TY - JOUR T1 - Design and results of the ice sheet model initialisation experiments initMIP-Greenland: an ISMIP6 intercomparison JF - The Cryosphere Y1 - 2018 A1 - Goelzer, Heiko A1 - Nowicki, Sophie A1 - Edwards, Tamsin A1 - Beckley, Matthew A1 - Abe-Ouchi, Ayako A1 - Aschwanden, Andy A1 - Calov, Reinhard A1 - Gagliardini, Olivier A1 - Gillet-Chaulet, Fabien A1 - Golledge, Nicholas R. A1 - Gregory, Jonathan A1 - Greve, Ralf A1 - Humbert, Angelika A1 - Huybrechts, Philippe A1 - Kennedy, Joseph H. A1 - Larour, Eric A1 - Lipscomb, William H. A1 - Le clec'h, Sébastien A1 - Lee, Victoria A1 - Morlighem, Mathieu A1 - Pattyn, Frank A1 - Payne, Antony J. A1 - Rodehacke, Christian A1 - Rückamp, Martin A1 - Saito, Fuyuki A1 - Schlegel, Nicole A1 - Seroussi, Helene A1 - Shepherd, Andrew A1 - Sun, Sainan A1 - van de Wal, Roderik A1 - Ziemen, Florian A. AB - Abstract. Earlier large-scale Greenland ice sheet sea-level projections (e.g. those run during the ice2sea and SeaRISE initiatives) have shown that ice sheet initial conditions have a large effect on the projections and give rise to important uncertainties. The goal of this initMIP-Greenland intercomparison exercise is to compare, evaluate, and improve the initialisation techniques used in the ice sheet modelling community and to estimate the associated uncertainties in modelled mass changes. initMIP-Greenland is the first in a series of ice sheet model intercomparison activities within ISMIP6 (the Ice Sheet Model Intercomparison Project for CMIP6), which is the primary activity within the Coupled Model Intercomparison Project Phase 6 (CMIP6) focusing on the ice sheets. Two experiments for the large-scale Greenland ice sheet have been designed to allow intercomparison between participating models of (1) the initial present-day state of the ice sheet and (2) the response in two idealised forward experiments. The forward experiments serve to evaluate the initialisation in terms of model drift (forward run without additional forcing) and in response to a large perturbation (prescribed surface mass balance anomaly); they should not be interpreted as sea-level projections. We present and discuss results that highlight the diversity of data sets, boundary conditions, and initialisation techniques used in the community to generate initial states of the Greenland ice sheet. We find good agreement across the ensemble for the dynamic response to surface mass balance changes in areas where the simulated ice sheets overlap but differences arising from the initial size of the ice sheet. The model drift in the control experiment is reduced for models that participated in earlier intercomparison exercises. VL - 12 UR - https://www.the-cryosphere.net/12/1433/2018/ ER - TY - JOUR T1 - A large impact crater beneath Hiawatha Glacier in northwest Greenland JF - Science Advances Y1 - 2018 A1 - Kjær, Kurt H. A1 - Larsen, Nicolaj K A1 - Binder, Tobias A1 - Bjørk, Anders A A1 - Eisen, Olaf A1 - Fahnestock, Mark A A1 - Funder, Svend A1 - Garde, Adam A A1 - Haack, Henning A1 - Helm, Veit A1 - Houmark-Nielsen, Michael A1 - Kjeldsen, Kristian K A1 - Khan, Shfaqat A A1 - Machguth, Horst A1 - McDonald, Iain A1 - Morlighem, Mathieu A1 - Mouginot, Jérémie A1 - Paden, John D A1 - Waight, Tod E A1 - Weikusat, Christian A1 - Willerslev, Eske A1 - MacGregor, Joseph A. AB - We report the discovery of a large impact crater beneath Hiawatha Glacier in northwest Greenland. From airborne radar surveys, we identify a 31-kilometer-wide, circular bedrock depression beneath up to a kilometer of ice. This depression has an elevated rim that cross-cuts tributary subglacial channels and a subdued central uplift that appears to be actively eroding. From ground investigations of the deglaciated foreland, we identify overprinted structures within Precambrian bedrock along the ice margin that strike tangent to the subglacial rim. Glaciofluvial sediment from the largest river draining the crater contains