Fall 2014
Colloquia are held on Fridays at 11:30 a.m. in Cullimore Lecture Hall II, unless noted otherwise. Refreshments are served at 11:30 am. For questions about the seminar schedule, please contact Yassine Boubendir.
Date: October 17, 2014
Speaker: John Wettlaufer
Yale University
University of Oxford
Title: "Sea Ice and Climate: A Model System in Stochastic Nonlinear Dynamics"
Abstract:
On any given day newspapers around the world cover climate change, often with a particular focus on the demise of the Arctic ice cover. From the perspective of physical science and mathematics, it is difficult to deny that the Earth's climate system is a complex nonlinear dynamical system. Three main approaches are commonly advanced. (a) Observation of the past and present state of the system and extrapolation to the future. (b) Numerical simulations using General Circulation Models (GCM's) which treat the system with the deterministic approach of a weather forecaster and hence approximate the processes at work on a coarse-grained scale. (c) Evidently due to the ready availability of computing power the approach that has become less favorable is to think about a low-order description of a subsystem of the climate or the entire system. In this talk I focus on the latter and take a tour through a hierarchy of simple, but observationally consistent, nonlinear non autonomous models of the Arctic sea ice cover. In order to understand the role of variability in the decay of the ice I describe an analysis of satellite retrievals, which are the principal geophysical observables of the system. These data provide a starting point for a stochastic treatment of the nonlinear models and open a rich set of challenging questions.