PARTICLE EXPORT AND SCAVENGING IN THE CHUKCHI SEA DERIVED FROM 234TH

The polar waters of the Chukchi Sea are becoming increasingly exposed to sunlight, leading to changes in the timing, magnitude, and composition of the biological food web. These ecosystem modifications will likely alter the overall nutrient load available to the Arctic Ocean, further influencing food web community structure and the exchange of organic carbon between the sediment and water column. To determine spatial and annual shifts of carbon and nutrient fluxes to depth, the short lived radionuclide, thorium-234, and the disequilibrium from its parent element uranium-238, were measured in conjunction with abundances of particulate matter, carbon, nitrogen and phosphorus during two summer cruises (2010 and 2011) in the coastal Chukchi Sea as part of the ICESCAPE (Impact of Climate Change on the Ecosystem and Chemistry of the Arctic Pacific Environment) Program. Preliminary results along the shelf suggest that particle fluxes were highly variable, with ²³⁴Th:²³⁸U disequilibria often reaching the seafloor, suggesting sediment resuspension. In contrast, 2011 was characterized by mostly ice free waters and lower and less variable particle flux due to increased stratification. We hypothesize that lower fluxes in 2011 are the result of sampling towards the end of the bloom season and less bottom resuspension.