Dissolved Inorganic Carbon (δ13С(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 μmol/kg in the summer waters of the Koryak shelf to 2510 μmol/kg in the deep waters in the area of the Commander Islands. The δ13С values of DIC in productive summer waters exceed +1‰ and reach +3.08‰ in Koryak shelf surface waters. The depth of the carbon isotope minimum (–0.7‰) is ≈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 δ13С(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 ≈1000 m and remain approximately constant (2430 ± 30 μmol/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.