Session 040: Ecosystem in Sea Ice Influenced Areas
Chair: Meibing Jin (International Arctic Research Center, UAF, USA. Email: mjin@iarc.uaf.edu)
Co-Chair: Clara Deal (International Arctic Research Center, UAF, USA. Email: deal@iarc.uaf.edu)
Co-Chair: Sang H. Lee (Korea Polar Research Institute, KORDI, Korea. Email: sanglee@kopri.re.kr)
SESSION STATEMENT: The polar and sub-polar marine ecosystems are experiencing rapid changes under the polar-amplified global climate warming. A changing sea ice cover can dramatically alter light availability, water temperature and salinity, water column stability, circulation, timing and magnitude of primary and second production, carbon, DMS and nutrients cycling etc. It is essential to understand how resilient of the marine ecosystem to the changing sea ice cover, and what is the threshold of these changes that can cause a major marine ecosystem shift. All topics addressing the above mentioned issues are encouraged to present in this session. The session will focus on observations and modeling studies of the marine ecosystem in seasonally and perennially ice-covered areas. Interested topics cover researches on primary and second production, carbon, DMS and nutrients cycles in sea ice, in water column under sea ice and after ice retreat. Any study of the broad influences of changing sea ice-associated ecosystem on fisheries, marine mammal and human dimensions are also welcome.
List of Abstracts in the Session (23 in total):
Elliott, S. ., Los Alamos National Laboratory, Los Alamos NM, USA, sme@lanl.gov
Hunke, E. ., Los Alamos National Laboratory, Los Alamos NM, USA, eclare@lanl.gov
Maltrud, M. ., Los Alamos National Laboratory, Los Alamos, USA, maltrud@lanl.gov
As a central component of several marine systems models, the biogeochemical Parallel Ocean Program (POP) has recently been augmented with a dynamic global sulfur cycle. Although most results are encouraging, high latitude processes remain deficient; polar improvements necessarily constitute a next generation emphasis. Based on a blend of available regional simulators, epontic algae and their high DMS production have been implemented within the Los Alamos sea ice model (CICE), which runs interactively with POP and produces Pan-Arctic results in agreement with sparse data. Pelagic ecosystems within POP have been adjusted to reflect dominant high latitude phytoplankton classes including Phaeocystis. The new species are treated as segregated explicit variables competing with diatoms and microbes. Progress will be reported for (1) Arctic simulations conducted in a decoupled cryobiological CICE, (2) the northern polar domain of the POP ocean model, and (3) basin scale, interactive ice-ocean computations. Sensitivity tests include incorporation of biotic absorption of solar radiation within the skeletal layer using multiple scattering radiative transfer. In addition to the Arctic work, preliminary results will be presented for the Southern Ocean.
Oakes, S. A., University of California Santa Barbara, Interdepartmental Graduate Program in Marine Science, Santa Barbara, USA, oakes@lifesci.ucsb.edu
Ross, R. M., University of California Santa Barbara, Marine Science Institute, Santa Barbara, USA, robin@icess.ucsb.edu
Quetin, L. B., University of California Santa Barbara, Marine Science Institute, Santa Barbara, USA, langdon@icess.ucsb.edu
A model to predict growth of individual Antarctic krill (Euphausia superba) during their first and second winters was constructed with experimentally-derived estimates of winter ingestion of water column and sea ice associated food, assimilation efficiency, and respiration. Environmental variables included chlorophyll concentration both in the water column and sea ice, and carbon to chlorophyll ratio of the food. Krill feeding in the water column or at the sea-ice surface was predicted by day length. Net growth rates for individuals were positive or negative depending on initial food conditions. Daily growth rates were consistent with published rates. Model results indicated that while krill can survive or grow under a variety of food conditions, when sea ice is absent krill in their second winter survive or grow at low water-column food concentrations that would not support krill in their first winter. Linking physiological growth models to dynamic models of winter primary productivity would allow prediction of the impact of future changes in annual sea ice production on winter survival of krill.
