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Free Content Meddy, spiral arms, and mixing mechanisms viewed by seismic imaging in the Tagus Abyssal Plain (SW Iberia)

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Seismic imaging of the water column is used to investigate the relative roles of thermohaline intrusive mixing and stirring (straining and shearing) by mesoscale eddies in the NE Atlantic, in and around a Meddy, and in waters between the Meddy and the coast of Portugal. The images show that mixing is virtually absent within the core but anomalously high in the top, bottom, and surrounding frontal region, as previously found by conventional means. In the immediate periphery of the Meddy, bands of water with numerous reflectors consistent with thermohaline intrusions, and with anomalously high mixing rate can be seen. We suggest these may be “spiral arms” of water that was removed from the Meddy periphery by instability or external stirring.

The region between the Meddy and the Portuguese continental slope was also imaged, and shows numerous reflectors with relatively small slope and strength similar to the reflectors found in the Meddy periphery. This is in contrast to the predictions of individual thin filaments of slope O(f/N) by Smith and Ferrari (2009), and we suggest that eddy stirring in this region produces thermohaline fronts that are acted upon by thermohaline intrusions. Therefore, the cascade of thermal variance to microscale dissipation could involve a partnership between eddy stirring and thermohaline intrusions.

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Document Type: Research Article

Publication date: 2011-07-01

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  • The Journal of Marine Research publishes peer-reviewed research articles covering a broad array of topics in physical, biological and chemical oceanography. Articles that deal with processes, as well as those that report significant observations, are welcome. In the area of biology, studies involving coupling between ecological and physical processes are preferred over those that report systematics. Authors benefit from thorough reviews of their manuscripts, where an attempt is made to maximize clarity. The time between submission and publication is kept to a minimum; there is no page charge.
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