May 11, 2015
The Obersulzbach Glacier, is situated in the uppermost part of the Obersulzbach Valley, which feeds the Salzach River system in Austria. The glacier drains the northeastern flank of Großvenediger. The glacier was the third largest glacier in Austria in the 1980’s, but in the last several decades separated into five distinct sections. Now that it is in five parts, should it be listed as such?
Yes, given that the Austrian Glacier Inventory has reclassified the glacier as five separate glaciers (Fischer et al, 2014). In this post they are numbered 1=Krimmlertorl Kees, 2=Obersulzbach Kees, 3=Bleidacher Kees, 4=Sulzbacher Kees, 5=Venediger Kees.
Nick Fisher sent me a map of the glacier prepared by the Austrian Military in the early 1930’s this is compared to the GE image of the glacier from 2012, below. According to this 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. In 1934 the five branches of the Obersulzbach all joined and continued downglacier past a prominent rib on the east side of the glacier, light blue arrow, to terminate at 1980 meters, green arrow. The two western most glaciers Krimmerlertorl and Obersulzbach on the images, were joined at the pink arrow in 1934 and are well separated in 2012. At the orange arrow in 1934 Bleidacher (3) flowed over a steep cliff and joined the other segments. Today the glacier section ends at the top of a steep cliff. Glacier Sulzbacher and Venediger are the largest and easternmost draining the actual slopes of Großvenediger. They joined the other segments in 1934. By 1988 they had retreated to the red arrow but the two were still joined, by 2012 they had separated at the yellow arrow. Hence, we now have separate glaciers that formerly joined together. The World Glacier Monitoring Service reports indicate this glacier retreated 140 meters from 1991-2000 and 345 m from 2001-2010, a substantial increase. Here we examine Landsat imagery from 1988, 1998, 2012, 2013 and 2014 to identify the retreat andand separation of the glacier into. By 1998 a small lake less than 100 m long has formed at the end of the glacier, blue arrow.
In 1988 there is no lake visible at the end of the main terminus. The glacier has retreated 1.4 km since 1934. At the pink arrow glacier Krimmerlertorl and Obersulzbach are still joined in 1988. Glacier Sulzbacher and Venediger are also still joined at the yellow arrow and terminate at the red arrow. Glacier section Bleidacher has become detached.
By 1998 Krimmerlertorl and Obersulzbach are separated but the eastern glaciers Sulzbacher and Venediger are still joined at the yellow arrow. No lake yet exists at the terminus. Obersulzbach Glacier 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). They observed that in 2009, the lake had an area of 95,000 m2 with a maximum depth of 42 m.
By 2013 all the glacier segments are separate. By 2013 the lake, Obersulzbach-Gletschersee,has grown to a length of 450 m and a with of over 200 meters. The retreat from 1988-2013 of glaciers Krimmerlertorl=0.8 km, Obersulzbach=0.6 km, Bleidacher=1.3 km, Sulzbacher=1.4 km, Venediger=1.6 km. The 2014 image is not as clear, but further retreat did occur. The Austrian Alpine Club 124th annual survey indicated 86% of Austrian glaciers retreated from 2013-2014.
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. Glacier area loss will lead to declines in summer runoff. A mass balance program has been started on Venediger Kees.
Verbund Power Station, blue arrow.