Dissolved Inorganic Carbon (δ13C(DIC), [DIC]) in Waters of the Western Bering Sea

For the first time, the isotopic composition and concentration of dissolved inorganic carbon in waters of the western Bering Sea (Koryak shelf and Chukotka continental slope, and Commander Islands, depth range 10-4100 m) have been analyzed. The [DIC] values vary from 1900 mu mol/kg in the summer waters of the Koryak shelf to 2510 mu mol/kg in the deep waters in the area of the Commander Islands. The delta C-13 values of DIC in productive summer waters exceed +1 parts per thousand and reach +3.08 parts per thousand in Koryak shelf surface waters. The depth of the carbon isotope minimum (-0.7 parts per thousand) is approximate to 500 m. The model calculations were made taking into account the physical processes (isotopic exchange with atmospheric CO2 and conservative mixing). The calculations show that the delta C-13(DIC) and [DIC] values in the main water column are governed by oxidation of organic matter. The predominance of primary production occurs only in the surface (<20 m) waters of the Bering Sea. The DIC concentrations increase to depths of approximate to 1000 m and remain approximately constant (2430 +/- 30 mu mol/kg), exceeding [DIC] levels in deep Pacific waters. A "physical carbon pump" model is proposed, in which the main role in the accumulation and redistribution of DIC within the water column is attributed to winter waters of the Bering Sea.