Carbon utilization in the Eurasian sector of the Arctic Ocean

Production and remineralization of carbon in the Eurasian sector have been estimated based on a combined data set of the Oden-91 and Polarstern-93 (AR K IX-4) expeditions. This sector includes the deep Nansen and Amundsen Basi ns and their linked shelf seas, i.e., the Barents, Kara, and Laptev Seas. T he water masses in this region are composed of Atlantic water, river runoff , and sea ice-melt water. The fractionation between these source waters is elucidated from the delta(18)O-salinity relation and conservation of mass. By combining preformed nitrate concentrations of the source waters with the fractionation model and the measured nitrate concentrations, nitrate defic its and excesses are calculated. These concentrations are then converted to carbon equivalents by applying a C/N ratio, whereby a measure of apparent carbon utilization (ACU) is obtained. From the relative inventory of ACU al ong the slope and deep basin sections, we conclude that the shelf areas are the dominant productivity sites and that the productivity signal is transp orted to all water masses in the Eurasian Basin. The flux of utilized carbo n from the Barents-Kara and Laptev Seas is about 0.022 Gton C yr(-1).