First results from thermal investigations of rock glaciers in the Slovak High Tatra Mountains, Western Carpathians
Abstrakt
We present the first results from thermal investigations of seven rock glaciers located in the Slavkovská dolina and Veľká Studená dolina valleys. While mean air temperatures for the whole observation period (between October 2014 and August 2015) range between +1.6 and +2.6 oC, mean values of GSTs are between -1.7 and +1.7 oC with an average of +0.4 oC.
Three of the seven rock glaciers have average GST < 0 oC and one rock glacier has average GST < +0.5 oC. All investigated rock glaciers show negative surface offset up to 3.6 oC.
GSTs recorded during the BTS window have an average of -4.2 oC and range between -6.4 and -2.6 oC, suggesting probable and possible permafrost occurrence at six and one of the rock glaciers, respectively. BTS values measured during the field campaign have an average of -3.3 oC and indicate probable and possible permafrost at three and four rock glaciers, respectively.
However, considerable spatial heterogeneity of BTS values, ranging between -8.3 and -0.1 oC, exists over the rock glacier surfaces with the lowest BTS values occurring at the foot of talus slopes and along the most distinct furrows. Generally, rock glacier areas show significantly cooler conditions compared to nearby vegetated locations, where average BTS value is -0.6 oC.
Based on these preliminary results we infer that permafrost is likely to occur within all the studied rock glaciers. Given a relatively narrow altitudinal gradient, GSTs and BTS have no clear relationship to altitude, but local-scale variations in potential incoming solar radiation, snow cover thickness, topography, debris size, land cover and/or possible ventilation effects are the dominant factors.
Rock glaciers show significant negative thermal anomaly, which may favour presence of permafrost at other rock glacier bodies or scree slopes situated below the lower limit of suggested regional permafrost occurrence (1930 +- 150-200 m asl).