Carbonate chemistry of the wintertime Bering Sea marginal ice zone

Abstract

Winter titration alkalinity, total CO 2, pCO 2 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 CO 2, and normalized calcium concentrations but low pCO 2. Total CO 2 data indicated organic carbon production rates of 2.9 ± 1.1 and 2.2 ± 1.1g C m −2day −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 μmol 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 CO 2, but excess CO 2 penetrates to no more than 1000 m in the Aleutian Basin and no excess CO 2 can be found in the Bering Sea Bottom Water. The entire Bering Sea contains 0.19 ± 0.05 × 10 15g 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 CO 2 level. The carbonate deposits on the shelf could then begin to neutralize excess CO 2 and become an important excess CO 2 sink.