flowing eastwards at the surface layer, and Mediterranean waters flowing westwards
at the intermediate and deep layers to finally outflow through the Strait of Gibraltar,
being these currents modulated by the Coriolis force (Millot and Taupier-Letage
2005). This general circulation pattern is ultimately responsible for the circulation of
the Alboran Sea, which has a very energetic dynamics at its upper layer, showing
intense currents (Perkins et al. 1990), frontal areas, and mesoscale structures
(Troupin et al. 2018; Olita et al. 2017; García-Lafuente et al. 1998; Tintoré et al.
1988).
The heat and water budget of the Mediterranean Sea can change on a large range
of time scales, producing changes in the exchange through the Strait of Gibraltar and
consequently on the properties of the water masses and their circulation patterns
within the Mediterranean Sea and the Alboran Sea itself. Such time scales go from
seasonal (Vargas-Yáñez et al. 2002), to inter-annual (Mihanovic et al. 2018; Renault
et al. 2012), decadal and secular (Vargas-Yáñez et al. 2010a, b). The latter time scale
is presumably linked to the current global warming process.
Besides this variability associated to the Mediterranean thermohaline circulation,
the Alboran Sea circulation is influenced by changes in the wind and pressure fields
that could alter its circulation at shorter (sub-inertial, several days to weeks) time
scales. Finally, some of the shortest time scales affecting the circulation of the
Alboran Sea are those associated to tidal phenomena, although these latter processes
are of minor importance within the Mediterranean Sea. This circulation feature is
mainly barotropic, affecting the whole water column, as internal tides, which have a
large magnitude in the Strait of Gibraltar (Naranjo et al. 2014; Sánchez-Román et al.
2009) are of minor importance within the Alboran Sea (Vargas-Yáñez 1998; GarcíaLafuente et al. 1999).
In order to provide a brief description of the physical processes that determine the
properties of different water masses and their circulation within the Alboran Sea and
their time and spatial variability, this chapter is organized as follows. First, the
climatic forcing, the formation of the different water masses and the thermohaline
circulation of the Mediterranean Sea are described from a general perspective
establishing the climatic and oceanographic context of the Alboran Sea. Then a
more specific description of the water masses and their properties in the Alboran Sea
are presented. Once the water masses that occupy the Alboran Sea have been
described, their circulation is addressed. The first section is devoted to a brief
description of the tidal currents which constitute a source of variability at short
time scales. Then, the circulation of the different layers that form the Alboran Sea are
analyzed. This analysis is decomposed into the upper layer, on one hand, and the
intermediate and deep layers on the other. Although these two sections have been
established according to the different depth levels considered, and not to the different
time scales, it can be established that the time scales that affect the main traits of the
Alboran Sea circulation, mainly in the upper layer, extend from the sub-inertial to the
inter-annual, passing through the seasonal one. The last section is specifically
devoted to long-term changes that affect the properties of the main water masses
in the Alboran Sea and are very likely associated to climate change. This chapter
ends with a summary and conclusions section.
86
M. Vargas-Yáñez et al.
at the intermediate and deep layers to finally outflow through the Strait of Gibraltar,
being these currents modulated by the Coriolis force (Millot and Taupier-Letage
2005). This general circulation pattern is ultimately responsible for the circulation of
the Alboran Sea, which has a very energetic dynamics at its upper layer, showing
intense currents (Perkins et al. 1990), frontal areas, and mesoscale structures
(Troupin et al. 2018; Olita et al. 2017; García-Lafuente et al. 1998; Tintoré et al.
1988).
The heat and water budget of the Mediterranean Sea can change on a large range
of time scales, producing changes in the exchange through the Strait of Gibraltar and
consequently on the properties of the water masses and their circulation patterns
within the Mediterranean Sea and the Alboran Sea itself. Such time scales go from
seasonal (Vargas-Yáñez et al. 2002), to inter-annual (Mihanovic et al. 2018; Renault
et al. 2012), decadal and secular (Vargas-Yáñez et al. 2010a, b). The latter time scale
is presumably linked to the current global warming process.
Besides this variability associated to the Mediterranean thermohaline circulation,
the Alboran Sea circulation is influenced by changes in the wind and pressure fields
that could alter its circulation at shorter (sub-inertial, several days to weeks) time
scales. Finally, some of the shortest time scales affecting the circulation of the
Alboran Sea are those associated to tidal phenomena, although these latter processes
are of minor importance within the Mediterranean Sea. This circulation feature is
mainly barotropic, affecting the whole water column, as internal tides, which have a
large magnitude in the Strait of Gibraltar (Naranjo et al. 2014; Sánchez-Román et al.
2009) are of minor importance within the Alboran Sea (Vargas-Yáñez 1998; GarcíaLafuente et al. 1999).
In order to provide a brief description of the physical processes that determine the
properties of different water masses and their circulation within the Alboran Sea and
their time and spatial variability, this chapter is organized as follows. First, the
climatic forcing, the formation of the different water masses and the thermohaline
circulation of the Mediterranean Sea are described from a general perspective
establishing the climatic and oceanographic context of the Alboran Sea. Then a
more specific description of the water masses and their properties in the Alboran Sea
are presented. Once the water masses that occupy the Alboran Sea have been
described, their circulation is addressed. The first section is devoted to a brief
description of the tidal currents which constitute a source of variability at short
time scales. Then, the circulation of the different layers that form the Alboran Sea are
analyzed. This analysis is decomposed into the upper layer, on one hand, and the
intermediate and deep layers on the other. Although these two sections have been
established according to the different depth levels considered, and not to the different
time scales, it can be established that the time scales that affect the main traits of the
Alboran Sea circulation, mainly in the upper layer, extend from the sub-inertial to the
inter-annual, passing through the seasonal one. The last section is specifically
devoted to long-term changes that affect the properties of the main water masses
in the Alboran Sea and are very likely associated to climate change. This chapter
ends with a summary and conclusions section.
86
M. Vargas-Yáñez et al.