Extended Abstract (180K)3a.9
On the Response of the Arctic Ocean ice thickness distribution to changes in external forcing
PAPER WITHDRAWN
Johan Söderkvist, Göteborg University, Göteborg, Sweden; and G. Bjork
The sensitivity of the Arctic Ocean ice cover to the atmospheric poleward energy flux, D, is studied using a coupled column model of the ocean, ice, and atmosphere. In the model, the ice cover is described by a thickness distribution and the atmosphere is a simple two stream grey body, in radiative equilibrium. It is shown that the thickness distribution in combination with the albedo function gives a strong nonlinear response to positive perturbations of D. The response on D is sensitive to the albedo parameterization and the shape of the thickness distribution, controlled by ridging and divergence. An increase of 9 W m-2 from a standard value of D=103 W m-2 has a dramatic effect, reducing the ice thickness with more than 2 m and generates a large open water fraction during summer. The reduction of ice thickness is characterized by a clear transition between two regimes, going from a regime where first year ice survives the next summer melt period, to a regime where the first year ice melts completely. The adjustment time scale of the ice cover towards a new equilibrium is 6 years for negative and small positive perturbations of D. For larger positive perturbations the adjustment take up to 20 years. A somewhat speculative conclusion is that even if the high sensitivity of the ice cover on D may result in quite large changes of the ice thickness, a feedback on the poleward energy flux prevents the ice cover to reach extreme states with very much thinner or thicker ice.
Session 3a, Sea Ice Properties: Observed and Modeled: Continued (Parallel with Session 3B)
Thursday, 17 May 2001, 10:30 AM-11:34 AM
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