Journal cover Journal topic
The Cryosphere An interactive open-access journal of the European Geosciences Union
The Cryosphere, 11, 1199-1211, 2017
http://www.the-cryosphere.net/11/1199/2017/
doi:10.5194/tc-11-1199-2017
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
12 May 2017
Dynamic changes on the Wilkins Ice Shelf during the 2006–2009 retreat derived from satellite observations
Melanie Rankl1, Johannes Jakob Fürst1, Angelika Humbert2,3, and Matthias Holger Braun1 1Friedrich-Alexander Universität Erlangen-Nürnberg, Institute of Geography, 91058 Erlangen, Germany
2Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Glaciology Section, 27568 Bremerhaven, Germany
3University of Bremen, Department of Geosciences, 28359 Bremen, Germany
Abstract. The vast ice shelves around Antarctica provide significant restraint to the outflow from adjacent tributary glaciers. This important buttressing effect became apparent in the last decades, when outlet glaciers accelerated considerably after several ice shelves were lost around the Antarctic Peninsula (AP). The present study aims to assess dynamic changes on the Wilkins Ice Shelf (WIS) during different stages of ice-front retreat and partial collapse between early 2008 and 2009. The total ice-shelf area lost in these events was 2135 ± 75 km2 ( ∼  15 % of the ice-shelf area relative to 2007). Here, we use time series of synthetic aperture radar (SAR) satellite observations (1994–1996, 2006–2010) in order to derive variations in surface-flow speed from intensity-offset tracking. Spatial patterns of horizontal strain-rate, stress and stress-flow angle distributions are determined during different ice-front retreat stages. Prior to the final break up of an ice bridge in 2008, a strong speed up is observed, which is also discernible from other derived quantities. We identify areas that are important for buttressing and areas prone to fracturing using in-flow and first principal strain rates as well as principal stress components. Further propagation of fractures can be explained as the first principal components of strain rates and stresses exceed documented threshold values. Positive second principal stresses are another scale-free indicator for ice-shelf areas, where fractures preferentially open. Second principal strain rates are found to be insensitive to ice-front retreat or fracturing. Changes in stress-flow angles highlight similar areas as the in-flow strain rates but are difficult to interpret. Our study reveals the large potential of modern SAR satellite time series to better understand dynamic and structural changes during ice-shelf retreat but also points to uncertainties introduced by the methods applied.

Citation: Rankl, M., Fürst, J. J., Humbert, A., and Braun, M. H.: Dynamic changes on the Wilkins Ice Shelf during the 2006–2009 retreat derived from satellite observations, The Cryosphere, 11, 1199-1211, doi:10.5194/tc-11-1199-2017, 2017.
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