Slowdown in Antarctic mass loss from solid Earth and sea-level feedbacks

Science ◽  
2019 ◽  
Vol 364 (6444) ◽  
pp. eaav7908 ◽  
Author(s):  
E. Larour ◽  
H. Seroussi ◽  
S. Adhikari ◽  
E. Ivins ◽  
L. Caron ◽  
...  
Keyword(s):  
Solid Earth ◽  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
West Antarctica ◽  
Spatiotemporal Resolution ◽  
Amundsen Sea ◽  
Polar Ice Sheets ◽  
Short Time ◽  
The Impact

Geodetic investigations of crustal motions in the Amundsen Sea sector of West Antarctica and models of ice-sheet evolution in the past 10,000 years have recently highlighted the stabilizing role of solid-Earth uplift on polar ice sheets. One critical aspect, however, that has not been assessed is the impact of short-wavelength uplift generated by the solid-Earth response to unloading over short time scales close to ice-sheet grounding lines (areas where the ice becomes afloat). Here, we present a new global simulation of Antarctic evolution at high spatiotemporal resolution that captures all solid Earth processes that affect ice sheets and show a projected negative feedback in grounding line migration of 38% for Thwaites Glacier 350 years in the future, or 26.8% reduction in corresponding sea-level contribution.

scholarly journals Last Interglacial climate and sea-level evolution from a coupled ice sheet–climate model

2016 ◽  
Vol 12 (12) ◽  
pp. 2195-2213 ◽  
Author(s):  
Heiko Goelzer ◽  
Philippe Huybrechts ◽  
Marie-France Loutre ◽  
Thierry Fichefet
Keyword(s):  
Surface Temperature ◽  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Last Interglacial ◽  
A Minor ◽  
The Antarctic ◽  
The Impact ◽  
And Sea Level

Abstract. As the most recent warm period in Earth's history with a sea-level stand higher than present, the Last Interglacial (LIG,  ∼  130 to 115 kyr BP) is often considered a prime example to study the impact of a warmer climate on the two polar ice sheets remaining today. Here we simulate the Last Interglacial climate, ice sheet, and sea-level evolution with the Earth system model of intermediate complexity LOVECLIM v.1.3, which includes dynamic and fully coupled components representing the atmosphere, the ocean and sea ice, the terrestrial biosphere, and the Greenland and Antarctic ice sheets. In this setup, sea-level evolution and climate–ice sheet interactions are modelled in a consistent framework.Surface mass balance change governed by changes in surface meltwater runoff is the dominant forcing for the Greenland ice sheet, which shows a peak sea-level contribution of 1.4 m at 123 kyr BP in the reference experiment. Our results indicate that ice sheet–climate feedbacks play an important role to amplify climate and sea-level changes in the Northern Hemisphere. The sensitivity of the Greenland ice sheet to surface temperature changes considerably increases when interactive albedo changes are considered. Southern Hemisphere polar and sub-polar ocean warming is limited throughout the Last Interglacial, and surface and sub-shelf melting exerts only a minor control on the Antarctic sea-level contribution with a peak of 4.4 m at 125 kyr BP. Retreat of the Antarctic ice sheet at the onset of the LIG is mainly forced by rising sea level and to a lesser extent by reduced ice shelf viscosity as the surface temperature increases. Global sea level shows a peak of 5.3 m at 124.5 kyr BP, which includes a minor contribution of 0.35 m from oceanic thermal expansion. Neither the individual contributions nor the total modelled sea-level stand show fast multi-millennial timescale variations as indicated by some reconstructions.

ISMIP6 Future Projections for Antarctica performed using the AWI PISM ice sheet model

2020 ◽  
Author(s):  
Thomas Kleiner ◽  
Jeremie Schmiedel ◽  
Angelika Humbert
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Climate Models ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Initial State ◽  
Intercomparison Project ◽  
Non Local ◽  
The Impact

<p>Ice sheets constitute the largest and most uncertain potential source of future sea-level rise. The Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) brings together a consortium of international ice sheet and climate models to explore the contribution from the Greenland and Antarctic ice sheets to future sea-level rise.</p> <p>We use the Parallel Ice Sheet Model (PISM, pism-docs.org) to carry out spinup and projection simulations for the Antarctic Ice Sheet. Our treatment of the ice-ocean boundary condition previously based on 3D ocean temperatures (initMIP-Antarctica) has been adopted to use the ISMIP6 parameterisation and 3D ocean forcing fields (temperature and salinity) according to the ISMIP6 protocol.</p> <p>In this study, we analyse the impact of the choices made during the model initialisation procedure on the initial state. We present the AWI PISM results of the ISMIP6 projection simulations and investigate the ice sheet response for individual basins. In the analysis, we distinguish between the local and non-local ice shelf basal melt parameterisation.</p>

