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Contenuto archiviato il 2024-05-27

Global Glacier Mass Continuity

Final Report Summary - ICEMASS (Global Glacier Mass Continuity)

The ICEMASS project aimed at (A) quantifying glacier surface velocity over a global scale and for several time periods using mainly correlation of repeat satellite images, (B) measuring glacier thickness changes over a global scale using satellite altimetry and digital elevation models, and (C) combining both towards regional-scale glacier mass budgets.

For goal (A) methods of feature tracking in repeat satellite images were refined. Thereby, a first main focus was on improving the estimation of velocities under non-optimal image conditions in order to expand the temporal and spatial extent of measurements. A novel generic processing scheme was developed and demonstrated. A second main focus under goal (A) was on a high degree of automation in order to be able to cover large areas over several time periods. Methods were developed to automatize search, download and processing of in particular EU Copernicus Sentinel-1, Sentinel-2, and NASA/USGS Landsat image data. Glacier velocities, in parts repeated, were measured for a number of regions and a set of changes, such as from glacier surges, were analysed.

For goal (B), one main focus was on improved analysis of satellite laser altimetry (NASA ICESat) over mountain topography. The project team is able to derive glacier elevation change (and snow thickness) information to an extent and with an accuracy that by far exceeds the original satellite mission plans. The second main focus within goal (B) was on improving elevation models from satellite stereo, in particular from the now almost 20-year long ASTER optical satellite stereo mission. Analytic co-registration of elevation models was developed and is widely used in the scientific community. The ICEMASS project team is able to produce ASTER satellite elevation models with higher quality than the ones from the official US/Japan ASTER processing line. As a side product for validation of these results, routines were developed for generating DEMs using Structure-From-Motion technology from simple action cameras and commercial hand-held GPS without the requirement of ground control. The elevation change techniques developed were and are continued to being applied to a number of regions including Norway, Svalbard, Greenland and Himalaya.

For goal (C), models were developed to combine elevation changes and surface velocities in order to quantify mass balance terms and separate their contributions towards better understanding of the mass changes found. Fully 3-dimensional thermo-dynamic coupled flow models were developed and applied to several individual glaciers, providing unique insights in glacier processes and their response to climatic changes. The methods and results of goals (A) and (B) were also combined to better understand natural hazards from glaciers, including glacier lake outbursts, and the so far largely overlooked collapsing of large parts of low-angle glaciers leading to extraordinary large and fast ice-rock avalanches.

Highlight results from ICEMASS and related publications in high-impact interdisciplinary journals include the quantification and climatic interpretation of glacier and lake changes in High Mountain Asia, global glacier volume changes, improved understanding of glacier basal sliding, and improved understanding of glacier instabilities such as glacier surges and catastrophic collapsing of glaciers. As project spin-offs, a number of novel methods and applications have been developed, for instance related to river flow, earthquake-induced displacements, glacier disasters, or permafrost dynamics.