Surface expression of Mediterranean Water dipoles and their contribution to the shelf/slope – open ocean exchange

Abstract

Abstract. The generation of dipolar eddies within the Mediterranean Water (MW) layers, at the Portuguese continental slope, was observed using subsurface RAFOS floats. The surface expression of these mid-depth dipoles is here characterized with remote sensing data, namely with sea surface temperature, chlorophyll concentration and sea surface height measurements. Two cases are presented demonstrating the remote detection of these underwater structures in the Gulf of Cadiz during 1998 and 2001. The presence of subsurface MW dipoles in the Iberian coastal zone is shown to influence the development of coastal upwelling filaments. The surface circulation induced by the dipoles causes the upwelling filaments to extend offshorewards and thus to enhance the transport of physical, chemical and biological properties into the open ocean. A numerical model simulation of the ocean circulation around the Iberian Peninsula forced by heat and freshwater fluxes (computed using the NCEP reanalysis atmospheric state) and by the overflow of MW at the Strait of Gibraltar, corroborates the connection between the surface and the mid-depth flows. The highresolution numerical experiment is used to help clarifying the occurrence of the MW dipoles surface expression and the impact of these dipoles on the eddy kinetic energy of the upper ocean and on the exchange of volume and salt between the shelf/slope and the open ocean.

Variability of Iberian upwelling implied by ERA-40 and ERA-Interim reanalyses

“…Results show a rather good agreement on the western coast, indicating a qualitatively good representation of enhanced inter-annual variability in the region affected by episodic upwelling. Results are poor on the southern coast, a region where all results should be considered with caution, since the simulation domain and resolution do not allow for a representation of the interaction between the Upper Atlantic Water and the mid-depth Mediterranean Water (Serra et al, 2010).…”

Evidence of Mediterranean Water dipole collision in the Gulf of Cadiz

“…The western dipole (M1 and C1) could not be completely described by lack of hydrological data, but its meddy was fully studied in Carton et al [2010]. The Portimão dipole (M2 and C2), which had been described previously in Serra et al [2005], Ambar et al [2008], and Serra et al [2010], has been identified as the structure colliding with the western dipole, in the present paper.…”

“…The meddy position corresponds to the Rafos floats loops during this period. The cyclone is called C3 and the meddy M3 (labeled M6 in Figure 6 of Serra et al [2010]). Now, we compare the hydrological properties of M3 with those of M1 and M2, and the characteristics of C3 with those of C2.…”

Seasonal cycle of plankton production in the Iberian margin based on a high resolution ocean model

“…The high-resolution domain, or second domain (SD), included the western Iberian region from the Gulf of Cádiz to northwest Iberia (Galicia) (34.5° N --45.5° N and 5.5° W --12.5° W; ~ 1200 x× 600 km) ( Fig. 1) and had a horizontal resolution of 1/27° (~ 3 km) and 60 vertical s-levels in order to properly resolve the Mediterranean undercurrent, which the circulation of which is known to influence the surface transport of chemical and biological properties (Serra et al, 2010). A more detailed description of this climatological regional configuration of ROMS can be found in Nolasco et al (2013).…”