Observed mean and mesoscale upper ocean circulation in the midlatitude northeast Atlantic

Type Article
Date 2005-07
Language English
Author(s) Le Cann Bernard1, 4, Assenbaum Michel2, Gascard Jean-Claude3, Reverdin Gilles3
Affiliation(s) 1 : Univ Bretagne Occidentale, UFR Sci, Inst Francais Rech Exploitat Mer, CNRS,Lab Phys Oceans, F-29238 Brest, France.
2 : Bur Rech & Etud SHOM Meteo, Lab Etud Geophys & Oceanog Spatiales, F-31400 Toulouse, France.
3 : Univ Paris 06, Lab Oceanog Dynam & Climatol, F-75252 Paris, France.
Source Journal of Geophysical Union - Research C - Oceans (0148-0227) (American Geophysical Union), 2005-07 , Vol. 110 , N. C7 , P. NIL_30-NIL_59
DOI 10.1029/2004JC002768
WOS© Times Cited 27
Keyword(s) Altimetry, Drifting buoys, Acoustic floats, Lagrangian circulation, Mesoscale eddies, Northeastern Atlantic
Abstract Lagrangian instruments and altimetry data are used to investigate the upper ( 0 to similar to 500 m) mean and mesoscale circulations in a region of the midlatitude northeast Atlantic (36 degrees - 47 degrees N, 13 degrees - 23 degrees W), a formation and subduction area of Subpolar Mode Water. Lagrangian data were collected between September 2000 and September 2001 with isobaric subsurface floats, totaling 34.0 float years, and surface drifting buoys, totaling 27.9 buoy years. The near-surface ( 0 - 100 m) mean circulation is dominated by two weak ( similar to 5 cm/s) eastward currents which veer southward in the domain. In the 100- to 500-m-deep layer, these eastward mean currents retroflect westward and form two anticyclonic circulation cells, opened to the west and separated by a cyclonic cell. Eddy kinetic energy is decreasing from the northwest to the southeast of the area, from similar to 100-200 (cm/s)(2) to similar to 20 - 30 (cm/s)(2). Long-lived anticyclones and cyclones display mean coherent displacements, both to the southwest. Westward eddy propagation speeds, close to that of long Rossby waves, increase southward and are consistent with a superposition of beta effect and advection by mean currents. Southward eddy displacements are coherent with the observed mean currents. In the north, anticyclones are seen to consist of Central and Subpolar Mode Water eddies, most of them likely originating from the eastern boundary, whereas in the south, most anticyclonic features result from the influence of "Mediterranean Water Eddies'' (meddies) on the upper layers. Cyclonic activity is concentrated in "cyclonic zones,'' which are seen to exchange floats and water properties.
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Le Cann Bernard, Assenbaum Michel, Gascard Jean-Claude, Reverdin Gilles (2005). Observed mean and mesoscale upper ocean circulation in the midlatitude northeast Atlantic. Journal of Geophysical Union - Research C - Oceans, 110(C7), NIL_30-NIL_59. Publisher's official version : https://doi.org/10.1029/2004JC002768 , Open Access version : https://archimer.ifremer.fr/doc/00000/745/