An idealized modeling study of the mid-latitude variability of the wind-driven meridional overturning circulation

Abstract The frequency and latitudinal dependence of the mid-latitude wind-driven meridional overturning circulation (MOC) is studied using theory linear nonlinear applications a quasi-geostrophic numerical model. Wind-forcing varied by either changing strength wind or shifting location stress curl pattern. At forcing periods less than first mode baroclinic Rossby wave basin crossing time scale response in mid-depth deep ocean phase opposite to Ekman transport. For close scale, upper MOC are enhanced, becomes shifted, relative longer weakens increases, but eventually for long enough (decadal) entire spins down. Nonlinearities mesoscale eddies found be important two ways. First, instability causes weaken, lose correlation with transport, gyre. Second, eddy thickness fluxes extend beyond latitudes direct forcing. These results consistent several recent studies describing four-dimensional structure North Atlantic.