The Importance of History for Predicting the Future of the West Antarctic Ice Sheet

The West Antarctic Ice Sheet (WAIS) initiative began in 1990, following on earlier studies of the 'Siple Coast' ice streams and the Ross Ice Shelf. The past nearly two decades of field and satellite research of the West Antarctic ice sheet have produced an astounding number of discoveries, not the least of which is the variability of the West Antarctic ice sheet on time scales from seconds (yes, seconds!) to many millennia. The shorter-time-scale variations, such as the recent acceleration and thinning of glaciers draining into the Amundsen Sea, have illustrated serious weaknesses in what were once regarded as excellent models of ice sheet dynamics. Repairing this modeling capability requires understanding and incorporating external and internal processes previously regarded as less important. Ice-sheet history remains the best means to test, tune and validate numerical models of ice sheets. Cenozoic-age behavior may seem too ancient to matter to a centennial-time-scale focus on the future, but it is precisely through a long history, that the variety of more extreme ice sheet configurations can be extracted. Such upper or lower bound estimates have served the WAIS community well over the years to help justify research needed to assess the probability of dramatic behavior. Now, with the necessity of model revisions central to the WAIS effort, time histories of ice sheet behavior over both short and long time scales will return to a position of extreme importance.