Recent developments in modeling ice sheet deformation

2020 ◽  
Author(s):  
Felicity McCormack ◽  
Roland Warner ◽  
Adam Treverrow ◽  
Helene Seroussi
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Vertical Shear ◽  
Shear Stresses ◽  
Polar Ice ◽  
Ice Flow ◽  
Polar Ice Sheets ◽  
Basal Shear ◽  
The Impact

<p>Viscous deformation is the main process controlling ice flow in ice shelves and in slow-moving regions of polar ice sheets where ice is frozen to the bed. However, the role of deformation in flow in ice streams and fast-flowing regions is typically poorly represented in ice sheet models due to a major limitation in the current standard flow relation used in most large-scale ice sheet models – the Glen flow relation – which does not capture the steady-state flow of anisotropic ice that prevails in polar ice sheets. Here, we highlight recent advances in modeling deformation in the Ice Sheet System Model using the ESTAR (empirical, scalar, tertiary, anisotropic regime) flow relation – a new description of deformation that takes into account the impact of different types of stresses on the deformation rate. We contrast the influence of the ESTAR and Glen flow relations on the role of deformation in the dynamics of Thwaites Glacier, West Antarctica, using diagnostic simulations. We find key differences in: (1) the slow-flowing interior of the catchment where the unenhanced Glen flow relation simulates unphysical basal sliding; (2) over the floating Thwaites Glacier Tongue where the ESTAR flow relation outperforms the Glen flow relation in accounting for tertiary creep and the spatial differences in deformation rates inherent to ice anisotropy; and (3) in the grounded region within 80km of the grounding line where the ESTAR flow relation locally predicts up to three times more vertical shear deformation than the unenhanced Glen flow relation, from a combination of enhanced vertical shear flow and differences in the distribution of basal shear stresses. More broadly on grounded ice, the membrane stresses are found to play a key role in the patterns in basal shear stresses and the balance between basal shear stresses and gravitational forces simulated by each of the ESTAR and Glen flow relations. Our results have implications for the suitability of ice flow relations used to constrain uncertainty in reconstructions and projections of global sea levels, warranting further investigation into using the ESTAR flow relation in transient simulations of glacier and ice sheet dynamics. We conclude by discussing how geophysical data might be used to provide insight into the relationship between ice flow processes as captured by the ESTAR flow relation and ice fabric anisotropy.</p>

scholarly journals Collapse of the West Antarctic Ice Sheet after local destabilization of the Amundsen Basin

2015 ◽  
Vol 112 (46) ◽  
pp. 14191-14196 ◽  
Author(s):  
Johannes Feldmann ◽  
Anders Levermann
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheet ◽  
Horizontal Resolution ◽  
West Antarctica ◽  
Amundsen Sea ◽  
Ice Dynamics ◽  
Antarctic Ice Sheet ◽  
Topographic Features ◽  
Global Sea Level

The future evolution of the Antarctic Ice Sheet represents the largest uncertainty in sea-level projections of this and upcoming centuries. Recently, satellite observations and high-resolution simulations have suggested the initiation of an ice-sheet instability in the Amundsen Sea sector of West Antarctica, caused by the last decades’ enhanced basal ice-shelf melting. Whether this localized destabilization will yield a full discharge of marine ice from West Antarctica, associated with a global sea-level rise of more than 3 m, or whether the ice loss is limited by ice dynamics and topographic features, is unclear. Here we show that in the Parallel Ice Sheet Model, a local destabilization causes a complete disintegration of the marine ice in West Antarctica. In our simulations, at 5-km horizontal resolution, the region disequilibrates after 60 y of currently observed melt rates. Thereafter, the marine ice-sheet instability fully unfolds and is not halted by topographic features. In fact, the ice loss in Amundsen Sea sector shifts the catchment's ice divide toward the Filchner–Ronne and Ross ice shelves, which initiates grounding-line retreat there. Our simulations suggest that if a destabilization of Amundsen Sea sector has indeed been initiated, Antarctica will irrevocably contribute at least 3 m to global sea-level rise during the coming centuries to millennia.

