Interactions between ice sheets and atmospheric circulation during ice ages

The last glacial period is characterized by the presence of two large ice sheets covering Canada and North Eurasia. These ice sheets are a key element of the climatic system by interacting with all the components of the Earth system. The aim of this thesis is to determine by which mechanisms changes in atmospheric circulation may have induced a teleconnection between the Northern hemisphere paleo-ice sheets. The use of a simplified coupled climate-ice sheet model allowed to test separately the influence of the ice-sheet topography and albedo on temperature and precipitation fields throughout the last glacial cycle and to highlight the role of atmospheric circulation within the synergy of past boreal ice sheets. To investigate in more details the underlying mechanisms, the use of a general circulation model was necessary. I therefore carried out an inter-comparison of the PMIP3 models to examine the GCM responses to glacial conditions. This work allowed to determine the role of glacial conditions on the shift of the North Atlantic jet stream position and to establish a relationship between this shift and the amount of precipitation over southern Europe. The last part of this thesis is devoted to the respective role of each ice sheet on atmospheric circulation changes observed under glacial conditions. To achieve this, I performed idealized experiments with the atmospheric circulation model LMDZ. The results highlight the key influence of the North American ice sheet on the Eurasian ice sheet surface mass balance. (author)