CARBONATE CHEMISTRY OF THE WINTERTIME BERING SEA MARGINAL ICE-ZONE

Winter titration alkalinity, total CO2, PCO2 and calcium profiles across the marginal ice zone of the central and southeastern Bering Sea shelf were obtained for the first time. The data indicate that Bering Sea Shelf Water was significantly affected by river runoff, and conservative mixing dominated the distribution of physical-chemical properties on the shelf. Low salinity waters had high normalized alkalinity, normalized total CO2, and normalized calcium concentrations but low PCO2. Total CO2 data indicated organic carbon production rates of 2.9 +/- 1.1 and 2.2 +/- 1.1 g C m-2 day-1, respectively, on the shelf and in the Aleutian Basin between March and June. Calcium data suggested a vertical inorganic carbon flux of 0.075 mumol kg-1 y-1, which represents approximately 35% of the total carbon flux in the Aleutian Basin. The entire Bering Sea Shelf Water was saturated by the anthropogenic CO2, but excess CO2 penetrates to no more than 1000 m in the Aleutian Basin and no excess CO2 can be found in the Bering Sea Bottom Water. The entire Bering Sea contains 0.19 +/- 0.05 x 10(15) g anthropogenic carbon. The shelf water is now supersaturated with respect to calcite and aragonite, but could become undersaturated with a doubling of the current atmospheric CO2 level. The carbonate deposits on the shelf could then begin to neutralize excess CO2 and become an important excess CO2 sink.