Rockglacier acceleration in the Turtmann valley (Swiss Alps): Probable controls

Temporal variations in mountain permafrost creep are discussed within a regional study on rockglacier ¹

In order to emphasize the autonomy of the phenomenon, the term ‘rockglacier’ is expressed as one word in this article, in accordance with Barsch 1988.

kinematics. On all investigated active rockglaciers in the Turtmann valley, a distinct acceleration of horizontal velocities has been recorded since the early 1990s. Since variations in rockglacier movement are mainly discussed in the context of temperature fluctuations in the current literature, the link between surface velocities and temperature development is investigated at two different scales. The signal of rockglacier speed-up in the period 1993–2001 (here termed as ‘regional signal’ since all rockglaciers show this behaviour) fits well with the general increase in air temperature recorded during the 1990s. On the local scale, the pattern of BTS values coincides well with the surface-velocity pattern, but in areas with high velocities the BTS temperatures are clearly below −3°C. Thus, marginal permafrost occurrence is not indicated in this data and the high velocities probably do not result directly from ‘warming’ permafrost conditions, as is suggested by other studies.

Keywords:

• acceleration
• climate change
• dynamics
• rockglacier
• Swiss Alps

Acknowledgements

The study was funded by the Deutsche Forschungsgemeinschaft (DFG) as a PhD project within the Research Training Group ‘Landform – a structured and variable boundary layer’ (Graduiertenkolleg 437). Special thanks are dedicated to Reinhard Böhm for the homogenized temperature data of the Alps and the Sion station and to the Swiss Federal Office of Topography for access to the aerial photographs. Further thanks are due to Kirsten von Elverfeldt and all the helping hands in various field campaigns and at the photogrammetric workstation at the Department of Geography in Zürich. We gratefully acknowledge the valuable comments on the manuscript by Ole Humlum and Martin Kirkbride.

Notes

In order to emphasize the autonomy of the phenomenon, the term ‘rockglacier’ is expressed as one word in this article, in accordance with Barsch 1988.