High-resolution observations of a dual-core anticyclonic eddy in the Algerian Basin (PROTEVS-MED 2016)

Date 2018
Temporal extent 2016-03-01 -2016-05-31
Author(s) Louazel Stephanie1, Dumas Franck1, Garreau PierreORCID2
Affiliation(s) 1 : SHOM, Service Hydrographique et Océanographique de la Marine, 13 rue de Chatellier, CS592803, 29228 Brest CEDEX2, France
2 : IFREMER, Univ. Brest, CNRS UMR 6523, IRD, Laboratoire d'Océanographie Physique et Spatiale (LOPS), IUEM, 29280, Plouzané, France
DOI 10.17882/56028
Publisher SEANOE
Keyword(s) Algerian Eddy, High resolution transects, Seasoar, Anticyclonic Eddy, North Balearic Front, Sub-mesoscale Observations
Abstract

Mesoscale dynamics in the Mediterranean Sea have been investigated for years and anticyclonic eddies are regularly observed features in the Algerian Basin. In early spring 2016, a field experiment during the ProtevsMed 2016 cruise thoroughly investigated this specific eddy, when it was located near the North Balearic Front, taking high-resolution (Seasoar) hydrological transects, several CTD casts and LADCP measurements. In addition, four drifting buoys were released in the eddy core. These in situ measurements revealed that the vertical structure of this anticyclone was made of two water lenses of very different origins (Atlantic Water above and Western Intermediate Water below) spinning together. In the vicinity of the North Balearic Front, which may act as a dynamical barrier for structures, the eddy interacted with a subsurface anticyclonic eddy made of modal water, which fostered cross-front exchanges generating filaments by stirring. The high-resolution sampling revealed fine scales structures both adjacent to the eddy and within its core.

The eddy has been targeted from 21 March to 1 April 2016 taking advantage of a meteorological window. It has been sampled with: 


  • a towed undulating vehicle, the SeaSoar designed and built by Chelsea Instruments; it gets mounted on its sides two Sea-bird SBE-9 (SBE 3 temperature and SBE 4 conductivity sensors)  and a Wetlabs Fluorometer of type ChloroA WetStar 

  • CTD casts performed with a Sea-bird SBE-9 (SBE 3 temperature and SBE 4 conductivity sensor) and an RDI 150 kHz current profiler mounted in a general oceanics 12-place rosette, with12l Niskin bottles 

  • drifters with holey-sock positioned at 50 m deep below the expected Ekman layer thickness (remaining in the eddy until mid May).

Licence CC-BY-NC
Acknowledgements The authors acknowledge the financial support of the French Government Defense procurement and technology agency (DGA) through PROTEVS project . 
They thank the technical team at the French Naval Hydrologic and Oceanographic Service (SHOM), the crew of the French Navy ship Beautemps-Beaupré for their contribution to the field experiment
Sensor metadata

CTD and LADCP casts :

- presure  (Sea-bird SBE-9 ; 0 at surface)

- sea water temperature (Sea-bird SBE-9; SBE 3 temperature sensor)

- sea water electrical conductivity (Sea-bird SBE-9; SBE 4 conductivity sensor) 

- practical salinity units  (derived computation)

- Currents velocities : RDI 150 kHz current profiler

SEASOAR transects :

- sea water temperature (Sea-bird SBE-9; SBE 3 temperature sensor)

- sea water electrical conductivity (Sea-bird SBE-9; SBE 4 conductivity sensor) 

- practical salinity units  (derived computation)

SURFACE DRIFTERS :

- geographical positions

- surface temperature

Data
File Size Format Processing Access
PROTEVS-MED2016 EDDY 179 MB CSV Raw data Open access
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How to cite 

Louazel Stephanie, Dumas Franck, Garreau Pierre (2018). High-resolution observations of a dual-core anticyclonic eddy in the Algerian Basin (PROTEVS-MED 2016). SEANOE. https://doi.org/10.17882/56028