the hydrologic cycle and its role in arctic and global

The Hydrologic Cycle and its Role in Arcticand Global Environmental Change:

A Rationale and Strategy for Synthesis Study

A Report from the Scientific Community to theNational Science Foundation Arctic System Science Program

NSF-ARCSS Hydrology Workshop Steering Committee

Charles Vörösmarty (University of New Hampshire)Larry Hinzman (University of Alaska Fairbanks)Bruce Peterson (Marine Biological Laboratory)David Bromwich (Ohio State University)Lawrence Hamilton (University of New Hampshire)James Morison (University of Washington)Vladimir Romanovsky (University of Alaska Fairbanks)Matthew Sturm (CRREL, Fort Wainwright, Alaska)Robert Webb (NOAA, Boulder, Colorado)

With contributions from scientists at the NSF-ARCSS Hydrology Workshop, Santa Barbara, CA, September 2000

2The Hydrologic Cycle and its Role in Arctic and Global Environmental Change

This report may be cited as:Vörösmarty, C. J., L. D. Hinzman, B. J. Peterson, D. H. Bromwich, L. C. Hamilton, J. Morison, V. E.

Romanovsky, M. Sturm, and R. S. Webb. 2001. The Hydrologic Cycle and its Role in Arctic and Global Envi-ronmental Change: A Rationale and Strategy for Synthesis Study. Fairbanks, Alaska: Arctic Research Consor-tium of the U.S., 84 pp.

Cover photo: Aerial view of Accomplishment Creek and the Sagavanirktok River in the Brooks Range of Alaska. Photo byD. L. Kane.

The workshop and this report were funded by the National Science Foundation under Grant OPP-9910264 andCooperative Agreement #0101279. Any opinions, findings, conclusions, or recommendations expressed in thispublication are those of the authors and do not necessarily reflect the views of the National ScienceFoundation.

3

Acknowledgements ................................................................................. 4

Executive Summary with Key Findings and Recommendations ............ 5Current State of the Art ........................................................................... 5Key Scientific Challenges and Recommendations ................................ 5Major New Synthesis Initiative Required .............................................. 6Implementation of Arctic-CHAMP ........................................................ 6Policy Implications ................................................................................. 7Summary .................................................................................................. 8

1. Introduction ........................................................................................ 9Rationale for Pan-Arctic Hydrologic Synthesis ..................................... 9Report Framework ................................................................................. 13

2. A Strategy for Detecting and Understanding ArcticHydrological Change: Arctic-CHAMP ............................................ 15Arctic-CHAMP Basic Long-Term Monitoring ...................................... 15Arctic-CHAMP Field-Based Process Studies ........................................ 18Arctic-CHAMP Synthesis Modeling ..................................................... 19Execution of Arctic-CHAMP ................................................................. 23

3. Role and Importance of Water in the Arctic System..................... 29The Integrated Water Cycle of the Pan-Arctic ...................................... 29Land ....................................................................................................... 29Atmosphere ............................................................................................ 31Ocean ..................................................................................................... 32Importance of Arctic Hydrology to the Arctic System ........................ 32Importance of the Arctic to the Earth System ..................................... 33

4. Unprecedented Change to Arctic Hydrological Systems ............. 35Changes to the Land-Based Hydrologic Cycle .................................... 35Changes to the Atmosphere ................................................................. 36The Changing Arctic Ocean and its Regional Seas .............................. 40

5. Impacts and Feedbacks Associated with ArcticHydrological Change ...................................................................... 43Direct Impacts on Ecosystems .............................................................. 43Arctic Water Cycle Change and Humans ............................................. 47Land-Atmosphere-Ocean Feedbacks .................................................... 48Land-Atmosphere-Ocean-Human Feedbacks ..................................... 49

6. Implementation of Arctic-CHAMP................................................... 53

References ............................................................................................ 61

Appendix 1. NSF-ARCSS Arctic Hydrology Workshop Participants ..... 71

Appendix 2. Current Gaps in Understanding thePan-Arctic Hydrological Cycle ........................................................ 75

Appendix 3. Integration of Arctic-CHAMP with NSFand Other Federal Agency Initiatives ............................................ 79

Appendix 4. International Collaborations .......................................... 83

Contents


Acknowledgements

The Hydrology Workshop Steering Committee wishes to express itsappreciation to those reviewers from the broader community and to thethirty-three scientists who met in a workshop at the National Center forEcological Analysis and Synthesis (NCEAS) in Santa Barbara, California,to discuss the gaps in our current understanding of arctic hydrology andto formulate a plan for future synthesis studies. Many scientists revieweda draft of this document and provided written comments, which greatlyimproved the final publication.

The Arctic Research Consortium of the United States (ARCUS), throughSue Mitchell, project manager, and Wendy Warnick, executive director,provided publication support, including layout design and development,preparation of graphics, technical editing, and coordination of the publi-cation process. Darlene Dube, administrative assistant at the Universityof New Hampshire (UNH), and Tamara Platt, administrative assistant atthe University of Alaska Fairbanks (UAF), provided much-needed andmuch-appreciated help throughout development of this document. Weare indebted to Jim Reichman and Marilyn Snowball and the staff ofNCEAS for providing a stimulating meeting place and essential work-shop support.

We are also grateful to the National Science Foundation Arctic SystemScience Program for supporting the workshop and the publication of thisdocument.

—Charles Vörösmarty and Larry Hinzman, co-chairsNSF-ARCSS Hydrology Workshop Steering Committee

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Executive Summarywith Key Findings and Recommendations

T he arctic system con-stitutes a unique and im-portant environmentwith a central role in the

dynamics and evolution of theearth system. The Arctic is inher-ently a highly dynamic system. Yetthere is mounting evidence that itis now experiencing an unprec-edented degree of environmentalchange. Many of these changes arelinked to the arctic hydrologiccycle and are quite possibly theresult of both the direct and indi-rect impacts of human activities.Despite the importance of this is-sue, the current state of the art can-not adequately establish these po-tential linkages to global change.Understanding the full dimensionof arctic change is a fundamentalchallenge to the science commu-nity over the coming decades andwill require a major new effort atinterdisciplinary synthesis. It alsorequires an unprecedented degreeof international cooperation.

Current State of the Art

The water cycle is an inseparableelement of the climate, biology,and biogeochemistry of the arcticregion. The sensitivity of arctic hy-drology to environmental changehas been demonstrated throughdozens of disciplinary studies fo-cused on individual elements ofthe water cycle such as precipita-

tion, evaporation, or runoff. Weknow much less about water-related teleconnections to regionaland global climate. The absence ofcross-disciplinary synthesis studiescontributes to our inability to for-mulate a clear and quantitativepicture of the integrated arctic sys-tem. In the face of global environ-mental change, the arctic sciencecommunity has made predictionsof system-wide impacts, but withlittle confidence.

These key, unresolved issues can becast as a set of scientific questions,fundamentally cross-disciplinaryand synthetic in nature:

• What are the major features (i.e.,stocks and fluxes) of the pan-arctic water balance and how dothey vary over time and space?

• How will the arctic hydrologiccycle respond to natural vari-ability and global change?

• What are the direct impacts ofarctic hydrology changes onnutrient biogeochemistry andecosystem structure and function?

• What are the hydrologic cyclefeedbacks to the oceans andatmosphere in the face of natu-ral variability and globalchange? How will these feed-backs influence human systems?

Key Scientific Challengesand Recommendations

How well are we poised to answersuch questions? A survey of thearctic science community—repre-sented by an interdisciplinaryworkshop convened by ARCSS inSeptember 2000 and summarizedin the remainder of this volume—revealed several notable gaps inour current level of understandingof arctic hydrological systems. Atthe same time, rapidly emergingdata sets, technologies, and model-ing resources provide us with anunprecedented opportunity tomove substantially forward. Threemajor research and synthesis chal-lenges with accompanying recom-mendations for strategic invest-ments in arctic system science aregiven below. Understanding, simu-lating, and predicting contempo-rary and future hydrological dy-namics is greatly limited by:

1.A sparse observational networkfor routine monitoring togetherwith the absence of integrateddata sets of spatial and tempo-rally harmonized biogeophysicalinformation over the pan-arcticdomain. The situation is farfrom optimal and deterioratingrapidly over much of thepan-arctic, especially in Russiaand Canada.

Executive Summary


Recommendations: A substantialcommitment should be made torescue, maintain, and expand cur-rent meteorological and hydrologi-cal data collection efforts. Estab-lishing high-resolution griddedmaps of climatic, hydrologic, topo-graphic, vegetation, and soil prop-erty attributes for the Arctic Oceanwatershed is strongly advised. Ad-ditional resources must be investedin scaling techniques, includingthe expanded use of remote sens-ing. Support for free and open ac-cess to arctic environmental datasets is essential to future progress.Coordination with existing U.S.and international monitoring pro-grams is critical.

2.Numerous gaps in our currentunderstanding of basic scientificprinciples and processes regardingthe water cycle over the entirepan-arctic domain.

Recommendations: Interdisciplinarysynthesis studies linking hydro-logic processes with other depen-dent biogeochemical and biogeo-physical processes should befostered to assemble a more com-plete understanding of the arcticsystem and its role in the broaderearth system. Investments in long-term, process-based hydrologicalfield studies are required.

3.The lack of cross-disciplinary syn-thesis research and modeling todecipher feedbacks arising fromarctic hydrological change on theearth system and on society.

Recommendations: Supportshould be given to integrativeresearch that identifies the uniquerole of arctic hydrosystems in thebroader earth system. An assess-

ment of the feedback mechanismsthrough which progressive hydro-logical change influences bothnatural and human systems isurgently needed. New researchdevoted to establishing quantita-tive linkages between the biogeo-physical and socioeconomicresearch communities is stronglyadvised.

Major New SynthesisInitiative Required

The gaps identified above demon-strate an urgent need to reformu-late the manner in which arctic hy-drological research is funded andexecuted. Implementation of therecommended actions will requirea dedicated research program tosupport arctic hydrological synthe-sis studies. Such a program doesnot now exist, yet has been calledfor as a component of the U.S.Global Change Research Program’sinitiative on the water cycle. Tosupport this new science, thecommittee’s central recommenda-tion is that:

• NSF-ARCSS invest in the devel-opment of a pan-Arctic Commu-nity-wide Hydrological Analysisand Monitoring Program (Arctic-CHAMP) to provide a frame-work for integration studies ofthe pan-arctic water cycle andto articulate the role of fresh-water in terrestrial ecosystem,biogeochemical, biogeophys-ical, ocean, climate, and humandynamics.

The primary aim of Arctic-CHAMPis to catalyze and coordinate inter-disciplinary research with the goalof constructing a holistic under-standing of arctic hydrology

through integration of routineobservations, process-based fieldstudies, and modeling. Four goalsshould guide this effort:

Goal 1: Assess and better under-stand the stocks and fluxeswhich constitute the arctic hy-drologic cycle.

Goal 2: Document changes to thearctic water cycle, contributing ahydrological component to themultiagency SEARCH Program.

Goal 3: Understand the causes ofarctic water cycle change andassess their direct impacts onbiological and biogeochemicalsystems.

Goal 4: Develop predictive simula-tions of the response of the earthsystem and human society tofeedbacks arising from progres-sive changes to arctic hydrologi-cal systems.

Implementation ofArctic-CHAMP

To execute this initiative, the com-mittee strongly recommends:• creating an Arctic-CHAMP Scien-

tific Steering Committee (AC-SSC)to formulate a detailed interdis-ciplinary implementation planand then supervise execution ofthe initiative

• supporting a multidisciplinaryset of process-based catchmentstudies

• initiating a major effort to im-prove our current monitoring ofwater cycle variables, coordinat-ing with U.S. and internationalagency partners as required

• establishing the Arctic-CHAMPSynthesis and Education Center

7

(CSEC) to serve as the physicallocation for several of the scien-tific activities of the program.The center should lead the coor-dination of modeling, field re-search, and monitoring effortswithin CHAMP.

• selecting a core group of Arctic-CHAMP researchers, chosenthrough peer review, to executeprocess studies, monitoring, andmodeling efforts. The researchteam would include principalinvestigators and their post-doc-toral fellows and graduate stu-dents, in residence at CSEC. Theteam would have representativesfrom the biogeophysical and so-cioeconomic realms and includeboth observationalists andmodelers.

• convening an Arctic-CHAMPWorkshop Series and Open Sci-ence Meetings to promote a con-tinuing involvement of the arcticand earth systems science com-munities

• fostering collaboration with themany relevant U.S. arcticresearch initiatives. This willhelp to ensure maximum syn-ergy across programs and avoidduplication of effort. The hydro-logic cycle studies of Arctic-CHAMP could serve as the NSF-ARCSS contribution to themultiagency SEARCH Program.They also will support NSFBiocomplexity and InformationTechnology programs as well aspublic outreach and educationefforts.

• creating and sustaining a vigor-ous set of international scienceand monitoring partnerships.

Most of the pan-arctic land massresides in Russia and Canada.No single National ScienceFoundation program, or even theU.S. arctic research communityas a whole, could achieve thedegree of synthesis required. TheNSF must forge strategic interna-tional partnerships to be success-ful in this endeavor.

Policy Implications

Scientists have yet to observe andunderstand the full dimension ofpan-arctic variability and progres-sive change, but at the same time,they are under increasing pressureto advise the policy-making com-munity as it struggles with howbest to manage the full dimensionof contemporary and future globalchange. The impact of arctic systemchange is likely to extend farbeyond the Arctic per se and thusbecome of critical concern to soci-ety at large. An investment inknowledge is of clear and immedi-ate necessity. The contributions ofan Arctic-CHAMP toward articulat-ing the diverse physical, biological,and human vulnerabilities to thischange provide an important im-petus for international cooperationin wisely managing this criticalpart of the earth system.

Executive Summary


Key Unresolved Scientific Questions

• What are the major features (i.e., stocks and fluxes) of the pan-arctic water balance and how do theyvary over time and space?

• How will the arctic hydrologic cycle respond to natural variability and global change?

• What are the direct impacts of arctic hydrology changes on nutrient biogeochemistry and ecosystemstructure and function?

• What are the hydrologic cycle feedbacks to the oceans and atmosphere in the face of natural variabil-ity and global change? How will these feedbacks influence human systems?

Recommendations• A substantial commitment should be made to rescue, maintain, and expand data collection efforts. Estab-

lishing high-resolution gridded maps of climatic, hydrologic, topographic, vegetation, and soil propertyattributes for the Arctic Ocean watershed is strongly advised. Additional resources must be invested inscaling techniques, including the expanded use of remote sensing.

• Interdisciplinary synthesis studies linking hydrologic processes with other dependent biogeochemical andbiogeophysical processes should be fostered. Investments in long-term, process-based hydrological fieldstudies are required.

• Support integrative research that identifies the unique role of arctic hydrosystems in the broader earthsystem.

• Develop a pan-Arctic Community-wide Hydrological Analysis and Monitoring Program (Arctic-CHAMP).

Arctic-CHAMP Implementation• Create an Arctic-CHAMP Scientific Steering Committee (AC-SSC) to formulate a detailed interdisciplinary

implementation plan and then supervise execution of the initiative.

• Support a multidisciplinary set of process-based catchment studies.

• Initiate a major effort to improve our current monitoring of water cycle variables, coordinating with U.S.and international agency partners as required.

• Establish the Arctic-CHAMP Synthesis and Education Center (CSEC) to serve as the physical location forseveral of the scientific activities of the program. The center should lead the coordination of modeling,field research, and monitoring efforts within CHAMP.

• Convene an Arctic-CHAMP Workshop Series and Open Science Meetings to promote a continuing involve-ment of the arctic and earth systems science communities.

• Foster collaboration with the many relevant U.S. arctic research initiatives. The hydrologic cycle studies ofArctic-CHAMP could serve as the NSF-ARCSS contribution to the multiagency SEARCH Program. Theyalso will support NSF Biocomplexity and Information Technology programs and public outreach andeducation efforts.

• Create and sustain a vigorous set of international science and monitoring partnerships. The NSF mustforge strategic international collaborations to achieve the degree of synthesis required.

9

derstand the rapidly changing stateof the Arctic and predict its futurecondition, we need to synthesizeexisting hydrologic knowledge andto identify gaps in that knowledge.It is critical to organize our currentunderstanding into a frameworkthat captures the essential work-ings and complexities of the arcticwater cycle, taken as a whole. Inthis way we can more effectivelyarticulate the Arctic’s unique placewithin the larger earth system andits role in global change, as calledfor in the recent U.S. GlobalChange Research Program watercycle initiative (USGCRP WaterCycle Study Group 2001).

An understanding of the contem-porary and potential future statesof the arctic hydrological system isa precursor to assessments of theassociated impact on natural eco-systems and human society. Suchassessments must rely on highquality, quantitative informationand are thus critical to sound poli-cies for environmental protection.

The Arctic Water Cycle asan Integrating FrameworkThe hydrologic cycle provides anideal framework for arctic systemsynthesis. First, the arctic hydro-logic system spans three realms:land, ocean, and atmosphere. Sec-ond, the water cycle is more thanjust a set of physical processes: itincludes living things—plant,animal, and human—and they all

Introduction• Assess the state of the art in arctic

systems hydrology and identifyresearch priorities for achievingpredictive understanding of therole of the arctic water cycle inglobal change.

The meeting had broad representa-tion from within the arctic researchcommunity, with more than 30members having expertise in landsurface hydrology, terrestrial andfreshwater ecology, atmosphericdynamics, ocean processes, simula-tion modeling and geo-spatialanalysis (Appendix 1). A steeringcommittee attempted to captureconsensus views articulated duringthe meeting and represented bythis current document. Majorthrusts of the workshop were toarticulate the need for interdiscipli-nary arctic hydrologic studies andto formulate a strategy for newsynthesis research.

Rationale for Pan-ArcticHydrologic Synthesis

The pan-arctic hydrological systemis complex and currently undergo-ing a period of rapid change thatwill influence all aspects of life inthe Arctic. The changes will alsointeract in important ways with theglobal system. In the followingchapters, we document thesechanges and show the complexlinkages within the arctic hydro-logic system and between the arcticand global systems. If we are to un-

T he water cycle of theArctic plays a centralrole in regulating boththe planetary heat bal-

ance and circulation of the globaloceans. Recent and unprecedentedenvironmental changes, such asdeclines in the total area of wintersnow cover on land and decliningsea ice cover throughout the ArcticOcean, are now well documented.Unfortunately, the causes of thesechanges and their impact on theglobal ocean and atmosphere arestill poorly understood. The cycleof freshwater in the arctic land-atmosphere-ocean system is centralto these observed changes (Figure1-1). Yet, knowledge of the hydrol-ogy of the arctic region remainsincomplete due to the complexitiesof permafrost terrain, difficulties inacquiring data in harsh environ-ments, decline in routine monitor-ing, and a lack of interdisciplinaryresearch. Progress in predictingglobal change can only be achievedthrough development of a newmore synthetic and systematic un-derstanding of the water cycle ofthe Arctic.

In September of 2000, a workshopsupported by the National ScienceFoundation Arctic System Science(ARCSS) Program was convened atthe National Center for EcologicalAnalysis and Synthesis in SantaBarbara, California. The work-shop’s central goal was to:

1

1. Introduction


Figure 1-2. Multiscale approach toward achieving synthesis of pan-arctic hydro-logical dynamics and identifying its role in the larger earth system. Informationfrom all scales is necessary to ensure mutual consistency of predictive models.Biophysical, biogeochemical, and human dimension issues should be simulta-neously addressed. (Precipitation over the land area that drains into the ArcticOcean is shown in the lower left panel.)

Local Basin/Region

Figure 1-1. Conceptual diagram of the arctic system, showing linkages amongthe atmosphere, land surface, and ocean systems. Links within the arctic regionas well as the larger earth system must be considered to achieve an integratedview of the hydrological cycle (from Walsh et al. 2001).

Sea Surge,Sea Level

Sea Surge,Sea Level

Freshwaterand

Constituents

Freshwaterand

Constituents

Water,Energy,TraceGases

Wat

er, E

nerg

y,Tr

ace

Gas

es

Wat

er, E

nerg

y

ICE SHEETS(Land Based)

TERRESTRIAL SYSTEMS(Biogeochemistry,

Vegetation Dynamics,Hydrology)

ATMOSPHERE(Climate)

SEA ICEOCEANS

Pan-Arctic Global

interact. Third, the hydrologic cycleis a complex system that cannot beunderstood or predicted fromstudy of its individual parts alone(Woo 1986). This complexity ex-ists over the pan-arctic scale downto the smallest river basin or re-search plot.

The arctic domain may be one ofthe best places to explore the inter-action of land, atmosphere, andoceans through the unique rolethat water plays in linking theserealms (Figures 1-1 and 1-2). It isthe most “closed” and land-domi-nated of all the major ocean basins(Vörösmarty et al. 2000). The Arc-tic Ocean’s connection to globalocean circulation is through tworelatively well-defined exchangesthrough the Bering Strait and Nor-dic Sea. Sea ice generated in theArctic Ocean can be tracked on itsway southward to the Atlantic. At-mospheric exchange is bounded bythe fairly well-identified PolarFront. The domain is relativelypristine, and thus an excellentlaboratory for isolating the effectsof natural variability versus the di-rect impacts of human activity.

