adélie penguins confront climate change in the ross sea grant ballard, viola toniolo, david ainley,...

Adélie Penguins Confront Climate Change in the Ross SeaGrant Ballard, Viola Toniolo, David Ainley, Claire Parkinson (Code 614.1, NASA GSFC), Kevin Arrigo,

and Phil Trathan

Figure 2: April 2004 (left) and July 2004 (right) sea ice distributions (fuzzy gray) and locations of the tracked Ross Island Adélie penguins from Cape Royds (blue) and Cape Crozier (orange) (from Ballard et al. 2009).

Figure 1: Sea ice distributions in the Ross Sea and vicinity in February 2004, 2005, and 2006, and positions of Adélie penguins tracked with satellite transmitters (from Ballard et al. 2009; ACC = Antarctic Circumpolar Current).

Hydrospheric and Biospheric Sciences Laboratory

Sea ice changes in recent decades in the Antarctic include ice decreases near the Antarctic Peninsula and ice increases in the Ross Sea. The changes have been challenging for Antarctic seabirds, including Adélie penguins, whose numbers have declined markedly in regions of decreasing sea ice. Until recently, no wintertime data were available for the southernmost of the Adélies. This study has changed that through the use of Geolocation Sensors to track penguins from two Ross Island colonies (at Cape Royds and Cape Crozier). Key results include:

(1) The distance traveled by the tracked penguins in their annual migrations averaged 12,760 km

(2) The penguins favored areas with sea ice concentrations between 75% and 85%, utilized sea ice movements to assist in a clockwise migration pattern, and rarely ventured north of the outer ice edge.

(3) Although the penguins require light for navigating and for foraging, twilight is sufficient. (4) In contrast to the Adélies of the Weddell Sea, the Ross Island Adélies winter within the consolidated pack ice, well back from the outer ice edge. This could be either because of the greater competition the Ross Island penguins have from other Ross Sea penguins or because of their wanting to remain as close to Ross Island as possible.

Name: Claire L. Parkinson, NASA GSFC, Code 614.1Email: [email protected]: 301-614-5715

Affiliations: G. Ballard/PRBO Conservation Science and University of Auckland, V. Toniolo/Stanford University, D. Ainley/HT Harvey & Associates, C. Parkinson/NASA Goddard Space Flight Center, K. Arrigo/Stanford University, P. Trathan/British Antarctic Survey

Reference: Ballard, G., V. Toniolo, D. G. Ainley, C. L. Parkinson, K. R. Arrigo, and P. N. Trathan, 2009: Responding to climate change: Adélie penguins confront astronomical and ocean boundaries, Ecology, submitted.

Data Sources: Penguin data were obtained through platform transmitting terminals (PTTs) and Geolocation Sensors affixed to the penguins. Sea ice data were derived from data from the Defense Meteorological Satellite Program (DMSP) F13 Special Sensor Microwave Imager (SSMI).

Technical Description of the Images: Figure 1. The mapped sea ice distribution shows the areas with ice concentrations of at least 15%, as derived from DMSP SSMI data using the NASA Team Algorithm. Penguin locations were tracked by satellite through PTTs placed on the penguins. Figure 2. Sea ice coverage was derived from DMSP SSMI data using the NASA Team Algorithm. Penguin locations were determined from Geolocation Sensors attached to the penguin legs. The average southern boundary of the Antarctic Circumpolar Current (ACC) is shown near the top of each image; the Ross Sea shelf break is depicted with a solid white curve; the Ross Ice Shelf is in white at the center bottom; and the two latitude circles shown are for the Antarctic Circle (at 66.5°S) and for the latitude of 0 winter twilight (72.7°S).

Scientific Significance: The rapidity of recent climate changes has been challenging for many species, including Adélie penguins, who have been affected in particular by changes in Antarctic sea ice distributions. Adélie populations have declined markedly in regions of decreasing sea ice coverage, and their migration patterns have been affected in all regions of changing ice. This study has obtained information about the wintertime migration patterns of the Ross Island Adélies, determining, for instance, their preference for sea ice of concentrations of 75-85% and the fact that twilight suffices for their light requirements.

Relevance to Future Science and Relationship to Decadal Survey: As climate change continues, Adélie penguins are one of many wildlife species that is bound to be affected, as the Adélies rely on marine life for food, sea ice for a platform especially during their annual molt (when their growing feathers lack a protective waterproof layer), and sunlight for navigating and foraging. For species like the Adélies, the interconnections between the physical environment and local and regional ecosystems are still far from fully understood, with great need for intensive long-term studies.


