426
that enters and leaves the region of area A, respectively. This water flux is the combination
of southward geostrophic and Ekman flow , about 3-5 Sv (Stramma and Isemer 1988,
Stramma and Siedler 1988, Schmitz and McCartney 1993, Arhan et al. 1994). With
A = 3.4 X 10 12 m 2 , 8; = 19°C, 80 = 24°C and V = 4 Sv this gives 23 W 1m 2 . These
numbers agree with those results indicative of relatively small heat transport divergence
as compared to heat influx density, but not at all negligible. This supports the idea
that a significant portion of the resulting WWM may directly recirculate into the western
NASG, as combined Ekman and geostrophic heat transport, and become a major path of
heat export into the northern North Atlantic (Csanady 1986).
From April to September WWM is formed at a rate which may be estimated multiplying 23 W 1m 2 by the area A, giving 7.8 x 10 13 W. For this same period Stramma
and Isemer (1988) found that between 30 0 N and 200N the meridional total heat transport
convergence is about three times larger, which allows not only for zonal heat recirculation
but also for local heat collection (Fig. 4). From September to April WWM formation
ceases, except in the coastal upwelling region (see below). The annually averaged heat
flux used to create WWM over this region is obtained from our previous estimate, taking
into account that WWM is formed only during half of the year, as about 4 x 10 13 W.
""''-~'().6 .:r,~ :y::...,~-T--.-~ Q3 :..; I.;:.: 'tPW ..;,:...; ().6 ~.-N
35 -
-
WlnI(W
...• ""''0
•••• SUn"ln"lef
- - taU
25'
15'
..... ~
- - lall
I 10'
_____ I
L-________________ ~ ________ ~
Figure 4. Total (left), geostrophic (center) , and Ekman (right) meridional heat transport in the eastern NASG (between 30 0 30'W and the African coastline); reproduced from
Stramma and Isemer (1988).
Upwelling off Northwest Africa
Many studies have looked at the mean hydrographic conditions and temporal variability off northwest Africa (Fedosev 1970, Jones 1972, Hughes and Barton 1974, Wooster
that enters and leaves the region of area A, respectively. This water flux is the combination
of southward geostrophic and Ekman flow , about 3-5 Sv (Stramma and Isemer 1988,
Stramma and Siedler 1988, Schmitz and McCartney 1993, Arhan et al. 1994). With
A = 3.4 X 10 12 m 2 , 8; = 19°C, 80 = 24°C and V = 4 Sv this gives 23 W 1m 2 . These
numbers agree with those results indicative of relatively small heat transport divergence
as compared to heat influx density, but not at all negligible. This supports the idea
that a significant portion of the resulting WWM may directly recirculate into the western
NASG, as combined Ekman and geostrophic heat transport, and become a major path of
heat export into the northern North Atlantic (Csanady 1986).
From April to September WWM is formed at a rate which may be estimated multiplying 23 W 1m 2 by the area A, giving 7.8 x 10 13 W. For this same period Stramma
and Isemer (1988) found that between 30 0 N and 200N the meridional total heat transport
convergence is about three times larger, which allows not only for zonal heat recirculation
but also for local heat collection (Fig. 4). From September to April WWM formation
ceases, except in the coastal upwelling region (see below). The annually averaged heat
flux used to create WWM over this region is obtained from our previous estimate, taking
into account that WWM is formed only during half of the year, as about 4 x 10 13 W.
""''-~'().6 .:r,~ :y::...,~-T--.-~ Q3 :..; I.;:.: 'tPW ..;,:...; ().6 ~.-N
35 -
-
WlnI(W
...• ""''0
•••• SUn"ln"lef
- - taU
25'
15'
..... ~
- - lall
I 10'
_____ I
L-________________ ~ ________ ~
Figure 4. Total (left), geostrophic (center) , and Ekman (right) meridional heat transport in the eastern NASG (between 30 0 30'W and the African coastline); reproduced from
Stramma and Isemer (1988).
Upwelling off Northwest Africa
Many studies have looked at the mean hydrographic conditions and temporal variability off northwest Africa (Fedosev 1970, Jones 1972, Hughes and Barton 1974, Wooster