Current Arctic WaterCycle ResearchAlthough there is a widespread rec-ognition that arctic hydrology issensitive to global change, anunderstanding of the basic mecha-nisms that control terrestrial watercycling constitutes a major researchneed. Recent ARCSS activities haveclearly identified the importanceof the terrestrial water cycle, re-flected most notably in the LAIIPlan for Action (1997), Modeling theArctic System (1997), Toward anArctic System Synthesis (1998), andToward Prediction of the Arctic Sys-

11

tem (1998) workshop reports andsteering documents. Many of theoverview diagrams in these publi-cations show elements of the ter-restrial water cycle figuring promi-nently in virtually all arctic systemdynamics. Although these reportsrecognize a key role for water inthe arctic system, there remains acompelling need for a coherentframework through which to studyarctic hydrology per se.

A proliferation of traditional disci-plinary research has been success-ful in producing a wealth ofknowledge about individual com-ponents of the hydrologic system(Brown 1968, Dingman 1973,Dingman et al. 1980). However,this body of work does not yet per-mit these pieces to be forged into acomprehensive understanding ofthe whole. Work funded by NSFand other agencies has typicallybeen separated by discipline—hydrology, atmosphere and oceandynamics, biogeochemistry, andecology—and collaborationbetween the disciplines has beenlimited. Essential hydrologic pro-cesses regulating terrestrial ecosys-tem dynamics, for example, haveoften been addressed through in-dependent hydrologic studies andhave not taken advantage of thesynergy possible by the sharing ofresearch sites and experimentaldesign. But the interfaces betweenthese disciplines are likely to bethe very areas where the mostexciting and valuable new researchwill take place. Disciplinary barri-ers need to come down.

The Need for SynthesisIn developing an integrated pictureof arctic hydrology, the scientificcommunity has at its disposal a

broad disciplinary literature thatcan provide a quantitative sum-mary of the pools of water andenergy found in the atmosphere,soil, rivers, lakes, glaciers, sea ice,and ocean waters of the Arctic (Fig-ure 1-3). Estimates of the energyand water transport into and outof the Arctic are also becomingavailable. While providing a usefulbackdrop, collectively these studiesare hardly comprehensive and dif-ficult to interpret from a systemsviewpoint. Because of its integrat-ing role, the arctic water cyclerequires an understanding of theprocesses controlling these poolsand transports. An integrated sci-entific program based on long-term monitoring, field studies, andsimulation could provide animportant path forward. We wouldbe in a much improved position toassess and interpret historic trendsand to make predictions of thefuture.

Development of a synthetic under-standing of the arctic hydrologiccycle will thus require closer col-laboration between modelers andobservationalists. Field measure-ments and process studies providethe data and physical insights forarctic water cycling that underpinmodeling efforts. Models, in turn,provide predictive capability, thecritical ability to extrapolate intime and space needed to addressthe impact of hydrologic change.Models have not yet been ad-equately exploited in designingoptimal arctic monitoring pro-grams, identifying regions wherethe density and distribution ofcritical measurements need to beupgraded, or singling out signifi-cant gaps in our understanding ofthe hydrologic processes. A multi-

disciplinary approach can yieldimportant new insights (Figure1-4). Communication and closecollaboration between these groupsis essential.

NSF-ARCSS Hydrology Workshopparticipants proposed a major sci-entific challenge:• Can we successfully construct a

quantitative and coherent pictureof the arctic water cycle and itslinks to the earth system based onthe current state of knowledge,infrastructure, and institutionalsupport, including all relevantARCSS and non-NSF researchprograms?

A consensus indicated that the an-swer is no. Three major obstacleshave hindered progress:1.A sparse observational network

for routine monitoring togetherwith the absence of integrateddata sets of spatial and tempo-rally harmonized biogeophysicalinformation over the pan-arcticdomain.

2.Numerous gaps in our currentunderstanding of basic scientificprinciples and processes regardingwater cycling in arctic environ-ments.

3.The lack of cross-disciplinary syn-thesis research and modeling todecipher feedbacks on the earthsystem and on society arisingfrom arctic hydrological change.

To address these challenges, theworkshop participants recom-mended development of a pan-Arctic Community-wide Hydro-logical Analysis and MonitoringProgram (Arctic-CHAMP) thatfocuses on arctic water and energycycles. Arctic-CHAMP is planned asa research program with routine

1. Introduction


Figure 1-3. Conceptual model of the arctic hydrological cycle, with key linkages among land, ocean, and atmosphere. Thecoupling of these components within the Arctic and to the larger earth system remains an important yet unresolvedresearch issue. The hydrological cycle is inextricably connected to all biological and chemical processes occurring in thebiosphere, atmosphere, and cryosphere. Hydrologic interactions with terrestrial and aquatic ecosystems and their bio-geochemistry control all life in arctic regions.

J

GG

HHH

I

BBBA

DDDDD

A = atmospheric boundary fluxesB = atmospheric dynamicsC = land-surface atmosphere exchanges (with

vegetation and permafrost dynamics)D = discharge through well-defined flow networks (with

groundwater and river corridor flow)E = runoff from poorly organized lowland flow systems

F = sea ice mass balance and dynamicsG = estuarine controls on terrestrial/shelf interactionsH= changes in glacial mass balance and associated runoffI = direct groundwater discharge to oceanJ = Arctic Ocean dynamics and deep water formationK = biological dynamics and oceanic food chains

13

Figure 1-4. Progressive change in alkalinity of Toolik Lake, Alaska, from long-term, synergistic hydrology and hydrochemical measurements. Chemicalchanges may signal the warming of permafrost in response to global climatechange (Neil Bettez, Arctic LTER database).

0.3

0.4

0.5

0.6

0.7

1975 1979 19851983 1987 1989 1991 1993 1995 1997 1999

Alk

alin

ity

(mill

ieq

uiv

ale

nts

)

1977

observations, focused on process-based field studies, and pan-arcticsynthesis. The workshop partici-pants went on to develop a con-ceptual framework for Arctic-CHAMP and to define its rolewithin NSF-ARCSS.

Report Framework

In the chapters that follow weexplain the scientific reasoning forArctic-CHAMP together with sev-eral practical aspects surroundingits implementation. We begin witha chapter describing the concep-tual design of the Arctic-CHAMP.This chapter is followed by a sum-mary of our current state of knowl-

edge regarding the arctic watercycle and its role in climate, land,and ocean system dynamics. Wethen show evidence for changes tothe arctic water cycle. A chapter isthen presented which is organizedas a brief assessment of our currentunderstanding of the sensitivity ofarctic hydrology to global changeand of the potential feedbacks tothe larger pan-arctic and earth sys-tems. We close with an initial setof recommendations for imple-mentation of Arctic-CHAMP, high-lighting opportunities for collabo-rative work with other U.S. andinternational agency partnersacross the Arctic.

1. Introduction

15

A Strategy for Detecting andUnderstanding Arctic Hydrological

Change: Arctic-CHAMPFigures 2-1 and 2-2. It consists ofthree basic, interacting components:1.compilation and evaluation of

monitoring data on the hydro-logic cycle,

2.field observations and focusedprocess studies, and

3.simulation models operatingover local to regional to pan-arctic domains.

We will focus on the individualcontributions of these primary sci-entific elements but also discusshow they should be integrated formaximum benefit. The executionof Arctic-CHAMP, which requires a

consideration of its organizationalstructure, specific program activi-ties, and links to ongoing NSF,U.S., and international researchprograms, is detailed in Chapter 6.

Arctic-CHAMP BasicLong-Term Monitoring

We recommend that steps be takenimmediately to reconstitute, sus-tain, and improve upon the basichydrologic monitoring systems ofthe Arctic. The long-term observa-tions necessary to understand theconsequences of global change onthe hydrosphere are currently

W e recommenddevelopment ofa pan-ArcticCommunity-wide

Hydrological Analysis and Moni-toring Program (Arctic-CHAMP) toprovide the structure and frame-work for synthesis studies of thepan-arctic water cycle. Arctic-CHAMP would provide a focalpoint for cross-disciplinaryresearch that focuses on the link-ages between land, atmosphere,ocean, and biota.

The overall structure of Arctic-CHAMP is shown conceptually in

Figure 2-1. Overall framework of the Arctic Community-Wide Hydrological Analysis and Monitoring Program (Arctic-CHAMP). The science and technical goals of the project are considered in Chapter 2. Execution of the program isdescribed in Chapter 6.

SCIENCE AND OBSERVATIONALCOMPONENTS EXECUTION

Arctic-CHAMPSynthesisModeling

Long-TermMonitoring

Process-BasedField

Studies

• Arctic-CHAMP Synthesis and Education Center• Arctic-CHAMP Steering Committee• Interdisciplinary Implementation Plan• Funded Science Projects• Workshop Series and Open Science Meetings• Integration with Other U.S. and International Arctic Research Programs

2

2. A Strategy for Detecting and Understanding Arctic Hydrological Change


unavailable. The Arctic is where wewill best be able to measure theearly signs of global change. A sus-tained commitment of resourceswill be necessary to develop theinfrastructure necessary to capital-ize on this unique scientificopportunity.

The value of documenting long-term changes in arctic temperature,precipitation, snow cover, sea ice,and storms has been demonstrated(Serreze et al. 2000). These pro-gressive changes are occurringacross the very region where gen-eral circulation models (GCMs)have predicted the earliest andlargest greenhouse warming(Houghton et al. 1996, 2001) andwhere observed changes are consis-tent with predicted trends. Unfor-tunately, at precisely the time weneed these records most, the qual-ity and extent of arctic monitoringnetworks have diminished sub-stantially (IAHS Ad Hoc Group onGlobal Water Data Sets 2001;

Shiklomanov et al. in review) (Box2-1).

The existing network of hydro-meteorological stations devoted tolong-term monitoring needs to beaggressively reconstructed andoptimized in order to detect andaccurately track the unique signa-ture of global change on the Arctic.Consideration needs to be given todeploying instruments for observ-ing the system as a whole. This is afundamental goal of the new inter-agency Study of Environmental Arc-tic Change (SEARCH) Program(SEARCH SSC 2001), which goeswell beyond hydrology per se. Tosupport continued availability ofhydrologically relevant monitoringdata, we recommend the followingsteps, all of which require a com-mitment to free and open data ex-change (Box 2-2):

1.Rescue Data: Critical data frompast monitoring and measure-ment programs needs to be iden-

tified, recovered, and made avail-able. Support for translation,documentation, accuracy check-ing, and conversion of paperarchives to electronic media isneeded. In vast areas of Eurasia,monitoring networks continueto deteriorate and every effortshould be made to rescue criticaldata from these stations. Someof this effort (Holmes et al.2000, Lammers et al. 2001; cf.National Snow and Ice DataCenter) is underway, but muchmore needs to be done.

2.Sustain/Augment ObservationalNetworks: Ground-based arctichydrological and meteorologicalsites where long-term observa-tions are most valuable need tobe identified and steps taken toensure that measurements willbe continued at these sites.Threatened sites can be foundnot only in Eurasia but in NorthAmerica as well. For example,atmospheric moisture fluxesdetermined from numericalweather prediction modelreanalyses ultimately depend onthe routine rawinsonde networkwhich has been in decline sincethe early 1990s.

3.Improve Autonomous Instrumen-tation: Because much of the Arc-tic is remote and uninhabited,there is a pressing need for betterand more reliable autonomousinstrumentation for collectinghydrological and meteorologicalparameters. Critical improve-ments are needed in communi-cations, power, and in the mea-surement of precipitation,notorious for gauge-related bias.

Figure 2-2. Overall conceptual framework of the pan-Arctic Community-wideHydrological Analysis and Monitoring Program (Arctic-CHAMP).

Inte

gratio

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er Earth

System

Atm

osph

ere

• process understanding• scaling up

• scaling down• model testing• observation network design

Oce

an

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Arctic-CHAMP

diagnostic prognosticObservations Models

new ideas, new components

17

Box 2-1. The Deterioration of Arctic HydrographicMonitoring Networks

Despite sensitivity of the pan-arctic region toglobal change and mounting evidence of itsresponse expressed through the arctic watercycle, we see an increasing number of obstaclesto the timely and broad distribution of in situmonitoring data. Precipitation data are threat-ened for several reasons. In spite of the universalimportance and high value of accurate measure-ments of rain and snowfall, the number of mea-surement stations continues to decrease. Thedata that does exist is not always usable due togauge undercatch that occurs (particularly forsnow) in windy areas (Benson 1982, Goodisonet al. 1998, Yang et al. 2000).

The situation has been particularly trouble-some with respect to discharge data, which areviewed as a strategic information resource sub-ject to formal and informal data policy restric-tions and commercialized for cost-recovery (Na-tional Research Council 1999, IAHS Ad HocCommittee on Global Data Sets 2001). Time se-ries of available pan-arctic discharge monitoringstation data sets is shown below (Lammers et al.2001), and the problem is obvious. In the Rus-sian Arctic, we have seen a 30% decline in opera-tional capacity since 1990. Delays in data reduc-tion and release, in many countries amountingto several years, greatly exacerbate the problem.Large quantities of otherwise reliable data existin difficult-to-use paper formats, warehoused for

0

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years and in grave risk of damage. Canada hasseen a 20% reduction in the number of dis-charge stations since 1990, many in the Arctic(B. Goodison, Environment Canada, DownsviewONT, personal communication, 2000). InCanada there has been a push to establish in-strumented monitoring stations that are un-tended during the winter. Much data such assnow depths are now not collected and otherdata are compromised by instrument failure dur-ing winter. The U.S. also has lost river stationtime series, including the vital lowermost stationon the Yukon River, which fortunately has justbeen reopened. Accurate water chemistry dataover the pan-arctic are even more fragmentary(Holmes et al. 2000).

The situation is in stark contrast to the real-time availability of meteorological andoceanological data for weather forecasting. Themismatch between river discharge and meteoro-logical data availability interferes with the timelyidentification and interpretation of a changinghydrology of the pan-arctic. A good example isthe most recent estimate of present-day freshwa-ter inflow to the Arctic Ocean, based on six-year-old observations (I. Shiklomanov et al. 2000). Atemporally harmonized data set for pan-arctichydrology and meteorology will be essential tothe future monitoring of global change in theregion.

Time series of station holdings from a pan-arctic hydrographic archive (R-ArcticNet)(Lammers et al. 2001) and an opera-tional data bank (Arctic-RIMS). Bothnet declines in operating stations (lines)and multiyear delays in data access (un-shaded area) are apparent in the panelon the left. Arctic-RIMS represents aconcerted effort to obtain timely hydro-graphic records for a set of key stations(from Shiklomanov et al. in review).



Arctic-CHAMP Field-BasedProcess Studies

We recommend that a commit-ment be made toward establishinga core set of pan-arctic watershedstudy sites where a tightly inte-grated set of process-based mea-surements and monitoring can besystematically carried out over along time frame. An interdiscipli-nary perspective is central to thesuccess of these field studies.

There is a conspicuous lack of fullycoordinated studies of hydrologi-cal processes in the Arctic. De-cades-long watershed studies likeCoweeta, Hubbard Brook, andH. J. Andrews have made majorcontributions toward our process-based understanding of temperateecosystems and provide essentialcalibration and validation data to awide spectrum of hydrological andhydrological-biogeochemical mod-els. From these sites has emergedcritical information on water cycledynamics, for instance, how pre-cipitation and evapotranspirationinteract to regulate runoff through-out the year. Comparable facilitiesdedicated to integrated analyses ofarctic hydrological processes mustbe established.

To fill current gaps in our process-based knowledge and to improveour capacity to simulate and pre-dict arctic hydrologic and ecosys-tem change, research at these siteswould comprise:• experiments to uncover hydro-

logic mechanisms through theconjunction of fieldwork andmodeling;

• measurements allowing com-parative analyses with otherwatersheds; and

Box 2-2. Open Data Policy

The success of CHAMP will depend heavily on a policy of free andunrestricted data exchange. In light of the continued loss of hy-drometeorological monitoring capacity (Box 2-1) this continues tobe of critical importance. The arctic scientific community has onlyrecently compiled an adequate historical archive of data sets thatcan be combined to detect systematic changes to the arctic system.When this has been done for the issue of change detection (Serrezeet al. 2000), it has provided compelling evidence of major warm-ing trends, atmospheric circulation changes, and a host of associ-ated impacts. The NSF Arctic System Science Program has alreadyinvested heavily in community-wide databases by supporting theNational Snow and Ice Data Center in Boulder, Colorado.

An Arctic-CHAMP Hydrometeorological Data Archive (HDA),representing an integrated community data resource, should becreated as part of the overall CHAMP effort. HDA should serve as arepository not only for station-based measurements (such as met-eorological and hydrological data) but also for second-generationdata (gridded interpolations of point measurements and thematicinterpretations of spatially distributed data sets) and model inputand output files (such as associated with GCMs or regional cli-matic models). Each of these data sets should be organized in stan-dard formatting, distributed through the Internet, and accompa-nied by appropriate metadata to explain the methodology used tocreate each data product.

Contributions of data to the archive should be an obligation ofevery scientist who receives funding under NSF ARCSS programs,and in particular Arctic-CHAMP. Charging a fee to use data or lim-iting access to that data places obstacles in the path of rapid scien-tific advancement (IAHS Ad Hoc Group on Global Water Data Sets2001, Kanciruk 1997). Data should be freely distributed to anyoneupon request. However, in keeping with the long-standing tradi-tion in the NSF-funded geosciences, an exclusive right to data pro-viders to first complete their analyses and publish those data asappropriate should be granted before release to the generalcommunity.

• research to improve the transfer-ability of site-specific processstudies and measurements tounmonitored sites, larger drain-age basins, and the entire pan-arctic.

The coordinated set of activitieswould constitute hydrological aswell as biogeochemical and bio-logical measurements, includingseldom-made winter observations(Table 2-1). Since permafrost is thesingle most dominant control onarctic terrestrial hydrological pro-

19

cesses, it is important that the sitesspan a latitudinal gradient extend-ing southward from the ArcticOcean into the region of discon-tinuous permafrost. The sites mustalso encompass both tundra andboreal forest biomes because thereis evidence that these ecosystemsare changing rapidly and that thechange is intimately linked to hy-drology. As shrub invades tundra,or spruce follows shrubs, a varietyof hydrologic consequences andfeedbacks are operating, all ofwhich impact humans and poten-tially the global system.

We recommend that a joint NSFworking group consisting ofresearchers from LAII, OAII,HARC, PARCS, SIMS, and LTER beconvened to study the costs andbenefits of establishing and main-taining an integrated set of well-instrumented small arcticcatchments. The group should ad-vise on an optimal set of measure-ments that would support processunderstanding, process modeling,and pan-Arctic extrapolation, aswell as on-site location to encom-pass the full range of landscapestypical of the pan-arctic land mass.The group should include observa-tionalists, modelers, and research-ers from Canada, Scandinavia, andRussia and international scientificprograms so that the choice of sitesaugments existing networks and isof greatest value to modeling.

Arctic-CHAMPSynthesis Modeling

We recommend that an Arctic-CHAMP Integrated System Model(ARC-ISM) be developed. Oneway to promote synthesis in arc-tic hydrology is to integrate exist-

ing models and develop a simula-tion system that can provide aformal mechanism for mass andenergy balance accounting, pro-cess-level testing, hypothesis gen-eration, and pan-arctic applica-tion. ARC-ISM is intended toprovide such a mechanism. Italso provides a framework forintegrating the long-term moni-toring and process-based experi-mental elements of Arctic-CHAMP.

ARC-ISM (Figure 2-3) is an earthsystem model focused on the Arc-tic. It should treat in an integratedfashion the Arctic’s climate, land

surface hydrology, ocean, vegeta-tion, biogeochemical, and humansystems. Equally as important, itmust be able to quantitativelyarticulate the pan-arctic’s connec-tion to the larger earth system,which will be critical for analyzingfeedbacks in response to globalchange. Retrospective, contempo-rary, and future time frames needto be analyzed, with ARC-ISM castas a diagnostic as well as prognosticmodeling tool. ARC-ISM shouldbe considered to be a numericalmodeling framework serving as aflux coupler to which variouscomponent models (land, ocean,

Table 2-1. Examples of the coordinated set of measurements that mightbe made at an Arctic-CHAMP study site. Efforts should be made toexpand the number of sites and the number of variables routinelyobserved.

Hydrological and Other Geophysical Measurements• Precipitation Amount (Year Round)• Evapotranspiration and Sublimation• Solar Flux and Surface Energy Measurements• Snow Pack• Snow Redistribution• Snow Melt• Soil Thermal Properties and Their Variation

- Temperature Profiles- Active Layer Depth- Permafrost Temperature- Thermal Conductivity

• Infiltration on Frozen and Unfrozen Soils• Soil Moisture• Runoff Flow Paths• Stream and Large River Discharge• High-Resolution and Accurate Digital Elevation Models

Biological and Biogeochemical Measurements• Precipitation Chemistry• Vegetation Surveys• Soil Mapping• Monitoring of Vegetation, Soil, and Groundwater Chemistry• Stream and River Constituent Concentration• Aquatic Ecosystem Surveys• Isotope and Other Tracers for Discharge Entering Arctic Ocean



Figure 2-3. Major features of the Arctic-CHAMP Integrated System Model (ARC-ISM) showing (top) the overall con-ceptual domains of the model and (bottom) the land surface hydrological component in more detail. The land includesvegetation, soils, river corridors, wetlands, and aquatic ecosystems. Carbon, nutrient, and other constituent fluxes will bemodeled in tandem with the simulated water cycle dynamics.

diagnostic

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21

atmosphere) could be attached.This would allow for the necessaryflexibility to make the overallmodeling scheme accessible to thebroadest user community. Successwill require strict adherence torules governing module couplingand documentation.

