Permafrost soils have accumulated vast stores of organic carbon recently estimated to be ~1600 Pg C (Tarnocai et al., 2009). During the next century, near-surface permafrost across the circumpolar Arctic is expected to degrade significantly due to global warming. Large amounts of organic matter, particulate (POM) and dissolved (DOM), will be released, transported to the oceans and either mineralized or convected down to the deep Arctic Ocean. Another severe impact of global warming on the Siberian coasts is the coastal erosion in the permafrost regions. The sediment discharge from the coast is as high or even higher than the riverine one transporting huge amounts of organic carbon into the coastal regions. The coastline in the Lena delta, for example, retreated at a mean rate of 0.5 m per year during the last decades (Lantuit et al., 2011). All involved processes are characterized by high spatial and temporal variability but in their entirety they are likely to have critical implications for primary production and carbon cycling on the Arctic shelves and in the Arctic Ocean. The discharge of dissolved organic carbon (DOC) is clearly higher than that of the particulate fraction (POC). DOC in the Lena River has quite similar concentrations over long distances with a high carbon to nitrogen ratio. The classical relation between DOC and salinity in the coastal regions implies a conservative mixing, however, a strong modification of DOM must occur during the transition from freshwater to seawater as, for example, the carbon to nitrogen ratio strongly decreases in the estuarine and near shore regions. Samples from the Lena delta have very different characteristics and highly variable DOC concentrations that are in the range from 450 to 650 µM for river water, 800 to 10,800 µM for ice complex meltwater and of about 800 µM for the ice of ice complexes. Ultra high resolution mass spectrometry is used to identify markers to trace the fate of organic matter from the rivers and coasts into the deep Arctic Ocean. References Tarnocai, C., Canadell, J.G., Schuur, E.A.G., Kuhry, P., Mazhitova, G., and Zimov, S. 2009. Soil organic carbon pools in the northern circumpolar permafrost region. Global Biogeochemical Cycles 23, GB2023. Lantuit, H., Atkinson, D., Overduin, P.P., Grigoriev, M., Rachold, V., Grosse, G., and Hubberten, H.-W. 2011. Coastal erosion dynamics on the permafrost-dominated Bykovsky Peninsula, north Siberia, 1951-2006. Polar Research 30:7341.