Jin, M. ., University of Alaska Fairbanks, International Arctic Research Center, Fairbanks, USA, ffjm@uaf.edu
Deal, C. ., University of Alaska Fairbanks, International Arctic Research Center, Fairbanks, USA, deal@iarc.uaf.edu
Wang, J. ., NOAA, Ann Arbor, USA, jia.wang@noaa.gov
Lower trophic level ecosystem model and statistical methods are used to assess the impacts of reducing sea ice cover and rising temperature in the southeastern Bering Sea on the lower tropic level production and fishery catches. The vertically 1-D coupled ice-ocean ecosystem model (Jin et al., 2007) includes both pelagic and sea ice algal components and is applied to the NOAA/PMEL mooring site M2 in the southeastern Bering Sea from 1970 to 2006 forced by wind stress, heat and salt flux. Model results are validated favorably with various observations: 1) temperature, salinity, fluorometer data at 12m, 24m and 44m from 1995-2005; 2) daily SeaWiFS chl a data. While the quantity of variability of the primary production did not show an increase/decrease trend in the past three decade, there exists a shift of dominant phytoplankton species coincident of the Pacific Decadal Oscillation (PDO) index. The model primary production were dominant by ice algae before the 1976/77 regime shift, and by open water species of diatom and flagellates thereafter with only occasional ice algal blooms. Fish catches in the eastern Bering Sea showed mixed reponse to the climate changes. Among the 12 dominant economic fish species, only Walleye pollock and Yellowfin sole showed significant correlations with the PDO index in certain regions. This indicates that a more complicated system analysis is necessary to fully understand the reponse of higher trophic level prodcution to climate changes.
http://people.iarc.uaf.edu:8080/~mbj/
Hoff, K. ., Barnard College, New York, USA, kh2167@barnard.edu
Pfirman, S. ., Barnard College, New York, USA, spfirman@barnard.edu
Tremblay, B. ., Lamont Doherty Earth Observatory, Columbia University and McGill University, Palisades, USA, tremblay@ldeo.columbia.edu
Newton, R. ., Lamont Doherty Earth Observatory, Columbia University, Palisades, USA, bnewton@ldeo.columbia.edu
As the climate warms, Arctic ice extent decreases and food webs shift, Arctic marine mammals will attempt to adapt. Many species will be negatively impacted by habitat loss while others may benefit. Historically, some Arctic mammals, including walrus, inhabited warmer, more southerly ranges, using the Arctic as a refuge from hunting and commercial exploitation. Their previous range may presage adaptations to warmer conditions. In this analysis, we will model projected ice cover, material fluxes and surface temperatures in a doubled CO2 scenario, while representative marine mammal species will be mapped using their full pre-industrial ranges to gauge environmental tolerances. The impact on carrying capacity of the shift of the marginal ice zone to deeper waters will be assessed. As sea-ice retreats and commercial activities in the Arctic surge, it is hoped that such projections will facilitate environmental policies that maximize the ecological potential of a warmer Arctic region.
Chen, J. ., Second Institute of Oceanography, SOA, Hangzhou, China, biogeo_chen@hotmail.com
Li, H. ., Second Institute of Oceanography, SOA, Hangzhou, China, jfchen@hzcnc.com
Because of its sea ice cover the Arctic Ocean has not been considered as a sink of atmospheric carbon dioxide. With recent observations of decreasing ice cover due to global warming there is the potential for an increasing of biological pump efficiency, especially in the Arctic shelf seas. During two cruises of Chinese Arctic Expeditions in summers in 1999 and 2003, we analyzed nutrients, water column/sediment chl a, opal, primary productivity, organic carbon burial rate etc in the Chukchi Sea. Our preliminary results suggest that as one of the largest shelves in the world (one-forth of world shelves), as well as its sufficient nutrients supply (north Pacific Ocean, large rivers), Arctic Ocean might play a very important role in global carbon sink when sea ice shrinks.