ARC-ISM in diagnostic modeshould be used to analyze retro-spective and near-real time watercycle dynamics, drawing on experi-ence and techniques developedthrough state-of-the-art atmo-spheric modeling. These modelsinclude the current generation ofGeneral Circulation Models(GCMs) and Regional ClimateModels (RCMs). “Reanalysis”efforts by the National Centers forEnvironmental Prediction (NCEP)and the European Centre forMedium-Range Weather Forecasts(ECMWF) constitute a promisingmethod for obtaining relevantfields for the pan-Arctic. Atmo-spheric transports of water vaporprovide the fastest and most directlink between the pan-arctic andglobal climates and are thereforeof great value in articulating thecoupling of the Arctic to the earthsystem. Such models provide uswith the necessary tools for analyz-ing this linkage and for quantita-tively assessing changes to the pan-arctic water budget. An emphasison improving the accuracy of suchmodels is clearly warranted (e.g.,Gutowski et al. 1997). Data assimi-lation for all key variables of thehydrologic cycle should also befostered explicitly.

The diagnostic ARC-ISM can alsooffer an important resource in thedesign of optimal monitoring net-works for hydrological variables.

Precipitation, for example, remainsone of the most crucial but diffi-cult-to-estimate hydrologic mea-surements. Precipitation fields canbe obtained through spatial inter-polation techniques that producehigh-resolution gridded data sets(e.g., Willmott and Rawlins 1999,Willmott and Matsuura 1995,Hutchinson 1998) based on sta-tion data, topography and/or exist-ing climate information. The tech-niques are sensitive to stationdensity, which is in decline overmuch of the Arctic. The diagnosticversion of ARC-ISM could be usedin numerical experiments to iden-tify critical stations requiring for-mal protection and to formulatean optimal deployment strategyfor new sites. Identification of theappropriate level of spatial andtemporal detail necessary to cap-ture the salient features of hydro-logical processes—working fromthe intensive field site models upto the domain of the pan-arctic—would be a major activity of theARC-ISM modeling group.

An important opportunity presentsitself to the arctic research commu-nity through a rapidly emergingsuite of remote sensing data re-sources provided by U.S. and inter-national space agencies. Given itspan-Arctic perspective, ARC-ISMcould provide an important test-bed for satellite sensors specificallytargeted at the hydrology of high-latitude landscapes. Its initial usecould be in testing data sets in ex-isting remote sensing repositories(Alaska SAR Facility [http://www.asf.alaska edu], NationalSnow and Ice Data Center [http://nsidc.org]), which have not yetbeen adequately exploited for hy-drological studies (Walsh et al.

2001). One particularly importantdata set for high-latitude runoffsimulation would be an accurateand high-resolution digital eleva-tion model (DEM), which has yetto be collected for the pan-Arcticdespite major investments to ob-tain this information for otherparts of the world (i.e., recentNASA Shuttle Radar TopographyMission). Space-borne sensors thatshow promise in delineating criti-cal seasonal transitions in thearctic hydrologic cycle (McDonaldet al. 1999, Running et al. 1999,Frolking et al. 1999, Kimball et al.2001) could be investigated andrigorously tested in the context ofARC-ISM. It could also be used tocreate specific new sensor sciencerequirements that could be actedupon in the design phase of thesesensors (Cline et al. 1999).

ARC-ISM should also be config-ured to run in prognostic modeover the pan-Arctic. Current arcticregional climate models incorpo-rate several interacting compo-nents of the hydrologic system, in-cluding atmosphere, ocean, landsurface, and biosphere (e.g., Lynchet al. 2001, Wei et al. in review).These regional climate models op-erate at much higher spatial resolu-tions than global climate models,but their boundaries are providedby the coarse-scale GCMs intowhich they are nested. Such mod-els may eventually provide detailedspatial descriptions of climatechange scenarios. The modelscould thus be used to gauge theimpacts of greenhouse warming onplant community structure or al-tered runoff generation and riverdischarge to the Arctic Ocean.Some specific applications of theARC-ISM integrated modeling



Box 2-3. Arctic-CHAMP Framework Application:Atmosphere/Land Surface Hydrology Reanalysis

As the sophistication of atmospheric modelinghas increased, it is now possible to begin quanti-fying a wide array of hydrologically relevantcomponents of the overall climate system—forexample, the troposphere, land surface, ocean,and stratosphere. New techniques for assimilat-ing meteorological observations directly intoNumerical Weather Prediction (NWP) modelsfosters the improvement of operational productsas well as the reanalysis of long time series ofhistorical archive data. These are important datasets because they provide us with the raw mate-rial for analyzing quasi-periodic phenomenasuch as ENSO, AO, and NAO. Working with U.S.(NCEP) and European (ECMWF) meteorologicalservices, ARC-ISM researchers would be well po-sitioned to develop an optimal land surfacemodel for Arctic NWP. Improved representationsof specific processes would include runoff gen-eration at the surface and at depth, storage in

QaQb

P E

∂Wa ∂t

Xg

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ROg

∂Wg ∂tGa

Gb

∂Wr ∂tDa

Xs

Db

the soil in liquid and solid forms, surface subli-mation or evapotranspiration, surface storage inthe form of snow, river routing, etc. When com-bined with atmospheric and oceanic modelsthat contain an optimal representation of arcticphysical processes (e.g., sea ice, arctic stratus,arctic haze, etc.), a reanalysis designed specifi-cally for arctic hydrology could be realized. Hy-drologic predictions constrained by all availableobservations would be obtained with high timeresolution for a period of many years using anappropriate data assimilation scheme. Such aproject would have to be a combined effort ofthe arctic hydrology community and experts inNWP. Improved reanalysis parameterizationshave a major additional benefit: the enhance-ment of near-real-time, operational weatherforecasts for the pan-arctic using versions of thesame NWP models. An application of the equa-tions shown here can be found in Box 2-4.

Wa = precipitable water (vertically integrated) Xs = excess water to river/surface pools

∇Q = horizontal water vapor flux divergence Wg = groundwater storage

E = evaporation + transpiration ∇G = horizontal groundwater flux divergence

P = precipitation ROg = runoff from groundwater

Ws = snowpack/soil water storage Wr = river water storage

Xg = excess water to groundwater pool ∇D = horizontal discharge divergence

t = time

AtmosphereObservations ProcessesWater Vapor Cloud Micro PhysicsAerosol Profiles Boundary Layer ProcessesWind Profiles Moisture ConvergenceTemperature Profiles Modulation/InfluenceCloud Cover by AO, NAO, ENSO, PNAPrecipitationEvaporation

LandObservations ProcessesPrecipitation InfiltrationEvaporation Snow MeltSnow Cover FreezeSoil Moisture ThawPermafrost ThermokarstingDischarge Runoff (X

s + RO

g)

∂Wa = –∇Q + E – P ∂t

∂Ws = P – E – Xg – Xs ∂t

∂Wg = –∇G + X – ROg ∂t

∂Wr = –∇D + ROg + Xs ∂t

GroundWater

River

Snowpack& Soil

Atmosphere

→

→

→

→

→

→

23

framework are given in Boxes 2-3through 2-8.

Execution of Arctic-CHAMP

While each element of Arctic-CHAMP is important in its ownright, we believe their integrationwill be the key to significant andrapid progress. To that end, Arctic-CHAMP has been structured toprovide facilities and synthesissupport activities linking the threecomponents of the initiative—monitoring, process studies, andsynthesis modeling. To afford pan-arctic integration, a multiscale ap-proach will be fundamental,incorporating under a singleframework broad-scale monitoringnetwork data sets, site-specific hy-drologic research, and simulation.

Successful synthesis will not be au-tomatic, and the otherwise inde-pendent monitoring, field experi-mentation, and simulationcomponents of Arctic-CHAMP willrequire a continual and concertedeffort at integration. The manage-ment of the program will thus be akey to its success. The overall pro-gram goals can be achieved by in-corporating guidance from a steer-ing committee, providing supportto targeted science and technologyprojects, entraining promisingyoung investigators, funding ex-panded monitoring, coordinatingwith existing arctic research pro-grams, and making a strategic in-vestment in science infrastructure.These programmatic elements aredetailed in Chapter 6.

Box 2-4. Arctic-CHAMP FrameworkApplication: Diagnosing thePerformance of Model Outputs

Computed evapotranspiration from the combination of aerological bud-gets from NWP reanalysis and an independent precipitation data set(Willmott and Matsuura 2000). Note the negative values, incongruentwith our current understanding of system dynamics. The framework forcombining such data sets is at the heart of the ARC-ISM algorithm andArctic-CHAMP more generally.

In its diagnostic mode, Arctic-CHAMP should be designed to maxi-mize our ability to judge the consistency among individual datasets, both against themselves and observational archives. Thus,Arctic-CHAMP would be a test bed for intercomparison studies us-ing equations of the form shown in Box 2-3. An example would betesting for disparities among several existing precipitation datasets and the translation of these discrepancies into runoff uncer-tainty. In another example, preliminary assessment by M. Serreze(University of Colorado, Boulder, unpublished data) demonstratesthat when NCEP atmospheric divergence fields and station-based,interpolated precipitation fields are blended to generate estimatesof spatially varying evapotranspiration, these estimates give whollyunrealistic, large negative evapotranspiration values (see Figure).Ongoing work demonstrates that fields can be somewhat improvedby accounting for gauge undercatch of solid precipitation (Serrezeet al. in review). Such sensitivity tests allow the community tojudge the degree to which observations of individual water cycleelements contribute uncertainty to the overall water budget closureacross the pan-Arctic. Identification of such “weak links” is a nec-essary step in identifying fertile areas for future research.



Box 2-5. Arctic-CHAMP Framework Application:Design of Optimal Monitoring Networks

Potential bias in river basin precipitation as inferred from closure experiments on global water budgets. Formuch of the arctic drainage basin there are strong negative biases (blue color), which are likely associated withunderestimates of regional precipitation (from Fekete et al. 1999).

River discharge is one of the more accurate ob-servations associated with the global hydrologi-cal cycle. However, real-time river discharge datahas been underutilized within the ocean-atmo-sphere modeling community due to typical three-to-five-year delays in data posting (GRDC 1996),network closure, and data policy restrictions.

Recent work (Fekete et al. 1999) has demon-strated the capacity to identify possible sourcesof error in particular elements of the water cyclewhen judged objectively against the instrumen-tal record. The figure above shows the spatialdistribution of potential biases in precipitationwhen compared against observed discharge anda physically consistent water budget model. It isnoteworthy that the Arctic, when analyzed fromthe standpoint of river discharge records overlarge river basins, shows sizable underestima-tion. This corroborates, from an independentperspective, the well-known problems with gaugecatch and interpolation bias in both liquid andsolid precipitation measurements in such harshenvironments (Groisman 1991, Groisman et al.2001, Willmott and Matsuura 1995).

The experiment shown in the figure indicatesthat by combining otherwise decoupled data setsand models, we can assess the degree of uncer-tainty and potential bias (see also Box 2-4). Inaddition, it lends hope that the synergy embod-ied in these data sets can yield a mutually con-sistent picture of water and energy budget clo-sure. ARC-ISM should be used to optimize suchan integration of data and model results andcould beneficially be applied in the design offuture monitoring systems for the pan-arctic sys-tem. These should be optimized to retrieve infor-mation of direct value to the scientific objectivesof Arctic-CHAMP. However, of particular notewould be the additional use of ARC-ISM derivedproducts to help improve operational forecastand reanalysis products from weather predictionservices. A coherent pan-arctic observationalprogram in support of Arctic-CHAMP thuswould provide an important framework for im-proving our capacity to monitor change over theArctic and to interpret its impact.

WBM Runoff Correction Coefficients30-minute spatial resolution

25

Box 2-6. Remote Sensing Support for Pan-Arctic Synthesis

Daily Maximum Air Temperature Interpolatedfrom Met Stations

31 March 12 April 20 April 26 April1997 1997 1997 1997

Comparison of maximum air temperature, inter-polated from measurements acquired from 72meteorological stations in Alaska with freeze/thaw index maps derived from two-day NASAScatterometer (NSCAT) satellite sensor compos-ite mosaics. NSCAT was extremely sensitive tothe presence of unfrozen water on the surface ofthe snow or ground and is therefore a promisingplatform for determining hydrologic conditionsover wide areas. The bottom four graphs showtemporal series of NSCAT backscatter at four lo-cations along a north-south transect extending(1) from Toolik Lake on the north slope of theBrooks Range, (2) to the Dietrich Valley, sur-rounding Coldfoot, Alaska, near the northernlimit of the boreal forest, (3) through the Bo-nanza Creek Experimental Forest in the centralinterior, and (4) to Denali National Park in theAlaska Range. Each point on the four graphs rep-resents mean NSCAT backscatter computed overa 50 km region centered at the respective groundlocation. The broken vertical lines mark thetimes initiating the two-day NSCAT compositemosaics. Remote sensing will provide critical ob-servational support to Arctic-CHAMP synthesisstudies. From the unique vantage point of space,satellite-based sensors constitute an importantmonitoring asset for constructing comprehen-sive views of the changing biogeophysical char-acter of the entire pan-arctic domain (see Walshet al. 2001). Use of such remote sensing data setswill be critical to observational support for pan-arctic synthesis studies as part of Arctic-CHAMPand to afford pan-arctic coverage.

Figure from Running et al. 1999.

NSCAT-Based Freeze/Thaw State



Box 2-7. Arctic-CHAMP Framework Application:Prognostic Simulation

The Arctic-CHAMP model can be used in a prog-nostic mode to produce high-resolution sets ofscenarios on the potential future state of thepan-arctic system. The ARC-ISM model couldeasily be envisioned to represent a regionalsimulation nested within a larger earth systemmodel, but with higher detail in its physical rep-resentation of land surface hydrology, ecosystemand vegetation state, coastal and Arctic Ocean,sea ice, and the dynamic atmosphere. The cou-pling has several advantages. It permits the full-system behavior to be assessed, as well as anysubcomponents that would be the targets ofmore focused studies, thereby enabling feed-backs to be better elucidated. In addition,through scenario analysis it could be used to testfor system sensitivities. And, using results de-rived from the error analysis developed underthe diagnostic mode, ARC-ISM could be used topredict the impact of uncertainties in our under-standing of possible future trajectories of envi-ronmental change.

Changes in annual mean surface air temperature(top), precipitation (center), and surface solar ra-diation (bottom) over the 100 years from 1961–1990 to 2061–2090, according to a greenhousesimulation by the GFDL coupled global climatemodel. Units are degrees C, mm per day, and Wattsper square meter, respectively. Yellow and red denoteincreases; green and blue denote decreases, and graydenotes little or no change (IPCC Data DistributionCenter, http://www.dkrz.de/ipcc/ddc/html/dkrzmain.html).

27

Box 2-8. Arctic-CHAMP Framework Application:Human Dimensions

The interactions between humans and the hy-drological cycle in the Arctic are an integral partof the Arctic-CHAMP concept. Humans are re-sponsible for damming rivers, deforestation,and agriculture, which alter the timing, amount,and quality of runoff to the ocean. Conversely,arctic hydrological conditions affect humansinhabiting the Arctic in many other ways (seeTable 5-2). Ice and snow affect the everyday livesof arctic residents, including their commercialactivities as well as traditional hunting and fish-ing. Permafrost changes affect the stability ofengineering works such as roads, hospitals,schools, houses, pipelines, and industrial struc-tures. Sea ice conditions affect both coastalhunters and commercial shipping alongAlaska’s arctic and Chukchi coasts, Canada’sNorthwest Passage, and the Northern Sea Routeof Russia.

These issues have a fundamental geophysicalunderpinning which will be integrated withinArctic-CHAMP. The necessary links to these dy-

namics must be made by a consortium of physi-cal and biological scientists and socioeconomicexperts. Human dimension considerations havesometimes been treated merely as speculative oras anecdotal adjuncts to natural-science re-search. Arctic-CHAMP could serve as a vehiclefor more empirical, observational researchaimed at understanding the links between hu-man systems variables and arctic hydrology.Documenting changes observed by indigenouspopulations would be especially important inthis context, owing to the strong dependence ofnative residents on the arctic environment.Physical science and modeling work will seek toidentify aspects of arctic hydrological systemsthat have varied substantially in the recent past,and/or appear likely to exhibit substantialchange in the future. Researchers can then usethis information as a starting point to systemati-cally investigate the societal implications, in-cluding human responses to the hydrologicalvariations that are already being observed.

A tundra pond was created among thePrudhoe Bay oil fields after a shortgravel road was removed. Anthropo-genic influences may have direct or in-direct impacts on the hydrologic system(photo by L. Hinzman).



Figure 3-1. A view of the pan-arctic region, showing the contributing drainage basin of the Arctic Ocean and its numer-ous seas. Blue lines represent relative river discharge. The coupling of atmosphere-land-ocean is strong, and knowledge ofthe region’s hydrologic cycle is central to our understanding of the sensitivity and reaction of the overall arctic system toglobal change (from Forman et al. 2000).

29

Role and Importance ofWater in the Arctic System

to examine how the arctic hydro-logic cycle interacts with thecoupled land-ocean-atmospheresystem.

In this section, we first review themultiple roles that water plays ineach of the major domains of thepan-arctic system, namely land,atmosphere, and oceans. We thenturn to the question of how thearctic water cycle functions in thelarger arctic and earth systems.

Land

Water responds strongly to the ex-treme contrast between summerand winter conditions over the arc-tic land mass (Figure 3-2; Box 3-1).During the thaw season water runsoff, transporting mass, energy, andmomentum through watershedsand ultimately to the Arctic Oceanin ways similar to lower latituderiver systems. But unlike water-sheds in more temperate regions,snowmelt runoff produces nor-mally a single, sharp peak flowevent for the year. Water cyclingthrough arctic landscapes providesthe moisture plants need; is asource of vapor to the atmosphere;and through runoff, transportssediment and other constituents tothe ocean. Surface flow, ponding,and freeze-thaw are the primarydrivers of erosion and geomorphicchange because thermal, along

with mechanical factors, regulatethe runoff and erosion processes.In sharp contrast, during the longfrozen season water itself becomesthe land surface in the form of lakeice, river ice, and most importantly,snow, which radically increases theland surface albedo (reflectivity)and reduces the solar energy ab-sorbed, but at the same time pro-vides a blanket of high-quality in-sulation that reduces ground heatlosses.

Seasonal delays in the storage andrelease of snowpack are extremelyimportant in regulating connec-tions between the land surface andoverlying atmosphere and high-light the complexities associatedwith the hydrological cycle’s roleinside the arctic system. The nine-month-long winter, with strongnegative energy balance, thusserves as an important storehousefor water that is later destined tobecome runoff or precipitationthrough local recycling. The sea-sonal storage of snowpack repre-sents water imported into the Arc-tic from great distances, and thusemphasizes an important link ofthe pan-Arctic to the larger climatesystem. Large river basins thentransport this water equally greatdistances with eventual delivery tothe coastal seas of the Arctic Ocean.

The Integrated Water Cycleof the Pan-Arctic

T he hydrologic cycle fig-ures prominently in thedynamics of energy andconstituent exchange

among the land, atmosphere, andoceanic components of the arcticand larger earth system (Figures1-1, 1-3). The coupled arctic land-atmosphere-ocean system is com-plex, and without a comprehensiveunderstanding of the integratedwater cycle, we cannot hope to un-derstand the changing arctic envi-ronment or the global conse-quences of this change.

For this assessment, we maintain abroad conceptual and geographicdefinition of the pan-arctic region.Geographically, the pan-Arctic is amore or less well-bounded seg-ment of the larger earth system(Figure 3-1). The land mass drain-ing into the Arctic Ocean and dis-charging freshwater through theBering Strait can be easily identi-fied (Lammers et al. 2001, Prowseand Flegg 2000), together with theocean fluxes from the Pacific andexchanges with the North Atlantic.In addition, the arctic circumpolarcirculation, including the PolarFront, is a fundamental feature ofthe earth’s climate system that canbe clearly tracked. We use this do-main as our organizing framework

3

3. Role and Importance of Water in the Arctic System


Figure 3-2. Example of a permafrost dominated landscape with sharp contrasts in the state of water cycling between thelong winter and short summer (photographs courtesy of J. Holmgren, L. Hinzman, Y. Kodama).

A unique and important feature ofarctic hydrology associated withthe long, cold winter is the pres-ence of permafrost and a summeractive layer (the layer of soil abovethe permafrost that thaws eachsummer). Permafrost limits theamount of subsurface water stor-age and infiltration that can occur,leading to wet soils and ponded

surface waters, unusual for a regionwith such limited precipitation.Active layer thickness and perma-frost conditions are largely con-trolled by surface heat fluxes, cou-pling the hydrology to the surfaceenergy balance so closely that theycannot be quantified separately. Insummer, solar heating leads torapid thawing of the active layer,

while in winter, a delicate balancebetween the thermal insulation ofthe snow cover and its high albedocontrols the rate and severity offreezing. Since large stocks of or-ganic carbon are currently seques-tered in permafrost, changes in thecoupled thermal-hydrologic systemhave the potential for creating im-portant feedbacks to the globalcarbon cycle.

