Antarctic sub-shelf melt rates via PICO

Reese, Ronja; Albrecht, Torsten; Mengel, Matthias; Asay‐Davis, Xylar; Winkelmann, Ricarda

doi:10.5194/tc-12-1969-2018

Cited by 133 publications

(225 citation statements)

References 56 publications

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“…We convert the CMIP5 projections of ocean temperature into a mean additional ocean sub-shelf melt forcing using the linear relationship between temperature anomaly and ice shelf melting, which is approximated for the ASE (Rignot and Jacobs, 2002), where an additional 0.1 • C temperature increase results in an increase of 1 m a −1 to the basal melt rate. The CMIP5 AOGCM forcing data that we use are relatively coarse in their spatial resolution and also do not capture sub-ice-shelf oceanographic conditions.…”

Section: Cmip5 Melt Rate Forcingmentioning

confidence: 99%

Ocean-forced evolution of the Amundsen Sea catchment, West Antarctica, by 2100

et al. 2020

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The response of ice streams in the Amundsen Sea Embayment (ASE) to future climate forcing is highly uncertain. Here we present projections of 21st century response of ASE ice streams to modelled local ocean temperature change using a subset of Coupled Model Intercomparison Project (CMIP5) simulations. We use the BISICLES adaptive mesh refinement (AMR) ice sheet model, with highresolution grounding line resolving capabilities, to explore grounding line migration in response to projected sub-iceshelf basal melting. We find a contribution to sea level rise of between 2.0 and 4.5 cm by 2100 under RCP8.5 conditions from the CMIP5 subset, where the mass loss response is linearly related to the mean ocean temperature anomaly. To account for uncertainty associated with model initialization, we perform three further sets of CMIP5-forced experiments using different parameterizations that explore perturbations to the prescription of initial basal melt, the basal traction coefficient and the ice stiffening factor. We find that the response of the ASE to ocean temperature forcing is highly dependent on the parameter fields obtained in the initialization procedure, where the sensitivity of the ASE ice streams to the sub-iceshelf melt forcing is dependent on the choice of parameter set. Accounting for ice sheet model parameter uncertainty results in a projected range in sea level equivalent contribution from the ASE of between −0.02 and 12.1 cm by the end of the 21st century.Published by Copernicus Publications on behalf of the European Geosciences Union.

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Section: Cmip5 Melt Rate Forcingmentioning

confidence: 99%

Ocean-forced evolution of the Amundsen Sea catchment, West Antarctica, by 2100

et al. 2020

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“…These studies, however, are all based on ideal geometries and completely ignore basal melt under floating ice (i.e., no melt is applied under floating ice). In reality, melt can be strong, es- pecially in the vicinity of the grounding line, where it can reach ∼ 100 m yr −1 (Dutrieux et al, 2013;Rignot et al, 2013;Berger et al, 2017). Several studies have shown that, for the same melt parameterization, the choice of numerical implementation of melt has a strong impact on model results for both projections of the West Antarctic Ice Sheet Arthern and Williams, 2017) and idealized glaciers (Gladstone et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Representation of basal melting at the grounding line in ice flow models

Seroussi¹,

Morlighem²

2018

Preprint

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Abstract. While a lot of attention has been given to the numerical implementation of grounding lines and basal friction in the grounding zone, little has been done about the impact of the numerical treatment of ocean-induced basal melting in this region. Several strategies are currently being employed in the ice sheet modeling community, and the resulting grounding line dynamics may differ strongly, which ultimately add significant uncertainty to the projected contribution of marine ice sheets to sea level rise. We investigate here several implementations of basal melt parameterization on partially floating elements in a finite element framework, based on the Marine Ice Sheet-Ocean Model Intercomparison Project (MISOMIP) setup: (1) melt applied only to entirely floating elements, (2) melt applied over the entire elements that are crossed by the grounding line, and (3) melt integrated partially over the floating portion of a finite element using two different sub-element integration methods. All methods converge towards the same state when the mesh resolution is fine enough. However, (2) and (3) will systematically overestimate the rate of grounding line retreat in coarser resolutions, while (1) converges faster to the solution in most cases. The differences between sub-element parameterizations are exacerbated for experiments with large melting rates in the vicinity of the grounding line and for a Weertman sliding law. As most real-world simulations use horizontal mesh resolutions of several hundreds of meters at best, and large melt rates are generally present close to the grounding lines, we recommend using (1) to avoid overestimating the rate of grounding line retreat.

