hydrologic fluctuations at pyramid lake, walker lake… · walker lake was low at a.d. 950 (
TRANSCRIPT
1
HYDROLOGIC FLUCTUATIONS AT PYRAMID LAKE, WALKER LAKE, AND THE
CARSON SINK, NEVADA DURING THE MEDIEVAL CLIMATE ANOMALY
KENNETH D. ADAMS
Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512
Lake levels in the western Great Basin have fluctuated throughout the Holocene in response to
changes in the hydrologic balance of their watersheds. The magnitudes of lake-level fluctuations
are not only based on changes in climate but are also controlled by the hypsometries of
individual basins, the presence and elevations of surrounding sills, and in the case of Walker
Lake, through river diversions. This presentation focuses on the lake-level histories of Walker
Lake, the Carson Sink, and Pyramid Lake through the Medieval Climate Anomaly (MCA; A.D.
900-1350), a time period characterized by severe and sustained droughts as well as periods
wetter than modern. Although not as temporally precise as tree-ring studies, lake-level histories
help discern the severity of droughts as well as the magnitude of wet periods. Despite differences
in hydrology, hypsometry, and the effects of sills, there are commonalities in the three records.
Walker Lake was low at A.D. 950 (<1,205 m), A.D. 1150 (<1,224 m), and at A.D. 1650 (<1,215
m). The first and last of these low periods, however, are associated with evidence for diversion
of the Walker River into the Carson Sink. Walker Lake also reached relative highstands at about
A.D. 1030 (~1,245m) and A.D. 1290 (~1,255 m), the latter level being several meters above the
historic highstand (A.D. 1868; ~1,252 m). A large lake in the normally dry Carson Sink formed
around A.D. 1100, reaching an elevation of ~1,204 m and surface area of ~3,000 km2. The
timing of this lake was coincident with the possible addition of the Walker River, but this
diversion by itself is not enough to account for the large Medieval lake. At Pyramid Lake, levels
were below 1,174 m around A.D. 950 and again at A.D. 1300, but reached near the historic
highstand level (~1,181 m; A.D. 1868) in the intervening time around A.D. 1100. The relatively
low amplitude of lake-level fluctuations at Pyramid Lake through the MCA may be explained by
a low sill (~1,177 m) that exports water to Winnemucca Lake. Lake-level fluctuations in the
western Great Basin are correlative with hydrologic records interpreted from tree rings and
pollen and show regional and dramatic responses to short-lived climate changes during the
MCA, both drier and wetter than present.
2
EXAMINING GULF OF ALASKA MARINE PALEOCLIMATE
AT SEASONAL TO DECADAL TIMESCALES
JASON A. ADDISON (1), BRUCE P. FINNEY (2), AND JOSEPH S. STONER (3)
(1) U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025
(2) Department of Biological Sciences, Idaho State University, Pocatello, ID 83209-8007
(3) College of Ocean and Atmospheric Sciences, Oregon State University,
Corvallis, OR 97331-8563
The Gulf of Alaska, located in the subarctic northeast Pacific Ocean, experiences dramatic
climate variability over seasonal, annual, and decadal timescales. Environmental forcing
mechanisms that affect physical parameters (e.g., precipitation and SST) can be expressed
through indicators of marine ecosystem productivity due to a coupled positive feedback
mechanism between the oceanic Alaska Gyre upwelling center and the atmospheric Aleutian
Low pressure cell. This system is sensitive to low-latitude phenomena (ENSO), and due to the
Pacific-North American teleconnection pathway, conditions in the Gulf of Alaska can influence
distant regions throughout the Northern Hemisphere. However, it differs from most eastern
boundary current settings (e.g., California) in that it is dominated by downwelling of surface
waters throughout most of the year.
Using these modern observations as a template for describing past fluctuations in
paleoceanographic proxies, we present data from two marine sediment cores collected in
temperate ice-free fjords along the Gulf of Alaska margin. These cores preserve evidence of past
environmental variability at decadal to annual temporal resolutions for the past 4,000 (EW408-
44JC) to 8,000 (EW408-33JC) years. Computerized tomography scans show complex internal
structures in these cores, including millimeter-scale laminations as well as high-density turbidite
layers likely formed by past seismic or flood activity. Isotopic and geochemical analysis of the
laminations indicate they are composed of cyclical couplets, consisting of a black, high-density
terrigenous organic matter (OM)-rich band and a green, low-density marine OM-rich band.
Based on a linear age-depth model interpolated between two well-preserved AMS 14
C
macrofossil samples, we find that preliminary lamination thickness measurements of the marine
OM-rich bands between 3,900 to 3,300 cal yr B.P. indicate variability in the range of ENSO
periodicities. These results suggest a linkage between tropical forcing and extratropical
sedimentation that predates anthropogenic climate change.
3
MULTI-PROXY EVIDENCE FOR MIDDLE AND LATE HOLOCENE
FLUCTUATIONS IN CLIMATE REGIME IN THE
NORTH-CENTRAL GREAT BASIN
LYSANNA ANDERSON, DAVE WAHL, SCOTT STARRATT, AND ELMIRA WAN
U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025
[email protected], [email protected], [email protected], [email protected]
The north-central Great Basin lies within the transition zone between the winter-dominated
precipitation regime of the Pacific coastal states and the monsoon-driven summer precipitation
regime of the Southwest. Paleoclimatic reconstruction of fluctuations in the dominance of these
regimes across the region has proven difficult due to a paucity of paleoclimate records. Here we
present a high-resolution middle and late Holocene charcoal record to augment existing pollen
and diatom data from Favre Lake in the Ruby Mountains, Nevada (40° 26‘ 39.80‖ N, 115° 20‘
49.5‖ W, 2,899 m a.s.l.). High concentrations of charcoal corresponding to diatom and pollen
data indicate rising lake level are interpreted as reflective of sustained summer precipitation and
a strengthened southwestern monsoon at around 5,400 cal yr B.P. These conditions may have
supported an increase in fire intensity and frequency as a result of increased fuel buildup and
frequent lightning. Lower and more variable charcoal concentrations after approximately 4,000
cal yr B.P., concurrent with relatively quiescent pollen and diatom assemblages, suggests the
influence of a strengthening and increasingly variable ENSO, resulting in a shift to a more
variable, lower intensity fire regime.
THE IMPACT OF LITTLE ICE AGE COOLING ON MOUNTAIN HEMLOCK (Tsuga
mertensiana) DISTRIBUTION IN SOUTHCENTRAL, ALASKA
R. SCOTT ANDERSON (1), DARRELL S. KAUFMAN (1), CALEB SCHIFF (1),
TOM DAIGLE (2), AND EDWARD BERG (3)
(1) School of Earth Sciences and Environmental Sustainability,
Northern Arizona University, Flagstaff, AZ 86011
[email protected], [email protected], [email protected]
(2) GEI Consultants, 4601 DTC Boulevard, Suite 900, Denver, CO 80237
(3) U.S. Fish and Wildlife Service, Kenai National Wildlife Refuge,
P.O. Box 2139, Soldotna, AK 99669 (retired)
The natural distribution of mountain hemlock (Tsuga mertensiana) in the northeast Pacific is in
regions of cool to cold maritime climate, with cool winters and short summers. Presently, the
species reaches its northern distribution in southcentral Alaska. We investigated the Holocene
history of vegetation and climate change for two sites in and near the Kenai Mountains, south of
Anchorage. Mica Lake is located at 100 m elevation on an island in Prince William Sound, near
the northern limits of the tree, whereas Goat Lake is located at 550 m elevation, in the Kenai
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Mountains, at the upper local limit of mountain hemlock. From pollen analysis of these lake
sediments, mountain hemlock became established at Mica Lake by at least 6,000 cal yr B.P. The
tree became established at the higher elevation Goat Lake sometime after 3,000 years ago.
Expansion at both sites was abruptly curtailed during the colder climate of the Little Ice Age,
commencing at Goat Lake in the mid-17th
century. The decline was more extensive at the Goat
Lake site, where climatic conditions may have been severe enough to reduce or eliminate the
mountain hemlock forest there. This is consistent with tree-ring evidence of major glacial
advance (Wiles and Calkin 1993; 1994; Daigle and Kaufman, 2008; Wiles et al. 2009) at this
time in the Kenai Mountains. Warmer conditions during the 20th
century have reversed that
trend.
Wiles, G.C. and Calkin, P.E., 1993, Neoglacial fluctuations and sedimentation of an iceberg-calving glacier resolved
with tree rings (Kenai Fjords National Park, Alaska): Quaternary International, v. 18, p. 35–42.
Wiles, G.C., and Calkin, P.E., 1994, Late Holocene, high-resolution glacial chronologies and climate, Kenai
Mountains, Alaska: Geological Society of America Bulletin, v. 106, p. 281-303.
Wiles, G.C., Barclay, D.J., Calkin, P.E., and Lowell, T.V., 2008, Century to Millennial-Scale Temperature
Variations for the Last Two Thousand Years Inferred from Glacial Geologic Records of Southern Alaska:
Global and Planetary Change, v. 57, doi:10.1016/j.gloplacha.2006.07.036
Daigle, T. A. and Kaufman, D. S., 2009, Holocene Climate inferred from glacier extent, lake sediment and tree rings
at Goat Lake, Kenai Mountains, Alaska, USA: Journal of Quaternary Science, v. 24, p. 33–45.
RESPONSE OF DIATOM AND SILICOFLAGELLATE ASSEMBLAGES TO CLIMATE
CHANGE IN THE SANTA BARBARA BASIN DURING THE PAST 178 YEARS AND
THE RISE OF THE TOXIC DIATOM PSEUDO-NITZSCHIA AUSTRALIS
JOHN A. BARRON (1), DAVID BUKRY (1), AND DAVID B. FIELD (2)
(1) Volcano Science Center, MS 910, U.S. Geological Survey, Menlo Park, CA 94025
[email protected], [email protected]
(2) Department of Natural Sciences, Hawaii Pacific University, Kaneohe, HI 96744
Diatoms and silicoflagellate assemblages studied in two year-increments of varved samples in
Santa Barbara Basin (SBB) box core 0806 spanning 1830 to 2007 suggest that unprecedented
warming of surface waters began at about 1940, which is in agreement with CalCOFI SST data
and changes in planktonic foraminferal assemblages. These earlier studies argued that increased
stratification and deepening of the thermocline occurred during the latter half of the 20th
Century
within 50–100 km of the southern California coast in response to anthropogenically-forced
global warming. Diatoms (Thalassionema nitzschioides = TN) and silicoflagellates (Distephanus
speculum s.l. = DS) indicative of cooler waters and a shallow thermocline declined markedly in
relative numbers in the SBB beginning at about 1940. Prior to that time, TN constituted on
average ~30% of the Chaetoceros-free diatom sediment assemblage and DS on average ~36% of
the silicoflagellate assemblage. Between 1940 and 1996 these relative abundances drop to ~20%
(TN) and ~8% (DS). Cooling of surface waters coincident with the onset of negative PDO
conditions in the North Pacific in 1998 brought about a return to pre-1940 values of these cool
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water taxa (TN ~31%, DS ~25%). However, this recent regional cooling appears to have been
accompanied by profound changes to surface water productivity events in the SBB. Pseudo-
nitzschia australis, a diatom associated with domoic acid, a neurotoxin that causes shellfish
poisoning and marine mammal deaths, appeared suddenly in the SBB sediment record in 1999
and increased significantly in numbers as a bloom-forming taxon (relatively to Chaetoceros
spores) in 2003. Prior to 2003 diatom blooms represented in the SBB sediment record consisted
predominantly of Chaetoceros spores and less commonly of Rhizosolenia spp. (Neocalyptrella
robusta and R. setigera). Fecal pellets dominated by valves of P. australis, however, are
abundant in both the 2003 and 2006 samples, coincident with recorded incidents of domoic acid
increase and widespread shellfish poisoning in the SBB.
According to published studies the first recorded large-scale toxigenic P. australis bloom
in the SBB occurred in June 1998 as part of more widespread blooms and shellfish poisoning
along the central California coast. Although high numbers (or blooms) of P. australis were
reported in plankton studies off the Scripps Pier in La Jolla during the 1930‘s, 1967, and 1983,
blooms of P. australis associated with toxic domoic acid levels were first reported in 1991 in
Monterey Bay. Biologists have shown that Pseudo-nitzschia blooms correspond to lowered sea
surface temperatures and increased salinity that are typical of coastal upwelling events, but they
have debated whether increased nutrients levels from river runoff have been a factor in the recent
increase of these blooms. Laboratory studies have demonstrated that toxin production in some
species of Pseudo-nitzschia may increase under silicic acid or phosphorous limitation. Whatever
the cause, our 177 year-long diatom sediment record suggests that the recent increase of Pseudo-
nitzschia blooms in the SBB has occurred at the expense of Chaetoceros and Rhizosolenia, the
natural bloom-forming diatoms in the SBB.
6
EXTENDING THE RECORD OF ABRUPT AND MILLENNIAL-SCALE
CLIMATE AND OCEAN CHANGE THROUGH THE MID-PLEISTOCENE
TRANSITION IN SANTA BARBARA BASIN, CALIFORNIA
RICHARD J. BEHL (1), SARA AFSHAR (1), JAMES P. KENNETT (2), CRAIG
NICHOLSON (3), CHRISTOPHER C. SORLIEN (2), COURTNEY J. MARSHALL (1),
TESSA M. HILL (3), SARAH M. WHITE (3), WALTER E. DEAN (4),
AND JOHN A. BARRON (5)
(1) Department of Geological Sciences, California State University, Long Beach, CA 90840
[email protected], [email protected], [email protected]
(2) Department of Earth Science, University of California, Santa Barbara, CA 93106
[email protected], [email protected], [email protected]
(3) Department of Geology, University of California, Davis, CA 95616
[email protected], [email protected]
(4) U.S. Geological Survey, Federal Center, P.O. Box 25046, Denver, CO 80225
(5) U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025
Quaternary strata in the Santa Barbara basin, California, hold the potential to extend subdecadal-
resolution paleoclimate records back through the Mid-Pleistocene Transition (>1 Ma). In support
of proposed continuous coring by IODP, we conducted an integrated seismic acquisition and
piston coring campaign in 2005 and 2008 where we acquired >40 2-11 m piston cores that
provide ~2,000-9,000 year windows into past climate behavior. We identified and mapped
distinctive seismic stratigraphic horizons across the basin to seafloor outcrop in pre-existing
multichannel seismic (MCS) reflection data and in high-resolution MCS and towed chirp data
acquired during our research cruises. Horizons and cores are dated by interpolation between
ODP Site 893, a previously published 1-Ma horizon, and recovered tephra, biostratigraphic, and
climatic datums. Sedimentation rates are high enough (70-130 cm/1,000 yr) to generate ultra-
high-resolution data on the rate and character of climate and ocean change on human time scales.
High-frequency climatic oscillations are recorded in many of these cores by variations in
massive to laminated sedimentary fabric, oxygen and carbon isotopes, % total organic carbon, %
carbonate, % biogenic silica, abundance of redox- and productivity-sensitive elements, or
planktonic foraminiferal assemblages. In general, warm interstadials are represented by
laminated, organic-rich sediment deposited under highly productive surface waters. Rapid, multi-
decadal-scale climatic and oceanographic transitions occur during different climatic states, such
as: MIS 3-like intermediate conditions, deglacial transitions, and glacial episodes, but not during
otherwise fully interglacial conditions. These results indicate that the California margin has been
sensitive to climatic forcing and experienced rapid climatic fluctuations since at least the Mid-
Pleistocene Transition when predominance of 41,000 year climate cycles shifted to a 100,000
year climate cycle regime.
7
SUBSTRATE AND CLIMATE INFLUENCES ON HOLOCENE
FOREST DEVELOPMENT
CHRISTY E. BRILES (1,2), CATHY WHITLOCK (3), CARL N. SKINNER (4),
AND JERRY MOHR (5)
(1) School of Geography and Environmental Science, Monash University, Australia, VIC 3800
(2) Palynology Laboratory, Texas A&M University, College Station, TX, 77803-4352
(3) Department of Earth Sciences, Montana State University, Bozeman, MT 59717
(4) U.S. Forest Service, Pacific Southwest Research Station, Redding, CA 96002
(5) College of Forestry, Oregon State University, Corvallis, OR 97331
The role of substrates in facilitating plant adjustments to climate change and influencing fire
regimes in the past has received little attention. The Klamath Mountains of northern California
consist of a mélange of rock types, including ultramafic types with high levels of toxic minerals
and low levels of nutrients for plants that result in unique and diverse plant communities. To
better understand the development of these diverse forests, pollen and macroscopic charcoal
preserved in the sediments of eight cirque lakes in different geological settings, were analyzed.
The records were compared with independent climate records from the Klamath Mountain region
to determine the relative role of geology and climate in shaping forests and fire regimes since the
last glacial period (~15,000 yr B.P.). Comparison of sites suggests that ultramafic and non-
ultramafic substrates supported distinctly different plant communities through the period. Plants
on ultramafic substrates were less responsive to climate change than forests on non-ultramafic
substrates, with the only major compositional change occurring at the glacial/interglacial
transition (~11,500 yr B.P.). Plants on non-ultramafic substrates were more responsive to
climate changes, and tracked climate by moving along elevational gradients. Fire regimes were
similar until 4,000 yr B.P. on both substrate types. After 4,000 yr B.P., understory fuels on
ultramafic substrates became sparse and fire activity decreased, while on non-ultramafic
substrates forests became increasingly denser and fire activity increased. The combination of
long-term persistence of plant communities on ultramafic sites and individualistic range
adjustments of forest dominants on non-ultramafic sites help to explain the high levels of plant
diversity and endemism in the Klamath Mountain region.
8
PRELIMINARY RESULTS FROM A NEW HIGH-RESOLUTION ICE CORE FROM
COMBATANT COL, MOUNT WADDINGTON, BRITISH COLUMBIA, CANADA
DOUGLAS H. CLARK (1), NICOLE BOWERMAN (1) ERIC J., STEIG (2),
PETER NEFF (2), ERIN PETTIT (3), JOSEPH MCCONNELL (4),
BELLA BERGERON (5), AND BRIAN MENOUNOS (6)
(1) Geology Department, Western Washington University, Bellingham, WA 98225
(2) Earth and Space Sciences, University of Washington, Seattle, WA 98025
(3) Department of Geology and Geophysics, University of Alaska, Fairbanks, AK 99775
(4) Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512
(5) ICDS, Madison, WI 53706
(6) University of Northern British Columbia, Prince George, BC, V2N 4Z9, Canada
In July, 2010, we recovered a 140 m ice core from Combatant Col, elevation 3,200 m, on the
shoulder of Mount Waddington, British Columbia Coast Range, Canada, as part of a larger
Canadian effort (WC2N) to investigate glacier-climate linkages across western Canada. The
geographic setting and depth of ice (200+ m) at the site make it one of the more promising
locations for collecting a relatively long ice-core record in North America outside of Alaska, and
should help improve our understanding of long-term variability in the pattern and strength of
precipitation across the region. Analysis of gridded GPS stakes during the summer provide
constraints on glacier flow across the Col and will be used to develop a flow model to evaluate
thinning and flow of ice at the core site. We also collected continuous weather data and shallow
snow samples in the Col during the spring and summer in order to assess the evolution of snow
over the course of the summer.