31

Box 3-1. Unique Water Cyclingin the Arctic

Terrestrial hydrology in the Arctic differs substantially from hy-drology at lower latitudes in several important ways:• great contrasts occur between summer (liquid water) and win-

ter (solid water) hydrological states;• extensive and long-lasting snow cover insulates the ground and

reflects solar energy;• permafrost and an active layer control soil moisture and fluvial

erosion, and intimately link hydrology to the thermal balanceof the soil;

• vegetation cover, closely coupled to soil moisture and the activelayer, affects surface energy exchange—causing feedbacks to hy-drologic and thermal systems; and

• freeze-thaw controls hydrological cycling and thus the abruptseasonal changes in available nutrients to arctic plants, flux ofbiogenic gases to the atmosphere, and export of carbon and nu-trients to rivers and seas.Strong seasonality characterizes arctic hydrology (Figure 3-2).

During the long winter, precipitation is stockpiled as snow, whilelakes and rivers are frozen. Winter radiation balance is dominatedby longwave losses to space. The short, intense spring thaw starts aperiod of more vigorous transport. Spring runoff produces thehighest discharge values of the year (Grabs et al. 2000) and waterbegins to infiltrate the still-frozen ground (Kane and Stein 1983).As spring warms into summer, surface soil layers thaw, providingwater and nutrients to plants. Evaporative rates increase, and runoffincreases substantially—often tenfold or more.

Large changes in surface energy balance follow this annualcycle. During winter up to 85% of incoming shortwave solar radia-tion is reflected (Geiger 1957, Barry 1996), but sensible heat lossfrom the ground is reduced by continuous snow cover, an excellentthermal insulator (Mellor 1964, Sturm et al. 1997). In summer,vegetation type and its insulation capacity affect the ground’s ther-mal state (Eugster et al. 1997, McFadden et al. 1998). Annual en-ergy balance determines the temperature of permafrost as well asthe thickness of the active layer. These in turn interact with surfaceand subsurface water flows.

Much of the Arctic resembles a desert, in terms of annual pre-cipitation—less than 200mm per year in some regions (Korzoun etal. 1978). But this is a desert that can look like a bog, with wetsoils and lush green vegetation. Permafrost prevents surface waterfrom draining, supporting the formation of hydrophilic ecosys-tems. Should the climate warm or the surface be disturbed, how-ever, warm permafrost can degrade. Thermokarsts (Figure 5-2)form as ice-rich soils or massive ice thaw. Then, surface soils sub-side, creating large depressions or ponds. If thawing continues,taliks (layers of unfrozen soil above permafrost) persist through theyear. These taliks allow soils to drain and set in motion dramaticchanges in vegetation.

Atmosphere

The atmosphere carries waterevaporated from the oceans andprecipitates it in the form of rainand snow onto arctic land areas,oceans, and sea ice. Much of thewater and energy comes fromlower latitudes in the form of wa-ter vapor, making the atmospherean important conduit connectingthe rest of the globe to the Arctic.In addition, this poleward atmo-spheric transport carries with itcontaminants and other chemicalspecies into an otherwise “pris-tine” environment. Annual precipi-tation falling onto arctic riverbasins is modest in comparison tothat in lower latitudes because coldair masses are unable to holdmuch moisture. During the winter,precipitation is almost entirely inthe form of snow and the winter-time precipitation rate is abouthalf that in summer, which to-gether with modest rates of evapo-ration and sublimation, leads to alimited local recycling of water.Although snowfall can occur onany day of the year, summer pre-cipitation varies from primarilyrain in the south to mixed rain andsnow in the north. Maximum pre-cipitation rates occur in the shortsummer season, often in conjunc-tion with thunderstorm clouds.High evaporation rates in summerlead to predominantly localizedrecycling of water. The freeze-thawcycle, affecting the seasonal accu-mulation of snowpack, snowmelt,and the mobilization of waterthrough soil and vegetation duringthe summer, is a dominant featureof the hydrology of the Arctic.



Figure 3-3. Snowmelt is usually the dominant hydrologic event of the year inwatersheds dominated by snow and ice. Monitoring snowmelt and the resultantrunoff is essential to quantify the annual water balance in arctic and subarcticwatersheds (photo by L. Hinzman).

Ocean

The timing and distribution offreshwater inflow critically affectsArctic Ocean circulation as well aswater and energy exchanges withthe atmosphere. Principal freshwa-ter sources are in the form of dis-charge delivered by north-flowingrivers. Warm, salty Atlantic waterenters the Arctic Ocean throughthe eastern side of Fram Strait andacross the Barents Sea shelf (Figure3-1). Less saline Pacific water en-ters through the Bering Strait.These fresh and saltwater sources,combined with sea ice freezing andmelting and wind-driven circula-tion, produce an outflow throughthe western part of Fram Strait andthe Canadian Archipelago that in-cludes nearly fresh sea ice, coldsurface water of relatively low sa-linity, and deeper water masseswith salinities close to that of theAtlantic inflow.

The freshwater input is importantto Arctic Ocean dynamics by con-tributing to the formation of thecold halocline layer, a water masswith a strong salinity gradient andnear freezing temperatures, lyingbetween the surface mixed layerand deeper, warm, salty Atlanticwater. The estuarine and shelfzones between fresh river and Arc-tic Ocean waters have a particularlyimportant role to play in these dy-namics and may be especially sen-sitive to future change (MacDonald2000). The maintenance of thecold halocline is important to thethermodynamics of the ocean ba-sin. The temperature is so cold thatit provides little heat to the mixedlayer and ice, and the strong strati-fication of the cold halocline in-hibits turbulent mixing of heat up-

ward to the ice from the warmerAtlantic water below.

The freshwater output from theArctic Ocean, in the form of sea iceand reduced salinity sea water, ar-guably has a large effect on the glo-bal ocean because it increasesstratification in the Nordic and La-brador seas, reducing the deepconvective overturning and therebyweakening the thermohaline circu-lation of the North Atlantic(Carmack 2000). In addition toaffecting the thermohaline circula-tion for the whole earth, thischange in the condition of theNorth Atlantic may directly feed-back on the arctic freshwater cycleby changing the flux of heat andmoisture through the atmosphere.

Importance of ArcticHydrology to the ArcticSystem

Over the annual cycle, the terres-trial water cycle embodies a com-plex series of processes that regu-

late evaporation, changes in mois-ture storage, and runoff. Precipita-tion and evaporation serve as thecritical links between the atmo-spheric and terrestrial segments ofthe hydrologic cycle. Land surfacehydrologic budgets can be definedby the changes in total water stor-age (i.e., in soils, ground, and sur-face waters) which in turn equalthe sum of time-varying precipita-tion, evaporation, and net runoff.The seasonality of frozen versusunfrozen landscapes is the defini-tive characteristic of arctic hydro-logical systems. Snowmelt typicallygenerates the bulk of seasonal ex-cess water and must be routedthrough soils and groundwater oroverland into stream channels(Figure 3-3). In permafrost-domi-nated areas, the freezing and thaw-ing of frozen soil is critical to thetiming of plant growth and evapo-ration, infiltration, and runoff aswell as the presence or absence ofwetlands (Figure 3-4). These pro-cesses have been observed, butquantifying them over many pan-

33

arctic hydrological regimes in or-der to compute water budgetsremains both an open area of re-search and a significant monitor-ing challenge.

The delivery of freshwater from thecontinental land mass is of specialimportance to the Arctic Oceansince it contains only 1% of theworld’s ocean water, yet receives11% of world river runoff(Shiklomanov et al. 2000). TheArctic Ocean is the most river-in-fluenced and landlocked of alloceans and is the only ocean witha contributing land area greaterthan its surface area (Ivanov 1976;Vörösmarty et al. 2000). Annualfreshwater inflow contributes asmuch as 10% of the freshwater inthe upper 100 meters of the watercolumn for the entire Arctic Ocean(Barry and Serreze 2000). Approxi-mately three-quarters of ArcticOcean riverine freshwater inputderives from the Eurasian portionof the Arctic Ocean watershed, andthree rivers (Yenisei, Lena, Ob) areresponsible for approximately 70%of this contribution (Carmack1990, Gordeev et al. 1996). Thiswater exerts a tremendous influ-ence on the Arctic Ocean and espe-cially on the Eurasian shelf seas(the Barents, Kara, Laptev, and EastSiberian). Salinity distribution andsea ice formation are affected bycontinental runoff. As mentionedbefore, the cumulative impact ofchanges in freshwater flux to theArctic Ocean may exert significantcontrol over global ocean circula-tion by affecting the volume ofNorth Atlantic Deep Water forma-tion (Aagaard and Carmack 1989,WMO/World Climate ResearchProgram 1994, Broecker 1997).

River inputs of water and constitu-ents influence delta, estuarine, andnear-shore ecosystems that havehistorically provided the basis forsubsistence of northern Eurasianhuman populations. Climatechange during the transition fromthe Pleistocene to the Holocenewas accompanied by major shiftsfrom utilization of terrestrial foodsto use of riverine and coastal ma-rine resources including fishes andmammals (Makeyev et al. 1993).

Importance of the Arctic tothe Earth System

From a large body of GCM experi-ments, the Arctic is thought to beparticularly sensitive to global cli-mate change (Manabe et al. 1991,Manabe and Stouffer 1995, Hough-ton et al. 1996, 2001; Watson et al.1998). Manabe et al. (1991) showthat under a representative globalwarming scenario, temperature in-creases will be amplified in theArctic, and the upper Arctic Oceansalinity will decrease due toenhanced precipitation at high

latitudes. Analysis of a broad suiteof archived hydrometeorologicaldata sets further supports this viewand suggests the presence of a glo-bal warming signal across the re-gion (Serreze et al. 2000). Prelimi-nary assessments for some regionsof the Arctic show that recentchanges in winter temperature andmean annual precipitation haveaffected local runoff conditionsand river discharge to the ArcticOcean (Lammers et al. 2001,A. Shiklomanov 1994, I. Shiklo-manov 1997, Georgievsky et al.1996). At the same time tele-connections have been establishedbetween El Niño Southern Oscilla-tion (ENSO) events and climateanomalies in parts of the arcticdrainage system (Brown andGoodison 1996, Shabbar et al.1997).

Key indicators of global changethus involve major components ofthe high-latitude water cycle, andthe reciprocal response of the Arc-tic—beyond its land-based hydrol-ogy—must be considered. For


Figure 3-4. Arctic wetlands depend on the presence of permafrost (photo by L.Hinzman).


example, the Arctic Ocean’s stratifi-cation and ice cover provide acontrol on the surface heat andmass budgets of the north polarregion, and thereby on the globalheat sink (e.g., Manabe et al.1991). If the distribution of seaice—a significant stock of arcticfreshwater—were substantially dif-ferent from that of the present,then the altered surface fluxeswould affect both the atmosphereand the ocean and would likelyhave significant consequences forregional and global climate. Also,the export of low-salinity waters,whether liquid or in the form ofdesalinated sea ice, has the poten-tial to influence the overturningcell of the global ocean throughcontrol of convection in the sub-polar gyres, which in turn feed theNorth Atlantic (Aagaard andCarmack 1989). Recent sugges-tions that North Atlantic and Eur-asian climate variability may bepredictable on decadal time scales(Griffies and Bryan 1997) rest inpart on the variability of such up-stream forcing in the GreenlandSea (Delworth et al. 1997).

Central Question: What Are the Major Features and Natural Variabilityof the Pan-Arctic Water Balance?

Key Gaps in Current Understanding and Needed Studies:• Fluxes throughout the water cycle (atmospheric vapor transport pre-

cipitation, evaporation, soil water, runoff)• Arctic atmospheric teleconnections to the larger climate system• Role of seasonal snowpack and permafrost water storages• Runoff generation and pathways• Continental discharge and connections to sea ice and deep ocean

convection

On the atmospheric side, results ofThompson and Wallace (1998)and others show that the atmo-spheric circulation of the NorthernHemisphere changes as part of apole-centered pattern, termed theArctic Oscillation (AO). Recentmodeling studies suggest the AO isa fundamental mode of atmo-spheric change and that the posi-tive trend seen in recent decadesmay be symptomatic of the green-house effect (Fyfe et al. 1999,Shindell et al. 1999).

Consideration of the coupled setof atmosphere-ocean interactionsis thus absolutely essential to ourunderstanding of the ultimate im-pact that arctic environmentalchanges have on the earth system.The hydrological cycle will figureprominently in any such analysis.

35

Unprecedented Change toArctic Hydrological Systems

et al. 1997, Overpeck 1996,SEARCH SSC 2001, Serreze et al.2000).

The multiagency SEARCH SciencePlan (SEARCH SSC, 2001) pro-vides an in-depth analysis of thespatial and temporal extent of re-cent changes to the arctic system.Many significant changes are ob-servable from what is admittedlyan incomplete and in many casesfragmentary record. The reviewgiven below focuses on the arcticsystem as well, but highlights thosechanges related specifically to thearctic water cycle.

Changes to the Land-BasedHydrologic Cycle

A wide range of changes in terres-trial arctic hydrology has been de-tected, and many of these changesstarted, or accelerated, in the mid-1970s. The arctic hydrologic systemis particularly sensitive to changesin the magnitude and timing ofrain and snowfall, freeze-up andthaw, and the intensity and season-ality of storm activity that reflectchanges in large-scale atmosphericcirculation rather than simple re-sponses to temperature increases.Although historical changes inthese fields are poorly known andcharacterized by enormous spatialand temporal variability, observa-tions suggest that the arctic hydro-

logic system may be entering astate that is unprecedented, at leastover a historical timeframe (Serrezeet al. 2000, Lammers et al. 2001).

Integrated measures of hydrologi-cal status, such as glacier mass bal-ance studies that record both sum-mer and winter precipitation,indicate that over the last 30 years,smaller glaciers in the Arctic haveexperienced decidedly negativemass balances (Dyurgerov and

C hange is an inherentproperty of the Arctic,with the paleoclimaticrecord providing

ample evidence of the enormouschanges experienced by the regionsince the last glacial maximum(Mayewski et al. 1994, Alverson,Oldfield, and Bradley 2000). Thesystem has alternately experiencedextensive and thick ice sheets, theblockage of northward flowing riv-ers, exposed coastal shelf regions,giant catastrophic floods, and mostrecently the complex signature ofhuman-induced climate change.High-resolution paleo-records in-dicate that arctic climate can moverapidly from one regime to an-other, resulting in the anomalouspersistence of warm temperatures,shifts in seasonality, extremeevents, and changes in ocean circu-lation (e.g., Bond et al. 1999, Dou-glas et al. 1994). These and manyother paleoclimate studies providean understanding of arctic hydro-logic variability and are needed toplace the recent observations of Arc-tic system change into appropriatecontext (Stein 1998). Althoughchanges to many environmentalvariables have occurred previouslythroughout geologic time, the rateof changes observed within the lastfew decades to century are quitelikely unprecedented and indeedhave evoked a sense of urgencywithin the community (Overpeck

Figure 4-1. The McCall Glacier in theRomanzof Mountains of Arctic Alaskahas been losing mass since measure-ments began in 1957, with acceler-ated losses over the last two decades(Rabus et al. 1995).

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4

4. Unprecedented Change to Arctic Hydrological Systems


Meier, 1997). The 1957 to 1995record for McCall Glacier in arcticAlaska (Figure 4-1) shows that themass balance has not only beennegative, but the rate of down-wasting has increased dramaticallysince 1976 (Rabus et al. 1995).The Greenland Ice Sheet has alsoincreased in melt area throughoutthe 1980s (Abdalati and Steffen1997), and the associated reduc-tion in volume is about equal tothose of all the smaller glacier sys-tems in the Arctic (Dyurgerov andMeier 1997).

Observed responses of arctic riversystems to changes in temperatureand precipitation reflect a complexset of spatial patterns, including amean delay of nine days for freeze-up and a ten-day earlier icebreakup date for lakes and rivers,comparing conditions 150 yearsago to today (Figure 4-2;Magnuson et al. 2000). Trendanalysis of river outflow has beeninconclusive. Shiklomanov et al.(2000) suggest very little change inmean annual discharge for largerivers over the last several decades,whereas Semiletov et al. (2000)document increases for severalEurasian rivers. Changes in the sea-sonal pattern of discharge in manyArctic rivers have occurred(Savelieva et al. 2000), but thesechanges are challenging to detectbecause of large natural variations.Changes in the base flow, such asthe increases in the Yenisei Riverbetween 1936 and 1995 (Figure 4-3) (Yang et al. in review), are moredistinct and thought to reflect in-creased groundwater infiltrationcoupled to reductions in perma-frost and an increase in active layerthickness due to warmer tempera-tures (Figure 4-4). A recent analysis

of discharge records from severalhundred stations distributed acrossthe pan-Arctic (Lammers et al.2001) indicates there has been anincrease in winter flow in severalSiberian river basins during the1980s. Such hydrologic changescan impact stream habitat, increaseicing, and elevate the export ofsediment and solutes to the ocean.

Changes to the Atmosphere

Within the atmosphere, evidenceof unprecedented change is docu-mented in the instrumental recordof precipitation and temperatureas well as in changes in synopticscale circulation and variability.The paleo perspective extends therelatively short instrumental

Figure 4-2. With increasing temperature, there have been noticeable changes inthe dates of freeze up and ice breakup in many lakes and rivers of the Arctic.The average change over the 150-year period was nearly nine days later forfreeze up dates and almost 10 days earlier for ice breakup dates of rivers andlakes in the Northern Hemisphere (Magnuson et al. 2000).

YEAR

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Breakup Sites

37

period and thus provides a morecomplete context for interpretingrecent hydrologic variability andchange. Overpeck et al. (1997)used a multiproxy regional synthe-sis to determine that arctic summerair temperatures of the 20th cen-tury have been the highest in thelast 400 years, despite showingboth positive and negative shorterterm temperature trends. Onewarm period began in the 1920sand extended to the late 1940s; asecond, still underway, started inthe 1970s (Figure 4-5). The instru-mental record of change in theArctic indicates that high northernlatitudes have increased in meanannual temperature by ~1˚C, withthe largest increase in winter tem-peratures (~2˚C), whereas summertemperatures increased by ~0.5˚C(Lugina 1999, Lugina et al. 2001).Serreze et al. (2000) confirm thattemperature changes are spatiallycomplex, with warming in north-ern Eurasia and western NorthAmerica but cooling in easternCanada and southern Greenland(Figure 4-6).

Instrumental precipitation recordsdocument a significant increaseover northern Eurasia (Groisman1991) over the last 50 years acrossnorthern North America(Groisman and Easterling 1994),whereas in eastern Russia over thesame period there has been a de-crease in summer precipitation(Sun and Groisman 2000). Thisdecrease in eastern Russia over thelast 50 years has been accompa-nied by a replacement of stratiformclouds with convective clouds.Overall, across much of Russiathere has been an increase in con-vective cloudiness associated withan increase in the number of days

Figure 4-3. The base flow (non-surface runoff) of the Yenisei River increasedmarkedly over the period from 1936 to 1995. For each month the plot showsthe average conditions for each sequential year. This change is postulated toarise from increased groundwater infiltration coupled with permafrost degrada-tion, which itself is a response to climate warming (Yang et al., in review). Theconstruction of large artificial impoundments may also contribute to thesechanges.

Yenisei River at Igarka, 1936–1995

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Figure 4-4. Springs represent an important connection between groundwaterand surface water, often forming at the permafrost boundary. Presence of well-developed minerotrophic vegetation indicates the spring has existed for manyyears. As permafrost degrades, the connections between groundwater and sur-face water increase, allowing springs to form or in some cases ponds to shrink(photo by L. Hinzman).



with heavy precipitation (Sun et al.2001).

The primary modes and variabilityof the North Atlantic Oscillation(NAO), and the closely related Arc-tic Oscillation (AO), determineinterannual precipitation varia-

tions over Eurasia and easternNorth America whereas westernNorth America responds to vari-ability in the North Pacific Ocean.Consistent with intensification ofthe NAO/AO over the last two de-cades, winter precipitationamounts and surface air tempera-tures have been increasing in

northern Eurasia, decreasing insouthern Eurasia, and decreasingin northeastern Canada in re-sponse to enhanced storm activityin northern latitudes (Serreze et al.2000). Over the same period thatwinter precipitation has increased,there has been a dramatic declinein northern hemisphere snowcover (Robinson 1999) (Figure4-7). Eurasian snow cover extenthas decreased over the past 20years (primarily in the spring andsummer; Groisman et al. 1994).The same is true for Alaska whereduring the past 50 years a generalretreat of spring snow cover wasreported (Groisman et al. 2001).Most of this retreat has occurredduring the past two decades, result-ing in an earlier onset of spring byapproximately two weeks.

These climate trends are consistentwith greenhouse warming, how-ever, uncertainty remains whetherthese phenomena reflect naturalclimate variability, anthropogenicforced (i.e., “global warming”) or acombination. Changes in rainfall,snowfall, and the recycling of wa-ter back to the atmospherethrough evaporation and sublima-tion are difficult to assess from theinstrumental record because thenetwork of stations is sparse anddata collection difficult (Black1954; Woo et al. 1983; Yang et al.1999, 2001). Summer precipita-tion trends, determined by com-puting precipitation (P) minusevaporation (E) from numericalweather prediction model reanaly-sis (Walsh et al. 1994, Serreze et al.1995, Cullather et al. 2000), reveallittle systematic change over thepast 30 years. Site-specific studiesoften yield less ambiguous results.In locations where direct land-

Figure 4-5. Time series of temperature anomalies for the 20th century for theNorthern Hemisphere from 55o to 85o N (based on update to Eischeid et al. 1995).

