The Arctic Oscillation controls interannual transport and fate of particulate organic carbon on the Eurasian Arctic Shelf

• River plume paths affect riverine particulate organic carbon (POC) transport. • Interannual spatial heterogeneity in significant δ 13 C depletion of POC is observed. • δ 13 C depletion could be associated with the selective dispersal of aquatic POC. • The Arctic Oscillation modulates interannual POC transport dynamics on the shelf. Carbon export through the Arctic rivers could significantly impact land–ocean interactions and coastal ecosystems under global warming. However, the transport dynamics and coastal fate of these carbon associated with large river plumes on the adjacent shelves remain largely unknown, particularly under large-scale climate patterns like the Arctic Oscillation (AO). In this study, we analyzed the interannual variation of particulate organic carbon (POC) and hydrological properties on the Eurasian Arctic Shelf (EAS) during summer to examine the influence of AO on the coastal dispersal of POC in the EAS. Our results revealed interannual spatial heterogeneity in highly depleted δ 13 C POC values in the Laptev Sea under varying atmospheric conditions. This significant depletion of δ 13 C POC could be attributed to the selective dispersal of aquatic biomass POC, coupled with rapid settlement of mineral-rich POC, as indicated by the relationship between δ 13 C POC and salinity within the Lena plume. Therefore, variations in the pathways of river plumes, driven by atmospheric forcing under the annual AO regime, could not only affect the hydrological regime of the Laptev Sea but also modulate the dispersal and dynamics of POC in the EAS. Our findings are crucial for understanding the biogeochemical behavior of terrigenous POC and its impact on the future carbon cycle and coastal ecosystem in the Arctic margins, particularly in the context of recent warming and a positive trend of AO.