The longterm signal of climate change in the Swiss Alps: Glacier retreat since the end of the Little Ice Age and future ice decay scenarios

Abstract

The study presented summarizes selected results of a nationwide glacier inventory project supported by the Swiss National Research Programme (NRP 31) on «Climate Changes and natural Catastrophes» completed in 1999. The data were obtained by the glaciological reconstruction and homogeneous parameterization of the 1850 glacier situation in the Swiss Alps (the last advance period of the Little Ice Age). The statistical comparison with the present-day glaciation (recorded in 1973) provides for the first time a complete synopsis of various glaciological and geographical aspects of longterm glacier retreat in the period since 1850. Attempts were made, based on the new inventory data, to model potential ice decay scenarios for the Swiss Alps and to estimate the glaciological consequences of an enhanced atmospheric warming. Since the end of the Little Ice Age the mean vertical 2:1-ELA shift (AAR = 0.67) of glaciers with normal topographic characteristics is in the order of +90 m. This unfavourable change in mass balance conditions has led to a substantial glacier area loss in the Swiss Alps of approximately 500 km² (27 percent) and to an ice volume loss of 33 km³ (31 percent) The relative amount of ice-decay (area, volume, length) is highly variable on an individual scale but in general shows a significant inverse correlation with former glacier size. The simulation of different 2:1-ELA-rise scenarios outlines the high sensitivity of alpine glaciation in respect of future climate changes. A strongly accelerated but regionally differentiated glacier decay within the next few decades would be the result of the 21^st century based atmospheric warming scenarios.