The Arctic is undergoing accelerated warming and widespread permafrost thaw, processes expected to enhance the export of terrestrial dissolved organic carbon (DOC) to the ocean. Yet whether climate change has altered the magnitude, distribution, and transport pathways of terrestrial DOC across the Arctic Ocean remains poorly constrained by basin-scale observations. Here we combine optical proxies with satellite remote sensing to track the spatiotemporal dynamics of terrestrial DOC across the Arctic since the early 21st century. We find that terrestrial DOC is not confined to river plumes or adjacent shelves, but is redistributed across ocean basins by large-scale circulation. Despite relatively stable riverine DOC fluxes, the terrestrial contribution to surface DOC showed no long-term trend in annual means, yet increased significantly in summer across the Arctic Ocean. Terrestrial DOC variations are amplified at regional scales, with significant enhancement in the Barents and Chukchi Seas. Such changes likely reflect climate oscillation-driven variability in river discharge and Atlantification-induced mixed layer shoaling. Our synoptic constraints suggest that while total terrestrial DOC supply has remained largely unchanged over the past two decades, climate-driven oceanographic processes are substantially reorganizing its spatial patterns.
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