Stability of ice wedges in Alaska's Arctic National Parks, 1951-2019

Abstract

Ice-wedge polygons are a striking and widespread feature of the arctic landscape. Ice wedges are vulnerable to thaw because they are nearly pure ice bodies near the surface, with little insulating overlying material. Ice-wedge polygon monitoring is a part of the permafrost monitoring program for the National Park Services Arctic Inventory and Monitoring Network (ARCN, the five National Park units in northern Alaska). The present report is a re-analysis of ice-wedge condition in three study areas, based on satellite images taken in 2019 and 2020 (sampling episode 3). Results are compared to previous analyses based on aerial photographs from 1950-51 (episode 1) and satellite images from 2006-2009 (episode 2). Significant ice-wedge degradation occurred between sampling episodes 1 and 2 in one of the study areas (in Kobuk Valley National Park, KOVA). Sampling episode 3 revealed relatively minor changes from episode 2 in all three areas. This is somewhat surprising given the record warm temperatures that occurred between sampling episodes 2 and 3. Apparently the recent warming did not cross any thresholds that would trigger immediate and widespread visible changes in ice wedges, or insufficient time has elapsed since the recent onset of warmer temperatures in 2014. However, the effects of previous ice-wedge degradation continued to be manifested in new drainage channels that formed by linkage of pits from previous ice-wedge degradation. The Noatak National Preserve (NOAT) study area was affected by wildfires in 1977 and 2010, and comparison of burned to unburned areas in subsequent sampling episodes failed to show significant new ice-wedge degradation brought about by these fires.