Preliminary analyses of melt-layers, stable water isotope ratios, soot, and elemental
concentrations in our cores show unambiguous seasonal stratigraphy in the ice, which will
eventually provide a detailed age-depth model. The ice accumulation rate recorded in the ice
core averages 2,500-3,500 kg/m3yr. Ice temperature and instrumental records indicate that mean
annual temperature at the Col is -5°C. Summer surface melt produces local melt horizons that
are consistent with the identification of summertime snow in the isotope, soot, and dust
stratigraphy. Infrequent melt horizons also occur within the winter stratigraphy, but there is no
evidence for significant migration of water across annual layers. Detailed analyses of the full
core are in-process…more details at the meeting!
9
PROJECTED 21ST
CENTURY TRENDS IN HYDROCLIMATOLOGY
OF THE TAHOE BASIN
ROBERT COATS (1), MARIZA COSTA-CABRAL (2), MICHAEL DETTINGER (3), JOHN
RIVERSON (4), JOHN REUTER (1), GOLOKA SAHOO (1),
GEOFFREY SCHLADOW (1), AND BRENT WOLFE (5)
(1) University of California Tahoe Environmental Research Center, Davis, CA 95616
(2) Hydrology Futures, Seattle, WA 98107
(3) U.S. Geological Survey, Scirpps Institution of Oceanography, La Jolla, CA 92093
(4) Tetra Tech Inc., Fairfax, VA 22201
(5) Northwest Hydraulic Consultants, Inc., West Sacramento, CA 95691
Using historic lake temperature, air temperature and hydrologic data, we previously showed that
1) the average temperature and thermal stability of Lake Tahoe have increased since 1970, 2)
basin air temperatures have increased since 1910, 3) date of snowmelt peak runoff is shifting,
and 4) the snowfall:rainfall ratio is decreasing. Here we report on the results of efforts to model
impacts of 21st century climate change on basin hydroclimatology and on Lake Tahoe itself.
Meteorological data from the GFDL model for two emission scenarios were downscaled to a 12
km grid, bias-corrected, and used to drive a distributed hydrologic model. Output from this
watershed model, along with the meteorological data, was then used as input to a 1-d
hydrodynamic and water quality model of the lake (DLM-WQ, developed at U.C. Davis), and to
calculate stream-flow statistics for the Upper Truckee River (UTR) and trends in the Palmer
Drought Severity Index (PDSI) for two sites representing wet and dry zones in the basin.
The results indicate that 1) recent trends in basin climate and hydrology will continue,
with a possible 5 oC increase in average annual air temperature by 2100, 2) precipitation will
continue to shift from snow to rain, and annual amounts are projected to decline in the latter half
of this century, 3) the timing of snowmelt and the hydrograph centroid are likely to shift toward
earlier dates, 4) the magnitude of the estimated 100-year flood of the UTR is likely to vary
greatly over the course of this century but eventually decline in response to warming and drying,
5) summer low-flow is projected to decline, 6) drought, as measured by the PDSI, is projected to
increase, especially in the latter third of this century, and most strongly on the eastern (drier) side
of the basin, 7) the lake may be expected to continue warming, and the resulting increasing
thermal stability will likely limit deep mixing and deep ventilation, with impacts on dissolved
oxygen, internal nutrient loading and water quality, and 8) the annual frequency of episodes of
no-lake-outflow is likely to increase, especially toward the end of this century.
10
POST-GLACIAL PLANT MIGRATIONS ARE SIMILAR TO HISTORIC AND
ONGOING DISPERSAL AND SUCCESSION
KENNETH L. COLE (1, 2), KIRSTEN IRONSIDE (2), AND NEIL COBB (2)
(1) Southwest Biological Science Center, Colorado Plateau Research Station,
U.S. Geological Survey, P.O. Box 5614, Northern Arizona University, Flagstaff, AZ 86011
(2) Merriam-Powell Center for Environmental Research, P.O. Box 4071,
Northern Arizona University, Flagstaff, AZ 86011
[email protected], [email protected]
Modeling the effects of warming climates on plant species requires estimates of their future
dispersal and proliferation into new areas. Estimates of likely spread into new areas of potential
climate can be informed by: 1) paleo-migration and succession rates averaged over millennia
following past sharp increases in temperature or past disturbances, 2) observations of historic
shifts in response to 20th
century warming climates and disturbances, and 3) recent vegetative
dynamics observed through permanent plots or autecological studies. While good data for a
single species rarely exists for all three time periods, information from two or more sources is
usually in agreement.
Because dispersal and proliferation for many species requires a chance sequence of
favorable years, migration rates are best projected as averages over 50 years or more. Species
vary greatly in their rates of potential migration. Early successional, disturbance-adapted herbs,
grasses, and shrubs that are widely spread by wind or animals (ie. Encelia farinose, Erodium
cicutarium), have averaged as much as 1000 m/yr in historic and recent data. Late successional
trees of humid forests (ie. Picea mariana, Fagus grandifolia) seem to have migrated at rates as
fast as 500 m/yr in the early postglacial despite requiring a century or more to succeed to
dominance of historic old fields. This pattern suggests expansion outward from undetected
satellite populations. But even at 500 m/yr, these species will only spread about 45 km by the
time the atmosphere reaches a doubling of pre-industrial carbon dioxide. Late successional trees
in semi-arid regions (ie. Pinus edulis, Juniperus monosperma) have migrated at 40 to 100 m/yr
in postglacial and historic records. But the slowest rates of past and recent dispersal and
proliferation belong to many late successional desert shrubs and succulents (ie. Coleogyne
ramosissima, Larrea tridentata, Yucca brevifolia) which have, and are, only spreading at 10 m/yr
or less.
11
GEOCHEMICAL EVIDENCE FOR CHANGES IN SURFACE-WATER
PRODUCTIVITY AND BOTTOM-WATER REDOX CONDITIONS
DURING GLACIAL-INTERGLACIAL TRANSITIONS
IN THE SANTA BARBARA BASIN
WALTER E. DEAN
Geology and Climate Change Science Center, MS 980,
U.S. Geological Survey, Federal Center, Denver CO 80225
Geochemical investigations of the transition between the last glacial interval (LGI) and the
Holocene, and between stadial and interstadial intervals in Oxygen Isotope Stage 3 (OIS 3) in
sediment cores from the Gulf of Alaska, the Alta and Baja California margins, and the Cariaco
Basin show distinct differences. In general, interstadial and interglacial intervals are
characterized by high surface-water productivity, oxygen-deficient bottom waters, and laminated
sediments. Glacial and stadial intervals are characterized by low surface-water productivity,
well-oxygenated bottom waters, and bioturbated sediments. Surface-water productivity is tracked
by concentrations of organic carbon (OC) and cadmium (Cd). Bottom-water oxygen conditions
are tracked by laminated vs. bioturbated sediments and concentrations of redox-sensitive trace
elements, notably molybdenum (Mo), vanadium (V), nickel (Ni), uranium (U), and zinc (Zn).
Results show that interglacial and interstadial intervals, such as the Bölling-Alleröd (B-A) warm
interval, the Holocene, and interstadials within OIS 3, are characterized by laminated sediments
and high concentrations of OC, Cd, and Mo. Glacial and stadial intervals, such as the LGI, the
Younger Dryas (YD) cold interval, and stadials within OIS 3, are characterized by bioturbated
sediments and low concentrations of OC, Cd, and Mo. Recent results from overlapping piston
cores that collected sediments in the Santa Barbara Basin with largely undated ages going back
to older glacial-interglacial transitions show similar sedimentological and geochemical
characteristics as younger transitions, such as the B-A/YD, namely, laminated sediments
containing high concentrations of OC, Cd, and Mo in interglacials and bioturbated sediments
containing low concentrations of OC, Cd, and Mo in glacials. The best dated of these transitions
is between OIS 16 and OIS 15, which contains the Lava Creek B ash dated at 639,000 years old.
Oxygen isotope data on these cores obtained by Jim Kennett show that the transition from cold to
warm can occur within decades. The interglacial intervals have millennial-scale interstadial-
stadial cycles like those in OIS 3 on the California margin, and some of the stadials were as
abrupt and as cold as the YD.
12
EVALUATION OF VEGETATION DYNAMICS AND CLIMATIC OSCILLATIONS IN
THE SACRAMENTO-SAN JOAQUIN DELTA OF CALIFORNIA
DURING THE HOLOCENE
IRINA DELUSINA
Department of Geology University of California, Davis, CA 95616
Pollen analysis of three cores of peat, deposited in the Sacramento-San Joaquin Delta of
California and situated in different locations: Webb Tract levee, Browns Island, and Franks Tract
wetland, was used to reconstruct the vegetation dynamics and climatic trends during the
Holocene. A salinity index, calculated from pollen criteria, was also used. The pollen data
indicate that between about 6,500 and 5,250 yr B.P., when peat first started to form, the area was
undergoing a relatively cool period and that fresh or low salinity water existed in the delta area.
This interval was followed by a recognizable shift in forest vegetation which indicates a warming
trend that reached its peak at 5,000 yr B.P. The salinity of the water at this point was the highest
for the studied time interval. A new, cooler interval occurred between 4,000 and 2,050 yr B.P.,
with low salinity. However, in the middle of this interval at about 2,900 years BP, there is a
peak in salinity, which probably indicates a drought. After 2,050 yr B.P., cool and wet
conditions, with moderate to high salinity, are established. After 1,250 yr B.P., conditions move
toward wet and warm, and the salinity becomes high again.
The study demonstrates how the process of peat formation and local environmental and
hydrological conditions are influenced by general climatic trends. This study was conducted
within the framework of Project REPEAT (2007-2009).
PROJECTED CLIMATE CHANGES AND FLOOD RISKS IN CALIFORNIA
MICHAEL D. DETTINGER (1), TAPASH DAS (2), DANIEL R. CAYAN (1),
AND THERESA CARPENTER (2,3)
(1) U.S. Geological Survey, Scripps Institution of Oceanography, La Jolla, CA 92093 [email protected]
Scripps Institution of Oceanography, La Jolla, CA92093
(2) Hydrologic Research Center, 12780 High Bluff Drive, Suite 250 San Diego, CA 92130
Current projections of climate change are unanimous in calling for warming temperatures over
the western States. Beyond this, they more-or-less unanimously yield trends towards less
precipitation over the extreme southwest and more over the extreme northwest, but are
indeterminate (as a whole) over the rest of the western States. These precipitation uncertainties
reflect tradeoffs between two fairly simple and reliable global-scale heat-transfer processes that
are energized directly by increasing greenhouse-gas concentrations in all climate models and
thus are unlikely to be resolved any time soon. Despite uncertainties about overall, long-term
13
precipitation amounts over the western States, the direct influences of warming, together with
projections of increased storm intensities that most climate models share, current projections of
flood risk around the Sierra Nevada and in flash-flood zones of southern California suggest that
risks may increase substantially in most California settings during the 21st century. Results from
a) storm-typing analyses of multi-model ensembles of current climate-change projections, b)
snow-fed hydrology simulations forced with multi-model ensembles of downscaled climate-
change projections, and c) flash-flood frequencies simulated by geomorphically constrained
runoff–generation models forced by downscaled, orographically enhanced precipitation
projections, taken together suggest that—regardless of whether average precipitation in
California increases or decreases—floods may be enhanced under the 21st century climate.
SIMULATING MOUNTAIN CLIMATES: CHALLENGES AND APPROACHES
PHILIP B. DUFFY
Climate Central, Inc. Palo Alto, CA 94028 and Woods Institute on the Environment,
Stanford University, Stanford, CA 94305
The mountainous regions near the Pacific are among the most vulnerable to climate change. And
impacts of climate change in these regions can have widespread effects, for example increased
water scarcity. At the same time, our ability to simulate past climate and project future climate is
generally worse in mountainous regions than elsewhere.
I will discuss challenges inherent in understanding and simulating climate in
mountainous regions, as well as approaches commonly used to address them.
The talk should be useful to those not specifically interested in mountain climates
because, as I will point out, difficulties simulating mountain climates are generally more extreme
versions of those encountered when working elsewhere.
14
COMPARISON OF VARVE CHRONOLOGY AND 14
C DATES AT HIGH
RESOLUTION: REEVALUATING THE AGE OF THE SANTA BARBARA BASIN
LATE HOLOCENE PALEOCLIMATE SEQUENCE
LARIANNA DUNN (1), INGRID L. HENDY (1),
AND ARNDT SCHIMMELMANN (2)
(1) Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109
[email protected], [email protected]
(1) Department of Geological Sciences, Indiana University,
Bloomington, IN 47405
One of the most significant recent shifts in climate was the transition between the Medieval
Warm Period (MWP) and the Little Ice Age. This transition occurred in Santa Barbara Basin
(SBB) around A.D. 1200 based on radiocarbon (14
C) dating, while the varve-count chronology
suggests A.D. 1400. This 200 year difference is extremely important for accurately comparing
the SBB paleoclimate record to records both in the southwest region and globally. There are
three possible factors that may contribute to the discrepancy between SBB varve-count and 14
C
chronologies: 1) erosion of varves below turbidites (i.e. ‗missing varves‘), 2) Changes in surface
water 14
C reservoir ages (e.g., due to changes in upwelling), and 3) varve counting errors when
sedimentation failed to express distinct seasonal differences (undercounting of varves), or when
very strong seasonal changes in sedimentation were interpreted as annual varves (overcounting
of varves). Previous studies lacked sufficient temporal resolution to determine the cause of the
discrepancy between these independent dating techniques. Laminated sediments from SBB have
previously been dated using consecutive varve-counting covering the past ~ 2,000 years. Here
we provide the first high-resolution 14
C study in the SBB. Kasten core SPR0901-06-KC
(34°16.914N, 120°02.419W) was sampled at ~5 cm intervals over the upper 2.6 meters, and 53 14
C ages for mixed planktonic foraminfera (particularly Globigerina bulloides and
Neogloboquadrina pachyderma) were generated at Lawrence Livermore National Laboratory‘s
Center for Accelerator Mass Spectrometry. After removing a local 14
C reservoir effect of 633
years (presumed to have been constant), 14
C dates were then calibrated with IntCal09 using the
calibration program CALIB v. 6.0. Comparison of the calibrated 14
C datum to the varve
chronology reveals an increasing offset from the varve chronology back to A.D. 440, with the
loss of ~15 years in every 100 varves counted. The results demonstrated a linear difference in
age with an r2 of 0.78, indicating a consistent net undercounting in varve years relative to
14C
years.
15
INITIAL RESULTS FROM A NEW LAKE ELSINORE SEDIMENT CORE REVEAL
EVIDENCE FOR HYDROLOGIC CHANGE DURING THE
LATE GLACIAL-HOLOCENE TRANSITION
JOANNA M. FANTOZZI (1), MATTHEW E. KIRBY (1),
STEVEN P. LUND (2), AND CHRISTINE A. HINER (1)
(1) Department of Geological Sciences, California State University, Fullerton, CA 92834
(2) Department of Earth Sciences, University of Southern California,
Los Angeles, CA 90089
While there are several well-developed records of marine climate from Southern California that
span the late Glacial-Holocene transition, there are currently no high-resolution terrestrial
counterparts. In June 2010, a 20 meter sediment core covering 10-30 meters below the sediment-
water interface was extracted from the depocenter of Lake Elsinore, California – the largest
natural, permanent lake in the region. Here, we present the initial results of a multi-proxy study
on the section of this sediment core that spans the late Glacial-Holocene transition (18.5-10 m
below the sediment-water line [bswl]). Initial results reveal three distinct sediment units. Unit I
(15-10 m bswl) is composed of a homogeneous, often mottled (bioturbated?), gray mud with
high and moderately variable magnetic susceptibility values (avg = 1.20 ± 0.29 x 10-7
m3/kg),
low organic matter content (6.50 ± 0.83%), and highly variable carbonate content (12.21 ±
4.89%). Unit II (17-15m bswl) is a transitional unit that begins as a gray mud similar to that of
Unit I and transitions into a massive to laminated brown mud with low and variable magnetic
susceptibility values (0.88 ± 0.38 x 10-7
m3/kg), increasing organic matter content (11.52 ±
2.19%), and highly variable carbonate content (10.84 ± 4.75%). Unit III (18-17.5m bswl) is
characterized by a massive to laminated brown mud with very low and stable magnetic
susceptibility values (0.87 ± 0.19 x 10-7
m3/kg), declining organic matter content (11.21 ±
2.02%), and low to negligible carbonate content (5.0 ± 0.87%). Together, these data indicate a
significant change in Lake Elsinore‘s depositional environment that is likely related to
hydrologic change (i.e. average lake level) during the late Glacial-Holocene transition – a change
that has not previously been documented in southern California.
16
A HISTORICAL RECONSTRUCTION OF AN ALEXANDRIUM CATENELLA CYST
RECORD FROM SEQUIM BAY, WASHINGTON AND ITS
RELATION TO CLIMATE VARIABILITY
KIRSTEN FEIFEL AND RITA HORNER
Department of Oceanography, University of Washington, Seattle, WA 98195
Detection of paralytic shellfish toxins (PSTs) due to blooms of the harmful alga Alexandrium
catenella has increased in Puget Sound, Washington since the 1970s. This increase has been
linked to large-scale climate variability such as the Pacific Decadal Oscillation (PDO), and local
variables such as air temperature, stream flow, and sea surface temperature. However, existing
records of A. catenella bloom dynamics, based on toxins in shellfish, are relatively short, dating
only to 1957, and therefore it is difficult to statistically assess the influence of short-term,
stochastic environmental variability versus long-term, multi-decadal, trends in relation to
climatology. Hence, we examined the relationship between historical climate variability and
profiles of A. catenella cysts in a sediment core from Sequim Bay, Washington, in order to better
determine the influence of climate on A. catenella populations. The cyst record allowed us to
extend the A. catenella history in Sequim Bay to 1878 and to statistically evaluate the historical
relationship between the cyst record and available environmental parameters. There is no
statistically significant relationship between the cyst record and PDO or stream flow, but there is
a positive, significant relationship between local air temperature and sea surface temperature.
The disconnect between historical, large-scale North Pacific sea surface variability, as measured
by the PDO index, may highlight the importance of local climate variability and the possible
influence of recent warming in the Puget Sound due to anthropogenic climate change as driving
factors of the A. catenella population increase in the 1970s.
MULTIPLE MODES OF VARIABILITY IN THE NORTHEAST PACIFIC:
A HISTORICAL PERSPECTIVE
DAVID B. FIELD
Hawaii Pacific University, Kaneohe, HI 96744-5297
Recent flooding in southern California has been occurring in the La Niña winter of 2010-2011,
which is an atypical pattern of La Niña conditions; high rainfall is more typically associated with
El Niño conditions or a positive phase of the Pacific Decadal Oscillation (PDO). Much attention
has been given to the PDO as a dominant source of decadal-scale variability in North Pacific
SST patterns, which, in turn, are associated with variations in precipitation off western North
America. However, the PDO has the trend in SSTs removed. Moreover, paleo-records indicate
that the PDO may not have been as predominant a form of variability prior to the 20th
century,
and thus may not be a dominant mode in the future either. I present records of planktonic
17
foraminifera from two-year intervals obtained from annually laminated sediments of the Santa
Barbara Basin to illustrate the importance of both the warming trend in the 20th
century as well
as multiple modes of variability prior to the 20th
century. The 20th
century warming in the
eastern Pacific is characterized by two distinct pulses, which match the global temperature
anomalies: one from 1925 and another around 1977. Prior to the 20th
century, foraminifera
assemblages indicate anomalously cool or warm periods could be accompanied by a shallow or
deep thermocline. These different oceanographic conditions arise not just from expansions and
contractions of the Aleutian Low pressure system (as seen in association with the PDO) but from
shifts in the position of high and low pressure cells, as modified by the jet stream.
