Arctic rivers and runoff from the land pour vast volumes of freshwater into the Arctic Ocean, influencing seawater salinity, sea-ice formation and ocean circulation, thereby playing an important role in regulating Earth’s heat balance.

As northern monitoring networks decline, scientists have turned to satellite data to reconstruct two decades of river discharge and runoff, revealing a striking mosaic of regional change as warming temperatures and shifting precipitation patterns reshape the Arctic’s hydrological system in uneven and unexpected ways.