Dynamic influence of pinning points on marine ice-sheet stability: a numerical study in Dronning Maud Land, East Antarctica

Favier, Lionel; Pattyn, Frank; Berger, Sophie; Drews, Reinhard

doi:10.5194/tc-10-2623-2016

Cited by 67 publications

(79 citation statements)

References 47 publications

(82 reference statements)

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“…The lack of a sub-grid fjord treatment does not allow for a proper analysis of the ice front processes which become relevant when the retreat has reached the continental area above the sea level. Especially when, as in our case, the submarine melt goes abruptly to a high value at the grounding line, the implementation of a sub-grid-scale parameterization would allow the small processes at the fjords to be accurately resolved (Calov et al, 2015;Favier et al, 2016;Gladstone et al, 2017). However, these limitations lead to only secondorder effects given the scope of our work.…”

Section: Discussionmentioning

confidence: 79%

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

et al. 2018

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Abstract.Observations suggest that during the last decades the Greenland Ice Sheet (GrIS) has experienced a gradually accelerating mass loss, in part due to the observed speedup of several of Greenland's marine-terminating glaciers. Recent studies directly attribute this to warming North Atlantic temperatures, which have triggered melting of the outlet glaciers of the GrIS, grounding-line retreat and enhanced ice discharge into the ocean, contributing to an acceleration of sea-level rise. Reconstructions suggest that the influence of the ocean has been of primary importance in the past as well. This was the case not only in interglacial periods, when warmer climates led to a rapid retreat of the GrIS to land above sea level, but also in glacial periods, when the GrIS expanded as far as the continental shelf break and was thus more directly exposed to oceanic changes. However, the GrIS response to palaeo-oceanic variations has yet to be investigated in detail from a mechanistic modelling perspective. In this work, the evolution of the GrIS over the past two glacial cycles is studied using a three-dimensional hybrid ice-sheetshelf model. We assess the effect of the variation of oceanic temperatures on the GrIS evolution on glacial-interglacial timescales through changes in submarine melting. The results show a very high sensitivity of the GrIS to changing oceanic conditions. Oceanic forcing is found to be a primary driver of GrIS expansion in glacial times and of retreat in interglacial periods. If switched off, palaeo-atmospheric variations alone are not able to yield a reliable glacial configuration of the GrIS. This work therefore suggests that considering the ocean as an active forcing should become standard practice in palaeo-ice-sheet modelling.

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Section: Discussionmentioning

confidence: 79%

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

et al. 2018

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“…In subsequent decades, the BIS gradually readvanced and reestablished contact with the bedrock at the MIR, whilst velocities decreased to pre-1970 levels (Gudmundsson et al, 2017). This cycle of internal dynamical change controlled by calving-induced unpinning and subsequent regrounding at the MIR is arguably not a unique phenomenon, as many ice shelves around Antarctica, and in particular in Dronning Maud Land, are controlled by the presence of one or several pinning points (Matsuoka et al, 2015;Fürst et al, 2015;Favier et al, 2016;Berger et al, 2016). However, the long observational record and the relatively short calving frequency on the order of decades makes the BIS an ideal location to study this cycle.…”

Section: Introductionmentioning

confidence: 99%

Recent rift formation and impact on the structural integrity of the Brunt Ice Shelf, East Antarctica

et al. 2018

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Abstract. We report on the recent reactivation of a large rift in the Brunt Ice Shelf, East Antarctica, in December 2012 and the formation of a 50 km long new rift in October 2016. Observations from a suite of ground-based and remote sensing instruments between January 2000 and July 2017 were used to track progress of both rifts in unprecedented detail. Results reveal a steady accelerating trend in their width, in combination with alternating episodes of fast (> 600 m day −1 ) and slow propagation of the rift tip, controlled by the heterogeneous structure of the ice shelf. A numerical ice flow model and a simple propagation algorithm based on the stress distribution in the ice shelf were successfully used to hindcast the observed trajectories and to simulate future rift progression under different assumptions. Results show a high likelihood of ice loss at the McDonald Ice Rumples, the only pinning point of the ice shelf. The nascent iceberg calving and associated reduction in pinning of the Brunt Ice Shelf may provide a uniquely monitored natural experiment of ice shelf variability and provoke a deeper understanding of similar processes elsewhere in Antarctica.