DJF

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39

Figure 4-6. The geography of recent circumarctic temperature change. Updatedfrom Chapman and Walsh (1993).

based measurements have beenavailable (Oechel et al. 2000), anobserved trend toward increasingsummer precipitation (1960 to1998) has been offset by increas-ing air temperature and evapo-transpiration, resulting in a netgain of water vapor to the atmo-sphere and drying of the soil (Fig-ure 4-8).

Although pan-arctic data sets ofcritical hydroclimatic variables canbe assembled at relatively highresolutions using state-of-the-artinterpolation and gridding tech-niques (Price et al. 2000, Willmottand Rawlins 1999), accuracy islimited by a deteriorating networkof ground-based monitoring sta-tions. Intercomparison tests(Rawlins 2000) suggest that notonly are new techniques still


Figure 4-7. Understanding the pro-cesses controlling the variability ofsnowpack properties and snow coverdistribution are critically important tounderstanding the current hydrologicregime and in predicting potentialresponses to climate change (photo byL. Hinzman).


Figure 4-9. Impact of interpolationtechnique on the resulting bias inpan-arctic temperature climatologies.Latitudinally averaged (over 30’ lati-tude bands) mean surface tempera-ture for winter is shown for traditionalspherical interpolation versus Digitaltopography-Aided Interpolation (DAI)(Rawlins 2000). This graphic high-lights the need to address systematicerrors in our monitoring of hydrologi-cally relevant variables across the pan-Arctic.

Figure 4-8. Changes in precipitation (P), potential evapotranspiration (PET),and their difference, a measure of net water available for soil water rechargeand runoff. These data represent measurements made at four sites in northernAlaska. A net change in CO

2 flux is also tabulated as terrestrial primary pro-

ductivity and ecosystem respiration are linked closely to moisture availability atthese sites during the growing season (Oechel et al. 2000).

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Anecessary to narrow the substantialgaps in our detection of climatewarming but a substantial upgrad-ing of station holdings remainscritical (Figure 4-9).

The Changing Arctic Oceanand its Regional Seas

Recent hydrologically relatedchanges within the Arctic Oceansystem include increased salinity inthe central region, shrinking of thecold halocline layer, and decreasedsurface salinity off of westernNorth America (SEARCH SSC,2001). Specific hydrological obser-vations include changes in ice driftpattern, decreased sea ice extent,and decreased sea ice thickness.Arctic sea ice extent decreased by2.9 +/- 0.4% per decade over thelast 30 years (Cavalieri et al. 1997)and analyses of passive microwavetime series from satellites indicatethat ice reductions have been ac-companied by an increased lengthof ice melt season (Smith 1998).Arctic sea ice thickness measuredby U.S. Navy submarines over thelast 20 years record an average43% reduction in thickness for thecentral Arctic Ocean (Rothrock etal. 1999). The yearly average pres-sure maps indicate a shift in the

41

Box 4-1. The Arctic Oscillation andHypothesized Connections to the Water Cycle

Based on extensive oceanographic observation, critical changes inthe Arctic Ocean and changes to the land-based hydrologic cycleare hypothesized to relate closely to the onset of the Arctic Oscilla-tion (AO) (Thompson and Wallace 1998). The working hypothesisis that as the AO index rises, the strength of the polar vortex in-creases, and the surface pressure in the Arctic Basin decreases,weakening the Beaufort high (Walsh et al. 1996). This applies posi-tive vorticity to the sea ice and ocean circulation (Proshutinsky andJohnson 1997), resulting in reduced convergence in the BeaufortGyre. This in turn results in more open water, greater radiative heatinput, increased summer melt, and decreased Beaufort Sea surfacesalinity (McPhee et al. 1998). The change in circulation may alsoaccount for the decreased ice cover on the Siberian shelves(Maslanik et al. 1996). Increasing surface air temperatures are alsothought to influence land-based freeze-thaw with potential accel-eration of the terrestrial water cycle.

Steele and Boyd (1998) argue that the change in circulation re-routes Siberian river runoff to the east rather than allowing it tomix with Atlantic water, cool, and move cross-shelf to form coldhalocline water. It is thereby responsible for thinning the cold ha-locline layer. The shift of Siberian runoff to the east may also be in

part responsible for the fresh-ening of the upper layers ofthe Beaufort Sea (McPhee etal. 1998, Macdonald et al.1999). The increased cyclonicvorticity added to the ArcticOcean may also act to drawsurface water from the lowersalinity, western region of thebasin and increase the amountof fresh surface water flowingout through Fram Strait. Thiscould increase stratification inthe Greenland Sea and con-tribute to the weakened deepconvection observed there inrecent years (Aagaard et al.1991, Schlosser et al. 1991).

An intriguing possibility isthat reduced thermohaline cir-culation imposes a negativefeedback on this system bycausing less northward oceanheat flux into the Nordic seasand thereby cooling northernEurope and Russia, with im-portant consequences for ter-restrial ecosystems and humansociety.

These complex interconnec-tions argue strongly for syn-thesis studies of the entirecoupled arctic system. Inte-grated monitoring and simu-lation—at the heart of theoverall Arctic-CHAMP initia-tive—will be essential to fu-ture progress in understand-ing these geophysicalprocesses.



position of the Beaufort high, usu-ally centered over 180˚ longitudebefore 1988–1989, to a more west-ern position and weakening there-after. These pressure anomalies arelinked to changes in ocean circula-tion patterns and therefore the dis-tribution of sea ice, terrestrially de-rived runoff, and salinity.

Collectively these changes repre-sent some of the most compellinglines of evidence for arctic environ-mental change and suggest a sub-stantial reorganization of the ArcticOcean system, with important im-plications for ice cover, the ice-al-bedo feedback, and the terrestrialwater cycle. These changes alsohighlight the integrative nature ofthe hydrologic cycle, linking land,atmosphere, and ocean. Box 4-1describes some of the hypoth-esized links between the ArcticOcean and freshwater dynamics.The full impact of the unfoldingchanges to the Arctic Ocean hydro-logic system remains unknown,but the dramatic changes evidentin numerous paleoclimate recordsunderscore the importance of un-derstanding both the magnitudeand consequences of contempo-rary hydrological changes acrossthis climatically sensitive region(Stein 2000).

Central Question: Are the Observed Changes in Arctic Hydrology Part ofthe Natural Variability or Are They Related Uniquely to Human-forcedGlobal Warming?

Key Gaps in Current Understanding and Needed Studies:• Design and implementation of long-term, coherent observational

programs for water-related variables over land, atmosphere, ocean,and cryosphere

• Historical and paleo studies to establish benchmarks by which con-temporary change can be measured

• Quantify the underlying processes controlling the natural variabilityand the observed unprecedented changes

• Studies that identify the causal agents of observed changes to arctichydrosystems

• Trend analysis for early detection of global climate change

43

5Impacts and Feedbacks Associated

with Arctic Hydrological Changetic and another considering hu-man dynamics.

Direct Impactson Ecosystems

Recent hydrological changes im-pact permafrost structure and sta-bility, the distribution of arctic veg-etation, and soil processesincluding CO

2 flux (Table 5-1).

Data from an extensive set of bore-holes indicate that permafrost tem-peratures have warmed 2 to 4˚Cacross the broad region of North-

ern Alaska during the last century(Lachenbruch and Marshall 1986).Farther south in regions of discon-tinuous permafrost, 1 to 1.5˚C ofwarming has been observed overthe last 20 years (Osterkamp andRomanovsky 1999). In someplaces, the warming is sufficient tothaw the permafrost, resulting insignificant landscape changes asmassive buried ice melts. Wherethe thawed ground sinks below thewater table, new swamps are cre-ated (Figure 5-1). In upland areas,drainage can be enhanced, convert-ing wetlands to a drier ecosystem(Figure 5-2). Drier soils no longersupport the plant and animal com-munities formerly adapted to livethere—one of the many challengesto arctic ecosystems posed by cli-mate change (Krajick 2001).

Recently observed changes in tem-perature, soil moisture, snow cover,and precipitation have resulted inspatially and temporally rich shiftsin vegetation. Mosses and othertundra species insulate the groundand reduce active layer thickness(Luthin and Guymon 1974).When disturbed by fire or a warm-ing climate, this ground cover isreplaced by shrubs or even treesthat change the thermal regime(Brown and Grave 1979). Localtree lines have been advancing insome places. Field studies have

A lteration of land surfacehydrology in the Arcticimposes both directand indirect effects on

“downstream” components of thearctic system. Important direct im-pacts are conveyed on terrestrialecosystems and human society. In-direct effects constitute feedbacksthrough which hydrologicalchanges in turn cause changes toatmosphere and ocean dynamics.We treat two broad classes of feed-back in this chapter, one involvingthe physics and biology of the Arc-

Figure 5-1. The hydrologic consequences of climate warming are very much sitedependent. The Tanana Flats (Lat. 64˚40’ Long. 147˚50’) is an area of ice-richpermafrost and upwelling groundwater. As the permafrost degrades with climatewarming, the surface collapses, and areas that were once birch and black spruceforests become flooded and are replaced by fens and bogs (photo from Jorgensonet al. 2000).

5. Impacts and Feedbacks Associated with Arctic Hydrological Change


Figure 5-2. Thermokarst formationnear Council, Alaska, has resulted invariable impacts to the local hydro-logic regime. New riparian channelsform as ice-rich permafrost degrades.As drainage improves in adjacent tus-sock tundra, soils become somewhatdrier and the proportions of shrubsincrease (photo courtesy of L.Hinzman).

demonstrated a transition in landsurface cover from graminoid-dominated to shrub-dominatedtundra (Chapin et al. 1995, Henryand Molau 1997, Jones et al. 1997,Walker et al. 1999, Silapiswan inpress), which could have impor-tant consequences for snow accu-mulation and winter biogeochemi-cal processes (McFadden et al.2001, Sturm et al. 2001, Liston etal. in press). Satellite remote sens-ing of NDVI (Normalized Differ-ence Vegetation Index) records anincrease in arctic plant growth andgrowing season between 1981 and1991 that is consistent with an in-crease in shrubs (Myneni et al.1997). A major challenge will beto monitor the progression of suc-cessional changes and their impacton seasonal evapotranspirationand runoff (Shiklomanov andKrestovsky 1988, Eugster et al.1997, McFadden et al. 1998,Chapin et al. 2000), especiallysince vegetation changes occur ondecadal time scales that are longrelative to observational records,

and thus difficult to detect. Box 5-1 schematically summarizes a fewof the ways in which biotic andabiotic systems might respond toclimate change.

The arctic terrestrial system playsan important role in global carbondynamics and may possibly be oneof the so-called “missing sinks”needed to balance the atmosphericcarbon budget (Tans et al. 1990,Ciais et al. 1995, Schimel 1995).Changes in arctic air temperaturesand precipitation impacting soilmoisture and snow cover have hadan important effect on the efflux ofCO

2 from the land, with global-

scale climate implications. In re-cent years there has been a shift inparts of the Arctic from a net an-nual sink to a net source of carbon(Oechel et al. 2000). During thegrowing season the system contin-ues to take up carbon (Figure 4-8),but this uptake is more than bal-

anced by winter losses (Jones et al.1997, Fahnestock et al. 1998,1999, Vourlitis et al. 1997, 1999,Oechel et al. 1997, Zimov et al.1993a, b).

Whether the arctic land surface is a“missing sink” or not, the effluxand sequestration of carbon in arc-tic soils is intimately linked withhydrology. Soil moisture deter-mines the rate of organic matterdecomposition, with cold, wetsoils generally limiting the decom-position process (Oberbauer et al.1989). At the same time, much ofthe plant growth in the Arctic isnitrogen-limited (Chapin et al.1995). Warming and drying notonly promotes greater carbonefflux through decomposition(Oechel et al. 2000), but also in-creases nitrogen mineralization,promoting a shift in plant commu-nity composition toward moreproductive functional groups

Figure 5-3. Waterfowl that migrate to the Arctic each year depend on tundraponds. Ice-rich permafrost prevents percolation of surface water to groundwaterand maintains these ponds despite relatively low rates of precipitation (photo byL. Hinzman).

45

(Chapin et al. 1995). The wholeecosystem response is complicatedand still under investigation(Shaver et al. 2000), but the role ofwater, particularly in the form ofsoil moisture, is well established ascritical to carbon cycling in theArctic.

Arctic animals have adapted totheir particular niche, and changesin the environment will influenceall creatures. Terrestrial herbivoresmust be able to graze beneath thewinter snowpack. Midwinterwarming or rain events can intro-duce ice layers that prevent caribouand musk oxen from cratering theice-encrusted snow. Similarly, suchice layers can prevent adequatewind pumping of fresh air to smallrodents living under the snow. Thecircumpolar arctic serves as abreeding ground for dozens of spe-cies of waterfowl and other birds(Figure 5-3), and the condition ofthe arctic environment determinesthe size of populations that mi-grate to more temperate winterranges. The timing of their migra-tions and very existence is stronglyaffected by local hydrological con-ditions. Water conveys obviouscontrols on aquatic habitat. Recentwork in the Kuparuk River inAlaska shows an additional, closelinkage between fish productionand river discharge (Figure 5-4).

Marine life in the Arctic is condi-tioned by physical factors includ-ing circulation, temperature, salin-ity, and ice. Changes in thesefactors inevitably affect marineecosystems. For example, cold low-salinity surface water anomaliesoriginating in the Arctic can reducevertical mixing, negatively affecting

Sensible heat flux

Climate warming

Snow trapping

Warmer soils

Soil Nsupply

Litter quality

Shrubgrowth

Soil moisture

TaliksDiscontinuouspermafrost-thermokarst

Active layerfrost penetration

Frost penetrationActive layer

thickness

Summer warming

winter warming(more snow)

Primary production and respiration increase and hydrology changes

Box 5-1. Postulated Land SurfaceHydrology Responses to GreenhouseWarming

The hydrologic response of the arctic land surface to changing cli-mate is dynamically coupled to the region’s surface energy balance,thermal regime, and ecology. The coupling between hydrology andecology takes place primarily through changes in the active layer ofthe permafrost. One likely consequence of climate warming will bethat soil conditions will improve for shrubs, creating both winter(snow holding) and summer (increased nitrogen mineralization)conditions more favorable to shrub growth and dispersion (Sturmet al. 2001). Changes in land surface cover will change the energypartitioning and carbon cycling, thereby affecting both localweather and global climate. At the same time, as suggested by theupper cycle, the climate change will affect the active layer and per-mafrost character. Summer warming, or winter warming with in-creased snow, will have different outcomes, though for large andlong-term changes in climate, they will probably converge. The twocycles are shown linked through soil thermal conditions, but theyare also linked through soil moisture. Both cycles have a direct im-pact on the hydrologic response of the landscape, including waterstorage for subsequent evaporation and runoff (Kane 1997). Thisscenario applies to upland ecosystems. Lowlands and wetlandsmay respond differently.



Figure 5-4. Discharge versus fish production in the Kuparuk River, Alaska. Instream biotic systems are linked closely tothe behavior of river systems, with dependencies on both the physical (scouring, habitat) and chemical (oxygen status,primary production) setting. These dependencies on biotic systems are translated into dependencies on human society,both industrial and indigenous. Above is a plot of the average arctic grayling adult growth and young-of-the-year weightat 40-d versus mean discharge in the reference and fertilized reaches of the Kuparuk River, 1986, 1988–1998 (adultgrowth was not available for 1993). The impact of hydrological processes on biological processes is evident (LindaDeegan, Arctic LTER database).

0

0.5

1

1.5

2

2.5

0 1 2 3 4 5

Ad

ult

Gro

wth

(g/

d)

Reference

Fertilized

0

0.5

1

1.5

2

2.5

3

0 1 2 3 4 5

Age

-0 W

eigh

t

Mean Summer Discharge (m3/s)

Table 5-1: Examples of how observed environmental changes may affect arctic ecosystems. Note that some changes canreverse direction depending on the local context.

CHANGINGPHYSICAL ECOSYSTEM IMPACTSENVIRONMENT Vegetation Wildlife Biogeochemical Trace gas Fire Lakes and

Fluxes Streams

Permafrost thaw Slumping soils Decrease in Increased export of Increasing Drainage Increaseddisrupt trafficability C, N, P and flux to promotes productivity/vegetation sediments atmosphere fire sediment load

Soil moisture Shifts in species Mixed response Increased export CO2 flux Fire frequency If runoff

changes distribution depending if runoff increases increases in and severity increases,upon species drier soils, increases in productivity

methane flux drier soils will increaseincreases inwetter soils

Summer Higher gross Increase in Increased Decomposition Fire frequency Lake trout andtemperature primary insects decomposition leads to and severity grayling growthincrease production and liberates nutrients increases in increase decline

respiration fluxes

Snow cover Shifts in Less insulation Greater winter Fluxes may Increased fire Less springdecline vegetation for rodents. export decrease if input of organic

stature and Predator species soils are colder matter andspecies become more due to lack of nutrients lowers

advantaged insulation productivity

Winter Northward Winter mortality Decomposition Fluxes increase Longer fire Increases intemperature migration of decreases. rates increase season baseflowincrease species, increase Ice layers reduce during winter throughout

in shrubs fresh air to increasing soluble winterrodents nutrients in spring

47

nutrient flows and hence phy-toplankton production on whichmarine food webs—and northernAtlantic commercial fisheries—depend (Gudmundsson 1998,Astthorsson and Gislason 1995,1998, Hamilton and Allanson2001). Marine mammals have aclose dependence on sea ice formobility and access to foodsources.

Arctic Water Cycle Changeand Humans

Environmental change across theArctic influences human societies.Table 5-2 shows some of these“points of contact” between hu-mans and the linked hydrologicalsystem. Industrial enterprises suchas energy development, transporta-tion, or commercial fisheries, and

Table 5-2: Points of contact, and areas of needed research, where changing physical environment parameters are likely toaffect human activities in the Arctic.

CHANGINGPHYSICAL HUMAN DIMENSION IMPACTSENVIRONMENT Infrastructure Transportation Other Economic Subsistence, Health

Activities Traditional Activities

Permafrost Buildings, water Roads, runways Pipelines Overland travel, Water supplies,& power systems subsistence resources waste disposal

Precipitation, Riverbank Roads, navigable Mining & industrial Overland travel, Water-bornerunoff erosion, flooding, waters wastes subsistence resources illness

water supplies

Storms, fog Coastal wave Sea, air Fire prevention Subsistence Accidentserosion hunting & fishing

Snow cover Snow removal Winter travel Water supply Overland travel, Water supplyavalanches subsistence resources

River & sea ice Coastal/riverside Shipping routes Hydropower Subsistence Accidentserosion & season hunting, travel

Summer Foundation Permafrost and ice- Tourism Changes in species Insects, vector-temperature instability road degradation and migration routes borne illness

Sea level Coastal flooding, Shipping facilities Village relocation Coastal cemeteries Freshwatererosion or artifacts salinization

Ocean circulation Harbor siting Shipping Commercial fisheries Subsistence hunting Contaminant& fishing transport

Contaminants Water supply/ Spill prevention Commercial fisheries Subsistence hunting Humantreatment remediation & fishing exposure

more traditional livelihoods andcommunities of the Arctic’s indig-enous peoples, are intimately con-nected to elements of the arctichydrologic cycle. Changes to pre-cipitation quantity and timing,fog, snow, river and sea ice, sealevel, temperature, ocean circula-tion, and contaminants have, andwill continue to affect individuallivelihoods, the viability of settle-ments, and national economicprosperity for many who live inthe Arctic. Precipitation changesassociated with climate warming,such as that which killed thou-sands of reindeer on Svalbard(Aanes et al. 2000), point to thevulnerability of human-managedarctic ecosystems. Changes in per-mafrost could affect thousands ofstructures built on frozenground—including houses, hospi-

tals, pipelines, and community wa-ter systems—well into the future asthe thermal and structural stabilityof soils continues to degrade (Fig-ures 5-5, 5-6, 5-7). While the trueimpact of each of these changesrequires an understanding of thecomplex interactions betweenphysical, biological, and humansystems, current studies are mostlylimited to educated guesswork. Be-cause arctic physical processes aretightly coupled to global processes,shifts in arctic water cycles couldalso have consequences for peoplefar outside the Arctic. As an ex-ample, freshwater from the Arcticbasin is important to global oceancirculation, including the NorthAtlantic Current that moderatesthe climate of northern Europeand perhaps aridity in centralNorth America.



Figure 5-5. Structures can be dramatically affected if the underlying ice-richpermafrost thaws (photo by L. Hinzman).

Figure 5-7. Ice-rich permafrost thaw-ing and surface and groundwater in-tensive flow created this thermokarstpit in a parking lot in Fairbanks,Alaska (photo by V. Romanovsky).

Figure 5-6. The Trans-Alaska Pipeline is designed to keep permafrost frozen bythe use of thermosiphons. Permafrost is warming in interior Alaska, where thispicture was taken (photo by L. Hamilton).

