Atlantic Coastal Biome
227
occurs because of the conjunction of different subsurface water masses. Some
confusion is possible in color images between algal production due to upwelling
south of Cape Finisterre and production within the adjacent coastal rias due to
river discharge of nutrients.
Cape St. Vincent (37
N ): Upwelling behind this southwest-jutting cape is topographically reinforced, strong, and extends along the coast of the Algarve, where red
tide blooms are frequent accessories to upwelling events. Off Huelva, a front often
extends in a southwesterly direction and marks the limit of the upwelling process.
Capes Spartel (35
N ), Cantir (325
N ), Ghir (315
N ), and Juby (28
N ): Upwelling
occurs the length of this coast essentially year-round, although peaking in frequency
and intensity during summer. It is strongest behind these capes because of favorable
angles between the coastline and the direction of the trade winds (Mittelstaedt,
1991). Discharge from rivers draining from the Atlas Mountains may cause some
difficulty of interpretation along this sector of the coast, where upwelling is not such
an intense phenomenon as further south. The Canary Islands lie just beyond the
continental edge at Cape Jubi and their presence must be noted when examining
satellite images of this region.
The Canary Islands (27–29
N ) archipelago spans the southward flow of the Canary
Current; a recurrent cyclonic eddy south of the islands entrains mesoscale eddies
of both signs formed behind individual islands as well as cold filaments arising at
the coast. Recirculation of these features within the persistent cyclone constrains
the export capacity of individual filaments (Barton et al., 2004). Water may be
recirculated within this system for some weeks, surface layer drifters completing
several circuits before being released into the complex flows further south.
Cape Bojador (26
N ) in Western Sahara is an upwelling focus in both spring and
summer and, from here south to Cape Blanc, upwelling occurs more consistently
year-round than elsewhere in this province. Perhaps onshore flow may restrict the
spread of the upwelled water to a rather narrow zone along the coast (Mittelstaedt,
1991). Especially between Cape Bojador and Cape Barbas, upwelled NACW water
forms cells of bottom water on the shelf, within which nutrient levels may be
unusually high (Hughes and Fiuza, 1982; Minas et al., 1982).
Cape Blanc, Cape Timiris (19–21
N ) is a major upwelling focus where the greatest
intensity and frequency of upwelling occurs during the first months of the year.
It is also a special case because a shelf-crossing submarine canyon may serve to
focus the upwelling flow (Roy, 1990) so that an immensely productive, plumelike
ecosystem develops, as noted earlier, that is similar to that off Peru at 15
S (see
Chapter 11, HUMB).
Arguin Bank (20
N ) occupies the bight to the south of Cape Blanc and is a special
case. There is at times a strong excess of evaporation over precipitation in the
shallow water around this biologically rich area of shallows and offshore banks.
When this occurs, episodic cascades of the dense water that is formed on the bank
down the continental slope are replaced almost immediately with cool, recently
upwelled water, bringing nutrients to the shallows (van Camp et al., 1991), this
being, perhaps, a unique model of the general process of upwelling.
Cape Verde, Cape Roxo (12–15
N ): In this most southerly focus of upwelling, activity
is restricted to late months of boreal winter when the trade-wind belt is at its most
southerly position, and Harmattan winds reach the sea. In boreal summer and fall,
the region is entirely under the influence of the NECC and of tropical water. At
Cape Roxo, the coast bends eastward into the Gulf of Guinea and a stable, tropical
coastal regime is met (see the GUIN Coastal Province).
Because this province lies between the Atlantic and the Sahara desert, a special characteristic of the wind regime is the dust-laden nature of the northeast trades, strongest in
227
occurs because of the conjunction of different subsurface water masses. Some
confusion is possible in color images between algal production due to upwelling
south of Cape Finisterre and production within the adjacent coastal rias due to
river discharge of nutrients.
Cape St. Vincent (37
N ): Upwelling behind this southwest-jutting cape is topographically reinforced, strong, and extends along the coast of the Algarve, where red
tide blooms are frequent accessories to upwelling events. Off Huelva, a front often
extends in a southwesterly direction and marks the limit of the upwelling process.
Capes Spartel (35
N ), Cantir (325
N ), Ghir (315
N ), and Juby (28
N ): Upwelling
occurs the length of this coast essentially year-round, although peaking in frequency
and intensity during summer. It is strongest behind these capes because of favorable
angles between the coastline and the direction of the trade winds (Mittelstaedt,
1991). Discharge from rivers draining from the Atlas Mountains may cause some
difficulty of interpretation along this sector of the coast, where upwelling is not such
an intense phenomenon as further south. The Canary Islands lie just beyond the
continental edge at Cape Jubi and their presence must be noted when examining
satellite images of this region.
The Canary Islands (27–29
N ) archipelago spans the southward flow of the Canary
Current; a recurrent cyclonic eddy south of the islands entrains mesoscale eddies
of both signs formed behind individual islands as well as cold filaments arising at
the coast. Recirculation of these features within the persistent cyclone constrains
the export capacity of individual filaments (Barton et al., 2004). Water may be
recirculated within this system for some weeks, surface layer drifters completing
several circuits before being released into the complex flows further south.
Cape Bojador (26
N ) in Western Sahara is an upwelling focus in both spring and
summer and, from here south to Cape Blanc, upwelling occurs more consistently
year-round than elsewhere in this province. Perhaps onshore flow may restrict the
spread of the upwelled water to a rather narrow zone along the coast (Mittelstaedt,
1991). Especially between Cape Bojador and Cape Barbas, upwelled NACW water
forms cells of bottom water on the shelf, within which nutrient levels may be
unusually high (Hughes and Fiuza, 1982; Minas et al., 1982).
Cape Blanc, Cape Timiris (19–21
N ) is a major upwelling focus where the greatest
intensity and frequency of upwelling occurs during the first months of the year.
It is also a special case because a shelf-crossing submarine canyon may serve to
focus the upwelling flow (Roy, 1990) so that an immensely productive, plumelike
ecosystem develops, as noted earlier, that is similar to that off Peru at 15
S (see
Chapter 11, HUMB).
Arguin Bank (20
N ) occupies the bight to the south of Cape Blanc and is a special
case. There is at times a strong excess of evaporation over precipitation in the
shallow water around this biologically rich area of shallows and offshore banks.
When this occurs, episodic cascades of the dense water that is formed on the bank
down the continental slope are replaced almost immediately with cool, recently
upwelled water, bringing nutrients to the shallows (van Camp et al., 1991), this
being, perhaps, a unique model of the general process of upwelling.
Cape Verde, Cape Roxo (12–15
N ): In this most southerly focus of upwelling, activity
is restricted to late months of boreal winter when the trade-wind belt is at its most
southerly position, and Harmattan winds reach the sea. In boreal summer and fall,
the region is entirely under the influence of the NECC and of tropical water. At
Cape Roxo, the coast bends eastward into the Gulf of Guinea and a stable, tropical
coastal regime is met (see the GUIN Coastal Province).
Because this province lies between the Atlantic and the Sahara desert, a special characteristic of the wind regime is the dust-laden nature of the northeast trades, strongest in