López-Jurado et al. 1995; López-Jurado 1990). The θS values above the mixing line
show an absolute salinity maximum (>38.5) and a relative temperature maximum
(>13.25
C) that correspond to the LIW. WMDW is found below the LIW, filling
the Alboran Sea to the sea bottom with θS values that range between 12.78
C and
12.8
C and between 38.42 and 38.43. Finally, since TDW is denser than LIW, but
lighter than the WMDW it is located between these two water masses, and can thus
easily be confused with the mixing line between LIW and WMDW (García-Lafuente
et al. 2017).
In summary, AW, WIW, LIW, WMDW and TDW can be observed in the
Alboran Sea and even in the Strait of Gibraltar (García-Lafuente et al. 2017; Naranjo
et al. 2015; Millot 2009). Their spatial distribution depends on the dynamics and
circulation of this basin and will be discussed in the next sections.
4.4 Currents and Circulation in the Alboran Sea
The currents in the Alboran Sea are mainly driven by the Mediterranean thermohaline circulation previously described, which is modulated by the Coriolis force,
winds and bathymetry. As a result, there is a fast AW flow, usually referred to in
the literature as the Atlantic Jet (AJ), flowing into the Alboran Sea through the Strait
of Gibraltar. This AJ and its variability dominate the circulation of the upper 200 m
of the Alboran Sea. Because of the freshwater deficit and heat losses in the Mediterranean Sea, there is a deep current that flows to the west below the AW. The
position of the interface separating both the inflow and the outflow depends on the
geographical location, decreasing from 250 at the western sector of the Strait of
Gibraltar, to 75 m at its eastern limit (Bray et al. 1995). Nevertheless, these figures
are strongly modulated by the tidal dynamics within the Strait (Naranjo et al. 2014,
2015).
The LIW, WMDW and TDW flow from 200 m depth to the sea bottom within the
Alboran Sea to finally outflow to the Atlantic Ocean. The circulation of the intermediate and deep water masses is conditioned by the Coriolis force and bathymetric
constrictions.
Besides this two-layer circulation scheme whose time variability is within the
sub-inertial range, there are tidal currents with diurnal and semi-diurnal periodicity.
Because of the periodic character of these currents they do not constitute an efficient
mechanism for the net transport of water, salt, heat or any biochemical tracer in the
Alboran Sea and for the rest of the Mediterranean, although a different situation
could stand for the Strait of Gibraltar.
The tidal range and the intensity of tidal currents in the Mediterranean Sea are
small if compared with the nearby Atlantic Ocean. Next section presents a brief
description of their characteristics in the Alboran Sea. Then, the circulation of the
upper layer of the Alboran Sea and its variability are addressed.
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M. Vargas-Yáñez et al.
show an absolute salinity maximum (>38.5) and a relative temperature maximum
(>13.25
C) that correspond to the LIW. WMDW is found below the LIW, filling
the Alboran Sea to the sea bottom with θS values that range between 12.78
C and
12.8
C and between 38.42 and 38.43. Finally, since TDW is denser than LIW, but
lighter than the WMDW it is located between these two water masses, and can thus
easily be confused with the mixing line between LIW and WMDW (García-Lafuente
et al. 2017).
In summary, AW, WIW, LIW, WMDW and TDW can be observed in the
Alboran Sea and even in the Strait of Gibraltar (García-Lafuente et al. 2017; Naranjo
et al. 2015; Millot 2009). Their spatial distribution depends on the dynamics and
circulation of this basin and will be discussed in the next sections.
4.4 Currents and Circulation in the Alboran Sea
The currents in the Alboran Sea are mainly driven by the Mediterranean thermohaline circulation previously described, which is modulated by the Coriolis force,
winds and bathymetry. As a result, there is a fast AW flow, usually referred to in
the literature as the Atlantic Jet (AJ), flowing into the Alboran Sea through the Strait
of Gibraltar. This AJ and its variability dominate the circulation of the upper 200 m
of the Alboran Sea. Because of the freshwater deficit and heat losses in the Mediterranean Sea, there is a deep current that flows to the west below the AW. The
position of the interface separating both the inflow and the outflow depends on the
geographical location, decreasing from 250 at the western sector of the Strait of
Gibraltar, to 75 m at its eastern limit (Bray et al. 1995). Nevertheless, these figures
are strongly modulated by the tidal dynamics within the Strait (Naranjo et al. 2014,
2015).
The LIW, WMDW and TDW flow from 200 m depth to the sea bottom within the
Alboran Sea to finally outflow to the Atlantic Ocean. The circulation of the intermediate and deep water masses is conditioned by the Coriolis force and bathymetric
constrictions.
Besides this two-layer circulation scheme whose time variability is within the
sub-inertial range, there are tidal currents with diurnal and semi-diurnal periodicity.
Because of the periodic character of these currents they do not constitute an efficient
mechanism for the net transport of water, salt, heat or any biochemical tracer in the
Alboran Sea and for the rest of the Mediterranean, although a different situation
could stand for the Strait of Gibraltar.
The tidal range and the intensity of tidal currents in the Mediterranean Sea are
small if compared with the nearby Atlantic Ocean. Next section presents a brief
description of their characteristics in the Alboran Sea. Then, the circulation of the
upper layer of the Alboran Sea and its variability are addressed.
92
M. Vargas-Yáñez et al.