Land-Atmosphere-OceanFeedbacks

Atmospheric circulation patternschange seasonally and have com-plex interactions with ocean circu-lation, sea ice, and land-surface

energy and water fluxes. Amongthese interactions, the link be-tween the atmosphere and snowcover extent is relatively wellestablished. Snow cover influencesthe surface energy budget in winterby insulating the surface and in

spring by recharging rivers. Clark etal. (1999; citing also Thompsonand Wallace 1998) found that theArctic Oscillation (AO) correlateswith Eurasian surface air tempera-tures. Temperatures in turn affectsnow cover. The observed recentdecrease in Northern Hemispherespring/summer snow cover(Groisman et al. 1994) thus likelyreflects large-scale atmosphericevents. Box 5-2 outlines some ofthe evidence linking northernhemisphere snow cover to atmo-spheric dynamics.

In chapter 4, we reviewed evidencefor decadal-scale variability in Arc-tic Ocean ice. Recent data showsignificant losses of sea ice, espe-cially in coastal and marginal seas.Several geophysical phenomena,including ventilation of the ArcticOcean, deep-water formation, oce-anic albedo, roughness, and evapo-ration, are dramatically altered bythe presence or absence of sea ice.Box 5-3 illustrates some of theselinkages.

49

Arctic land-atmosphere-oceanfeedbacks extend far beyondcoastal seas and influence the Arc-tic Ocean as well as other oceansof the world. Recent analysis of pe-riodic atmospheric phenomenasuch as the AO and NAO suggestinterconnections among the majorland, ocean, and atmospheric com-ponents of the larger arctic system(Hilmer and Jung 2000, Morisonet al. 2000). Salinity anomaliesoriginating with freshwater pulsesfrom the Arctic have had oceano-graphic, climatic, and economicconsequences around the northernAtlantic (Malmberg et al. 1999).Such observations give hints abouthow the system is woven togetherand its potential sensitivities to glo-bal change (Box 4-1).

Land-Atmosphere-Ocean-Human Feedbacks

The commercial fisheries of theNorth Atlantic, important eco-nomically to more than a dozennations and as food sources tomany more (Figure 5-8), are im-mediately “downstream” from theArctic Ocean. Often, they havebeen directly affected by the arctichydrologic cycle (see Box 5-4). It ispossible to trace causal links fromarctic winds and precipitation, toarctic and Atlantic oceanographicchanges, to primary biological pro-duction and key fisheries re-sources. The health of these re-sources in turn affects thewell-being of people, enterprises,communities, and even nations.The cold-ocean ecosystems of thenorthern Atlantic support some ofthe most fisheries-dependent soci-eties on Earth. Marine resourcesare critical as well to many arcticand sub-arctic indigenous commu-

Box 5-2. Large-Scale Circulation/Snow Cover Linkages

Interactions between the arctic land mass and overlying atmo-sphere have been found to have an important impact on the devel-opment and sustainability of snow cover and on arctic weather pat-terns. Several studies have shown how the atmosphere affectsEurasian snow cover (e.g., Clark et al. 1999). Other investigationshave emphasized the atmospheric response to snow such as therelationship between anomalous Eurasian snow cover extent andthe strength of the Asian monsoon (e.g., Douville and Royer 1996).Cohen and Entekhabi (1999) showed a statistically significant im-pact of autumn Eurasian snow cover patterns on the strength andspatial coverage of the Siberian high and how that can affect theposition of the Icelandic low, resulting in shifts in the North Atlan-tic-Arctic atmospheric circulation. Large negative (positive) snowextent anomalies that exist in autumn can act as a heating (cool-ing) mechanism through albedo conditions and have an effect onthe following wintertime atmospheric conditions (Watanabe andNitta 1999). Figure is from Arsenault (2000).

AO

Ind

ex

(1972–1997)

Eurasian Snow Covered Area (106 km2)

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

–0.5

–1.0

–1.521 22 23 24 25 26 27

nities, for whom subsistence hunt-ing and fishing provide culturalcontinuity and significant sourcesof food. Water fluxes also regulatethe spread and bioaccumulation ofcontaminants, originating bothfrom northern and more distantsources, in arctic wildlife (AMAP1999). Such contaminants are un-derstandably of great concern to

arctic residents (Figure 5-8). Air-borne transport of pollutants anddeposition through precipitationconstitute a major transboundaryenvironmental issue (Figure 5-9).

Other important land–atmo-sphere–ocean–human connectionslinked through the water cycle af-fect arctic industrial activities and



Box 5-3. Feedbacks Among Sea Ice, Precipitation,River Runoff, and Coastal Oceans

Recent studies indicate the presence of decadal-scale variability in the extent and thickness ofarctic sea ice. Recent trends show decreasing seaice, especially in coastal and marginal seas. Thebox diagram shows some potential land-ocean-ice-atmosphere feedbacks and interactions thatmight occur in such a changing environment.

We start with an assumption of decreasing seaice cover near the coast in response to climatewarming, which would encourage cloud forma-tion and increased precipitation. More open wa-ter fosters a potential biotically mediated posi-tive feedback on clouds through production ofdimethyl sulfide (DMS) by marine phytoplank-ton. DMS then serves as a source of cloud con-densation nuclei. We also note the potential foradditional water vapor advected to the coastalregion from the central Arctic Ocean and/orlower latitude areas. In summer, increased pre-cipitation would create more runoff and thusmore discharge of fresh waters to the coastalocean. A potential negative feedback might thenresult, since all other effects being constant,freshwater tends to stratify the coastal ocean and

Increased Evaporation

Climate ChangeClimate Change

RadiativeFeedbacks?

RadiativeFeedbacks?

Increased Precipitation

Decreased Ice/Increased Open Water

Increased Discharge

Increased Snow &Warmer Permafrost

positive feedbacksnegative feedbacks

Increased Clouds

Heat and Moisture From Lower Latitudes

Increased Evaporation

Increased Biologic Activity

positive/negative??

encourage sea ice growth. (In fact, the annual vol-ume of river discharge to the Arctic Ocean ap-proximately equals the volume of sea ice exportedsouthward through Fram Strait.) However, positivefeedbacks could also occur as the stratified oceanwarms (Macdonald 2000).

The above scenario assumes that the land sur-face is fixed. In reality, increased precipitationmight encourage a warming of the land surface,for example, as the insulating effects of snowcover act to warm permafrost. This might lead toplant community changes, increased evaporationand thus more clouds, more precipitation, andso on. We also note the potential for radiativefeedbacks in this scenario, yet predicting cloudproperties and their specific response to pertur-bation will constitute a major challenge. Animportant caveat is the presence of lateral advec-tion, which would certainly produce a three-dimensional structure that is not captured bythis two-dimensional schematic. The unknownsand uncertainties are many, and the hydrologicalcycle figures prominently in each.

51

Box 5-4. Freshwater Fluxes, Ocean Salinity, and Fisheries

The graph above shows total catches in Icelandicwaters of herring and capelin, 1905 to 1997.Dashed vertical lines show approximate arrivalsof cold, low-salinity arctic water anomalies (GSA’70s and GSA ’80s) off North Iceland. Theseanomalies have strong linkages to the watercycle and affect biological production of impor-tance to humans.

The “Great Salinity Anomaly” (GSA ’70s), alow-salinity surface water mass that circulatedaround the North Atlantic ca. 1968–82, isthought to have originated with a freshwater/seaice pulse from the Arctic via Fram Strait. A sec-ond North Atlantic salinity anomaly (GSA ’80s)that circulated ca. 1982–89 had different origins,forming in the Labrador Sea/Baffin Bay due tosevere winters and possibly arctic freshwater out-flow through the Canadian Archipelago (Belkinet al. 1998). Arctic hydrological factors, includ-ing precipitation and runoff in northernCanada, and the sea-ice extent in the westernArctic Ocean, are thus linked (Power and Mysak1992, cited in Belkin et al. 1998) to a phenom-enon that has been described as “one of themost persistent and extreme variations in globalocean climate yet observed in this century”(Dickson et al. 1988). As they moved for yearsthrough the North Atlantic, both GSAs had ef-fects on marine life, commercial fisheries, andhuman societies.

The seas north of Iceland are characterized byrelatively large variations in temperature andsalinity in comparison with seas to the south.These variations affect phytoplankton produc-tion: a cold, fresh surface layer inhibits verticalmixing, reducing the nutrients available tomaintain the spring phytoplankton blooms(Gudmundsson 1998). Phytoplankton produc-tion controls the biomass of zooplankton, whichin turn provides food for larval cod, capelin, andherring (Astthorsson and Gislason 1995). Thecold, relatively fresh water of GSA ’70s was firstobserved northeast of Iceland in 1965–71, coin-ciding with the collapse of Iceland-waters her-ring catches seen in the graph above (Hamiltonand Allanson 2001). Herring stocks never fullyrecovered from this collapse. In subsequentyears another forage species, capelin, played alarger commercial role. GSA ’80s circulatedthrough North Icelandic waters in 1982, andagain in 1989–90. Both these events were fol-lowed by steep falls in capelin catches.

Onshore in Iceland, fluctuating fisheriescatches translated into economic hardship forindividuals and businesses who count heavily onthese resources. Some employers were forced toshut down and some communities lost inhabit-ants as well as jobs.

Her

rin

g: 1

000s

of

ton

s

Cap

elin

: 1000s

of

ton

s

Herring Capelin

1910 1930 1950 1970 19900

100

200

300

400

500

600

700

0

200

400

600

800

1000

1200

A capelin catch in southeast Iceland (photo by LarryHamilton).



Figure 5-9. Sulfur dioxide and otherpollutants from this smelter in theMurmansk region of Russia havekilled forests in an area more than 40kilometers across and caused measur-able damage well into Norway andFinland (photo by L. Hamilton).

Figure 5-8. Fish are an importantpart of the subsistence diet and thecommercial economy for many arcticpeople. This Native family is harvest-ing salmon on the Arctic Red River inthe Northwest Territories, Canada(photo by L. Hinzman).

settlements. Development andmaintenance of infrastructure inarctic regions is thoroughlyintertwined with permafrost-domi-nated hydrological processes. Fa-cilities built over permafrost re-main stable only so long as thepermafrost remains frozen. A weakunderstanding of hydrologic sci-ence and a warming climate com-bine to make construction andmaintenance of infrastructuretenuous.

Construction of roads or bridgesrequires knowledge of thebiogeophysical characteristics ofthe drainages that must be tra-versed. These include the fre-quency of floods, average high and

low flows, potential for icing, rain-fall distributions, snow loads anddominant drift directions, soilproperties, and vegetation. Formost regions of the Arctic, suchinformation is essentially nonexist-ent. This often leads to costly mis-takes and extensive re-engineering.Construction or removal of road-ways also threatens to damagefragile ecosystems that will requiredecades or centuries to recover.Roads create impoundments ofwater, which if not properlydrained can result in extensivethermokarsting (Figure 5-7). All ofthese issues become especiallyproblematical under rapid envi-ronmental change and highlightthe role of humans in the interact-ing arctic biogeophysical system.

Central Questions: What are the impacts of arctic hydrological changeson ecosystems and humans? How does the hydrologic cycle feed back tothe oceans and atmosphere?

Key Gaps in Current Understanding and Needed Studies:• Synthesis studies coupling atmosphere-land-ocean dynamics• Permafrost impacts on vegetation, biogeochemistry, and trace gas

exchanges• Documentation of changes in the distribution and dynamics of arc-

tic vegetation• Documentation of changes to arctic animal populations, many of

importance to humans• Altered weather and human response• Sensitivity of human infrastructure to permafrost warming and asso-

ciated hydrological change• Synthesis studies embedding human dimension issues into coupled

atmosphere-land-ocean system studies

53

ocean studies, terrestrial andaquatic ecology, and socio-economics. In addition, member-ship should include scientistsactive in executing large-scale syn-thesis studies, specifically, thosedeveloping earth and arctic sys-tems models. A balance betweenprocess-level field researchers,operational monitoring agencyrepresentatives, and simulationmodelers should be sought. Thecharge of AC-SSC will be to set thescience agenda of the overall initia-tive, to coordinate its researchactivities, and to ensure that resultsare disseminated to a broad usercommunity. The AC-SSC shouldcritically assess the initiative’sprogress and scientific relevancy, aswell as provide guidance to NSF-ARCSS on future funding require-ments. To ensure continuity acrossNSF arctic research programs, theAC-SSC should be represented onthe ARCSS Committee.

• The committee recommendsthat an Arctic-CHAMP scienceagenda should be more fullydeveloped through an interdis-ciplinary implementation plan.

A detailed science plan should gobeyond this current document,presenting guidance on the institu-tional structure for Arctic-CHAMP,its governance, a set of specific sci-entific investigations and observa-tional campaigns, and coordina-tion with other NSF, national, andinternational agency efforts. The

implementation plan would beaugmented through annual reportssummarizing progress on Arctic-CHAMP and providing revisedplans for future work. Additionaldocumentation of progress wouldbe provided through, first andforemost, peer-reviewed publica-tions by participating researchers.A newsletter, workshop reports,and a frequently updated web pagewould also help to promote abroad following.

• The committee strongly recom-mends that NSF support a set ofmultidisciplinary, process-based catchment studies.

Through the normal peer reviewprocess, NSF should identify andfund experiments at a core groupof field sites aimed at developing amechanistic view of the hydrologyof the Arctic. Integration of hydrol-ogy, land-atmosphere interaction,biology, and biogeochemical pro-cesses should be a fundamentalfeature of this research. An empha-sis on up-scaling to ensure the rel-evancy of these studies to the fullpan-arctic domain is encouraged.

• The committee recommends animmediate and major effort toimprove our current monitor-ing of water cycle variablesacross the pan-Arctic.

Detecting and interpreting progres-sive changes to the arctic hydro-logic cycle will be impossible with-out a coherent observational

A rctic-CHAMP must beinclusive and struc-tured to enlist a con-tinuing input of new

ideas from the scientific commu-nity at large. The initiative alsorequires a “corporate identity”through which scientists can pro-pose and participate in the moni-toring, modeling, and processstudy components of the initiative.The committee envisions this iden-tity-building to be aided by an Arc-tic-CHAMP steering committee, aninstitutional home for the pro-gram, research plans, and a work-shop series. A successful Arctic-CHAMP should complement,contribute to, and draw from otherimportant NSF, federal agency, andinternational arctic initiatives.These issues are articulated as a setof specific recommendations toNSF, mapped to the scientific andtechnical requirements of Arctic-CHAMP identified throughout ear-lier portions of this report (Box 6-1).

• This committee recommendsthat an Arctic-CHAMP ScientificSteering Committee (AC-SSC)be formed to catalyze concep-tual development of Arctic-CHAMP and to provide ongo-ing supervision of itsexecution.

The AC-SSC should constitute aninterdisciplinary advisory board,with representatives from the fieldsof land surface hydrology, atmo-spheric dynamics, sea ice and

Implementation of Arctic-CHAMP6

6. Implementation of Arctic-CHAMP


strategy. This requires immediateattention as well as long-term vigi-lance. NSF should invest in an ex-panded, hydrologically orientedmonitoring program across thepan-Arctic, coordinating, as re-quired, with U.S. and internationalagency partners. Enhancing ourcurrent capacity will involve datarescue, expansion of current obser-vational networks, and develop-ment of new technologies forharsh weather instrumentation. Itshould also foster development ofnew interpolation and remotesensing techniques to achieve pan-arctic coverage at high spatial andtemporal resolutions.

• This committee recommendscreation of an Arctic-CHAMPSynthesis and Education Center(CSEC) to serve as the institu-tional focal point for the initia-tive, open to the entire commu-nity of arctic researchers.

We recommend NSF create a cen-tral facility to catalyze ongoingsynthesis studies of pan-arctic hy-drology. Arctic-CHAMP synthesismodels would be developed atCSEC. The center should lead thecoordination of modeling, fieldresearch, and monitoring effortswithin Arctic-CHAMP. Each devel-opmental version of the Arctic-CHAMP models would reside atCSEC, but when sufficiently ma-ture, distributed to the broader re-search community. In coordina-tion with the National Snow andIce Data Center (Boulder, Colo-rado), CSEC would produce a con-tinually evolving Arctic-CHAMPHydrometeorological Data Archive(HDA) for station-based monitor-ing data and value-added projectoutputs emerging from the synthe-sis work. Arctic-CHAMP science

Box 6-1. Arctic-CHAMP Scientificand Technical Needs

Several specific research needs aimed at improving our current un-derstanding of the arctic water cycle and its sensitivity to changewere identified throughout the text, setting the scientific stage forArctic-CHAMP. In response to the integrative nature of the arcticwater cycle, these issues will need to be addressed in a systematicand comprehensive fashion. A synthetic view of the entire pan-arc-tic hydrologic system, based on focused process, feedback, andsensitivity studies, will be critical to ensure the necessary transferof knowledge between fine and large scale studies and betweencampaigns dedicated to observation and process understanding.Specific activities that are required to develop such an integratedview of the entire pan-arctic system include:• maintenance of existing and establishment of new, long-term,

and coherent monitoring programs for key hydrological and bio-geochemical variables, including both water itself and the con-stituents it supports;

• enhancement of the current generation of field programs to sup-port process-based understanding of arctic hydrology;

• development of methods to bridge the gap between process-levelstudies, point-scale monitoring, and the hydrodynamics of thepan-Arctic through combined field-based measurements, remotesensing, and modeling;

• design of a strategy to achieve synthesis and water budget clo-sure over the full water cycle, encompassing interactions acrossatmospheric, land surface, and oceanic components with links tothe larger earth system;

• determination of the links between water-related changes, eco-system dynamics, biogeochemical cycling, and trace gas emissionwhich feed back to the hydrologic cycle and climate system;

• assessment of the vulnerability of humans to arctic water cyclechanges;

• full-system feedback and sensitivity studies, including humansystems, in response to global change; and

• implementation of a viable administrative structure and mecha-nism to promote full pan-arctic system integration.A more exhaustive listing of recommended actions representing

the views of a broad cross-section of the arctic science communityis presented in a collection of position papers (Hinzman andVörösmarty 2001). Appendix 2 offers a summary listing of theseissues.

55

activities will serve as an importantapplication of state-of-the-art tech-nologies and should be coordi-nated with relevant activities of theNSF Information Technology Re-search Program.

Researchers and their students andpost-docs would be chosen througha competitive fellowship programattracting the most highly quali-fied applicants. CSEC would bringtogether observationalists, process-level scientists, and modelers in acollaborative physical setting toshare insight and to cross-fertilizeideas. Research would be per-formed by graduate students andpost-doctoral fellows on site, butsupervised by contributing re-searchers from several parent insti-tutions. A useful model for CSECis that of the NCEAS (NationalCenter for Ecological Analysis andSynthesis in Santa Barbara, Califor-nia). To inform the public of theneed to study the otherwise distantArctic and its role in environmen-tal change, direct links to the NSFInteragency Education ResearchInitiative are advised. A vigorousK-12 effort could be mountedthrough the CSEC.

• This committee recommendsthat funding be committed toan Arctic-CHAMP WorkshopSeries and Open Science Meet-ings to provide ongoing intel-lectual support for the overallinitiative.

Arctic-CHAMP would serve as anexcellent focal point for workinggroups seeking to execute fieldprograms, create and implementcommunity-based models, and in-terpret specific observational datasets. A major initial effort shouldbe directed toward understanding

the changing contemporary condi-tion of the pan-arctic water cycle.Other workshops in the seriescould focus on historical/paleoand future settings. Biogeophysicaland human dimension issuesshould be jointly addressed. Peri-odic Open Science Meetingsshould also be convened to solicitinput from the broader researchcommunity.

• The success of Arctic-CHAMPwill depend on a purposefulintegration across other pro-grammatic elements of the Na-tional Science Foundation andallied federal agencies, and thecommittee strongly advises thatsteps be implemented to fosterthis collaboration.

A primary goal of the current NSF-ARCSS Program (Box 6-2) is topromote an understanding of theimpacts of global change on thephysical, biological, and humanresources of the Arctic (ARCUS1998). The issue of feedbacksacross the pan-Arctic is an impor-tant emphasis of the future ARCSSProgram and thus integrates wellwith the concept of an Arctic-CHAMP. This interdisciplinary per-spective is driven not only by sci-entific curiosity but as well by theneeds of the policy community,which seeks response strategies toimpending climate change thattranscend the domains of tradi-tional disciplines (e.g., U.S. Na-tional Assessment 2000).

By their very nature, multiagencyefforts such as the U.S. NationalAssessment and SEARCH wouldserve as important sources of infor-mation and would be served, inturn, by the unique set of hydro-logically oriented results emerging

from Arctic-CHAMP. As a good ex-ample, remote sensing for freeze-thaw dynamics, envisioned as aNASA post-2002 mission (Cline etal. 1999), would provide an enor-mously important data set for hy-drological studies across the entirepan-Arctic. Coordination with Arc-tic-CHAMP field studies could pro-vide critical ground-truth, whileArctic-CHAMP simulation studieswould constitute an immediatehydrological application for thissatellite system. Arctic-CHAMPstudies on biological and bio-geochemical feedbacks in responseto global change would directlysupport the central scientific con-cerns of the NSF BiocomplexityProgram. A coordination is clearlyneeded to avoid duplication of ef-fort and to optimize the use of fed-eral research dollars. Appendix 3lists several specific opportunitiesfor collaboration within the U.S.Arctic research community.

• There are several ideal opportu-nities for international collabo-ration in arctic hydrologicalresearch. The committee urgesan active linkage of these ongo-ing programs with Arctic-CHAMP.

