ON THE ICE-OCEAN RESPONSE TO WIND FORCING

The ice-ocean response to variable winds is analysed based upon two ty pes of models. An analytical ice-ocean model with linear stress laws a nd forced by periodic winds is first derived. Secondly a numerical, ve rtically resolved ice-ocean model is introduced. In the numerical mode l, the ice-water stress law is calculated from a turbulence model and the wind stress is calculated on the basis of a square law formation. By comparing the ice-ocean stress law formulations, it is illustrated that the numerical model predicts an ice-ocean stress law that has a p ower slightly less than 2 compared to 1 for the analytical model. The numerical prediction is in good accordance with field observations and the slight deviation from 2 is due to wall effects close to the ice-w ater interface. It is then demonstrated that the ice-ocean response to variable winds could be well simulated by both models, but the analyt ical model did not capture the wind dependency properly (because of th e linear approach). The ice and current factors are amplified at wind frequencies close to inertial (omega = -f) and damped at high positive and negative frequencies. The maximum ice and current factors at a wi nd frequency equal to the inertial oscillation are shown to be depende nt only on the friction coefficients. With the constants applied in th e present study, the maximum ice drift and current speed are equal to 7.8% and 5.5% of the wind speed, respectively. These steady state valu es are however quite unrealistic as they would require a uniformly cha nging wind direction for many inertial periods.