Observing Two Key Mechanisms of Widespread Permafrost Degradation across Alaska and Northern Canada

Louise M. Farquharson
Postdoctoral Researcher, Geophysical Institute Permafrost Laboratory, University of Alaska

"Permafrost temperatures across the sub-Arctic and Arctic are warming, in some regions at as much as ~1ºC per decade. Long-term monitoring at sites across Alaska and northern Canada highlight two key mechanisms of permafrost degradation: thermokarst development and talik development. A comparison between the Canadian High-Arctic (~80ºN) and the Interior of Alaska (~60ºN) show that the geomorphological impact of permafrost degradation varies primarily due to differences in summer and winter heat flux, ecosystem conditions, and ground ice distribution. At three High-Arctic monitoring sites in the Canadian Archipelago, mean annual ground temperature at 1m depth is ~-13ºC. At these sites, ground ice lies close to the surface and there is limited ecosystem protection. Between 2003 and 2016 we observed thawing degree days up to 240% above historical normals. This caused an increase in depth of thaw, ground ice melt, and up to 90cm of subsidence. In the sub-Arctic, on both the Seward Peninsula and in Interior Alaska, we have observed the initial stages of talik development at over 20 monitoring sites spanning over 1000 km. These sites are characterized by very warm permafrost where the mean annual ground temperature ranges from -1ºC and -0.3ºC. At these sites, an increase in depth of thaw combined with heavy winter snow fall has, in some years, led to incomplete freeze up and the intermittent formation of a talik. It is important to note that despite our observations being associated with specific locations, both mechanisms described can occur across a range of environmental settings as well as at similar latitudes. The two processes we observe have drastically different implications for infrastructure and the natural environment."

Date: 12:00 PM ET, Tuesday, September 3, 2019

Where: USGS National Center, Reston VA, Room 3C129

GS Talk: https://gstalk.usgs.gov/755736

Phone: 703-648-4848 Code:755736