Co2 Cycling in the Coastal Ocean. Ii. Seasonal Organic Loading of the Arctic Ocean from Source Waters in the Bering Sea

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A Lagrangian model of water parcel transit along at 2850-km trajectory from the 80-m isobath of the southeastern Bering Sea to the same depth of the northwestern Chukchi Sea replicates the major seasonal features of nitrogen and carbon cycling on these shelves. Spring-summer extraction of nitrate from the Bering and Chukchi water columns and of CO2 from the atmosphere is followed by fall-winter storage of ammonium and DOC near the shelf-break of the Canadian Basin. Here, the memory of a simulated seasonal range in water parcel contents of 0.2-13.0 μg-at NO3 l-1, 2056-2125 μg at ΣCO2 l-1, 0.3-3.3 μg-at NH4 l-1, and 67-134 μg-at total marine DOC l-1, exiting the Chukchi Sea, is evidently maintained in the halocline of the adjacent Canadian Basin at depths of ~75 m during summer and ~125 m during winter. Based on these properties of imported water parcels, estimated rates of nitrification, DOC oxidation, and ΣCO2 evolution in the Canadian Basin suggest (1) a residence of ~10 y for shelf waters of Pacific origin in the halocline, (2) production of POC within the overlying ice-covered slope waters may indeed be 10-fold larger than first estimates made in the deeper Basin during the 1950s, (3) ~81% of all of the DOC within Bering Strait is of marine origin from prior production cycles in the SBS, and (4) over 50% of the colon signal seen by satellite above these waters is of DOC origin, rather than from phytoplankton pigments.

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Continental Shelf Research, v. 17, issue 1, p. 1-36