On the width of the equatorial deep jets and the impact of the barotropic mean flow.

Claus, Martin , Greatbatch, R. J. , Brandt, Peter and Didwischus, Sven-Helge (2013) On the width of the equatorial deep jets and the impact of the barotropic mean flow. [Talk] In: Tropical Atlantic Variability Meeting / PIRATA-18 Meeting . , 22. - 25.10.2013, Venice, Italy .

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Abstract

The equatorial deep jets (EDJ) are a striking feature of the equatorial ocean circulation. In the Atlantic Ocean, the EDJ are associated with
a vertical scale of between 300 and 700 m, a time scale of roughly 4.5 years and upward energy propagation to the surface and thus are contributing to the interannual climate variability in the equatorial Atlantic region. However, it has been found that the meridional width of the EDJ is roughly 1.5 times larger than expected based on their vertical scale. Here a representation of a equatorial basin mode excited in a shallow water model for a single high order baroclinic vertical normal mode is used as a simple model for the EDJ. The model is linearised about both a state of rest and a barotropic mean flow resembling the Atlantic Equatorial Intermediate Current System with eastward flow at roughly 2◦ N and 2◦ S and westward flow in between and poleward of it. We argue that mixing of momentum along isopycnals can explain the enhanced width and a lateral
eddy viscosity of 300 m^2 s−1 is found to be sufficient to account for the width implied by observations. The underlying eastward mean flow effectively shields the equator from off-equatorial Rossby waves, blocking the westward propagation of these waves that are generated by the reflection of equatorial Kelvin waves at the eastern boundary.

Document Type: Conference or Workshop Item (Talk)
Keywords: EDJ ; Equatorial Deep Jets; tropical Atlantic; barotropic mean flow ; SFB754 ; equator; equatorial current
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-TM Theory and Modeling
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
Date Deposited: 08 Nov 2013 10:06
Last Modified: 08 Nov 2013 10:06
URI: http://oceanrep.geomar.de/id/eprint/22362

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