HYDROLOGIC RESPONSE TO CLIMATE CHANGE AND
HABITAT RESILIENCY ILLUSTRATED
USING FINE-SCALE WATERSHED MODELING
ALAN L. FLINT (1), LORRAINE E. FLINT (1), ELISABETH MICHELI (2), STUART B.
WEISS (3), AND MORGAN KENNEDY (2)
(1) U.S. Geological Survey, Placer Hall, 6000 J Street, Sacramento, CA 95819
(2) Pepperwood Preserve, Santa Rosa, CA 95404
(3) Creekside Center for Earth Observation, 27 Bishop Lane, Menlo Park, CA 94025
In the face of rapid climate change predictions of landscape change are of great interest to land
and resource managers that endeavor to develop long term plans with the goal of maintaining
biodiversity and ecosystem services, and adapting to extreme changes in the landscape. Climate
models, primarily exhibited as increases in air temperature, often support habitat modeling that
predicts large scale migrations, either northward or up in elevation, or extinctions of sensitive
species. Current studies rely most dominantly on large spatial scale projections (> 10 km) of
changes in precipitation and air temperature that neglect the subtleties of topographic shading,
geomorphic features of the landscape and fine-scale differences in soil properties. Fine-scale
modeling has been tested using climate parameters with improved correlations of vegetation
distribution with temperature. For this study, future climate projections were downscaled to 270-
m and applied to a hydrologic model to calculate future changes in recharge, runoff, and climatic
water deficit for basins draining into the northern San Francisco Bay.
We generated future watershed hydrology scenarios using a coupled climate-hydrology
Basin Characterization Model (BCM) that predicts water cycle fractions of runoff, recharge,
evapotranspiration, and streamflow. Primary BCM inputs consist of topography, soil
composition and depth, parent geology, and spatially-distributed values (measured or estimated)
for air temperature and precipitation. Model calibration is achieved by using historic
precipitation and temperature as BCM inputs and comparing model estimates of discharge with
streamflow measured at gages. Using estimates of future precipitation and air temperature
derived from Global Circulation Models (GCMs) (two models, GFDL and PCM, for two
18
emissions scenarios, A2 and B1) as model input, we describe observed variability over the last
century and estimate watershed-scale hydrologic response to potential climate change scenarios
for approximately the next century. Results indicate large hydrologic variability among
scenarios, increased water deficits, and local scale resiliency of habitats to climate change.
HIGH RESOLUTION CLIMATE PROJECTIONS AND THEIR USE IN IMPACTS AND
ADAPTATION ASSESSMENTS IN CALIFORNIA
GUIDO FRANCO
California Energy Commission, 1516 Ninth Street, Sacramento, CA 95814
In 2003 the California Energy Commission‘s Public Interest Energy Research (PIER) Program
adopted a strategy to produce climate projections for California at adequate spatial and temporal
resolutions for both research and long-term planning. The long-term strategy also included the
goal of generating ―probabilistic‖ climate projections for California (Franco et al., 2003). Since
then, all the steps included in that strategy have been implemented such as: 1) development of
climate scenarios for two California Assessments, 2) development and testing of a new statistical
downscaling technique designed to simulate daily events, 3) development of a technique to
translate multiple projections into ―probabilistic‖ distributions, 4) enhancement of three dynamic
regional climate models and simulations of historical conditions, 5) development of a protocol
to inter-compare dynamic and statistical downscaling techniques, 6) inter-comparison of
dynamic and statistical regional climate models for California, and, 7) estimation of the
probability of future global climate forcing using expert elicitation techniques. This presentation
will briefly discuss the lessons learned from scientific and resource management perspectives
and will present preliminary ―probabilistic‖ climate projections for California.
Franco, G., Wilkinson, R., Sanstad, A., Wilson, M., and Vine, E., 2003, PIEREA Climate Change Research,
Development and Demonstration Plan. California Energy Commission. Publication Number: 500-03-
025FS.
19
ABOVE-TREELINE LINANTHUS PUNGENS SHRUB-CHRONOLOGIES ON THE
EASTERN SIERRA NEVADA CREST, MONO COUNTY, CALIFORNIA CONTAIN
RECORDS OF PRECIPITATION AND TEMPERATURE
REBECCA S. FRANKLIN (1), MALCOLM K. HUGHES (1)
AND CONSTANCE I. MILLAR (2)
(1) Laboratory of Tree-Ring Research, University of Arizona, AZ 85721
(2) U.S. Forest Service, Pacific Southwest Research Station, Albany, CA 94710-0011
Herb- or shrub-chronology, a technique adapted from dendrochronology, is the study of the
annual growth rings in roots of certain perennial dicotyledonous plants. The presence of annual
growth increments in high-elevation plants is significant as it highlights the importance of
herbchronology for climatic, ecological, and geomorphologic applications in alpine and extra-
arboreal regions. For an above-treeline site on the eastern crest of the Sierra Nevada range at the
Barney Lake rock glacier (BLRG) (37.56466N, 118.96554W), I will discuss the
dendrochronological potential of several species colonizing this rock glacier with a focus on the
ring-width chronology and climate response of the species Linanthus pungens (Torr.) J.M. Porter
& L.A. Johnson. Commonly known as Granite Gilia, this species is a low-branching shrub (10-
20 cm high) native to California and is found throughout the arid mountainous western U.S. and
British Columbia at elevations ranging from 1,500–3,700 m. The BLRG chronology is 112 years
in length with signal strength of EPS > 0.85 from 1952 through 2008. In an exploration of the
BLRG chronology, I will present an analysis of correlations with PRISM climate data, SNOTEL
April snow water equivalent, Palmer Drought Severity Index, Multivariate ENSO Index , Pacific
Decadal Oscillation and local climate station temperature and precipitation records and the
potential for climate reconstructions using L. pungens.
20
THE PALEOCLIMATE POTENTIAL AND ENIGMA OF LAGUNA MINUCUA,
OAXACA, MEXICO
MICHELLE GOMAN (1), CHARLOTTE PEARSON (2), WILLIAM GUERRA (1),
ARTHUR JOYCE (3), AND DARREN DALE (4)
(1) Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY 14853
(2) Cornell Tree Ring Laboratory, Cornell University, Ithaca, NY 14853
(3) Department of Anthropology, University of Colorado at Boulder, CO 80309
(4) Cornell High Energy Synchrotron Source, Cornell University, Ithaca, NY 14853
Despite over 50 years of paleoecological and paleoclimatological research the climate history of
much of Mexico remains poorly understood. To some extent this is caused by the difficulty of
deconvolving the long history of human impacts to the natural environment from natural climate-
driven forcings. Further, research has tended to focus on two key regions within Mexico (central
Mexico and the southern Maya lowland region) in part driven by the availability of suitable
sedimentary archives but also because of these regions well known and popular cultural history
(i.e. the Aztecs and Maya, respectively). However, this focus has resulted in an incomplete
understanding of paleoclimate changes, particularly in tropical western Mexico, the purported
location of Zea mays domestication. In order to address this data gap we undertook an extensive
field research campaign in the summer of 2008 in the lowlands and highlands of Oaxaca and
Guerrero, Mexico with the aim of locating suitable archives for paleoenvironmental
reconstructions. The field season was highly successful with nine lacustrine and wetland sites
cored and two locations sampled for dendrochronological analysis.
We present preliminary data from Laguna Minucua, located within the Sierra Madre del
Sur at an elevation of ~2,500 m. Laguna Minucua is a small (~0.25 ha), shallow (< 30 cm deep
at time of coring) pond with no apparent inlets or outlets; it appears to have formed from a
carbonate sink hole but this is not verified. The site is surrounded on the northwest side by a
calcareous ridge, which has stands of Pinus oaxacana and Quercus spp. growing on the slope.
We retrieved two sediment cores from the site (3.5 m and 5.6 m long). Surprisingly, given the
shallow water depth, the cores are well- laminated and possibly varved.
Here we present a preliminary analysis of the observed laminae using a combination of
high resolution synchrotron and scanning XRF data, magnetic susceptibility data, and micro-
morphological characterization from thin sections. We discuss the possible implications of this
for the chronology for the site.
21
MONSOON PRECIPITATION RECONSTRUCTED FROM TREE RINGS IN THE
SOUTHWESTERN UNITED STATES
DANIEL GRIFFIN (1,2), CONNIE A. WOODHOUSE (1,2), DAVID M. MEKO (1), RAMZI
TOUCHAN (1), STEVEN W. LEAVITT (1), CHRISTOPHER L. CASTRO (3), CARLOS M.
CARILLO (3), AND BRITTANY CIANCARELLI (3)
(1) Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ 85721
(2) School of Geography and Development, University of Arizona, Tucson, AZ 85721
(3) Department of Atmospheric Sciences, University of Arizona, Tucson, AZ 85721
The North American monsoon system, emanating northward from Mexico during the warm
season, delivers up to 60% of the annual precipitation to the southwestern United States
(SWUS). The SWUS, however, is predominately on the fringe of monsoon influence, and warm-
season precipitation across the region is highly variable on annual to decadal time scales.
Interannual monsoon moisture variability, a key factor influencing summer water demand and
ecosystems in the SWUS, has been the focus of extensive research in recent decades. While tree
rings have revealed much about the long-term hydroclimatic history of this region‘s westerly-
driven winter climate regime, no dendroclimatic studies have systematically targeted the
monsoon across the SWUS. Our group is developing the region‘s first network of monsoon-
sensitive chronologies, focusing on variability in the latewood (summer growth) of precisely
dated tree rings from some 50 sites. This study describes the relationship between warm-season
precipitation and tree-growth from sites across the SWUS and presents the first tree-ring
reconstruction of monsoon (July-August) precipitation for southeastern Arizona and
southwestern New Mexico. The 350-year reconstruction, which explains over 55% of the
variance in the instrumental record, reveals severe and persistent monsoon droughts, including
several that coincided with sustained dryness in the cool season. None of the sustained cool
season droughts of this period appear to have been offset by persistently wet monsoons, and the
widely discussed tendency for cool season dry (wet) extrema to be followed by wet (dry)
monsoons seems to have been most consistent during the late 20th century.
http://monsoon.ltrr.arizona.edu
22
THE TIMING OF MULTI-DECADAL DROUGHT SIGNALS RECORDED IN THE
ELEMENTAL COMPOSITION OF SANTA BARBARA BASIN SEDIMENTS
INGRID L. HENDY (1), LARIANNA DUNN (1), AND ARNDT SCHIMMELMANN (2)
(1) Department of Geological Sciences, University of Michigan, MI 48109
(2) Department of Geological Sciences, Indiana University, Bloomington, IN 47405
Santa Barbara Basin (SBB) is renowned for high quality paleoclimate records due to an
extremely high sedimentation rate, high biological productivity, and suboxic bottom waters that
preserve annually laminated, anoxic sequences. Here we extend an annually resolved high-
resolution paleoclimate record back 1,800 years. XRF analysis of Si, S, Ti, and Ca at 200 µm
intervals on the upper 65 cm of box core SPR0901-4BC and overlapping sections of kasten core
SPR0901-03KC (275 cm) were conducted using an ITRAX core scanner, equipped with a Cr-
tube. Core sections were spliced together between instantaneous sedimentation events (turbidites
and flood deposits) to provide a continuous sedimentary record with a resolution of four to eight
counts per year. High resolution 14
C dating on planktonic foraminifera was completed on
SPR0901-06KC (255 cm) at 5 cm intervals. Two preliminary age models were generated by
removing instantaneous sedimentation events from the sequence and generating ages using a
linear interpolation between (1) sedimentary events dated by previous varve chronology studies,
and (2) the same events dated by the newly calibrated 14
C datum. Ti counts relate to the relative
contribution of lithogenic to biogenic components in SBB sediments. Low Ti counts indicate
little riverine detrital input during drought conditions, while high counts suggest increased river
discharge with high associated lithogenic components. During the 20th
century high Ti count
years correlate with El Niño and positive PDO years. Multi-decadal low Ti count intervals exist
between A.D. 1110-1180, 1290-1320, 1530-1550, and 1740-1760 based on varve chronology
suggest earlier drought conditions far more severe that occurring during California‘s written
history. The multi-decadal droughts may have been widespread as these intervals correlate with
droughts suggested by the Cariaco Basin, Venezuela runoff record. Yet based on the 14
C derived
chronology, these mega droughts shift to A.D. 790-810, 990-1080, 1195-1230, 1470-1505, and
1700-1720 and subsequently occur during wet intervals recorded in Cariaco Basin. Resolution of
dating issues is vital if we are to understand the climate mechanisms, which produced these
multi-decadal droughts.
23
LINKS BETWEEN SOUTHERN CALIFORNIA CURRENT VARIABILITY AND
NORTHERN HEMISPHERE TEMPERATURES: THE PAST MILLENNIUM
JUAN CARLOS HERGUERA (1), P. GRAHAM MORTYN, (2,3),
AND MIQUEL ÀNGEL MARTÍNEZ-BOTÍ (2)
(1) División de Oceanología, Centro de Investigación Científica y de Educación
Superior de Ensenada (CICESE), México
(2) Institute of Environmental Science and Technology (ICTA),
Universitat Autonoma de Barcelona, Spain
(3) Geography Department, Universitat Autonoma de Barcelona, Spain
Instrumental sea surface temperature (SST) variability of the California Current System (CCS)
for the last century is thought to be modulated by interannual to interdecadal oscillations
superimposed on a background warming trend. However, our understanding of the amplitude of
multidecadal SST changes over the last millennium, its persistence through time, and drivers
before the instrumental record are still not well characterized. Here we present an absolutely-
dated and decadally-resolved planktonic foraminiferal Mg/Ca reconstruction of summer SSTs in
the southern dynamic boundary of the CCS for the past millennium to explore the links between
this eastern boundary current, Northern Hemisphere (NH) temperatures end equatorial ocean
dynamics. Summer SST variability is inversely linked with continental NH temperatures on
multidecadal timescales and directly linked with the Equatorial Pacific ocean dynamics until the
19th
-20th
century, when continental NH temperatures become the dominant driver. This inverse
pattern is best explained by the seasonal ocean-land temperature contrast during the spring to
early summer warming process that enhances the ocean-continent pressure gradient and drives
the persistent alongshore winds, and upwelling processes on multidecadal timescales. However,
this pattern seems to reverse during the last third of the 20th
century with a trend towards warmer
SSTs, probably associated with a cloud cover reduction over the northeast Pacific, that leads to
increased SSTs, a weaker subtropical high and a lessening of the trade winds as a positive
feedback for further warming in response to increased atmospheric greenhouse gases.
24
OCCURRENCE OF SEVERE DROUGHT CONDITIONS IN COASTAL SOUTHERN
CALIFORNIA DURING THE MEDIEVAL CLIMATE ANOMALY INFERRED FROM
POLLEN DEPOSITED IN THE
SANTA BARBARA BASIN SINCE ~ A.D. 800
HEUSSER, LINDA (1), BARRON, JOHN (2), AND HENDY, INGRID (3)
(1) Lamont Doherty Earth Observatory, Palisades, NY 10964
(2) U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025
(3) Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109
Pollen analyses of the upper 3.95 m from ODP Site 893B from the Santa Barbara Basin (SBB)
provide proxy evidence for major climate-driven changes in the vegetation onshore between ~
A.D. 800 and A.D. 1800. Dominance of plant communities adapted to drought conditions of hot,
dry southern California summers (chamise chaparral and coastal sage scrub) corresponds with
increases in the duration and severity of western U.S. drought identified by Stine (1994) and
Cook et al. (2004) and with MacDonald and Case's (2005) interpretation of more negative
Pacific Decadal Oscillation variability during the Medieval Climate Anomaly. Extreme drought
conditions occur during a period of multi-decadal drought recorded by the high resolution-Ti
record between A.D. 1000-1100 (14
C corrected) (Hendy et al., 2011). The shift toward wetter,
cooler conditions at ~ A.D. 1400 (an increase in more mesic oak and pine communities such as
scrub oak and pine woodland chaparral, or more open grass woodland) coincides with
temperature changes in the waters offshore. Correlative diatom and planktonic foraminifera
deposited in the SBB during the Little Ice Age suggest increased seasonal sea surface
temperature changes with cooler winters and warmer springs, respectively (Barron et al., 2010;
Fisler and Hendy, 2008). The distinctive signature of the 19th
and 20th
century pollen
assemblages reflects agricultural and residential impact on the natural vegetation of southern
coastal California following European settlement.
Barron, J., Bukry, D., and D. Field, 2010, Santa Barbara Basin diatom and silicoflagellate response to global climate
anomalies during the past 2200 years: Quaternary International, v. 215, p 34-44.
Cook, E., Woodhouse, C., Eakin, M., Meko
, D.M., Stahle, D.W., 2004, Long-term aridity changes in the western
United States Science v. 306 n. 5698, p. 1015-1018.
Fisler, J. and Hendy, I., 2008, California Current System response to late Holocene climate cooling in southern
California: Geophysical Research Letters, v. 35, L09702.
Hendy, I.L., Dunn, L., and Schimmelmann, A., 2011, The timing of multi-decadal drought signals recorded in the
elemental composition of Santa Barbara Basin sediments: Abstracts of the 25th
Pacific Climate Workshop,
Asilomar, California, March 6-9, 2011.
MacDonald, G. M. and Case, R.A., 2005, Variations in the Pacific Decadal Oscillation over the past millennium:
Geophysical Research Letters, v. 32, n. 8, L08703.
Stine, S., 1994, Extreme and persistent drought in California and Patagonia during mediaeval time: Nature, v. 369,
n. 6481, p. 546-549.
25
TWENTY-FIVE YEARS OF CO-EVOLUTION OF DENDROCLIMATOLOGY
AND PACLIM
MALCOLM K. HUGHES
Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ 85721
Referring to the late 1970s, Hughes et al. (2011) recently wrote that ―From today’s viewpoint, it
is difficult to imagine how little was known about interannual- to century-scale variability in the
climate system at that time, with published sketches of the spectrum of climate variability
exhibiting little or no power between bidecadal and millennial frequencies‖. The first of what
became the PACLIM multidisciplinary workshops was held at Asilomar just a few years later in
1984. The scientific programs of these workshops track a rapid evolution of understanding of the
climate system on time-scales of relevance to society, the landscape, the oceans and ecological
systems. The pioneering dendroclimatological work of Harold Fritts, dealt with geographic and
time domains of interest to PACLIM. In the past 25 years, Fritts‘ contributions have been built
upon by his students and colleagues. Not only has this approach been expanded to cover much of
the globe, and enhanced to provide more process-based understanding of climate and its impacts,
but it has provided an example of the multidisciplinary approach so characteristic of PACLIM.
