TY - JOUR A1 - Bindschadler, Robert A. A1 - Nowicki, Sophie A1 - Abe-Ouchi, Ayako A1 - Aschwanden, Andy A1 - Choi, Hyeungu A1 - Fastook, Jim A1 - Granzow, Glen A1 - Greve, Ralf A1 - Gutowski, Gail A1 - Herzfeld, Ute A1 - Jackson, Charles A1 - Johnson, Jesse A1 - Khroulev, Constantine A1 - Levermann, Anders A1 - Lipscomb, William H. A1 - Martin, Maria A. A1 - Morlighem, Mathieu A1 - Parizek, Byron R. A1 - Pollard, David A1 - Price, Stephen F. A1 - Ren, Diandong A1 - Saito, Fuyuki A1 - Sato, Tatsuru A1 - Seddik, Hakime A1 - Seroussi, Helene A1 - Takahashi, Kunio A1 - Walker, Ryan A1 - Wang, Wei Li T1 - Ice-sheet model sensitivities to environmental forcing and their use in projecting future sea level (the SeaRISE project) JF - Journal of glaciology N2 - Ten ice-sheet models are used to study sensitivity of the Greenland and Antarctic ice sheets to prescribed changes of surface mass balance, sub-ice-shelf melting and basal sliding. Results exhibit a large range in projected contributions to sea-level change. In most cases, the ice volume above flotation lost is linearly dependent on the strength of the forcing. Combinations of forcings can be closely approximated by linearly summing the contributions from single forcing experiments, suggesting that nonlinear feedbacks are modest. Our models indicate that Greenland is more sensitive than Antarctica to likely atmospheric changes in temperature and precipitation, while Antarctica is more sensitive to increased ice-shelf basal melting. An experiment approximating the Intergovernmental Panel on Climate Change's RCP8.5 scenario produces additional first-century contributions to sea level of 22.3 and 8.1 cm from Greenland and Antarctica, respectively, with a range among models of 62 and 14 cm, respectively. By 200 years, projections increase to 53.2 and 26.7 cm, respectively, with ranges of 79 and 43 cm. Linear interpolation of the sensitivity results closely approximates these projections, revealing the relative contributions of the individual forcings on the combined volume change and suggesting that total ice-sheet response to complicated forcings over 200 years can be linearized. Y1 - 2013 U6 - https://doi.org/10.3189/2013JoG12J125 SN - 0022-1430 VL - 59 IS - 214 SP - 195 EP - 224 PB - International Glaciological Society CY - Cambridge ER - TY - JOUR A1 - Levermann, Anders A1 - Clark, Peter U. A1 - Marzeion, Ben A1 - Milne, Glenn A. A1 - Pollard, David A1 - Radic, Valentina A1 - Robinson, Alexander T1 - The multimillennial sea-level commitment of global warming JF - Proceedings of the National Academy of Sciences of the United States of America N2 - Global mean sea level has been steadily rising over the last century, is projected to increase by the end of this century, and will continue to rise beyond the year 2100 unless the current global mean temperature trend is reversed. Inertia in the climate and global carbon system, however, causes the global mean temperature to decline slowly even after greenhouse gas emissions have ceased, raising the question of how much sea-level commitment is expected for different levels of global mean temperature increase above preindustrial levels. Although sea-level rise over the last century has been dominated by ocean warming and loss of glaciers, the sensitivity suggested from records of past sea levels indicates important contributions should also be expected from the Greenland and Antarctic Ice Sheets. Uncertainties in the paleo-reconstructions, however, necessitate additional strategies to better constrain the sea-level commitment. Here we combine paleo-evidence with simulations from physical models to estimate