@article {Kiaer2018, title = {{A large impact crater beneath Hiawatha Glacier in northwest Greenland}}, journal = {Science Advances}, volume = {4}, number = {11}, year = {2018}, month = {nov}, pages = {eaar8173}, abstract = {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.}, issn = {23752548}, doi = {10.1126/sciadv.aar8173}, url = {http://advances.sciencemag.org/ http://advances.sciencemag.org/lookup/doi/10.1126/sciadv.aar8173}, author = {Kj{\ae}r, Kurt H. and Larsen, Nicolaj K and Binder, Tobias and Bj{\o}rk, Anders A and Eisen, Olaf and Fahnestock, Mark A and Funder, Svend and Garde, Adam A and Haack, Henning and Helm, Veit and Houmark-Nielsen, Michael and Kjeldsen, Kristian K and Khan, Shfaqat A and Machguth, Horst and McDonald, Iain and Morlighem, Mathieu and Mouginot, J{\'e}r{\'e}mie and Paden, John D and Waight, Tod E and Weikusat, Christian and Willerslev, Eske and MacGregor, Joseph A.} } @article {MacGregor2015b, title = {{Radar attenuation and temperature within the Greenland Ice Sheet}}, journal = {Journal of Geophysical Research: Earth Surface}, volume = {120}, number = {6}, year = {2015}, month = {jun}, pages = {983{\textendash}1008}, issn = {21699003}, doi = {10.1002/2014JF003418}, url = {http://doi.wiley.com/10.1002/2014JF003418}, author = {MacGregor, Joseph A. and Li, Jilu and Paden, John D and Catania, Ginny a and Clow, Gary D and Fahnestock, Mark A and Gogineni, S Prasad and Grimm, Robert E and Morlighem, Mathieu and Nandi, Soumyaroop and Seroussi, Helene and Stillman, David E} } @article {MacGregor2015, title = {{Radiostratigraphy and age structure of the Greenland Ice Sheet}}, journal = {Journal of Geophysical Research: Earth Surface}, volume = {120}, year = {2015}, pages = {212{\textendash}241}, keywords = {10.1002/2014JF003215 and Greenland Ice Sheet, ice core, ice-penetrating dynamics, ice-sheet dynamics}, issn = {21699003}, doi = {10.1002/2014JF003215}, url = {http://doi.wiley.com/10.1002/2014JF003215}, author = {MacGregor, Joseph A. and Fahnestock, Mark A. and Catania, Ginny A. and Paden, John D and Prasad Gogineni, S. and Young, S Keith and Rybarski, Susan C and Mabrey, Alexandria N and Wagman, Benjamin M and Morlighem, Mathieu} }