CO2 cycling in the coastal ocean. II. Seasonal organic loading of the Arctic Ocean from source waters in the Bering Sea

A Lagrangian model of water parcel transit along a 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 μ-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 DOCl-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 time 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 color signal seen by satellite above these waters is of DOC origin, rather than from phytoplankton pigments.