Warming transforms the western Arctic Ocean into a hub of drifting matter.

The Arctic Ocean is increasingly stressed by anthropogenic pollution and rapid environmental change. River discharge plays a crucial role in this transition by delivering freshwater, nutrients, carbon, and contaminants to the ocean. Yet how river-borne materials will spread through the Arctic under future climate warming remains unclear. Here we show that climate warming accelerates and expands the dispersal of Arctic river waters and drifting materials through multi-scale changes in ocean circulation linked to sea-ice decline and reduced upper-ocean density. Stronger ocean eddy activity and altered wind-driven circulation transform the Beaufort Gyre from a predominantly regional reservoir into a pan-Arctic convergence zone that efficiently accumulates river-derived materials from Siberia. Meanwhile, intensified boundary currents and Transpolar Drift accelerate the export of Siberian discharge toward the North Atlantic. Together, these circulation changes greatly increase cross-basin connectivity, with broad implications for marine ecosystems in the northern high-latitude oceans and for Arctic coastal communities.