Organic carbon flux and remineralization in surface sediments from the northern North Atlantic derived from pore-water oxygen microprofiles

Organic carbon fluxes through the sediment/water interface in the high-lati tude North Atlantic were calculated from oxygen microprofiles. A wire-opera ted in situ oxygen bottom profiler was deployed, and oxygen profiles were a lso measured onboard (ex situ). Diffusive oxygen fluxes, obtained by fittin g exponential functions to the oxygen profiles, were translated into organi c carbon fluxes and organic carbon degradation rates. The mean C-org input to the abyssal plain sediments of the Norwegian and Greenland Seas was foun d to be 1.9 mg C m(-2) d(-1). Typical values at the seasonally ice-covered East Greenland continental margin are between 1.3 and 10.9 mg C m(-2) d(-1) (mean 3.7 mg C m(-2) d(-1)), whereas fluxes on the East Greenland shelf ar e considerably higher, 9.1-22.5 mg C m(-2) d(-1). On the Norwegian continen tal slope C-org fluxes of 3.3-13.9 mg C m(-2) d(-1) (mean 6.5 mg C m(-2) d( -1)) were found. Fluxes are considerably higher here compared to stations o n the East Greenland slope at similar water depths. By repeated occupation of three sites off southern Norway in 1997 the temporal variability of diff usive O-2 fluxes was found to be quite low. The seasonal signal of primary and export production from the upper water column appears to be strongly da mped at the seafloor. Degradation rates of 0.004-1.1 mg Gcm(-3) a(-1) at th e sediment surface were calculated from the oxygen profiles. First-order de gradation constants, obtained from C-org degradation rates and sediment org anic carbon content, are in the range 0.03-0.6 a(-1). Thus, the correspondi ng mean lifetime of organic carbon lies between 1.7 and 33.2 years, which a lso suggests that seasonal variations in C-org flux are small. The data pre sented here characterize the Norwegian and Greenland Seas as oligotrophic a nd relatively low organic carbon deep-sea environments, (C) 2000 Elsevier S cience Ltd. All rights reserved.