December 20, 2016
Has Fridtjovbreen, Svalbard Surged for the last time?
Posted by Mauri Pelto
Fidtjovbreen, Svalbard comparison in 1998 and 2016 Landsat imagery. Red arrow marks the 1998 terminus, yellow arrow the 2016 terminus and purple dots mark the snowline. The Yellow numbers indicate area of separation between glaciers. Pink arrows indicate areas on the upper glacier where thinning is exposing more bedrock. F=Fridtjovbreen, S=Sagabreen, G=Gronfjordbreen
Fridtjovbreen, Svalbard, is a tidewater-terminating glacier that started a 7-year surge advance during the 1990’s. This central Spitsbergen glacier drains into Van Mijenfjorden and is currently 13.5 km long. The glacier advanced ~2.8 km during a surge in the 1990’s at a maximum rate of ~4 m per day (Murray et al, 2003). Murray et al (2012) observed that from 1969 to 1990, the glacier retreated ~500 m and lost 5% of its volume. During this interval the glacier thinned up to 60 m in the lower elevations while thickening up to 20 m in its higher elevations. The upper part of the glacier is considered the reservoir zone, which after sufficient thickening and slope increase versus lower glacier glacier, receiving zone, surges yielding an increased flux into the receiving zone. If the reservoir zone is not an accumulation zone due to climate change, than the surge mechanism in this case is lost. Murray et al (2012) observed that the reservoir zone thinned by up to ~120 m and the receiving zone thickened by ~140 m during the most recent surge. Lonne et al (2014) examined glacial surges in Svalbard noting they are protracted and characterized by individual dynamic evolution. Fridtjovbreen provides a well documented example of a 12 year (1991–2002) surge. that Lonne et al (2014) report relocated 5 km2 of ice into the fjord, yet 15 years later leaves little visual evidence behind. The advance led to the overriding of Sagabreen (S) observed by Glasser et al (1998).
The most recent surge occurred in a climate of decreasing overall ice volume, but in an environment of accumulation zone thickening on Fridtjovbreen (Lonne et al 2014). Here we examine Landsat imagery that illustrates both retreat from 1998 to 2016 and that instead of thickening during the quiescent phase, high snow lines have led to thinning even at the head of the glacier. From 1998 to 2016 the glacier has retreated 2.2 km. This had led to separation from Sagabreen (1) from Fridtjovbreen. Thinning at higher elevations had led to bedrock expansion at each pink arrow in the comparison of 1998 and 2016, as well as the 2000 to 2015 imagery below. In each of the four years the snowline has risen to above 500 m by the end of the melt season. In 2016 the image is from the end of July, by early September the snowline had risen well above 500 m. There is also separation of glaciers adjacent to Gronfjordbreen at an elevation of 300 m, at Point 2 and 3. This implies that the reservoir zone is losing mass and cannot initiate a future surge. The thinning, retreat and volume loss parallels that of other glaciers in the area, that are not surging Frostisen and Paierbreen. Lonne et al (2014) note that although the surge mechanism itself is unrelated to climate, climatic conditions play a major role in the course of a surge. I would add that climate can eliminate the potential for a surge if the reservoir region is no longer an area of accumulation, without which there will not be thickening.
Fridtjovbreen, Svalbard comparison in 2002 and 2015 Landsat imagery. Yellow arrow the 2016 terminus and purple dots the snowline. Purple dots indicate the snowline and Pink arrows indicate areas on the upper glacier where thinning is exposing more bedrock.