Physical Oceanography of the Indian Ocean
33
Its upper strata have temperatures between 1 ° and 2 ° C, and salinities slightly above
34.70%0 at depths between 500 and 1500 m. This water is of very high nutrient content
and enriches the surface layer by upwelling and upward nutrient fluxes. Below this intermediate temperature and salinity maximum, the transition to the Antarctic bottom water
takes place, which has temperatures less than 0° C and slightly lower salinities near
34.680/00 in the Indian Ocean sector.
IV. The Deep Circulation
The deep circulation can only be inferred from the spreading of characteristic water
masses (Fig. 7), since no direct measurements of the flow are available, and the precision
of dynamic calculations in the very deep layers is poor and affected by the arbitrary choice
10"
.,.
~ .
'?"
If(
JQ'
q
JQ'
II?
ltl"S
0
lOO
000
600
.00
1<10()()
/
1000
~
/
" ~
L~
~
~ I$CO
rSOO
- - - - " stHfrAaS
! SA' iN1"
.............. .. TCIIJlCIlATVII( IfAXIJltII/
MUII/fIII
Altl)lIf",1ICI1i
- - - - - SAL/NIT'! 1I,uIItP.lJl
/
SAtiN" r IIINIIIUII
()XT'C£II II/NIl/fill
lOOO
;;;;un)), n.;;;;,
01'&(11 IIAIIIINIJi
/
IJOO
I
r500
1$'11 10"
.,.
go
,qo
rgo
JQ'
'"
SO"
II?
ltl"S
Fig. 7. Depth of the major core layers along 65° E in the western Indian Ocean together with the
depth of some sigma-t surfaces
of a reference level. In general, it may be concluded that the deep circulation of the Indian
Ocean is weaker than that of the Atlantic Ocean. Both the bottom water and the deep
water are derived from the Atlantic Ocean, and there is no real evidence for the formation
of bottom water along the Antarctic Continent in the Indian Ocean.
The Antarctic bottom water is formed in the Weddell Sea, sinks to the bottom, and
parts of it spread east into the Indian Ocean along the Antarctic continent. Water of less
than 0° C potential temperature penetrates north into the Cape Basin, the East Crozet
Basin and east into the Indian Antarctic Basin, and reaches upwards to 2000 m
near Antarctica. During its spreading it warms slowly, but on its way northward fills all
33
Its upper strata have temperatures between 1 ° and 2 ° C, and salinities slightly above
34.70%0 at depths between 500 and 1500 m. This water is of very high nutrient content
and enriches the surface layer by upwelling and upward nutrient fluxes. Below this intermediate temperature and salinity maximum, the transition to the Antarctic bottom water
takes place, which has temperatures less than 0° C and slightly lower salinities near
34.680/00 in the Indian Ocean sector.
IV. The Deep Circulation
The deep circulation can only be inferred from the spreading of characteristic water
masses (Fig. 7), since no direct measurements of the flow are available, and the precision
of dynamic calculations in the very deep layers is poor and affected by the arbitrary choice
10"
.,.
~ .
'?"
If(
JQ'
q
JQ'
II?
ltl"S
0
lOO
000
600
.00
1<10()()
/
1000
~
/
" ~
L~
~
~ I$CO
rSOO
- - - - " stHfrAaS
! SA' iN1"
.............. .. TCIIJlCIlATVII( IfAXIJltII/
MUII/fIII
Altl)lIf",1ICI1i
- - - - - SAL/NIT'! 1I,uIItP.lJl
/
SAtiN" r IIINIIIUII
()XT'C£II II/NIl/fill
lOOO
;;;;un)), n.;;;;,
01'&(11 IIAIIIINIJi
/
IJOO
I
r500
1$'11 10"
.,.
go
,qo
rgo
JQ'
'"
SO"
II?
ltl"S
Fig. 7. Depth of the major core layers along 65° E in the western Indian Ocean together with the
depth of some sigma-t surfaces
of a reference level. In general, it may be concluded that the deep circulation of the Indian
Ocean is weaker than that of the Atlantic Ocean. Both the bottom water and the deep
water are derived from the Atlantic Ocean, and there is no real evidence for the formation
of bottom water along the Antarctic Continent in the Indian Ocean.
The Antarctic bottom water is formed in the Weddell Sea, sinks to the bottom, and
parts of it spread east into the Indian Ocean along the Antarctic continent. Water of less
than 0° C potential temperature penetrates north into the Cape Basin, the East Crozet
Basin and east into the Indian Antarctic Basin, and reaches upwards to 2000 m
near Antarctica. During its spreading it warms slowly, but on its way northward fills all