%0 Journal Article %J The Cryosphere %D 2018 %T Design and results of the ice sheet model initialisation experiments initMIP-Greenland: an ISMIP6 intercomparison %A Goelzer, Heiko %A Nowicki, Sophie %A Edwards, Tamsin %A Beckley, Matthew %A Abe-Ouchi, Ayako %A Aschwanden, Andy %A Calov, Reinhard %A Gagliardini, Olivier %A Gillet-Chaulet, Fabien %A Golledge, Nicholas R. %A Gregory, Jonathan %A Greve, Ralf %A Humbert, Angelika %A Huybrechts, Philippe %A Kennedy, Joseph H. %A Larour, Eric %A Lipscomb, William H. %A Le clec'h, Sébastien %A Lee, Victoria %A Morlighem, Mathieu %A Pattyn, Frank %A Payne, Antony J. %A Rodehacke, Christian %A Rückamp, Martin %A Saito, Fuyuki %A Schlegel, Nicole %A Seroussi, Helene %A Shepherd, Andrew %A Sun, Sainan %A van de Wal, Roderik %A Ziemen, Florian A. %X 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. %B The Cryosphere %V 12 %P 1433–1460 %8 apr %G eng %U https://www.the-cryosphere.net/12/1433/2018/ %R 10.5194/tc-12-1433-2018 %0 Journal Article %J Science Advances %D 2018 %T A large impact crater beneath Hiawatha Glacier in northwest Greenland %A Kjær, Kurt H. %A Larsen, Nicolaj K %A Binder, Tobias %A Bjørk, Anders A %A Eisen, Olaf %A Fahnestock, Mark A %A Funder, Svend %A Garde, Adam A %A Haack, Henning %A Helm, Veit %A Houmark-Nielsen, Michael %A Kjeldsen, Kristian K %A Khan, Shfaqat A %A Machguth, Horst %A McDonald, Iain %A Morlighem, Mathieu %A Mouginot, Jérémie %A Paden, John D %A Waight, Tod E %A Weikusat, Christian %A Willerslev, Eske %A MacGregor, Joseph A. %X 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. %B Science Advances %V 4 %P eaar8173 %8 nov %G eng %U http://advances.sciencemag.org/ http://advances.sciencemag.org/lookup/doi/10.1126/sciadv.aar8173 %R 10.1126/sciadv.aar8173 %0 Journal Article %J Journal of Geophysical Research: Earth Surface %D 2016 %T A synthesis of the basal thermal state of the Greenland Ice Sheet %A MacGregor, Joseph A. %A Fahnestock, Mark A. %A Catania, Ginny A. %A Aschwanden, Andy %A Clow, Gary D. %A Colgan, William T. %A Gogineni, S. Prasad %A Morlighem, Mathieu %A Nowicki, Sophie M. J. %A Paden, John D. %A Price, Stephen F. %A Seroussi, Helene %B Journal of Geophysical Research: Earth Surface %8 jul %G eng %U http://doi.wiley.com/10.1002/2015JF003803 %0 Journal Article %J Journal of Geophysical Research: Earth Surface %D 2015 %T Radar attenuation and temperature within the Greenland Ice Sheet %A MacGregor, Joseph A. %A Li, Jilu %A Paden, John D %A Catania, Ginny a %A Clow, Gary D %A Fahnestock, Mark A %A Gogineni, S Prasad %A Grimm, Robert E %A Morlighem, Mathieu %A Nandi, Soumyaroop %A Seroussi, Helene %A Stillman, David E %B Journal of Geophysical Research: Earth Surface %V 120 %P 983–1008 %8 jun %G eng %U http://doi.wiley.com/10.1002/2014JF003418 %R 10.1002/2014JF003418 %0 Journal Article %J Journal of Geophysical Research: Earth Surface %D 2015 %T Radiostratigraphy and age structure of the Greenland Ice Sheet %A MacGregor, Joseph A. %A Fahnestock, Mark A. %A Catania, Ginny A. %A Paden, John D %A Prasad Gogineni, S. %A Young, S Keith %A Rybarski, Susan C %A Mabrey, Alexandria N %A Wagman, Benjamin M %A Morlighem, Mathieu %K 10.1002/2014JF003215 and Greenland Ice Sheet %K ice core %K ice-penetrating dynamics %K ice-sheet dynamics %B Journal of Geophysical Research: Earth Surface %V 120 %P 212–241 %G eng %U http://doi.wiley.com/10.1002/2014JF003215 %R 10.1002/2014JF003215 %0 Journal Article %J J. Geophys. Res. %D 2013 %T Insights into spatial sensitivities of ice mass response to environmental change from the SeaRISE ice sheet modeling project I: Antarctica %A Nowicki, Sophie %A Robert A. Bindschadler %A Abe-Ouchi, Ayako %A Andy Aschwanden %A E. Bueler %A Choi, Hyeungu %A Fastook, Jim %A Granzow, Glen %A Greve, Ralf %A Gutowski, Gail %A Herzfeld, Ute %A Jackson, Charles %A Jesse V Johnson %A Constantine Khroulev %A Larour, Eric %A Anders Levermann %A Lipscomb, William H. %A Maria A. Martin %A Morlighem, Mathieu %A Parizek, Byron R. %A David Pollard %A Stephen F. Price %A Ren, Diandong %A Eric Rignot %A Fuyuki Saito %A Tatsuru Sato %A Seddik, Hakime %A Seroussi, Helene %A Takahashi, Kunio %A Walker, Ryan %A Wang, Wei Li %B J. Geophys. Res. %V 118 %P 1002–1024 %G eng %U http://doi.wiley.com/10.1002/jgrf.20081 %R 10.1002/jgrf.20081 %0 Journal Article %J J. Geophys. Res. %D 2013 %T Insights into spatial sensitivities of ice mass response to environmental change from the SeaRISE ice sheet modeling project II: Greenland %A Nowicki, Sophie %A Robert A. Bindschadler %A Abe-Ouchi, Ayako %A Andy Aschwanden %A E. Bueler %A Choi, Hyeungu %A Fastook, Jim %A Granzow, Glen %A Greve, Ralf %A Gutowski, Gail %A Herzfeld, Ute %A Jackson, Charles %A Jesse V Johnson %A Constantine Khroulev %A Larour, Eric %A Anders Levermann %A Lipscomb, William H. %A Maria A. Martin %A Morlighem, Mathieu %A Parizek, Byron R. %A David Pollard %A Stephen F. Price %A Ren, Diandong %A Eric Rignot %A Fuyuki Saito %A Tatsuru Sato %A Seddik, Hakime %A Seroussi, Helene %A Takahashi, Kunio %A Walker, Ryan %A Wang, Wei Li %B J. Geophys. Res. %V 118 %P 1025–1044 %8 jun %G eng %U http://doi.wiley.com/10.1002/jgrf.20076 %R 10.1002/jgrf.20076