shocked quartz and other impact-related grains. Geochemical analysis of this sediment indicates that the impactor was a fractionated iron asteroid, which must have been more than a kilometer wide to produce the identified crater. Radiostratigraphy of the ice in the crater shows that the Holocene ice is continuous and conformable, but all deeper and older ice appears to be debris rich or heavily disturbed. The age of this impact crater is presently unknown, but from our geological and geophysical evidence, we conclude that it is unlikely to predate the Pleistocene inception of the Greenland Ice Sheet. VL - 4 UR - http://advances.sciencemag.org/ http://advances.sciencemag.org/lookup/doi/10.1126/sciadv.aar8173 ER - TY - JOUR T1 - A synthesis of the basal thermal state of the Greenland Ice Sheet JF - Journal of Geophysical Research: Earth Surface Y1 - 2016 A1 - MacGregor, Joseph A. A1 - Fahnestock, Mark A. A1 - Catania, Ginny A. A1 - Aschwanden, Andy A1 - Clow, Gary D. A1 - Colgan, William T. A1 - Gogineni, S. Prasad A1 - Morlighem, Mathieu A1 - Nowicki, Sophie M. J. A1 - Paden, John D. A1 - Price, Stephen F. A1 - Seroussi, Helene UR - http://doi.wiley.com/10.1002/2015JF003803 ER - TY - JOUR T1 - Radar attenuation and temperature within the Greenland Ice Sheet JF - Journal of Geophysical Research: Earth Surface Y1 - 2015 A1 - MacGregor, Joseph A. A1 - Li, Jilu A1 - Paden, John D A1 - Catania, Ginny a A1 - Clow, Gary D A1 - Fahnestock, Mark A A1 - Gogineni, S Prasad A1 - Grimm, Robert E A1 - Morlighem, Mathieu A1 - Nandi, Soumyaroop A1 - Seroussi, Helene A1 - Stillman, David E VL - 120 UR - http://doi.wiley.com/10.1002/2014JF003418 ER - TY - JOUR T1 - Radiostratigraphy and age structure of the Greenland Ice Sheet JF - Journal of Geophysical Research: Earth Surface Y1 - 2015 A1 - MacGregor, Joseph A. A1 - Fahnestock, Mark A. A1 - Catania, Ginny A. A1 - Paden, John D A1 - Prasad Gogineni, S. A1 - Young, S Keith A1 - Rybarski, Susan C A1 - Mabrey, Alexandria N A1 - Wagman, Benjamin M A1 - Morlighem, Mathieu KW - 10.1002/2014JF003215 and Greenland Ice Sheet KW - ice core KW - ice-penetrating dynamics KW - ice-sheet dynamics VL - 120 UR - http://doi.wiley.com/10.1002/2014JF003215 ER - TY - JOUR T1 - Insights into spatial sensitivities of ice mass response to environmental change from the SeaRISE ice sheet modeling project I: Antarctica JF - J. Geophys. Res. Y1 - 2013 A1 - Nowicki, Sophie A1 - Robert A. Bindschadler A1 - Abe-Ouchi, Ayako A1 - Andy Aschwanden A1 - E. Bueler A1 - Choi, Hyeungu A1 - Fastook, Jim A1 - Granzow, Glen A1 - Greve, Ralf A1 - Gutowski, Gail A1 - Herzfeld, Ute A1 - Jackson, Charles A1 - Jesse V Johnson A1 - Constantine Khroulev A1 - Larour, Eric A1 - Anders Levermann A1 - Lipscomb, William H. A1 - Maria A. Martin A1 - Morlighem, Mathieu A1 - Parizek, Byron R. A1 - David Pollard A1 - Stephen F. Price A1 - Ren, Diandong A1 - Eric Rignot A1 - Fuyuki Saito A1 - Tatsuru Sato A1 - Seddik, Hakime A1 - Seroussi, Helene A1 - Takahashi, Kunio A1 - Walker, Ryan A1 - Wang, Wei Li VL - 118 UR - http://doi.wiley.com/10.1002/jgrf.20081 ER - TY - JOUR T1 - Insights into spatial sensitivities of ice mass response to environmental change from the SeaRISE ice sheet modeling project II: Greenland JF - J. Geophys. Res. Y1 - 2013 A1 - Nowicki, Sophie A1 - Robert A. Bindschadler A1 - Abe-Ouchi, Ayako A1 - Andy Aschwanden A1 - E. Bueler A1 - Choi, Hyeungu A1 - Fastook, Jim A1 - Granzow, Glen A1 - Greve, Ralf A1 - Gutowski, Gail A1 - Herzfeld, Ute A1 - Jackson, Charles A1 - Jesse V Johnson A1 - Constantine Khroulev A1 - Larour, Eric A1 - Anders Levermann A1 - Lipscomb, William H. A1 - Maria A. Martin A1 - Morlighem, Mathieu A1 - Parizek, Byron R. A1 - David Pollard A1 - Stephen F. Price A1 - Ren, Diandong A1 - Eric Rignot A1 - Fuyuki Saito A1 - Tatsuru Sato A1 - Seddik, Hakime A1 - Seroussi, Helene A1 - Takahashi, Kunio A1 - Walker, Ryan A1 - Wang, Wei Li VL - 118 UR - http://doi.wiley.com/10.1002/jgrf.20076 ER -