the future sea-level commitment on a multimillennial time scale and compute associated regional sea-level patterns. Oceanic thermal expansion and the Antarctic Ice Sheet contribute quasi-linearly, with 0.4 m degrees C-1 and 1.2 m degrees C-1 of warming, respectively. The saturation of the contribution from glaciers is overcompensated by the nonlinear response of the Greenland Ice Sheet. As a consequence we are committed to a sea-level rise of approximately 2.3 m degrees C-1 within the next 2,000 y. Considering the lifetime of anthropogenic greenhouse gases, this imposes the need for fundamental adaptation strategies on multicentennial time scales. KW - climate change KW - climate impacts KW - sea-level change Y1 - 2013 U6 - https://doi.org/10.1073/pnas.1219414110 SN - 0027-8424 VL - 110 IS - 34 SP - 13745 EP - 13750 PB - National Acad. of Sciences CY - Washington ER - TY - JOUR A1 - Nowicki, Sophie A1 - Bindschadler, Robert A. A1 - Abe-Ouchi, Ayako A1 - Aschwanden, Andy A1 - Bueler, Ed A1 - Choi, Hyeungu A1 - Fastook, Jim A1 - Granzow, Glen A1 - Greve, Ralf A1 - Gutowski, Gail A1 - Herzfeld, Ute A1 - Jackson, Charles A1 - Johnson, Jesse A1 - Khroulev, Constantine A1 - Larour, Eric A1 - Levermann, Anders A1 - Lipscomb, William H. A1 - Martin, Maria A. A1 - Morlighem, Mathieu A1 - Parizek, Byron R. A1 - Pollard, David A1 - Price, Stephen F. A1 - Ren, Diandong A1 - Rignot, Eric A1 - Saito, Fuyuki A1 - Sato, Tatsuru A1 - Seddik, Hakime A1 - Seroussi, Helene A1 - Takahashi, Kunio A1 - Walker, Ryan A1 - Wang, Wei Li T1 - Insights into spatial sensitivities of ice mass response to environmental change from the SeaRISE ice sheet modeling project II Greenland JF - Journal of geophysical research : Earth surface N2 - The Sea-level Response to Ice Sheet Evolution (SeaRISE) effort explores the sensitivity of the current generation of ice sheet models to external forcing to gain insight into the potential future contribution to sea level from the Greenland and Antarctic ice sheets. All participating models simulated the ice sheet response to three types of external forcings: a change in oceanic condition, a warmer atmospheric environment, and enhanced basal lubrication. Here an analysis of the spatial response of the Greenland ice sheet is presented, and the impact of model physics and spin-up on the projections is explored. Although the modeled responses are not always homogeneous, consistent spatial trends emerge from the ensemble analysis, indicating distinct vulnerabilities of the Greenland ice sheet. There are clear response patterns associated with each forcing, and a similar mass loss at the full ice sheet scale will result in different mass losses at the regional scale, as well as distinct thickness changes over the ice sheet. All forcings lead to an increased mass loss for the coming centuries, with increased basal lubrication and warmer ocean conditions affecting mainly outlet glaciers, while the impacts of atmospheric forcings affect the whole ice sheet. KW - Greenland KW - ice-sheet KW - sea-level KW - model KW - ensemble Y1 - 2013 U6 - https://doi.org/10.1002/jgrf.20076 SN - 2169-9003 VL - 118 IS - 2 SP - 1025 EP - 1044 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Pattyn, Frank A1 - Perichon, Laura A1 - Durand, Gael A1 - Favier, Lionel A1 - Gagliardini, Olivier A1 - Hindmarsh, Richard C. A. A1 - Zwinger, Thomas A1 - Albrecht, Torsten A1 - Cornford, Stephen A1 - Docquier, David A1 - Furst, Johannes J. A1 - Goldberg, Daniel A1 - Gudmundsson, Gudmundur Hilmar A1 - Humbert, Angelika A1 - Huetten, Moritz A1 - Huybrechts, Philippe A1 - Jouvet, Guillaume A1 - Kleiner, Thomas A1 - Larour, Eric