Climate change in Austria: Alpine glaciers thousands of years ago smaller than today
By Dr. Sebastian Lüning and Prof. Fritz Vahrenholt
(German text translated/edited by P Gosselin)
In 1998 there were 925 glaciers and large ice masses in Austria with an area of 1 hectare or more, in total 453 square kilometers. Fifty percent of the Austrian glacier area are found in the Ötztal Alps and Venice Alps groups.
All measured glaciers in Austria have significantly lost area and volume in the period since 1980. For example, in the southern Ötztal Alps, the largest contiguous glacier area in Austria, glacier area decreased from 144.2 km² in 1969 to 126.6 km² in 1997 and 116.1 km² in 2006 (APCC 2014).
Post Little Ice Age
Previously, in the 1960s and 1970s, considerable glacial advances had occurred in Austria for a few years (Fig. 1). Over the long run, however, there has been a marked melting trend over the last century and a half. This loss of ice fits well with the rise in temperature during the rewarming since the end of the Little Ice Age.
Figure 1: Annual ice mass balances 1952-2011. Negative values mean ice melt, positive values mark ice gains, 1952-2011. Source: APCC 2014 as to Fischer et al. (2012).
However, the longer-term climate context is also important. 1000 years ago – at the time of the Medieval Warm Period – many Alpine glaciers were as small as they are today. In the transition over to the Little Ice Age, the glaciers in the Alps grew strongly, and reached their greatest extent for the past 10,000 years.
At the end of the Little Ice Age, the glaciers started to melt again, and this continues today. In the Swiss glaciers this has led to the frequent finding of tree remnants from the time of 1000 years A.D., i.e. the Medieval Warm Period. Obviously parts of today’s glacial areas were forested during the times of strong glacier retreat.
Much of the Holocene saw less glaciers in Alps than today
Another more intensive melting phase had already occurred 8000 to 4000 years ago during the so-called Holocene Warm Period when many glaciers were smaller than they are today (Fig. 2).
At the Gepatschferner, the treeline back then was considerably higher than today. There glacier advances and retreats occurred in cycles over the past 4000 years (Nicolussi & Kerschner 2014). The Austrian Expert Report on Climate Change 2014 summarized the pre-industrial glacier lengths in Austria as follows (APCC 2014, Volume 2, Chapter 2):
The glaciers in the Alpine region during the last 11,000 years [Holocene] have been characterized by long periods of comparatively small size in the early and middle Holocene (up to 4,000 years ago) and multiple, far reaching advances, which culminated in the largest glaciers in the “Little Ice Age” (about 1260 to 1860 AD). Today’s glacier extents are repeatedly less or more than in the Early and Middle Holocene.”
Figure 2: Years before 2000 AD. The blue bars mark the times when many alpine glaciers were less than today. Shown are data based on tree rings and C14 dating. Chart changed as to APCC 2014.
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September 22, 2018 at 08:43AM
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