Cryospheric and Polar Processes Seminar

Uh-Oh. Abrupt Collapse of an Arctic Ice Cap

by Dr. Michael Willis - Assistant Professor of Geodesy and Remote Sensing, CIRES and Department of Geological Sciences

Cold-based and polythermal ice caps that flow by internal deformation are predicted to evolve slowly in response to changes in climate. Past work suggests that such ice caps in the Russian High Arctic (RHA) are small contributors to sea level at present, even though the region is warming rapidly. Over the coming decades, ice mass loss from the RHA is expected to accelerate based on ensemble models. Our works  highlights unprecedented behavior and rapidly evolving dynamics at one ice cap in the central RHA that may provide an indication that this transition is capable of happening sooner than expected. Satellite radar remote sensing from 1996 indicates that the western margin of Vavilov Ice Cap (area 1,820 km2; location 79.3ºN, 94.4ºE) on October Revolution Island, Severnaya Zemlya, flowed westwards at an average rate of 20 m/year, a speed maintained through 2012; however, by the spring of 2016 glacier sliding speeds surpassed 9,000 m/year. The greatest acceleration in speed occurred while the ice front advanced ~2 km over weak marine sediments and developed a floating terminus. The terminus advance is driven by long-term changes in precipitation patterns amplified by a change in basal conditions at the ice front. The newly-activated outlet glacier is transferring mass rapidly from an area grounded above sea level, deep in the interior of the ice cap, causing thinning rates there of more than 0.30 m/day in 2016. This extraordinary event shows that slowly deforming glaciers, with a frozen bed and no known previous history of fast flow, can initiate surge-like behavior if changes in the pattern of precipitation or other climate factors allow them to advance over weak marine sediments. This raises questions about the overall long-term stability of cold, polar ice caps, many of which terminate in marine waters, in a warmer/wetter Arctic climate with less sea ice.