IAM-PIMS-MITACS Distinguished Colloquium Series: John Wettlaufer (Yale University)

In light of the rapid recent retreat of Arctic sea ice, a number of studies have discussed the possibility of a critical threshold beyond which the ice-albedo feedback causes the ice cover to melt away in an irreversible process. The focus has typically been centered on the annual minimum (September) ice cover, which is often seen as particularly susceptible to destabilization by the ice-albedo feedback. Here, I examine the central physical processes associated with the transition from ice-covered to ice-free Arctic Ocean conditions using a simple nonautonomous ODE that reproduces the systems principal observables. While the ice-albedo feedback does indeed promote the existence of multiple ice-cover states, the stabilizing thermodynamic effects of sea ice mitigate this when the Arctic Ocean is ice covered during a sufficiently large fraction of the year. Whence, threshold behavior is unlikely during the approach from current perennial sea- ice conditions to seasonally ice-free conditions. However, a further warmed climate exhibits a sudden loss of the remaining wintertime-only sea ice cover via a saddle-node bifurcation. Using a stochastic approach to the same basic theory it is found that there is an asymmetry in the dwell times between ice free and ice covered states questioning the utility of using satellite data to extrapolate information from one year to the next. This latter issue of predictability using observations is addressed by extracting the embedding dimension and examining the recurrence texture of this satellite data.

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John Wettlaufer is an A. M. Bateman Professor of Geophysics and Physics and a Professor of Applied Mathematics at Yale University. His work is best described as a hybrid between condensed matter theory and experiment, materials physics, and applied mathematics with applications focusing on environmental, geophysical and technological problems. Of particular interest is the growth of ice from vapor, pure and binary melts, phase-antiphase boundary migration, and the role of surface melting in the migration of negative crystals, grain boundaries, and as an underlying cause of frost heave. John has been a frequent participant in the Geophysical Fluid Dynamics Summer Program at Woods Hole and in the Geophysical and Environmental Fluid Dynamics Summer School at the Department of Applied Mathematics and Theoretical Physics, University of Cambridge.