@article{FarinottiKingAlbrechtetal.2014, author = {Farinotti, Daniel and King, Edward C. and Albrecht, Anika and Huss, Matthias and Gudmundsson, Gudmundur Hilmar}, title = {The bedrock topography of Starbuck Glacier, Antarctic Peninsula, as determined by radio-echo soundings and flow modeling}, series = {Annals of glaciology}, volume = {55}, journal = {Annals of glaciology}, number = {67}, publisher = {International Glaciological Society}, address = {Cambridge}, issn = {0260-3055}, doi = {10.3189/2014AoG67A025}, pages = {22 -- 28}, year = {2014}, language = {en} } @article{DeichmannAnsorgeScherbaumetal.1999, author = {Deichmann, N. and Ansorge, J{\"o}rg and Scherbaum, Frank and Aschwanden, Andy and Bernadi, F. and Gudmundsson, Gudmundur Hilmar}, title = {Evidence for deep icequakes in an alpine glacier}, year = {1999}, language = {en} } @article{PattynPerichonDurandetal.2013, author = {Pattyn, Frank and Perichon, Laura and Durand, Gael and Favier, Lionel and Gagliardini, Olivier and Hindmarsh, Richard C. A. and Zwinger, Thomas and Albrecht, Torsten and Cornford, Stephen and Docquier, David and Furst, Johannes J. and Goldberg, Daniel and Gudmundsson, Gudmundur Hilmar and Humbert, Angelika and Huetten, Moritz and Huybrechts, Philippe and Jouvet, Guillaume and Kleiner, Thomas and Larour, Eric and Martin, Daniel and Morlighem, Mathieu and Payne, Anthony J. and Pollard, David and Rueckamp, Martin and Rybak, Oleg and Seroussi, Helene and Thoma, Malte and Wilkens, Nina}, title = {Grounding-line migration in plan-view marine ice-sheet models: results of the ice2sea MISMIP3d intercomparison}, series = {Journal of glaciology}, volume = {59}, journal = {Journal of glaciology}, number = {215}, publisher = {International Glaciological Society}, address = {Cambridge}, issn = {0022-1430}, doi = {10.3189/2013JoG12J129}, pages = {410 -- 422}, year = {2013}, abstract = {Predictions of marine ice-sheet behaviour require models able to simulate grounding-line migration. We present results of an intercomparison experiment for plan-view marine ice-sheet models. Verification is effected by comparison with approximate analytical solutions for flux across the grounding line using simplified geometrical configurations (no lateral variations, no buttressing effects from lateral drag). Perturbation experiments specifying spatial variation in basal sliding parameters permitted the evolution of curved grounding lines, generating buttressing effects. The experiments showed regions of compression and extensional flow across the grounding line, thereby invalidating the boundary layer theory. Steady-state grounding-line positions were found to be dependent on the level of physical model approximation. Resolving grounding lines requires inclusion of membrane stresses, a sufficiently small grid size (<500 m), or subgrid interpolation of the grounding line. The latter still requires nominal grid sizes of <5 km. For larger grid spacings, appropriate parameterizations for ice flux may be imposed at the grounding line, but the short-time transient behaviour is then incorrect and different from models that do not incorporate grounding-line parameterizations. The numerical error associated with predicting grounding-line motion can be reduced significantly below the errors associated with parameter ignorance and uncertainties in future scenarios.}, language = {en} } @article{ReeseWinkelmannGudmundsson2018, author = {Reese, Ronja and Winkelmann, Ricarda and Gudmundsson, Gudmundur Hilmar}, title = {Grounding-line flux formula applied as a flux condition in numerical simulations fails for buttressed Antarctic ice streams}, series = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union}, volume = {12}, journal = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union}, number = {10}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1994-0416}, doi = {10.5194/tc-12-3229-2018}, pages = {3229 -- 3242}, year = {2018}, abstract = {Currently, several large-scale ice-flow models impose a condition on ice flux across grounding lines using an analytically motivated parameterisation of grounding-line flux. It has been suggested that employing this analytical expression alleviates the need for highly resolved computational domains around grounding lines of marine ice sheets. While the analytical flux formula is expected to be accurate in an unbuttressed flow-line setting, its validity has hitherto not been assessed for complex and realistic geometries such as those of the Antarctic Ice Sheet. Here the accuracy of this analytical flux formula is tested against an optimised ice flow model that uses a highly resolved computational mesh around the Antarctic grounding lines. We find that when applied to the Antarctic Ice Sheet the analytical expression provides inaccurate estimates of ice fluxes for almost all grounding lines. Furthermore, in many instances direct application of the analytical formula gives rise to unphysical complex-valued ice fluxes. We conclude that grounding lines of the Antarctic Ice Sheet are, in general, too highly buttressed for the analytical parameterisation to be of practical value for the calculation of grounding-line fluxes.}, language = {en} } @article{ReeseGudmundssonLevermannetal.2017, author = {Reese, Ronja and Gudmundsson, Gudmundur Hilmar and Levermann, Anders and Winkelmann, Ricarda}, title = {The far reach of ice-shelf thinning in Antarctica}, series = {Nature climate change}, volume = {8}, journal = {Nature climate change}, number = {1}, publisher = {Nature Publ. Group}, address = {London}, issn = {1758-678X}, doi = {10.1038/s41558-017-0020-x}, pages = {53 -- 57}, year = {2017}, abstract = {Floating ice shelves, which fringe most of Antarctica's coastline, regulate ice flow into the Southern Ocean1,2,3. Their thinning4,5,6,7 or disintegration8,9 can cause upstream acceleration of grounded ice and raise global sea levels. So far the effect has not been quantified in a comprehensive and spatially explicit manner. Here, using a finite-element model, we diagnose the immediate, continent-wide flux response to different spatial patterns of ice-shelf mass loss. We show that highly localized ice-shelf thinning can reach across the entire shelf and accelerate ice flow in regions far from the initial perturbation. As an example, this 'tele-buttressing' enhances outflow from Bindschadler Ice Stream in response to thinning near Ross Island more than 900 km away. We further find that the integrated flux response across all grounding lines is highly dependent on the location of imposed changes: the strongest response is caused not only near ice streams and ice rises, but also by thinning, for instance, well-within the Filchner-Ronne and Ross Ice Shelves. The most critical regions in all major ice shelves are often located in regions easily accessible to the intrusion of warm ocean waters10,11,12, stressing Antarctica's vulnerability to changes in its surrounding ocean.}, language = {en} }