Arctic Greening Thaws Permafrost, Boosts Groundwater Flow
Models are used to understand how low-Arctic landscapes are changing in a warming climate.
Models of permafrost dynamics were used to show that snow drifts associated with tall shrub patches warm the underlying soil, resulting in holes called “through taliks” in the permafrost. Through taliks can activate deep flow pathways that significantly alter groundwater flow patterns in shrub-tundra landscapes.
The resulting increases in groundwater discharge suggest that observed increases in tall shrub abundance throughout the Arctic may be a driver of observed increases in winter Arctic river discharge.
At hilly field sites in the southern Seward Peninsula, Alaska, patches of deep snow in tall shrubs are associated with higher winter ground temperatures. Reseachers from the Next-Generation Ecosystem Experiments (NGEE)–Arctic study show that through taliks—thawed zones extending through the entire permafrost layer—can form under these patches. The formation of through taliks creates new hydrologic pathways connecting the near surface to deeper regions, with significant hydrological and biogeochemical consequences. In particular, through taliks enable exchange and transport of nutrients and soil carbon from shallow upland hillslope sources to streams and lakes through groundwater discharge. To better understand the processes controlling and consequences of through taliks, researchers used NGEE–Arctic’s permafrost hydrology model, Arctic Terrestrial Simulator (ATS), to simulate through taliks associated with snow drifts. Scenarios were developed based on an intensively studied hillslope transect on the southern Seward Peninsula. In these scenarios, when through taliks formed, subpermafrost groundwater flow greatly increased. The simulations showed that through talik can form quickly (over a few decades) and then drive a rapid increase in subpermafrost groundwater.
Los Alamos National Laboratory
Oak Ridge National Laboratory
This work is part of the Next-Generation Ecosystem Experiments (NGEE)–Arctic project, which is supported by the Office of Biological and Environmental Research within the U.S. Department of Energy (DOE) Office of Science.
Jafarov, E.E., E.T. Coon, D.R. Harp, C.J. Wilson, S.L. Painter, A.L. Atchley, & V.E. Romanovsky. “Modeling the role of preferential snow accumulation in through talik development and hillslope groundwater flow in a transitional permafrost landscape.” Environmental Research Letters 13(10), 105006 (2018). DOI:10.1088/1748-9326/aadd30