Publication Abstract

Ocean regulation of glacier dynamics in south-east Greenland and implication for ice sheet mass changes

Ocean regulation of glacier dynamics in south-east Greenland and implication for ice sheet mass changes

T. Murray, K. Scharrer,  T. D. James, S. Dye*, E. Hanna, A. Booth, N. Selmes, A. J. Luckman,  A. L. Hughes, S. Cook, P. Huybrechts

Synchronous acceleration and thinning of south-east (SE) Greenland glaciers during the early 2000s was the main contributor in causing the annual mass loss from the ice sheet to double. During the period 2003-2005, SE Greenland’s outlet glaciers were dramatically thinning, accelerating, and retreating. Then, in 2006, two of the largest outlet glaciers in the sector, Helheim and Kangerdlugssuaq, were reported to have simultaneously slowed down, ceased thinning, and re-advanced, and there was indication that other glaciers in the region followed suit. In order to examine the extent of the dynamic changes and to identify their cause we used satellite and airborne data to measure changes in glacier surface elevation, calving front positions and flow speeds for a large number of tidewater terminating outlets throughout SE Greenland. We concentrate on the region with the highest rates of mass deficit and our data cover the period during and after the cessation of fast flow and thinning at Helheim and Kangerdlugssuaq. We show that the acceleration of these glaciers was followed by a synchronized and widespread slowdown, in many cases associated with a decrease in thinning rates and re-advance of the glaciers’ front margins. We propose that ice sheet-ocean interactions are the first-order regional control on these recent mass changes. Sea surface temperature and mooring data show that the preceding dynamic thinning coincided with a brief decline in the cold East Greenland Coastal Current, probably partly induced by a reduction in ice-sheet runoff. This decline allowed warm water from the Irminger Current to reach the SE Greenland coast. A re-strengthening of the cold waters of the East Greenland Coastal Current coincides with their subsequent slowdown. We argue that this warming and subsequent cooling of the coastal waters was the cause of the glacier’s dynamic changes, and further suggest that the re-strengthening of the East Greenland Coastal Current resulted in part from cold water input by increased glacier calving during the speedup and increased ice-sheet runoff. Thus we conclude that the main mechanism for ice sheet mass loss in SE Greenland is highly sensitive to ocean conditions and is likely subject to negative feedback mechanisms.

T. Murray, K. Scharrer, T. D. James, S. Dye*, E. Hanna, A. Booth, N. Selmes, A. J. Luckman, A. L. Hughes, S. Cook, P. Huybrechts

American Geophysical Union, Fall Meeting 2009, abstract #C11A-03