Shifts in the warm surface water pathways in the North Atlantic OceanSirpa Hakkinen, NASA GSFC, Code 614.2

Analysis of surface drifter tracks in the North Atlantic Ocean from 1990 to 2008 provides evidence that warm subtropical waters have recently increased their penetration towards the Nordic Seas.

Prior to 2000, the warm water branches of the North Atlantic Current fed by the Gulf Stream turned southeastward in the eastern North Atlantic.

Since 2001, Fig. 1, these paths have shifted toward the Rockall Trough through which the most saline North Atlantic Waters pass to the Nordic Seas.

The near-surface changes between the latter half of the 1990s and the first half of the 2000s, have been also confirmed in the surface-current product (OSCAR) computed from altimeter, Fig. 2. These changes are also consistent with the observed increase in temperature and salinity of the waters flowing northward into the Nordic Seas.

Figure 2: Difference of OSCAR surface current fields [2001-2005] minus [1996-2000].

Figure 1: Subtropical drifter tracks when drifters are within the western box during 1991-1995, 1996-2000, 2001-2005 and 2003-2008. Drifter tracks entering (cyan) and leaving (magenta) the subtropical box (48W-78W, 35N-47N). The black squares are locations of the drifter launches. From Hakkinen and Rhines, J.Geophys.Res., 114, 2009.


Name: Sirpa Hakkinen, NASA/GSFC E-mail: [email protected]: 301-614-5712

References:

Hakkinen and Rhines, J.Geophys.Res., 114, doi:10.1029/2008JC004883, 2009.

Data Sources: We use surface currents from NOAA/AOML Global Lagrangian Drifting Buoy Data Base. The data are available since 1989, although somewhat sparse in the early years. The surface drifters are drogued to 15m depth below sea surface, and we will use only drogued drifter observations. The data base provides the drifter location and temperature every 6 hours. The surface drifters are imbedded in the surface Ekman layer, thus wind stress changes are anticipated to have an impact on the drifter tracks. To visualize the changes of the surface currents in the Eulerian frame we take advantage of OSCAR surface current analysis (http: //www.oscar.noaa.gov) which combines altimetric geostrophic velocities and Ekman drift computed from remotely sensed wind products (SSM/I, NSCAT, QuikSCAT).

Technical Description of Image:Figure 1:Subtropical drifter tracks when drifters are within the western box during 1991-1995, 1996-2000, 2001-2005 and 2003-2008. Drifter tracks entering (cyan) and leaving (magenta) the subtropical box (48W-78W, 35N-47N). The black squares are locations of the drifter launches. Figure 2:Difference of OSCAR surface current fields [2001-2005] minus [1996-2000].

Scientific significance: The observed large increase in salinity of the Nordic Seas inflow at the Faroe-Shetland Channel and Rockall Trough since 1996 and particularly after 2001, cannot be explained by local surface precipitation-evaporation flux, but requires changes in the source waters of the inflow, which can only be achieved by changes in the large scale circulation. The drifter data as well as the altimetry derived currents show that the large scale surface circulation is able to undergo large shifts in matter of few years.

Relevance for future science : The increased Nordic Seas inflow salinity will help to maintain Atlantic meridional overturning circulation by enhancing the water mass modification at higher latitudes.


http://db.aoml.noaa.gov/cgi-bin/db/Bin/init_applet.x?gld+GLDKRIGGUI.class

NASA provides key datasets for monitoring of global agricultural productionNASA provides key datasets for monitoring of global agricultural productionMolly Brown, NASA GSFC, Code 614.4Molly Brown, NASA GSFC, Code 614.4

In agricultural economies, the majority of residents get some or all of their income from agricultural activity. In these regions, food security is highly related to weather-related food production deficits.

NASA satellite data and models are key input variables for organizations such as the Famine Early Warning Systems Network (FEWS NET).

The images show key monitoring variables for FEWS NET.

Figure 3: NASA AVHRR NDVI Figure 4: TRMM Rainfall data

Figure 2: AIRS precipitable water


Figure 1: MODIS land surface temperature

Name: Molly E. Brown, NASA/GSFC E-mail: [email protected]: 301-614-6616

Satellite remote sensing data is a key input to agricultural monitoring programs, both here in the U.S. and in Africa. Remotely sensed images taken from satellites and aircraft provide a means to assess field conditions and pasture conditions at a scale that enables direct comparison of production on different continents and regions simultaneously.

