HR: 0800h
AN: B51C-0601    [Abstracts]
TI: Carbon Biogeochemistry in the Western Arctic Ocean and Inferences on an Ice Free Arctic Ocean
AU: * Mathis, J T
EM: jmathis@sfos.uaf.edu
AF: University of Alaska Fairbanks, SFOS 245 ONL Bldg 905 North Koyokuk, Fairbanks, AK 99775, United States
AU: Bates, N R
EM: nick@bbsr.edu
AF: Bermuda Institute of Ocean Sciences, 17 Biological Lane, St. George's, GE 01, Bermuda
AU: Hansell, D A
EM: dhansell@rsmas.miami.edu
AF: University of Miami-RSMAS, 4600 Rickenbacker CSWY, Miami, FL 33149, United States
AB: The Chukchi shelf is the site of some of the highest rates of primary production in the global ocean. Each spring, seasonal ice cover retreats and exposes nutrient-rich waters to near continuous sunlight stimulating an intense biological bloom. In 2002, rates of net community production over the shelf were as high as 2,000 mg C m-2 d-1 near Barrow Canyon, and averaged 800 mg C m-2 d-1 across the entire shelf. During this time, concentrations of DOC and POC increased from in situ production and terrestrial fluxes. 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.
DE: 4805 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4912)
DE: 4806 Carbon cycling (0428)
DE: 4808 Chemical tracers
DE: 4815 Ecosystems, structure, dynamics, and modeling (0439)
DE: 4845 Nutrients and nutrient cycling (0470, 1050)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting