Insights into spatial sensitivities of ice mass response to environmental change from the SeaRISE ice sheet modeling project I: Antarctica

Nowicki, Sophie; Bindschadler, Robert; Abe‐Ouchi, Ayako; Aschwanden, Andy; Bueler, Ed; Choi, Hyeungu; Fastook, J. L.; Granzow, Glen D.; Greve, Ralf; Gutowski, G.; Herzfeld, U. C.; Jackson, Charles S.; Johnson, Jesse V.; Khroulev, C.; Larour, Eric; Levermann, Anders; Lipscomb, William H.; Martin, Maria A.; Morlighem, Mathieu; Parizek, B. R.; Pollard, David; Price, Stephen; Ren, Diandong; Rignot, Eric; Saito, Fuyuki; Sato, Takaaki; Seddik, Hakime; Seroussi, Hélène; Takahashi, Kunio; Walker, R. T.; Wang, Wei Li

doi:10.1002/jgrf.20081

Cited by 75 publications

(107 citation statements)

References 147 publications

(249 reference statements)

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“…The most elementary flow regime of the grounded ice sheet is according to the shallow-ice approximation (SIA; Hutter, 1983), extended with either a Weertman type (or power-law) function or a linear/plastic Coulomb friction law for basal sliding. Ice shelf flow is governed by the shallow-shelf approximation (SSA; Morland, 1987;MacAyeal, 1989), defined by zero basal drag and extended by a water-pressure condition at the seaward edge. The transition between both systems is given by a flux condition at the grounding line DeConto, 2009, 2012a), either derived from boundary layer theory based on SSA (SGL; Schoof, 2007a) or given by a flux condition based on Coulomb friction at the grounding line (TGL; Tsai et al, 2015).…”

Section: Approximationsmentioning

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)

Pattyn

2017

The Cryosphere

155

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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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Section: Approximationsmentioning

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)

Pattyn

2017

The Cryosphere

155

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“…Levermann et al [110] developed a probabilistic approach to projecting the contribution of Antarctica to GMSL by employing linear response functions based on the response of three ice sheet models from the SEARISE exercise [116] to an idealized step increase in marine melt. A scaling is developed between global mean temperature change and ocean temperatures around Antarctica based on the CMIP5 ensemble, which combined with the response functions forms a probabilistic framework for making projections.…”

Section: Antarctic Ice Sheetmentioning

confidence: 99%

Recent Progress in Understanding and Projecting Regional and Global Mean Sea Level Change

Clark

Church

Gregory

et al. 2015

Curr Clim Change Rep

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Considerable progress has been made in understanding the present and future regional and global sea level in the 2 years since the publication of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change. Here, we evaluate how the new results affect the AR5's assessment of (i) historical sea level rise, including attribution of that rise and implications for the sea level budget, (ii) projections of the components and of total global mean sea level (GMSL), and (iii) projections of regional variability and emergence of the anthropogenic signal. In each of these cases, new work largely provides additional evidence in support of the AR5 assessment, providing greater confidence in those findings. Recent analyses confirm the twentieth century sea level rise, with some analyses showing a slightly smaller rate before 1990 and some a slightly larger value than reported in the AR5. There is now more evidence of an acceleration in the rate of rise. Ongoing ocean heat uptake and associated thermal expansion have continued since 2000, and are consistent with ocean thermal expansion reported in the AR5. A significant amount of heat is being stored deeper in the water column, with a larger rate of heat uptake since 2000 compared to the previous decades and with the largest storage in the Southern Ocean. The first formal detection studies for ocean thermal expansion and glacier mass loss since the AR5 have confirmed the AR5 finding of a significant anthropogenic contribution to sea level rise over the last 50 years. New projections of glacier loss from two regions suggest smaller contributions to GMSL rise from these regions than in studies assessed by the AR5; additional regional studies are required to further assess whether there are broader implications of these results. Mass loss from the Greenland Ice Sheet, primarily as a result of increased surface melting, and from the Antarctic Ice Sheet, primarily as a result of increased ice discharge, has accelerated. The largest estimates of acceleration in mass loss from the two ice sheets for 2003-2013 equal or exceed the acceleration of GMSL rise calculated from the satellite altimeter sea level record over the longer period of 1993-2014. However, when increased mass gain in land water storage and parts of East Antarctica, and decreased mass loss from glaciers in Alaska and some other regions are taken into account, the net acceleration in the ocean mass gain is consistent with the satellite altimeter record. New studies suggest that a marine ice sheet instability (MISI) may have been initiated in parts of the West Antarctic Ice Sheet (WAIS), but that it will affect only a limited number of ice streams in the twenty-first century. New projections of mass loss from the Greenland and Antarctic Ice Sheets by 2100, including a contribution from parts of WAIS undergoing unstable retreat, suggest a contribution that falls largely within the likely range (i.e., two thirds probability) of the AR5. These new results increase confidence in the AR5 likel...

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“…Antarctic and Greenland ice sheet model ensembles, in particular, remain in their infancy. Only one attempt has been produced so far, namely the SeaRISE initiative, which has been extensively reported in three pivotal papers by Bindschadler et al (2013) and Nowicki et al (2013a, b). Results of all participating models were aggregated into unweighted model averages to produce SLR projections.…”

Section: G Durand and F Pattyn: Antarctic Projections Uncertainitiesmentioning

confidence: 99%

Reducing uncertainties in projections of Antarctic ice mass loss

Durand

Pattyn

2015

The Cryosphere

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Abstract.Climate model projections are often aggregated into multi-model averages of all models participating in an intercomparison project, such as the Coupled Model Intercomparison Project (CMIP). The "multi-model" approach provides a sensitivity test to the models' structural choices and implicitly assumes that multiple models provide additional and more reliable information than a single model, with higher confidence being placed on results that are common to an ensemble. A first initiative of the ice sheet modeling community, SeaRISE, provided such multi-model average projections of polar ice sheets' contribution to sealevel rise. The SeaRISE Antarctic numerical experiments aggregated results from all models devoid of a priori selection, based on the capacity of such models to represent key ice-dynamical processes. Here, using the experimental setup proposed in SeaRISE, we demonstrate that correctly representing grounding line dynamics is essential to infer future Antarctic mass change. We further illustrate the significant impact on the ensemble mean and deviation of adding one model with a known bias in its ability of modeling grounding line dynamics. We show that this biased model can hardly be identified from the ensemble only based on its estimation of volume change, as ad hoc and untrustworthy parametrizations can force any modeled grounding line to retreat. However, tools are available to test parts of the response of marine ice sheet models to perturbations of climatic and/or oceanic origin (MISMIP, MISMIP3d). Based on recent projections of Pine Island Glacier mass loss, we further show that excluding ice sheet models that do not pass the MISMIP benchmarks decreases the mean contribution and standard deviation of the multi-model ensemble projection by an order of magnitude for that particular drainage basin.

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Insights into spatial sensitivities of ice mass response to environmental change from the SeaRISE ice sheet modeling project I: Antarctica

Cited by 75 publications

References 147 publications

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)

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)

Recent Progress in Understanding and Projecting Regional and Global Mean Sea Level Change

Reducing uncertainties in projections of Antarctic ice mass loss

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