References:Brown, M. E., C. Funk, G. Galu & R. Choularton (2007) Earlier Famine Warning Possible Using Remote Sensing and Models. EOS Transactions of the American Geophysical Union, 88, 381-382.

Brown, M.E. (2008) Famine Early Warning Systems and Remote Sensing Data, Springer-Verlag: Heidelberg and New York. pp 313 (May 2008).

Brown M.E. and C.C. Funk (2008) Food Security under Climate Change. Science 319 (5863): 580 - 581. DOI: 10.1126/science.1154102

Data Sources: Satellite remote sensing from NASA form the basis for agricultural observations for a variety of US government agencies as well as private sector and international organizations. The US Department of Agriculture (USDA) and the US Agency for International Development in particular have missions which require global monitoring of agricultural production. They are key users of NASA earth science data. This slide shows four key datasets that are used operationally by the Famine Early Warning Systems Network (FEWS NET), a key program at the US Agency for International Development.

Technical Description of Image:Figure 1: Land surface temperature product from the Terra MODIS sensor has recently been introduced to FEWS NET as a result of a NASA ROSES project in collaboration with the US Geological Survey. This image, as well as that from Figures 2 and 4, are part of the Early Warning Explorer (EWX) viewer, which will soon be operational at the USGS.

Figure 2: AIRS precipitable water data provides an additional source of information over regions that are persistently cloudy during the agricultural growing season, to assist in determining the progress of the season.

Figure 3. AVHRR normalized difference vegetation index (NDVI) data is available from the GSFC GIMMS group from 1981 to the present in real time every fifteen days. FEWS NET and the foreign agriculture service at the USDA use NDVI as a key parameter in estimating the intensity of flood and drought conditions on agricultural production through time.

Figure 4. NOAA’s rainfall estimate (RFE) is a gridded precipitation model that ingests TRMM data along with a wide variety of other NASA products to estimate rainfall over land in real time.

Scientific significance: These data products are key elements to monitoring agricultural production and pastoral health in developing countries that are extremely sensitive to fluctuations of weather. Understanding ongoing weather conditions and how they may impact agriculture is a key first step in being able to respond effectively and with the least cost to the US Government. Thus NASA’s role in these programs is central to their success.

Declining Per Capita Agricultural Production and Climate Change Threatens Declining Per Capita Agricultural Production and Climate Change Threatens Food Security in 2030Food Security in 2030

Molly Brown, NASA GSFC, Code 614.4Molly Brown, NASA GSFC, Code 614.4

Per capita agricultural production is likely to continue to decline due to population expansion, lack of investment and threats to rainfall due to climate change.

Figure 2: Numbers on the map show likely changes in per capita agricultural production in 2030 under a ‘business as usual’ scenario, based on historical 1961-2007 trends, including both precipitation changes (TRMM) and population expansion.

Funk and Brown (2009) Food Security J.

Disparity in yields is both a threat and an opportunity!

Figure 1: Projected change in TRMM rainfall in 2050 using a hybrid dynamic-statistical precipitation reformulations. We expect large declines in rainfall in east and southern Africa.


Name: Molly E. Brown, NASA/GSFC E-mail: [email protected]: 301-614-6616

Hybrid dynamic-statistical reformulations (Funk et al., 2008; Brown and Funk, 2008) provide one potential way to work around the limitations of global climate models for precipitation projections. Instead of using the climate model precipitation directly, we use regression (based on historical data) to relate changes at some location to large scale climate indicators.

References:C. Funk and M.E. Brown (2009) Declining Global per Capital Agricultural Capacity and Warming Oceans Threaten Food Security, Food Security Journal doi: 10.1007/s12571-009-0026-y

Brown M.E. and C.C. Funk (2008) Food Security under Climate Change. Science 319 (5863): 580 - 581. DOI: 10.1126/science.1154102

Brown, M. E., B. Hintermann & N. Higgins (2009) Markets, Climate Change and Food Security in West Africa. Environmental Science and Technology, 18. in press

Data Sources: The data used in this analysis are the UN’s Food and Agriculture Organization’s division of the world into 18 regions, and using 1961-2007 data on total cereal yields, harvested area, and total population. We also used a number of 20th century (1980-2000) & 21st century (2000-2100) simulations used in this study. These model simulations are produced by premier climate modeling groups in the United States, Europe and Asia, including the GFDL CM 2.1,GISS ER, IAP FGOALS, IPSL CM4, MIROC3.2 Hi Res, MIROC3.2 Med Res, MPI ECHAM5, MRI CGCM 2.3.2a, NCAR CCSM 3.0, and the UKMO HADGEM1.

