CO2 cycling in the coastal ocean .2. 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 mu g-at NO3 1(-1), 2056-2125 mu g-at Sigma CO2 1(-1), 0.3-3.3 mu g-at NH4 1(-1), and 67-134 mu g-at total marine DOC 1(-1), exiting the Chukchi Sea, is evidently maintained in the halocline of the adjacent Canadian Basin at depths of similar to 75 m during summer and similar to 125 m during winter. Based on these properties of imported water parcels, estimated rates of nitrification, DOC oxidation, and Sigma CO2 evolution in the Canadian Basin suggest (I) a residence time of similar to 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) similar to 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. Copyright (C) 1996 Elsevier Science Ltd