Thrym Glacier Retreat, Greenland

Thrym Glacier in southeast Greenland is a marine terminating outlet glacier at the head of Skjoljungen Fjord. This post focuses on Landsat images from 2000, 2004 and 2012. During the last decade several changes of significant are evident at the terminus of the glacier. This glacier was one of the glaciers that was a focus of a recent examination of Greenland glacier marginal change over the last 80 years by Bjork et al (2012) (detailed supplement).Thrym Glacier’s terminus in 2000 was connected with a second glacier flowing from the north, a branch of the Maelkevejen. The first change since 2000 is the opening of a channel between the terminus of the glacier and the fjord wall (green arrow) on the east side of the valley. This removes a pinning point for the glacier that should enable an increase of calving in the greater water depths. At the junction of the two glacier a lake has developed that now is part of the fjord. This water body has expanded to 2.5 km in length and 1.5 in width (yellow arrow). Upglacier of the terminus the glacier is fed by many tributaries, one of these has separated from the glacier in the last decade and is no longer feeding ice into the system, purple arrow.
Landsat image 2000

Landsat image 2004
Landsat image 2012
A close up view of the glacier terminus and new outlet also indicates the drop in water level of the developing lake in 2000 that has now become part of the fjord in 2012, images below. The red arrows indicate the recession of shoreline as the fjord opened and water levels dropped. The actual retreat of the glacier margin ranges from 200-400 meters during the last decade, fairly minor, but the changes will lead to a more dramatic retreat in the near future. John Mercer of Ohio State(1961) was the first to write about the importance of pinning points to stability of a terminus. Brown et al (1982) of the USGS, quantified the strong direct relationship between water depth and calving rate on Alaskan glaciers, Pelto and Warren (1991) noted that this relationship extended with to Greenland glaciers. The current terminus position of Thrym Glacier having just moved into deeper water and fronted now by tidal front along its entire front, is not in a stable position. The glacier will now have to retreat into the narrower valley, to reduce its calving rate. In June of 2013 the opening remains unchanged, indicating no terminus advance during the winter season. Historic photographs of this glacier dating back to World War II indicate the outlet had been closed throughout the latter half of the 20th century. The retreat of this glacier follows the regional pattern observed on Sortebrae Glacier and De Reste Bugt Glacier
Landsat image 2000

Landsat image 2012
thyrm glacier 2013Landsat image 2013

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