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“…Converting ocean conditions into ocean-induced melt at the base of ice shelves is an active area of research, and several parameterizations with different levels of complexity have recently been proposed for converting ocean conditions into ice 120 shelf melt rates (Lazeroms et al, 2018;Reese et al, 2018a;Pelle et al, 2019). As only a limited number of direct observations of ocean conditions (Jenkins et al, 2010;Dutrieux et al, 2014) and ice shelf melt rates Depoorter et al, 2013) exist, these parameterizations are difficult to calibrate and evaluate.…”

mentioning

confidence: 99%

“…Geothermal heat flux is from Shapiro and Ritzwoller (2004). We use the Potsdam Ice-shelf Cavity model (PICO, Reese et al, 2018a) which extends the ocean box model by Olbers and Hellmer (2010) for application in three dimensional ice-sheet models to calculate basal melt rate patterns underneath the ice shelves. We use a compilation of observed ocean temperature and salinity values 2013, Schmidtko et al, 2014) (1955, Locarnini et al, 2019 to drive PICO.…”

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confidence: 99%

ISMIP6 Antarctica: a multi-model ensemble of the Antarctic ice sheet evolution over the 21st century

Seroussi¹,

Goelzer²,

Morlighem³

2020

Preprint

122

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Ice flow models of the Antarctic ice sheet are commonly used to simulate its future evolution in response to different climate scenarios and inform on the mass loss that would contribute to future sea level rise. However, there is currently no consensus on estimated the future mass balance of the ice sheet, primarily because of differences in the representation of physical processes and the forcings employed. This study presents results from 18 simulations from 15 international groups focusing on the evolution of the Antarctic ice sheet during the period 2015-2100, forced with different scenarios from the Cou-5 pled Model Intercomparison Project Phase 5 (CMIP5) representative of the spread in climate model results. The contribution of the Antarctic ice sheet in response to increased warming during this period varies between -7.8 and 30.0 cm of Sea Level Equivalent (SLE). The evolution of the West Antarctic Ice Sheet varies widely among models, with an overall mass loss up to 21.0 cm SLE in response to changes in oceanic conditions. East Antarctica mass change varies between -6.5 and 16.5 cm SLE, with a significant increase in surface mass balance outweighing the increased ice discharge under most RCP 8.5 scenario 10 forcings. The inclusion of ice shelf collapse, here assumed to be caused by large amounts of liquid water ponding at the surface of ice shelves, yields an additional mass loss of 8 mm compared to simulations without ice shelf collapse. The largest sources of uncertainty come from the ocean-induced melt rates, the calibration of these melt rates based on oceanic conditions taken outside of ice shelf cavities and the ice sheet dynamic response to these oceanic changes. Results under RCP 2.6 scenario based on two CMIP5 AOGCMs show an overall mass loss of 10 mm SLE compared to simulations done under present-day 15 conditions, with limited mass gain in East Antarctica.

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Antarctic sub-shelf melt rates via PICO

Cited by 133 publications

References 56 publications

Ocean-forced evolution of the Amundsen Sea catchment, West Antarctica, by 2100

Ocean-forced evolution of the Amundsen Sea catchment, West Antarctica, by 2100

Representation of basal melting at the grounding line in ice flow models

ISMIP6 Antarctica: a multi-model ensemble of the Antarctic ice sheet evolution over the 21st century

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