A GCM study of Antarctic glaciation

An atmospheric general circulation model, the NCAR CCM, has been used to investigate the possible effects of two specific tectonic mechanisms on Antarctic glaciation. These two mechanisms are: (1) closing the Drake Passage (connecting South America with Antarctica), which is assumed to effectively represent an increased meridional heat transport by the ocean; and (2) changing the elevation of Antarctica. Perpetual season (summer and winter) and seasonal cycle simulations with warmer sea-surface temperatures and no sea ice prescribed for mid- to high-latitude southern oceans have been made with both present-day (high) Antarctic elevations and with low Antarctic elevations (all points 200 m). The results suggest a relatively minor role for oceanic heat transport in the formation/elimination of Antarctic glaciation. That is, under the warmer conditions inferred to have prevailed prior to the opening of the Drake Passage, conditions would still have been favorable for the maintenance of an Antarctic ice-sheet. If anything, a moderate ocean warming would promote glaciation, by increasing snowfall. Lowering the elevation of Antarctica has a larger effect on the model simulations, reducing the likelihood of glacial conditions. In the absence of snowcover, summer temperatures over Antarctica can warm considerably, leading to a monsoon-like circulation. However, it may be difficult to achieve such snow-free conditions, even with greatly increased atmospheric carbon dioxide. A tundra-like climate is the closest the model has come to representing a non-glacial climate, even when both seasurface temperatures and elevations are maximally varied.