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Zusammenfassung:
In the permafrost domain, hydrological processes are expected to be altered by warming-induced permafrost degradation, mainly through changing the connections between surface and subsurface systems. However, due to the lack of groundwater observations in the permafrost domain, key processes that control subsurface dynamics are not well understood. Nevertheless, as a consequence of frozen ground during the cold season, the winter river discharge is only recharged by groundwater and thus can reflect the changes in groundwater dynamics. In this contribution, we investigate the magnitude and timing of the occurrence of miniflow, as well as their relations to the corresponding groundwater dynamics during 1950-2010 in large river catchments (with various permafrost coverages) in southern Siberia. Based on daily discharge records, we found that the lowflow in all the catchments increased during 1950-2010, with the most considerable rise being noticed since 1980. Particularly, in the catchments where discontinuous permafrost prevails, there is a clear shift in the occurrence of miniflow from late winter to early winter. In continuous permafrost catchments, though the miniflow always occurs in late winter, it also exhibits a potential shift of the regime in the miniflow. Given strong correlations between winter flow and climate variables in the warm season, these significant changes in both magnitude and timing of low flow could be triggered by the degrading permafrost and associated alterations in surface water-groundwater interactions. Overall, our results highlight the potential evolutions in the long-timescale groundwater dynamics over varied temporal and spatial distributions of permafrost under a warming climate.