Drought, streamflow, fire climatology, circulation indices, and extreme climatic events have all
figured in the contributions dendroclimatology has made to understanding of the climate system
and its interactions with society, the biosphere, and the geosphere over the Pacific-Western
Americas domain.
Hughes, M.K., Swetnam, T.S., and Diaz, H.F., editors, 2011, Dendroclimatology: Progress and Prospects: Springer,
Dordrecht, xii + 365 pp.
26
ENVIRONMENTAL AND BIOTIC CHANGE AT THE NANODIAMOND DATUM: THE
YOUNGER DRYAS BOUNDARY IMPACT HYPOTHESIS
JAMES KENNETT (1), ALLEN WEST (2), DOUGLAS KENNETT (3), CHARLES KINZIE
(4), AND WENDY WOLBACH (5)
(1) Department of Earth Science, University of California Santa Barbara,
Santa Barbara, CA 93106
(2) Geosciences Consulting, Dewey, AZ 86327
(3) Department of Anthropology, University of Oregon, Eugene, OR 97403
(4) Department of Chemistry, De Paul University, Chicago, IL 60614
(5) Department of Chemistry, De Paul University, Chicago, IL 60614
The onset of the Younger Dryas (YD) cool episode is marked by a diverse assemblage of
abundant nanodiamonds at the YD boundary layer (YDB) that forms a widely correlated datum
across North America and Western Europe. This evidence is consistent with a high-temperature
cosmic impact event at 12,900 +/- 100 cal yr B.P. The YDB is marked by a complex and broad
array of abrupt and potentially linked changes in atmospheric and oceanic circulation, ice sheets,
North American continental hydrosphere, the biosphere including extinctions, and human
adaptations, and possible population reductions and reorganization. The cause of the YD is
controversial and currently debated, yet any causal hypothesis needs to account for these
changes. We will review and challenge recent contributions that have questioned evidence for an
impact event at the YD onset. Younger Dryas cooling is enigmatic in its timing, magnitude and
abruptness at near-peak insolation. Such cooling episodes with YD characteristics and timing in
earlier terminations appear more affiliated with terminal glacial episodes. Younger Dryas onset is
also outstanding because of close collective association with major, abrupt continental-scale
ecological reorganization, megafaunal extinction, and human adaptive and population change.
Climate change at the YD onset was remarkably abrupt (~one year) suggesting
atmospheric climate response preceded oceanic change. A major North American hydrographic
reorganization, apparently associated with destabilization of ice sheet margins, was marked by
abrupt switch in flow from the south to northern oceans. This outburst flooding may have
coincided with major drainage of Lake Agassiz. Associated outburst floods affected widely
separated areas of the Arctic. The most pronounced oceanic effect was change in meridional
overturning.
Major responses recorded in temperate environments include widespread evidence of
biomass burning, changes in sediment deposition including a layer with diverse exotic materials
interpreted to be of cosmic impact origin, broad continental vegetation disruption, abrupt
megafaunal extinction, and genetic bottlenecks reflecting population declines and/or animal
migrations. The North American human record suggests abrupt disappearance of the Clovis
27
culture, a human genetic bottleneck, and a widespread archeological gap during the early
centuries of the YD cooling episode.
EFFECTS OF BASELINE CONDITIONS ON THE SIMULATED HYDROLOGIC
RESPONSE TO PROJECTED CLIMATE CHANGE: A CASE STUDY OF THE
ALMANOR CATCHMENT, NORTH FORK OF THE FEATHER RIVER BASIN,
CALIFORNIA
KATHRYN M. KOCZOT (1), STEVEN L. MARKSTROM (2),
AND LAUREN E. HAY (2)
(1) U.S. Geological Survey CAWSC, 4165 Spruance Road, Suite 200, San Diego, CA 92101
(2) U.S. Geological Survey, Box 25046, Federal Center Mail Stop 412, Denver, CO 80225
[email protected], [email protected]
The hydrologic response to changes in 21st century climate was evaluated for the Almanor
Catchment in the North Fork of the Feather River basin, California. Changes in temperature and
precipitation projected from five general circulation models using one late 20th
century and three
21st century emission scenarios were downscaled to three different baseline conditions. Baseline
conditions are periods of measured temperature and precipitation selected from 20th
century data,
and used to represent historical climate. The three baseline conditions were selected to represent
a drier-than-average climate cycle, an average-to-wetter climate cycle, and a wetter-than-average
climate cycle. The hydrologic effects of the climate projections are simulated by using the
Precipitation Runoff Modeling System (PRMS), which is a watershed hydrology model.
Hydrologic components (i.e. snowpack formation and melt, evapotranspiration, and
streamflow) from the PRMS simulations are compared. Results indicate that, when the study
area displays climate with highly variable cycles, the selection of a specific period used to
represent baseline conditions has a substantial effect on the simulation of some, but not all,
hydrologic variables. This effect seems to be amplified in hydrologic variables that accumulate
over time, such as soil-moisture content. Furthermore, the uncertainty associated with baseline
conditions should be evaluated by using a range of different baseline conditions representative of
the climate of the basin of interest. This is particularly important for studies in basins with highly
variable climate, such as the Almanor Catchment.
28
FIRE HISTORY IN THE EASTERN UINTA MOUNTAINS, UTAH, USA
REBECCA KOLL (1,2) AND MITCHELL J. POWER (1,2)
(1) Department of Geography, University of Utah, Salt Lake City, UT, 84112
(2) Utah Museum of Natural History, University of Utah, Salt Lake City, UT 84112
A 2.1-meter-long sediment core from the eastern Uinta Mountains provides a 10,600-year-long
record of vegetation change and fire history. Few studies have explored the long-term vegetation
and disturbance history from the Uinta Mountains. As a result, significant gaps remain in
understanding historical processes affecting biodiversity from this region. The charcoal-based
fire history reconstruction from Reader Fen (3,205m a.s.l.) suggests fires occurred on average
every 400 years during the last 10,600 years. A previously published pollen-based vegetation
history (Carrara et al., 1985) near Reader Fen suggests subalpine forest species (e.g. Picea
engelmannii and Pinus contorta) arrived in the Uinta Mountains soon after glaciers retreated
(7,500 cal yr B.P.). From ~5,500 to 2,500 cal yr B.P., arboreal species increased in high-
elevation forests and fires occurred. During the last 500 years, and particularly during the last
century, fire frequency has increased. This long-term perspective suggests fire activity has
increased in high-elevation forests during the historical period (Agee and Skinner, 2005; Long,
2003). Understanding the frequency and magnitude of past disturbances is necessary for
understanding the catalyst of vegetation change and for making informed management decisions
on present and future ecological change in the Uinta Mountains.
Agee, J.K. and Skinner, C.N., 2005, Basic principles of forest fuel reduction treatments: Forest Ecology and
Management, v. 211, p. 83–96. Carrara, P.E., Short, S.K., and Shroba, R.R., 1985, A pollen study of Holocene peat and lake sediments, Leidy Peak
area, Uinta Mountains, Utah: Brigham Young University Geology Studies, v. 32, n. 1, p. 1-7. Long, J.N., 2003, Diversity, complexity and interactions: an overview of Rocky Mountain forest ecosystems: Tree
Physiology, v. 23, p. 1091–1099.
EL NIÑO IN THE HOLOCENE AND LAST GLACIAL MAXIMUM
ATHANASIOS KOUTAVAS
Department of Engineering Science and Physics, College of Staten Island, City
University of New York, Staten Island, NY 10314
The El Niño-Southern Oscillation (ENSO) is a major influence in the global climate and a source
of uncertainty in future regional climate responses including prominently those over western
North America. To better understand ENSO sensitivity, modes of variability, and the strength
and stability of its teleconnections, it is important to reconstruct past ENSO activity at its source
region – the equatorial Pacific. Efforts toward paleo-ENSO reconstructions have had limited
success because they have relied mostly on fossil corals which are short-lived and discontinuous,
29
or land archives (tree-rings and lake sediments) which assume stable atmospheric
teleconnections. In this work I have taken an alternative approach, which utilizes individual
planktonic foraminifera from marine sediments accumulating in the Galapagos region, a hotspot
of ENSO activity. The oxygen isotope composition of foraminiferal calcite records the
anomalous warming and freshening that occurs during El Niño (opposite for La Niña). Because
each foraminifer lives for only a few weeks to a month, its chemistry provides a short snapshot
of sea surface conditions that resolves the ENSO timescale despite the slower accumulation rate
of the sediment within which it is embedded. Analysis of multiple co-occurring individuals can
reveal the total variance within a sample, reflecting the seasonal and interannual ENSO
variability. We have conducted over 2,000 individual analyses in the Holocene and LGM
sections of a core from the Galapagos and resolved highly significant changes in variance.
Minimum variance is observed in the middle Holocene approximately 6,500-4,000 years ago,
while maximum variance occurred in the LGM. While these variance estimates incorporate both
ENSO and seasonal effects, additional constraints suggest they are primarily driven by ENSO
modulation. The middle Holocene ENSO suppression evident in these data matches the timing of
western U.S. droughts inferred from lake records, suggesting ENSO has had a profound
influence on North American climate over the Holocene.
HAWAIIAN FOREST BIRDS: THE PAST, PRESENT AND FUTURE STATUS OF AN
ENDANGERED AVIFAUNA
DENNIS A. LAPOINTE (1), CARTER T. ATKINSON (1), PAUL C. BANKO (1), RICHARD
J. CAMP (2), P. MARCOS GORRESEN (2) , JAMES D. JACOBI (1), THANE K. PRATT (1),
AND MICHAEL D. SAMUEL (3)
(1) U.S. Geological Survey, Pacific Island Ecosystems Research Center, Kilauea Field Station,
Hawai’i Volcanoes National Park, HI 96718
(2) Hawai‘i Cooperative Studies Unit, Pacific Aquaculture and Coastal Resources Center,
University of Hawai‘i at Hilo, HI 96720
(3) U.S. Geological Survey, Wisconsin Cooperative Wildlife Research Unit, University of
Wisconsin, Madison, WI 53706
The Hawaiian forest birds are among the most endangered avifauna of the world. Entire bird
groups have disappeared from the Hawaiian Islands, and of the more than fifty, historically-
known species of Hawaiian honeycreeper, only 17 remain. Due to the extreme geographical
isolation, few birds colonized the Hawaiian Islands but, released from direct competition,
predation, and disease, these founders flourished and evolved amid the heterogeneous geography
of the archipelago. This process of colonization and speciation is best characterized by the
honeycreepers; the largest radiation of endemic forest birds in the Hawaiian Islands, or for that
matter, birds on any oceanic archipelago. But this remarkable avifauna has suffered great loses
30
since the arrival of humankind. Extinctions and population declines began with the inadvertent
introduction of predatory rats, overharvesting of flightless species and destruction of lowland
forest by Polynesians. Habitat destruction and degradation and predation accelerated with the
arrival of Westerners and their domestic animals and pests, leading to more extinction and
increasing rates of population decline. The introduction of mosquito vectors, avian disease
pathogens, and vertebrate and invertebrate competitors led to the displacement of many native
bird species from lowland forests. Today, on protected lands, there are apparently stable
populations of only a handful of the remaining species. However, habitat degradation, predation,
disease and food web disruption by invasive hymenoptera continue to impact critical
populations. Additionally, climate change will likely increase habitat degradation, disease, and
food web disruption further restricting remaining populations to smaller and more dispersed
refuges. Although the fate of Hawaiian forest birds appears bleak, there are reasons for hope.
Some populations of Hawaii amakihi have evolved tolerance to avian malaria and are
burgeoning in the once quieted lowland forests. Captive breeding and release programs have
prevented the extinction of at least two species and consortiums of managed conservation lands
increase the extent and suitability of remaining forest bird habitat.
SEVERITY AND FORCING OF DROUGHT IN THE
NORTHWESTERN GREAT PLAINS SINCE 1365
SUZAN L. LAPP, JESSICA R. VANSTONE, JEANNINE-MARIE ST. JACQUES,
AND DAVID J. SAUCHYN
Prairie Adaptation Research Collaborative (PARC), University of Regina,
Regina, SK, S4S 7H9, Canada
[email protected], [email protected], [email protected],
The 20th
century hydroclimatology of the Pacific Northwest has been linked to natural recurring
large-scale climate patterns such as the Pacific Decadal Oscillation (PDO) and the El Niño-
Southern Oscillation (ENSO). Tree-ring proxy data analyses carried out in western North
America have proven valuable to quantify natural climate variation over centuries to millennia.
A reconstruction of PDSI over the western Canadian Prairie region provides a record of drought
for the past 800 years. We are able to mine these long reconstructions for much more
information about the frequency/duration of positive (wet) and negative (dry) moisture
anomalies during difference phases of PDO and ENSO, as reconstructed from tree-ring datasets.
As well, by comparing these moisture reconstructions to temperature reconstructions of the
region we are able to identify warm/cool drought periods. These reconstructions reflect the
seasonal changes in moisture relative to both the instrumental and future time periods. The large-
scale climate patterns will also be derived from multiple GCMs, for the 21st century, as tools to
better understand projections of future moisture variability. Decision makers responsible for
31
adaptation to climate variability and change may use our forecasts of persistent departures from
mean hydroclimate to plan for future climate conditions.
THE LAST 2,000 YEARS OF CALIFORNIA CLIMATE VARIABILITY:
COMPARISON OF SEDIMENT RECORDS OF LATE HOLOCENE PALEOCLIMATE
FROM THE WESTERN UNITED STATES
STEVE LUND (1), LARRY BENSON (2), MATTHEW KIRBY (3), WILL BERELSON (1),
SARAH FEAKINS (1), AND FRANK CORSETTI (1)
(1) Department of Earth Sciences, University of Southern California,
Los Angeles, CA 90089
(2) Department of Anthropology, University of Colorado, Boulder, CO 80309
(3) Department of Geology, California State University, Fullerton, CA 92834
We have recovered late Holocene paleoclimate records from eight sediment sequences in the
California region, which form a transect from northwestern Nevada to Baja California: Pyramid
Lake (Nevada), Walker Lake (Nevada), Mono Lake (California), Owens Lake (California), Santa
Cruz coast (California), Zaca Lake (California), Lake Elsinore (California), Pescadero Basin
(Mexico). The cores are all 14
C dated and correlated with paleomagnetic field secular variation.
Work is just beginning in some records, while other records are fully published. In this study, our
goal is to compare evidence for multi-decadal to millennial-scale climate/environmental
variability among the records and look for regional patterns of variability. Different records have
different degrees of resolution or response, so distinctive patterns in some records are not
expected to be visible in all records. We see clear evidence for centennial- to millennial-scale
variability in these records, but it is not yet clear that we can assign a specific regional pattern to
that variability. Similarly, we see evidence for ENSO to multi-decadal variability in several of
the records, but it is not clear that the same multi-decadal pattern can be correlated across the
region.
32
A SEASON SPECIFIC PALEOCLIMATE RECORD FROM A NORTHERN WASATCH
MOUNTAINS SPELEOTHEM AND LINKAGES TO THE PACIFIC
ZACHARY LUNDEEN (1), ANDREA BRUNELLE (1), STEPHEN J. BURNS (2), YEMANE
ASMEROM (3), AND VICTOR POLYAK (3)
(1) Department of Geography, University of Utah, Salt Lake City, UT 84112
(2) Department of Geosciences, University of Massachusetts Amherst, Amherst, MA, 01003
(3) Department of Earth and Planetary Sciences, University of New Mexico,
Albuquerque, NM, 87131
Pacific Ocean influences on spatiotemporal precipitation variability in the American West are
well documented, especially with respect to El-Niño-Southern Oscillation and the Pacific
Decadal Oscillation. However, the effects of these large-scale teleconnection patterns on
precipitation distribution are most pronounced in the winter, with less noticeable effects the rest
of the year. Linking terrestrial paleoclimate records to past ENSO or PDO variability in the
Pacific Ocean is hampered by the lack of season-specific paleoclimate proxies. Rather than being
able to isolate winter season precipitation amounts, most paleoclimate records are instead more
representative of mean annual effective moisture conditions. We present an isotope-based
paleoclimate record from a speleothem in the Bear River Range, the northernmost extension of
the Wasatch Mountains. Due to the location‘s characteristics, we interpret the speleothem stable
isotope data as a record of winter precipitation amount and temperature variability. The record
shows a generalized pattern of wet early Holocene conditions, a dry middle Holocene, and a wet
neoglacial period. Significant droughts occurred from ~6,200-7,200 cal yr B.P., and at ~4,200 cal
yr B.P. Temperatures were generally cool in the early Holocene and show a consistent warming
trend through the middle Holocene. Anthropogenic warming is evident in the record, with
modern oxygen isotope delta values more than two standard deviations above the Holocene
mean.
DECICPHERING THE ROLE OF CLIMATE- VERSUS HUMAN-CAUSED
DISTURBANCE DURING THE 19TH
AND 20TH
CENTURY: A COMPARISON OF
ISOTOPIC, STOICHOIMETRIC, POLLEN, AND PLANT MACROFOSSILS FROM
TWO LAKES IN THE WESTERN U.S.
ANTHONY N. MACHARIA AND (1), AND MITCHELL J. POWER (1,2)
(1) Department of Geography, University of Utah, Salt Lake City, UT 84112
(2) Utah Museum of Natural History, University of Utah, Salt Lake City, UT 84112
Historical paleoenvironmental interpretations of biotic and abiotic processes in lake sediment
records are complicated by recent anthropogenic activities. To disentangle the role of climate
versus people in 19th
and 20th
century lake sediment records we use sedimentary elemental and
33
stable isotopes, plant macrofossils, charcoal and pollen records. Ecological effects of climatic-
versus anthropogenic disturbances are compared for two lakes in the Western U.S. (Utah Lake
(48 10‘N, 114 21‘W) and Foy Lake (40° 13.82'N, 111° 47.12'W). Trends in bulk sediment δ15
N
values were most effective in distinguishing the relative role of climate versus anthropogenic
activity as the dominant mechanism of ecosystem disturbance. In the organic-rich Foy Lake
sediments, influxes of allochthonous materials generated significant shifts in δ13
C, and C:N
ratios while the δ15
N values and charcoal records show the most dramatic shifts in Utah Lake.
The disturbance from late 19th
century sawmill operations and widespread forest fires were
responsible for the observed shifts in Foy Lake, while agricultural activities, urban development,
and 20th
century variations in Utah Lake hydrology help explain trends in Utah lake sediments.
Changes in pollen and macrofossil composition in Utah Lake reinforce these interpretations.
Observed differences in sedimentary δ18
O at both lakes reflect the contrasting climatological and
hydrological settings of the two basins. These results demonstrate that the influx of nutrients and
particulate organic matter from natural and anthropogenic sources produce dramatic changes in
sedimentary geochemistry. Using multiple tools for interpreting past environmental change in
lake systems can help decipher natural versus anthropogenic drivers.
