STABLE CARBON ISOTOPES IN SEDIMENTS OF THE EAST-SIBERIAN SEA

Abstract

The Arctic Ocean accounts for 20% of the world`s continental shelves. The amount of terrestrial organic carbon stored in the wide circum-Arctic shelf and slope areas is certainly of importance for calculation of organic carbon budgets on a global scale [Aagaard et el., 1999 ; Codispoti et al., 1990 ; Gobeil et al., 2001 ; Macdonald et al., 1998]. Greater than 90% of all organic carbon burial occurs in sediment deposition on deltas, continental shelves, and upper continental slopes [Hedges et al., 1999], and the significant portion of organic carbon withdraw occurs over the Siberian shelf [Bauch et al., 2000, Fahl and Stein, 1999]. The Arctic coastal zone plays a significant role in the regional budget of carbon transport, accumulation, transformation, and seaward export. Hydro-chemical anomalies obtained over the shallow Siberian shelves demonstrate significant role of coastal erosion in the formation of the biogeochemical regime in the Arctic seas (Semiletov, 1999 ; Dudarev et al., 2001) that could effect a hydro-chemical regime of the surface and halocline waters over the Arctic Basin. Determining the magnitude of particulate and dissolved fluxes of old organic carbon and other terrestrial material from land is critical to constraining a range of issues in the Arctic shelf-basin system, including carbon cycling, the health of the ecosystem, and interpretation of sediment records. Most of the eroded terrestrial organic matter accumulates in coastal zones ; however, significant amounts of this material are transported further offshore by different processes, such as sea-ice, ocean currents, and turbidity currents. The role of the coastal zone in transport and fate of terrestrial organic carbon has not been discussed sufficiently. In this report we present a new data about the distribution of the organic carbon (C-13) and nitrogen (N-15) isotope ratios, OC/N, mineralogy and size distribution of the surface sediment in the most unexplored area of the Arctic Ocean ; the East-Siberian Sea.