Arctic-CHAMP’s treatment ofcoupled water dynamics across theentire pan-Arctic will enlist the in-terest and involvement of the in-ternational research community.There are several well-establishedexperimental, monitoring, andanalysis programs in place to whichArctic-CHAMP should be linked,with the aim of providing synergis-tic benefits not otherwise achiev-able through each individual ef-fort. These involve significantongoing as well as new initiativesorganized around scientific and



monitoring activities. Box 6-3 sum-marizes several noteworthy efforts.Among these are major arctic fieldcampaigns over a variety of spatialscales, routine environmentalmonitoring, intercomparisonmodeling studies, remote sensing,numerical weather prediction andreanalysis, data archiving activities,and policy-relevant assessments.Bilateral agreements involving theU.S. and other arctic scientific part-ners should be fostered, in particu-lar with Russia to help sustain itsscientific infrastructure and humanresources.

• The Arctic, as a harbinger ofglobal climate change, will con-tinue to be an important focalpoint for ongoing research andinternational policy formula-tion. It is recommended that apolicy arm of Arctic-CHAMPbe established to disseminatescientific findings to the envi-ronmental managementcommunity.

It is noteworthy that ongoing IPCCassessments include a polarregional analysis, due to the manyyears of research indicating a highsensitivity of the Arctic to green-house warming. Integrative, pan-arctic understanding of hydrologicinteractions and feedbacks in

Box 6-2. NSF ARCSS Program Elements

As a consequence of its ambitious mandate, ARCSS has been orga-nized into a series of more manageable programmatic components:

• Land-Atmosphere-Ice Interactions (LAII);• Ocean-Atmosphere-Ice Interactions (OAII);• Paleoenvironmental Studies (Greenland Ice Sheet Project

Two [GISP2], Paleoclimates from Arctic Lakes and Estuaries[PALE]), both part of Paleoenvironmental Arctic Sciences(PARCS);

• Human Dimensions of the Arctic System (HARC); and• Russian-American Initiative on Shelf-Land Environments

(RAISE).The LAII Flux Study in Alaska, North American Tundra Experi-

ment (NATEX), Arctic Transitions in the Land-Atmosphere System(ATLAS) program, and U.S. contributions to the International Tun-dra Experiment (ITEX) provide important observational compo-nents to the overall ARCSS effort. These studies have supported abroad array of observational programs, process-based studies,modeling efforts, and environmental assessments. Several havebeen high profile and highly successful (e.g., Greenland Ice SheetProject, SHEBA), both scientifically and in raising public aware-ness of the importance of the Arctic in global change. While theseprograms provide important new science, synthesis across theseefforts has yet to be achieved. Integration and synthesis is empha-sized as part of the new ARCSS research agenda.

response to global change—of thetype envisioned for Arctic-CHAMP—provides critical scien-tific support to U.N. FrameworkConvention activities. The interna-tional diplomacy issues associatedwith arctic system change are enor-mous. The contributions of Arctic-

CHAMP toward articulating thediverse physical, biological, andhuman vulnerabilities to thischange provide an important im-petus for international cooperationin wisely managing this critical partof the arctic and earth systems.

57

Box 6-3. International Programs Sharing the Scientific, Obser-vational, and Policy-Oriented Objectives of Arctic-CHAMP

Several opportunities are apparent for mutually beneficial collaboration, taking advantage of existinginfrastructure and ongoing investment in these programs. The listing below shows some major repre-sentative programs and is not meant to be exhaustive.

INTERNATIONAL PROGRAM PRIMARY GOALS/ACTIVITIESMajor International Science Initiatives

1. World Meteorological Organization’s World Climate Research Program (WMO/WCRP)

(a) Global Water and Energy Experiment Coupling studies of land-atmosphere for regional and(GEWEX) global modeling; Continental-Scale Experiments (CSE’s)

include Baltic Sea (BALTEX), Mackenzie GEWEX Study(MAGS), GEWEX Asian Monsoon Experiment (GAME) forLena River; organizing major Coordinated Enhanced Ob-servation Period (CEOP) for 2001–02.

(b) Climate Variability and Predictability Understanding climate variability on a months-to-Study (CLIVAR) decades time frame.

(c) Climate and Cryosphere (CliC) Broad set of cryosphere/atmosphere interactions (snow,ice, land, sea ice, oceans); Arctic as harbinger of globalchange; strong monitoring component including WMOmeteorology and hydrology networks; follow-on to exist-ing Arctic Climate System Study (ACSYS).

2. International Geosphere-Biosphere Program and Subsidiary Program (IGBP) Elements

(a) Past Global Changes (PAGES) Response of earth system to change over numerous timedomains including rapid climatic shifts; analysis of seaice, salinity, thermohaline circulation under current ver-sus glacial maximum conditions, paleoclimatic recon-structions along Pole-Equator-Pole (PEP) transects;paleoclimate modeling including dynamic vegetation;human dimension issues during the Holocene.

(b) Task Force of Global Analysis, Development of linked models of the completeInterpretation, and Modeling (GAIM) earth system, integrating dynamic atmosphere, ocean,

biosphere, and biogeochemical models; feedback studiesand system sensitivity to global change.

(c) Biospheric Aspects of the Hydrological Enhancements of land surface-atmosphere transferCycle (BAHC) schemes; design and execution of large-scale field experi-

ments; monitoring of carbon, water and energy fluxes atinstrumented sites; constituent transport across drainagebasins; dynamic vegetation and its role in regulating cli-mate.

(d) International Global Atmospheric Biosphere-atmosphere exchanges of trace gases,Chemistry (IGAC) including arctic wetlands; development of new gas emis-

sion instrumentation.



Intercomparison Studies

(a) GEWEX/ACSYS Project for Inter- Improve arctic land surface transfer schemes throughcomparison of Land Surface multiyear, spatial comparisons of participating modelParameterization Schemes (PILPS-2e) results; explore alternative treatments of snowpack, soil,

permafrost, frozen lake, wetland dynamics.

(b) International Association of Hydrological Improve understanding of snow/hydrology process-levelSciences Snow Model Intercomparison linkages.Project (SNOWMIP)

(c) WMO Commission for Instruments and Correction of well-known biases in precipitationMethods of Observation: Solid measurements.Precipitation MeasurementIntercomparison

(d) IGBP Paleo-Model Intercomparison Assess relative performance of models contrasting glacialProject (PMIP) maximum (20K years before present) to Holocene

altithermal (6K bp).

(e) European Ice Sheet Modeling Initiative Test, compare, improve upon numerical ice-sheet, ice-(EISMINT) shelf, and glacier models.

(f) ACSYS Sea Ice Model Intercomparison Improve understanding of freshwater dynamicsProject (SIMIP) associated with growth, transport, and decay of Arctic

Ocean sea ice.

(g) Arctic Ocean Model Intercomparison Understand processes influencing Arctic Ocean climateProject (AOMIP) of ACSYS-CliC and how to best represent and forecast these in numeri-

cal models.

Existing Field/Process Study Sites(a) U.S. and International Long-Term Two LTER sites with integrated research, intensive

Ecological Research Network monitoring, and experimentation. Two other sites(LTER/ILTER) beginning to develop long-term and integrated research.

(b) International Tundra Experiment (ITEX) MAB-NSN initiative (Man-And-the-Biosphere, NorthernSciences Network); provides systematic meteorologicalstation data, monitoring of permafrost in collaborationwith IPA, snow cover and lake ice data, and analysis ofpermanent plot studies.

(c) Northern Hemisphere Climate-Processes Long-term catchment studies, soil-plant-atmosphereLand-Surface Experiment (NOPEX) monitoring, regional climate surveys, use of remote sens-

ing for data inputs to models, development of cold-weather measurement techniques.

(d) BOREAS Major U.S.-Canadian initiative to developimprovements in understanding of land surface-atmo-sphere exchanges of energy, water, carbon, and other bio-geochemical fluxes, including trace gases; bulk of fieldeffort ended in mid-1990s, analysis continues.

Remote Sensing

(a) Glacier Inventory of the Commission on Based on Landsat-7 data, provides benchmarks forGlaciation, International Union for future change in freshwater stocks trapped on landQuaternary Research (INQUA) as “permanent” ice.

INTERNATIONAL PROGRAM PRIMARY GOALS/ACTIVITIES

59

(b) Cryosphere System Program (CRYSYS) Develop methods to extract and use cryospheric(Canadian contribution to NASA Earth information from satellite and more conventionalObserving System) data sources.

(c) European Space Agency (ESA) Synthetic Provide altimetry for monitoring changes inAperature Radars on ERS-1 and ERS-2 glacial ice mass.

(d) ESA’s CryoSat Set for launch in 2003, will fly a radar altimeter to moni-tor ice sheets and marine ice.

(e) Canada’s RADARSAT Provide synthetic aperature radar (SAR) imagery withhigh resolutions, from 8 to 100 m; backscattering holdspotential for mapping freeze-thaw of surface active layer.

Monitoring and Analysis Programs

(a) Global Climate Observing System (GCOS)/ Multiorganizational (WMO/UNESCO/UNEP/ICSU)Global Terrestrial Observing System (GTOS) operational framework for systematic change detection;

GCOS Surface Network (GSN) would serve as a globalreference network of land surface observational weather/climate stations; Global Terrestrial Networks (GTN)would include measurements of high relevance to north-ern polar region including glacier inventories (GTNet-G),hyrology (GTN-H), permafrost (GTNet-P).

(b) World Glacier Monitoring Service Glacier monitoring providing inventories of glacier num-bers, areal extent and in some cases glacier mass balance.

(c) International Permafrost Association Site-specific time series and pan-arctic mapping of(IPA) permafrost; two international programs constitute IPA

observational activities: the Circumpolar Active-LayerMonitoring (CALM) and Permafrost and Climate in Eu-rope (PACE); NSIDC holds the IPA Circumpolar Active-Layer Permafrost System (CAPS) CD-ROM.

(d) Arctic Paleo-River Discharge (APARD) Multi-disciplinary analysis of modern and ancientcircumarctic river discharge, initiated by the Arctic OceanSciences Board (AOSB).

Numerical Weather Prediction and Reanalysis

(a) European Center for Medium-range Forthcoming ECMWF ERA-40 global reanalysis will provideWeather Forecasting (ECMWF) and long time series (1957–present) of atmospheric variablesNational Center for Environmental at 60-km resolution and six-hourly time steps; precipita-Prediction (NCEP) tion, evaporation, net vapor convergence, winds, radia-

tion fluxes, and clouds will be routinely computed; U.S.reanalysis efforts (1948–present) established under NCEP.

(b) ACSYS Panel on Polar Products from Activities to support use of weather predictionReanalysis Working Group on Coupled and atmospheric reanalysis models with arcticModels Numerical Experimentation focus; under WCRP auspices.Group (ACSYS NEG)

Data Archives

(a) National Snow and Ice Data Center Clearinghouse for a broad array of data sets supporting(NSIDC) polar and high-latitude studies, including historical sta-

tion time series and remote sensing data sets, several




directly linked to the arctic hydrologic cycle (e.g., precipi-tation, snow cover, sea ice extent); serves as NSF-ARCSS,NASA, and ISCU data center for arctic geophysical dataproducts.

(b) Arctic Precipitation Data Archive (APDA) ACSYS product from WMO Global Precipitation Clima-tology Center (GPCC).

(c) ACSYS Data and Information Service Metadata directory of historical or newly available arctic(ADIS) data sets.

(e) Global Observing Systems Information Data clearinghouse for GCOS/GTOS/GOOS databases.Center (GOSIC)

(f) Arctic Environmental Data Directory Metadata system; archive nodes at USGS offices in(AEDD) Anchorage, UNEP GRID (Arendal, Norway), Russian Min-

istry of Environment Protection and Natural Resources(Moscow).

(g) Global Runoff Data Center (GRDC) Archive of Arctic River Database (ARDB) housed inWMO-GRDC, Federal Institute of Hydrology, Koblenz,Germany.

(h) Pan-Arctic Hydrographic Data Base Compendium of time series of runoff and discharge data(R-ArcticNET) across pan-arctic domain, conjoining USGS, Russian

State Hydrological Institute (SHI), Environment Canadadata; a collaboration of the University of New Hampshireand SHI; distributed by NSIDC.

Framework Convention on Climate Change

(a) Working Group 1 (Science of Quantitative documentation of progressive environ-Climate Change) mental changes due to greenhouse warming; Arctic recog-

nized as highly sensitive to global climate change; obser-vational support from GCOS/GTOS.

(b) Working Group 2 (Impacts, Adaptations, Studies of biogeophysical changes and policy-relevantMitigation) human dimensions issues.

Other Arctic Assessment Programs

(a) Arctic Monitoring and Assessment International program case as broad assessment ofProgram (AMAP) contaminant pollution across the pan-arctic, with consid-

eration of associated impacts.

(b) Arctic Climate and Impact Evaluation and synthesis of climate variability, change,Assessment (ACIA) and UV radiation increases; contributes an arctic perspec-

tive to IPCC, established under the Arctic Council.

(c) Northern Research Basins (NRB) Symposium convened every two years to share researchresults from studies in watersheds dominated by snow,ice, and permafrost.


61

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References

71

Appendix 1NSF-ARCSS Arctic Hydrology

Workshop ParticipantsNational Center for Ecological Analysis and Synthesis,

Santa Barbara, California, 18–20 September 2000

John ChristensenBigelow Laboratory for

Ocean Sciences180 McKown PointWest Boothbay, ME 04575Tel.: (207) 633-9601Fax: (207) [email protected]

Andrew FountainPortland State UniversityDepts. Geology and Geography17 Cramer Hall,

1721 SW BroadwayPortland, OR 97201Tel.: (503) 725-3386Fax: (503) [email protected]

Steve FrolkingUniversity of New HampshireComplex Systems Research Center39 College Road, Morse HallDurham, NH 03824-3525Tel.: (603) 862-0244Fax: (603) [email protected]

Barry GoodisonEnvironment CanadaAES-Climate Research Branch4905 Dufferin StreetDownsview, ON M3H 5T4 CanadaTel.: (416) 739-4345Fax: (416) [email protected]

Pavel GroismanUniversity of Massachusetts at

AmherstDept. of GeosciencesMorrill Science Cntr, Box 35820Amherst, MA 01003Tel.: (413) 545-9573Fax: (413) [email protected]

William GutowskiIowa State UniversityDept. of Geological and

Atmospheric Sciences3021 AgronomyAmes, IA 50011-1010Tel.: (515) 294-5632Fax: (515) 294-2619/[email protected]

Lawrence HamiltonUniversity of New HampshireDept. of Sociology20 College RoadDurham, NH 03824-3509Tel.: (603) 862-1859Fax: (630) [email protected]

Larry HinzmanUniversity of Alaska FairbanksWater and Environmental

Research CenterPO Box 755860Fairbanks, AK 99775-5860Tel.: (907) 474-7331Fax: (907) [email protected]

Carl BøggildGeological Survey of Denmark and

GreenlandDept. of Hydrology and GlaciologyThoravej 8Copenhagen NVDK-2400 DenmarkTel.: 45 38 14 27 94Fax: 45 38 14 20 [email protected]

David BromwichThe Ohio State UniversityPolar Meteorology Group

Byrd Polar Research Center1090 Carmack RoadColumbus, OH 43210Tel.: (614) 292-6692Fax: (614) [email protected]

David BrooksTexas A&M UniversityOceanography/College of

GeosciencesCollege Station, TX 77843-3148Tel.: (409) 845-3651Fax: (409) [email protected]

F. Stuart Chapin IIIUniversity of Alaska FairbanksInstitute of Arctic BiologyPO Box 757000Fairbanks, AK 99775-7000Tel.: (907) 474-7922Fax: (907) [email protected]

Appendix 1. Workshop Participants


Doug KaneUniversity of Alaska FairbanksWater and Environmental

Research CenterPO Box 755900Fairbanks, AK 99775-5860Tel.: (907) 474-7808Fax: (907) [email protected]

Yuji KodamaInstitute of Low Temperature

ScienceHokkaido UniversitySapporo 060-0819 JapanTel./Fax: [email protected]

Richard LammersUniversity of New HampshireInstitute for the Study of Earth,

Oceans, and SpaceWater Systems Analysis Group39 College Road, Morse HallDurham, NH 03824-3525Tel.: (603) 862-4699Fax: (603) [email protected]

Dennis LettenmaierUniversity of WashingtonCivil and Environmental

Engineering164 Wilcox Hall, Box 352700Seattle, WA 98195-5270Tel.: (206) 685-1024Fax: (206) [email protected]

Glen ListonColorado State UniversityDept. of Atmospheric ScienceFort Collins, CO 80523-1371Tel.: (970) 491-8220Fax: (970) [email protected]

Wieslaw MaslowskiNaval Postgraduate SchoolDept. of Oceanography—Code

OC/Ma833 Dyer Road, Room 331Monterey, CA 93943-5122Tel.: (831) 656-3162Fax: (831) [email protected]

James McNamaraBoise State UniversityGeoscience Dept.Mail Stop 1535Boise, ID 83725Tel.: (208) 426-1354Fax: (208) [email protected]

James MorisonUniversity of WashingtonPolar Science Center - Applied

Physics Laboratory1013 NE 40th StreetSeattle, WA 98105-6698Tel.: (206) 543-1394Fax: (206) [email protected]

Frederick NelsonUniversity of DelawareDepartment of Geography216 Pearson HallNewark, DE 19716Tel.: (302) 831-0852Fax: (302) [email protected]

Bruce PetersonMarine Biological LaboratoryThe Ecosystems Center7 MBL StreetWoods Hole, MA 02543Tel.: (508) 289-7484Fax: (508) [email protected]

Terry ProwseEnvironment CanadaNational Water Research Institute11 Innovation BoulevardSaskatoon, SK S7N 3H5CanadaTel.: (306) 975-5737Fax: (306) [email protected]

Alan RobockRutgers UniversityDept. of Environmental Sciences14 College Farm RoadNew Brunswick, NJ 08901-8551Tel.: (732) 932-9478Fax: (732) [email protected]

Vladimir RomanovskyUniversity of Alaska FairbanksGeophysical InstitutePO Box 750109Fairbanks, AK 99755-0109Tel.: (907) 474-7459Fax: (907) [email protected]

Mark SerrezeUniversity of Colorado at BoulderCoop. Inst. for Research

in Env. Sci.Div. of Cryospheric and Polar

ProcessesCampus Box 216Boulder, CO 80309-0216Tel.: (303) 492-2963Fax: (303) [email protected]

Michael SteelePolar Science CenterApplied Physics Laboratory1013 NE 40th StreetSeattle, WA 98105Tel.: (206) 543-6586Fax: (206) [email protected]

Marc StieglitzColumbia UniversityLamont-Doherty Earth

ObservatoryRoute 9WPalisades, NY 10964Tel.: (914) 365-8342Fax: (914) [email protected]

Matthew SturmCold Regions Research and

Engineering LaboratoryPO Box 35170Ft. Wainwright, AK 99703-0170Tel.: (907) 353-5183Fax: (907) [email protected]

James SyvitskiUniversity of ColoradoInstitute of Arctic and Alpine

ResearchCampus Box 450Boulder, CO 80309-0450Tel.: (303) 492-7909Fax: (303) [email protected]

73

Charles VörösmartyUniversity of New HampshireWater Systems Analysis Group39 College Road, Morse HallDurham, NH 03824-3525Tel.: (603) 862-0850Fax: (603) [email protected]

Robert WebbNOAA/OAR/CDC325 BroadwayBoulder, CO 80303Tel.: (303) 497-6967Fax: (303) [email protected]

Cort WillmottUniversity of DelawareGeography Department216 Pearson HallNewark, DE 19716Tel.: (302) 831-2292Fax: (302) [email protected]

Appendix 1. Workshop Participants

75

Appendix 2Current Gaps in Understanding the

Pan-Arctic Hydrological Cycle• What determines the regional

and temporal distribution ofsnow trends? Is it tied to the AO?

• How important is lateral transferof heat during snowmelt?

• What are the mechanisms of veg-etation-snow feedback?

• What is the role of vegetation inwater budgets and how does itvary in space and time?

• What is the affect of boreal for-ests on pan-arctic hydrologicprocesses?

• Is there widespread drying of soiland ponds across the pan-Arcticin response to regional warmingtrends, and if so what is its im-pact on resident ecosystems?

• What is the distribution and im-portance of rock glaciers androck fields as a source of latesummer arctic discharge?

• What controls basin morphologyin watersheds underlain by per-mafrost and how will it changewith a warming climate?

• How does the fact that sedimentis immobile (frozen) at the timeof maximum stream power affectthe sediment load in arctic rivers?

• What are the pathways of sedi-ment discharged into the conti-nental shelves by the arctic riversand is the variability of this sedi-ment delivery large enough to berepresented in paleorecords?

• What is the timing and magni-tude of sediment, carbon, andnutrient loads from hillslopes tolarge rivers and what is the effec-tive constituent discharge of ice-affected rivers?

• How will sediment and otherconstituent discharges change aspermafrost distribution respondsto climate warming?

• What are the controls on thetransfer of nutrients and organicmatter from soils to streamsacross the pan-Arctic?

Technical Needs and Uncertainties• Study energy, water, and carbon

cycles as a linked system.• Develop methods to quantify

historic levels of soil moisture.• Quantify the cumulative impacts

of industrial and civil develop-ment on hydrologic systems.

