Detecting and characterizing mesoscale and submesoscale structures of Mediterranean water from joint seismic and hydrographic measurements in the Gulf of Cadiz

Marine seismic and hydrographic data from the GO cruise in the Gulf of Cadiz acquired in April 2007 are analyzed to determine the physical nature and geometric characteristics of acoustic reflectors in the water column. Seismic data show strong reflectors near the surface, above Mediterranean water (MW) undercurrents, above a meddy, and within a submesoscale MW structure. These reflectors are associated with thermohaline layering. Wavelet analysis of seismic and hydrographic data (both in terms of reflectivity) shows strong signals with 12-48 m vertical wavelength scales. Hydrological data with its high vertical resolution, capture weaker signals with shorter wavelengths. At the edge of a meddy, lateral intrusions of fresher water are revealed by reflectors with 25-75 m thickness. Analyses of marine seismic data allow detection of submesoscale eddies that hydrographic sections identify only occasionally.