Strong hydrographic controls on spatial and seasonal variability of dissolved organic carbon in the Chukchi Sea

A detailed analysis of dissolved organic carbon (DOC) distribution in the Western Arctic Ocean was performed during the spring and summer of 2002 and the summer of 2003. DOC concentrations were compared between the three cruises and with previously reported Arctic work. Concentrations of DOC were highest in the surface water where they also showed the highest degree of variability spatially, seasonally, and annually. Over the Canada Basin, DOC concentrations in the main water masses were: (1) surface layer (71±4 μM, ranging from 50 to 90 μM); (2) Bering Sea winter water (66±2 μM, ranging from 58 to 75 μM); (3) halocline layer (63±3 μM, ranging from 59 to 68 μM), (4) Atlantic layer (53±2 μM, ranging from 48 to 57 μM), and (5) deep Arctic layer (47±1 μM, ranging from 45 to 50 μM). In the upper 200 m, DOC concentrations were correlated with salinity, with higher DOC concentrations present in less-saline waters. This correlation indicates the strong influence that fluvial input from the Mackenzie and Yukon Rivers had on the DOC system in the upper layer of the Chukchi Sea and Bering Strait. Over the deep basin, there appeared to be a relationship between DOC in the upper 10 m and the degree of sea-ice melt water present. We found that sea-ice melt water dilutes the DOC signal in the surface waters, which is contrary to studies conducted in the central Arctic Ocean.