Ice-sheet mass balance and climate change

Abstract

'Ice-sheet mass balance and climate change. ', Nature., 498 (7452). pp. 51-59. Further information on publisher's website:http://dx.doi.org/10.1038/nature12238Publisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Greenland is losing mass at an increasing pace, Antarctic loss is likely to be less than some 52 recently-published estimates. It remains unclear whether East Antarctica has been gaining 53 or losing mass over the last twenty years, and uncertainties in mass change for West 54Antarctica and the Antarctic Peninsula remain large. We highlight the last six years of 55 progress and examine the key problems that remain. (primarily snow accumulation) and mass losses (primarily melt-water runoff and solid ice 74 dynamical discharge across the grounding line). Surface mass balance (SMB) is the net 75 balance of mass gains and losses at the ice-sheet surface and does not include dynamical 76 mass loss. Efforts to determine ice-sheet mass balance using the three satellite geodetic 77 techniques of altimetry, interferometry, and gravimetry (see Section 2.1) have recently 78 been sharpened by carefully defining common spatial and temporal domains for inter-79 comparison 2 . Here we review the latest mass balance estimates for the Antarctic (AIS) and 80Greenland (GrIS) ice sheets. New glacial isostatic adjustment (GIA) models, tested and 81 evaluated against Global Positioning System (GPS) data, have recently led to significant 82 downwards revision in GIA, and hence downwards revisions of gravimetric and altimetric 83 satellite estimates of Antarctic mass loss 2 (Box 1). 84Since IPCC AR4, ice-sheet models are no longer constrained to using overly 85 simplified physics, allowing them to more accurately simulate the important coupling 86 between ice sheets, ice streams and ice shelves. This major advance has been accompanied 87 by improved model representation of the complex interactions of the ice-sheet with its bed, 88 the atmosphere and the ocean. For completeness we also discuss briefly the contributions 89 to sea-level rise (SLR) from other sources, namely glaciers and ice caps, thermal expansion 90 of the oceans and terrestrial water storage changes. Similarly, GRACE and radar and laser altimetry studies require the effects of GIA-121 related vertical bedrock motion (Box 1) to be accurately removed. Such vertical motion 122 could be misinterpreted as ice-mass change by the GRACE satellites or ice-thickness change 123 by radar and laser altimeters, and a GIA correction m...

Sedimentary and structural evolution of a relict subglacial to subaerial drainage system and its hydrogeological implications: an example from Anglesey, north Wales, UK

“…Understanding the behaviour of subglacial meltwater systems is crucial because of their influence upon substrate rheology and ice-bed coupling (Boulton & Hindmarsh, 1987;Iverson et al, 1995;Boulton, 1996;Piotrowski et al, 2004Piotrowski et al, , 2006Evans et al, 2006;Kjaer et al, 2006;Lee & Phillips, 2008;Boulton et al, 2009), and in-turn, glacier dynamics that operate over a range of temporal and spatial scales (Kamb, 1987;Bartholomew et al, 2010;Sundal et al, 2011;Robel et al, 2013). Research now recognises that these processes act to drive the expansion, break-up and collapse of major ice streams and ice masses (MacAyeal, 1993;Clark, 1994;Tulaczyk et al, 2000;Bell et al, 2007;Stokes et al, 2007;Burke et al, 2012) thus linking subglacial drainage to collapsing ice masses, sea-level change and abrupt climate change (Goezler et al, 2011;King et al, 2012;Hanna et al, 2013;Fürst et al, 2014 and references therein). Indeed, subglacial meltwater systems underpin major global issues surrounding the stability of the modern Antarctic and Greenland ice sheets, their sensitivity too and influence on current and future changes in sea-level and climate (Alley et al, 2005;Zwally et al, 2005;Shepherd & Wingham, 2007;Pfeffer et al, 2008).…”

An ETKF approach for initial state and parameter estimation in ice sheet modelling

“…Good estimates of their future contribution are therefore crucial to producing sea-level change forecasts, as underlined by Hanna et al (2013). Producing pertinent estimates of polar ice sheet contribution to sea-level change relies on our ability to run a precisely calibrated ice sheet evolution model starting from a reliable initial state.…”

“…The Best Linear Unbiased Estimation (BLUE) and Optimal Interpolation (OI) methods were introduced by Arthern (2003) and Berliner et al (2008). The Robin inverse method due to Chaabane and Jaoua (1999) has been introduced by Arthern and Gudmundsson (2010) for ice sheet models, and finally, Heimbach and Bugnion (2009) presented the first adjoint ice sheet model derived automatically.…”

The sensitivity of the Greenland Ice Sheet to glacial–interglacial oceanic forcing

“…The complex mechanisms that lead to ice-shelf thinning, loss of buttressing and potential grounding-line instability have been studied largely for the Antarctic Ice Sheet (AIS) (DeConto and Pollard, 2016;Favier et al, 2014;Hanna et al, 2013;Joughin et al, 2014a;Pritchard et al, 2012;Rignot et al, 2004;Shepherd et al, 2004;Wouters et al, 2015). The thinning of the Larsen C ice shelf and its recent calving event (Hogg and Gudmundsson, 2017;Jansen et al, 2015), the collapse of Larsen B and the melting of the Antarctic Peninsula glaciers (Cook et al, 2016), the widespread retreat of Pine Island and other glaciers in West Antarctica (Alley et al, 2015;Joughin et al, 2014b;Rignot et al, 2014) and the thinning of some East Antarctica ice shelves are notable examples of the direct connection between changes in oceanic forcing and glacier-termini adjustment (Alley et al, 2015).…”