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Free Content Lagrangian eddy statistics from surface drifters in the eastern North Atlantic

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In 1976–1977, 16 surface drifters were seeded regularly in an area about 100 km in diameter, providing a good opportunity to study diffusion induced by the mesoscale eddies present in this part of the eastern North Atlantic. It is found herein that Taylor's formula relating the diffusivity (rate of dispersion) of marked fluid parcels to the integral of the Lagrangian correlation function is accurate up to 30 days. The diffusivity, initially zero, reaches a plateau after about 10 days. The diffusivities associated with the time scale of the energy containing eddies (30 days) are 2.3 107 cm2/s and 1.7 107 cm2/s in the zonal and meridional direction respectively. This is small in view of the surface eddy kinetic energy of the order of 100 cm2/s2. Accordingly the Lagrangian integral time scales are as short as 2 days. After 30 days, the diffusivity decreases and the dispersion saturates. The Lagrangian eddy energy content is therefore weak at low frequencies in contrast with subsurface Eulerian energy content obtained in the same area. The center of gravity of the Lagrangian and Eulerian energy spectrum indicates time scales respectively of 12 and 26 days. At frequencies higher than 0.1 cpd the Lagrangian velocity spectrum falls off with a −2 slope. This may be an indication of a balance between the Lagrangian acceleration of water parcels and the essentially white noise wind stress computed from a nearby weathership. Eulerian spectra at greater depths which had a similar −2 slope in this band but a much reduced energy level suggest an oceanic response strongly trapped at the surface.

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Document Type: Research Article

Publication date: August 1, 1983

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  • The Journal of Marine Research, one of the oldest journals in American marine science, 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. Biological studies involving coupling between ecological and physical processes are preferred over those that report systematics. The editors strive always to serve authors and readers in the academic oceanographic community by publishing papers vital to the marine research in the long and rich tradition of the Sears Foundation for Marine Research. We welcome you to the Journal of Marine Research.
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