PACIFIC OCEAN SEA SURFACE TEMPERATURE INFLUENCE ON
SOUTHWESTERN UNITED STATES CLIMATE DURING THE PAST MILLENNIUM:
NEW EVIDENCE FROM A WELL-CALIBRATED, HIGH-RESOLUTION
STALAGMITE δ18
O RECORD FROM THE SIERRA NEVADA, CALIFORNIA
STARYL E. MCCABE-GLYNN (1), KATHLEEN R. JOHNSON(1), MAX B.
BERKELHAMMER (2), ASHISH SINHA (3), H. CHENG (4,5),
AND LARRY EDWARDS (5)
(1) Department of Earth System Science, University of California, Irvine, CA 92696
(2) Cooperative Institute for Research in Environmental Sciences,
University of Colorado, Boulder, CO 80309
(3) Earth Sciences Department, California State University, Dominguez Hills, Carson, CA 90747
(4) Institute of Global Environmental Change, Xi’an Jiaotong Univ., Xi’an, Shaanxi, China
(5) Department of Geology and Geophysics, University of Minnesota,
Minneapolis, MN 55455
Proxy data from tree-rings and lake sediments indicate that past droughts in the southwestern
U.S. were of greater magnitude and longer duration than the 20th
century droughts. To determine
the natural range and mechanisms of past hydrologic variability in the southwestern U.S., we are
using speleothems from Crystal Cave in Sequoia National Park, California, on the southwestern
flank of the Sierra Nevada (36.58°N; 118.56°W; 1,540 m), to develop a well-dated, high
resolution (near-annually resolved) oxygen isotope record of past climate. We have conducted an
instrumental calibration study using a 10.5 cm stalagmite, CRC-3, that formed over the past
1,000 years until it was collected in 2008. Initial results suggest that speleothem, and hence
34
rainfall, δ18
O at this site is not correlated to temperature or precipitation amount, but is strongly
influenced by the moisture source and rainout history of landfalling storms, in agreement with a
recent isotope-enabled GCM study (isoGSM). A comparison between the instrumental portion of
the CRC-3 timeseries reveals a strong inverse relationship with the PDO index, indicating that
speleothem δ18
O at this site is highly sensitive to Pacific Ocean SST patterns. The CRC-3
timeseries (A.D. 957 to 2008) exhibits a prominent decadal to multidecadal scale variability
which we infer to reflect the influence of changing SST's on the precipitation patterns in the
southwestern U.S. Here we present a comparison of this record with existing proxy records of
SST, drought, and precipitation variability over the last millennium.
LATEST QUATERNARY PALEOCEANOGRAPHIC CHANGES ON THE
FARALLON ESCARPMENT OFF CENTRAL CALIFORNIA
MARY MCGANN
U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025
A suite of climate proxy data (benthic and planktic foraminiferal assemblage census counts,
Benthic Foraminiferal Oxygen Index (BFOI) values, and total carbon, organic carbon, and
calcium carbonate analyses of sediments) coupled with previously published data (stable
isotopes and Ca/Cd) from off central California on the Farallon Escarpment (1,605 m; 37°13.4'N,
123°14.6'W; core F-8-90-G21) are used to investigate paleoceanographic changes from the last
glacial maximum to the late Holocene. A Q-mode cluster analysis divided the planktic fauna into
Pleistocene and Holocene clusters whereas the benthic fauna was separated into three clusters,
one Pleistocene and two Holocene. Stable oxygen isotope values show an increase in water
temperature of ~1°C from the late glacial to late Holocene, which is supported by a change in
faunal composition of the planktic assemblage suggesting warmer surface waters. A general
trend of decreasing dissolved oxygen concentration from the Pleistocene (well oxygenated; 3.0-
6.0+ ml/L O2) to the Holocene (poorly oxygenated; 1.5-3.0 ml/L O2), reflecting decreased
ventilation, is evident in the BFOI data and agrees with the Cd/Ca data except for an increase
between ~13,000-11,000 cal yr B.P. when ventilation briefly improved. Middle Holocene
cooling, suggested in other central and northern California margin studies, is not evident in F-8-
90-G21, which compares more favorably with studies from southern California and British
Columbia. Total carbon and organic carbon values are highest in the Bølling-Allerød, early
Holocene, and late Holocene. Similarly, calcium carbonate values are high in the Bølling-
Allerød and peak in the early Holocene, but decrease significantly in the latest middle and late
Holocene which coincides with a depauparate planktic fauna in the upper 60 cm (~7,000-0 cal yr
B.P.) of the core and poor preservation of the benthic fauna at and above 40 cm (~3,000-0 cal yr
B.P.). The depauparate faunas are thought to be biologically, not taphonomically, controlled
because the abundance of planktic foraminifera remains low today in waters off central
California. Decoupling of the planktic and benthic faunal response to changing climatic
35
conditions is evident, with the surface-dwelling assemblage often leading the bottom-dwelling
assemblage by several millenia.
A 9,700-YEAR MULTI-PROXY RECONSTRUCTION OF HYDROLOGIC AND
VEGETATION HISTORY FROM A LOW-ELEVATION SPRING-FED MEADOW,
EAST CENRAL NEVADA
SCOTT MENSING (1) AND SAXON E. SHARPE (2)
Department of Geography, University of Nevada, Reno, NV 89503
Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512
A ~9,700-year-old 7-m-long sediment core obtained from Stonehouse spring in the Spring
Valley in east-central Nevada (White Pine County) contains a unique record because 1) springs
are not commonly cored for paleoenvironmental data so this project shows that springs can
produce viable long-term hydrologic histories, 2) little is known about past biologic and
hydrologic variability in the Spring Valley area so these cores provide the first
paleoenvironmental record at this locality, 3) sediments date to the early Holocene, a relatively
long and high resolution record, 4) springs are often biodiversity hot spots and the sole habitat
for many spring-dwelling species, and 5) springs are closely associated with physiochemical
characteristics of groundwater systems which are usually fed by climate. Thus, spring sediments
can provide long-term biologic, hydrologic, and climatic information. This project uses pollen,
mollusks, diatoms, and chironomids from the core (elevation 1,914 m) to evaluate past
hydrology and climate. Evaluating the hydrologic and climate history of this area is important
because 40,000 to 60,000 acre-feet of groundwater are planned to be pumped from Spring Valley
by the Southern Nevada Water Authority, the owner of Stonehouse spring.
Preliminary results from pollen show low pollen accumulation rates, supporting the
suggestion of high sedimentation rates associated with generally high meadow productivity.
Preliminary results from mollusks recovered from the core show time intervals with no mollusks,
intervals with mixed aquatic and terrestrial mollusks, and intervals with spring-obligate
mollusks. Periods with mollusks are associated with clay rich sediments and low percent
organics, suggesting standing water. Future work includes additional radiocarbon dates, analysis
of ostracodes and diatoms, and the integration of these paleohydrologic and paleoclimatic proxy
data with other records to determine both the long-term hydrologic variability of Stonehouse and
how well hydrology and climate are linked at this location.
36
THERMAL AND HYDROLOGIC ATTRIBUTES OF ROCK GLACIERS AND
RELATED LANDFORMS IN THE SIERRA NEVADA, CALIFORNIA:
FIVE YEARS OF iBUTTON RECORDS
CONSTANCE I. MILLAR, ROBERT D. WESTFALL, AND DIANE L. DELANY
Pacific Southwest Research Station, U.S. Forest Service, Albany, CA 94710
[email protected], [email protected], [email protected]
Over the past five years we have deployed iButton thermochrons in and around environments of
rock glaciers and related landforms (boulder streams and talus) of the eastern Sierra Nevada. Our
goal has been to explore thermal regimes and hydrologic capacity of these little-known features.
Whereas we have reported individual results at previous PACLIM Workshops, and while we
await results from an ongoing intensive study, we take this opportunity to synthesize consistent
trends that have emerged from the iButton records. We propose ―active‖ Sierran features to have
attributes that include:1) persistent water in outlet streams through the year (frozen in winter), 2)
mean outlet stream temperatures < 0°C (annual) and < 2°C (summer), 3) mean annual
temperature of air in the rock matrix 1 m below the surface -1°C, 4) matrix summer temperatures
highly attenuated relative to surface temperatures, 5) lapse rates mostly negative in summer
within the matrix environments, and no obvious trend in winter when features are snow-covered,
and 6) floristically diverse wetland communities or persistent water bodies at the forefront. From
these trends, we hypothesize active landforms to contain embedded ice that is the source of
persistent and cold outlet streams, and that supports adjacent wetlands or lakes. Karst ponds that
develop on some rock glaciers reveal stratified ice (to ~10 m depth), suggesting sedimentary
(glaciogenic) origin. Whether all ice in active features forms this way or whether some features,
especially active boulder streams and taluses, develop ice lenses from permafrost origin is
unknown. We propose ―inactive‖ features to have attributes that include: 1) outlet streams often
missing or dry by late summer or fall, especially in drought years, 2) mean outlet stream
temperatures 1-3°C (annual) and 4-8°C (summer), 3) mean annual temperature of air in the rock
matrix 5-7°C, 4) attenuated matrix summer temperatures relative to surface, 5) strongly positive
summer lapse rates within features in the matrix, and negative lapse rates in winter, the latter
appearing more correlated with persistent snowpack at the base than elevation within the feature,
and 6) forefields of drier meadow communities and shrublands and lakes rarely present. Internal
thermal conditions of inactive and active rock matrices have complex seasonal patterns relative
to surface temperatures. For instance during early spring, temperature profiles suggest that
melting snow refreezes in the matrix, coating rocks below the surface with layers of ice, a
situation we have observed in the field to persist even after surface snowpack has melted.
Although inactive features do not appear to contain persistent ice, they remain reliable sources of
groundwater and support unique vegetation communities and important wildlife habitat even
during droughts. Active versus inactive landforms are not readily distinguished by systematic
differences in environmental context (e.g. aspect), elevation (although active features tend to be
higher), form and appearance (active and inactive features can both have oversteepened fronts),
or capacity to support soil and vegetation. Intensive study of groundwater and/or permafrost
37
processes of these landforms will be important for understanding their hydrologic contributions
as temperatures increase in the future and other water sources disappear.
A NEW LOOK AT THE CHRONOLOGY FOR A CLASSIC PLEISTOCENE LAKE:
LAKE BONNEVILLE’S PROVO SHORELINE
DAVID M. MILLER (1), CHARLES G. OVIATT (2), AND JOHN P. MCGEEHIN (3)
(1) U.S. Geological Survey, 345 Middlefield Road, MS 973, Menlo Park, CA 94025
(2) Department of Geology, 108 Thompson Hall, Kansas State University, Manhattan, KS 66506
(3) U.S. Geological Survey, 12201 Sunrise Valley Drive, MS 926A, Reston, VA 20192
Lake Bonneville is one of the most studied and best dated Pleistocene lakes in the world and its
radiocarbon chronology serves as a benchmark for new chronometric methods. However, many
uncertainties remain, including issues with the dated materials, their relation to lacustrine
deposits, and interpreting stratigraphy and geomorphology of the deposits. The Provo shoreline,
generally considered to have been occupied during a period of overflow following the 17,500 cal
yr B.P. Bonneville flood until ~15,000 cal yr B.P., is the biggest geomorphic feature of Lake
Bonneville; its size has been attributed by many workers to stability of the overflow threshold.
During the course of studying the Provo shoreline to better determine the hydrologic maximum
for Lake Bonneville, we discovered that the relative ages of widely preserved beaches separated
vertically by ~3 m are the opposite of what has been widely assumed. The highest beach is the
youngest based on stratigraphy and geomorphology, and the Provo beach gravels thus represent
beach sedimentation during several lake-level rises. These relations could be explained by rises
in the overflow threshold by alluvial fan or landslide deposition. New radiocarbon dates from
gastropods collected within the beach gravels young upward and are among the oldest obtained
for the Provo deposits. The ages suggest that all or most of the beach deposits we studied (three
locations, three sets of deposits) formed early in the Provo time period, ~18,000 to 17,000 cal yr
B.P. In contrast, most previous ages were obtained from shells in offshore sand deposits, and are
17 to 15,000 cal yr B.P. The new data raise questions about the timing of the Bonneville flood,
the duration of Provo overflow, whether beach deposition shifted to offshore sand deposition
after 17,000 cal yr B.P., and whether Lake Bonneville radiocarbon ages on gastropods are
reliable. We conclude that significant uncertainties exist in the gastropod-dated chronology for
Lake Bonneville, and urge caution in interpreting radiocarbon ages at their reported
uncertainties, as well as in interpreting origins of landforms.
38
HOLOCENE VEGETATION AND DISTURBANCE RECONSTRUCTIONS
FROM THE TRANSITION REGION OF THE GREAT BASIN
AND COLORADO PLATEAU IN UTAH, USA
JESSE L. MORRIS (1), ANDREA R. BRUNELLE (1)
AND MITCHELL J. POWER (1,2)
(1) Department of Geography, University of Utah, Salt Lake City, UT 84112
[email protected], [email protected]
(2) Utah Museum of Natural History, University of Utah, Salt Lake City, UT 84112
Wildfire and bark beetles are important disturbance agents in western North America. This
research provides new insights into the ecology of these disturbances in the subalpine spruce/fir
forests of central and southern Utah. Two lacustrine records retrieved from the Wasatch and
Aquarius Plateaus suggest that epidemic spruce beetle (Dendroctonus rufipennis) disturbances
have pronounced impacts on vegetation composition and thusly pollen accumulation, and recur
at least at multicentennial intervals. The mean return interval (MRI) for stand-replacing fire
events is similarly long, ranging between 300-500 years. We report that wildfire does not follow
spruce beetle outbreaks, which supports dendroecological data conducted elsewhere in the
western U.S. Our records also demonstrate that forest composition is important in disturbance
ecology, particularly when considered over longer timescales. As the subalpine landscape
transitioned from the relatively cool late Pleistocene to the relatively warm middle Holocene,
these ecosystems shifted from spruce parkland to closed-canopy spruce/fir forests. Coincident
with greater stand density and fuel/host continuity, wildfire and spruce beetle disturbance events
became more frequent. The 20th century portion of these records reflect a general absence of fire
and the most significant spruce beetle outbreaks observed over the Holocene. The intensity of
these recent outbreaks are likely associated with anthropogenic modifications to the landscape
during the historic period, including logging, grazing, and fire suppression.
NORTHEAST PACIFIC AND WESTERN NORTH AMERICAN
CLIMATE VARIATIONS DURING 2009-2011
TOM MURPHREE
Department of Meteorology, Naval Postgraduate School, Monterey, CA 93943
The northeast Pacific Ocean and western North America region experienced several major
intraseasonal to interannual climate variations during 2009-2011, including El Niño, La Niña,
Madden-Julian Oscillation, and Arctic Oscillation events and/or their associated impacts. These
variations had significant impacts on atmospheric and oceanic temperatures and circulations, and
precipitation in the region. These impacts appear to have been, in part, a result of constructive
interference between the different variations. There is also some preliminary evidence that
39
global warming may have affected the magnitude of these impacts. The basic patterns and
processes associated with these variations and their impacts on the northeast Pacific Ocean and
western North American region will be reviewed, with a focus on extreme temperature and
precipitation events in western North America during 2009-2011.
VERTICAL MOVEMENT OF LOW-OXYGEN WATERS IN SANTA BARBARA BASIN
FOR THE PAST 15,000 YEARS
SARAH MYHRE (1), TESSA M. HILL (1), JAMES P. KENNETT (2),
KENICHI OHKUSHI (3), AND RICHARD BEHL (4)
(1) Bodega Marine Laboratory, P.O. Box 247, Bodega Bay, CA 94923
(2) Department of Earth Science, 1006 Webb Hall – MC 9630, University of California, Santa
Barbara, CA 93106-9630
(3) Ibaraki University 2-1-1, Bunkyo, Mito, 310-8512, Japan
(4) Department of Geological Sciences, California State University Long Beach,
1250 Bellflower Boulevard, 1250 Long Beach, CA 90840-3902
Here we constrain the upper vertical boundary of the California Margin Oxygen Minimum Zone
(OMZ) through the past 15,000 years. The depth and intensity of the California Margin OMZ is
responsive to events of rapid warming, however the spatial extent and underlying mechanism for
the synchrony is not clear. We construct a depth transect within Santa Barbara Basin (34 15‘N,
119 45‘W) using a core from 418 m water depth (MV0811-15JC), and previously investigated
cores from 481 m (MD02-2503) and 570 m (MD02-2504a) water depths. The transect spans 152
vertical meters and ends 32 m above basin‘s western sill depth. Isotope stratigraphy and
radiocarbon dating (planktonic foraminiferal calcite) were used to generate an age model.
Foraminiferal and invertebrate assemblages and sediment laminations reconstruct bottom water
oxygenation. Oxygen isotopic values at all three sites record similar surface water 18
O shifts
over the deglaciation (1.5‰ magnitude; based upon planktonic foraminifera Globigerina
bulloides) and a smaller but analogous 18
O shift is seen in benthic records (0.5‰ magnitude;
based on benthic foraminifera Uvigernia peregrina). The Bølling-Allerød lamination record
indicates strong hypoxia below 480 m; however laminations are not preserved at 418 m. In
contrast, benthic foraminiferal assemblages show similar responses (albeit more muted in the
shallowest site) to low-oxygen concentrations during the Bølling-Allerød, with species
Nonionella stella, Bolivina tumida, and Bulimina tenuata dominating at all three sites.
Invertebrate fauna diversity and abundance exhibit taxa-specific synchronicity with respect to
climate transition intervals, indicating cross-community responses to fluctuating oxygen
concentrations. At core MV0811-15JC, 32 m above the western basin sill, the proxies in the
Bølling-Allerød indicate marginally low oxygen conditions; strong enough to affect
foraminiferal and invertebrate assemblages, yet not strong enough to preserve annual laminations
40
like those seen in the deeper sites. These results indicate that OMZ waters ephemerally and
intermittently shoaled above 418 m during the Bølling-Allerød.
URANIUM ISOTOPIC VARIATIONS IN MODERN SOILS AND DATED SOIL
MINERALS: CALIBRATING A POTENTIAL PALEO-RAINFALL PROXY
JESSICA OSTER, KATHARINE MAHER, AND DANIEL IBARRA
Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305
[email protected], [email protected], [email protected]
Dated secondary minerals, such as pedogenic carbonate and opal and speleothem, display
substantial secular variations in initial (234
U/238
U) that may be related to environmental
variability. (234
U/238
U) of secondary minerals should record the U isotopic value of the soil
water or drip water from which they precipitate. Variation in soil water (234
U/238
U) may reflect
changes in eolian inputs, infiltration rates, or weathering rates. Given this wide array of potential
influences, distinguishing which processes led to initial (234
U/238
U) variability in the past can be
challenging. Here we present preliminary results from a combined study of modern soil water
chemistry from three soil sequences in Nevada and pedogenic mineral uranium isotopic
variability from Fish Lake Valley, Nevada. Modern soil waters from Diamond Valley, Newark
Valley, and Fish Lake Valley show significant initial (234
U/238
U) variability between sites, but
are consistent along soil profiles. Soil water initial (234
U/238
U) values appear to be set in the Av
layer and reflect soil parent material and grain size, and the degree of silicate versus carbonate
weathering in the soil profile. Initial (234
U/238
U) values vary significantly along an elevation
transect in Fish Lake Valley, with lower elevation soil waters displaying higher (234
U/238
U)
values, possibly reflecting slower water infiltration rates due to less precipitation at lower
elevations. The results of this modern soil water chemistry study were used to parameterize two
-recoil loss factor, and
infiltration rate on soil water initial (234
U/238
U) values. Fish Lake Valley pedogenic opal displays
substantial initial (234
U/238
U) variability (1.0-1.8) over the past 140,000 years, with generally
lower values during past glacial periods, and higher values during interglacials. This variability
could reflect generally wetter conditions during glacial periods, and drier conditions during
interglacials.