Technical Description of Image:Figure 1: These panels describe our hybrid dynamic-statistical precipitation reformulations for eastern and southern Africa. These reformulations are based on 21st century projections of central Indian Ocean [0-15°S, 60-90°E] precipitation (from the blended satellite-gauge Global Precipitation Climatology Project (Adler et al. 2003)) and global precipitation 1st principal components. The left plot shows each location’s main growing season (M=MAM, J=JJA, S=SON, D=DJF). The right plot shows downscaled 2050 rainfall projections, expressed as a percent change in main season precipitation. IO and PC1 regression parameters are multiplied by the seasonally appropriate changes shown in Fig. 5. This produces the anticipated change in rainfall.

Figure 2: The colors on the map shows 2030 per capita production projections based on historical 1961-2007 trends. The projected yields are those based on 1961-2007 linear trend models. Annual yield trends vary significantly by region. North America, Western Europe, and Eastern Asia have seen increases of over 700 kg ha-1 annum-1. Western, Middle, and Eastern Africa, conversely, have exhibited very slow growth in yields (Table 5), with annual changes in yields of less than 110 kg ha-1 annum-1. Without accelerated agricultural development, many regions will still see very low yields in 2030. Values shown on map before and after arrows denote, respectively, the observed 2007 and projected 2030 per capita cereal production values in kg per person per year.

Scientific significance: This paper presented analyses that show that without concerted effort, today’s food security crisis will continue to accelerate, robbing millions of people of their potential livelihoods. Our results suggest that large-scale trends in yields and per capita harvested area (Fig. 2) are very predictable. We can be quite certain that the world will experience significant reductions in food availability as consumption demands increase due to biofuels and rising living standards.


Soil moisture is an important component of the Earth’s water and energy balance, but tree canopies present a challenge to measuring soil moisture from space due to their masking effect on the underlying soil moisture signal.

A field experiment has been conducted to see if effectivevegetation parameters for trees can be determined for use in thesimple zero-order tau-omega model for soil moisture retrieval.

Effective single scattering albedo (ω) values do not appear to be sensitive to seasonal changes in the canopy or to incidence angle, and are on the order of ω = 0.1; vegetation opacity (τ) is sensitive to incidence angle and season, and its accurate determination requires additional work.

Determination of Effective Tree Parameterization for Improved Microwave Soil Determination of Effective Tree Parameterization for Improved Microwave Soil Moisture Retrieval Moisture Retrieval

Peggy O’Neill, NASA GSFC, Code 614.3Peggy O’Neill, NASA GSFC, Code 614.3

Figure 1: Test site of deciduous Paulownia trees.

Hsim HeffVsim Veff

-- first-order scattering solution -- best-fit zero-order solution -- first-order scattering solution -- best-fit zero-order solution

Figure 2: Table of effective τ & ω values determined from Fig. 3 and from a best fit to measured data.


Figure 3: Effective τ & ω tree values found by fitting the zero-order tau-omega model to a first-order scattering solution.

Name: Peggy E. O’Neill, NASA/GSFC, Code 614.3E-mail: [email protected]: 301-614-5773

References:

Kurum, M., R. Lang, P. O’Neill, and C. Utku, “Modifying Tau-Omega Model to Account for Forest Canopy Scattering,” National Radio Science Meeting, Commission F, URSI, Boulder, CO, January 5-8, 2009.

O’Neill, P., R. Lang, M. Kurum, A. Joseph, M. Cosh, and T. Jackson, “Microwave Soil Moisture Retrieval under Trees using a Modified Tau-Omega Scattering Model,” Proc. of IGARSS’09, IEEE, Cape Town, South Africa, July 13-17, 2009.

Kurum, M., R. Lang, C. Utku, and P. O’Neill, “A Physical Model for Microwave Radiometry of Forest Canopies,” Proc. of IGARSS’09, IEEE, Cape Town, South Africa, July 13-17, 2009.

