Biomarker and carbon isotope constraints (d13C, d14C) on sources and cycling of particulate organic matter discharged by large Siberian rivers draining permafrost areas

Circumpolar permafrost soils store about half of the global soil organic carbon pool. Currently most of this organic matter remains frozen and therefore does not take part in the active carbon cycle, making permafrost soils a globally important carbon sink. As a result of Arctic climate warming the thaw-induced release of greenhouse gases to the atmosphere possibly creates a positive climate feedback. The great arctic rivers play an important role in global biogeochemical cycles by connecting the large permafrost carbon pool of their hinterlands with the arctic shelf seas and the Arctic Ocean. The first part of this thesis deals with the modern Lena River system using biomarkers to detect and characterize organic matter sources. The second part investigates past permafrost dynamics and the possible permafrost/wetland climate feedback during the last deglaciation and Early Holocene using compound-specific 14C dating of sediments discharged by the Amur River to the Okhotsk Sea.