Russell, J. L., University of Arizona, Tucson, USA, jrussell@email.arizona.edu
Ainley, D. G., H.T. Harvey and Associates, Los Gatos, USA, dainley@penguinscience.com
Goodman, P. J., University of Arizona, Tucson, , pgoodman@email.arizona.edu
Using observations of Adelie and Emperor penguins and their needs for nesting and food as guidelines, we examine how the IPCC-AR4 coupled climate models predict that their habitat will be altered under global warming scenarios. Russell et al. (2006) compared 18 of the coupled climate models included in the latest IPCC report on the basis of how well they simulated the Southern Ocean circulation. That study used the strength of the Antarctic Circumpolar Current as a proxy for the overall health of the model simulation. In that analysis the most important factor to determining the quality of the ACC simulation was the strength and position of the Southern Hemisphere westerly winds. In this complementary analysis, we will address which of the AR4 climate model simulations of the Southern Ocean best represent the distribution and seasonality of sea ice, what changes are projected in the ocean circulation, sea ice extent seasonality and thickness around Antarctica under global warming conditions and what are the implications for ice-obligate species of penguins, like the Adelie and Emperor.
Jinping/Zhao, J. ., Ocean University of China, Qingdao, China, jpzhao@ouc.edu.cn
Jacqueline/Grebmeier, J. M., University of Tennessee, Knoxville, USA, jgrebmei@utk.edu
Yutian/Jiao, Y. ., Ocean University of China, Qingdao, China, jiaoyutian@ouc.edu.cn
Related to the global warming, sea ice in area, thickness, and concentration is obviously decreasing. Along with less sea ice in winter and early melting in spring, the marine ecosystem in northern shelf of Bering Sea is experiencing corresponding changes. As ice opens earlier than usual, Algae grow firstly in brighter upper level in a short time and then move to the lower level with the exhaustion of surface nutrition. The optical multi-spectrum attenuation coefficients by duplicate observation in May to June, 2007, reflect the variation. The spectral fluorescence emitted by phytoplankton provides the other information in distinguishing different kind of algae. On the other hand, solar radiation is the main energy to melt sea ice. The earlier bloom of phytoplankton changes the light field in seawater and increases solar absorption, which results in extra warming, a positive feedback to the ice melting. The solar radiation penetrated is also the main source for heating lower water. The linkage among thermal, optical and ecological features in northern Bering Sea is discussed in this paper to address the contribution of phytoplankton to ice retreats.
Mei, Z. ., University of Quebec at Rimouski, Rimouski, Canada, zmei@mta.ca
Saucier, F. ., University of Quebec at Rimouski, Rimouski, Canada, francois_saucier@uqar.qc.ca
Zakardjian, B. ., University of Quebec at Rimouski, Rimouski, Canada,
Primary production in the NPZD models is usually formulated as either light- or nutrient limited, and zooplankton growth, as prey limited. However, the importance of temperature regulation of phytoplankton and zooplankton growth re-emerged during early and recent data synthesis, which suggest that differential response of phytoplankton and zooplankton growth to temperature account for distribution of phytoplankton spring bloom of the global ocean by affecting the coupling between primary and secondary producers. Primary and secondary production of Gulf St Lawrence (Canada) are simulated with and without temperature control are conducted in this study. Temperature regulation changed spatial distribution, the timing and extent of spring phytoplankton bloom, primary and secondary production remarkably, which have significant implications to the coupling between primary and secondary production, carbon flux and interannual variation of biological productivity of marine ecosystems in response to climate change.
