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Surface Signature of Mediterranean Water Eddies in the Northeastern Atlantic: Effect of the Upper Ocean Stratification : Volume 8, Issue 6 (01/11/2012)

By Bashmachnikov, I.

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Book Id: WPLBN0004020622
Format Type: PDF Article :
File Size: Pages 13
Reproduction Date: 2015

Title: Surface Signature of Mediterranean Water Eddies in the Northeastern Atlantic: Effect of the Upper Ocean Stratification : Volume 8, Issue 6 (01/11/2012)  
Author: Bashmachnikov, I.
Volume: Vol. 8, Issue 6
Language: English
Subject: Science, Ocean, Science
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Publication Date:
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications


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Bashmachnikov, I., & Carton, X. (2012). Surface Signature of Mediterranean Water Eddies in the Northeastern Atlantic: Effect of the Upper Ocean Stratification : Volume 8, Issue 6 (01/11/2012). Retrieved from

Description: Institute of Oceanography of the Faculty of Sciences of the University of Lisbon (OI-FCUL), Campo Grande, 1749-016, Lisbon, Portugal. Meddies, intra-thermocline eddies of Mediterranean water, can often be detected at the sea surface as positive sea-level anomalies. Here we study the surface signature of several meddies tracked with RAFOS floats and AVISO altimetry.

While pushing its way through the water column, a meddy raises isopycnals above. As a consequence of potential vorticity conservation, negative relative vorticity is generated in the upper layer. During the initial period of meddy acceleration after meddy formation or after a stagnation stage, a cyclonic signal is also generated at the sea-surface, but mostly the anticyclonic surface signal follows the meddy.

Based on geostrophy and potential vorticity balance, we present theoretical estimates of the intensity of the surface signature. It appears to be proportional to the meddy core radius and to the Coriolis parameter, and inversely proportional to the core depth and buoyancy frequency. This indicates that surface signature of a meddy may be strongly reduced by the upper ocean stratification. Using climatic distribution of the stratification intensity, we claim that the southernmost limit for detection in altimetry of small meddies (with radii on the order of 10–15 km) should lie in the subtropics (35–45° N), while large meddies (with radii of 25–30 km) could be detected as far south as the northern tropics (25–35° N). Those results agree with observations.

Surface signature of Mediterranean water eddies in the Northeastern Atlantic: effect of the upper ocean stratification

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