Kinematics of the Unprecedently-Short Surge Cycles of Turner Glacier, St. Elias Mountains, Alaska, from 1984 to 2017

Surge-type glaciers exhibit a short active phase of rapid ice velocity followed by a much longer quiescent phase of stagnant flow that typically lasts years to centuries. Here we focus on surge events of Turner Glacier (St. Elias Mountains, Alaska) from 1984 to 2017 using the Landsat archive. Five previously unexamined surge events were identified by variations in velocity measurements produced by offset tracking and terminus delineation of Landsat images. Surge events occurred in 1985-1986, 1991-1993, 1999-2002, 2006-2008, and 2011-2013. These observations indicate that Turner Glacier has a ~5-year surge repeat interval and an active phase length of one to two years. Compared to the typical ~15-year repeat interval of Alaskan glaciers, this is the fastest documented surge repeat interval in Alaska and possibly the world. Although the elevation record for Turner Glacier is more limited than our terminus and speed change data-sets, ASTER digital elevation models from the 2006-2007 and 2011-2013 surge events show mass build up in the reservoir zone preceding the surge with mass redistribution to the terminus as a result of the surge. The reservoir zone experienced surface elevation increase of 50 meters preceding the 2005-2008 surge event. As a result of the surge event, the reservoir zone subsided 100 meters and the receiving zone rose 75 meters. he short repeat interval of Turner Glacier provides a unique opportunity to study the internal ice-instabilities controlling surge kinematics at a higher temporal resolution than ever before. These insights into internal ice-instabilities provide a valuable proxy to the internal instabilities of the major ice streams of Greenland and Antarctica, which are crucial to understand for future sea-level projections.