Grebmeier, J. M., University of Tennessee, Knoxville, USA, jgrebmei@utk.edu
Cooper, L. W., University of Tennessee, Knoxville, USA, lcooper1@utk.edu
Pirtle-Levy, R. ., North Carolina State University, Raleigh, USA, rpirtlel@utk.edu
Brown, R. S., University of Tennessee, Knoxville, USA, rbrown12@utk.edu
Lovvorn, J. R., University of Wyoming, Laramie, USA, lovvorn@uwyo.edu
Variable sea ice duration, low seawater temperature, and low zooplankton populations in the spring in the northern Bering Sea result in high export of labile organic carbon to the sediments. Both sediment oxygen uptake (short-term indicator of carbon supply to the benthos) and benthic biomass (longer-term indicator of carbon export) respond at different time scales to organic carbon reaching the sediments. Approximately 60 experimental stations were occupied in 2006 and 2007 on USCGC Healy as part of a continuing multi-decadal effort to assess status and change in the highly productive northern Bering Sea benthic ecosystem. Sediment oxygen uptake ranged from <1-27.8 mmol O2m-2 d-1, and reoccupation of some stations during the cruise facilitated tracking the timing and impact of export production on the benthic system as sediment oxygen uptake rates increased following organic carbon deposition from the spring bloom. Measurements of benthic infaunal biomass (2.2-48.1 g C m-2) show that the dominant bivalve, polychaete and amphipod communities vary depending upon overlying water masses and sediment type, but overall biomass has declined, possibly as a result of changing environmental conditions.
Cooper, L. W., University of Maryland Center for Environmental Science, Solomons , USA, cooper@cbl.umces.edu
Janout, M. ., University of Alaska Fairbanks, Fairbanks, USA, janout@sfos.uaf.edu
Grebmeier, J. M., University of Tennessee, Knoxville, Knoxville , USA, jgrebmei@utk.edu
Frey, K. E., Clark University, Worcester, USA, kfrey@clarku.edu
Pirtle-Levy, R. ., North Carolina State University, Raleigh, USA, rpirtlel@utk.edu
Lovvorn, J. R., University of Wyoming, Laramie, USA, lovvorn@uwyo.edu
The benthos of the northern Bering Sea shelf is dominated by a world-class biomass of soft-bottom macrofauna as well as important epifaunal assemblages. The likely basis for this high sustained benthic biomass is the intense spring bloom, but few observations are available that have followed the direct sedimentation of this rich organic material during and after the bloom peak in May. MODIS satellite imagery, water column chlorophyll concentrations and surface sediment chlorophyll inventories were used to document the dynamics of sedimentation to the sea floor in both 2006 and 2007. An atmospherically-derived radionuclide, 7Be, that is deposited in surface sediments as ice cover retreats was used to supplement these observations, as were studies of light penetration and nutrient depletion in surface waters as the bloom progressed. Tight linkages among sea ice retreat, chlorophyll biomass, water mass structure and particulate sedimentation on the sea floor suggest that significant shifts in benthic ecosystem productivity and impacts on the associated benthic based foodweb can be expected with continued seasonal sea ice retreat in the northern Bering Sea.
Hufford, G. L., National Weather Service, Anchorage, USA, gary.hufford@noaa.gov
Ray, G. C., University of Virginia, Charlottesville, USA, cr@virginia.edu
Frey, K. E., Clark University, Worcester, USA, kfrey@clarku.edu
Labunski, E. ., US Fish and Wildlife Service, Anchorage, USA, elizabeth_labunski@fws.gov
Beringian sea ice is projected to disappear by the end of the century due to climate change. AVHRR and MODIS satellite imagery and shipboard observations (USCGS Healy cruises, 2006 and 2007) confirm that Pacific walruses prefer “broken pack” and ribbon seals prefer “loose pack” for reproduction and molting. A seascape approach shows that these sea-ice habitats have diminished from the 1990s, becoming more chaotic due to large areas of open water, and allowing sea-ice types to become mixed due to fluxes in wind and ocean currents. Tracking of ice floes known to have walruses and seals present show dramatic differences between the two years, as well as some similarities; e.g., ice-floe movements were dominated by ocean currents in 2006 and by winds in 2007. We predict that the high variability of sea-ice conditions among years and a trend towards reduction of sea-ice habitat will play reinforcing roles, and that the highly variable and poorly structured conditions observed in 2006 and 2007 will become more common in the future, with serious implications for these species’ populations.
