482
D. H. CUSHING:
in the open ocean. During the SW monsoon, it will be seen that a fair proportion of the
Arabian Sea is highly productive. Between 55 and 65° E, the rich area extends south to
15° C. The coast of East Africa from Zanzibar to the South African border, including the
Mozambique Channel, is quite rich. Production is quite high off Ceylon and there is an
extensive area of high production in the eastern tropical ocean with a high peak off
Java, where there is an upwelling system. The poorest area is in the centre of the
southern subtropical anticyclone. The richest areas are in the Arabian upwelling, the
Mozambique Channel and in the eastern tropical oceans. A rough distribution of
productivity during the SW monsoon by area is given in Table 1.
Table 1. Productivity in the Indian Ocean during the SW monsoon
Area
Arabian upwelling
Arabian Sea
Javan upwelling
East tropical ocean
Equatorial region
East Africa and Mozambique Channel
1.16
0.76
0.85
0.70
0.40
0.83
No. of squares
8
16
3
16
18
13
The average productivity for the whole ocean is 0.50 gC m- 2 day-I, which is
surprisingly high. It is a pity that the Bay of Bengal was inadequately sampled during
the SW monsoon, because upwelling probably occurs there off the Orissa coast of India
and east of the Andaman Islands.
Fig. 1 b shows the productivity in gC m -2 day-l in the Indian Ocean during the
period of the NE monsoon. It is immediately obvious that the productivity is considerably
less. Indeed the average for the NE monsoon is 0.15 gC m- 2 day-t, which is less than
one-third of the value in the SW monsoon. The productive areas are less well pronounced;
the equatorial region, the East African coast, the Bay of Bengal and the eastern tropical
ocean are regions of relatively high production (Table 2).
Table 2. Productivity in the Indian Ocean during the NE monsoon
Area
Arabian upwelling
Arabian Sea
Javan upwelling
East tropical ocean
Equatorial region
East Africa and Mozambique Channel
Bay of Bengal
0.23
0.12
0.28
0.26
0.15
0.42
0.21
No. of squares
6
14
1
12
16
10
14
Compared with the SW monsoon period, most regions are reduced by a factor of three,
as expected from the comparison of the averages. In the Arabian Sea, there is a reduction
of five times, as there is in the Arabian upwelling.
2. Secondary Production
In Fig. 3 a is given the distribution of secondary stock as gC m -2 during the SW
monsoon and in Fig. 3 b that during the NE monsoon. The subscripts refer to the number
D. H. CUSHING:
in the open ocean. During the SW monsoon, it will be seen that a fair proportion of the
Arabian Sea is highly productive. Between 55 and 65° E, the rich area extends south to
15° C. The coast of East Africa from Zanzibar to the South African border, including the
Mozambique Channel, is quite rich. Production is quite high off Ceylon and there is an
extensive area of high production in the eastern tropical ocean with a high peak off
Java, where there is an upwelling system. The poorest area is in the centre of the
southern subtropical anticyclone. The richest areas are in the Arabian upwelling, the
Mozambique Channel and in the eastern tropical oceans. A rough distribution of
productivity during the SW monsoon by area is given in Table 1.
Table 1. Productivity in the Indian Ocean during the SW monsoon
Area
Arabian upwelling
Arabian Sea
Javan upwelling
East tropical ocean
Equatorial region
East Africa and Mozambique Channel
1.16
0.76
0.85
0.70
0.40
0.83
No. of squares
8
16
3
16
18
13
The average productivity for the whole ocean is 0.50 gC m- 2 day-I, which is
surprisingly high. It is a pity that the Bay of Bengal was inadequately sampled during
the SW monsoon, because upwelling probably occurs there off the Orissa coast of India
and east of the Andaman Islands.
Fig. 1 b shows the productivity in gC m -2 day-l in the Indian Ocean during the
period of the NE monsoon. It is immediately obvious that the productivity is considerably
less. Indeed the average for the NE monsoon is 0.15 gC m- 2 day-t, which is less than
one-third of the value in the SW monsoon. The productive areas are less well pronounced;
the equatorial region, the East African coast, the Bay of Bengal and the eastern tropical
ocean are regions of relatively high production (Table 2).
Table 2. Productivity in the Indian Ocean during the NE monsoon
Area
Arabian upwelling
Arabian Sea
Javan upwelling
East tropical ocean
Equatorial region
East Africa and Mozambique Channel
Bay of Bengal
0.23
0.12
0.28
0.26
0.15
0.42
0.21
No. of squares
6
14
1
12
16
10
14
Compared with the SW monsoon period, most regions are reduced by a factor of three,
as expected from the comparison of the averages. In the Arabian Sea, there is a reduction
of five times, as there is in the Arabian upwelling.
2. Secondary Production
In Fig. 3 a is given the distribution of secondary stock as gC m -2 during the SW
monsoon and in Fig. 3 b that during the NE monsoon. The subscripts refer to the number