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Publisher: Cambridge : Cambridge University Press × Subject: ice-sheet modelling ×

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    SHMIP The subglacial hydrology model intercomparison Project
    (Cambridge : Cambridge University Press, 2018) De Fleurian, Basile; Werder, Mauro A.; Beyer, Sebastian; Brinkenhoff, Douglas J.; Delaney, Ian; Dow, Christine F.; Downs, Jacob; Gagliardini, Olivier; Hoffman, Matthew J.; HookeE, Roger LeB; Seguinot, Julien; Sommers, Aleah N.
    Subglacial hydrology plays a key role in many glaciological processes, including ice dynamics via the modulation of basal sliding. Owing to the lack of an overarching theory, however, a variety of model approximations exist to represent the subglacial drainage system. The Subglacial Hydrology Model Intercomparison Project (SHMIP) provides a set of synthetic experiments to compare existing and future models. We present the results from 13 participating models with a focus on effective pressure and discharge. For many applications (e.g. steady states and annual variations, low input scenarios) a simple model, such as an inefficient-system-only model, a flowline or lumped model, or a porous-layer model provides results comparable to those of more complex models. However, when studying short term (e.g. diurnal) variations of the water pressure, the use of a two-dimensional model incorporating physical representations of both efficient and inefficient drainage systems yields results that are significantly different from those of simpler models and should be preferentially applied. The results also emphasise the role of water storage in the response of water pressure to transient recharge. Finally, we find that the localisation of moulins has a limited impact except in regions of sparse moulin density.
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    Antarctic ice sheet response to sudden and sustained ice-shelf collapse (ABUMIP)
    (Cambridge : Cambridge University Press, 2020) Sun, Sainan; Pattyn, Frank; Simon, Erika G.; Albrecht, Torsten; Cornford, Stephen; Calov, Reinhard; Dumas, Christophe; Gillet-Chaulet, Fabien; Goelzer, Goelzer; Golledge, Nicholas R.; Greve, Ralf; Hoffman, Matthew J.; Humbert, Angelika; Kazmierczak, Elise; Kleiner, Thomas; Leguy, Gunter R.; Lipscomb, William H.; Martin, Daniel; Morlighem, Mathieu; Nowicki, Sophie; Pollard, David; Price, Stephen; Quiquet, Aurélien; Seroussi, Hélène; Schlemm, Tanja; Sutter, Johannes; van de Wal, Roderik S.W.; Winkelmann, Ricarda; Zhang, Tong
    Antarctica's ice shelves modulate the grounded ice flow, and weakening of ice shelves due to climate forcing will decrease their 'buttressing' effect, causing a response in the grounded ice. While the processes governing ice-shelf weakening are complex, uncertainties in the response of the grounded ice sheet are also difficult to assess. The Antarctic BUttressing Model Intercomparison Project (ABUMIP) compares ice-sheet model responses to decrease in buttressing by investigating the 'end-member' scenario of total and sustained loss of ice shelves. Although unrealistic, this scenario enables gauging the sensitivity of an ensemble of 15 ice-sheet models to a total loss of buttressing, hence exhibiting the full potential of marine ice-sheet instability. All models predict that this scenario leads to multi-metre (1-12 m) sea-level rise over 500 years from present day. West Antarctic ice sheet collapse alone leads to a 1.91-5.08 m sea-level rise due to the marine ice-sheet instability. Mass loss rates are a strong function of the sliding/friction law, with plastic laws cause a further destabilization of the Aurora and Wilkes Subglacial Basins, East Antarctica. Improvements to marine ice-sheet models have greatly reduced variability between modelled ice-sheet responses to extreme ice-shelf loss, e.g. compared to the SeaRISE assessments. Copyright © The Author(s) 2020.