Ice Sheet, Climate, and Landscape Interactions in Dronning Maud Land, Antarctica

Sammanfattning: The impact of glaciers and ice sheets on the subglacial landscape are of fundamental importance for studies of glacial history and landscape development, both in previously glaciated areas and in areas that are glaciated today. The thesis concerns the present and past erosive capacity of the ice sheet in Dronning Maud Land, East Antarctica. Large-scale subglacial landforms, mainly glacial valleys and cirques, were mapped by radar soundings and basal ice temperatures were calculated. The hypothesis that the alpine landscape in western and central Dronning Maud Land predates the ice sheet was tested. It was found that the ice sheet covering localities at high altitudes within the landscape today are covered by cold-based, and thus non-erosive, ice and that this probably also was the case during late Cenozoic glacial/interglacial cycles. It was concluded that the high-altitude alpine landscape commonly found within the coastal mountain ranges of Dronning Maud Land was formed by local wet-based mountain glaciers during the middle Cenozoic. In the late Cenozoic, the high-altitude alpine landscape has been preserved by cold-based ice coverage. Glacial preservation of a subglacial large-scale sediment accumulation, interpreted as a pre-glacial floodplain or valley delta, was also inferred. Intermediate altitudes within the landscape may have experienced alternating phases of cold-based and wet-based conditions during the late Cenozoic. The lowest parts of the Dronning Maud Land landscape constitute troughs of tectonic origin, exemplified by the prominent Penck-Jutul Trough. In these depressions wet-based conditions have prevailed up to the present day due to the presence of fast flowing ice streams such as Jutulstraumen and Veststraumen. Ice stream erosion has probably been important for the continued deepening of these troughs, and it is feasible that erosion by ice streams today still increases the already significant landscape relief. The alpine landscape of Dronning Maud Land is incised in considerably older large-scale morphology consisting of an elevated Paleozoic planation surface and a passive continental margin escarpment. An attempt is made to synthesise major events in the long-term landscape development of central and western Dronning Maud Land since the time of break-up of the Gondwana continent. The role of glacial erosion in the development of this passive continental margin is assessed.