ABSTRACT
Human-induced climate change is now a worldwide phenomenon. Warming impacts the hydrological system directly by changes in precipitation, but in addition by decreasing snow cover, changing vegetation, and by glacial and permafrost thaw. We may even need to rethink our simplifications for sediment transport as conveniently ‘temperature-independent’ parameters? The Arctic region experiences most rapid climate change and thus is an evident target for enhancing understanding of river dynamics in a world with an altered thermal state.Observational records show Arctic river discharge has increased and the timing of floods have changed. We developed a coupled model of river temperature and permafrost thermal regime to investigate the impact of changing river dynamics on floodplain permafrost. Our numerical modeling for the last 30 years of the Kuparuk River in Northernmost Alaska shows that water temperature can now reach well above 15°C. This delivered heat efficiently is transferred into the channel belt and floodplain and creates ‘thaw bulbs’ under the river valley. Our model experiments show that both increasing discharge and earlier arrival of the spring flood enhance permafrost degradation in the floodplain.Our experiments suggest that in these river systems sediment transport is enhanced. Whereas sediment transport was previously inhibited by frozen substrate, and infinitely high shear stress for part of the season, now sees increased mobility of the river bed. In addition, river banks consisting of degraded permafrost contribute larger fluxes by bank collapse. These results suggest that not only the hydrological cycle has undergone an acceleration, but indeed the sediment transport system is being impacted too.
