Seasonal ice-speed variations in 10 marine-terminating outlet glaciers along the coast of Prudhoe Land, northwestern Greenland

Daiki Sakakibara,Shin Sugiyama

doi:10.1017/jog.2019.81

Abstract

AbstractWe present a 3-year record of seasonal variations in ice speed and frontal ablation of 10 marine-terminating outlet glaciers along the coast of Prudhoe Land in northwestern Greenland. The glaciers showed seasonal speedup initiated between late May and early June, and terminated between late June and early July. Ice speed subsequently decreased from July to September. The timing of the speedup coincided with the onset of the air temperature rise to above freezing, suggesting an influence of meltwater availability on the glacier dynamics. No clear relationship was found between the speedup and the terminus position or the sea-ice/ice-mélange conditions. These results suggest that the meltwater input to the glacier bed triggered the summer speedup. The excess of summer speed (June–August) over the mean for the rest of the year accounted for 0.5–13% of the annual ice motion. Several glaciers showed seasonal frontal variations, i.e. retreat in summer and advance in winter. This was not due to ice-speed variations, but was driven by seasonal variations in frontal ablation. The results demonstrate the dominant effect of glacier surface melting on the seasonal speedup, and the importance of seasonal speed patterns on longer-term ice motion of marine-terminating outlet glaciers in Greenland.

Highlights

Mass loss from the Greenland ice sheet has contributed to global sea level rise at a mean rate of 0.47 mm a−1 during the period from 1991 to 2015
Since ∼40% of the mass loss was due to changes in ice discharge from marine-terminating outlet glaciers, a future projection of ice discharge from the Greenland ice sheet is crucial for understanding the magnitude and timing of global sea level rise
We studied ice-speed variations of 10 marine-terminating outlet glaciers along the coast of Prudhoe Land in northwestern Greenland

Summary

Introduction

Mass loss from the Greenland ice sheet has contributed to global sea level rise at a mean rate of 0.47 mm a−1 during the period from 1991 to 2015 (van den Broeke and others, 2016). Since ∼40% of the mass loss was due to changes in ice discharge from marine-terminating outlet glaciers (van den Broeke and others, 2016), a future projection of ice discharge from the Greenland ice sheet is crucial for understanding the magnitude and timing of global sea level rise. Recent progress in satellite remote sensing techniques contributes to the studies of seasonal speed patterns of marine-terminating glaciers in Greenland (Howat and others, 2010; Moon and others, 2014, 2015; Vijay and others, 2019). Sole and others (2011) reported the ∼1% contribution of summer speedup to annual ice motion of a marine-terminating outlet glacier in southwest Greenland. As the study site was far inland from the glacier terminus at >1200 m a.s.l., the importance of summer speedup to glacier dynamics in the vicinity of the terminus remains poorly understood

Results

Discussion

Conclusion