Exceptional Retreat of Kangerlussuaq Glacier, East Greenland, Between 2016 and 2018

Stephen Brough,James M Lea,J Rachel Carr,Neil Ross

doi:10.3389/feart.2019.00123

Stephen Brough, James M Lea + Show 2 more

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https://doi.org/10.3389/feart.2019.00123

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Abstract

Kangerlussuaq Glacier is one of Greenland’s largest tidewater outlet glaciers, accounting for approximately 5% of all ice discharge from the Greenland ice sheet. In 2018 the Kangerlussuaq ice front reached its most retreated position since observations began in 1932. We determine the relationship between retreat and: (i) ice velocity; and (ii) surface elevation change, to assess the impact of the retreat on the glacier trunk. Between 2016 and 2018 the glacier retreated ∼5 km and brought the Kangerlussuaq ice front into a major (∼15 km long) overdeepening. Coincident with this retreat, the glacier thinned as a result of near-terminus acceleration in ice flow. The subglacial topography means that 2016–2018 terminus recession is likely to trigger a series of feedbacks between retreat, thinning, and glacier acceleration, leading to a rapid and high-magnitude increase in discharge and sea level rise contribution. Dynamic thinning may continue until the glacier reaches the upward sloping bed ∼10 km inland of its current position. Incorporating these non-linear processes into prognostic models of the ice sheet to 2100 and beyond will be critical for accurate forecasting of the ice sheet’s contribution to sea level rise.

Highlights

The Greenland ice sheet is a major source of global sea level rise and contributed 171 Gt a−1 (∼0.47 ± 0.23 mm a−1) to sea level rise between 1991 and 2015
40% of Greenland’s mass loss since 1991 was due to increased ice discharge from marine-terminating outlet glaciers and it accounted for ∼60% of ice loss during the phase of rapid outlet glacier retreat observed between 2000 and 2005 (Rignot and Kanagaratnam, 2006; Enderlin et al, 2014; Andersen et al, 2015; van den Broeke et al, 2016)
Terminus positions of Kangerlussuaq were manually digitized from all available Level 1T pansharpened (15 m) Landsat 8 Operational Land Imager (OLI) satellite imagery between 2013 and 2018 using the Google Earth Digitisation Tool (GEEDiT) (Lea, 2018)

Summary

Introduction

The Greenland ice sheet is a major source of global sea level rise and contributed 171 Gt a−1 (∼0.47 ± 0.23 mm a−1) to sea level rise between 1991 and 2015 (van den Broeke et al, 2016). 40% of Greenland’s mass loss since 1991 was due to increased ice discharge from marine-terminating outlet glaciers and it accounted for ∼60% of ice loss during the phase of rapid outlet glacier retreat observed between 2000 and 2005 (Rignot and Kanagaratnam, 2006; Enderlin et al, 2014; Andersen et al, 2015; van den Broeke et al, 2016). Predictions of ice discharge from Greenland’s marine-terminating outlet glaciers are critical for forecasting near-future sea level rise. Despite their importance, substantial uncertainty remains over the response of Greenland’s outlet glacier to climatic and oceanic warming (e.g., Carr et al, 2013; Enderlin et al, 2013; Stocker et al, 2013). This response is complicated by glacier-specific factors, the bed and fjord geometry, which can strongly enhance/suppress glacier response to forcing (e.g., Moon et al, 2012; Carr et al, 2015)

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