Large sinuous rivers are slowing down in a warming Arctic

Arctic regions are disproportionately affected by atmospheric warming, with cascading effects on multiple surface processes. Atmospheric warming is destabilizing permafrost, which could weaken riverbanks and in turn increase the lateral mobility of their channels. Here, using timelapse analysis of satellite imagery, we show that the lateral migration of large Arctic sinuous rivers has decreased by about 20% over the last half-century, at a mean rate of 3.7‰ per year. Through a comparison with rivers in non-permafrost regions, we hypothesize that the observed migration slowdown is rooted in a series of indirect effects driven by atmospheric warming, such as bank shrubification and decline in overland flow and seepage discharge along channel banks, linked in turn to permafrost thaw. As lower migration rates directly impact the residence timescales of sediment and organic matter in floodplains, these surprising results may lead to important ramifications for watershed-scale carbon budgets and climate feedbacks.