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 - Modelled glacier dynamics over the last quarter of a century at Jakobshavn Isbræ JF - The Cryosphere Y1 - 2016 A1 - Muresan, Ioana S. A1 - Khan, Shfaqat A. A1 - Aschwanden, Andy A1 - Khroulev, Constantine A1 - Van Dam, Tonie A1 - Bamber, Jonathan A1 - van den Broeke, Michiel R. A1 - Wouters, Bert A1 - Kuipers Munneke, Peter A1 - Kjær, Kurt H. VL - 10 UR - http://www.the-cryosphere.net/10/597/2016/ ER - TY - JOUR T1 - Greenland ice sheet mass balance JF - Reports on Progress in Physics Y1 - 2015 A1 - Khan, Shfaqat A. A1 - Aschwanden, Andy A1 - Bjørk, Anders A A1 - Whar, John A1 - Kjeldsen, Kristian K. A1 - Kjær, Kurt H. AB - Mass balance equation for glaciers; areal distribution and ice volumes; estimates of actual mass balance; loss by calving of icebergs; hydrological budget for Greenland; and temporal variations of Greenland mass balance are examined. PB - IOP Publishing VL - 78 UR - http://dx.doi.org/10.1088/0034-4885/78/4/046801 ER -