Kurum, M., R. Lang, P. O’Neill, A. Joseph, T. Jackson, and M. Cosh, “L-band Radar Estimation of Forest Attenuation for Active/Passive Soil Moisture Inversion,” IEEE Trans. on Geoscience and Remote Sensing, Sept., 2009, in press. Data Sources: NASA’s Terrestrial Hydrology Program has funded a three-year field experiment to measure the L band microwave response to soil moisture under different types of small to medium tree canopies (Fig. 1). The project is a collaboration between GSFC, George Washington University, and USDA. The truck-mounted ComRAD radar / radiometer instrument system is used to obtain microwave data over deciduous and coniferous trees coincident with measurements of soil and vegetation properties.

Technical Description of Image: Most microwave soil moisture retrieval algorithms developed for use at L band frequencies have been based on a simplified zero-order radiative transfer approach where scattering is ignored and vegetation canopies are generally treated as a bulk attenuating layer – this is usually referred to as the tau-omega model, where vegetation effects are parameterized by tau and omega, the vegetation opacity and single scattering albedo. The zero-order tau-omega model is attractive for routine microwave soil moisture retrieval due to its simplicity and ease of inversion and implementation, and is the baseline retrieval approach for the SMOS and SMAP missions. However, its applicability to large vegetation canopies like trees is questionable. Although physical theory indicates that more scattering terms should be included in the radiative transport solution for forest canopies due to the large size of the tree canopy components, it is possible that effective tau and omega values can be found that will enable the zero-order tau-omega model to work for trees (Fig. 2, 3). This project has investigated a number of different ways of estimating effective scattering and attenuation parameters, and compared them to values obtained by a best-fit to measured experimental data.

Scientific significance: While advances in L band microwave technology have led to the upcoming SMOS and SMAP missions, current baseline soil moisture retrieval algorithms for these missions have been developed and validated only over grasslands, agricultural crops, and light to moderate vegetation. Tree areas have generally been excluded from operational microwave soil moisture retrieval plans due to the large expected impact of trees on masking the microwave response to the underlying soil moisture. Once completed, this project should provide quantitative assessments of tree scattering and attenuation, leading to improved soil moisture retrievals for tree areas from microwave missions in space.

Relevance for future science and relationship to Decadal Survey: Soil moisture is a critical control on water and energy cycles, as well as weather,climate, hydrological and agricultural prediction. Eventually, the knowledge gained from this study will help to extend accurate soil moisture retrievals from global microwave space missions like SMOS and SMAP to more areas of the Earth’s surface than are currently feasible.


Satellite-Scale Modeling of Land-Atmosphere CouplingSatellite-Scale Modeling of Land-Atmosphere CouplingJoseph A. Santanello, Jr. and Christa D. Peters-Lidard, NASA-GSFC Code 614.3Joseph A. Santanello, Jr. and Christa D. Peters-Lidard, NASA-GSFC Code 614.3


Dry Soils

Atmospheric fluxes of heat and moisture

(entrainment)

7am

Land Surface fluxes of heat and moisture (evaporation)

‘Mixing Diagram’ approach depicts L-A fluxes and feedbacks through the evolution of 2-meter temperature and humidity.

7pm

7am

----- Observations

7pm

The degree of local coupling (‘LoCo’) between the land and atmosphere is a function of complex processes and feedbacks that require further understanding and quantification.

The daily variability of heat and moisture states and fluxes near the Earth’s surface is reflective of both land surface (soil moisture) and atmospheric (boundary-layer depth) conditions. As a result the modeled and observed evolution of temperature (T) and humidity (q) can be used as a diagnostic of LoCo.

A unique NASA modeling system (LIS-WRF) has been developed and successfully applied to a framework for diagnosing LoCo that combines physically-based process models with observations of land and atmospheric properties at satellite scales.

Results show that soil moisture anomalies lead to significantly different signatures of heat and moisture evolution and highlight the potential utility of routine observations of T and q from current and future NASA satellite platforms.

Figure 2: Daytime evolution of specific humidity vs. potential temperature for the dry and wet soil moisture locations in Fig. 1

Model Range

Wet Soils

Dry Soils

Wet

Dry

Soil Moisture (m3/m3)

Figure 1: Near-surface soil moisture map of the Southern Great Plains Region.

Name: Joseph A. Santanello, Jr., NASA-GSFC E-mail: [email protected]: 301-286-7450

References: Kumar, S. V., C. D. Peters-Lidard, J. L. Eastman, and W.-K. Tao, 2008: An integrated high resolution hydrometeorological modeling testbed using LIS and WRF. Environmental Modelling and Software, 23, 169-181.

