Aguedjou H. M. A., Chaigneau Alexis, Dadou I., Morel Y., Pegliasco C., Da-Allada C. Y., Baloitcha E. (2021). What can we learn from observed temperature and salinity isopycnal anomalies at eddy generation sites ? Application in the Tropical Atlantic Ocean. Journal of Geophysical Research : Oceans, 126 (11), p. e2021JC017630 [27 p.]. ISSN 2169-9275.
Titre du document
What can we learn from observed temperature and salinity isopycnal anomalies at eddy generation sites ? Application in the Tropical Atlantic Ocean
Aguedjou H. M. A., Chaigneau Alexis, Dadou I., Morel Y., Pegliasco C., Da-Allada C. Y., Baloitcha E.
Source
Journal of Geophysical Research : Oceans, 2021,
126 (11), p. e2021JC017630 [27 p.] ISSN 2169-9275
Based on 18 years of satellite altimetry data and temperature/salinity (theta/S) profiles from Argo floats, we analyze the isopycnal theta/S anomalies (theta'/S') within newborn eddies in the tropical Atlantic Ocean (TAO). Our results show that on density-coordinates, both anticyclonic eddies (AEs) and cyclonic eddies (CEs) can exhibit positive, negative, or nonsignificant theta'/S'. Almost half of the sampled eddies do not have significant theta'/S' at their generation site. The other half exhibits significant positive or negative theta', up to +/- 0.5 degrees C typically. More than 70% of them have a subsurface signature. Refined analyses of the vertical structure of new-born eddies in three selected subregions show the dominance of cold (warm) subsurface AEs (CEs) likely due to isopycnal advection of large-scale potential vorticity (PV) and theta. PV is a key parameter to analyze eddy generation and dynamics. Isopycnal advection, friction or diapycnal mixing can be involved in the generation of PV anomalies from which vortices can then emerge. However, it is difficult to evaluate PV at mesoscale. In this study, we propose to combine theta'/S' and PV anomalies to analyze which process could be involved in its transformation in the ocean. We argue that eddies created by diapycnal mixing or isopycnal advection of water-masses are associated with PV anomalies and significant theta'/S'. In contrast, a frictional forcing also creates PV anomalies but without modifying theta/S. Even though our results remain qualitative, the proposed diagnostics can be of interest to validate realistic models and then use them to analyze the PV anomaly sources.
