March 18, 2013
The Obersulzbach Glacier, is situated in the uppermost part of the Obersulzbach Valley, which feeds the Salzach River system in Austria. The Salzach is fed by many glaciers covering over 100 square kilometers (Koboltschnig and Schoner, 2011). These glaciers melt all summer providing considerable runoff to the numerous hydropower projects along the Salzach, that can produce 260 MW of power. The Verbund Power Plant producing 13 MW is seen below, at blue arrow. The glacier has receded in a narrow bedrock basin since the late 1990’s and a shallow lake, Obersulzbach-Gletschersee, has formed since 1998 (Geilhausen et al, 2012). (Geilhausen et al, 2012) observed that in 2009, the lake had an area of 95,000 m2 with a maximum depth of 42 m. Nick Fisher sent me a map of the glacier prepared by the Austiran Military in the early 1930’s this is compared to the GE image of the glacier from 2000, below. The green arrow indicates the 1930’s terminus extending due east from the nose of a ridge and the blue arrow parallels a prominent ridge somewhat above the terminus. The pink arrow in these images and in the Landsat images further below indicates the 1988 terminus position, the yellow arrow the mid section of a glacier tongue from the west that rejoined the main terminus in 1988, the orange arrow the top of a cliff where the eastern tributary ended in 1988. As Nick has noted: Since 1934,the glacier has retreated about 1.6 km,from a terminus at 1980 m, and the proglacial lake lies just behind where once was a magnificent ice fall known as the Turkische Zeltstadt (Turkish Tent City). The Zeltstadt is now a series of waterfalls. According to my map, in 1934 the ice was at least 150 m deep over the current lake surface,where all the glacier streams united before heading down the ice fall.
The World Glacier Monitoring Service reports indicate the glacier retreated 140 meters from 1991-2000 and 345 m from 2001-2010. Here we examine Landsat imagery from 1988, 1998, 2011 and 2012 to identify the retreat of this glacier and formation of the new lake. The pink arrow in each image indicates the 1988 terminus position, the yellow arrow the mid section of a glacier tongue from the west that rejoined the main terminus in 1988, and the orange arrow the top of a cliff where the eastern tributary ended in 1988. By 1998 a small lake less than 100 m long has formed at the end of the glacier. By 2011 and 2012 the lake has grown to a length of 450 m and a with of over 200 meters. The main terminus has retreated 450 to 500 m in the last 25 years. The western tongue at the yellow arrow no longer connects to the main terminus in 1998. By 2011 and 2012 the western tongue is separated by 600 meters from the main terminus. The eastern tongue has retreated 400 m from the cliff by 2012.
A closeup view of the terminus in 2003 from Google Earth indicates the lake development in three small locations around the terminus at the blue arrows. This glaciers retreat fits the pattern of other glaciers in the Austrian Alps, Oberaar Glacier, Rotmoosferner and Ochsentaler.