GEOCHEMICAL CHARACTERISTICS AND BURIAL RECORDS OF ORGANIC CARBON IN THE COLUMN SEDIMENTS FROM WESTERN BERING SEA

Using the two column samples (BL16 and BL10) taken during the Fifth Chinese National Arctic Expedition Cruise at the western Bering Sea, the geochemical characteristics and burial records of total organic carbon (TOC) over the past century were studied. The results show that the depositional regime was rather stable in the study area according to the vertical distribution of ²¹⁰Pb profiles and its relationship to the core depth. Therefore, the sedimentary record of the past seventy years could be established for the two short cores respectively. As in the core BL16, there is a good correlation between TOC and total nitrogen (TN) as well as grain sizes, suggesting a consistent provenance of sedimentary organic components and the control of sediment grain size over the OM burial. On the other hand, the core BL10 from the upper slope was composed of more coarser sediments where exist poor relation between TOC and TN, probably caused by the complex depositional regime, varying OM input and microorganism activity. A clear shift of TOC and CaCO₃ abundance in the upper sections (about twenty years ago) were observed in both two cores, which may indicate the recent regional warming in the arctic area and ocean acidification. The TOC sequestration in the two cores were estimated as 3100 mmol C·m^-2·a^-1 and 1400 mmol C·m^-2·a^-1, respectively. After the examination of the preservation of sedimentary TOC and the regional correlation of TOC sink fluxes, the relatively higher sequestration of TOC in the study area could be constrained by the higher marine productivity, quick POC export from the upper water column, effective metabolic processing and higher sedimentation rates of the seabed.