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“…(22). Given the relatively low spatial resolution of a large-scale ice sheet model, small pinning points underneath ice shelves due to small bathymetric rises scraping the bottom of the ice and exerting an extra back pressure on the ice shelf Favier et al, 2016) are not taken into account. To overcome this a simple parametrization based on the standard deviation of observed bathymetry within each model cell was accounted for to introduce a given amount of basal friction of the ice shelf (Pollard and DeConto, 2012a).…”

Section: Calving and Sub-shelf Pinningmentioning

confidence: 99%

“…Since then several marine ice sheet models of the Antarctic ice sheet have been developed, with varying ways of treating the grounding line, i.e. by increasing locally spatial resolution at the grounding line (Favier et al, 2014;Cornford et al, 2015), by making use of local interpolation strategies at the grounding line (Feldmann et al, 2014;Feldmann and Levermann, 2015;Golledge et al, 2015;Winkelmann et al, 2015) or by parametrizing grounding-line flux based on boundary layer theory (Pollard and DeConto, 2009;Pollard et al, 2015;DeConto and Pollard, 2016).…”

Section: Introductionmentioning

confidence: 99%

Sea-level response to melting of Antarctic ice shelves on multi-centennial timescales with the fast Elementary Thermomechanical Ice Sheet model (f.ETISh v1.0)

2017

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Abstract. The magnitude of the Antarctic ice sheet's contribution to global sea-level rise is dominated by the potential of its marine sectors to become unstable and collapse as a response to ocean (and atmospheric) forcing. This paper presents Antarctic sea-level response to sudden atmospheric and oceanic forcings on multi-centennial timescales with the newly developed fast Elementary Thermomechanical Ice Sheet (f.ETISh) model. The f.ETISh model is a vertically integrated hybrid ice sheet-ice shelf model with vertically integrated thermomechanical coupling, making the model twodimensional. Its marine boundary is represented by two different flux conditions, coherent with power-law basal sliding and Coulomb basal friction. The model has been compared to existing benchmarks.Modelled Antarctic ice sheet response to forcing is dominated by sub-ice shelf melt and the sensitivity is highly dependent on basal conditions at the grounding line. Coulomb friction in the grounding-line transition zone leads to significantly higher mass loss in both West and East Antarctica on centennial timescales, leading to 1.5 m sea-level rise after 500 years for a limited melt scenario of 10 m a −1 under freely floating ice shelves, up to 6 m for a 50 m a −1 scenario. The higher sensitivity is attributed to higher ice fluxes at the grounding line due to vanishing effective pressure.Removing the ice shelves altogether results in a disintegration of the West Antarctic ice sheet and (partially) marine basins in East Antarctica. After 500 years, this leads to a 5 m and a 16 m sea-level rise for the power-law basal sliding and Coulomb friction conditions at the grounding line, respectively. The latter value agrees with simulations by DeConto and Pollard (2016) over a similar period (but with different forcing and including processes of hydrofracturing and cliff failure).The chosen parametrizations make model results largely independent of spatial resolution so that f.ETISh can potentially be integrated in large-scale Earth system models.

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Dynamic influence of pinning points on marine ice-sheet stability: a numerical study in Dronning Maud Land, East Antarctica

Cited by 67 publications

References 47 publications

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

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

Recent rift formation and impact on the structural integrity of the Brunt Ice Shelf, East Antarctica

Sea-level response to melting of Antarctic ice shelves on multi-centennial timescales with the fast Elementary Thermomechanical Ice Sheet model (f.ETISh v1.0)

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