July 10, 2013

Blåmannsisen Outlet Glacier Retreat, northern Norway

Posted by Mauri Pelto

Blåmannsisen is the fifth largest ice cap in Norway, just ahead of Hardanger in the Inventory of Norwegian Glaciers published by NVE in 2012. The ice cap is not tapped for hydropower and has not been the target of much research as a result from the NVE, second image is from NVE report. The ice cap outlet glaciers drain into a number of lakes. The NVE inventory indicates a reduction in area of the ice cap during the 20th century from 124 to 87 square kilometers. There is no change indicated for the 1961 to 1999 period. In the last 20 years retreat has become evident. blamannsisenblamannsisen terminusHere we examine the terminus change of two outlets one on the north side of the ice cap (yellow arrow) and one at the southwest corner (red arrow). For the northern outlet glacier three changes are emphasized. First at the terminus at the arrow point the expansion of the terminus lake from a small pond in 1994, 100 by 100 m, to a lake that is one kilometer long and 100 to 400 m wide in 2011. The progression of the lake development is steady with expansion evident in 1999 and 2006. The second noteworthy item is the ice connection of the outlet glacier to the main ice cap, yellow dots. This connection has narrowed from 1300 m in 1994 to 800 m in 2011. This in particular is apparent above Point A, which in 1994 is a bedrock knob surrounded by the glacier, a small nunatak. In 1999 Point A is still a nunatak. In 2006 the nunatak is just barely surrounded by ice, and in 2011 it is now just the extension of a ridge. The problem with the narrowing connection to the main ice cap, due to thinning ice, is less inflow, which will hasten the retreat. As is evident in 2006 and 2011 this glacier is becoming dynamically separated from the ice cap and has little retained snowcover of its own. Notice that as you cross onto the main ice cap there is no snowcover. This terminus has retreated 150 m on the west side and 400 m on the east side since 1994.

The second terminus is at the red arrow and has retreated from 1994 to 2011 exposing a new bedrock peninsula in the lake at the tip of the red arrow. This bedrock exposure at the tip of the red arrow was surrounded by glacier ice in 1994 and 1999. By 2006 the terminus had pulled back from this area, the bedrock exposure had expanded and ice no longer passed south of it either. By 2011 next to the letter B a small bedrock knob is being exposed at the terminus by continued retreat. The retreat of this outlet has been 500 m on the south side and 200 m on the north side since 1994. This glaciers retreat began later than at another northern Norwegian glacier Engabreen and more slowly and less dramatically than southern Norway glaciers such as Tunsbergdalsbreen, as noted by the annual frontal change studies of NVEblamannsisen 1994
1994 Landsat image
blamannsisen 1999
1999 Landsat image

blamannsisen 2006
2006 Landsat image
blamannsisen 2011
2011 Landsat image