Santanello, J. A., C. Peters-Lidard, S. Kumar, C. Alonge, and W.-K. Tao, 2009: A modeling and observational framework for diagnosing local land-atmosphere coupling on diurnal time scales. J. Hydrometeor., 10, 577-599.

Data Sources: The community-supported Weather Research and Forecasting (WRF) model has been coupled to NASA-GSFC’s Land Information System (LIS), which provides a flexible and high-resolution representation and initialization of land surface physics and states. Within the LIS-WRF framework, the land surface energy balance and mixed layer equilibrium established by difference land-atmosphere scheme couplings are evaluated in terms of the diurnal temperature and humidity evolution simulated by each. In addition, surface meteorological observations of 2 meter temperature and moisture, surface flux towers, and radiosonde-based vertical profiles of temperature and humidity are used for evaluation purposes and obtained from the ARM-SGP program.

Technical Description of Image:

Figure 1: Near-surface soil moisture (0-10cm) valid at 7am on 12 June 2002 as simulated from a 2.5 year spinup of the Noah land surface model (using LIS) over a 1-km horizontal resolution domain in the U.S. Southern Great Plains (SGP). The soil temperature and moisture states generated by this simulation is then used as input to the coupled LIS-WRF simulation over the identical domain. The high-resolution of LIS and its datasets produce improved initial conditions, whose impacts can then be evaluated in the evolution of LIS-WRF variables related to land-atmosphere coupling.

Figure 2: Diurnal co-evolution (7am-7pm) of 2m-specific humidity and 2m-potential temperature on 12 June 2002 as simulated by LIS-WRF for the dry and wet soil moisture locations in Fig. 1 using the Noah land surface model coupled to the YSU, MYJ, and MRF planetary boundary layer (PBL) schemes. The shaded regions for each indicate the model range for each land surface and PBL scheme coupling. Also shown are the vectors that represent the fluxes of heat and moisture from the land surface versus those from the atmosphere due to entrainment.

Scientific significance: The degree of local land-atmosphere coupling (LoCo) is a critical component of prediction models and impacts the simulation of sensible weather, turbulence, convective initiation, and precipitation across a range of scales. This work, funded by the NASA Energy and Water Cycle Study (NEWS) and supported by the NASA MAP and Air Force (AWFA) programs, serves as the backbone for an international effort (GEWEX) to evaluate LoCo in models and observations across the globe. A coupled regional model (WRF) that combines a suite of atmospheric turbulence schemes with a flexible, high-resolution land surface interface (LIS) is used to evaluate the behavior of different land-atmosphere couplings. This work combines unique NASA models with observations to evaluate the significance and accuracy of these interactions and can be applied to any model and location of interest. In turn, this work assesses the impact of land-atmosphere coupling on the variability and simulation of the local, regional, and global hydrological cycle.

Relevance for future science and relationship to Decadal Survey: The diurnal evolution of temperature and humidity near the surface (MODIS, AIRS), in combination with surface flux estimates based on soil moisture estimation (SMAP) and remote sounding of the lower troposphere (AIRS, CALIPSO) will all be provided via remote sensing from NASA platforms in the next decade. Therefore, a simple yet robust technique such as this will enable satellite remote sensing to be used to evaluate land-atmosphere coupling continuously across the globe.


Optical properties of boreal region biomass burning aerosols in central Alaska and seasonal variation of aerosol optical depth at an Arctic coastal site

Thomas F. Eck (Code 614.4 NASA GSFC) and Brent N. Holben (Code 614.4 NASA GSFC)Thomas F. Eck (Code 614.4 NASA GSFC) and Brent N. Holben (Code 614.4 NASA GSFC)

Figure 2: Time series of monthly average AOD at 500 nm by year for the summer and early fall months (June-September) at Bonanza Creek.

Figure 1: Map of Alaska showing the AERONET sites in Alaska and the fires detected by the MODIS sensor on the Terra satellite for the years 2004 through 2007.

Data from long-term monitoring at a central Alaska boreal forest region AERONET site (Bonanza Creek) and seasonal monitoring at a coastal site on the Arctic Ocean (Barrow) were analyzed. Measurements of aerosol optical depth (AOD) at Bonanza Creek from 1994 through 2008 showed extreme inter-annual variability that resulted from episodic major forest fire emissions in dry years as compared to background levels during wet years. Record forest burning extent in the years 2004 and 2005 resulted in monthly average AOD in August of both years that was similar to peak burning season monthly mean AOD in major tropical biomass burning regions.

