08 Sep 2022
08 Sep 2022
Status: this preprint is currently under review for the journal TC.

Weekly to monthly terminus variability of Greenland’s marine-terminating outlet glaciers

Taryn E. Black1,2 and Ian Joughin2 Taryn E. Black and Ian Joughin
  • 1Department of Earth and Space Sciences, University of Washington, Seattle, WA, 98195, USA
  • 2Polar Science Center, Applied Physics Laboratory, Seattle, WA, 98105, USA

Abstract. Earlier studies have shown that seasonal terminus-position variability is superimposed on multi-decadal trends of glacier retreat. To characterize this seasonal variability, we manually digitized terminus positions for 219 marine-terminating glaciers in Greenland from January 2015 through December 2021 using Sentinel-1 SAR mosaics. We digitized at a monthly frequency for 199 glaciers and at a six-day frequency for 20 glaciers. We found that nearly 75 % of glacier termini in Greenland vary significantly on a seasonal basis. For these seasonally-varying glaciers, on average, seasonal retreat typically begins in mid-May, and seasonal advance generally commences in early October. The timing of the initiation of the retreat period may be related to the timing of the onset of ice-sheet surface melt. The rate of retreat events peaks in late summer and reaches a minimum in late winter and early spring. The median magnitude of terminus-position seasonality, the difference between glacier length at the dates of peak advance and retreat, is about 220 m. We find a stronger correlation between this magnitude and glacier velocity than between magnitude and glacier width. Terminus-position seasonality can influence longer-term glacier dynamics and, consequently, ice-sheet mass balance. This study contributes to our understanding of terminus-position seasonality for individual glaciers and collectively for glaciers around the entire Greenland Ice Sheet.

Taryn E. Black and Ian Joughin

Status: open (until 03 Nov 2022)

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Taryn E. Black and Ian Joughin

Taryn E. Black and Ian Joughin


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Short summary
The frontal positions of most ice sheet-based glaciers in Greenland vary seasonally. On average, these glaciers begin retreating in May and begin advancing in October, and the difference between their most advanced and most retreated positions is 220 m. The timing may be related to the timing of melt on the ice sheet, and the seasonal length variation may be related to glacier speed. These seasonal variations can affect glacier behavior, and consequently, how much ice is lost from the ice sheet.