Abstract
AbstractGreenland's future contribution to sea-level rise is strongly dependent on the extent to which dynamic perturbations, originating at the margin, can drive increased ice flow within the ice-sheet interior. However, reported observations of ice dynamical change at distances >~50 km from the margin have a very low spatial and temporal resolution. Consequently, the likely response of the ice-sheet's interior to future oceanic and atmospheric warming is poorly constrained. Through combining GPS and satellite-image-derived ice velocity measurements, we measure multi-decadal (1993–1997 to 2014–2018) velocity change at 45 inland sites, encompassing all regions of the ice sheet. We observe an almost ubiquitous acceleration inland of tidewater glaciers in west Greenland, consistent with acceleration and retreat at glacier termini, suggesting that terminus perturbations have propagated considerable distances (>100 km) inland. In contrast, outside of Kangerlussuaq, we observe no acceleration inland of tidewater glaciers in east Greenland despite terminus retreat and near-terminus acceleration, and suggest propagation may be limited by the influence of basal topography and ice geometry. This pattern of inland dynamical change indicates that Greenland's future contribution to sea-level will be spatially complex and will depend on the capacity for dynamic changes at individual outlet glacier termini to propagate inland.
Highlights
The Greenland Ice Sheet (GrIS) has lost mass to the ocean at an increasing rate over recent decades (Rignot and others, 2008, 2011; Shepherd and others, 2012, 2020; Enderlin and others, 2014; King and others, 2018; Mouginot and others, 2019), and has the largest contribution to global sea-level rise of any individual ice body (Vaughan and others, 2013; Bamber and others, 2018)
The complexity within the observed pattern of inland change likely reflects a range of controls, including the speed at which a perturbation can propagate inland, and the influence of ice geometry and basal topography in facilitating or limiting the extent to which a perturbation can propagate up-glacier
These findings are of great importance with regards to Greenland’s future contribution to global sea-level rise, as they indicate that ice acceleration at many tidewater glaciers has the potential to propagate considerable distances into the ice-sheet interior, accelerating the draw-down of greater volumes of thicker ice towards the margins, accelerating mass loss
Summary
The Greenland Ice Sheet (GrIS) has lost mass to the ocean at an increasing rate over recent decades (Rignot and others, 2008, 2011; Shepherd and others, 2012, 2020; Enderlin and others, 2014; King and others, 2018; Mouginot and others, 2019), and has the largest contribution to global sea-level rise of any individual ice body (Vaughan and others, 2013; Bamber and others, 2018). While the impacts of variable hydrological forcing on ice flow have been well-studied near the ice margin (van de Wal and others, 2008, 2015; Bartholomew and others, 2010; Sole and others, 2013; Tedstone and others, 2015), it remains unclear whether meltwater can access the bed, and efficient subglacial channels form, further into the ice-sheet interior where the ice is thicker and rates of surface melting are lower (Nienow and others, 2017) This is important given that as the ELA rises in response to projected increases in surface melt (Hanna and others, 2008), the area of the ice-sheet surface undergoing melt will increase exponentially due to the hypsometry of the ice-sheet surface (Bartholomew and others, 2011; Machguth and others, 2016). Considering conservation of mass, the thickness of ice in the interior is considerably greater than that at the margin, and so any increase in ice motion has the potential to result in a much larger increase in mass flux when compared to marginal regions (Doyle and others, 2014), for marine-terminating margins which are characterised by faster flow velocities and can Downloaded from https://www.cambridge.org/core. 02 Nov 2021 at 11:01:35, subject to the Cambridge Core terms of use
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