A time series of TanDEM-X DEMs and feature-tracking of Helheim and Kangerdlugssuaq glaciers in south-east Greenland
Bevan, Suzanne; Luckman, Adrian; Murray, Tavi
Swansea University, UNITED KINGDOM
The rate of mass loss from the Greenland ice sheet has accelerated over the past decade, with increases in discharge from tidewater outlet glaciers accounting for a significant proportion of the loss. Helheim and Kangerdlugssuaq are the two largest tidewater glaciers in south-east Greenland. Between 2003 and 2005 they experienced near-synchronous acceleration and retreat, doubling their combined ice discharge to the ocean. Both glaciers have since slowed but remain more retreated and more active than before 2003. It seems likely that these recent rapid changes are controlled by processes acting at or near the calving front. Obtaining observations of glacier geometry and flow velocity at a high spatial and temporal resolution will contribute to a better understanding of exactly how Helheim, Kangerdlugssuaq, and other similar glaciers, respond to calving front processes. Ultimately, this should lead to a better understanding of their probable response to a warming atmosphere and ocean.
Here we use sequences of TanDEM-X acquisitions between June 2011 and November 2012 to generate interferometric digital elevation models (DEMs) and to feature-track surface displacement between image acquisitions for Helheim and Kangerdluugssuaq. The high spatial resolution, day/night, and cloud-penetrating capabilities of the X-band SAR system enable year round production of DEMs and surface velocity fields with a spatial resolution of 2 m, at 11-day intervals.
Time-lapse animations of Helheim DEMs reveal the development of troughs in surface elevation close to the front. The troughs propagate down flow and develop into the rifts from which calving takes place. On both glaciers, regions of high variance in elevation can be identified caused by the transit of crevasses. In addition, on Helheim, a 1 km wide band of high variance adjacent to the calving front may be interpreted as the response to tidal forcing of a partially floating tongue.
The DEMs and surface velocity fields for Helheim will also be used in support of a NERC-funded project that is collecting in-situ measurements from a wireless network of sensors close to the terminus in order to constrain and validate a numerical calving model.