Large-scale glaciation on Earth and on Mars

This habilitation thesis combines ten publications of the author which are concerned with the large-scale dynamics and thermodynamics of ice sheets and ice shelves. Ice sheets are ice masses with a minimum area of 50,000 km2 which rest on solid land, whereas ice shelves consist of floating ice nourished by the mass flow from an adjacent ice sheet, typically stabilized by large bays. Together, they represent the major part of the cryosphere of the Earth. Furthermore, ice on Earth occurs in the form of glaciers and small ice caps, sea ice, lake ice, river ice, snow and ground ice (permafrost). For Mars, it has long been known that both poles are covered by ice caps which grow and shrink in the course of the seasons, and which leave small residual caps during the respective summer. Recent space-probe missions have revealed that the residual caps are ice sheets in the above sense. Articles 1 and 2 lay the theoretical foundation. Dynamic/thermodynamic model equations for ice sheets and ice shelves are developed, subjected to a scaling analysis, and simplified by assuming small aspect (thickness to width) ratios. The resulting systems of equations are refered to as shallow ice approximation (SIA) and shallow shelf approximation (SSA), respectively. For ice sheets, the computer model SICOPOLIS (SImulation COde for POLythermal Ice Sheets) is introduced, which solves the SIA equations prognostically and three-dimensionally with finite difference methods. Articles 3, 4, 5 deal with paleoclimatic simulations of the Greenland ice sheet over two climatic cycles with the ice-sheet model SICOPOLIS driven by the paleo-temperature record of the GRIP ice core, the attention being focused on the region around Summit, the highest point of the Greenland ice sheet. Simulations which aim at predicting the response of the Greenland ice sheet to future greenhouse warming are the objective of Article 6. For Article 7, the ice-sheet model SICOPOLIS is modified such that it can be applied to model studies of the paleo-glaciation of the entire northern hemisphere. Similar to the Articles 3, 4, 5, simulations over 250,000 years of climate history are carried out, driven by temperature reconstructions of the central Greenland GRIP and the east Antarctic Vostok ice core, respectively. The two-part study of Articles 8, 9 deals with simulations of the Antarctic ice sheet which aim at providing model support for the planned ice core in western Dronning Maud Land within the frame of the European Project for Ice Coring in Antarctica (EPICA). Finally, as an extra-terrestrial application of ice-sheet modelling, Article 10 is concerned with simulations of the permanent north polar H2O ice cap of Mars over the most recent millions of years in response to orbital cycles.