Low-frequency variability enhancement of the midlatitude climate in an eddy-resolving, coupled ocean-atmosphere model. Part I: Anatomy [post]

Ryosuke Kurashina, Pavel Berloff
2022 unpublished
This study investigated coupling of the wind-driven ocean gyres with the atmospheric westerly jet, or jet stream, using an idealised, eddy-resolving, coupled ocean-atmosphere model. An empirical orthogonal function analysis showed that the ocean gyre variability is dominated by meridional shifts of the eastward jet extension and changes in strength of the subtropical inertial recirculation zone. On the other hand, the atmospheric jet variability is shown to be dominated by the growth of
more » ... Rossby wave patterns which are enhanced by the presence of western boundary currents and a sharp sea surface temperature (SST) front. Singular value decompositions of the low-pass filtered data revealed positive feedbacks between meridional shifts of the ocean eastward jet extension and the growth of a standing Rossby wave disturbances in the atmospheric jet. The response of the atmosphere is controlled by shifts in meridional eddy heat fluxes which are co-located with the SST front and trigger the growth of baroclinic instabilities over the ocean basin. This eventually leads to a large-scale, barotropic circulation response in the atmosphere over the eastern ocean basin. Reduction in the atmospheric resolution inhibits the ability of atmospheric eddies to resolve length scales associated with meridional shifts of the SST front and eastward jet. This consequently weakens the influence of ocean gyre variability on the atmospheric jet and reduces the strength of the positive feedback.
doi:10.21203/rs.3.rs-2207293/v1 fatcat:via2e7h7azdrne7ggmrsumqtf4