scholarly journals A mass conserving formalism for ice sheet, solid Earth and sea level interaction

2020 ◽  
Author(s):  
Surendra Adhikari ◽  
Erik R. Ivins ◽  
Eric Larour ◽  
Lambert Caron ◽  
Helene Seroussi
Keyword(s):  
Solid Earth ◽  
Sea Level ◽  
Ice Sheet ◽  
Geoid Height ◽  
Earth System ◽  
Ice Shelves ◽  
Ocean Mass ◽  
Polar Ice Sheets ◽  
Ice Sheet Dynamics ◽  
And Sea Level

Abstract. Polar ice sheets are important components of any Earth System model. As the domains of land, ocean, and ice sheet change, they must be consistently defined within the lexicon of geodesy. Understanding the interplay between the processes such as ice sheet dynamics, solid Earth deformation, and sea level adjustment requires both consistent and mass conserving descriptions of evolving land and ocean domains, grounded and floating ice masks, coastlines and grounding lines, and bedrock and geoid height as viewed from space. Here we present a geometric description of an evolving ice sheet margin and its relations to sea level change, the position and loading of the solid Earth and include the ice shelves and adjacent ocean mass. We generalize the formulation so that it is applied to arbitrarily distributed ice, bedrock and adjacent ocean, and their interactive evolution. The formalism simplifies computational strategies that seek to conserve mass in Earth System models.

scholarly journals Contrasting response of West and East Antarctic ice sheets to Glacial Isostatic Adjustment

2020 ◽  
Author(s):  
Violaine Coulon ◽  
Kevin Bulthuis ◽  
Sainan Sun ◽  
Konstanze Haubner ◽  
Frank Pattyn
Keyword(s):  
Solid Earth ◽  
Sea Level ◽  
Ice Sheet ◽  
East Antarctica ◽  
Climate Forcing ◽  
West Antarctica ◽  
Antarctic Ice Sheet ◽  
West Antarctic ◽  
Earth Structures ◽  
The Antarctic

<p>The Antarctic ice sheet (AIS) lies on a solid Earth that displays large spatial variations in rheological properties, with a thin lithosphere and low-viscosity upper mantle (weak Earth structure) beneath West Antarctica and an opposing structure beneath East Antarctica. This contrast is known to have a significant impact on ice-sheet grounding-line stability. Here, we embedded a modified glacial-isostatic ELRA model within an Antarctic ice sheet model that considers a weak Earth structure for West Antarctica supplemented with an approximation of gravitationally-consistent local sea-level changes. By taking advantage of the computational efficiency of this elementary GIA model, we assess in a probabilistic way the impact of uncertainties in the Antarctic viscoelastic properties on the response of the Antarctic ice sheet to future warming by using an ensemble of 2000 Monte Carlo simulations that span a range of plausible solid Earth structures for both West and East Antarctica. <br>We show that on multicentennial-to-millennial timescales, model projections that do not consider the dichotomy between East and West Antarctic solid Earth structures systematically overestimate the sea-level contribution from the Antarctic ice sheet because regional solid-Earth deformation plays a significant role in promoting the stability of the West Antarctic ice sheet (WAIS). However, WAIS collapse cannot be prevented under high-emissions climate scenarios. At longer timescales and under unabated climate forcing, future mass loss may be underestimated because in East Antarctica, GIA feedbacks have the potential to re-enforce the influence of the climate forcing as compared with a spatially-uniform GIA model. In this context, the AIS response might be an even larger source of uncertainty in projecting sea-level rise than previously thought, with the highest uncertainty arising from the East Antarctic ice sheet where the Aurora Basin is very GIA-dependent.</p>

scholarly journals Interdependence of the Northern Hemisphere ice-sheets build-up during the last glaciation: the role of atmospheric circulation

2013 ◽  
Vol 9 (2) ◽  
pp. 2183-2216
Author(s):  
P. Beghin ◽  
S. Charbit ◽  
C. Dumas ◽  
M. Kageyama ◽  
D. M. Roche ◽  
...  
Keyword(s):  
Sea Level ◽  
Atmospheric Circulation ◽  
Northern Hemisphere ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Stationary Waves ◽  
Sea Level Pressure ◽  
Orographic Effect ◽  
Level Pressure ◽  
The Impact

