Three-dimensional internal structure and characteristics of periglacial landforms as a key to enhance the understanding of process dynamics and sensitivity to climate change
Final Report Abstract
Periglacial environments are facing dramatic changes. Warming air temperatures and strong snow cover variations fundamentally affect land-forming processes in this hotspot region of climate change. The internal structure of periglacial landforms contains valuable information on the past and present environmental conditions. To benefit from this archive an enhanced knowledge of the subsurface heterogeneity is crucial. An assessment of the prevailing process regimes and evaluation of the sensitivity of different landform units to environmental changes is enabled. The project focused on the assessment of structural variations in the subsurface of rock glaciers, solifluction lobes, palsas/lithalsas and patterned ground that occur between the different landform types, but also between landform units of the same type. Detailed information on ground characteristics, active layer thickness, frost table topography and extent of the permafrost body was gained by multi-dimensional geophysical imaging (Electrical Resistivity Imaging, ERI and Ground-Penetrating Radar, GPR). The study areas are located in high-alpine environments in Switzerland and two of them are located in the subarctic highlands of Iceland. Additionally, surface and subsurface temperature values were continuously recorded at selected study sites. From a methodological view, the field work focused on the application of quasi-3-D electrical resistivity imaging, an approach in which data from multiple two-dimensional data sets is combined to create one three-dimensional data set. This permits a three-dimensional delimitation of subsurface structures and a spatial investigation of the distribution of permafrost and its characteristics. At one of the high-alpine study sites, a highly variable ice content indicates a complex development of the investigated rock glacier assembly. The local formation of ground ice is attributed to an embedding of surface patches of snow or ice into the subsurface by rockfall. At another study site the results indicate the occurrences of isolated ground ice patches in the subsurface of a nearly 500 m long rock glacier. Detected characteristics of the internal structure enable a reconstruction of the development of the rock glacier, in which a temporary override of an adjacent glacier tongue on the pre-existing rock glacier is considered crucial for the current distribution of ground ice. However, the presented results show that buried glacier ice is absent in the subsurface of this rock glacier. At the subarctic study site, the results show that the internal structure of palsas can be used to deduce their current development stage and to assess their past and future development. Results affirm a long history of palsa development but further indicate recent changes in environmental conditions.
Publications
- (2017): Internal structure of two alpine rock glaciers investigated by quasi-3-D electrical resistivity imaging. The Cryosphere, 11, 841-855
Emmert, A. and C. Kneisel
(See online at https://doi.org/10.5194/tc-11-841-2017) - (2020): Glacier–permafrost interaction at a thrust moraine complex in the glacier forefield Muragl, Swiss Alps. Geosciences, 10, 205
Kunz, J. and C. Kneisel
(See online at https://doi.org/10.3390/geosciences10060205) - (2020): The Internal structure of periglacial landforms. Assessments of subsurface variations in permafrost-related and frost-related phenomena by multidimensional geophysical investigations. Würzburg University Press
Emmert, A.
