Abstract:Organic carbon fluxes through thesediment/water interface in the high-latitude NorthAtlantic have been calculated from oxygenmicroprofiles. A wire-operated in situ oxygen bottomprofiler was deployed, and oxygen profiles were alsomeasured on board (ex situ). Diffusive oxygen fluxes,obtained by fitting exponential functions to the oxygenprofiles, were translated into organic carbon fluxes andorganic carbon degradation rates. The mean Corg inputto the abyssal plain sediments of the Norwegian andGreenland Seas was found to be 1.9 mgCm-2d-1.Typical values at the seasonally ice-covered EastGreenland continental margin lay between 1.3 and 10.9mgCm-2d-1 (mean 3.7 mgCm-2d-1), whereas fluxes onthe East Greenland shelf are considerably higher, with9.1 to 22.5 mgCm-2d-1. On the Norwegian continentalslope Corg fluxes of 3.3 to 13.9 mgCm-2d-1 (mean 6.5mgCm-2d-1) were found. Fluxes are considerably higherhere compared to stations on the East Greenland slopeat similar water depths. By repeatedly occupying threesites off southern Norway in 1997 the temporalvariability of diffusive O2 fluxes was found to be quitelow. The seasonal signal of primary and exportproduction from the upper water column appears to bestrongly dampened at the seafloor. Degradation ratesof 0.004 to 1.1 mgCcm-3a-1 at the sediment surfacewere calculated from oxygen profiles. First-orderdegradation constants, obtained from Corg degradationrates and sediment organic carbon content, are in therange of 0.03 to 0.6 a-1. Thus, the corresponding meanlifetime of organic carbon lies between 1.7 and 33.2years, which also suggests that seasonal variations inCorg flux are small. The data presented herecharacterize the Norwegian and Greenland Seas asoligotrophic and relatively low organic carbon deep-seaenvironments.Keywords: Diffusive oxygen uptake,benthic fluxes, organic carbon, in situ oxygenmicroelectrodes, North Atlantic, high latitudes.
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