Multidecadal Variability of the Overturning Circulation in Presence of Eddy Turbulence

摘要: At low-resolution, idealized ocean circulation models forced by prescribed differential surface heat fluxes show spontaneous multidecadal variability depending critically on eddy diffusivity coefficients. The existence of this critical threshold in the range observational estimates legitimates some doubt relevance such intrinsic oscillations real ocean. Through a series numerical simulations with increasing resolution up to eddy-resolving ones (10 km) and various diapycnal diffusivities, proves generic ubiquitous feature, at least model versions flat bottom. mean largely changes process refining horizontal grid (along associated implicit viscosity diffusivity), spatial structure is modified, but there no clear influence main oscillation period. interdecadal appears even more robust low vertical overturning when mesoscale eddies are resolved. mechanism previously proposed for these oscillations, involving westward-propagating baroclinically unstable Rossby waves subpolar region its feedback circulation, unaffected turbulence simply displaced following polar front.