Seminar: 3D dynamics from uCTD observations of an anticyclonic eddy in the Alboran Sea (using variational mapping method)

  • Speaker: Eugenio Cutolo. Oceanografía y Cambio Global, IMEDEA







Esporles, December 20, 2019.


Intensive underway CTD (uCTD) sampling took place in the Alboran Sea during 2019. A 40-km diameter anticyclonic eddy was observed from satellites (altimetry and chlorophyll data) inside the campaign area. The same feature appeared in the high frequency uCTD salinity and temperature profiles at 1 km resolution and down to 200 m depth. These data were mapped with a variational method and used to reconstruct the 3D dynamics of the area.



The data were mapped also using optimal interpolation to test the sensibility of the methods. The interpolation grid was made with rotated coordinate system with axes parallel to the along/across-front directions. This strategy better preserved the gradients and allowed for a small correlation length of 20 km in the across-front direction. Along front we used a correlation length scale of 35 km due to the larger distances between profiles in the along front direction. The mapped hydrography data have been used to compute dynamic height and geostrophic velocities. ADCP data confirmed the validity of 200 m as a no-motion depth. Vertical velocities have been estimated from the Quasi-Geostrophic and Semi-Geostrophic frameworks. The SG omega equation gives total vertical velocities with a magnitude up to 45 m/day slighty bigger than the QG .



Furthermore the QG and SG equations provided estimates of the ageostrophic horizontal velocities component that has been compared with ADCP data and with the lagrangian trajectories obtained by the drifters deployed during the campaign. Finally, the validity of the QG and SG approximations in the Alboran Sea is investigated using synthetic data coming from a Process-Study Model Simulation.




Date and Time: Friday, December 20, 10:00-11:00h

Place: IMEDEA Meeting room on the 2nd floor,