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The Cryosphere An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/tc-2017-251
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
12 Feb 2018
Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal The Cryosphere (TC).
Ice velocity of Jakobshavn Isbræ, Petermann Glacier, Nioghalvfjerdsfjorden and Zachariæ Isstrøm, 2015–2017, from Sentinel 1-a/b SAR imagery
Adriano Lemos1, Andrew Shepherd1, Malcolm McMillan1, Anna E. Hogg1, Emma Hatton1, and Ian Joughin2 1Centre for Polar Observation and Modelling, University of Leeds, Leeds, UK
2Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, Washington, USA
Abstract. Systematically monitoring Greenland’s outlet glaciers is central to understanding the timescales over which their flow and sea level contributions evolve. In this study we use data from the new Sentinel-1a/b satellite constellation to generate 187 velocity maps, covering 4 key outlet glaciers in Greenland; Jakobshavn Isbræ, Petermann Glacier, Nioghalvfjerdsfjorden and Zachariæ Isstrøm. These data provide a new high temporal resolution record of each glacier’s evolution since 2014, and resolve recent seasonal and inter-annual changes in Greenland outlet glacier speed with an estimated certainty of 10 %. We find that since 2012, Jakobshavn Isbræ has been decelerating, and now flows approximately 1250 m yr−1 (10 %) slower than 5 years previously, thus reversing an increasing trend in ice velocity that has persisted during the last decade. Despite this, we show that seasonal variability in ice velocity remains significant; up to 750 m yr−1 (14 %) at a distance of 12 km inland of the terminus. We also use our new dataset to demonstrate a strong relationship between ice front position and ice flow at Jakobshavn Isbræ, with increases in speed of ~ 1800 m yr−1 in response to 1 km of retreat. Elsewhere, we record significant seasonal changes in flow of up to 25 % and 18 % at Petermann Glacier and Zachariæ Isstrøm, respectively. This study provides a first demonstration of the capacity of a new era of operational radar satellites to provide frequent, and timely, monitoring of ice sheet flow, and to better resolve the timescales over which glacier dynamics evolve.
Citation: Lemos, A., Shepherd, A., McMillan, M., Hogg, A. E., Hatton, E., and Joughin, I.: Ice velocity of Jakobshavn Isbræ, Petermann Glacier, Nioghalvfjerdsfjorden and Zachariæ Isstrøm, 2015–2017, from Sentinel 1-a/b SAR imagery, The Cryosphere Discuss., https://doi.org/10.5194/tc-2017-251, in review, 2018.
Adriano Lemos et al.
Adriano Lemos et al.
Adriano Lemos et al.

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Short summary
We present time-series of ice surface velocities on 4 key outlet glaciers in Greenland, derived from sequential satellite imagery acquired between October 2014 and February 2017. We demonstrate it is possible to resolve seasonal and inter-annual changes in outlet glacier with an estimated certainty of 10 %. These datasets are key for the timely identification of emerging signals of dynamic imbalance, and for understanding the processes driving ice velocity change.
We present time-series of ice surface velocities on 4 key outlet glaciers in Greenland, derived...
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