Description: This study examines present-day changes of the Antarctic ice sheet (AIS) by means of different data sets. We make use of monthly gravity field solutions acquired by the Gravity Recovery and Climate Experiment (GRACE) to study mass changes of the AIS for a 10-year period. In addition to "standard" solutions of release 05, solutions based on radial base functions were used. Both solutions reveal an increased mass loss in recent years. For a 6-year period surface-height changes were inferred from laser altimetry data provided by the Ice, Cloud, and land Elevation Satellite (ICESat). The basin-scale volume trends were converted into mass changes and were compared with the GRACE estimates for the same period. Focussing on the Thwaites Glacier, Landsat optical imagery was utilised to determine ice-flow velocities for a period of more than two decades. This data set was extended by means of high-resolution synthetic aperture radar (SAR) data from the TerraSAR-X mission, revealing an accelerated ice flow of all parts of the glacier. ICESat data over the Thwaites Glacier were complemented by digital elevation models inferred from TanDEM-X data. This extended data set exhibits an increased surface lowering in recent times. Passive microwave remote sensing data prove the long-term stability of the accumulation rates in a low accumulation zone in East Antarctica over several decades. Finally, we discuss the main error sources of present-day mass-balance estimates: the glacial isostatic adjustment effect for GRACE as well as the biases between laser operational periods and the volume-mass conversion for ICESat.

Description: 〉Within the IACS working group on Regional Assessments of Glacier Mass Change (RAGMAC) an intercomparsion experiment was set up to evaluate variations of volume change results between different processing chains and sensors. For this purpose, high resolution height change maps over two alpine glaciers, Aletschgletscher and Hintereisferner, were provided as independent validation data. Here we will target the influence of TanDEM-X bistatic scene selection for reporting height change rates and their difference to the provided validation data keeping a common processing chain. Ideally, two timely relevant, bistatic end of summer acquisitions from the same orbit and a suitable height of ambiguity should be utilized to calculate a DEM difference map from TanDEM-X data. In many cases however, the ideal set of criteria cannot be met and a scene selection from the TanDEM-X mission database has to be performed. SAR acquisitions from different seasons might enhance elevation biases due to signal penetration depending on the observed region. A combination of ascending and descending orbits will potentially increase the co-registration error and leads to an uneven sampling of the terrain due to different locations of shadow and layover caused by the steep terrain around many mountain glaciers. We will attempt to formulate a set of best-practices for TanDEM-X scene selection and future data acquisition ordering when targeting height change rate calculation for mountain glaciers.〈/p〉

Description: The mountain and foothill regions of the Republic of Uzbekistan occupy about 12% of the country’s territory. They are located in the East and South-East (Western Tien-Shan and Hissar-Alay mountains). Outstanding progress in the republic’s economic development predetermines the future active development of Uzbekistan’s mountain territories including tourism, roadbuilding and electric power line construction. The infrastructure development and recreational activities in the mountains can be threatened by avalanches and debris flow occurrence. The relevance of solving the scientific and practical tasks in studies of glaciers and snow avalanches is due to the need for current assessments of climate changes in the region, the impact on hydrological regime in glacierized basins, and timely protection in snow-avalanche prone areas and in the case of GLOF.Using TanDEM-X bistatic data, as well as the global TDM-DEM and SRTM-based NASADEM, geodetic mass balances were estimated for glaciers located in the upper part of the Pskem River basin for recent decades. However, the SAR data over the relatively small glaciers and the complex topography are largely affected by layover and shadow. For the present work recent bistatic TanDEM-X SAR acquisitions with different orbit direction configuration will be processed aiming at reducing the DEM gaps on the glaciers. The potential of interferometric SAR data pairs of the TerraSAR-X/PAZ constellation for deriving glacier movement and snow avalanche maps will be evaluated. The detection of avalanche paths and identification of the avalanche depositions in well-studied areas of Uzbekistan using SAR backscatter signatures and numerical simulations will be investigated.

Description: Totten Glacier is the principal source of ice loss from the East Antarctic Ice Sheet. Although the East Antarctic Ice Sheet as a whole has remained approximately in balance, the response of Totten Glacier to climate forcing remains a key source of uncertainty in predicting its future contribution to sea level rise. Here, we compare and combine estimates of the mass change of Totten Glacier and it's surrounding region from satellite measurements of changes in its volume, ice speed and gravitational potential acquired over the past two decades between 2002 and 2022. Ice losses from the Totten Glacier catchment and two surrounding areas – the Vincennes Bay region and the Moscow University catchment – have doubled since 2002 from 8.5 ± 0.7 Gt/yr to 20 ± 1.5 Gt/yr. We find the largest disagreement in Vincennes Bay, which remains a challenging region in which to monitor mass changes - likely a combination of a paucity in observations of ice thickness, and the regions’ small mass imbalance compared to local SMB fluctuations. Using a regional climate model, we show that only Totten Glacier is losing ice due to it flowing faster than it’s equilibrium state, although the rate of its dynamic ice loss has slowed by 60 %. In total, the region has lost 285 ± 19 Gt of ice and raised the global sea level by 0.8 ± 0.1 mm, with the majority (62 %) of this loss originating from Totten Glacier itself.

Description: Floating ice shelves fringe 74% of Antarctica's coastline, providing a direct link between the ice sheet and the surrounding oceans. A better understanding of Antarctic ice shelves and the physical processes affecting them has been the main objective of ESA’s Polar+ Ice Shelves project. A suite of geophysical products based on Earth Observation datasets from the last decade and modelling has been defined and produced over selected target ice shelves in Antarctica. One of these products, the ice shelf area change, is an important indicator of ice shelf stability in a warming climate, being affected by grounding line retreat as a possible consequence of ice thinning and calving events including ice shelf disintegration or collapse.An ice shelf is bounded at its seaward margin by the calving front while its inland border to the grounded ice of the Antarctic continent is given by the grounding line. Our calving front location is derived from Cryosat-2 swath elevation, while the grounding line is detected as the upper limit of ice shelf tidal flexure from Sentinel-1 and, prior to 2015, ERS-1/2 interferometric data. Time series of complete ice shelf delineations are obtained from the combination of these two products. It is possible to track absolute and relative area change of an ice shelf and additionally to partition the change into the individual contributions induced by the calving front and grounding-line migration. Examples of annual ice shelf perimeters of major ice shelves from 2011 to the present will be shown.