Cui, X. ., University of Tennessee, Knoxville, USA, xcui1@utk.edu
Grebmeier, J. M., University of Tennessee, Knoxville, USA, jgrebmei@utk.edu
Cooper, L. W., University of Tennessee, Knoxville, USA, lcooper1@utk.edu
Lovvorn, J. R., University of Wyoming, Laramie, USA, lovvorn@uwyo.edu
North, C. A., University of Wyoming, Laramie, USA, cnorth@uwyo.edu
Kolts, J. M., University of Wyoming, Laramie, USA, jkolts@uwyo.edu
Bottom water temperature increases are thought to be influencing northward fish range expansion and altering fish community structure in the Bering Sea north of St. Matthew Island as seasonal sea-ice becomes less prominent. During two icebreaker cruises on the USCGC Healy (7 May - 5 June 2006 and 16 May - 18 June 2007), groundfish were collected at 43 stations in 2006 (59 otter trawls), and 52 stations in 2007 (72 beam and 17 otter trawls). Arctic cod (Boreogadus saida), Bering flounder (Hippoglossoides robustus) and Snailfish (Liparidae) are the dominant fish in the northern Bering Sea. Patterns in species distribution and abundance (catch per unit area) are being analyzed in the context of prey items and environmental variables, such as bottom water temperature, salinity, and nutrient concentrations, along with sediment grain size and carbon content. Results indicate that groundfish may be competing for some of the same benthic food resources as are used by specialist benthic predators such as walrus, gray whale, bearded seals and spectacled eiders that feed on macrofauna in the rich Bering Sea sediments.
Lovvorn, J. R., University of Wyoming, Laramie, USA, lovvorn@uwyo.edu
Grebmeier, J. M., University of Tennessee, Knoxville, USA, jgrebmei@utk.edu
Cooper, L. W., University of Tennessee, Knoxville, USA, lcooper1@utk.edu
Richman, S. E., University of Wyoming, Laramie, USA, cruciger@uwyo.edu
Bump, J. K., University of Wyoming, Laramie, USA, jkbump@mtu.edu
Sirenko, B. I., Zoological Institute, S. Petersburg, Russian Federation, marine@zin.ru
The world population of Spectacled Eiders, a threatened species, winters in pack ice of the Bering Sea. To assess possible factors in the eiders’ population decline, we used historical data on benthic prey, sea ice, and weather in a simulation model of eider energetics that integrated field, laboratory, and remote sensing studies. Density and duration of leads in the pack ice during extreme versus average winters had little net effect on eider energy balance, as flight distance to other leads was usually short when leads closed. Nighttime cost was greatly reduced by the eiders’ resting on ice versus floating on water, but this factor was likely unimportant during the eider decline (1970s to 1990s). Despite a major shift in dominance of major prey species, food did not appear to be limiting at the beginning or end of the eiders’ decline. After a decade of poor bivalve recruitment, the area of viable habitat for eiders decreased dramatically between the early 1990s and early 2000s. Reduced prey availability and projected loss of ice for nighttime roosting may decrease the eiders’ prospects of recovery.
http://uwacadweb.uwyo.edu/Lovvorn/
Mathis, J. T., University of Alaska Fairbanks, Fairbanks, USA, jmathis@sfos.uaf.edu
Bates, N. R., Bermuda Institute of Ocean Sciences, , Bermuda, nick.bates@bios.edu
Hansell, D. A., University of Miami - RSMAS, Miami, USA, dhansell@rsmas.miami.edu
The Chukchi shelf is the site of some of the highest rates of primary production in the global ocean. In late spring and summer of 2002, rates of net community production over the shelf were as high as 2,000 mg C m-2 d-1, and averaged 800 mg C m-2 d-1 across the entire shelf. Using conservative tracers to construct a carbon mass balance, we found that 10% of the DIC consumed during net community production was converted to DOC and 15% was converted to suspended POC. The remaining 75% was exported from the mixed layer as sinking organic particles. At the termination of the bloom, nitrate concentrations had been reduced to near zero and most of the organic matter had been exported from the mixed layer, leaving surface waters undersaturated with respect to atmospheric CO2. Presently, these shelf surface waters are transported offshore beneath the permanent ice cover before any significant re-equilibration with atmospheric CO2 can occur. As such, the biological pump on the Chukchi shelf plays an important role in conditioning the highly oligotrophic waters of the Canada Basin. If the forecasted reduction in Arctic sea ice occurs then this basin will initially act as strong sink for atmospheric CO2 by allowing the re-equilibration. However, the depletion of nutrients from shelf processes will continue to limit any significant biological activity prohibiting the deep central Arctic Ocean from being a long term sink of that CO2.
