On low-frequency variability of the midlatitude ocean gyres

This paper studies the large-scale low-frequency variability of the wind-driven midlatitude ocean gyres and their western boundary currents, such as the Gulf Stream or Kuroshio, simulated with the eddy-resolving quasi-geostrophic model. We applied empirical orthogonal functions analysis to turbulent...

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Hauptverfasser: Shevchenko, I. V, Berloff, P. S, Guerrero López, David, Román Moltó, José Enrique
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Sprache:eng
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Zusammenfassung:This paper studies the large-scale low-frequency variability of the wind-driven midlatitude ocean gyres and their western boundary currents, such as the Gulf Stream or Kuroshio, simulated with the eddy-resolving quasi-geostrophic model. We applied empirical orthogonal functions analysis to turbulent flow solutions and statistically extracted robust and significant large-scale decadal variability modes concentrated around the eastward jet extension of the western boundary currents. In order to interpret these statistical modes dynamically, we linearized the governing quasi-geostrophic equations around the time-mean circulation and solved for the corresponding full set of linear eigenmodes with their eigenfrequencies. We then projected the extracted decadal variability on the eigenmodes and found that this variability is a multimodal coherent pattern phenomenon rather than a single mode or a combination of several modes as in the flow regimes preceding developed turbulence. The first two authors are thankful to the Natural Environment Research Council for the support of this work through the grant NE/J006602/1 and the use of ARCHER (the UK National Supercomputing Service). We express our gratitude to S. Burbidge and M. Harvey for their help with Imperial College London cluster, as well as to A. Thomas for his help with managing and maintaining the data storage. The last two authors were supported by the Spanish Ministry of Economy and Competitiveness under grant TIN2013-41049-P, and this support is gratefully acknowledged. We would also like to thank unknown referees for valuable comments and suggestions, which helped us to improve the paper. Shevchenko, IV.; Berloff, PS.; Guerrero López, D.; Román Moltó, JE. (2016). On low-frequency variability of the midlatitude ocean gyres. Journal of Fluid Mechanics. 795:423-442. https://doi.org/10.1017/jfm.2016.208