Pacific Institute for the Mathematical Sciences - PIMS

Whither Arctic Sea Ice: Nonlinear Threshold Behavior, Stochastic Dynamics and Recurrence Texture

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. 

3:00pm-4:00pm, LSK 301

This is the 4th lecture of the 2010-11 IAM-PIMS-MITACS
Distinguished Colloquium Series. For full details, visit:

http://www.iam.ubc.ca.