Improved geodetic glacier mass balance measurements by integrating remote sensing, surface mass balance and firn compaction modelling - a case study from James Ross Island, Antarctica

• Applicant: Professor Dr. Matthias Holger Braun
• Subject Area: Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography ; Physical Geography
• Term: from 2016 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 282369042

• Final Report Year: 2020

Final Report Abstract

During the two Antarctic field campaigns in 2017 and 2018, two automatic weather stations were successfully installed. Both were running until austral summer 2019/2020 and one is still installed. Measurement units installed in the VELMAP project were successfully read-out, providing unique in-situ surface mass balance and glacier surface velocity data. The amount of flight hours with the our helicopter-borne ground penetrating radar antenna was limited, especially in 2017. Nevertheless, in 2018 an almost complete coverage of the outlet area of Gourdon Glacier, and large parts of its catchment area on the James Ross Island dome could be covered. The results were recently published in MDPI Geosciences. They reveal a high significance for the scientific community showing that the published “consensus ice thickness estimate” (Farinotti et al. 2019) strongly overestimates the ice thickness at the outlet of Gourdon Glacier, resulting in an over-estimation of ice discharge of up to 30 Mt a^-1. The results show that the bedrock topography can be highly variable on James Ross Island, and dedicated campaigns in data-scarce regions with a small sampling interval such are required. A huge amount the remote sensing data (TerraSAR-X and Landsat-8 sensors) was investigated to reveal a very detailed time series of glacier surface velocity and frontal area changes in the time frame 2014-2018. The temporal and spatial variations suggest that the bathymetry controls the local impact of oceanic forcing and partially over-modulates the atmospheric influence. It was the first comparison of temporal variations in glacier velocity across whole James Ross Island. The report of the area changes at the glacier front using a common-box approach enabled a comparison with older measurements. The annual recession rates of the glacier fronts suggest a slow-down since the period 1988–2008/2009. The observed acceleration patterns of single glaciers can result in at least temporally strongly deviating mass balances. A comparison of the final elevation changes using elevation models generated from TanDEM-X acquisitions revealed high differences and a high uncertainty, also due to the choice of stable ground. The observed geodetic mass balance changes are relatively low. Thus, a comparison with results from the input-output method is strongly hampered for short time frames in the case of Gourdon Glacier and whole James Ross Island. Nevertheless, the results gained important new knowledge in the working group regarding problems of the TanDEM-X DEM generation in complex topography and the importance of the reference DEM for the estimation of stable ground.

Publications

• Spatial and Temporal Variability of Glacier Surface Velocities and Outlet Areas on James Ross Island, Northern Antarctic Peninsula. Geosciences 2019, 9, 374
  Lippl, S.; Friedl, P.; Kittel, C.; Marinsek, S.; Seehaus, T.C.; Braun, M.H.
  
• Uncertainty Assessment of Ice Discharge Using GPR-Derived Ice Thickness from Gourdon Glacier, Antarctic Peninsula. Geosciences 2020, 10, 12
  Lippl, S.; Blindow, N.; Fürst, J.J.; Marinsek, S.; Seehaus, T.C.; Braun, M.H.