separated by a cyclonic structure, referred to as Central Cyclonic Gyre, CCG
(Renault et al. 2012). This ensemble of mesoscale structures represents the widely
accepted mean pattern of surface circulation in the Alboran Sea. Such a pattern, with
the AJ flowing along the middle of the basin, favors the isolation of north and south
shore ecosystems or, at least, establishes a considerable obstacle for their hydrodynamic connection.
Intermediate and bottom circulation consist of waters of Mediterranean origin
moving sluggishly toward the Strait underneath the surface Atlantic layer (VargasYañez, this book). A spatial differentiation is found in that Levantine and other
Intermediate waters flow closer to the Spanish shore whereas Western Mediterranean deepwater moves along the African coast (Naranjo et al. 2015; Garcia-Lafuente
et al. 2017). All they overflow the main sill of the Strait and spread into the Atlantic
Ocean. Except for the Strait area itself, their typical speed is one order of magnitude
less than the surface counterpart. Its seasonal variability is more reduced and linked
to the formation of deep water in the Gulf of Lions (Garcia-Lafuente et al. 2009). In a
regional scenario where the average upper layer flow is to the east, the intermediatedeep circulation provides a chance for hydrodynamic connection in the opposite
direction.
12.2.2 Short-term Variability: Instabilities
The previous description suggests mesoscale scenarios simpler than those actually
found in the Alboran Sea. The AJ and the surface circulation are full of submesoscale
Fig. 12.1 Sketch of the average surface circulation of the Alboran Sea and Gulf of Cadiz overlying
the MODIS image of January 25, 2003 (NASA Goddard Space Flight Center, EOS Project Science
Office). Solid thick lines outline the two anticyclonic gyres (Western and Eastern Alboran Gyres,
WAG and EAG, respectively, and the Atlantic Jet, AJ). Dashed line is the Central Cyclonic Gyre
(CCG). Some locations (in white) and geographical features (deep yellow) are labelled
462
J. Garcia-Lafuente et al.
(Renault et al. 2012). This ensemble of mesoscale structures represents the widely
accepted mean pattern of surface circulation in the Alboran Sea. Such a pattern, with
the AJ flowing along the middle of the basin, favors the isolation of north and south
shore ecosystems or, at least, establishes a considerable obstacle for their hydrodynamic connection.
Intermediate and bottom circulation consist of waters of Mediterranean origin
moving sluggishly toward the Strait underneath the surface Atlantic layer (VargasYañez, this book). A spatial differentiation is found in that Levantine and other
Intermediate waters flow closer to the Spanish shore whereas Western Mediterranean deepwater moves along the African coast (Naranjo et al. 2015; Garcia-Lafuente
et al. 2017). All they overflow the main sill of the Strait and spread into the Atlantic
Ocean. Except for the Strait area itself, their typical speed is one order of magnitude
less than the surface counterpart. Its seasonal variability is more reduced and linked
to the formation of deep water in the Gulf of Lions (Garcia-Lafuente et al. 2009). In a
regional scenario where the average upper layer flow is to the east, the intermediatedeep circulation provides a chance for hydrodynamic connection in the opposite
direction.
12.2.2 Short-term Variability: Instabilities
The previous description suggests mesoscale scenarios simpler than those actually
found in the Alboran Sea. The AJ and the surface circulation are full of submesoscale
Fig. 12.1 Sketch of the average surface circulation of the Alboran Sea and Gulf of Cadiz overlying
the MODIS image of January 25, 2003 (NASA Goddard Space Flight Center, EOS Project Science
Office). Solid thick lines outline the two anticyclonic gyres (Western and Eastern Alboran Gyres,
WAG and EAG, respectively, and the Atlantic Jet, AJ). Dashed line is the Central Cyclonic Gyre
(CCG). Some locations (in white) and geographical features (deep yellow) are labelled
462
J. Garcia-Lafuente et al.