Glacial cycles simulation of the Antarctic Ice Sheet
with PISM – Part 1: Boundary conditions and climatic
forcing

Albrecht, Torsten; Winkelmann, Ricarda; Levermann, Anders

doi:10.5194/tc-2019-71

Cited by 7 publications

(17 citation statements)

References 83 publications

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“…When used to drive ice sheet models, these climate anomalies are not sufficient to remove the floating ice shelves that buttress ice flow from central Antarctica (20). In an attempt to bypass these problems, ice sheet models have been driven by a wide range of prescribed climate scenarios; however, these suggest widely different sensitivities dependent on model physics and parameterization (21,22), with >2°C (and in some instances >4°C) ocean warming required for the loss of the WAIS, exceeding paleoclimate estimates (3,9,20,23) and different sensitivities of Antarctic ice sheet sectors (18,24,25).…”

mentioning

confidence: 99%

Early Last Interglacial ocean warming drove substantial ice mass loss from Antarctica

Turney¹,

Fogwill²,

Golledge³

et al. 2018

Preprint

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The future response of the Antarctic ice sheets to rising temperatures remains highly uncertain. A valuable analogue for assessing the sensitivity of Antarctica to warming is the Last Interglacial (129-116 kyr), when global sea level peaked 6 to 9 meters above present. Here we report a blue-ice record of ice-sheet and environmental change from the periphery of the marine-based West Antarctic Ice Sheet (WAIS). Constrained by a widespread volcanic horizon and supported by ancient microbial DNA analyses, we provide the first direct evidence for Last Interglacial WAIS collapse, driven by ocean warming and associated with destabilization of sub-glacial hydrates. Ice-sheet modelling supports this interpretation and suggests a 2˚C warming of the Southern Ocean over a millennia could trigger a ~3.2 meter rise in global sea levels. Our data indicate Antarctica is highly vulnerable to projected increases in ocean temperatures and may drive ice-climate feedbacks that further amplify warming.

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mentioning

confidence: 99%

Early Last Interglacial ocean warming drove substantial ice mass loss from Antarctica

Turney¹,

Fogwill²,

Golledge³

et al. 2018

Preprint

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“…Yelmo does not explicitly model the impact of ice anisotropy on the ice flow, so the classical "enhancement factor" are used as a tuning parameter (Ma et al, 2010;Pollard and DeConto, 2012;Maris et al, 2014;Albrecht et al, 2019). For this study we found realistic PD states for E grounded =1.0 and for ice shelves E floating =0.7.…”

Section: Methods and Experimental Setupmentioning

confidence: 77%

“…This parameterisation captures the phenomenon by which the occurrence of sliding (and its intensity) is favoured at low bedrock elevations and specifically within the marine sectors of ice sheets. It follows a similar approach as in Albrecht et al (2019) and Martin et al (2011), where the bedrock friction (in their case the "till friction angle") depends on the bedrock elevation.…”

Section: Basal-drag Lawmentioning

confidence: 99%

“…Ice-sheet models thus use friction formulations that can range from linear viscous and regularized Coulomb friction laws, typical of hard bedrock sliding (Larour et al, 2012;Pattyn et al, 2013;Joughin et al, 2019) to Coulomb-plastic deformation, characteristic of ice flow over a soft bedrock with filled cavities (Schoof, 2005(Schoof, , 2006Nowicki et al, 2013). In the simplest cases a constant friction coefficient is prescribed over the whole domain (Golledge et al, 2012), but generally this parameter incorporates the dependency of basal friction on the effective pressure exerted by the ice, as well as on bedrock characteristics by making use of assumed till properties (Winkelmann et al, 2011;Albrecht et al, 2019;Sutter et al, 2019) or basal temperature conditions (Pattyn, 2017;Quiquet et al, 2018). The sensitivity of the simulated ice volume to these features is substantial.…”

Section: Introductionmentioning

confidence: 99%

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Exploring the impact of atmospheric forcing and basal boundary conditions on the simulation of the Antarctic ice sheet at the Last Glacial Maximum

