Distribution of dissolved organic carbon in the central Arctic Ocean: the influence of physical and biological properties

Detailed analysis of dissolved organic carbon (DOC) distribution in the central Arctic Ocean revealed that a characteristic mean DOC concentration could be assigned to each water mass: surface layer (78 muM; ranging from 43 to 225 muM), halocline (77; 44-200 muM), Atlantic water (59; 41-126 muM) and deep water (53; 29-112 muM). The deep water DOC values were highest in the Makarov Basin with 56 muM, decreasing to 54 muM in the Amundsen Basin and to 50 muM in the Nansen Basin. Different types of DOC versus depth profiles are described. The "surface maximum" profile type normally occurred in open water with a strongly stratified water column. Straight DOC profiles dominated under a closed ice cover and a mixed water column. No direct correlation of the individual DOC concentrations in the surface layer with biological and oceanographic parameters was found. Only at stations with open water and with a stratified water column were DOC concentrations coupled to primary production as indicated by chlorophyll a (chl a) and were significantly influenced by salinity, i.e., the freshwater signal from the Siberian Rivers. An unexpected DOC decrease towards the seafloor across the Lomonosov Ridge is discussed. (C) 2000 Elsevier Science B.V. All rights reserved.