Like all the major upwelling regions, the Canary Current is characterised b
y intense mesoscale structure in the transition zone between the cool, nutr
ient-rich waters of the coastal upwelling regime and the warmer, oligotroph
ic waters of the open ocean. The Canary Island archipelago, which straddles
the transition, introduces a second source of Variability by per turbing t
he general southwestward flow of both ocean currents and Trade winds. The c
ombined effects of the flow disturbance and the eddying and meandering of t
he boundary between upwelled and oceanic waters produce a complex pattern o
f regional variability. On the basis of historical data and a series of int
erdisciplinary field studies, the principal features of the region are desc
ribed. These include a prominent upwelling filament originating near 28 deg
rees N off the African coast, cyclonic and anti-cyclonic eddies downstream
of the archipelago, and warm wake regions protected from the Trade winds by
the high Volcanic peaks of the islands. The filament is shown to be a recu
rrent feature, apparently arising from the interaction of a topographically
trapped cyclonic eddy with the outer edge of the coastal upwelling zone. I
ts role in the transport and exchange of biogenic material, including fish
larvae, is considered. Strong cyclonic eddies, observed throughout the year
, drift slowly southwestward from Gran Canaria. One sampled in late summer
was characterised by large vertical isopycnal displacements, apparent surfa
ce divergence and strong upwelling, producing a fourfold increase in chloro
phyll concentrations over background values. Such intense eddies can be res
ponsible for a major contribution to the vertical flux of nitrogen. The lee
region of Gran Canaria is shown to be a location of strong pycnocline defo
rmation resulting from Ekman pumping on the wind shear boundaries, which ma
y contribute to the eddy formation process. (C) 1998 Elsevier Science Ltd.
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