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What can we learn from observed temperature and salinity isopycnal anomalies at eddy generation sites? Application in the Tropical Atlantic Ocean
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  • Habib Micaël Agnédjo AGUEDJOU,
  • Alexis Chaigneau,
  • Isabelle DADOU,
  • Yves Morel,
  • Cori Pegliasco,
  • Casimir Yelognisse Da-Allada,
  • Ezinvi Baloïtcha
Habib Micaël Agnédjo AGUEDJOU
Laboratoire D'Études en Géophysique et Océanographie Spatiale, University of Toulouse, CNES,CNRS, IRD,UPS

Corresponding Author:[email protected]

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Alexis Chaigneau
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Isabelle DADOU
Laboratoire d'Etudes en Geophysique et Oceanographie Spatiales
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Yves Morel
LEGOS, Toulouse, France
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Cori Pegliasco
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Casimir Yelognisse Da-Allada
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Ezinvi Baloïtcha
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Potential vorticity (PV) is a key parameter to analyze the generation and dynamics of oceanic mesoscale eddies. Adiabatic and diabatic processes can be involved in the generation of localized PV anomalies and vortices. However, PV is difficult to evaluate at mesoscale. In this study we argue that eddies created by diapycnal mixing or isopycnal advection of water-masses are associated with PV anomalies and significant isopycnal temperature/salinity anomalies (Ɵ’/S’). In contrast, eddies created by friction are associated with PV anomalies but with non-significant isopycnal Ɵ’/S’. Based on 18 years of satellite altimetry data and vertical Ɵ/S profiles from Argo floats, we analyze the isopycnal Ɵ’/S’ within new-born eddies in the tropical Atlantic Ocean (TAO) and discuss the possible mechanisms involved in their generation. Our results show that on density-coordinates system, both anticyclonic (AEs) and cyclonic (CEs) eddies can exhibit positive, negative or non-significant isopycnal Ɵ’/S’. Almost half of the sampled eddies do not have significant Ɵ’/S’ at their generation site, suggesting that frictional effects play a significant role in the generation of their PV anomalies. The other half of eddies, likely generated by diapycnal mixing or isopycnal advection, exhibits significant positive or negative anomalies with typical Ɵ’ of ±0.5°C. More than 70% of these significant eddies are subsurface-intensified, having their cores below the seasonal pycnocline. Refined analyses of the vertical structure of new-born eddies in three selected subregions of the TAO, show the dominance of cold (warm) subsurface AEs (CEs) likely due to isopycnal advection of large scale PV and temperature.
Nov 2021Published in Journal of Geophysical Research: Oceans volume 126 issue 11. 10.1029/2021JC017630