7 The Cabo Frio Upwelling System, Brazil
J.L. VALENTIN
7.1 Introduction
Upwelling processes are most common and most intense on the eastern side
of the Atlantic and Pacific oceans. The Cabo Frio upwelling system (23°S,
42°W) is an anomaly in that it is on the west side of the Atlantic Ocean on the
coast of the state of Rio de Janeiro, Brazil (Fig. 7.1). The name"capo frigidio"
(cold cape) first appeared on marine charts of Portuguese navigators at the
beginning of the 15th century. A change in coastal direction from northsouth to east-west at Cabo Frio and the proximity of the 100-m isobath lead
to a topography which promotes upwelling of deep South Atlantic central
water (SACW). However, the principal mechanism of upwelling is northnortheast wind. The process of SACW upflow follows two stages (Moreira
da Silva 1973 ). The first stage begins in mid-August/September (late winter)
and depends on the position of the main flow of the Brazil Current in relation to the continental slope and on variations in frequency and intensity
of NE winds. During strong upwelling, SACW advances beyond the continental slope and invades the shelf to depths of about 50-80 m where is remains until April (mid-fall). The second stage of upwelling, mainly from
September to March, is influenced by changes in intensity and direction of
local winds, which cause alternating warming and cooling of near-surface
waters. Two or 3 days of northeasterly winds (10m s- 1 ) bring SACW to the
surface and cold front passages (8- to 10-day cycles), which cause the wind
to shift to the west, reverse the process (downwelling). Upwelled surface
water forms a narrow belt ( <1 km) around Cabo Frio with the plume flowing west-southwest (50 em s- 1 ), owing toNE winds and the Coriolis effect.
However, upwelling is not limited to the cold surface water zone, but
south of Cabo Sao Tome the penetration of the deep SACW over the shelf
causes stratification, with thermocline differences of up to 10 oc within a
few meters of depth during much of the year.
Ecological Studies, Vol. 144
U. Seeliger and B. Kjerfve (eds.)
Coastal Marine Ecosystems of Latin America
© Springer-Verlag Berlin Heidelberg 2001
J.L. VALENTIN
7.1 Introduction
Upwelling processes are most common and most intense on the eastern side
of the Atlantic and Pacific oceans. The Cabo Frio upwelling system (23°S,
42°W) is an anomaly in that it is on the west side of the Atlantic Ocean on the
coast of the state of Rio de Janeiro, Brazil (Fig. 7.1). The name"capo frigidio"
(cold cape) first appeared on marine charts of Portuguese navigators at the
beginning of the 15th century. A change in coastal direction from northsouth to east-west at Cabo Frio and the proximity of the 100-m isobath lead
to a topography which promotes upwelling of deep South Atlantic central
water (SACW). However, the principal mechanism of upwelling is northnortheast wind. The process of SACW upflow follows two stages (Moreira
da Silva 1973 ). The first stage begins in mid-August/September (late winter)
and depends on the position of the main flow of the Brazil Current in relation to the continental slope and on variations in frequency and intensity
of NE winds. During strong upwelling, SACW advances beyond the continental slope and invades the shelf to depths of about 50-80 m where is remains until April (mid-fall). The second stage of upwelling, mainly from
September to March, is influenced by changes in intensity and direction of
local winds, which cause alternating warming and cooling of near-surface
waters. Two or 3 days of northeasterly winds (10m s- 1 ) bring SACW to the
surface and cold front passages (8- to 10-day cycles), which cause the wind
to shift to the west, reverse the process (downwelling). Upwelled surface
water forms a narrow belt ( <1 km) around Cabo Frio with the plume flowing west-southwest (50 em s- 1 ), owing toNE winds and the Coriolis effect.
However, upwelling is not limited to the cold surface water zone, but
south of Cabo Sao Tome the penetration of the deep SACW over the shelf
causes stratification, with thermocline differences of up to 10 oc within a
few meters of depth during much of the year.
Ecological Studies, Vol. 144
U. Seeliger and B. Kjerfve (eds.)
Coastal Marine Ecosystems of Latin America
© Springer-Verlag Berlin Heidelberg 2001