Observation of Changes in Ice Dynamics at the northern Antarctic Peninsula

The physical conditions along the Antarctic Peninsula have undergone considerable changes during the last 50 years. A period of pronounced air temperature raise, increasing ocean temperatures as well as changes in the precipitation pattern have been reported by various authors. Consequently, the glacial systems showed changes including widespread retreat, surface lowering as well as increased flow speeds. During the last decades numerous ice shelves along the Antarctic Peninsula retreated, started to break-up or disintegrated completely. The loss of the buttressing effect caused tributary glaciers to accelerate with increasing ice discharge along the Antarctic Peninsula. Quantification of the mass changes is still subject to considerable errors although numbers derived from the different methods are converging. We analysed time series of various SAR satellite sensors (ERS-1/2 SAR, ENVISAT ASAR, RADARSAT-1, ALOS PALSAR, TerraSAR-X/TanDEM-X, Sentinel-1) to detect changes in ice flow speed and surface elevation. The aim is to study the reaction of glaciers to the changing climatic conditions, especially the readjustments of tributary glaciers to ice shelf disintegration, as well as to better quantify the ice mass loss and its temporal changes. We applyed intensity feature tracking techniques on time series from different SAR satellites over the last 20 years to infer changes in glacier surface velocities. Variations in ice front position are mapped in conjunction with the velocity data sets. High resolution bi-static TanDEM-X satellite data was used to derive digital elevation models by differential SAR interferometry. In combination with ASTER and SPOT stereo images, changes in surface elevations were determined. Altimeter data from ICESat, CryoSat-2 and NASA operation IceBridge ATM were used for vertical referencing and quality assessment of the digital elevation models. Airborne laser scanning, ground penetrating radar (AWI Polar-5/6, NASA operation ice-bridge) and differential GNSS data from field campaigns support the ice discharge analysis. At the Sjogren-Inlet a total mass loss of -50.9±8.3 Gt and a contribution to sea level rise of 18.7±5.2 Gt were found. The current average surface lowering rate amounts to -2.1 m/a. At Dinsmoor-Bombardier-Edgeworth glacier system the results show an increase in surface velocity from 0.9 m/d in 1996 up to 8.8 m/d in 1999 close to the terminus. Subsequently, surface velocities decreased to 1.5 m/d in 2014. The changes in flow speeds are coinciding with changes in front position. The surface elevation changed by at least -130±15 m between 1995 and 2014 and -40.7±3.9 Gt of ice were discharged. The detailed multi-mission time series analysis will support the imbalance calculation in the research area and the interpretation on how ice shelf disintegration affects the tributary glaciers.