Linkages among runoff, dissolved organic carbon, and the stable oxygen isotope composition of seawater and other water mass indicators in the Arctic Ocean

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Read Full Article (file size: 2134787 bytes) Cited by JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, G02013, doi:10.1029/2005JG000031, 2005 Linkages among runoff, dissolved organic carbon, and the stable oxygen isotope composition of seawater and other water mass indicators in the Arctic Ocean Lee W. Cooper Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, Tennessee, USA Ronald Benner Department of Biological Sciences and Marine Science Program, University of South Carolina, Columbia, South Carolina, USA James W. McClelland Marine Biological Laboratory, Woods Hole, Massachusetts, USA Bruce J. Peterson Marine Biological Laboratory, Woods Hole, Massachusetts, USA Robert M. Holmes Woods Hole Research Center, Woods Hole, Massachusetts, USA Peter A. Raymond School of Forestry and Environmental Science, Yale University, New Haven, Connecticut, USA Dennis A. Hansell Division of Marine and Atmospheric Chemistry, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida, USA Jacqueline M. Grebmeier Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, Tennessee, USA Louis A. Codispoti University of Maryland Center for Environmental Science, Cambridge, Maryland, USA Abstract Flow-weighted dissolved organic carbon (DOC) concentrations and δ¹⁸O values were determined from major arctic rivers, specifically the Ob, Yenisey, Lena, Kolyma, Mackenzie, and Yukon during 2003–2004. These data were considered in conjunction with marine data for DOC, δ¹⁸O values, nutrients, salinity, and fluorometric indicators of DOC obtained during sampling at the shelf-basin boundary of the Chukchi and Beaufort seas. On the basis of these data, freshwater in the sampled marine waters is likely derived from regional sources, such as the Mackenzie, the Bering Strait inflow, and possibly eastern Siberian rivers, including the Kolyma, or the Lena, but not rivers farther west in the Eurasian arctic. Freshwater from melted sea ice is insignificant over annual cycles, although melted sea ice was a locally dominant freshwater component following summer sea-ice retreat in 2002. DOC concentrations were correlated with the runoff fraction, with an apparent meteoric water DOC concentration of 174 ± 1 μM. This is lower than the flow-weighted concentrations measured at river mouths of the five largest Arctic rivers (358 to 917 μM), indicating removal of DOC during transport through estuaries, shelves and in the deep basin. Flow-weighted DOC concentrations in the two largest North American arctic rivers, the Yukon (625 μM) and the Mackenzie (358 μM), are lower than in the three largest Eurasian arctic rivers, the Ob (825 μM), the Yenesey (858 μM), and the Lena (917 μM). A fluorometer responding to chromophoric dissolved organic matter (CDOM) was not correlated with DOC concentrations in Pacific-influenced surface waters unlike previous observations in the Atlantic layer. Nutrient distributions, concentrations, and derived ratios suggest the CDOM fluorometer may be responding to the release of chromophoric materials from shelf sediments. Shipboard incubations of undisturbed sediment cores indicate that sediments on the Bering and Chukchi Sea shelves are a net source of DOC to the Arctic Ocean. Received 3 March 2005; accepted 15 September 2005; published 7 December 2005. Keywords: stable oxygen isotopes; Arctic runoff; Arctic Ocean; dissolved organic carbon; Haardt fluoremeter. Index Terms: 0414 Biogeosciences: Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912); 4207 Oceanography: General: Arctic and Antarctic oceanography (9310, 9315); 1806 Hydrology: Chemistry of fresh water; 0744 Cryosphere: Rivers (0483, 1856); 0750 Cryosphere: Sea ice (4540). Read Full Article (file size: 2134787 bytes) Cited by Citation: Cooper, L. W., R. Benner, J. W. McClelland, B. J. Peterson, R. M. Holmes, P. A. Raymond, D. A. Hansell, J. M. Grebmeier, and L. A. Codispoti (2005), Linkages among runoff, dissolved organic carbon, and the stable oxygen isotope composition of seawater and other water mass indicators in the Arctic Ocean, J. Geophys. Res., 110, G02013, doi:10.1029/2005JG000031. Copyright 2005 by the American Geophysical Union.

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