41
PLEISTOCENE PRECIPITATION VARIABILITY IN THE CENTRAL SIERRA
NEVADA: STALAGMITE RESULTS AND FUTURE DIRECTIONS
JESSICA OSTER (1), ISABEL MONTAÑEZ (2), AND JERRY POTTER (2)
(1) Department of Geological and Environmental Sciences, Stanford University,
Stanford, CA 94305
(2) Department of Geology, University of California, Davis, CA 95616
[email protected], [email protected]
U-series-calibrated paleoclimate records for stalagmites from two central Sierra Nevada foothills
caves document precipitation changes that are approximately coeval with Greenland temperature
changes during the last glacial period and deglaciation. The Moaning Cave isotopic and trace
element stalagmite proxies record variations in precipitation between 16,500 and 8,700 years ago
that suggest drier and possibly warmer conditions during Northern Hemisphere warm periods
and wetter and possibly colder conditions during high-latitude cool periods during the last
deglaciation (Oster et al., 2009). New paleoclimate proxy records for a stalagmite from
McLean‘s Cave, document changes in precipitation that are approximately coeval with
interstadials and stadials associated with Dansgaard-Oeschger cycles between 68,000 and 56,000
years ago, during Marine Isotope Stages 4 and 3. The McLean‘s Cave stalagmite documents
drier conditions in central California during Greenland interstadial events, signified by elevated 18
O, 13
C, grayscale, [Sr], and [Ba], and less radiogenic 87
Sr/86
Sr. Conversely, wetter
conditions in California during Greenland stadials are signified by more negative 18
O, 13
C,
lower grayscale, [Sr], and [Ba], and more radiogenic 87
Sr/86
Sr.
The precipitation changes indicated by the Moaning and McLean‘s Cave records for the
western Sierra Nevada are consistent with a broad picture of precipitation variability throughout
the Northern Hemisphere in response to climate changes in the high northern latitudes, with the
polar jet stream and Intertropical Convergence Zone shifting southward during Northern
Hemisphere cold periods and northward during warm periods. Our new observations further
support other paleoclimate records and models that link reduced precipitation in central
California with changes in Arctic sea-ice extent and thermohaline circulation in the North
Atlantic coincident with Arctic warming. We are further investigating these relationships by
expanding our cave monitoring research and speleothem paleoclimate reconstructions to include
other central and northern Sierra Nevada caves. We are also in the process of testing the linkage
between high latitude climate conditions and California precipitation using the NCAR
Community Climate System Model 3.
Oster, J.L., Montañez, I.P., Sharp, W.D., and Cooper, K.M., 2009, Late Pleistocene California droughts during
deglaciation and Arctic warming: Earth and Planetary Science Letters, DOI: 10.1016/j.epsl.2009.10.003
42
FORAMINIFERAL SHELL THINNING OVER THE LAST 100 YEARS IN VARVED
SEDIMENT FROM THE SANTA BARBARA BASIN, CALIFORNIA
DOROTHY PAK (1), LILY CLAYMAN (1), JAMES WEAVER (2), ARNDT
SCHIMMELMANN (3), AND INGRID HENDY (4)
(1) Marine Science Institute, University of California, Santa Barbara, CA 93106
(2) Wyss Institute, Harvard University, Cambridge, MA 02138
(3) Department of Geological Sciences, Indiana University, Bloomington, IN 47405
(4) Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109
Foraminiferal shell weights have been used as a proxy for calcite dissolution in marine sediments
and to infer periods of past ocean acidification, assuming that lower shell weights are due to shell
thinning in response to lower ocean water pH. Previous laboratory studies have shown that
calcification rates of some species of planktonic foraminifera decrease in response to lower
seawater carbonate ion concentrations, however, it is difficult to distinguish between post-
depositional dissolution and reduced biogenic calcification. A 2009 box core collected from the
center of Santa Barbara Basin (586 m water depth, 34° 16.847‘ N, 120° 02.268‘ W) has provided
a high-resolution record of varved sediment since A.D. 1780. We present a record of size-
normalized shell weights of the near-surface dwelling planktonic foraminifera Globigerina
bulloides spanning the last 250 years. Results indicate that foraminiferal shell weights in Santa
Barbara Basin were highest between 1900 and 1920 and decreased significantly in the mid-1970s
coincident with northeast Pacific Ocean warming as the Pacific Decadal Oscillation shifted from
cool to warm phase. Scanning electron microscopy of the foraminiferal shells indicates that the
decrease in shell weight was accompanied by a distinctive change in morphology. High shell
weight G. bulloides have numerous, closely spaced spine bases and large pores while low shell
weight G. bulloides have a smooth shell texture and small pores. The smooth-shell surface
morphology is replicated in laboratory dissolution experiments, consistent with removal of an
outer layer of calcite during shell thinning and partial dissolution of G. bulloides. Downcore thin-
shelled G. bulloides may be the result of either reduced calcification or subsequent partial
dissolution as the northeast Pacific Ocean warmed in the 1970s.
43
LONG-TERM SNOWPACK VARIABILITY AND CHANGE
IN THE NORTH AMERICAN CORDILLERA
GREGORY T. PEDERSON (1), STEPHEN T. GRAY (2), CONNIE A. WOODHOUSE (3),
JULIO L. BETANCOURT (4), DANIEL B. FAGRE (1), JEREMY S. LITTELL (5),
EMMA WATSON (6), BRIAN H. LUCKMAN (7), AND LISA J. GRAUMLICH (8)
(1) U.S. Geological Survey, Northern Rocky Mountain Science Center, Bozeman, MT 59715
[email protected], [email protected]
(2) Civil and Architectural Engineering, University of Wyoming, Laramie, WY 82071
(3) Geography and Development, University of Arizona, Tucson, Arizona 85721
(4) U.S. Geological Survey, National Research Program, Tucson, AZ 85719
(5) Climate Impacts Group, University of Washington, Seattle, WA 98195
(6) Environment Canada, Ontario, Canada
(7) Department of Geography, University of Western Ontario, London
Ontario N6A 5C2, Canada
(8) College of the Environment, University of Washington, Seattle, WA 98195
In the mountains of western North America, snowpack controls the amount and timing of runoff,
while also influencing myriad ecosystem processes. Within the Columbia, Missouri, and
Colorado River drainages, 60-80% of streamflow originates as snowpack, and snow serves as the
primary water source for >70 million people. In much of this region, observational records show
diminished snowpack since the 1950s, with further declines projected for the 21st century.
However, questions remain as to whether observed declines might result from natural variability,
as well as to how the magnitude and spatial extent of recent events fits into the context of the
Medieval Climate Anomaly, Little Ice Age, and other key climatic periods of the past 1,000+
years. In the first study of its kind, we use tree rings to produce millennial-length reconstructions
of snowpack at multiple spatial scales for key runoff generating areas in the North American
Cordillera. Results confirm that snowpack has declined significantly across the Northern Rocky
Mountains during the 20th
century, and over the entire cordillera since the 1980s. Such coherent
and persistent snowpack declines are rare in the reconstructions; before the 1950s the region
exhibits substantial inter-basin variability with northern areas tending toward wetness when the
south was dry, and vice-versa (i.e. the north-south moisture dipole). Cordillera-wide periods of
low snowpack shown for the 1350s, 1400s, and post-1980s era correspond with times of
anomalous warmth at regional and hemispheric scales. This implies Pacific Basin forcing of
winter precipitation, and the resulting north-south dipole, have been defining features of
snowpack variability for at least the last millennium, but temperature also has the potential to
synchronize snowpack anomalies across the entire cordillera. When combined with the high
44
likelihood of future warming, these results may herald a fundamental shift in regional snowpack
and water supplies.
FOSSIL WETLANDS IN THE DESERTS OF THE AMERICAN SOUTHWEST
JEFFREY S. PIGATI
U.S. Geological Survey, Denver Federal Center, Box 25046, MS-980, Denver, CO 80225
Today, wetlands constitute ~0.3% of the total land cover in the deserts of the American
Southwest, and encompass a variety of hydrologic settings, including seeps, springs, marshes,
and wet meadows. These systems form in areas where water tables approach or breach the
ground surface, most often near the distal toes of alluvial fans or where shallow faults or bedrock
force groundwater to the surface. When active, desert wetlands serve as important watering
holes for local fauna, support vegetation that depends on access to ground water for survival, and
act as catchments for eolian and alluvial sediments. The interaction between hydrologic systems
(emergent ground water and surface water), biologic systems (plants and animals), and geologic
systems (eolian and alluvial sediments) in wetlands creates unique and complex depositional
environments that are preserved in the geologic record as ground-water discharge (or GWD)
deposits. Here I present the results of ongoing investigations of GWD deposits along an east-
west transect across the Mojave Desert and southern Great Basin, and compare the results to
GWD deposits elsewhere in the American Southwest in an attempt to better understand what
drove changes in hydrologic conditions in this region during the Pleistocene. I will also discuss
innovative methods of dating GWD deposits that we have developed, which have implications
for dating other types of Quaternary deposits in arid environments.
CHIRONOMID PALEOCLIMATOLOGY:
THE VIEW FROM THE GREAT BASIN
DAVID F. PORINCHU
Department of Geography, The Ohio State University, Columbus, OH 43201
Much progress has been made in using sub-fossil midges to reconstruct Holocene climate change
in the Great Basin of the United States and address outstanding questions relating to recent and
long-term climate change in this region. High-resolution (sub-decadal) chironomid stratigraphies
spanning the 20th
century, developed for a number of lakes in the Great Basin, reveal dramatic
shifts in midge community composition have occurred in recent decades and that variations in
midge community composition are tracking observed changes in July temperature. These studies
demonstrate that sub-fossil chironomid analysis can provide detailed records of local and
regional climatechanges at sub-decadal timescales. Application of a midge-based inference
45
model to late Holocene sediment has also provided insight into regional climate and
environmental conditions by providing a quantitative reconstruction of the thermal conditions
that existed during the last 2,000 years. A sediment core representing the past 2,000 years was
recovered from Stella Lake in the Snake Range of the central Great Basin in Nevada. The core
was analyzed for sub-fossil chironomids and sediment organic content. The midge-based
temperature reconstruction suggests that the interval between A.D. 600 and 1300 was
characterized by fluctuating temperature: a depression of approximately 1.2oC temperature
occurred between ~ A.D. 700 and 850 corresponding to the Carolingian cold phase and was
followed by an increase in MJAT of approximately 1.8 C between A.D. 900 and 1300
corresponding to the classical Medieval Climate Anomaly (MCA). Comparison of the Stella
Lake temperature reconstruction to previously published paleoclimatic records from this region
indicates that the Carolingian period was characterized by both decreased temperature and
increased effective moisture. The prolonged interval of elevated temperatures that characterized
the central Great Basin between A.D. 900 and 1300 correspond to regional records of widespread
aridity and are concurrent with hemispheric temperature trends associated with the MCA. This
record increases our understanding of temperature variability and temperature-drought relations
in the arid Southwest.
BIOMASS BURNING IN THE AMERICAS AFTER A.D. 1500:
EUROPEAN CONTACT OR CLIMATE?
MITCHELL JAMES POWER (1), FRANCIS MAYLE (2), PATRICK J BARTLEIN (3)
(1) Utah Museum of Natural History and Department of Geography,
University of Utah, Salt Lake City, UT 84112
(2) School of Geosciences, University of Edinburgh, Edinburgh, EH8 9AD United Kingdom
(3) Department of Geography, University of Oregon, Eugene, OR 97403
The degree to which indigenous population collapse, caused by European contact, led to a
decline in biomass burning across the Americas, is a topic of considerable debate. Here, we
investigate this issue by synthesizing charcoal records from the Americas, as a proxy for biomass
burning over the past 2,000 years. We find a clear, widespread signal that the Americas
experienced a post-1492 decrease in biomass burning, with a nadir centered ca. A.D. 1600-1800,
although inter-regional comparisons show that the amplitude of this downturn varied
considerably. However, charcoal records from outside of the Americas show a similar decrease.
This observation, with regional paleoclimate records and pre-Columbian population estimates
suggests that Little Ice Age cooling played a greater role than indigenous population collapse in
driving the decline in biomass burning.
46
THE PACLIM YEAR: WESTERN CLIMATE 2010-2011 IN PERSPECTIVE
KELLY T. REDMOND
Western Regional Climate Center, Desert Research Institute,
2215 Raggio Parkway, Reno NV, 89512
For the third year in a row the western states remained in a relatively cool pattern compared with
the last one to two decades, though parts of the region have remained somewhat warm. Spring
2011 and especially May showed very cool temperatures. The monsoon season was generally
wetter and warmer than average. Markedly cool temperatures were noted all summer along the
immediate California coastline, close to the coolest on record. The 2010 fire season was much
less active than during the previous decade. La Niña developed during the summer, and became
one of the strongest in the last six decades, persisting into spring. The spatial pattern of
precipitation anomalies differed in important respects from the expected canonical pattern. Of
special note was the extremely wet start to Water Year 2010-2011, well south along the
California coast, and in a swath extending northeastward from there into Colorado. Despite the
lengthy presence of La Niña, calendar year 2010 ended as globally the warmest year on record
(within uncertainty), from both surface and satellite observations. A six-week lull in snow
accumulation commenced at the start of 2011 along the West Coast, followed by a period that
more closely resembled the typical La Niña climate pattern in western North America. The
winter so far has shown a significant number of vigorous storms and noteworthy temperature and
hydrologic extremes in the western states, nationwide, and over North America. Both La Niña
and the negative phase of the Arctic Oscillation have appeared to be significant factors in the
winter so far. The Arctic and Greenland, by contrast, have experienced yet another very mild
winter, and Arctic ice thus far this winter is the lowest extent on record. Long-term drought has
diminished this winter over much of the West, but has expanded in eastern parts of the
Southwest. The Colorado River may experience near to above average snowmelt stream flow.
Globally, 2011 has started out cool to near average in temperature.
47
EVIDENCE FOR LATE HOLOCENE HYDROLOGIC CHANGE AT
BIG SODA LAKE, A MAAR LAKE IN NORTHWEST NEVADA
LIAM REIDY (1), ROGER BYRNE (1), LYNN INGRAM (2),
MICHAEL ROSEN (3), AND MARITH REHEIS (4)
(1) Department of Geography, University of California, Berkeley, CA 94720
[email protected], [email protected]
(2) Department of Earth and Planetary Sciences, University of California,
Berkeley, CA 94720
(3) U.S. Geological Survey, 2730 North Deer Run Road, Carson City, NV 89701
(4) U.S. Geological Survey, P.O. Box 25046, Lakewood, CO 80225
During the past 130 years paleolimnological research in the Great Basin has produced a rich
record of late Quaternary environmental change. Most of this research has focused on the
evidence of lake level changes and their implications for our understanding of climate change in
the region. However, despite the progress that has been made relatively few of these studies have
focused on high resolution i.e. sub-decadal scale records.
Here we present the preliminary results of δ18
O and x-ray fluorescence (XRF) analyses
on the upper 2-meters of a laminated sediment core recovered from Big Soda Lake, a maar lake
near Fallon, Nevada. Core chronology is provided by 210
Pb, the first appearance of non-native
pollen types, radiocarbon, and two dated tephra. The data provide a 1,500 year record of regional
climate change in the Carson Sink area.
High resolution δ18
O and XRF data indicate sub-decadal changes in lake levels during
the late Holocene and more recent changes associated with disturbance alongside the lake during
the late 19th
and early 20th
centuries. Oscillations in the oxygen isotope record during the pre-
historic period indicate significant changes in lake water levels. As the lake is only fed by
precipitation and groundwater inflow these changes in lake level must be related to regional
climate shifts. The abrupt change to lower oxygen isotope values near the top of the record
marks the introduction of fresh groundwater to the lake. Construction of an irrigation project in
the early 1900s caused increases in nearby groundwater levels which, in turn, caused lake levels
to rise by 18 m between 1907 and 1930.
Longer cores (8.80 m and 9.30 m) recovered in November 2010 are presently being
analyzed to extend the record to the middle Holocene.
48
WATER YEAR 2011: THE RAINS HAVE COME BACK
MAURICE ROOS
California Department of Water Resources, Sacramento, CA 95821
This will be a report on how the current water year is shaping up with a hydrologic review and
some perspective on the past several years including the 2007-2009 California drought.
This water year started off well in October with an abundance of rain eventually
producing about 250% of average by the end of the month. Nearly ¾ the monthly total was
produced by an atmospheric river from the semitropical western Pacific Ocean during the fourth
week of the month. The wet streak continued in November with northern Sierra Nevada eight
station average precipitation 127% of average followed by a very wet December nearly twice
normal. The three month total for the northern Sierra on January 1 was 1.8 times average.
Statewide precipitation was even better at almost twice average for the three month period. The
Sierra snowpack was a robust 210 percent of average and 75% of an average April 1 pack in
terms of water content. In contrast to patterns expected in a La Niña year, the southern Sierra
was 270% compared to 180% in the north. Southern California suffered from floods during
Christmas week.
In January, the tide shifted with the buildup of a high pressure system just offshore. As
of this writing in late January we have had three weeks of mostly dry weather. The snowpack
has remained at about ¾ of the April 1 average, hopefully to be available later in the season as
enough usable snowmelt to produce at least a near normal water supply.
Now to review the recent past, including the 2007-2009 three year drought and how it
compares with past droughts. After a very wet water year in 2006, which had statewide runoff
slightly over 170% of average, we had three consecutive years of much below average runoff.
This drought was not quite as severe as the six year 1987-1992 drought. For the Sacramento four
river runoff, the average annual amount in 2007-2009 was 11.1 million acre-feet (maf),
compared to 10.1 maf during 1987-1992 and a two year average of only 6.7 maf in 1976-1977.
The 50 year average is 18.6 maf for the Sacramento four rivers. When one looks at the runoff
deficits, the recent three year drought seemed to have greater consequences than previous. One
factor is continuing urban growth and therefore higher water demand with basically the same
supply infrastructure. Another is higher environmental demands. Since previous droughts
environmental factors have now reduced available water supplies for agricultural and urban
users. What has happened is a substantial increase in environmental water demands with no
significant change in supply facilities. It would be nice to distinguish between drought and water
shortage. The former is a hydrologic deficiency; the later would be due to demands exceeding
the assured supply or lack of facilities to meet water requirements even in normal years.
