Terminus behavior of Helheim and Kangerdlugssuaq Glaciers, southeast Greenland, from 2008-2015

Abstract:

Many marine-terminating outlet glaciers in Greenland retreated, accelerated, and thinned in the early 2000s. Although some of these glaciers, such as Jakobshavn Isbrae, have continued to retreat, others have re-stabilized in a new terminus configuration. This study investigates the terminus behavior of Helheim and Kangerdlugssuaq Glaciers, southeast Greenland, since their terminus positions re-stabilized in 2006, roughly 4 km upstream of their 2001 positions. (Glacier velocities have remained elevated since 2001.) We combine satellite measurements of ice-front position, glacier velocity, and surface elevation from 2008-2015. We find significant variability in terminus position and glacier velocity over this time period, with changes in terminus position of more than 3 km and changes in glacier velocity of more than 3 km/yr at both glaciers. At Kangerdlugssuaq Glacier, glacier velocity and terminus position varied seasonally, with glacier advance and slowdown typically commencing in December/January and glacier retreat and speedup typically commencing in July/August. The seasonal retreat occurred through the calving of large tabular icebergs, likely indicating the disintegration of a seasonal ice tongue similar to that observed at Jakobshavn Isbrae. In contrast, at Helheim Glacier, iceberg calving events and glacier retreat occurred at all times of the year. We interpret differences between the two glaciers in terms of the glacier, bed, and fjord geometry. Our results indicate that these glaciers are very sensitive to changes in the stress balance near their termini.