Potential mechanistic causes of increased baseflow across northern Eurasia rivers underlain by permafrost
Abstract
Warming in the Arctic is occurring at twice the rate of the global average, resulting in permafrost thaw and a restructuring of the Arctic hydrologic cycle as indicated by increased river discharge. In these cold regions, warming increases active layer depths, which is postulated to increase groundwater discharge to streams, or baseflow, through either: (a) increases in subsurface transmissivity, if the water table elevation is maintained in the thickening active layer, or (b) long-term increases in regional groundwater circulation due to extensive permafrost loss over decades. While increasing baseflow has been observed throughout northern Eurasia, the mechanistic causes remain elusive.
In this study, we estimate changes in baseflow in concert with changes in active layer thickness by computing minimum stream discharge and performing a baseflow recession analysis using daily streamflow records from 1912-2002 for 139 stations in northern Eurasia underlain by varying permafrost types. Results indicate that there is an increase in baseflow from 1912 to 2002 for the low-flow months of September and October across all permafrost types. However, areas underlain by continuous permafrost have positive recession flow intercepts (a proxy for increasing active layer thickness) while areas underlain by discontinuous, sporadic, isolated, and no permafrost have negative recession flow intercepts, indicating confounding changes in aquifer thicknesses. This may indicate that in regions underlain by continuous permafrost, active layer thickening correlates with increases in baseflow whereas in other permafrost regions, increases in baseflow may be caused by wholesale permafrost loss and enhanced regional groundwater circulation. The results of this work may inform our understanding of the changing Arctic hydrologic cycle which influences terrestrial and aquatic responses to warming temperatures throughout the Arctic.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C13E1365E
- Keywords:
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- 0702 Permafrost;
- CRYOSPHERE;
- 0708 Thermokarst;
- CRYOSPHERE;
- 0768 Thermal regime;
- CRYOSPHERE;
- 0774 Dynamics;
- CRYOSPHERE