• Improve understanding of waterstorage and subsurface flow pro-cesses in discontinuous perma-frost and mountainous regions.

• Improve understanding of thesurface heat and mass transferprocesses in mountain regions.

• Better define the role of geomet-ric patterns of permafrost degra-dation and its ecological and hy-drological consequences.

• Develop better understanding ofhydraulic routing through

The listing below was drawn fromthe set of key, unresolved scientificand technical issues that were so-licited from participants of theNSF-ARCSS Arctic HydrologyWorkshop, held at the NationalCenter for Ecological Analysis andSynthesis, Santa Barbara, Califor-nia, in September 2000. This list-ing is organized by the major do-mains over which the water cycleplays an integrative role: land,oceans, atmosphere, society (seeFigures 1-1, 1-3, 2-1, 2-2). A subsetof these issues has been identifiedand further articulated in the mainbody of this report.

Land SystemsScientific Questions• What would be the river re-

sponse to extreme Holocene cli-matic events?

• How is spring meltwater parti-tioned into infiltration and run-off?

• What is the relative role of soilmoisture dynamics in relation toother hydrological processes?

• What is the role of wind-pump-ing convection in arctic depthhoar and what is the importanceof hard slab and snow dune for-mation processes?

Appendix 2. Current Gaps in Understanding the Pan-Arctic Hydrological Cycle


glaciers; models of glacier runoffneed better depiction of waterdynamics at the base of theglaciers.

• Improve understanding ofgroundwater fluxes, includingdynamics during winter.

• Sublimation needs better quanti-fication.

• Methods need to be developedfor improved mid-winter dis-charge measurements in high-latitude rivers.

• Wind-blown flux of snow and itsredistribution is a critical un-known.

• Winter wind speed and directionoften unreliable due to riming/icing of sensors; improved tech-nology is required.

• Reliable methods to provideelectrical power to remoteweather stations need to be de-veloped.

• Stratigraphy is hard to measurewidely but determines criticalbulk thermal and physical prop-erties of arctic soils.

• Accurate and widespread mea-surement of winter precipitationnot yet achieved.

• Improve upon the quality anddocumentation of observingtechniques for making precipita-tion measurements.

• Link NSF arctic hydrological ini-tiatives more closely to GEWEX/Mags, Crysys/ACSYS/CLiC.

Data Needs• Quantify paleoclimatic forcing

fields.• Requirement for long-term ob-

servations of soil moisture at sta-tions with climate data.

• Need for time series of dischargealong the Arctic Coast that isocean model-ready (including

gauged and ungauged, chemistry,pollutants, sediments and heat).

• Accurate digital elevation modelsand vegetation maps necessaryfor hydrological studies.

• Thermal and hydraulic proper-ties of frozen soils need to besampled more systematically.

• Critical need for permafrost tem-peratures and distribution, in-cluding active zone dynamics.

• Measure the spatial and tempo-ral variation of P-E around theArctic.

• Develop and apply standardmethods of precipitation mea-surement and correction.

• Fully quantify and map currentglacier-covered areas to providebaseline for change.

• Need more arctic glacier massbalance measurements.

• Data rescue of hydrology obser-vations from former USSR.

• Assessment of hydrometeoro-logical data across national andother administrative borders isnecessary due to wide array ofsampling equipment.

• Need streamflow from a widerange of watershed scales.

• Snow cover depth maps derivedfrom remote sensing or meteoro-logical inputs need to be harmo-nized and cross-validated.

• Conventional networks are un-der severe cost pressures and au-tomation leads to loss of keydata and data degradation.

• Develop baseline data set ofchemical (nutrient, sediment,contaminant, tracer) flux fromall rivers in the Arctic Basin.

Scaling-Related Issues• Do processes in the headwater

basins really matter when mod-eling large basins and regions?

• New methods are necessary toscale hydrologic fluxes across ba-sin sizes, from smallest headwa-ters to scale of the pan-Arctic.

• Improved techniques are neededto rescale hydrologic processesfrom points to GCM domains.

• Creation of gridded data sets byinterpolation of sparse dataacross space and time requiresadditional attention.

Modeling and Related Analysis• Need extensive soil moisture

modeling over cold regions.• Need improved methods for re-

motely sensing soil moistureover large areas.

• Snow sub-grid distribution varia-tions by modeling or remotesensing remains a need.

• Spatial variation of snow coverinsulation and density (snowwater equivalent) is currentlypoorly articulated.

• Validation of model outputs ofsnow cover, snow water equiva-lent, snow depth, and precipita-tion is required.

• Develop and verify models ofmass transport from ungaugedwatersheds for water, nutrients,and sediment.

• Compare regional water bal-ances across Siberian, NorthAmerican, and Northern Eu-ropean domains.

• Improve representation of per-mafrost in regional and globalclimate and hydrologicalmodels.

• Improve compatibility of in situmeasurements, remotely sensed,and modeled data.

• Need for model intercomparisonfrom local to pan-arctic scale.

77

Ocean SystemsScientific Questions• What was the timing and extent

of the Eurasian ice sheet and itsimpact on the coasts and ocean?

• How do terrestrial ecosystemdynamics affect freshwater fluxesto oceans?

• What are the processes and ef-fects of stamuhki: runoff overand under fast ice?

Data Issues• Develop time series of sea level

measurements around the ArcticBasin.

• Quantify biogeochemistry andprimary productivity in estuariesand shelf regions.

• Document exchange in marginalseas, mixing and vertical fluxesassociated with freshwater.

• Measurement of sea ice.• Measurement of snow thermal,

optical hydraulic properties.• Develop improved methods for

incorporating sediment-tracerstudies in oceanographical stud-ies depicting the fate offreshwater.

Modeling Issues• Develop models of near-shore

and estuarine exchanges of waterand constituents.

• Further current understanding ofthe partitioning of freshwaterinto sea ice and sea water as afunction of space and time.

• Develop fully coupled freshwa-ter-sea ice-atmosphere simula-tions.

Atmospheric SystemsScientific Questions• What is the moisture flux con-

vergence between Greenland andScandinavia?

• What is the spatial and temporalvariability of precipitation minusevaporation (P-E) over arcticland mass and ocean?

• Which factors control summercirculation regime near westernSiberia?

• How does global warming forc-ing invoke feedbacks from thepan-arctic system and from thearctic water cycle?

• How does the atmosphericboundary layer respond to snowmelt?

Data Issues• Improve rawinsonde network in

Eurasia and Canada.• Secure agreements to work with

numerical weather predictionmodelers to jointly process pan-arctic data sets.

Modeling Issues• Develop coupled, fully interac-

tive arctic process models thatinclude vegetation and how itinteracts with the land surfaceand the atmosphere.

• Develop subgrid land surfaceprocess representations, withtests to determine which onesare important.

• Improve representation of per-mafrost in regional and globalclimate and hydrologicalmodels.

Human SystemsKey Issues• Identify parameters, locations,

and activities where we expectthat human activities in the Arc-tic demonstrate most sensitivityto hydrological change.

• Conduct empirical studies ofhow observed hydrological varia-tions affect human settlementsand activities in the Arctic.

• Integrate findings from the twosteps above with physical scienceresults to project future humanimpacts of likely hydrologicalchanges.

Appendix 2. Current Gaps in Understanding the Pan-Arctic Hydrological Cycle

79

Appendix 3Integration of

Arctic-CHAMP with NSF and OtherFederal Agency Initiatives

earth system. At the heart of SIMSis a recognition of the importanceof analysis of observational recordsas well as modeling as a means tocatalyze cross-disciplinary under-standing. Arctic-CHAMP wouldmake an obvious contribution tothe overall SIMS effort, and insome sense represents a substantialexpansion of SIMS. The ArcticNatural Sciences Program providescore support to disciplinary studiesin atmospheric sciences, earth sci-ences, ecosystem analysis, glaciol-ogy, and oceanography, as well asfacilitation of cross-disciplinarypolar projects supported by theNSF Office of Polar Programs(OPP). Coordination of Arctic-CHAMP with the Arctic NaturalSciences Program would bebeneficial.

Role of Current NSF Paleo StudiesA seasonal-to-centuries time frameis targeted for Arctic-CHAMPwhich will require retrospectivepaleo, historical, and contempo-rary monitoring in tandem withmodels describing each of thesetime domains. There would be ob-vious connections to virtually allNSF-OPP initiatives. The Paleo-environmental Arctic Sciences

(PARCS) program helps to articu-late the nature of Quaternary cli-mates over the Arctic and sub-Arc-tic. PARCS itself has promotedsynthesis studies including devel-opment of arctic proxy data (e.g.,PARCS database) and data-modelcomparisons (e.g., Circum-ArcticPaleoEnvironments [CAPE],Paleoclimate Modeling Inter-comparison Project [PMIP]).

NSF-Funded Monitoring andInstrumentation EffortsOPP is active in supporting initia-tives to improve the current stateof the art and it is recommendedthat Arctic-CHAMP capitalize onprogress to date. Two programs arenoteworthy. The first, the Polar In-strumentation and TechnologyDevelopment Program, supportsresearch infrastructure in high-lati-tude environments, includingdevelopment of novel techniquesfor harsh weather sampling. Sec-ond, the Long-Term Observatory(LTO) Program (joint betweenARCSS, Division of AtmosphericSciences, and Division of Environ-mental Biology) is currently sup-porting an array of individualprojects seeking to establish arcticenvironmental observatories,

NSF ProgramsSeveral offices of the Foundationsupport arctic research and thereare numerous opportunities forArctic-CHAMP to capitalize on thisshared interest in the region. NSFhas already invested heavily infield campaigns, modeling, moni-toring and instrumentation, data-base development, and paleostudies.

NSF Field-Oriented ProgramsArctic-CHAMP intensive field cam-paigns will be based on a rich heri-tage drawn from the several ARCSSfield programs listed in Box 6-2.Although many of these researchefforts have been fundamentallyinterdisciplinary—for example, thecollaborative work of boundarylayer physicists and ecosystem fieldscientists at LAII sites—there hasbeen little tangible movement to-ward an integration across allARCSS Program elements.

Existing Synthesis EffortsThe ARCSS Synthesis, Integrationand Modeling Studies (SIMS) pro-gram funds a small group of scien-tists who are beginning to worktoward a quantitative picture of theArctic as an interacting part of the

Appendix 3. Integration of Arctic-CHAMP with NSF and Other Federal Agency Initiatives


sample repositories, and remote/autonomous instrumentation.Long-term data sets associatedwith the NSF-LTER (Long-TermEcosystem Research) Program alsoprovide important supporting in-formation. An integration and ex-pansion of these NSF-supportedenvironmental monitoring capa-bilities will be key to a successfulArctic-CHAMP.

Integrated Arctic Database EffortsAnother critical component of Arc-tic-CHAMP will be development ofan integrated database of routinelycollected observational data (e.g.,precipitation, discharge), inten-sively sampled process-experimentresults (e.g., from long-term water-shed sites), biogeophysical forcingfields for Arctic-CHAMP models(e.g., from GCMs, weather predic-tion forecast/reanalysis models),and outputs from arctic systemsimulation models. A permanentarchive for ARCSS-generated datais well established through the Arc-tic System Science Data Coordina-tion Center at the National Snowand Ice Data Center (NSIDC). It isrecommended that an ongoingdialogue be established with thisdata repository to accommodateArctic-CHAMP data needs, withrequisite funding support fromARCSS.

Interagency Issuesand OpportunitiesArctic-CHAMP’s Role in U.S.Arctic ResearchBecause Arctic-CHAMP is envi-sioned to catalyze arctic and earthsystem synthesis activities, it couldmake important contributions tofederally funded programs beyondNSF. The Interagency Arctic Re-search Policy Committee (IARPC),

a multioffice initiative chaired byNSF, could provide the appropriatemultiagency context for Arctic-CHAMP. IARPC includes thirteenindividual agencies and offices,setting priorities for future arcticresearch, preparing multiagencybudget requests, and promotingcross-agency research coordina-tion, including logistical planningand data sharing. With the ArcticResearch Commission (USARC), itestablishes integrated arctic re-search policy. Arctic-CHAMP pro-vides an opportunity for IARPC tosupport its mandate of fosteringintegrated research and data ex-change.

Arctic-CHAMP and SEARCHMany of the issues described inthis hydrology-related strategicplan are, in fact, interagencySEARCH issues. These are con-cerned with changes in arctic hy-drology that may be related to thefeatures of more broad-scale pan-arctic environmental change (seeBox 4-1; Chapter 5 Boxes), andthus linked to the atmospheric andoceanic branches of the hydrologi-cal cycle (SEARCH SSC, 2001). Inrecognition of such linkages to theterrestrial domain, SEARCHevolved from ARCSS-OAII into athematic program extending acrossseveral individual components ofNSF-ARCSS. And now, SEARCHhas become an interagency andinternational effort as well. In theU.S. it includes partners from NSF,NOAA, DOD, NASA, EPA, andDOI. Arctic-CHAMP, since it seeksto provide a long-term and pan-arctic perspective on the terrestrialwater cycle, could play a promi-nent role in SEARCH and be NSF-ARCSS’s contribution to the overallinitiative.

Fostering Links to NOAA andArctic Operational AnalysisThe newly formed NOAA ArcticResearch Office promotes studiesinto the role of the Arctic in globalweather and climate variability,impacts of environmental changeon marine resources, and vulner-ability of human health in the Arc-tic to contaminant pollution.NOAA and NSF share leadershipfor U.S. interests in the Arctic Cli-mate Impact Assessment (ACIA), apan-arctic initiative of the intergov-ernmental Arctic Council set forcompletion in 2004. The NOAANational Center for EnvironmentalPrediction (NCEP) also can pro-vide contemporary numericalweather predictions, as well as sys-tematic reanalysis of multiyear at-mospheric dynamics to supportdiagnostic versions of Arctic-CHAMP models. The interactionshould be two-way, with Arctic-CHAMP researchers working withNOAA staff to improve current ver-sions of NCEP operational landsurface schemes over highlatitudes.

Arctic-CHAMP and NASASatellite MissionsNASA has recently put forward aseries of post-2002 mission con-cepts focused on land surface hy-drology. These include the system-atic collection of data on soilmoisture, global precipitation, in-land surface waters, and cold re-gion processes (Jackson et al.1999, Vörösmarty et al. 1999,Cline et al. 1999). The cryosphericmonitoring mission, envisioned toinclude some combination of pas-sive or active radiometers, will pro-vide a pan-arctic view of freeze-thaw dynamics, criticalinformation for activating and in-

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activating the large array of physi-cal and biological processes con-sidered by Arctic-CHAMP. NASAEarth Observing System (EOS) sen-sors will measure a very large num-ber of biogeophysical variables(Parkinson et al. 2000), whichshould also be exploited by Arctic-CHAMP diagnostic models of thecontemporary pan-Arctic. The Glo-bal Precipitation Mission (GPM)could be enhanced by the use ofArctic-CHAMP validation productsover the pan-Arctic. Work shouldbe directed within Arctic-CHAMPto develop a means for assimilat-ing the operational data sets toemerge from these missions.

Glacial mass balance and the asso-ciated discharges of meltwater isan important observational re-

quirement within Arctic-CHAMP.GLIMS (Global Land Ice Measure-ments from Space) is analyzing theworld’s glaciers using data fromEOS-ASTER (Advanced SpaceborneThermal Emission and ReflectionRadiometer). NASA ICESat, sched-uled to launch in July 2001, is abenchmark EOS mission to mea-sure ice sheet mass balance, cloudand aerosol heights, vegetation,and land topography via laser al-timetry. NASA’s Program in ArcticRegional Climate Assessment(PARCA) is currently using air-borne laser altimetry to measureice sheet thickness changes, withan emphasis on the changing char-acter of the Greenland ice sheet.

Appendix 3. Integration of Arctic-CHAMP with NSF and Other Federal Agency Initiatives

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Appendix 4International Collaborations

There are several major interna-tional science initiatives—both on-going and planned—that focus onthe Arctic. Many have made sub-stantial investments in polar re-search and could provide a mutu-ally beneficial synergy withArctic-CHAMP.

Among the numerous ongoing ef-forts, two broad-scale scientific ini-tiatives would provide benefit toArctic-CHAMP. The World Meteo-rological Organization’s World Cli-mate Research Program and theInternational Geosphere-BiosphereProgram (IGBP) represent majorefforts at securing an improved un-derstanding of the interactionsacross atmosphere-land-ocean sys-tem and their impacts on climatedynamics and the biosphere. Thepan-Arctic, as a well-bounded,linked land-atmosphere-ocean sys-tem, provides a unique test bed forregional and global climate, biol-ogy, and biogeochemical feedbackstudies. The World Climate Re-search Program (WCRP) GlobalEnergy and Water Experiment(GEWEX) and its focus on improv-ing land-atmosphere linkage mod-eling has numerous activities, in-cluding large-scale river basinexperiments, such as in Siberia,that will aid in the integration ofwater cycle dynamics into futureclimate models.

WCRP’s Arctic Climate SystemStudy (ACSYS) and follow-on Cli-mate and the Cryosphere (CliC)Project provides another importantprogrammatic link (WCRP 1998,1999, Allison et al. 2000). Majorsynthesis efforts are underway inthe IGBP, including analysis ofpaleoenvironmental dynamicsacross the high north. SEARCH hasalready integrated some of its ac-tivities with the WCRP ClimateVariability and Predictability Study(CLIVAR) and provides an excel-lent vehicle by which to unite Arc-tic-CHAMP hydrology with a muchlarger international initiative.

Intercomparison Studies

An important component of Arc-tic-CHAMP is the objective assess-ment of algorithms and observa-tional data sets, and there areseveral opportunities for linkagesto ongoing intercomparison ex-periments. Intercomparison stud-ies of the type envisioned for Arc-tic-CHAMP are already ongoing inseveral international fora (Box 6-3)(e.g., Goodison et al. 1998). Thesetreat land-surface exchanges in-cluding the dynamics of vegetationand snow and consider both con-temporary and paleo timedomains.

Existing Field Sites

A central idea behind Arctic-CHAMP is to create a series ofwell-instrumented process studysites across the northern high lati-tudes. The program could benefitgreatly by conjunctive use of exist-ing study sites, supported by bothfederal and international scienceagencies (Box 6-3). The value ofsuch experiments is highly evident,with the corresponding data setstypically analyzed for several yearsafter the dedicated field experi-ments have ended (e.g., BOREAS).Sustaining long-term experimentswill provide even more scientificvalue. Cost-sharing across severalinternational agencies will be re-quired but will provide to all theobservational context by which tomonitor ongoing arctic change andimprove upon our current level ofprocess understanding.

Remote Sensing

The use of remote sensing will beessential for achieving a truly pan-arctic perspective (Goodison et al.1999). U.S.-based activities, dis-cussed in chapter 2, are well-aug-mented by several internationalefforts. The utility of radar systemsto infer water and freeze or thawstate, together with the absence ofa U.S. radar satellite system, makes

Appendix 4. International Collaborations


collaboration with European, Japa-nese, and Canadian space agenciesessential. Such data have tradition-ally been costly both in terms oftheir price and computer storageand processing requirements, mak-ing it difficult to assemble longand coherent time series. A fund-ing commitment to make thesedata sets available would help toachieve a more complete picture ofthe seasonal storage and release offrozen water than is currently pos-sible.

Major MonitoringPrograms

Several multiorganizational obser-vational frameworks for systematicchange detection and improvedclimate prediction are also inplace, exemplified by the GlobalClimate and Global Terrestrial Ob-serving Systems (GCOS/GTOS).These seek to establish a global ref-erence network of land surface ob-servational weather/climate sta-tions, including several of highrelevance to the pan-Arctic (Cihlaret al. 2000). These activities alsoencompass International Perma-

frost Association activities inmonitoring frozen soil condition.The immediate challenge is for in-dividual countries to acquire theresources to implement an obser-vational program that will meetboth their own needs and contrib-ute to those outlined for GCOS/GTOS networks. Canada, for ex-ample, plans to enhance its currentGCOS surface network and itscryospheric observing system inremote northern regions as its con-tribution to international arcticscience.

Numerical WeatherPrediction and Reanalysis

The Arctic-CHAMP models will becast in both a diagnostic and prog-nostic mode. Important data setsare currently being prepared by theEuropean Center for Medium-range Weather Forecasting(ECMWF). The forthcoming ERA-40 global reanalysis will provide anearly half-century time series(1957–present) of atmosphericvariables at high spatial and tem-poral resolution. It is critical to as-sess the performance of this and

other such products from thestandpoint of water and energyconservation and the productionof sensible predictions with respectto the land surface hydrologicalcycle. ECMWF has been receptiveto the inputs of Arctic researchersand a productive interaction couldbe further promoted through Arc-tic-CHAMP.

International Data Archives

Arctic-CHAMP data requirementscould take advantage of severalmajor international data collec-tion, archiving, and distributionactivities. These involve both glo-bal and arctic-wide data reposito-ries. Given the wealth of geophysi-cal data sets currently available,meta-data systems and search en-gines optimized for Arctic-CHAMPresearch needs should be estab-lished. An early activity of theArctic-CHAMP Synthesis and Edu-cation Center could be the assem-bly of existing, hydrologically rel-evant arctic environmental data toprovide a quantitative benchmarkfor assessing future change.

the hydrologic cycle and its role in arctic and global

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