Evidence for the maintenance of slowly varying equatorial currents by intraseasonal variability

Greatbatch, Richard John, Claus, Martin, Brandt, Peter, Matthießen, Jan-Dirk, Tuchen, Franz Philip, Ascani, François, Dengler, Marcus, Toole, John, Roth, Christina and Farrar, J. Thomas (2018) Evidence for the maintenance of slowly varying equatorial currents by intraseasonal variability Geophysical Research Letters, 45 (4). pp. 1923-1929. DOI 10.1002/2017GL076662.

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Abstract

Recent evidence from mooring data in the equatorial Atlantic reveals that semi-annual and longer time scale ocean current variability is close to being resonant with equatorial basin modes. Here we show that intraseasonal variability, with time scales of 10's of days, provides the energy to maintain these resonant basin modes against dissipation. The mechanism is analogous to that by which storm systems in the atmosphere act to maintain the atmospheric jet stream. We demonstrate the mechanism using an idealised model set-up that exhibits equatorial deep jets. The results are supported by direct analysis of available mooring data from the equatorial Atlantic Ocean covering a depth range of several thousand meters. The analysis of the mooring data suggests that the same mechanism also helps maintain the seasonal variability.

Document Type: Article
Keywords: equatorial deep jets; seasonal cycle; momentum flux convergence; tropical instability waves; equatorial basin mode resonance
Research affiliation: OceanRep > SFB 754 > A9
OceanRep > SFB 754 > A4
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
Woods Hole
OceanRep > SFB 754
Kiel University
Refereed: Yes
DOI etc.: 10.1002/2017GL076662
ISSN: 0094-8276
Projects: SFB754, RACE, SACUS, MiKlip, PREFACE, PIRATA
Date Deposited: 12 Feb 2018 12:37
Last Modified: 16 Mar 2018 09:24
URI: http://eprints.uni-kiel.de/id/eprint/41896

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