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Isopycnal eddy diffusivities and critical layers in the Kuroshio Extension from an eddying ocean model

TitleIsopycnal eddy diffusivities and critical layers in the Kuroshio Extension from an eddying ocean model
Publication TypeJournal Article
Year of Publication2014
AuthorsChen R., McClean JL, Gille ST, Griesel A.
JournalJournal of Physical Oceanography
Date Published2014/08
Type of ArticleArticle
ISBN Number0022-3670
Accession NumberWOS:000340349800014
Keywordsantarctic circumpolar current; coherent structures; general-circulation; gulf-stream; jet; mean-flow; north-atlantic; southern-ocean; transport; variability

High spatial resolution isopycnal diffusivities are estimated in the Kuroshio Extension (KE) region (28 degrees-40 degrees N, 120 degrees-190 degrees E) from a global 1/10 degrees Parallel Ocean Program (POP) simulation. The numerical float tracks are binned using a clustering approach. The number of tracks in each bin is thus roughly the same leading to diffusivity estimates that converge better than those in bins defined by a regular geographic grid. Cross-stream diffusivities are elevated in the southern recirculation gyre region, near topographic obstacles and downstream in the KE jet, where the flow has weakened. Along-stream diffusivities, which are much larger than cross-stream diffusivities, correlate well with the magnitudes of eddy velocity. The KE jet suppresses cross-stream mixing only in some longitude ranges. This study estimates the critical layer depth both from linear local baroclinic instability analysis and from eddy phase speeds in the POP model using the Radon transform. The latter is a better predictor of large mixing length in the cross-stream direction. Critical layer theory is most applicable in the intense jet regions away from topography.

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