Absorption by the smoke aerosol in Bonanza Creek in 2004 and 2005 was very weak. The data suggest low black carbon fraction probably due to predominately smoldering combustion (of woody trunks and also soil peat layers), coupled with large fine mode particle radius, which resulted in greater scattering efficiency. Additionally, the relative absorption versus scattering at 440 nm was slightly greater than at the longer wavelengths possibly due to enhanced short wavelength absorption by organic carbon aerosols. This also suggests the possibility that smoke from peat burning may have had a significant influence on aerosol emissions.

0

0.2

0.4

0.6

0.8

1

1994

1996

1998

2000

2002

2004

2006

2008

JunJulAugSep

Aer

osol

Opt

ical

Dep

th (

500

nm

)


Name: Tom Eck and Brent Holben Code 614.4 NASA/GSFC E-mail:[email protected] Phone: 301-614-6625

References:Eck, T. F. , B. N. Holben, J. S. Reid, A. Sinyuk, E. J. Hyer, N. T. O’Neill, G. E. Shaw, J. R. Vande Castle, F. S. Chapin, O. Dubovik, A. Smirnov, E. Vermote, J. S. Schafer, D. Giles, I. Slutsker, M. Sorokine, and W. W. Newcomb (2009), Optical properties of boreal region biomass burning aerosols in central Alaska and seasonal variation of aerosol optical depth at an Arctic coastal site, J. Geophys. Res., 114, D11201, doi:10.1029/2008JD010870.

Holben, B.N. et al., AERONET - A federated instrument network and data archive for aerosol characterization, Remote Sensing of Environment, 66, 1-16, 1998.

Data Sources: The measurements we have analyzed were made by sun-sky radiometers that are a part of NASA’s AErosol RObotic NETwork (AERONET; Holben et al., 1998)), which is a federated global network of standardized radiometers calibrated to consistent reference sources and processed with state of the art algorithms. Over 250 sites located in diverse environments on all continents and oceanic islands are currently a part of AERONET.

The Bonanza Creek AERONET site in central Alaska (20 km west of Fairbanks) has one of the longest monitoring records within the entire network, from 1994 through to the present. A long monitoring record is particularly important in the boreal zone due to the large inter-annual variability in temperature and precipitation. Very dry years have large and numerous wildfires that may produce high concentrations of biomass burning aerosols.

Technical Description of Figures:Figure 1: Map of Alaska showing the AERONET sites at Bonanza Creek in the central boreal forest zone and Barrow on the arctic coast of the Beaufort Sea. Also shown are the fires detected by the MODIS sensor on the Terra satellite for the years 2004 through 2007.[Eck et al., 2009]. Note the very large number of fires detected in 2004 and 2005 as compared to very few observed in 2006 and 2007.

Figure 2: Time series of monthly average AOD at 500 nm by year for the summer and early fall months (June-September) at Bonanza Creek [Eck et al., 2009]. The AOD in August of the drought years 2004 and 2005 are the highest of any month, most likely due larger fires then and possibly also to deeper drying of the soil column in late summer, thus likely increasing the amount of peat that burns.

Scientific significance: Accurate knowledge of aerosol absorption and it’s spectral variation is critical for reducing the current large uncertainties in aerosol radiative forcing on climate, however it is poorly known over many areas of the globe. The biomass burning smoke produced in Alaska in strong burning years had larger fine mode particle size than typical and was found to be more weakly absorbing than other smoke. Additionally, aerosols in the boreal and arctic zone may have significant impact on snow and ice reflectance or albedo due to soot deposition.

Relevance for future science and relationship to Decadal Survey: Aerosol absorption is the most important atmospheric aerosol parameter after aerosol optical depth in characterizing the radiative forcing of aerosols at the earth’s surface and the top of the atmosphere. AERONET retrievals of AOD and single scattering albedo (SSA) have and will continue to be utilized in climate forcing studies and in the validation of current and future satellite missions, such as GLORY that will attempt to measure aerosol absorption from space. Additionally AERONET measurements are made over snow and ice covered polar regions, when it is not possible to obtain accurate retrievals of AOD or SSA from satellite, thereby providing important data that cannot be easily obtained from other observatories.


adélie penguins confront climate change in the ross sea grant ballard, viola toniolo, david ainley,...

Documents