Aakerman, H. J., Lund University, LUND, Sweden, jonas.akerman@nateko.lu.se
Changes in the sea-ice conditions long the west coast of Svalbard has during the last decades changed and affected conditions ashore. The effect upon the discharge characteristics of small drainage basins close to the seashore are discussed. The area studied is situated on the coastal plain, south of Kapp Linne’ (78o 04’ N, 13 o 38’ E,) with special focus on the anomalous discharge pattern of the Fyrsjöen Lake catchment area. The drainage of the lake is with increased frequency blocked by ice-cemented storm ridges delaying the spring and snowmelt peak flow. Vast areas are flooded, affecting vegetation and breeding birds of the area. The Lake is then, dramatically tapped during one or two days with heavy flow, after which the discharge pattern returns to normal. This process, is not unique here but rather common along the west coast of Spitsbergen. These special conditions have a clear influence on the active layer, the permafrost and, the vegetation and the bird colonies of the area.
http://jonas.akerman@nateko.lu.se
Caissie, B. E., University of Massachusetts Amherst, Amherst, USA, bethc@geo.umass.edu
Brigham-Grette, J. ., University of Massachusetts Amherst, Amherst, USA, juliebg@geo.umass.edu
The dramatic reduction in ice extent seen this summer in the Arctic Ocean highlights the need to understand natural rates of change of declining sea-ice extent and duration. To address this, we are developing a quantitative proxy for paleo-ice duration in the Bering Sea. A suite of surface sediments taken onboard the USCGC Healy 0601 and 0702 expeditions from a grid of stations across a gradient of sea-ice duration (historically ranging from four to nine months of ice cover per year) were analyzed for sediment grain size and diatom assemblages. These sites were then combined with a diatom assemblage dataset of surface sediments previously taken from the Bering Sea (Sancetta 1982). This combined dataset now includes sites representative of a full sea-ice duration gradient (zero to twelve months of ice per year). Several methods of machine based learning will be applied to the dataset to correlate these and other surface sediment variables (including diatom assemblages and morphology, sediment grain size, and the concentration of an organic compound associated with sea ice diatoms) with mean annual duration of sea ice.
Lee, S. H., Korea Polar Research Institute, Incheon, Republic Of Korea, sanglee@kopri.re.kr
Stockwell, D. A., IMS, UAF, Fairbanks, USA, dean@ims.uaf.edu
Whitledge, T. E., IMS/UAF, Fairbanks, USA, terry@ims.uaf.edu
Chung, K. H., Korea Polar Research Institute, Incheon, Republic Of Korea, khchung@kopri.re.kr
Kang, S. H., Korea Polar Research Institute, Incheon, Republic Of Korea, shkang@kopri.re.kr
Although ongoing changes in climate and ice conditions are expected to alter the carbon and nitrogen uptake rates of phytoplankton as primary producers in the Arctic Ocean, recently a few measurements have been done in the Canada Basin. The expedition in 2005 allowed us to provide a valuable data for the uptake rates of phytoplankton under the sea ice from in situ incubations, compare them with the 2002 data under different environmental conditions in the same basin, and form a backbone for any future discussion of impacts of global warming on the primary productivity in the region. The patterns of nutrient concentrations were similar, whereas the surface water temperature patterns were quite different between the two data sets in 2002 and 2005. Since stronger light intensity through the sea ice reached to the ice bottom in 2005, the carbon and nitrogen uptake rates of phytoplankton under the sea ice were higher in 2005 than in 2002. The mean f-ratio from this study in 2005 was 0.31 (±0.12) which is within the range in the Arctic Ocean.
