Purpose: The Alpine setting is characterized by the presence of periglacial environments rapidly changing due to global warming. In this context, landscape evolution is affected by movements of rock glaciers. They are widespread in European Alps and significant for their content of Alpine permafrost. The external temperature is considered one of the most important factors controlling rock glacier flow variation at both inter-annual and seasonal time scales, showing mean velocities ranging from centimeters to meters per year. This study employs Multi-temporal DInSAR technique to assess the deformation evolution of the rock glaciers and to classify their activity based on DInSAR results and geomorphological features. Methods: This work investigates the rock glacier stability in Val Senales (Italian Alps) by processing a dataset of 345 Sentinel-1 SAR images acquired between 2015 and 2022. Multi-temporal DInSAR processing has been performed by exploiting both persistent and distributed scatterers through SPINUA algorithm. Ad hoc processing strategies have been adopted in order to overcome both signal decorrelation due to changeable snow cover conditions, and aliasing due to very high displacement rates. The algorithm has been run by selecting springsummer acquisitions and forced to search for solutions corresponding to phase changes behind the aliasing limit. The DInSAR results (both mean velocity and displacement time series) have been ingested into a GIS environment together with other informative layers such as rock glacier classes (according to [1]) optical orthoimages, multi-temporal mean SAR amplitude, DInSAR coherence maps, permafrost index map, and Difference Vegetation Index (NDVI). Then, the mean velocity has been classified by adopting the more recent classification proposed in [2]. Lastly, the rock glacier activity has been reclassified by overlapping all available informative layers. Results: The resulting mean velocity map shows several areas affected by ground displacements. Many of these areas corresponds to areas within the border of the rock glaciers in the area of interest. A further interesting issue is related to lack of DInSAR coherent targes just within the rock glacier borders that could be related to the presence of very high displacement rates. This has been investigated by exploring changes in orthoimages from different years as well as maps of DInSAR phase and coherence. The new classification has been compared to that derived according to [1] showing several differences. Conclusions: The Multi-temporal DInSAR technique has proved to be useful for the assessment of rock glaciers, although the interpretation of the results must be supported by other informative layers. The comparison of the two classifications shows both the usefulness of the more recent techniques and the evolution of rock glaciers in recent years due to global warming.
Assessment of alpine rock glacier activity by exploiting SAR interferometric products
Fabio Bovenga;Ilenia Argentiero;Antonella Belmonte;Alberto Refice;
2023
Abstract
Purpose: The Alpine setting is characterized by the presence of periglacial environments rapidly changing due to global warming. In this context, landscape evolution is affected by movements of rock glaciers. They are widespread in European Alps and significant for their content of Alpine permafrost. The external temperature is considered one of the most important factors controlling rock glacier flow variation at both inter-annual and seasonal time scales, showing mean velocities ranging from centimeters to meters per year. This study employs Multi-temporal DInSAR technique to assess the deformation evolution of the rock glaciers and to classify their activity based on DInSAR results and geomorphological features. Methods: This work investigates the rock glacier stability in Val Senales (Italian Alps) by processing a dataset of 345 Sentinel-1 SAR images acquired between 2015 and 2022. Multi-temporal DInSAR processing has been performed by exploiting both persistent and distributed scatterers through SPINUA algorithm. Ad hoc processing strategies have been adopted in order to overcome both signal decorrelation due to changeable snow cover conditions, and aliasing due to very high displacement rates. The algorithm has been run by selecting springsummer acquisitions and forced to search for solutions corresponding to phase changes behind the aliasing limit. The DInSAR results (both mean velocity and displacement time series) have been ingested into a GIS environment together with other informative layers such as rock glacier classes (according to [1]) optical orthoimages, multi-temporal mean SAR amplitude, DInSAR coherence maps, permafrost index map, and Difference Vegetation Index (NDVI). Then, the mean velocity has been classified by adopting the more recent classification proposed in [2]. Lastly, the rock glacier activity has been reclassified by overlapping all available informative layers. Results: The resulting mean velocity map shows several areas affected by ground displacements. Many of these areas corresponds to areas within the border of the rock glaciers in the area of interest. A further interesting issue is related to lack of DInSAR coherent targes just within the rock glacier borders that could be related to the presence of very high displacement rates. This has been investigated by exploring changes in orthoimages from different years as well as maps of DInSAR phase and coherence. The new classification has been compared to that derived according to [1] showing several differences. Conclusions: The Multi-temporal DInSAR technique has proved to be useful for the assessment of rock glaciers, although the interpretation of the results must be supported by other informative layers. The comparison of the two classifications shows both the usefulness of the more recent techniques and the evolution of rock glaciers in recent years due to global warming.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
