Spatial heterogeneity of sedimentary organic carbon accumulation and degradation along the Arctic continental margins
Description
The warming climate has led to the translocation of a large amount of terrestrial organic carbon (TerrOC) from permafrost into the Arctic Ocean through river transport and coastal erosion. The fate of sedimentary organic carbon (SOC) varies dramatically and thus affects climate-carbon feedback. We analyzed the spatial heterogeneity of SOC sources and degradation along the East Siberian Arctic Shelf (ESAS) with bulk parameters (total organic carbon, δ13C) and a biomarker (lignin) for comparison of the spatial heterogeneity of TerrOC degradation between the broad ESAS and the narrow Amerasian continental shelf. The results show that the relative importance of river runoff, coastal erosion, and primary productivity causes alongshore variations in organic carbon (OC) sources within the ESAS, highlighting the effects of land-based inputs and ocean currents. Meanwhile, the variations of OC sources show gradually diminishing terrestrial signals in the seaward direction. The simultaneous offshore decrease in OC loadings and increase in lignin degradation indicate that the degradation of TerrOC within a water depth of 100 m is a key mechanism driving the cross-shelf loss of OC in the ESAS. Compared to the broad ESAS, the inconspicuous variations in Λ8/SSA and 3,5-Bd/V across the narrow Amerasian margin suggest that the width of the continental shelf is vital in determining the fate of TerrOC, despite greater levels of recalcitrant petrogenic OC in the Beaufort Sea. In general, the insights have profound implications for evaluating the coastal remobilization and preservation of SOC and its climate-carbon feedback across diverse pan-Arctic continental shelves.