| Summary: | Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1999. Includes bibliographical references (p. 231-236). The ice sheets of the last glacial maximum (about 21 thousand years ago) covered a significant fraction of the high latitude land mass, reached up to 3km in height, and had length scales of thousands of kilometers. They represented significant obstacles to the westerly flow of the atmosphere. As the atmospheric flow is forced to deviate around such topographic features, stationary waves-large scale standing patterns in the winds and temperatures-are established within the atmosphere. The largest of the ice sheets, the Laurentide (over North America), was approximately equal in both horizontal extent and height to the Tibetan Plateau, which is known to be a significant contributor to the stationary wave pattern in today's climate. As the ice sheet evolves, the patterns of temperature and winds due to the stationary wave change, and therefore the distribution of precipitation and ablation (melting) is altered over the ice sheet. These altered distributions will, in turn, change the shape of the ice sheet itself, given sufficient time over which to act. It is not possible to integrate full dynamical climate models for the long time scales appropriate to ice sheet dynamics (> 103yrs). Previous studies have typically either used general circulation models (GCMs) for 'snapshot' climate simulations with prescribed ice age insolation and boundary conditions, or used long integrations of energy balance models (EBMs), which do not account for atmospheric dynamics. We aim for an intermediate approach-including some of the important dynamical features of the climate within a framework which is nonetheless simple enough to do long term calculations with. In the most reduced approach, an ice sheet is treated as a perfectly plastic material, lying in the north-south direction. Simple representations of ablation and accumulation show that in equilibrium the ...
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