Surface elevation changes during 2007–13 on Bowdoin and Tugto Glaciers, northwestern Greenland

Shun Tsutaki,Daiki Sakakibara,Shin Sugiyama,Takanobu Sawagaki

doi:10.1017/jog.2016.106

Abstract

ABSTRACTTo quantify recent thinning of marine-terminating outlet glaciers in northwestern Greenland, we carried out field and satellite observations near the terminus of Bowdoin Glacier. These data were used to compute the change in surface elevation from 2007 to 2013 and this rate of thinning was then compared with that of the adjacent land-terminating Tugto Glacier. Comparing DEMs of 2007 and 2010 shows that Bowdoin Glacier is thinning more rapidly (4.1 ± 0.3 m a−1) than Tugto Glacier (2.8 ± 0.3 m a−1). The observed negative surface mass-balance accounts for <40% of the elevation change of Bowdoin Glacier, meaning that the thinning of Bowdoin Glacier cannot be attributable to surface melting alone. The ice speed of Bowdoin Glacier increases down-glacier, reaching 457 m a−1 near the calving front. This flow regime causes longitudinal stretching and vertical compression at a rate of −0.04 a−1. It is likely that this dynamically-controlled thinning has been enhanced by the acceleration of the glacier since 2000. Our measurements indicate that ice dynamics indeed play a predominant role in the rapid thinning of Bowdoin Glacier.

Highlights

The Greenland ice sheet (GrIS) is losing mass from increased surface melting and ice discharge from marine-terminating outlet glaciers (e.g. Sasgen and others, 2012; Andersen and others, 2015)
At Bowdoin Glacier, decrease in surface elevation is most significant within an area 8 km from the terminus (−8 to −2 m a−1) and the mean rate within 10 km from the terminus was −4.1 ± 0.3 m a−1
The change was small in the eastern tributary and the upper reaches of Bowdoin Glacier, where the rate of change was within the range of −4 to 0 m a−1

Summary

Introduction

The Greenland ice sheet (GrIS) is losing mass from increased surface melting and ice discharge from marine-terminating outlet glaciers (e.g. Sasgen and others, 2012; Andersen and others, 2015). Dynamic thinning accounted for ∼80% of the total ice mass loss from Upernavik Isstrøm in western Greenland over the period spanning 1985–2010 (Khan and others, 2013). The contribution of surface melting to the mass loss from GrIS outlet glaciers is increasing as a result of recent atmospheric warming trends. Van As (2011) reported that surface melting on Upernavik Isstrøm has roughly doubled since the 1980s under the influence of atmospheric warming. It is important to accurately quantify dynamic thinning and negative surface mass balance (SMB) in order to evaluate ongoing as well as future mass loss of marine-terminating outlet glaciers in Greenland. The contributions of these two processes to glacier thinning are poorly understood for the majority of the rapidly changing glaciers (Howat and others, 2007; van den Broeke and others, 2009)

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