Geometric and dynamic variations of the northeast Greenland Ice Sheet observed with TerraSAR-X and TanDEM-X data

Kurzfassung

Areal, surface elevation and flow variations of an ice sheet characterise its reaction to a changing regional climate. Those transformations result in mass changes of the ice sheet. A warming climate, ultimately causes an acceleration of outlet glaciers and enhanced surface melting [1], both of which contribute to global sea level rise. Eight major marine terminating glaciers on the east coast of Greenland between 71°N and 79°N have been investigated. Three among them are outlets of the Northeast Greenland Ice Stream (NEGIS). They are of particular interest, because they drain 16% of the whole ice sheet [2]. We report calving front locations, ice surface velocity and surface elevation changes for selected glaciers along the coast of northeast Greenland and the NEGIS basin. Ice surface velocity is an essential parameter to monitor environmental changes for ice sheets and glaciers. Together with calving front locations, ice flow velocity is needed as input to quantify the ice export of water terminating glaciers. We apply normalised cross-correlation on backscattering amplitude images to retrieve surface displacements between pairs of 11-days repeat pass TerraSAR-X (TSX) SSC products. The TSX velocities are derived from acquisitions during the months February-March 2015. In addition, time-series of calving front locations are delineated on TSX backscattering amplitude images by a semi-automatic algorithm for the years 20(12/08)-2016 over the most dynamic glaciers, Zachariae Isstrøm and Daugaard Jensen and calving rates are calculated. Surface elevation time series are generated from multiple bistatic TanDEM-X (TDM) CoSSC data acquired in the months December-January 2010/11 and December-January 2013/2014. We create digital elevation models (DEMs) with the Integrated TanDEM-X processor (ITP) and reference them to absolute elevations of the operational TDM global DEM. Subtraction of the absolute elevation mosaics yields a surface elevation change rate for the studied area, which is needed for the estimation of the geodetic mass balance. [1] van den Broeke, Michiel, et al. "Partitioning recent Greenland mass loss." science 326.5955 (2009): 984-986. [2] Khan, Shfaqat A., et al. "Sustained mass loss of the northeast Greenland ice sheet triggered by regional warming." Nature Climate Change 4.4 ( 2014): 292-299.