Warren, C. E., University of Tennessee, Knoxville, USA, cwarren6@utk.edu
Grebmeier, J. M., University of Tennessee, Knoxville, USA, jgrebmei@utk.edu
Cooper, L. W., University of Tennessee, Knoxville, USA, lcooper1@utk.edu
Community structure and biodiversity of benthic infaunal invertebrates were investigated in July 2007 on the icebreaker CCGS Sir Wilfrid Laurier as part of a joint US-Canadian International Polar Year program C3O (Canada’s Three Oceans) in the Bering, Chukchi and Beaufort Seas. These efforts took advantage of, and continue, longer-term decadal studies of biological change in this Arctic system, particularly documenting significant declines in populations and biomass of Arctic invertebrates in the sediments that may represent biological responses to warming water temperatures and other hydrographic changes. This presentation will include data on benthic infaunal abundance and biomass that were determined following sediment oxygen demand incubations of large diameter (133 cm2) cores. In addition, surface sediment characteristics including sediment grain size, inventories of chlorophyll deposited to the sea floor and organic carbon content influence benthic infaunal diversity. Data will be presented showing statistical relationships linking environmental factors to benthic community structure.
Deal, C. ., Unversity of Alaska Fairbanks, Fairbanks, USA, deal@iarc.uaf.edu
Jin, M. ., University of Alaska Fairbanks, Fairbanks, USA, mjin@iarc.uaf.edu
Wang, J. ., NOAA/Great Lakes Environmental Research Lab, Ann Arbor, USA, jiawang@noaa.gov
In recent years, modeling of both pelagic and sea ice regimes has revealed new insights into life at the dynamic interface between sea ice and water. Central to these modeling studies are field investigations, which are for the most part scarce in the Arctic. However, two sites on the Alaskan shelves have yielded and continue to provide biophysical multi-year time series observations that are crucial to the modeling work. This presentation will provide an overview of numerical modeling studies conducted through collaborations in recent years for the landfast ice ecosystem in the Chukchi Sea and the ice-ocean ecosystem in the fluctuating ice margin of the Bering Sea. Using the one-dimensional model, physical controls on biota are assessed, and hypotheses, such as seeding of the phytoplankton bloom by ice algae, investigated. Work in progress, including the addition of a sea ice microbial loop, will also be presented. This new component of the model will help to investigate the partitioning of sea ice primary production between the pelagic, benthic and sea ice microbial realms under climate change.
Vernet, M. ., Scripps Institution of Oceanography, La Jolla, USA, mvernet@ucsd.edu
Martinson, D. ., Lamont-Doherty Earth Observatory, Palisades, USA, dgm@ldeo.columbia.edu
Iannuzzi, R. ., Lamont-Doherty Earth Observatory, Palisades, USA, iannuzzi@ldeo.columbia.edu
Stammerjohn, S. ., Columbia University, New York, USA, sstammerjohn@giss.nasa.gov
Kozlowski, W. ., Scripps Institution of Oceanography, La Jolla, USA, wkoz@ucsd.edu
Sines, K. ., Scripps InstitutionoOceanography, La Jolla, USA, ksines@ucsd.edu
Smith, R. C., University of CaliforniaSanta Barbara, Goleta, USA, ray@icess.ucsb.edu
Garibotti, I. ., Instituto Argentino de Nivologia, Gaciologia y Ciencias Ambientales, Mendoza, Argentina, ireneg@lab.cricyt.edu.ar
In shelf waters west of the Antarctic Peninsula (wAP), with abundant macro- and micronutrients, water column stability due to freshwater input from sea ice melting has been suggested as a key factor controlling primary production. The area is subject to the annual advance and retreat of sea ice characteristic of Antarctic waters. A 12-year time series (1995-2006) was analyzed to study spatial and temporal patterns in primary production as well as major environmental determinants. A strong onshore-offshore gradient is evident along the Peninsula at the height of the growth season with higher production observed in inshore waters. Regional production varied inter-annually by a factor of 7. Mixed layer depth shows the higher correlation with production while late sea ice retreat explains 58% of the variability in space and time. No regional trend in primary production was detected during this period. We discuss the influence of sea ice retreat and water masses in determining summer mixed layer depth.
