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

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Greatbatch, Richard J.
Claus, Martin
Brandt, Peter
Matthießen, Jan-Dirk
Tuchen, Franz Philip
Ascani, Francois
Dengler, Marcus
Toole, John M.
Roth, Christina
Farrar, J. Thomas
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Equatorial deep jets
Seasonal cycle
Momentum flux convergence
Tropical instability waves
Equatorial basin mode resonance
Recent evidence from mooring data in the equatorial Atlantic reveals that semiannual 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 tens 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 idealized model setup 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.
© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geophysical Research Letters 45 (2018): 1923–1929, doi:10.1002/2017GL076662.
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Geophysical Research Letters 45 (2018): 1923–1929
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