UPWELLING AND THE PRODUCTION OF FISH
263
Equatorial Current near the equator. The same point is made in Fig. 13
(p. 295) showing the distribution of radiocarbon observations, u iiarrow
productive band at the equator in the eastern ocean above the Cromwell Undercurrent. The seasonal variation of the equatorinl systcm has
been described in the Pacific by Knauss (1963) and Table I summarizes his findings.
TABLE I
North
SOUllb
Cuwent
Current
Seuaon
Equdorial
Countercuwent
Equalorid
September to January
February to April
May to J u l y
July, August
Weak
Weak
Strong
Strong
None
Weak
Strong
Strong
Weak
Weak
Strong
Strong
(ICnauss, 1963)
Figure 4 is a diagram of the seasonal cycle of upwelling in an eastern
boundary current and in the equatorial system. It is based partly on
Wooster and Reid's (1963) estimates of Ekman transport normal to the
\
t t
Winter
I
I I I I
1 V l l l
Summer
4 0
'
\Spring
Autumn
Coastal upwelling
Current
I
1 Divergence 2 Convergence
Extensive area of divergence
Fro. 4. Diagram of the seasonal cycle of upwelling in an eastern boundary current and
of divergence in an equatorial current, based very roughly on tho system in North
Pacific anticyclone.