Blasco

Álvarez-Solas

Robinson

et al. 2020

Preprint

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Abstract. Little is known about the distribution of ice in the Antarctic ice sheet (AIS) during the Last Glacial Maximum (LGM). Whereas marine and terrestrial geological data indicate that the grounded ice advanced to a position close to the continental-shelf break, the total ice volume is unclear. Glacial boundary conditions are potentially important sources of uncertainty, in particular basal friction and climatic boundary conditions. Basal friction exerts a strong control on the large-scale dynamics of the ice sheet and thus affects its size, and is not well constrained. Glacial climatic boundary conditions determine the net accumulation and ice temperature, and are also poorly known. Here we explore the effect of the uncertainty in both features on the total simulated ice storage of the AIS at the LGM. For this purpose we use a hybrid ice-sheet-shelf model that is forced with different basal-drag choices and glacial background climatic conditions obtained from the LGM ensemble climate simulations of the third phase of the Paleoclimate Modelling Intercomparison Project (PMIP3). For a wide range of plausible basal friction configurations, the simulated ice dynamics vary widely but all simulations produce fully extended ice sheets towards the continental-shelf break. More dynamically active ice sheets correspond to lower ice volumes, while they remain consistent with the available constraints on ice extent. Thus, this work points to the possibility of an AIS with very active ice streams during the LGM. In addition, we find that the surface boundary temperature field plays a crucial role in determining the ice extent through its effect on viscosity. For ice sheets of a similar extent and comparable dynamics, we find that the precipitation field determines the total AIS volume. However, precipitation is deeply uncertain. Climatic fields simulated by climate models show more precipitation in coastal regions than a spatially uniform anomaly, which can lead to larger ice volumes. We strongly support using these paleoclimatic fields to simulate and study the LGM and potentially other time periods like the Last Interglacial. However, their accuracy must be assessed as well, as differences between climate model forcing lead to a range in the simulated ice volume and extension of about 6 m sea-level equivalent and one million km2.

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“…We have first applied a typical glacial-interglacial experiment (e.g. Golledge et al, 2014;Pollard et al, 2016;Albrecht et al, 2019) over the last 120 kyr (Figure 3a) with the prescribed external sea-level change (based on sea-level reconstructions by Bintanja et al (2008) and Lambeck et al (2014)) as a dominant forcing. Atmospheric forcing is produced 10 by perturbing present-day surface temperatures (RACMO2, Van Wessem et al, 2014) with a spatially constant temperature anomaly following ice-core reconstructions from EPICA Dome C (Jouzel et al, 2007), while correcting surface temperatures for elevation changes (e.g.…”

Section: Externally Forced Sea-level Variationsmentioning

confidence: 99%

Brief communication: On calculating the sea-level contribution in marine ice-sheet models

Goelzer¹,

Coulon²,

Pattyn³

et al. 2019

Preprint

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Abstract. Estimating the contribution of marine ice sheets to sea-level rise is complicated by ice grounded below sea level that is replaced by ocean water when melted. The common approach is to only consider the ice volume above flotation, defined as the volume of ice to be removed from an ice column to become afloat. With isostatic adjustment of the bedrock and external sea-level forcing, this approach breaks down, because ice volume above flotation can be modified without actual changes of the sea-level contribution. We discuss a consistent and generalised approach for estimating the sea-level contribution from marine ice sheets.

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Glacial cycles simulation of the Antarctic Ice Sheet with PISM – Part 1: Boundary conditions and climatic forcing

Cited by 7 publications

References 83 publications

Early Last Interglacial ocean warming drove substantial ice mass loss from Antarctica

Early Last Interglacial ocean warming drove substantial ice mass loss from Antarctica

Exploring the impact of atmospheric forcing and basal boundary conditions on the simulation of the Antarctic ice sheet at the Last Glacial Maximum

Brief communication: On calculating the sea-level contribution in marine ice-sheet models

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