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The Cryosphere An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/tc-2017-75
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
04 May 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal The Cryosphere (TC).
Increased West Antarctic ice discharge and East Antarctic stability over the last seven years
Alex S. Gardner1, Geir Moholdt2, Ted Scambos3, Mark Fahnstock4, Stefan Ligtenberg5, Michiel van den Broeke5, and Johan Nilsson1 1Jet Propulsion Laboratory, California Institute of Technology, Pasadena CA 91109
2Norwegian Polar Institute, Fram Centre, 9296 Tromsø, Norway
3National Snow and Ice Data Center (NSIDC), University of Colorado at Boulder, Boulder CO 80303 USA
4Geophysical Institute, University of Alaska Fairbanks, Fairbanks AK 99775 USA
5Institute for Marine and Atmospheric research Utrecht (IMAU), Utrecht University, Utrecht, the Netherlands
Abstract. Ice discharge from large ice sheets plays a direct role in determining rates of sea level rise. We map present-day Antarctic-wide surface velocities using Landsat 7 & 8 imagery spanning 2013–2015 and compare to earlier estimates derived from synthetic aperture radar, revealing heterogeneous changes in ice flow since ~ 2008. The new mapping provides complete coastal and inland coverage of ice velocity with a mean error of < 10 m yr-1, resulting from multiple overlapping image pairs acquired during the daylit period. Using an optimized flux gate, ice discharge from Antarctica is 1932 ± 38 Gigatons per year (Gt yr-1) in 2015, an increase of 35 ± 15 Gt yr-1 from the time of the radar mapping. Flow accelerations across the grounding lines of West Antarctica's Amundsen Sea Embayment, Getz Ice Shelf and Marguerite Bay on the western Antarctic Peninsula, account for 89 % of this increase. In contrast, glaciers draining the East Antarctic Ice Sheet have been remarkably stable over the period of observation. Including modeled rates of snow accumulation and basal melt, the Antarctic ice sheet lost ice at an average rate of 186 ± 93 Gt yr-1 between 2008 and 2015. The modest increase in ice discharge over the past 7 years is contrasted by high rates of ice sheet mass loss and distinct spatial patters of elevation lowering. This suggests that the recent pattern of mass loss in Antarctica, dominated by the Amundsen Sea sector, is likely part of a longer-term phase of enhanced glacier flow initiated in the decades leading up to the first continent wide radar mapping of ice flow.

Citation: Gardner, A. S., Moholdt, G., Scambos, T., Fahnstock, M., Ligtenberg, S., van den Broeke, M., and Nilsson, J.: Increased West Antarctic ice discharge and East Antarctic stability over the last seven years, The Cryosphere Discuss., https://doi.org/10.5194/tc-2017-75, in review, 2017.
Alex S. Gardner et al.
Alex S. Gardner et al.
Alex S. Gardner et al.

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We map present-day Antarctic surface velocities from Landsat imagery and compare to earlier estimates from radar. Flow accelerations across the grounding lines of West Antarctica’s Amundsen Sea Embayment, Getz Ice Shelf and the western Antarctic Peninsula, account for 89 % of the observed increase in ice discharge. In contrast, glaciers draining the East Antarctic have been remarkably stable. Our work suggests that patterns of mass loss are part of a longer-term phase of enhanced flow.
We map present-day Antarctic surface velocities from Landsat imagery and compare to earlier...
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