either direction with similar regularity in the first case, but obviously not in the
second one.
Curiously, examples of both situations are met in the Mediterranean Sea: the
Messina and Gibraltar straits. The Messina strait, roughly sketched in Fig. 3a, falls
in the first class. It sustains strong tidal currents due to the different phase of the tide
between the Tyrrhenian and Ionian seas [17]. In summer-autumn, when the seasonal thermocline is formed and the water column becomes stratified, internal wave
packets moving northwards or southwards are regularly observed, with nearly equal
rate of occurrence [1, 18]. On the contrary, the baroclinic background state sketched
in Fig. 3b, which applies to Gibraltar with the Mediterranean Sea to the right,
overwhelmingly breaks the balance toward the side of west-of-CS (left-of-sill in
Fig. 3) formed jump and subsequent eastwards propagation of internal waves.
Additionally, the year-round stratification in Gibraltar, driven by salinity rather than
temperature differences, also results in a fairly even distribution of the observed
wave packets over the year that contrasts with the summer-autumn concentration in
Messina [1].
The formation of hydraulic jumps east of CS is reproduced by the numerical
model of Sánchez-Garrido et al. [13], despite its apparent uncommonness (Fig. 2f).
The west-going wave packets resulting from the decay of the east-of-CS jump are
likewise elusive to observe, the few reported cases being offered by Alpers et al.
[18] or Morozov et al. [9]. Interestingly, the former authors associated the events
with the seasonal thermocline rather than with the permanent pycnocline between
Atlantic and Mediterranean waters, which is the interface the east-going internal
wave packets are linked to.
Even when the understanding of the whole process is very satisfactory,
small-scale details (O(1 km)) of the formation processes of the hydraulic jumps on
either side of CS, their flooding and subsequent release of internal bores, their
cross-strait spatial structure, etc., are not so well known, let alone from an experimental point of view. This work addresses some of these issues from an observational approach, taking advantage of a field experiment primarily designed to
investigate the cross-strait structure of the Mediterranean outflow in CS at subinertial time-scales [19]. Next section shows the detailed bathymetry of the CS area
and the essential topographic features, section “Data and Data Processing” presents
the data and data-processing, section “General Description” analyzes the data and
section “Discussion and Conclusions” discusses and summarizes the conclusions
drawn from this study.
A Close-Up to the Bathymetry of Camarinal Sill
Figure 1b displays an updated and detailed bathymetry of CS. The topography is
very uneven with marked sub-kilometric features that steer the deep water flow. Of
special interest is the presence of two larger-scale channels in the section, denoted by
Camarinal North and Camarinal South Channels (CSN and CSS, hereinafter, Fig. 1),
Asymmetric Baroclinic Response to Tidal Forcing …
197
second one.
Curiously, examples of both situations are met in the Mediterranean Sea: the
Messina and Gibraltar straits. The Messina strait, roughly sketched in Fig. 3a, falls
in the first class. It sustains strong tidal currents due to the different phase of the tide
between the Tyrrhenian and Ionian seas [17]. In summer-autumn, when the seasonal thermocline is formed and the water column becomes stratified, internal wave
packets moving northwards or southwards are regularly observed, with nearly equal
rate of occurrence [1, 18]. On the contrary, the baroclinic background state sketched
in Fig. 3b, which applies to Gibraltar with the Mediterranean Sea to the right,
overwhelmingly breaks the balance toward the side of west-of-CS (left-of-sill in
Fig. 3) formed jump and subsequent eastwards propagation of internal waves.
Additionally, the year-round stratification in Gibraltar, driven by salinity rather than
temperature differences, also results in a fairly even distribution of the observed
wave packets over the year that contrasts with the summer-autumn concentration in
Messina [1].
The formation of hydraulic jumps east of CS is reproduced by the numerical
model of Sánchez-Garrido et al. [13], despite its apparent uncommonness (Fig. 2f).
The west-going wave packets resulting from the decay of the east-of-CS jump are
likewise elusive to observe, the few reported cases being offered by Alpers et al.
[18] or Morozov et al. [9]. Interestingly, the former authors associated the events
with the seasonal thermocline rather than with the permanent pycnocline between
Atlantic and Mediterranean waters, which is the interface the east-going internal
wave packets are linked to.
Even when the understanding of the whole process is very satisfactory,
small-scale details (O(1 km)) of the formation processes of the hydraulic jumps on
either side of CS, their flooding and subsequent release of internal bores, their
cross-strait spatial structure, etc., are not so well known, let alone from an experimental point of view. This work addresses some of these issues from an observational approach, taking advantage of a field experiment primarily designed to
investigate the cross-strait structure of the Mediterranean outflow in CS at subinertial time-scales [19]. Next section shows the detailed bathymetry of the CS area
and the essential topographic features, section “Data and Data Processing” presents
the data and data-processing, section “General Description” analyzes the data and
section “Discussion and Conclusions” discusses and summarizes the conclusions
drawn from this study.
A Close-Up to the Bathymetry of Camarinal Sill
Figure 1b displays an updated and detailed bathymetry of CS. The topography is
very uneven with marked sub-kilometric features that steer the deep water flow. Of
special interest is the presence of two larger-scale channels in the section, denoted by
Camarinal North and Camarinal South Channels (CSN and CSS, hereinafter, Fig. 1),
Asymmetric Baroclinic Response to Tidal Forcing …
197