Summary
345
3 Ocean Currents
The prevailing oceanographic conditions vary greatly along the coast of
South and Central America. The Pacific coast is characterized by a northflowing, cold-water, eastern boundary current, the Peru or Humboldt Current, with surface water temperatures of 11-17 oc, and a volume transport
of approximately 20 x 10 6 m 3 s- 1 • The current is not necessarily well defined
and varies in magnitude between the inner shelf and seaward of the narrow shelf. During La Nifia conditions, wind dynamics produce a strong
offshore Ekman flux and upwelling just seaward of the shelf from as deep
as 2,000 m in a band between 40°S and 4 os where approximately 20 o/o of the
global industrial fish are harvested (see Chap. 16 by Tarazana and Arntz).
Every 2-5 years, when equatorial winds weaken and the El Nifio phase of
the ENSO cycle peaks (i.e., 1982-1983, 1986-1987, 1991-1992, and
1997-1998), a catastrophic breakdown of the coastal marine upwelling
system occurs with an enormous impact on coastal marine Pacific ecosystems as well as on ecosystems elsewhere. Coastal upwelling is also very
much a feature of the Pacific coast of Mexico, where northwesterly winds
and the southward flowing California Currents produce upwelling locally
along the Pacific coast of Baja California (see Chap. 21 by Ibarra-Obando et
al.) along with an arid coastal climate (Fig. 2).
The Atlantic coast of South America, with the exception of a section
from 6°S (Rio Grande do Norte State) to 16°S (Abrolhos banks; see Chapter
by Kellogg and Mohriak and Chap. 6 by Zelinda et al.), is characterized by
relatively wide continental shelves. A western boundary current, the Brazil
Current, flows southward from just south of the equator to approximately
35°S latitude and is part of the subtropical anticyclonic gyre in the South
Atlantic. The Brazil current has a volume transport of 20-40 x 10 6 m 3 s- 1
and is characterized by coastal surface water temperatures between 26 and
30 oc (Castro and Miranda 1998).A number of coastal capes from Bahia to
Rio de Janeiro, Brazil, introduce intense local coastal upwelling downstream of the capes. Upwelling is particularly intense and persistent atCabo Frio (see Chap. 7 by Valentin) where surface temperatures measure
12-18 oc even during the austral summer. The Brazil current converges
with the northward flowing cold-water Malvinas Current between the
mouth of Rio de la Plata and Lagoa dos Patos to form the Subtropical
Convergence in the southwest Atlantic (see Chap. 11 by Odebrecht and
Castello). The predominant flow on either side of the convergence zone
continues towards the east (Fig. 2).
The Caribbean is characterized by a poorly organized surface flow from
the east towards the west-northwest, the so-called Caribbean Current,
345
3 Ocean Currents
The prevailing oceanographic conditions vary greatly along the coast of
South and Central America. The Pacific coast is characterized by a northflowing, cold-water, eastern boundary current, the Peru or Humboldt Current, with surface water temperatures of 11-17 oc, and a volume transport
of approximately 20 x 10 6 m 3 s- 1 • The current is not necessarily well defined
and varies in magnitude between the inner shelf and seaward of the narrow shelf. During La Nifia conditions, wind dynamics produce a strong
offshore Ekman flux and upwelling just seaward of the shelf from as deep
as 2,000 m in a band between 40°S and 4 os where approximately 20 o/o of the
global industrial fish are harvested (see Chap. 16 by Tarazana and Arntz).
Every 2-5 years, when equatorial winds weaken and the El Nifio phase of
the ENSO cycle peaks (i.e., 1982-1983, 1986-1987, 1991-1992, and
1997-1998), a catastrophic breakdown of the coastal marine upwelling
system occurs with an enormous impact on coastal marine Pacific ecosystems as well as on ecosystems elsewhere. Coastal upwelling is also very
much a feature of the Pacific coast of Mexico, where northwesterly winds
and the southward flowing California Currents produce upwelling locally
along the Pacific coast of Baja California (see Chap. 21 by Ibarra-Obando et
al.) along with an arid coastal climate (Fig. 2).
The Atlantic coast of South America, with the exception of a section
from 6°S (Rio Grande do Norte State) to 16°S (Abrolhos banks; see Chapter
by Kellogg and Mohriak and Chap. 6 by Zelinda et al.), is characterized by
relatively wide continental shelves. A western boundary current, the Brazil
Current, flows southward from just south of the equator to approximately
35°S latitude and is part of the subtropical anticyclonic gyre in the South
Atlantic. The Brazil current has a volume transport of 20-40 x 10 6 m 3 s- 1
and is characterized by coastal surface water temperatures between 26 and
30 oc (Castro and Miranda 1998).A number of coastal capes from Bahia to
Rio de Janeiro, Brazil, introduce intense local coastal upwelling downstream of the capes. Upwelling is particularly intense and persistent atCabo Frio (see Chap. 7 by Valentin) where surface temperatures measure
12-18 oc even during the austral summer. The Brazil current converges
with the northward flowing cold-water Malvinas Current between the
mouth of Rio de la Plata and Lagoa dos Patos to form the Subtropical
Convergence in the southwest Atlantic (see Chap. 11 by Odebrecht and
Castello). The predominant flow on either side of the convergence zone
continues towards the east (Fig. 2).
The Caribbean is characterized by a poorly organized surface flow from
the east towards the west-northwest, the so-called Caribbean Current,