http://polarphytoplankton.ucsd.edu
White, B. A., University of Minnesota, Minneapolis, USA, white805@umn.edu
Matsumoto, K. ., University of Minnesota, Minneapolis, USA, katsumi@umn.edu
Austin, J. ., University of Minnesota - Large Lakes Observatory, Duluth, USA, jaustin@d.umn.edu
The physical and biogeochemical systems in mid-latitude lakes are tightly coupled due to strong seasonal forcings. The impact of climate change on these systems and their interactions is poorly understood. We examine the consequences of trends of winter ice cover decrease and unexpectedly rapid rates of surface water temperature increase on the carbon cycle of Lake Superior using the Regional Oceanic Modeling System (ROMS). This dynamical, three dimensional model has been configured to reflect conditions in Lake Superior. Included are an ice submodel and a carbon submodel. The carbon model features introduction of carbon via air-lake gas exchange and a dynamical food web. The food web architecture is based on the Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD) model of Fasham et al. 1990 but is being altered to match the phosphorus limited state of freshwater lakes. We will report on the results of our sensitivity experiments examining the effects of winter ice on seasonal carbon dynamics in Lake Superior.
Humphrey, A. B., University of Tennessee, Knoxville, USA, adamhumphrey@gmail.com
Grebmeier, J. M., University of Tennessee, Knoxville, USA, jgrebmei@utk.edu
Cooper, L. W., University of Tennessee, Knoxville, USA, lcooper1@utk.edu
The northern Bering Sea is a productive shelf ecosystem, in part because sea ice dynamics and primary production in the spring are intimately tied to export of labile organic carbon to the benthos. The rich benthic community supports large benthic predators (e.g., epibenthic crabs and snails, diving seaducks and marine mammals). Near-annual sampling over the past twenty years indicates a transition in the dominant bivalve from the large, thin-shelled Macoma calcarea to the comparatively smaller, thicker-shelled Nuculana radiata in addition to declining trends in overall benthic infaunal biomass. Changes in benthic community structure are being analyzed through similarity cluster analysis (Bray-Curtis index) to group stations from 16 oceanographic cruises over the past twenty years. Ordination through non-metric multi-dimensional scaling is used to analyze infaunal abundance in these benthic populations over time. In addition, station group separation is being evaluated with ecological parameters, such as sea ice cover/duration, hydrographic parameters, sediment variables, and spatial trends using the Geostatistical Analyst function of ArcGIS software. Results will be presented that evaluate potential forcing factors for the benthic changes being observed in this system.
Saenz, B. L., Stanford University, Stanford, USA, blsaenz@stanford.edu
Arrigo, K. R., Stanford University, Stanford, USA, arrigo@stanford.edu
We constructed a coupled physical-biological model describing Antarctic sea ice dynamics and associated ice algal production. Using satellite-derived ice cover, snow depth, and ice advection, as well as climatological light and atmospheric forcing, the model grows and melts sea ice using a multi-layer approach to create a reasonably realistic sea ice environment. Internal ice conditions (e.g., temperature, nutrients, and salinity) and a multi-spectral optical model of light attenuation are used to characterize the algal growth environment in discrete model layers. The model domain covers a portion of the southern hemispheric EASE grid. Each grid cell (625 km2 resolution) moves horizontally using a mass-conservative advection scheme and contains an independent 1-D ice-algal model. Single-station results confirm that the model reproduces physicochemical ice conditions and algal concentrations consistent with observed values. Using available daily forcing data (1997-2003), we have created a standard model run that provides high-resolution estimates of algal growth and carbon uptake through time. Model results can assist calculation of Southern Ocean carbon budgets and provide insight into trophic relationships that depend on sea ice.