114
L. G.-Weil et al.
Table 5.1 Long-term
mesoscale features generated
in the Canary Islands area
during 1998
Feature First location place
First observation date Days
C1
SW Gran Canaria
(27.55
◦ N, − 16.18
◦ W)
08/04/98
124
C2
SW Gran Canaria
(27.80
◦ N, − 16.05
◦ W)
03/07/98
83
C3
Fuerteventura-Africa
(27.54
◦ N, − 14.87
◦ W)
27/06/98
230
A1
S Gran Canaria
(27.37
◦ N, − 15.81
◦ W)
26/06/98
419
A2
S Tenerife
(27.56
◦ N, − 17.02
◦ W)
27/07/98
311
A3
SW La Palma
(28.28
◦ N, − 18.30
◦ W)
16/09/98
102
F2
S Cape Juby
(27.60
◦ N, − 13.71
◦ W)
27/06/98
167
F3
S Cape Bojador
(25.51
◦ N, − 15.80
◦ W)
27/07/98
87
5.3.2.2 Eddies and Cross Shelf Transport
The creation of filaments in the Canary Islands area is strongly promoted by
mesoscale eddies. In fact, eddies C1 and A1, both of which detached from Gran
Canaria island, generated upwelling filaments F1 (Fig. 5.3c–e) and F3 (Fig. 5.3e–h)
when moving southward and approaching the African continental shelf. Starting
in June 1998, C1 reached its most southern position at 26.2
◦ N and 16.5
◦ W, just
south of Cape Bojador and next to the latitude where the coastal shelf gets wider
(see Fig. 5.1a). At this time, a fully developed and irregular coastal upwelling front,
showing wavelike disturbances (some of them evolving into small filaments), was
observed. Then, the interaction between the eddy and one of these disturbances gave
place to a narrow and long tongue, about 10–15 km wide and ∼ 200 km long (from
the coastal upwelling front) labeled F1. This is shown in Figs. 5.3c, d and 5.10a, b,
in which C1 appears to have reached its final position.
At the end of July 1998, after moving southward, A1 was also implicated in the
formation of filament F3, located south of Cape Bojador. This process started when
the upwelled waters situated south of 26
◦ N (again the location where the continental
shelf expands) felt the shear induced by the southern rim of the eddy (Fig. 5.3e).
The upwelled waters were expelled away from the coast, forming a small plume
that quickly advanced offshore, around eddy A1 (Figs. 5.3f and 5.10c). Then, in 3
weeks, a long and narrow filament was clearly seen extending offshore, as A1 moved
westward (Figs. 5.6a–c and 5.10d). F3 persisted, in association with A1, until the
end of October, when A1 collided with another anticyclonic eddy (Fig. 5.7a).
In early June 1998, a small disturbance was observed in the coastal upwelling front
close to Cape Juby, in both the Chl-a and BT images. In successive images, this smallscale feature was seen growing, until finally, on June 27, 1998, the long filament F2
appeared, as entrained around the nearly stationary eddy C3. This filament stayed
associated with C3 (Fig. 5.10b–d) until the end of October 1998, when the eddy was
placed south of Gran Canaria.
L. G.-Weil et al.
Table 5.1 Long-term
mesoscale features generated
in the Canary Islands area
during 1998
Feature First location place
First observation date Days
C1
SW Gran Canaria
(27.55
◦ N, − 16.18
◦ W)
08/04/98
124
C2
SW Gran Canaria
(27.80
◦ N, − 16.05
◦ W)
03/07/98
83
C3
Fuerteventura-Africa
(27.54
◦ N, − 14.87
◦ W)
27/06/98
230
A1
S Gran Canaria
(27.37
◦ N, − 15.81
◦ W)
26/06/98
419
A2
S Tenerife
(27.56
◦ N, − 17.02
◦ W)
27/07/98
311
A3
SW La Palma
(28.28
◦ N, − 18.30
◦ W)
16/09/98
102
F2
S Cape Juby
(27.60
◦ N, − 13.71
◦ W)
27/06/98
167
F3
S Cape Bojador
(25.51
◦ N, − 15.80
◦ W)
27/07/98
87
5.3.2.2 Eddies and Cross Shelf Transport
The creation of filaments in the Canary Islands area is strongly promoted by
mesoscale eddies. In fact, eddies C1 and A1, both of which detached from Gran
Canaria island, generated upwelling filaments F1 (Fig. 5.3c–e) and F3 (Fig. 5.3e–h)
when moving southward and approaching the African continental shelf. Starting
in June 1998, C1 reached its most southern position at 26.2
◦ N and 16.5
◦ W, just
south of Cape Bojador and next to the latitude where the coastal shelf gets wider
(see Fig. 5.1a). At this time, a fully developed and irregular coastal upwelling front,
showing wavelike disturbances (some of them evolving into small filaments), was
observed. Then, the interaction between the eddy and one of these disturbances gave
place to a narrow and long tongue, about 10–15 km wide and ∼ 200 km long (from
the coastal upwelling front) labeled F1. This is shown in Figs. 5.3c, d and 5.10a, b,
in which C1 appears to have reached its final position.
At the end of July 1998, after moving southward, A1 was also implicated in the
formation of filament F3, located south of Cape Bojador. This process started when
the upwelled waters situated south of 26
◦ N (again the location where the continental
shelf expands) felt the shear induced by the southern rim of the eddy (Fig. 5.3e).
The upwelled waters were expelled away from the coast, forming a small plume
that quickly advanced offshore, around eddy A1 (Figs. 5.3f and 5.10c). Then, in 3
weeks, a long and narrow filament was clearly seen extending offshore, as A1 moved
westward (Figs. 5.6a–c and 5.10d). F3 persisted, in association with A1, until the
end of October, when A1 collided with another anticyclonic eddy (Fig. 5.7a).
In early June 1998, a small disturbance was observed in the coastal upwelling front
close to Cape Juby, in both the Chl-a and BT images. In successive images, this smallscale feature was seen growing, until finally, on June 27, 1998, the long filament F2
appeared, as entrained around the nearly stationary eddy C3. This filament stayed
associated with C3 (Fig. 5.10b–d) until the end of October 1998, when the eddy was
placed south of Gran Canaria.