Abstract. The development of large continental-scale ice sheets over Canada and Northern Europe during the last glacial cycle likely modified the track of stationary waves and influenced the location of growing ice sheets through changes in accumulation and temperature patterns. Although they are often mentioned in the literature, these feedback mechanisms are poorly constrained and have never been studied throughout an entire glacial-interglacial cycle. Using the climate model of intermediate complexity CLIMBER-2 coupled with the 3-D ice-sheet model GRISLI, we investigate the impact of stationary waves on the construction of past Northern Hemisphere ice sheets during the past glaciation. The stationary waves are not explicitly computed in the model but their effect on sea-level pressure is parameterized. Several parameterizations have been tested allowing to study separately the effect of surface temperature (thermal forcing) and topography (orographic forcing) on sea-level pressure, and therefore on atmospheric circulation and ice-sheet surface mass balance. We show that the response of ice sheets to thermal and/or orographic forcings is rather different. At the beginning of the glaciation, the orographic effect favors the growth of the Laurentide ice sheet, whereas Fennoscandia appears rather sensitive to the thermal effect. Using the ablation parameterization as a trigger to artificially modify the size of one ice sheet, the remote influence of one ice sheet on the other is also studied as a function of the stationary wave parameterizations. The sensitivity of remote ice sheets is shown to be highly sensitive to the choice of these parameterizations with a larger response when orographic effect is accounted for. Results presented in this study suggest that the various spatial distributions of ice sheets could be partly be explained by the feedbacks mechanisms occurring between ice sheets and atmospheric circulation.

scholarly journals Rapid marine deglaciation: asynchronous retreat dynamics between the Irish Sea Ice Stream and terrestrial outlet glaciers

2013 ◽  
Vol 1 (1) ◽  
pp. 277-309
Author(s):  
H. Patton ◽  
A. Hubbard ◽  
T. Bradwell ◽  
N. F. Glasser ◽  
M. J. Hambrey ◽  
...  
Keyword(s):  
Sea Ice ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Irish Sea ◽  
Swath Bathymetry ◽  
Ice Stream ◽  
Non Linear ◽  
Polar Ice Sheets ◽  
The Irish Sea ◽  
Short Time

Abstract. Understanding the retreat behaviour of past marine-ice sheets provides vital context to accurate assessment of the present stability and long-term response of contemporary polar-ice sheets to climate and oceanic warming. Here new multibeam swath-bathymetry data and sedimentological analysis are combined with high resolution ice-sheet modelling to reveal complex landform assemblages and process-dynamics associated with deglaciation of the British-Celtic Ice Sheet (BCIS) within the Irish Sea Basin. Our reconstruction indicates a non-linear relationship between the rapidly receding Irish Sea Ice Stream, the largest draining the BCIS, and the retreat of outlet glaciers draining the adjacent, terrestrially based ice sheet centred over Wales. Retreat of Welsh ice was episodic; superimposed over low-order oscillations of its margin are asynchronous outlet re-advances driven by catchment-wide mass balance variations that are amplified through migration of the ice cap's main ice-divide. Formation of large, linear ridges which extend at least 12.5 km offshore (locally known as sarns) and dominate the regional bathymetry are attributed to repeated frontal and medial morainic deposition associated with the re-advancing phases of these outlet glaciers. Our study provides new insight into ice-sheet extent, dynamics and non-linear retreat across a major palaeo-ice stream confluence zone, and has ramifications for the interpretation of recent fluctuations observed by satellites over short-time scales across marine-sectors of the Greenland and Antarctic ice sheets.

Coupled solid Earth – Antarctic ice sheet simulations with VILMA and PISM

2021 ◽  
Author(s):  
Torsten Albrecht ◽  
Meike Bagge ◽  
Ricarda Winkelmann ◽  
Volker Klemann
Keyword(s):  
Solid Earth ◽  
Sea Level ◽  
Climate Modeling ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Glacial Cycle ◽  
Glacial Cycles ◽  
Amundsen Sea ◽  
Antarctic Ice Sheet ◽  
Isostatic Adjustment

