| Date: Friday, March 11, 2011
Title: Stochastic Dynamics of Ice Sheets and Glaciers and the Demise of Deterministic Predictability
Abstract: Since the pioneering work of the great physicists Bragg, Nye and Weertman, glaciers and ice sheets have been treated as thin films of non-Newtonian fluids, deforming slowly over millennia in response to gravitationally induced pressure gradients. However, over the past decade the “continuum†view of glaciers has been challenged by observations showing that ice sheets can undergo relatively rapid changes over daily and shorter timescales. Many of these “fast†changes are associated with the sudden detachment of icebergs from the margins of ice sheets (iceberg calving) and the failure of more traditional continuum models of ice. Incorporating the discrete nature of calving into a continuum model of ice dynamics has proven to be a difficult and vexing problem in glaciology. In this talk, I discuss how methods rooted in statistical physics can be used to deduce macroscopically averaged calving “lawsâ€, valid for any glaciological domain, and that these laws emerge naturally as a large spatial-scale/long temporal-scale limit of an underlying discrete fracture process. An important element of the method developed here is that iceberg calving is treated as a stochastic process and that the probability that an iceberg will detach in a given interval of time can be described by a probability distribution function. The method developed has the potential to provide a physical basis to include iceberg calving into numerical ice sheet models that can be used to produce more realistic estimates of the glaciological contribution to sea level rise in the coming centuries.
Speaker: Jeremy Bassis
Institution: University of Michigan
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