Physical-biological control of primary production in Beaufort and Chukchi Sea ice: Its contribution to shelf-basin interactions in the western Arctic

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0125464GradingerThis interdisciplinary proposal aims to quantify sea ice primary production in the Chukchi and Beaufort seas. The main working hypotheses are that both light and nutrient supply control biomass formation within the sea ice. While irradiance controls the rate of biomass change in spring and autumn, nutrient advection dominates during summer as meltwater accumulation below the ice impedes nutrient supply and hence limits the total biomass accumulation in the ice cover. To verify these hypotheses the project combines field studies, laboratory experimental work and remote sensing observations. This approach is designed to quantify the ice-related biogeochemical processes and to supply a regional, seasonally varying estimate of carbon accumulation in, and release from, the ice cover. The shipboard work will take place during two spring-summer (May-August) expeditions when physical, chemical and biological parameters will be measured at locations encompassing the prevalent ice types. Ice thickness and structure will be determined using an indirect measurement technique along transects varying in length from hundreds to thousands of meters. Ice cores will be analyzed to determine the vertical distributions of salinity, temperature, stable isotope concentrations, algal pigment concentrations and species composition. Primary production will be determined using optical and tracer techniques. Laboratory experimental work will assess the relationships among ice physics, chemistry and algal activity and to extrapolate results of the field measurements to early spring and late summer when shipboard sampling is more difficult. Integration of remote sensing data will contribute to regional estimates of ice algal production and its temporal and spatial variability within the study region. This proposal contributes to the goals of the western Arctic Shelf-Basin Interaction program by assessing the regional contribution of ice-associated primary production and consequent accumulation and release of carbon from the ice to the adjacent water column system. Results are expected to help in understanding and quantifying the ice algal community response to climate variations.