February 27, 2012

Tunsbergdalsbreen Glacier Retreat, Norway

Posted by Mauri Pelto

The Norwegian Water Resources and Energy Directorate (NVE) has an excellent glacier monitoring program. Of these ten drain the largest ice cap in Norway the Jostedalsbreen, from 2008-2013 the net change was retreat on all 11. The largest outlet glacier Tunsbergdalsbreen is not one of the closely monitored glaciers. This glacier flows southeast from the icecap, is 18 km long and terminates at 670 meters in a new proglacial lake.

Examination of Tunsbergdalsbreen in Landsat imagery from 1989, 2003, 2011 and 2014. The violet arrows indicate the terminus. In 1989 no lake is evident. By 2003 the lake has begun to develop and has icebergs in it. In 2011 the lake is 400 meters across and has numerous icebergs in it. In 2014 the lake has expanded to a length of 700 m. The glacier is fed by several tributaries coming off the ice cap. At the #3 green arrow, bedrock is by 2010 in the midst of an icefall from the upper ice sheet that was underneath the glacier in 1989 and 2003. At green arrows #1 and #2 the area of bedrock exposure is expanding, indicating thinner and less ice draining from the ice cap into the tongue of the Tunsbergdalsbreen. In 2003, 2011 and 2014 the snowline is at 1450 m, too high to sustain the glacier, the negative mass balance will drive further retreat.

1989 Landsat image

2003 Landsat image

2011 Landsat image
tunsbergdalsbreen 2014
2014 Landsat image

A closeup of the terminus from Google Earth indicates a number of debris covered ice bergs in the lake. This combined with the observed thinning upglacier indicates that retreat will continue. Exposure of bedrock upglacier occurs because of thinning, which only occurs because of mass balance loss which also results in velocity and discharge reductions.

At present the Tunsbergdalsbreen is the focus of an ongoing field  project that aims to monitor the glacier on an annual basis documenting the impact of climate change. This project is focussing on monitoring the elevation of the glacier surface, the ice velocity and the front position. Video of the project are also worth examining.  In two of these images below, the red arrows in each indicate the thin relatively uncrevassed lower reach.  The low slope suggests the lake basin will continue to expand as this area is lost.  These are 2013 images and in fact some of this retreat has occurred.  Upglacier of the red arrows there is limited crevassing but the slope does increase.
In 2010 -2014 glacier mass balances across Norway were negative. The nearby Sporteggbreen Glacier is experiencing signficant area and volume loss.

2012 Google Earth Image.

tunsberg panorama
tunsberg terminus 2013

Images above from Pål Gran Kielland at the Norsk Bremuseum, a partner in the Tunsbergdalsbreen Project.