Tidal Currents
5
_
Pacific
Atlantic -
200
- E 300
-a 0>
0
400
500
600
0
100
200
300
400
500
600
700
Distance (Km)
Fig. 1.5. Isopycnals along the main axis of the Straits of Magellan during the austral spring 1989. (After Panella
et al. 1991b)
structure of the water masses occupying the
western sub-basin beyond the sill is completely different from that of the central
sector of the Straits. Colder and more diluted
water masses are found in the underlying
layer down to 500 m. The moderate thermocline and the well-defined halocline
characterizing the top layer give rise to a
stratified and stable structure.
The warmer and saltier water masses
occupying the underlying layer indicate a
strong Pacific influence due to the inflow of
sub-Antarctic water into the sub-basin. This
water, which originates north of the Polar
Front, is known to travel towards the Chilean
coast via the West Drift Current. Then it
moves southward at 43°S latitude, carried
by the southern branch of the West Drift
Current. This produces the Cape Horn
Current which flows towards the Strait of
Drake. Near the coast, sub-Antarctic water
undergoes significant surface dilution due to
continental water runoff. Surface temperatures of 9-lO o C and salinities below 33.6psu
were recorded in summer in the ocean area
near the Pacific entrance of the Straits (Silva
and Neshyba 1977).
1.3 Tidal Currents
The most striking hydrodynamic feature of
the Straits are the strong tidal currents
originating from semi-diurnal tidal waves in
the Atlantic Ocean (Medeiros and Kierfve
1988). The tidal regime of the Straits is
macrotidal, deriving from the amplification
of waves along the wide continental shelf of
the Atlantic where tidal amplitude can reach
a maximum of 9 m during the spring tide.
Tidal amplitude within the Straits is much
lower, varying from 7.8m at the channel
entrance to 1.2 m at a distance of 150 km
(Fig. 1.6). A rapid diminution in the height
of the tides is observed west of the Primera
and Segunda Angostura. The mean and spring tide ranges drop, respectively, from 7.8
and 9.5 m on the eastern side of the Primera
Angostura to 4.0 and 7.8m immediately west
of this basin. By contrast, mean and spring
5
_
Pacific
Atlantic -
200
- E 300
-a 0>
0
400
500
600
0
100
200
300
400
500
600
700
Distance (Km)
Fig. 1.5. Isopycnals along the main axis of the Straits of Magellan during the austral spring 1989. (After Panella
et al. 1991b)
structure of the water masses occupying the
western sub-basin beyond the sill is completely different from that of the central
sector of the Straits. Colder and more diluted
water masses are found in the underlying
layer down to 500 m. The moderate thermocline and the well-defined halocline
characterizing the top layer give rise to a
stratified and stable structure.
The warmer and saltier water masses
occupying the underlying layer indicate a
strong Pacific influence due to the inflow of
sub-Antarctic water into the sub-basin. This
water, which originates north of the Polar
Front, is known to travel towards the Chilean
coast via the West Drift Current. Then it
moves southward at 43°S latitude, carried
by the southern branch of the West Drift
Current. This produces the Cape Horn
Current which flows towards the Strait of
Drake. Near the coast, sub-Antarctic water
undergoes significant surface dilution due to
continental water runoff. Surface temperatures of 9-lO o C and salinities below 33.6psu
were recorded in summer in the ocean area
near the Pacific entrance of the Straits (Silva
and Neshyba 1977).
1.3 Tidal Currents
The most striking hydrodynamic feature of
the Straits are the strong tidal currents
originating from semi-diurnal tidal waves in
the Atlantic Ocean (Medeiros and Kierfve
1988). The tidal regime of the Straits is
macrotidal, deriving from the amplification
of waves along the wide continental shelf of
the Atlantic where tidal amplitude can reach
a maximum of 9 m during the spring tide.
Tidal amplitude within the Straits is much
lower, varying from 7.8m at the channel
entrance to 1.2 m at a distance of 150 km
(Fig. 1.6). A rapid diminution in the height
of the tides is observed west of the Primera
and Segunda Angostura. The mean and spring tide ranges drop, respectively, from 7.8
and 9.5 m on the eastern side of the Primera
Angostura to 4.0 and 7.8m immediately west
of this basin. By contrast, mean and spring