Investigation of Surge Dynamics on the Glaciers in the Karakoram Region and Alaska using TerraSAR-X and TanDEM-X Data
Vijay, Saurabh; Rankl, Melanie; Matthias, Braun
Friedrich-Alexander-Universität Erlangen-Nürnberg, GERMANY
Many of the glaciers in the Karakoram region and in Alaska are known to show a surge-type behaviour. The glaciers in the Karakoram region currently advance, whereas Alaskan glaciers show considerable contribution to sea level due to increased flow and melt. The surge behaviour and frequency as well as the underlying mechanisms are not well studied in both areas. In particular for the Karakoram region, surges are known to cause damming of upstream glacier rivers and putting considerable threat to local communities and infrastructure. Changes of flow and mass of such glaciers can be strongly out of phase to the climate signal of the nearby region. Various reasons including changes in the hydrological conditions have been identified as causes for surging. During an active phase of a surge, lasting over several months to years, glaciers advance and show a significant speed-up and surface crevasse patterns. Mass is transported from the upper catchment towards lower elevations. In a quiescent phase, the ice masses transported previously downward, melt down and the glacier profile starts to steepen again. This study investigates the surge activities in both areas. For Alaska, we show an example from the recent Bering Glacier surge, while for Karakoram glaciers ongoing advances and surges of smaller valley glaciers are presented. Glacier surface velocities and surface elevation changes are determined using high spatial resolution X band SAR sensor onboard TerraSAR-X and TanDEM-X satellites. SAR offset tracking technique is used over TerraSAR-X imagery to determine glacier surface velocities. Archived data from ALOS PALSAR, ERS-1/2 SAR and ENVISAT ASAR are also used to identify changes in flow velocities. The bi-static TanDEM-X science products are used to determine elevation and volume changes due to recent surge events. The temporal trend in surface elevation is determined by comparing TanDEM-X DEMs with SRTM DEM and IceSAT surface height tracks, while in case of Alaska, repeat TanDEM-X data is analysed. The present study quantifies surface velocities and temporal surface elevation changes for detailed investigation of surging glaciers.