49
EVIDENCE OF HYDROLOGICAL CHANGES CAUSED BY HUMAN DISTURBANCE
RECORDED IN NITROGEN AND CARBON ISOTOPES FROM BIG SODA
AND PYRAMID LAKES, NEVADA
MICHAEL R. ROSEN (1), LIAM REIDY (2), SIMON POULSON (3), CAROL KENDALL (4),
ROGER BYRNE (2), AND MARITH REHEIS (5)
(1) U.S. Geological Survey, 2730 North Deer Run Road Carson City, NV 89701
(2) Department of Geography, University of California, Berkeley, CA 94720
(3) Department Geological Sciences and Engineering, University Nevada, Reno, NV 89557
(4) U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025
(5) U.S. Geological Survey, P.O. Box 25046, Lakewood, CO 80225
Nitrogen isotopes of lake sediment organic matter have been used to determine changes in lake
productivity, eutrophication, and hydrology. However, isotopic shifts caused by human-induced
changes to the hydrology of lakes have rarely been documented in lake sediments. Nitrogen
isotope data collected from Big Soda Lake, a volcanic maar lake near Fallon, Nevada, and
Pyramid Lake, a large terminal lake located about 40 km northeast of Reno, Nevada, show
distinct opposite shifts in the early 1900‘s to the present that are likely caused by the construction
of the Newlands Irrigation Project, which diverted water away from the Truckee River and
Pyramid Lake down the Truckee Canal to Lahontan Reservoir. This water was used to irrigate
farmland near Big Soda Lake, which caused its lake level to rise 18 m by 1930. At the same
time Big Soda Lake was rising, Pyramid Lake level was falling and stopped overflowing to
nearby Lake Winnemucca in the early 1930‘s. This caused Lake Winnemucca to become a dry
lake in the late 1930‘s. The differing hydrologic history of the two lakes is evident in the
approximately 10‰ negative isotopic shift in δ
15N at Big Soda Lake in the upper 15 cm of
sediment. This change occurred around A.D. 1900 based on 210
Pb sedimentation rates. The
negative shift is likely caused by build-up of high ammonium concentrations (NH3 is
approximately 45 mg/L in the monimolimnion) due to meromixis, which began after the lake
level rose. This build-up led to a large isotopic fractionation that is associated with ammonium
assimilation. This in turn caused a decrease in the δ15
N values of the deposited organic matter. In
Pyramid Lake, a 2‰ increase in δ15
N occurred over approximately the same time period as the
decrease in Big Soda Lake. As 14
N is preferentially incorporated into phytoplankton,
phytoplankton N can have δ15
N values several ‰ lower than that of the dissolved inorganic
nitrogen (DIN), so the δ15
N value of the remaining DIN will increase in the deposited sediment.
These data possibly indicate an increase in primary productivity of Pyramid Lake during this
time. Stable δ13
C isotope data from both lakes show similar opposite trends over the same time
periods. Pyramid Lake δ13
C values became more negative after 1930 and Big Soda Lake became
more positive. Even though climate during this time was the same for both lakes, the hydrologic
50
changes to both basins have caused opposite trends in δ15
N values of deposited organic matter in
these lakes. Determining the changes in nitrogen isotope composition during these known
changes in recent hydrologic conditions can allow a better understanding of possible changes
observed in these lakes during the Holocene.
EROSION OF TOPMOST VARVES BY TURBIDITE DEPOSITION LIMITS
VARVE COUNT ACCURACY IN SANTA BARBARA BASIN, CALIFORNIA
ARNDT SCHIMMELMANN (1), INGRID HENDY (2), DOROTHY PAK (3),
AND AARON ZAYIN (1)
(1) Department of Geological Sciences, Indiana University, Bloomington, IN 47405
(2) Department of Geological Sciences, University of Michigan, MI 48109
(3) Marine Science Institute, University of California, Santa Barbara, CA 93106
The annually laminated (i.e. varved) sediment in the central Santa Barbara Basin (SBB) off
California has been dated independently by consecutive varve-counting of the last 2,000 varves
and by radiometric methods (e.g., radiocarbon ages of foraminifera). Age differences among
dating methods are in part caused by errors in varve counting that cumulatively reduce dating
accuracy down core. For example, some varves can be missing in the sedimentary record if the
topmost, youngest, and least consolidated sediment is eroded by occasional strong bottom
currents. The silled nature of the SBB usually precludes strong bottom currents, but the shear of
fast-flowing and dense turbidite currents from up-slope may erode and suspend topmost bacterial
mat and underlying soft sediment. A 2009 SBB box core from 585.8 m water depth (34° 16.847‘
N, 120° 02.268‘ W) featured continuously varved sediment from A.D. 1931 to 2009. However,
below the 1931 varve, a 6 cm thick turbidite was found resting on the 1923 varve, as
determined by cross-correlation of the pre-1924 varve pattern with records from other box cores
featuring continuous varves across the 20th
century. The turbidite was likely triggered seismically
on 5 August 1930 when a strong earthquake shook Santa Barbara. The local 1930 turbidite
eroded annual varves from 1924 to 1930. Sectioning of a cylindrical sub-core from the same box
core showed 1-cm large rip-up clasts of varved sediment with various angles of lamination
embedded in the lower portion of the 1930 turbidite. The presence of occasional thick turbidites
in SBB sediments, especially prior to A.D. 1850, likely causes undercounting of varves.
51
RAINFALL, RUNOFF, AND POST-WILDFIRE GEOMORPHIC
TRANSPORT PROCESSES
KEVIN M. SCHMIDT (1), MAIANA N. HANSHAW (1), JAMES F. HOWLE (2),
AND JONATHAN D. STOCK (1)
(1) U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025
[email protected], [email protected], [email protected] (2) U.S. Geological Survey, 5229 North Lake Boulevard, Carnelian Bay, CA 96140
Moderate rainfall rates that are insufficient to erode unburned landscapes can trigger accelerated
sediment transport rates in landscapes denuded of vegetation by wildfire. To quantify how
rapidly burned steeplands in southern California erode during rainfall, we monitored
rainfall/runoff relationships and generated time-series of high-resolution topography by
surveying steep, low-order drainage basins using repeat terrestrial laser scanning (TLS), lidar.
Our goals were to map geomorphic process signatures with respect to rainfall rates and
understand the mechanisms of sediment transport processes characteristic of post-wildfire
erosion including debris-flows. Through repeat TLS, generation of bare-earth model DEMs, and
field mapping, we documented how patterns of exhumed bedrock, sediment
redistribution/volume changes on hillslopes, and sediment infilling of low-order valleys rapidly
altered both the variable source area for overland runoff and the sediment available for transport
by post-fire debris flows. We derived ten distinct map units representing geomorphic processes
through field observations of topographic character, sedimentary structures, and depositional or
erosional relationships. Map unit boundaries varied over time in response to changing
rainfall/runoff relationships, storm magnitudes, and local conversion to sediment supply limited
conditions where the underlying bedrock or competent soil horizons were exhumed. In response
to precipitation intensities exceeding 20 mm/hr in four separate events, steep hillslopes underlain
by cohesive sediments in the western Transverse Range, California, experienced overland-flow
erosion over 70% of the area, but triggered no debris flows. In contrast, steep hillslopes
underlain by non-cohesive plutonic rocks in the San Gabriel Mountains, California experienced
widespread erosion along the valley axis exceeding 1.5 m depth, in addition to numerous debris
flows in response to four storms with rainfall rates ranging from 7 to 28 mm/hr; with the highest
averaged hourly rainfall intensities occurring during a localized convective storm. If climatic
forecasts of more frequent wildfire and greater precipitation variability are realized, accelerated
sediment transport rates may enhance conversion from soil-mantled, shrub-dominated chaparral
hillslopes to bedrock-dominated, grassland ecosystems.
52
MODELED PLEISTOCENE DISTRIBUTIONS OF THREE CLIMATICALLY
SENSITIVE TREE TAXA IN CENTRAL AND NORTHWESTERN MEXICO
DYUTI SENGUPTA AND ROGER BYRNE
Department of Geography, University of California, Berkeley, CA 94720
[email protected], [email protected]
Paleoecological reconstructions that include the Last Glacial Maximum (LGM; 21,000 cal yr
B.P.) from central and northwestern and Mexico are scarce. Only a handful of pollen records and
glacial evidence are commonly cited to describe conditions in central Mexico during the LGM.
For northwestern Mexico the story is similar, although the combination of high resolution
packrat middens, oceanic cores and terrestrial sediment cores lend more support to
reconstruction scenarios. In addition to traditional methods of proxy data analysis and
interpretation, phylogenetic analysis and paleoecological modeling serve as another means of
visualizing past environments. Recent improvements in climate modeling techniques and species
distribution (SDM) modeling software, coupled with increased data availability has greatly
benefited the process of visualizing past environments. However, the results are not always in
agreement with well-accepted paleoproxy interpretations. Here we consider three important cool
climate taxa that appear in both central and northwestern Mexico (Abies, Picea, Artemisia), to
test the usefulness of two models in a paleoclimatic context. On comparing the model results to
proxy data and phylogenetic interpretations, we find agreement in some regions of Mexico for all
three taxa. These results make clear that careful selection of relevant taxa and ecological
variables and an understanding of both the modeling technique and the climate data is crucial to
generating plausible results. We also suggest the possibility that the LGM climate projection may
be inaccurate in certain regions of Mexico, thereby affecting the model results.
CMIP3 PROJECTIONS FOR THE PACIFIC DECADAL OSCILLATION FOR 2000-
2050 UNDER THE B1, A1B, AND A2 SRES EMISSION SCENARIOS
JEANNINE-MARIE ST. JACQUES, SUZAN LAPP, ELAINE BARROW,
AND DAVID SAUCHYN
Prairie Adaptation Research Collaborative (P.A.R.C.), Room 120, 2 Research Drive,
University of Regina, Regina, SA, S4S 7H9, Canada
The climatology and hydrology of western North America display strong periodic cycles which
are correlated with the low-frequency Pacific Decadal Oscillation (PDO). The PDO‘s signature
is seen throughout the entire North Pacific Ocean, with related significant associations to
hydrology and ecology in western North America and northeastern Asia. Therefore, the status of
the PDO in a warmer world caused by anthropogenic climate change is of great interest. We
developed early 21st century projections of the PDO, using data from archived runs of the most
recent high-resolution global climate models from the IPCC Fourth Assessment Report (AR4)
53
(Phase 3 of the Coupled Model Intercomparison Project - CMIP3). These PDO projections for
2000-2050 showed a weak multi-model mean shift towards more occurrences of the negative
phase PDO for the B1, A1B and A2 emissions scenarios. If present-day teleconnection
correlation patterns hold, this suggests future declines in American Southwest and northern
Mexican surface water availability, and thereby negative impacts on agriculture and
hydroelectric power generation. It also suggests an increase in future winter precipitation for the
Pacific Northwest of North America. However, not all the models showed a consistent shift to
negative PDO conditions.
PROJECTED NORTHERN ROCKY MOUNTAIN ANNUAL STREAMFLOW FOR
2000-2099 UNDER THE B1, A1B AND A2 SRES EMISSIONS SCENARIOS
JEANNINE-MARIE ST. JACQUES (1), SUZAN LAPP (1), YANG ZHAO (2), ELAINE
BARROW (1) AND DAVID SAUCHYN (1)
(1) Prairie Adaptation Research Collaborative (P.A.R.C.), Room 120, 2 Research Drive,
University of Regina, Regina, SA, S4S 7H9, Canada
(2) Department of Mathematics and Statistics, University of Regina,
Regina, SA, S4S 0A2, Canada
The 20th
century hydroclimatology of the northern Rocky Mountains is heavily influenced by
recurring large-scale climate patterns: the Pacific Decadal Oscillation (PDO), the El Niño-
Southern Oscillation (ENSO), and the Arctic Oscillation/North Atlantic Oscillation (AO/NAO).
Hence, northern Rocky Mountain river discharge variability can be successfully modeled by
regression techniques using these climate indices as predictors. Generalized least squares (GLS)
regression addresses residual autocorrelation and allows reliable significance testing of any
predictor coefficients, and hence, is highly suitable for hydrological modeling. We developed
GLS regression equations which captured a major portion of streamflow variability for ten
centennial-length northern Rocky Mountain annual discharge records. Both unregulated and
paired regulated and naturalized flows were examined. Using archived global climate model runs
from the Coupled Model Intercomparison Project Phase 3 (CMIP3), we projected the PDO,
ENSO and NAO for the 21st century for the B1, A1B and A2 SRES emission scenarios. These
projected climate indices were used as inputs into the GLS equations, giving projected northern
Rocky Mountain river discharges for the 21st century. These projections showed generally
declining trends in surface water availability for 2001-2100. Researchers have projected
increases in summer warmth and typically decreasing summer precipitation, and increases in
winter precipitation and temperature for this region under greenhouse forcing. Our results
suggest that in the competition between these two opposing effects on surface water availability,
the former will dominate.
54
AN EMPIRICAL METHOD TO FORECAST THE EFFECT OF STORM INTENSITY
ON SHALLOW LANDSLIDE ABUNDANCE
JONATHAN D. STOCK (1) AND DINO BELLUGI (2),
(1) U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025
(2) Department of Earth and Planetary Sciences, University of California, Berkeley, CA 94720
Intense rainfalls from historic storms have triggered widespread shallow landslides in the coastal
mountains of California. Varved sediments in the Santa Barbara Basin may contain the geologic
record of such storms over the past millennium. These deposits are substantially thicker than
those associated with storms of January 1969, the most recent historic events to generate
widespread landslides in southern California. If layer thickness scales with storm intensity, these
layers imply that southern California has experienced storms that are massive compared to our
recent historical experience. Unlike seismic hazard maps, we cannot begin to quantify the
magnitude of landslide hazards that will accompany such a storm. Put simply, we cannot answer
the question of how many shallow landslides California's largest storms would trigger.
We hypothesize that shallow landslide abundance in a landscape increases with rainfall
intensity, duration and the number of unstable model cells for a given shallow landslide
susceptibility model. We use digital maps of historic shallow landslides in northern and southern
California, and nearby rainfall records to construct a relation between rainfall intensity and the
fraction of unstable model cells that actually fail in historic storms. We find that this fraction
increases as a power law with the 6-hour rainfall intensity for sites in southern California. We
use this relation to forecast shallow landslide abundance for a dynamic numerical simulation
storm for California (Arkstorm), representing the most extreme historic storms known to have
impacted the state.
55
PROJECTED SEA-LEVEL RISE IMPACTS ON THE SALT MARSH LANDSCAPES
OF SAN FRANCISCO BAY, CALIFORNIA AND ITS
RESIDENT SALT MARSH WILDLIFE SPECIES
JOHN TAKEKAWA (1), KAREN THORNE (1), KYLE SPRAGENS (1), MICHAEL
CASAZZA (2), CORY OVERTON (2), JUDITH DREXLER (3),
DAVE SCHOELLHAMMER (3), AND KATHLEEN SWANSON (3)
(1) Western Ecological Research Center, San Francisco Bay Estuary Field Station,
U.S. Geological Survey, 505 Azuar Drive, Vallejo, CA 94592
(2) Western Ecological Research Center, Dixon Field Station, U.S. Geological Survey,
6924 Tremont Road, Dixon, CA 95620
(3) California Water Science Center, U.S. Geological Survey, Placer Hall,
6000 J Street, Sacramento, CA 95819
Coastal salt marshes and estuaries are projected to be disproportionately impacted by climate
change and sea-level rise, according to the Intergovernmental Panel on Climate Change. Over
80% of wetlands in San Francisco Bay estuary have been lost to urban development and
landscape modification. The San Francisco Bay estuary, though severely fragmented and
modified, represents one of the largest tidal salt marsh complexes in the western United States
and contains important remaining habitat for federal- and state-listed species. Maintenance and
expansion of habitat is crucial to the successful recovery of endangered species, but it remains
unknown how much of a detrimental effect sea-level rise may impact the amount and quality of
habitat for these species. The focus of this interdisciplinary study is to evaluate sea-level rise
impacts to salt marsh habitats and wildlife by synthesizing field data, modeling, and using
ArcGIS tools to develop impact models. Work was done at 13 salt marsh sites around the San
Francisco Bay area. Our work illustrates the risk to wildlife species and identifies critical sea-
level rise thresholds for species. In addition sediment modeling and downscaling of tidal cycles
are being used to better understand impacts. Habitat impact models and ongoing research
objectives will be presented.
56
DIAGNOSING AND PROJECTING CLIMATE CHANGE IN THE HAWAIIAN
ISLANDS
OLIVER ELISON TIMM (1), THOMAS W. GIAMBELLUCA (1),
AND HENRY F. DIAZ (2)
(1) University of Hawaii at Manoa, Honolulu, HI 96822
(2) NOAA-CIRES Climate Diagnostics Center, Boulder, CO 80305
Hawai‗i has experienced a gradual warming in the last 100 years and especially since the mid-
1970s. Likewise, the statewide rainfall experienced decadal changes and an overall drying trend,
particularly during the wetter winter months. The warming trend is largest in higher elevated
regions on the islands, and this is consistent with other studies that support a general
amplification of anthropogenic warming with elevation. In Hawai‗i, the upper mountain slopes
harbor most of the remaining intact native ecosystems and a continuous warming is likely to
have severe impacts. For example, endangered Hawaiian honeycreepers currently find refuge in
high-elevation forests, where low temperatures limit the activity of disease-carrying mosquitoes.
Changes in temperatures and precipitation can force endemic species to abandon their old natural
habitat zones, migrate to more agreeable areas, or in worst case the habitat zones could vanish
entirely. Another unique feature of the climate of the Hawaiian Islands is that in most areas, the
highest intensity rainfalls contribute disproportionately to the annual means. We have been
focusing on diagnosing changes in the upper rainfall quantiles in the context of natural and
anthropogenic forcing.
PALEOFIRE REGIMES IN MEDITERRANEAN CLIMATE REGIONS
SHIRA TRACY (1), MITCHELL POWER (1), R. SCOTT ANDERSON (2), AND THE GPWG
COMMUNITY
(1) Utah Museum of Natural History, Department of Geography, University of Utah, Salt Lake
City, UT 84112
(2) School of Earth Sciences & Environmental Sustainability, Northern Arizona University,
Flagstaff, AZ 86011
Biological hotspots support high concentrations of endemic species and serve as an effective
conservation tool by delineating geographic boundaries. Here we explore the role of fire as a
potential mechanism of diversity across similar Mediterranean type climates. Fire and climate
linkages during the last 15,000 years were examined from five Mediterranean ecosystems,
including; coastal California, Mediterranean basin, central Chile, southwestern Australia, and
Southern Africa. These regions support Mediterranean climates with winter wet and summer dry
precipitation, associated ocean upwelling, and the absence of glaciated terrains. Sites from the
Global Charcoal Database were compared to pollen studies from localities in Mediterranean
57
hotspots. We hypothesize fire maintains mosaic landscapes by short fire return intervals,
contributing to the high levels of endemicity. Global analysis of Mediterranean fire activity
suggests a rapid rise in fires between14,000 and 13,000 cal yr B.P., followed by a decline from
13,000 to 12,000 cal yr B.P. After 9,000 cal yr B.P., fire activity increased in all Mediterranean
regions until the middle Holocene. Analysis of five isolated Mediterranean regions reveals a
coherent pattern in fire activity across all locations beginning by 9,500 cal yr B.P. As
Mediterranean-type vegetation developed between 5,000 and 2,000 cal B.P., increased climate
variability associated with ocean upwelling, produced increased variability in fire regimes and a
potential mechanism for the development of Mediterranean diversity. Identifying the long-term
interrelationship between fire and the presence and abundance of endemic species will provide a
better understanding of the role fire plays in the development and long-term stability in
Mediterranean hotspots. With increasing anthropogenic pressure, and high levels of fire
suppression in Mediterranean hotspots, more research is necessary to aid future conservation and
fire management strategies in these unique regions.
