T20 Measuring and Modeling the Water Cycle in Cold Regions

Monday, 26 October 2020
1:30 PM - 5:30 PM
Meeting Rooms

WHAT CAUSES INCREASES IN BASEFLOW ACROSS NORTHERN EURASIAN CATCHMENTS UNDERLAIN BY PERMAFROST?

Paper number: T20-9
Program: Technical Sessions
Time: 3:30 PM – 3:45 PM

Authors

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 stream discharge during low-flow periods. In these cold regions, permafrost thaw is postulated to increase low-flow discharge, or baseflow, through either: (a) localized increases in groundwater storage and discharge to streams due to increased aquifer transmissivity from thickening of the freeze-thaw layer above permafrost known as the active layer, or (b) long-term increases in regional groundwater circulation via enhancement of groundwater-surface water interactions due to extensive permafrost loss over decades. While increasing baseflow has been observed throughout northern Eurasia, the precise mechanistic causes remain elusive. Here, we di­fferentiate between where these two subsurface physical mechanisms of baseflow increase are occurring by performing a baseflow recession analysis using daily streamflow records from 1913-2003 for 139 stations in northern Eurasia underlain by varying permafrost areal extents. Results indicate that from 1913 to 2003, the majority of catchments underlain by continuous permafrost have an increasing trend in their recession flow intercepts, a proxy for increasing active layer thickness. Alternatively, the majority of catchments underlain by permafrost types that are less spatially extensive (e.g., discontinuous, sporadic, isolated, or no permafrost) have decreasing trends in their recession flow intercepts, indicating that a potential increase in active layer thickness is not the driving factor of baseflow variations in these catchments. This may indicate that in catchments underlain by continuous permafrost, active layer thickening correlates with increases in baseflow whereas, in other catchments with less extensive permafrost, increases in baseflow may be caused by wholesale permafrost loss and vertical talik expansion that enhances regional groundwater circulation. The results of this work may inform our understanding of the subsurface mechanisms responsible for the changing Arctic hydrologic cycle.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-352989

© Copyright 2020 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.