Transition of flow regime along a marine-terminating outlet glacier in East Antarctica

• Published in: The Cryosphere
• Main Authors: Callens, D, Matsuoka, K, Steinhage, D., Smith, B., Pattyn, F.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: COPERNICUS GESELLSCHAFT MBH 2014
• Subjects: East Antarctica; Dronning Maud Land; Shirase Glacier; Land Glacier; Antarc*; Antarctica; The Cryosphere
• Online Access: https://epic.awi.de/id/eprint/34221/; https://epic.awi.de/id/eprint/34221/1/tc-8-867-2014.pdf; https://hdl.handle.net/10013/epic.42550; https://hdl.handle.net/10013/epic.42550.d001

We present results of a~multi-methodological approach to characterize the flow regime of West Ragnhild Glacier, the widest glacier in Dronning Maud Land, Antarctica. A new airborne radar survey points to substantially thicker ice (> 2000 m) than previously thought. According to the new data, West Ragnhild Glacier discharges 13–14 Gt yr−1. Therefore, it is one of the three major outlet glaciers in Dronning Maud Land. Glacier-bed topography is distinct between the upstream and downstream section. In the downstream section (< 65 km upstream of the grounding line), the glacier overlies a wide and flat basin well below the sea level while the upstream region is more mountainous. Spectrum analysis of the bed topography reveals a clear contrast between these two regions, suggesting that the downstream area is sediment covered. The bed returned power varies by 30 dB within 20 km near the bed flatness transition, which suggests that water content at bed/ice interface increases over a short distance downstream, hence pointing to water-rich sediment. Ice flow speed observed in the downstream part of the glacier (~ 250 m yr−1) can only be explained if basal motion accounts for ~ 60% of the surface motion. All above lines of evidence (sediment bed, wetness and basal motion) and the relative flat grounding zone give the potential for West Ragnhild Glacier to be more sensitive to external forcing compared to other major outlet glaciers in this region which are more stable due to their bed geometry (e.g. Shirase Glacier).