Recent speed‐up of an alpine rock glacier: an updated chronology of the kinematics of outer hochebenkar rock glacier based on geodetic measurements

Abstract

Surface velocities have been regularly monitored at the rock glacier in Outer Hochebenkar, Ötztal Alps, Austria since the early 1950s. This study provides an update to previously published surface velocity time series, showing mean profile velocities of four cross profiles since the beginning of the measurements (1951,1954, 1997; depending on the profile), as well as single block displacements from 1998 to 2015. Profiles P1, P2 and P3 have moved between 42 and 90 m, at mean velocities between 0.70 and 1.48 m yr^–1, since they were first established in the early 1950s (1951/54). Profile P0, established in 1997, has since moved 13 m or 0.75 m yr^–1. An acceleration can be observed at all profiles since the late 1990s, with a particularly sharp velocity increase since 2010. All profiles reached a new maximum velocity in 2015, with 1.98 m yr^–1 at the slowest profile (P0) and 6.37 m yr^–1 at the fastest profile (P1). Year‐to‐year variations in profile velocities cannot be clearly attributed to inter‐annual variations of climatic parameters like mean annual air temperature, summer temperature, positive degree days, or precipitation. However, higher correlation is found between velocities and cumulative anomalies of air temperature (mean annual air temperature and positive degree days) and summer precipitation, suggesting that these parameters play a key role for the movement of the rock glacier. The lower profiles (P0, P1) show more pronounced year‐to‐year variations than the upper profiles (P2, P3). It is considered likely that processes other than climatic forcing (e.g. sliding, topography) contribute to the different velocity patterns at the four profiles.

Key words:

• rock glacier
• kinematics
• Hochebenkar

Acknowledgements

We wish to thank Heralt Schneider for his expertise and for generously providing us with the results of his many years of measurements. We also thank many helpers in the field, without whom the continued measurements at Outer Hochebenkar would not be possible. Last but not least, we thank the anonymous reviewers and the editor for their helpful and constructive input!

Notes

1. Climate data Obergurgl, 1953–2011 (http://doi.pangaea.de/10.1594/PANGAEA.806635, 8 Feb., 2016).

Additional information

Notes on contributors

Lea Hartl

Andrea Fischer, Institute for Interdisciplinary Mountain Research, Austrian Academy of Sciences. Technikerstr. 21a, ICT Building, 6020 Innsbruck, Austria, Email: [email protected]

Andrea Fischer

Lea Hartl, Institute for Interdisciplinary Mountain Research, Austrian Academy of Sciences. Technikerstr. 21a, ICT Building, 6020 Innsbruck, Austria, Email: [email protected], Institute of Geography, University of Innsbruck. Innrain 52f; 6020 Innsbruck, Austria

Martin Stocker‐waldhuber

Jakob Abermann, Asiaq‐Greenland Survey, PO Box 1003, 3900 Nuuk, Greenland, Email: [email protected]

Jakob Abermann

Martin Stocker‐Waldhuber, Institute for Interdisciplinary Mountain Research, Austrian Academy of Sciences. Technikerstr. 21a, ICT Building, 6020 Innsbruck, Austria, Email: [email protected], Institute for Geosciences and Geography, Physical Geography, Martin‐Luther‐University of Halle‐Wittenberg, 06099 Halle (Saale), Germany