Seasonal freezing increases High Arctic erosion and landscape response to climate extremes

Conventional views suggest Arctic landscapes erode more slowly than temperate ones due to seasonal ground ice increasing sediment cohesion. However, observations of relatively rapid cold region channelisation challenge this paradigm. Using flume experiments, scaling theory and field data, we show that thawing riverbeds erode faster than unfrozen counterparts. Early in the thaw season, surface water injections advect heat and momentum fluxes into the bed, driving convective stirring that localises subsurface thawing and increases bed erosion. Resultant bed and thaw front topographies continue modulating subsurface flow paths, sustaining spatially variable erosion, which generates a stepped surface topography for subsequent thaw seasons. At the landscape scale, this coupled thermal-erosional response results in a characteristic topographic fingerprint composed of discontinuous channel segments interspersed by depositional zones. Our findings suggest that cold region landscapes respond more quickly to a changing climate relative to temperate ones and are sensitive to early season extreme weather events. Cold-region riverbeds erode faster than unfrozen ones as early thaw season water injections enhance subsurface thawing and increase bed erosion, suggesting an increased sensitivity to extreme weather events, according to flume experiments, scaling theory, and field data.