An intrinsic mode of interannual variability in the Indian Ocean

TitleAn intrinsic mode of interannual variability in the Indian Ocean
Publication TypeJournal Article
Year of Publication2017
AuthorsWolfe CL, Cessi P, Cornuelle BD
JournalJournal of Physical Oceanography
Volume47
Pagination701-719
Date Published2017/03
Type of ArticleArticle
ISBN Number0022-3670
Accession NumberWOS:000397574000014
Keywordsatlantic; circulation
Abstract

An intrinsic mode of self-sustained, interannual variability is identified in a coarse-resolution ocean model forced by an annually repeating atmospheric state. The variability has maximumloading in the Indian Ocean, with a significant projection into the South Atlantic Ocean. It is argued that this intrinsic mode is caused by baroclinic instability of the model's Leeuwin Current, which radiates out to the tropical Indian and South Atlantic Oceans as long Rossby waves at a period of 4 yr. This previously undescribed mode has a remarkably narrowband time series. However, the variability is not synchronized with the annual cycle; the phase of the oscillation varies chaotically on decadal time scales. The presence of this internal mode reduces the predictability of the ocean circulation by obscuring the response to forcing or initial condition perturbations. The signature of this mode can be seen in higher-resolution global ocean models driven by high-frequency atmospheric forcing, but altimeter and assimilation analyses do not show obvious signatures of such a mode, perhaps because of insufficient duration.

DOI10.1175/jpo-d-16-0177.1
Student Publication: 
No