Indian Ocean Coastal Biome
297
Although the Somali Current has volume transport almost equivalent to the Gulf
Stream, it changes direction by 180
twice annually under the influence of the seasonally
reversing monsoon winds (Fig. 10.4). At the onset of the Northeast Monsoon of boreal
winter, southward flow develops along the western margin of the Arabian Sea, especially
from northern Somalia (10–11
N, near Cape Guardafui) where onshore flow feeds into
the coastal current. This flow continues to 2–3
S, near the change of orientation of the
Kenyan coastline, where northward flow in the East African Coastal Current (carrying
low-salinity water of SEC origin) converges with it. Here, after merging, both flows, which
Oman
Somalia
JANUARY
NE MONSOON
U
(WEAK)
U
(WEAK)
N o r t h e a s t t r a d e
w
i n d
Z m = >100 m
F i n d l a t e r j e t o f S W
t r a d e w i n d
U
U
U
U
U
UPWELLING
FILAMENT
‘GREAT WHORL’
DOWNWELLING
UPWELLING
JULY
SW MONSOON
(WEAK)
D
(WEAK)
D
D
D
D
D
Fig. 10.4 Idealized diagrams of the ecological consequences of the seasonally reversing monsoon winds over
the Somali Current; redrawn from several sources.