L. Stramma et al., THE FLOW-FIELD OFF SOUTHWEST INDIA AT 8N DURING THE SOUTHWEST MONSOONOF AUGUST 1993, Journal of marine research, 54(1), 1996, pp. 55-72
The flow field off the southwest coast of India at 8N was investigated
during RV Sonne cruise 89 in August 1993 by direct velocity observati
ons from shipboard- and lowered-ADCP and geostrophic computations from
CTD stations. The upper ocean between 75E and 76 degrees 52'E near th
e South Indian shelf was governed by a northward flow with a subsurfac
e velocity maximum of 25 cm s(-1) at about 100 m depth. This flow, org
anized as a poleward undercurrent hugging the continental slope, is ty
pical for the southwest monsoon season. The northward transport in Aug
ust 1993 was 4.7 Sv (1 Sverdrup = 10(6) m(3) s(-1)) for the upper 300
m from the shipboard ADCP. Earlier geostrophic observations showed sou
thward surface flow above the poleward undercurrent, but in August 199
3 the northward flow reached to the surface and in the geostrophy calc
ulations, i.e. without the southward Ekman flow near the surface, ther
e was even no clear subsurface core. The T-S characteristics show that
Bay of Bengal Water (BBW) was carried with this flow, and low wind co
nditions seemed to be connected to the flow of BBW from the southern t
ip of Sri Lanka toward the southwest coast of India. Further offshore,
two meridional current bands were identified in the upper 300 m of th
e ocean. West of the coastal undercurrent a band of southward flow exi
sted with velocities up to 35 cm s(-1) above and to the east of the Ch
agos-Laccadive Ridge, from 72 degrees 10'E to 75E. The associated geos
trophic transport in the upper 500 m was 5.2 Sv. As the T-S relation w
as different from that of the northward flow, this current band was no
t a local recirculation of the poleward undercurrent. Further west, th
e flow was weak, but intensified toward the central Arabian Sea, betwe
en 66E and 69 degrees 20'E, where another southward current band was f
ound with velocities of up to 20 cm s(-1) and a total geostrophic tran
sport for the upper 300 m of -7.2 Sv.