Determining net dissolved organic carbon production in the hydrographically complex western Arctic Ocean

Abstract

Each spring and summer, the Chukchi Sea in the western Arctic Ocean experiences a short but intense phytoplankton bloom that is controlled by sea ice cover, nutrient availability, and river runoff. During the bloom, dissolved inorganic carbon (DIC) concentrations are drawn down in the mixed layer (shelf, ~Δ100 µmol kg −1 ; shelf‐break, ~Δ50 µmol kg −1 ; basin, −1 ) and converted to particulate organic carbon (POC) and dissolved organic carbon (DOC). We use δ 18 O and salinity to estimate DOC inputs by river and sea ice melt, allowing the marine portion of the DOC pool to be compared between seasons and to facilitate estimates of net DOC production in the region. We estimate that ~10% of the DIC consumed during net community production is converted to DOC. The remaining carbon deficit (90% of DIC drawdown) is most likely exported from the mixed layer as POC. In 2002 a carbon (C) mass balance was developed for the Chukchi Sea that showed that rates of vertical export were highest over the Chukchi Shelf near Point Barrow (64 mmol C m − d −1 ), but more commonly ranged from 10 to 35 mmol C m − d −1 over the remainder of the shelf. At the shelf‐break and in the Canada Basin export production was − d −1 . DOC plays a relatively small role as a carbon sink in the system, but quantifying its contributions provides more robust estimates of export production in the Arctic.

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