RIMBAY – a multi-approximation 3D ice-dynamics model for comprehensive applications: model description and examples

Thoma, Malte; Grosfeld, Klaus; Barbi, Dirk; Determann, Jürgen; Goeller, Sebastian; Mayer, Christoph; Pattyn, Frank

doi:10.5194/gmd-7-1-2014

Cited by 39 publications

(46 citation statements)

References 59 publications

(86 reference statements)

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“…Given the differences in approach with continental-scale ice sheet models, such as AISM-VUB (Huybrechts, 1990(Huybrechts, , 2002, ANICE (de Boer et al, 2013), GRISLI (Ritz et al, 2015), ISSM (Larour et al, 2012), PISM (Bueler and Brown, 2009), PISM-PIK Winkelmann et al, 2011;Golledge et al, 2015), PSU-ISM (Pollard and DeConto, 2012a), RIMBAY (Thoma et al, 2014) or SICOPO-LIS (Sato and Greve, 2012), verification of the f.ETISh model requires a detailed comparison with existing benchmarks. These are generally based on results of the models cited above.…”

Section: Discussionmentioning

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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Section: Discussionmentioning

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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“…Basic conclusions of both intercomparisons are that in order to resolve grounding lines, the inclusion of membrane stresses across the grounding line is required at a sufficiently small grid size (< 500 m), even when a subgrid interpolation of the grounding line (< 5 km) is preferred. An exception is the use of a grounding line parametrization based on the boundary layer theory due to Schoof, which has been successfully implemented in a series of models (Pollard and DeConto, 2012a; Thoma et al, 2014). This works well for coarse spatial resolutions, but the short-term transient response remains questionable when compared to other approaches (Drouet et al, 2013), especially since the theory has been developed for the steady-state case.…”

Section: The Marine Boundarymentioning

confidence: 99%

“…Surface mass balance is obtained from Van de Berg et al (2006) and Van den Broeke et al (2006), based on the output of a regional atmospheric climate model for the period 1980 to 2004, and calibrated using observed mass balance rates. During these runs, Eq.…”

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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“…(3)) but not the rate of accumulation or ablation. As done in many ice modelling studies (e.g., Tarasov and Peltier, 1999;Seddik et al, 2012;Seguinot, 2014;Thoma et al, 2014;Jouvet et al, 2017), we assume that the ice surface temperature is equal to the mean annual air temperature. Based on earlier climate reconstruction we assume that the mean annual temperature at the equilibrium line is −12…”

Section: Surface Temperaturementioning

confidence: 99%

Numerical reconstructions of the flow and basal conditions of the Rhine glacier, European Central Alps, at the Last Glacial Maximum

Cohen¹,

Gillet-Chaulet²,

Haeberli³

et al. 2017

Preprint

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Abstract. At the Last Glacial Maximum (LGM), the Rhine glacier in the Swiss Alps covered an area of about 16,000 km 2 .As part of an integrative study about the safety of repositories for radioactive waste under ice age conditions in Switzerland, we modeled the Rhine glacier using a fully-coupled, three-dimensional, transient, thermo-mechanical Stokes flow model down to a horizontal resolution of about 500 m. The accumulation and ablation gradients that roughly reproduced the geomorphic reconstructions of glacial extent and ice thickness suggested extremely cold (T July ∼ 0 • C at the glacier terminus) and dry (∼ 10 5 to 20% of today's precipitation) climatic conditions. Forcing the numerical simulations with warmer and wetter conditions that better matched LGM climate proxy records yielded a glacier on average 500 to 700 m thicker than geomorphic reconstructions.Mass balance gradients also controlled ice velocities, fluxes, and sliding speeds. These gradients, however, had only a small effect on basal conditions. All simulations indicated that basal ice reached the pressure melting point over much of the Rhine and Linth piedmont lobes, and also in the glacial valleys that fed these lobes. Only the outer margin of the lobes, bedrock highs ). In the lobes, despite low surface slopes and low basal shear stresses, sliding dictated main fluxes of ice which closely followed bedrock topography: ice was channeled in between bedrock highs along troughs, some of which coincided with glacially eroded overdeepenings. These sliding conditions may have favored glacial erosion by abrasion and quarrying. 20Our results confirmed general earlier findings but provided more insights into the detailed flow and basal conditions of the Rhine glacier at the LGM. Our model results suggested that the trimline could have been buried by a significant thickness of cold ice. These findings have significant implications for interpreting trimlines in the Alps and for our understanding of ice-climate interactions.

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RIMBAY – a multi-approximation 3D ice-dynamics model for comprehensive applications: model description and examples

Cited by 39 publications

References 59 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)

Reducing uncertainties in projections of Antarctic ice mass loss

Numerical reconstructions of the flow and basal conditions of the Rhine glacier, European Central Alps, at the Last Glacial Maximum

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