Coupling between wind-driven currents and midlatitude storm tracks

A model for the interaction between the midlatitude ocean gyres and the win d stress is formulated for a shallow-water, spherical hemisphere with finit e thermocline displacement and the latitudinal dependence of the long Rossb y wave speed. The oceanic currents create a temperature front at the midlat itude intergyre boundary that is strongest near the western part of the bas in. The intergyre temperature front affects the atmospheric temperature gra dient in the storm track region, increasing the eddy transport of heat and the surface westerlies. The delayed adjustment of the gyres to the wind str ess causes the westerly maximum to migrate periodically in time with a deca dal period. The behavior of the model in a spherical geometry is qualitativ ely similar to that in a quasigeostrophic setting except that here the coup led oscillation involves oceanic temperature anomalies that circulate aroun d the subpolar gyre, whereas the quasigeostrophic calculations favor the su btropical gyre. Another difference is that here there is a linear relations hip between the period of the coupled oscillation and the delay time for th e adjustment of ocean gyres to changes in the wind stress. This result depa rts from the quasigeostrophic result, in which the advection timescale also influences the period of the decadal oscillation.