Inland advance of supraglacial lakes in north-west Greenland under recent climatic warming

Laura A Gledhill,Andrew G Williamson

doi:10.1017/aog.2017.31

Abstract

ABSTRACTThe inland advance of supraglacial lakes (SGLs) towards the interior regions of the Greenland ice sheet (GrIS) may have implications for the water volumes reaching the subglacial drainage system, and could consequently affect long-term ice-sheet dynamics. Here, we investigate changes to the areas, volumes and elevation distributions of over 8000 manually delineated SGLs using 44 Landsat images of a 6200 km2 sector of north-west Greenland over three decades (1985–2016). Our results show that SGLs have advanced to higher maximum (+418 m) and mean (+299 m) elevations, and that there has been a near-doubling of total regional SGL areas and volumes over the study period, accelerating after 2000. These changes were primarily caused by an increased SGL area and volume at high (≥1200 m a.s.l.) elevations, where SGL coverage increased by over 2750% during the study period. Many of the observed changes, particularly the post-2000 accelerations, were driven by changes to regional surface-temperature anomalies. This study demonstrates the past and accelerating response of the GrIS's hydrological system due to climatic warming, indicating an urgent need to understand whether the increasingly inland SGLs will be capable of hydrofracture in the future, thus determining their potential implications for ice-sheet dynamics.

Highlights

AND AIMSGiven the ongoing and accelerating mass loss from the Greenland ice sheet (GrIS) and its contribution to global sea levels (Church and others, 2013; Vaughan and others, 2013; Enderlin and others, 2014), a growing body of research seeks to explore the drivers of this mass loss
Our analysis showed that surface temperature changes explained ∼40% of the variance in maximum Supraglacial lakes (SGLs) elevations (Fig. 6a), likely because higher surface temperatures promote increased surface melting across greater portions of the GrIS (Howat and others, 2013)
The total regional SGL area and volume nearly doubled over the study period, again with large accelerations post-2000, which were driven by increases to the SGL area and volume at high (≥1200 m a.s.l.) surface elevations

Summary

Introduction

AND AIMSGiven the ongoing and accelerating mass loss from the Greenland ice sheet (GrIS) and its contribution to global sea levels (Church and others, 2013; Vaughan and others, 2013; Enderlin and others, 2014), a growing body of research seeks to explore the drivers of this mass loss. Supraglacial lakes (SGLs) traditionally form annually within ice-surface topographic depressions (Echelmeyer and others, 1991) within the GrIS’s ablation zone, and are known to influence the loss in three ways. ∼13% of SGLs (Selmes and others, 2011) drain in situ by hydrofracture in as little as 2 h and commonly in under 24 h These rapid SGL drainage events deliver huge meltwater pulses to the ice-sheet bed, which can overwhelm the subglacial drainage system, drive down effective pressure, promote ice-bed decoupling and cause transient (hourly–weekly) ice speedups of up to 220% of background winter velocities (Das and others, 2008; Bartholomew and others, 2010; Banwell and others, 2013, 2016; Doyle and others, 2013; Tedesco and others, 2013). The opening of fractures during rapid SGL drainage results in surface meltwater reaching the colder ice within the ice-sheet body, heating it and promoting faster ice-deformation rates over long times (Phillips and others, 2010, 2013)

Results

Discussion

Conclusion