SBI Phase 2 OPP-0125464 Physical-biological control of primary production in Beaufort and Chukchi Sea ice: Its contribution to shelf- basin Arctic interactions in the western Arctic The Arctic shelves in general are highly productive seas, sustaining high biomass of pelagic and benthic biota. The seasonal sea ice cover plays a key role not only as a habitat but also in structuring physical and biological processes in these high-latitude systems. Reduction in sea ice extent is one of the major anticipated consequences of climate change in the Arctic. Arctic marine systems are challenged by a large-scale warming trend and a substantial loss of ice extent recorded over the past decades. The regional focus of the Shelf-Basin Interac-tions (SBI) program offers a unique opportunity to study the linkages between physical, chemical and biological oceanography in the Chukchi and Beaufort Seas in order to predict the impact of climate variability and change. This interdisciplinary proposal aims to quantify the sea ice primary production in the Chukchi and Beaufort Seas. The main working hypotheses are that both light and nutrient supply control the magnitude of biomass formation within the sea ice. While irradiance controls the rate of biomass changes in spring and autumn, nutrient advection is dominant during summer as melt water accumulation below the sea ice impedes nutrient supply and hence controls the total integrated biomass build- up in the ice cover. To verify these hypotheses we combine field studies, experimental work, and remote sensing efforts. Through this comprehensive approach we anticipate to quantify the ice-related biogeochemical processes and supply an estimate of carbon production and release from the seasonally varying ice cover. During two ship expeditions (May - August) an extensive data set of physical, chemical and biological parameters will be obtained at sampling locations comprising the prevailing ice types. Ice thickness and morphology will be determined with an indirect measurement technique along transects of several hundreds to thousands of meters in length. Profiles of salinity, temperature, stable isotope concentrations, algal pigments and species composition will be determined over the entire ice thickness based on ice cores. Primary production will be deter-mined by optical and tracer techniques. Our experimental work aims to elucidate the relationships between ice physics, chemistry and algal activity, to extend our estimates to early spring and late summer, when ship- based sampling is difficult. This proposal contributes to the overall aims of SBI in assessing the contribution of ice- associated primary production and biomass build-up and release from the ice to the total carbon flow in the system. It will help in understanding and quantifying the response of ice-algal communities to climate variability and change, and in particular how this impacts the overall system. The work also ties into the pelagic and benthic stud-ies carried out within the framework of SBI, as key physical, chemical and biological ice characteristics will be determined, allowing, e.g., to trace the fate of sea ice production in the pelagic and benthic realms. Physical/chemical/biological sea ice characteristics in the Chukchi and Beaufort Sea The data set consists of the sea ice measurements conducted at 17 stations between May 10 and June 9 2002 including location, snow thickness, ice temperature, salinity, nutrients, chlorophyll a (chl a), phaeopigments and particulate organic carbon (POC) and nitrogen (PON) values. The data set for each station is presented on one separate worksheet within the spreadsheet. MS Excel X for MAC Data are presented in an Excel spreadsheet. All units for all parameters are provided within the spreadsheet. 20020510 20020608 ice thickness, snow thickness, ice temperature, ice salinity, ice nutrient concentration, chlorophyll a, particulate organic carbon, particulate organic nitrogen, light, surface water temperature, Chukchi Sea, Beaufort Sea 74N, 67N, 169 W, 154W http://www.sfos.uaf.edu/research/seaicebiota/SBI2/index.html Sea-ice apparent conductivity, sea-ice thickness, snow depth, deteriorated ice layer depth, melt-pond depth, ice freeboard Ice cores were collected with a KOVACS-type ice auger (10 cm diameter). Ice temperature was measured in small drill holes at 5 to 10 cm intervals over the entire ice thickness with a Traceable thermometer (accuracy of 0.05 °K) immediately after coring. The entire cores were sectioned in segments of variable lengths and completely melted directly in the dark for salinity, nutrient, and POC/PON. Chl a analysis was conducted fluorometrically after melt water was filtered through GF/F filters. POC/PON values were measured using a ThermoFinnigan Delta mass spectrometers. Nutrient concentrations were measured onboard the HEALY by the SBI nutrient team. PAR (photosynthetically active radiation) intensity was measured with a LI-COR underwater 4d sensor, T and S below the ice was determined with an YSI85 sensor.