Final published version
Licence: CC BY: Creative Commons Attribution 4.0 International License
Research output: Contribution to Journal/Magazine › Journal article › peer-review
<mark>Journal publication date</mark> | 18/06/2018 |
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<mark>Journal</mark> | Cryosphere |
Issue number | 6 |
Volume | 12 |
Number of pages | 11 |
Pages (from-to) | 2087-2097 |
Publication Status | Published |
<mark>Original language</mark> | English |
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 four key outlet glaciers in Greenland: Jakobshavn Isbræ, Petermann Glacier, Nioghalvfjerdsfjorden, and Zachariæ Isstrøm. These data provide a new high temporal resolution record (6-day averaged solutions) of each glacier's evolution since 2014, and resolve recent seasonal speedup periods 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 1250g 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 750g yr-1 (14%) at a distance of 12 km inland of the terminus. We also use our new dataset to estimate the duration of speedup periods (80-95 days) and to demonstrate a strong relationship between ice front position and ice flow at Jakobshavn Isbræ, with increases in speed of 1800g yr-1 in response to 1 km of retreat. Elsewhere, we record significant seasonal changes in flow of up to 25% (2015) and 18% (2016) 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.