GUIDING CLIMATE CHANGE PLANNING FOR SAN FRANCISCO BAY
TIDAL MARSHES
SAM VELOZ (1), NADAV NUR(1), LEO SALAS(1), JULIAN WOOD(1), DIANA
STRALBERG (1,2), GRANT BALLARD (1), AND DENNIS JONGSOMJIT (1)
(1) PRBO Conservation Science, Petaluma, CA 94954
(2) Department of Biological Sciences, University of Alberta, Edmonton,
AB, T6G 2R3, Canada
Climate change will affect wetlands in San Francisco Bay through sea-level rise changes in
seasonal salinity and changes in tidal-inundation regimes. These changes are likely to convert
tidal freshwater and brackish wetlands into more saline systems and result in greater inundation
of tidal marshes, thereby changing plant species composition and structure for birds and other
wildlife and threatening the long-term sustainability of vegetated marsh habitats and the
ecosystem services they provide. Using several different scenarios of suspended sediment supply
and rates of sea-level rise we projected potential changes in tidal marsh habitats at twenty year
intervals from 2010-2100. In areas with low sediment availability (25-50 mg/L) such as southern
Marin, sedimentation models predict marsh drowning within 20-100 years, depending on the rate
of sea level rise. In areas with very high sediment availability (300 mg/L) such as the Petaluma
River and south San Francisco Bay, models predict marsh resilience even under high rates of sea
level rise (up to 165 cm over the next century). In areas with intermediate sediment availability,
however, marsh sustainability will depend on the rate of sea-level rise. Under high rates of sea
level rise, only low marsh can be maintained. We present results of future tidal marsh
simulations that project future distributions and abundance patterns of principal plant species and
key tidal-marsh dependent birds in relation to physical variables (elevation, salinity, channel
58
density, etc.). Summer salinity and tidal marsh elevation were consistently important variables
for predicting the distribution of tidal marsh vegetation. The distribution and abundance models
are being used to assess the vulnerability of tidal marsh bird species of conservation concern,
including the Federally-endangered Clapper Rail and the State-threatened Black Rail to climate
change. Our findings and recommendations can inform decisions that will shape efforts to
conserve and restore San Francisco Bay wetlands and vertebrate populations that depend on tidal
wetlands, as well as guide decision making by government agencies at the local, regional, and
state levels.
LATE HOLOCENE ENSO VARIABILITY IN THE CENTRAL PACIFIC:
PRELIMINARY DATA FROM PALMYRA ATOLL
DAVID WAHL (1), ALEXIS VISCAINO (2), ROB DUNBAR (2), AND LYSANNA
ANDERSON (1)
U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025
[email protected]; [email protected]
Environmental Earth System Science, Stanford University, CA 94305
[email protected]; [email protected]
Variations in present day tropical Pacific precipitation are tied to patterns of SST anomalies
primarily driven by shifting modes of ENSO. Instrumental records from the low latitude central
Pacific region exhibit a strong response to ENSO dynamics, suggesting paleoclimate
reconstructions from this region would hold great potential for more fully understanding the
relationship between ENSO variability and synoptic climate patterns. However, due to its
remoteness and lack of viable research sites, a paucity of high-resolution late Holocene climate
reconstructions from the central Pacific currently exists.
Palmyra Atoll, a remote uninhabited series of islets in the central Pacific, represents one
of these rare viable sites. Using multiple proxies to reconstruct past sea surface conditions, we
seek to understand the relationship between ENSO variability and known late Holocene climate
events (ie. the Medieval Climate Anomaly and Little Ice Age).
We report preliminary data from a 3.2 m sediment core retrieved from the west lagoon on
Palmyra Atoll (5º 53' 05.25" N; 162º 05' 21.63" W; water depth 51 m). Radiocarbon
determinations on pteropods from the basal sediment of the core indicate the record extends to ~
640 cal yr B.P. (A.D. 1310). Evidence for construction on the atoll during WWII includes a
discreet horizon of coarse-grained carbonate, providing a chronologic marker at 8 cal yr B.P.
(A.D. 1942). Oxygen isotopic composition of authigenic carbonates, high-resolution scanning
XRF, 14
C, and 210
Pb data are currently being collected, and together will be used to construct a
model of changing sea surface conditions for the region.
59
ELKHORN SLOUGH TIDAL WETLANDS: PAST, PRESENT AND FUTURE
ELIZABETH BURKE WATSON (1,2), ERIC VAN DYKE (2),
AND KERSTIN WASSON (2,3)
(1) Department of Land, Air and Water Resources, University of California, Davis, CA 95616
(2) Elkhorn Slough National Estuarine Research Reserve, Watsonville, CA 95076
(3) Ecology and Evolutionary Biology, University of California, Santa Cruz, CA 95064
Tectonic uplift, a narrow continental shelf, and heavy surf place strong natural limits on the areal
extent of tidal wetland habitat along the California coast. Concurrently, human activities and
associated landscape changes have led to the large-scale destruction of much of the region‘s tidal
wetlands. Tidal wetlands at Elkhorn Slough, central Monterey Bay, are thus a regionally
important resource: this area supports among the largest remaining extents of tidal wetlands in
California. Unfortunately, these wetlands are in deteriorated condition: a large portion were
diked off from tidal exchange (these areas exist today as shallow eutrophic ponds), and in fully
tidal locations, hydrologic modifications to the estuary have resulted in plant mortality and marsh
loss. At Elkhorn Slough National Estuarine Research Reserve, we are conducting a study
utilizing stratigraphic assessments and habitat modeling in order to address key questions about
the historical extent, current trajectory, and future distribution of estuarine wetlands at Elkhorn
Slough, with an emphasis on understanding the impacts of climate variability and climate change
on this coastal resource. For the purposes of habitat reconstruction, sediment stratigraphies with
chronologic control established using radiocarbon dating, have revealed dramatic variability in
marsh extent at Elkhorn Slough, revealing clear episodes of past marsh deterioration. Studies of
contemporary sediment accumulation undertaken using sediment-erosion tables, sediment tiles,
marker beds, and recent radiometric dating (e.g. 137
Cs/210
Pb) reflect a submerging marsh plain
and escalating accumulation rates in both vegetated and deteriorated tidal marsh.
Implementation of a habitat model (Sea level affecting marshes – SLAMM) has identified low
suspended sediment concentrations as an obstacle to marsh sustainability under even the most
moderate sea level rise/climate scenarios, but has identified potential future marsh migration
pathways. These data will be used to help set well-informed targets for marsh acreage in the
estuary and to understand what geographical areas are likely sites for marsh migration.
60
A LATE-HOLOCENE RECORD OF DISTURBANCE FROM THE
NORTHERN ROCKY MOUNTAINS, USA
JENNIFER H. WATT (1), ANDREA BRUNELLE (1), AND KURT KIPFMUELLER
Department of Geography, RED Lab, University of Utah, Salt Lake City, UT 84112
Department of Geography, Center for Dendrochronology, University of Minnesota, Minneapolis,
MN 55455
Mountain pine beetle (MPB) outbreaks have impacted or are currently affecting many pine
communities in the western U.S. It is not clear if these large-scale outbreaks are unprecedented
or if they have previously occurred at this magnitude. Reconstructing high-resolution
disturbance regimes (fire and MPB) from sedimentary records for the Holocene (the last 10,000
years) will provide insight on disturbance ecology in subalpine forests. The records presented
here use charcoal to identify past fire disturbance and a new pollen method to identify past MPB
outbreaks. The new pollen method was developed from recent studies in spruce-fir forests where
changes in pollen composition were used to identify past spruce beetle outbreaks. Initially, it
was unclear if this would work in pine-dominated systems where there is not the same trade-off
between dominant tree taxa. Two late Holocene records from Fishstick Lake, Idaho and Lake of
the Woods, Montana demonstrate that pollen ratios can be used to identify past bark beetle
outbreaks in pine-dominated forests.
FROM ATMOSPHERIC CIRCULATION TO GRAPE TEMPERATURES: MACRO-,
MESO-, TOPO-, AND MICROCLIMATE IN VINEYARDS (AND YOUR GLASS)
STUART B. WEISS
Viticision/Creekside Center for Earth Observation
27 Bishop Lane,Menlo Park, CA 94025
Few agricultural crops are as sensitive to weather and climate as wine grapes. Small fluctuations
in temperature and phenology can make the difference between high quality and poor quality
crops. Climate change will challenge continued production of quality wine grapes in the Pacific
States. In order to effectively consider climate change in vineyard design and management, a
multi-scale approach to climate is required, descending scales from macroclimate through
mesoclimate, topoclimate, and microclimate.
In this presentation, I describe applications of this hierarchy to vineyards. Station data,
and interpolated surfaces such as PRISM account for macroclimatic and mesoclimatic gradients
down to a scale of 800 m. Ripening dates, both past and projected, of grape varieties can be
estimated from monthly data at these scales. Topoclimatic gradients are derived from digital
elevation models (DEMs) using solar radiation models, topographic position, and slope, and
have profound effects on minimum and maximum temperatures. At the finest scale, microclimate
61
encompasses the effects of vegetation canopies on solar radiation, humidity, and temperature,
such as the effects of trellis design on berry temperature on either side of the trellis.
Hemispherical photography quantifies trellises from a ―grapes‘ eye view,‖ allowing estimation of
solar radiation on grape clusters at half hourly intervals for each month. By combining all of
these methods with inexpensive temperature sensors, the temperatures of grape clusters can be
tracked through growing seasons using local weather station data, with numerous key insights
into vineyard design and management in a variable and changing climate.
MILLENNIAL-SCALE CLIMATE OSCILLATIONS OVER THE PAST 735,000 YEARS
AS RECORDED IN HIGH-RESOLUTION MARINE SEDIMENT RECORDS
FROM SANTA BARBARA BASIN, CALIFORNIA
SARAH M. WHITE (1), TESSA M. HILL (1), JAMES P. KENNETT (2),
AND RICHARD BEHL (3)
(1) Department of Geology, University of California, Davis, CA 95616
[email protected], [email protected]
(2) Department of Earth Science, University of California, Santa Barbara, CA 93106
(3) Department of Geological Sciences, California State University, Long Beach, CA 90840
A lack of high-resolution climate records beyond the last glacial period has limited
understanding of causes, effects, and temporal development of Quaternary abrupt climate shifts.
Santa Barbara Basin (SBB), with a sedimentation rate of 100 cm/1,000 yr, provides uniquely
well-preserved sediments spanning the past ~700,000. Five piston cores from SBB, each
spanning ~5,000, were dated to ~735,000, 460,000, and 290,000 years ago. These cores allow us
to see whether millennial-scale climate shifts have changed in amplitude, shape, and/or timing
since the Mid-Pleistocene Transition, and how they are expressed in the Pacific in terms of ocean
circulation, productivity, and oxygenation. We use stable isotopes of planktonic (Globigerina
bulloides, Neogloboquadrina pachyderma), and benthic foraminifera (Uvigerina peregrina) and
planktonic foraminiferal assemblage analyses including % N. pachyderma (d), and sediment
lamination data. δ18
O data of G. bulloides and N. pachyderma show shifts of up to 1.4‰ in as
briefly as ~80 years and 2.5‰ over ~1,000 years during warming. Water column stratification
(shown by the difference between G. bulloides and N. pachyderma δ18
O) increases during
interstadials. The % N. pachyderma (d) often varies in tandem with planktonic δ18
O, but exhibits
threshold behavior instead of smooth change, and is generally higher during interstadials and/or
moderate water column stratification. δ13
C values broadly correlate with shifts in δ18
O, and
reflect changing ocean circulation, carbon cycling, and/or methane release. Preserved sediment
laminations coincide with intervals of warm, stratified upper waters. A comparison of our data to
SBB records from the past 60,000 years (Behl and Kennett, 1996; Hendy and Kennett, 1999,
2000; Hill et al., 2006) shows that typical stadial-interstadial shifts in planktonic δ18
O (~1.5‰)
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are similar to those recorded during the past 60,000 years, although changes in % N. pachyderma
(d) are smaller, and planktonic assemblages are slightly different, with fewer G. bulloides,
Globigerina quinqueloba, and Globorotalia scitula, and more N. pachyderma (s).
Behl, R.J., and Kennett, J.P., 1996, Brief interstadial events in the Santa Barbara Basin, NE Pacific, during the last
60 kyr: Nature, v. 376, p. 243-246.
Hendy, I.L. and Kennett, J.P., 1999, Latest Quaternary North Pacific surface water responses imply atmospherically-
driven climate instability: Geology, v. 27, n. 4, p. 291-294.
Hendy, I.L. and Kennett, J.P., 2000, Stable isotope stratigraphy and paleoceanography of the last 170 ka: ODP Site
1014, Tanner Basin, California: Ocean Drilling Program Scientific Reports, v. 167, p. 129-140.
Hill, T.M., Kennett, J.P., Pak, D.K., Behl, R.J., Robert, C., and Beaufort, L., 2006, Pre-Bølling warming in Santa
Barbara Basin, California: Surface and intermediate water records of early deglacial warmth: Quaternary
Science Reviews, v. 25, n. 21-22, p. 2835-2845.
CLIMATE DRIVERS OF STREAMFLOW SYNCHRONICITY IN
WESTERN U.S. RIVERS OVER MULTIPLE CENTURIES
ERIKA K. WISE
Department of Geography, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
Twentieth century high- and low-streamflow events in the western U.S. have been linked to
Pacific and Atlantic Ocean influences, including those described by the El Niño–Southern
Oscillation (ENSO), the Pacific Decadal Oscillation, and the Atlantic Multidecadal Oscillation.
Extended streamflow records, reconstructed using tree rings, have identified drought and pluvial
periods in the past that were more extreme than those recorded during in the instrumental record.
This study compares a new tree-ring based reconstruction of Snake River streamflow with
streamflow reconstructions of the Colorado, Sacramento, and Verde rivers. Results suggest that
changes in the predominance of zonal versus meridional atmospheric flow may have influenced
patterns of synchronous and asynchronous streamflow in the four rivers. Spatial drought patterns
indicate a zonal flow pattern during two of the most severe droughts in the Snake River record
(the 1630s and the 1930s), which were much less severe in the Verde River record. The Snake
River‘s low-flow period in the early 1700s, which was less severe in magnitude, is replicated in
the flow of all four rivers and may be indicative of persistent meridional flow. These drought
patterns appear to correspond to shifts in Pacific Ocean conditions; however, direct comparisons
between these periods and reconstructed indices such as ENSO are hindered by inconsistencies
between existing reconstructions of paleo-teleconnections.
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VARIATION IN FORAMINIFERAL DISTRIBUTIONS ACROSS THE PLEISTOCENE-
HOLOCENE TRANSITION OFF THE KAYAK SLOPE, NORTHERN GULF OF
ALASKA
SARAH D. ZELLERS, KATHRYN MUELLER, AND DIANA D. HILL
Department of Biology and Earth Science, University of Central Missouri,
Warrensburg, MO 64093
The Integrated Ocean Drilling Program is considering drilling in the Gulf of Alaska (GOA),
where the interplay among climate, tectonics, and deposition can be examined. A slope site off
Kayak Island, sampled by jumbo piston core (EW040885JC), is providing insight into
paleoceanographic, depositional, geochemical, and climatic changes across the Pleistocene-
Holocene transition, including the Bølling–Alleröd (Bø–Al) warm interval and the Younger
Dryas (YD) cold interval. These intervals were determined by geochemical analyses, siliceous
microfossil distributions, and isotopic analyses by various researchers. Foraminiferal biofacies
also track the Bø–Al and YD intervals. Core EW040885JC contains four intervals with distinct
faunal assemblages. From 1124 to 680cm core depth, samples consist of a sandy diamicton with
a mixture of outer shelf taxa (Epistominella pacifica , Uvigerina, Cassidulina, Islandiella, and
Cibicides), and common Elphidium clavatum, indicating transport into deep water by ice rafting
and/or turbidity currents. Planktonic foraminifera are abundant and consist mainly of
Neogloboquadrina pachyderma (sinistral and some dextral) and Globigerina bulloides. Two
samples from a short interval (680 to 640 cm), corresponding to the Bø–Al, consist of brown,
laminated calcareous ooze dominated by benthic taxa (Bolivina and Bulimina) indicative of low
oxygen and a few planktonic foraminifera. Above this zone (640 to 410 cm) are bioturbated,
silty muds with low abundances of Gyroidina, Bolivina, and the shelf taxa listed above, along
with abundant planktic foraminifera (N. pachyderma and G. bulloides), corresponding, in part,
to the YD. From 410 to the top of the core (0 cm), foraminifera are not common, with muds
dominated by abundant radiolarians, diatoms, and sponge spicules. Assemblages show a change
from glacially-influenced deposition, to low oxygen bottom waters, to climatic conditions
favoring silica production at the top.
DEVELOPING ROBUST AGE MODELS FOR LAKE RECORDS:
CASE STUDIES FROM CALIFORNIA
SUSAN R.H. ZIMMERMAN, TOM GUILDERSON, AND TOM BROWN
Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory,
Livermore, CA 94550
In recent years, it has become apparent that Earth‘s climate system is variable on many scales of
time and space, and includes abrupt changes that have global effects. When attempting to
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understand the relationships of decadal- to centennial-scale variability between sites and
depositional environments, a ―coarse‖ age model with a handful of ages does not suffice. To
better describe patterns of past drought in California, we are establishing robust, high-resolution 14
C chronologies for regional lakes ranging from 34º to 42º latitude, 540 to 2,100 m elevation,
and in a variety of vegetational, hydrological, geochemical, and biological settings. Almost 300
radiocarbon dates have been measured on terrestrial and aquatic macrofossils, as well as bulk
sediment – macrofossil pairs. The latter have yielded no single answer to the meaning of bulk-
sediment dates; in a few instances, a constant off-set is implied, but in most cases there is no
pattern, reinforcing the unreliability of bulk sediment dates. As a complement to the radiocarbon
measurements, some sediment sequences have also had 210
Pb, 137
Cs, and paleomagnetic secular
variation (PSV) measurements, providing independent information to refine the age model.
Construction of a robust age model from any set of measured ages requires honest
recognition of uncertainties due to the reliability of individual ages and methods, differences in
calendar-year calibration datasets, interpolation between discretely-dated horizons, and sources
of geological variability. Calibration of radiocarbon dates to calendar years requires an
internationally-accepted calibration data-set (e.g, INTCAL-09), and is relatively simple to do
with programs like Calib and OxCal, but requires a rigorous propagation of errors which in
reality should yield an age envelope and probability distribution. Several calibration programs
contain the ability to include Bayesian statistics (priors) of the calibration curve and construct an
age-model with simulated calendar uncertainties. We present examples of various methods for
construction of robust, high-precision age models, and a picture of past droughts in California
emerging from our lacustrine records.