<p><span>The Antarctic Ice Sheet rests on a bed that is characterized by tectonical activity and hence by a heterogeneous rheology. Spots of extremely weak lithosphere structure could have strong impacts on the Glacial Isostatic Adjustment and hence on the stability of the ice sheet, possibly also for confined glacier regions and on timescales of decades down to even years (Barletta et al., 2018).</span><span><br><br></span><span>We coupled the VIscoelastic Lithosphere and MAntle model (VILMA) to the Parallel Ice Sheet Model (PISM) </span><span>and ran simulations over the last two glacial cycles. In this framework, VILMA considers both viscoelastic deformations of the solid Earth and gravitationally consistent mass redistribution in the ocean by solving for the sea-level equation (Martinec et al., 2018)</span><span>. In turn, PISM interprets this as a vertical shift in bed topography that directly affects the stress balance within the ice sheet and hence the grounding line dynamics at the interface of ice, ocean and bedrock.</span><span><br><br></span><span>Here we present first results of the coupled Antarctic glacial-cycle simulations and investigate technical aspects, such as optimal coupling time steps, iteration schemes and convergence, for both one-dimensional and three-dimensional Earth structures. This project is part of the </span><span>German Climate Modeling Initiative, PalMod2.</span></p><p> </p><p><span>References:</span></p><p><sup><span>Barletta et al., 2018. <em>Observed rapid bedrock uplift in Amundsen Sea Embayment promotes ice-sheet stability. </em><strong>Science</strong>, <em>360</em>, pp.1335-1339. DOI: 10.1126/science.aao1447</span></sup></p><p><sup><span>Martinec et al., 2018. <em>A benchmark study of numerical implementations of the sea level equation in GIA modelling</em>. </span><span><strong>Geophysical Journal International</strong></span><span>, <em>215</em>(1), pp.389-414. DOI: 10.1093/gji/ggy280</span></sup></p><p> </p>

The Impact of Global Ice Sheet Evolution on North Sea Glacial Isostatic Adjustment during the Last Interglacial

2021 ◽  
Author(s):  
Oliver Pollard ◽  
Natasha Barlow ◽  
Lauren Gregoire ◽  
Natalya Gomez ◽  
Víctor Cartelle
Keyword(s):  
Sea Level ◽  
North Sea ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Last Interglacial ◽  
Isostatic Adjustment ◽  
The North ◽  
The North Sea ◽  
The Impact

<p>The Last Interglacial (LIG) period (130 - 115 ka) was the last time in Earth’s history that the Greenland and Antarctic ice sheets were smaller than those of today due, in part, to polar temperatures reaching 3 - 5 °C above pre-industrial values. Similar polar temperature increases are predicted in the coming decades and the LIG period could therefore help to shed light on ice sheet and sea level mechanisms in a warming world.</p><p>The North Sea region is a promising study site for the reconstruction of both the magnitude and rate of LIG sea-level change as well as the identification of relative, individual ice sheet contributions to sea level. The impact of glacial isostatic adjustment (GIA) is particularly significant for the North Sea region due to its proximity to the former Eurasian ice sheet, which deglaciated during the penultimate deglaciation leading into the LIG. The evolution of the local Eurasian and global ice sheets during the penultimate glacial cycle has left a complex spatio-temporal pattern of GIA during the LIG, both regionally and globally. In addition, interpretation of the LIG record is further complicated by uncertainties in ongoing earth deformation and sea level evolution since the LIG. However, there are large uncertainties in the geometry and evolution of global ice sheets before the Last Glacial Maximum and, in particular, a major source of uncertainty for North Sea LIG records is the geometry and evolution of the Eurasian ice sheet during the Penultimate Glacial Maximum (PGM).</p><p>We produce a range of plausible global ice sheet histories spanning the last 400 thousand years that vary in penultimate deglaciation characteristics including glacial maximum ice sheet volume, deglaciation timing, and the ice volume distribution of the Eurasian ice sheet. This novel PGM Eurasian component is constructed with the use of a simple ice sheet model (Gowan et al. 2016) enabling systematic variation in the thickness of each ice sheet region within known uncertainty ranges. We then employ a gravitationally consistent sea level model (Kendall et al. 2005) with a range of viscoelastic Earth structure models to calculate the global GIA response to each ice history and to infer which input parameters the North Sea LIG signal is most sensitive to. This work will improve our understanding of the GIA effects on near field relative sea level during previous interglacials and will enable a systematic quantification of uncertainties in LIG sea level in the North Sea.</p>

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