科研之友
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摘要
Active rock glaciers are permafrost landforms in high relief terrain moving slowly downward. Despite the fact that the movement of a rock glacier is influenced by site specific factors (e. g. slope, bedrock topography), climate and thereby mainly temperature are of main importance for surface flow velocity and its changes over time. However, establishing statistical significant correlations between climatic parameters and interannual variations in velocity is difficult and was hardly attempted because physical processes linking climate to rock glacier dynamics are complex and act at various spatial and temporal scale. In this study we compared rock glacier velocity data with different climatic parameters at three rock glaciers in the Hohe Tauern Range, Central Austria. Our study is based on annual geodetic field campaigns (maximum time span 1995-2011) with complementary data from aerial photogrammetric measurements covering up to 57 years totally. The three time series are some of the longest for the European Alps, therefore provide valuable insight into rock glacier velocity changes. Furthermore, continuous ground surface (maximum 10 years of data) and near ground-surface temperature (maximum 5 years) from the three rock glaciers, air temperature data from two meteorological stations, and complementary climate data from an official meteorological observatory were used. Results show that rock glacier velocities between the mid-1950s and mid-1990s were lower compared to the period afterwards. Either the time spans 2003-2004 or 2010-2011 was the fastest period with velocities about 1.5 to 3.2 times faster compared to the minimums in the last 57 years. Intercomparison of the three velocity time series showed strong correlations also revealing six different main phases: low velocities in the mid-1990s, faster velocities at the end of the 1990s, low velocities in 1999-2000, steady increase in velocity peaking in 2003-2004, steady deceleration in velocities until 2007-2008, and steady but rather fast increase until 2011. Comparison with air temperature data revealed a time lag of one to more years for acceleration caused by warm air temperatures. In contrast, strong cooling causes a slightly faster deceleration possibly related to the availability of liquid water within the rock glacier. Correlation analysis of rock glacier velocity with 13 different climatic parameters revealed that the interrelationships are complex. Only 13 out of 270 pairs of variables correlated statistically significant. Results showed for instance that a four-times milder winter measured at the ground surface causes an increase in velocity by 1.5 times. In contrast, an only two-times milder winter measured at one meter depth causes also an acceleration of 1.5 times indicating different influences of the temperature at the surface or at one meter depth to velocities. Furthermore, a warming of the mean annual ground temperature at one meter depth by only 1 degrees C from -2 degrees C to -1 degrees C increases velocity by 1.5 times. All three studied rock glacier fronts are close to the local lower limits of permafrost. Therefore, the inversion from velocity increase due to warming of permafrost to decrease due to substantial thawing of permafrost will possibly occur in this century, a plausible hypothesis for many other rock glaciers in Austria.
- 出版日期2012
