Advance-retreat of outlet glaciers in Sermilik fjord, Southeast Greenland over the past three decades: Changes in seasonality and co-variability

Victoria Miles
Nansen Environmental and Remote Sensing Center
Seminar Date: 
19. April 2012 - 12:30 - 13:00
Lecture room, Ground Floor, NERSC

Greenland’s marine-terminating outlet glaciers have been recently found to vary more rapidly than previously believed, possibly in response to atmospheric and/or oceanic forcing. For most outlet glaciers, the range of variability and degree of co-variability between them is poorly known and there are currently few observations of long-term variability of glacier calving dynamics at high temporal resolution.
Here we investigate seasonal-to-interdecadal variability and co-variability of calving-front positions for the three outlet marine-terminating glaciers in the Sermilik fjord: Helheim, Fenris and Midgård. We have produced continuous, high temporal resolution sequences of satellite images from a series of satellite sensor systems, including Landsat, SPOT, and synthetic aperture radar (SAR) data from ERS-1 and ERS-2 over a 30+-yr period, which is an unprecedented record with high temporal sampling. We find not only a negative long-term trend (i.e., retreat), but also changes in the magnitude of the seasonal cycle of advance-retreat, as well changes in the covaraibility in the seasonal-to-interannual pattern of ice-front variation between these three glaciers during the 1980–2002 period. Previously, it was believed that the magnitude of these glaciers’ seasonal fluctuation of the front position before 1999 was modest, but we find that the fluctuations were substantial: up to 5 km in 1980s and 2-3 km in the 1990s for Helheim glacier, 2 km for Fenris glacier and 2–3 km for Midgård glacier. In general, co-variability in the glacier’s advance-retreat behaviour is evident; however, in the most recent years, there are differences including diverging trends, with Midgård glacier retreating faster than the others. We are presently investigating the cause of these fluctuations.