Eddy transport of organic carbon and nutrients from the Chukchi Shelf: Impact on the upper halocline of the western Arctic Ocean

Abstract

In September 2004 a detailed physical and chemical survey was conducted on an anticyclonic, cold‐core eddy located seaward of the Chukchi Shelf in the western Arctic Ocean. The eddy had a diameter of ∼16 km and was centered at a depth of ∼160 m between the 1000 and 1500 m isobaths over the continental slope. The water in the core of the eddy (total volume of 25 km 3 ) was of Pacific origin, and contained elevated concentrations of nutrients, organic carbon, and suspended particles. The feature, which likely formed from the boundary current along the edge of the Chukchi Shelf, provides a mechanism for transport of carbon, oxygen, and nutrients directly into the upper halocline of the Canada Basin. Nutrient concentrations in the eddy core were elevated compared to waters of similar density in the deep Canada Basin: silicate (+20 μ mol L −1 ), nitrate (+5 μ mol L −1 ), and phosphate (+0.4 μ mol L −1 ). Organic carbon in the eddy core was also elevated: POC (+3.8 μ mol L −1 ) and DOC (+11 μ mol L −1 ). From these observations, the eddy contained 1.25 × 10 9 moles Si, 4.5 × 10 8 moles NO 3 − , 5.5 × 10 7 moles PO 3 − , 1.2 × 10 8 moles POC, and 1.9 × 10 9 moles DOC, all available for transport to the interior of the Canada Basin. This suggests that such eddies likely play a significant role in maintaining the nutrient maxima observed in the upper halocline. Assuming that shelf‐to‐basin eddy transport is the dominant renewal mechanism for waters of the upper halocline, remineralization of the excess organic carbon transported into the interior would consume 6.70 × 10 10 moles of O 2 , or one half the total oxygen consumption anticipated arising from all export processes impacting the upper halocline.