The most important mechanism in the earth system that could move significant quantities of green house gases into the atmosphere within this century is thawing permafrost. The potential for carbon release from thawing permafrost to affect global-climate links is realized from the sheer magnitude of the permafrost pools (~2,800 Pg-C) relative to the atmospheric carbon pools (~760 Pg-C). Recent results from the host research group in Arctic rivers suggest that the organic carbon (OC) released from permafrost may be extensively degraded and converted to green house gases (GHG) in the shelf area, but the fate of the releasing old OC in the Arctic shelf and the possible microbial degradation is still unknown.During this research project the applicant proposes to address this critical knowledge gap by analyzing the composition of multiple-proxies, like lipid biomarkers, lignin phenols and CSRA and CSIA analyses of organic carbon in many environmental compartments (sediment, SPM and water samples) from two different oceanographic campaigns in the understudied East Siberian Arctic Shelf (ESAS). CSRA measurements will represent an innovative and powerful approach for determining sources and sink dynamics of OC in the ESAS. This project also proposes the first CSRA-PLFA study in sediments from the Arctic Ocean in order to assess whether microbes are degrading the thawing permafrost. Moreover, CSRA of GHG in the ESAS seawater will determine unequivocal data of the outagassing GHG fluxes.