A1 - Martin, Daniel A1 - Morlighem, Mathieu A1 - Payne, Anthony J. A1 - Pollard, David A1 - Rueckamp, Martin A1 - Rybak, Oleg A1 - Seroussi, Helene A1 - Thoma, Malte A1 - Wilkens, Nina T1 - Grounding-line migration in plan-view marine ice-sheet models: results of the ice2sea MISMIP3d intercomparison JF - Journal of glaciology N2 - 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. Y1 - 2013 U6 - https://doi.org/10.3189/2013JoG12J129 SN - 0022-1430 VL - 59 IS - 215 SP - 410 EP - 422 PB - International Glaciological Society CY - Cambridge ER - TY - JOUR A1 - Seroussi, Helene A1 - Nowicki, Sophie A1 - Simon, Erika A1 - Abe-Ouchi, Ayako A1 - Albrecht, Torsten A1 - Brondex, Julien A1 - Cornford, Stephen A1 - Dumas, Christophe A1 - Gillet-Chaulet, Fabien A1 - Goelzer, Heiko A1 - Golledge, Nicholas R. A1 - Gregory, Jonathan M. A1 - Greve, Ralf A1 - Hoffman, Matthew J. A1 - Humbert, Angelika A1 - Huybrechts, Philippe A1 - Kleiner, Thomas A1 - Larourl, Eric A1 - Leguy, Gunter A1 - Lipscomb, William H. A1 - Lowry, Daniel A1 - Mengel, Matthias A1 - Morlighem, Mathieu A1 - Pattyn, Frank A1 - Payne, Anthony J. A1 - Pollard, David A1 - Price, Stephen F. A1 - Quiquet, Aurelien A1 - Reerink, Thomas J. A1 - Reese, Ronja A1 - Rodehacke, Christian B. A1 - Schlegel, Nicole-Jeanne A1 - Shepherd, Andrew A1 - Sun, Sainan A1 - Sutter, Johannes A1 - Van Breedam, Jonas A1 - van de Wal, Roderik S. W. A1 - Winkelmann, Ricarda A1 - Zhang, Tong T1 - initMIP-Antarctica BT - an ice sheet model initialization experiment of ISMIP6 JF - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union N2 - Ice sheet numerical modeling is an important tool to estimate the dynamic contribution of the Antarctic ice sheet to sea level rise over the coming centuries. The influence of initial conditions on ice sheet model simulations, however, is still unclear. To better understand this influence, an initial state intercomparison exercise (initMIP) has been developed to compare, evaluate, and improve initialization procedures and estimate their impact on century-scale simulations. initMlP is the first set of experiments of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6), which is the primary Coupled Model Intercomparison Project Phase 6 (CMIP6) activity focusing on the Greenland and Antarctic ice sheets. Following initMlP-Greenland, initMlP-Antarctica has been designed to explore uncertainties associated with model initialization and spin-up and to evaluate the impact of changes in external forcings. Starting from the state of the Antarctic ice sheet at the end of the initialization procedure, three forward experiments are each run for 100 years: a control run, a run with a surface mass balance anomaly, and a run with a basal melting anomaly beneath floating ice. This study presents the results of initMlP-Antarctica from 25 simulations performed by 16 international modeling groups. The submitted results use different initial conditions and initialization methods, as well as ice flow model parameters and reference external forcings. We find a good agreement among model responses to the surface mass balance anomaly but large variations in responses to the basal melting anomaly. These variations can be attributed to differences in the extent of ice shelves and their upstream tributaries, the numerical treatment of grounding line, and the initial ocean conditions applied, suggesting that ongoing efforts to better represent ice shelves in continental-scale models should continue. Y1 - 2019 U6 - https://doi.org/10.5194/tc-13-1441-2019 SN - 1994-0416 SN - 1994-0424 VL - 13 IS - 5 SP - 1441 EP - 1471 PB - Copernicus CY - Göttingen ER -