Mc. Mccarthy et Ld. Talley, Three-dimensional isoneutral potential vorticity structure in the Indian Ocean, J GEO RES-O, 104(C6), 1999, pp. 13251-13267
The three-dimensional isoneutral potential vorticity structure of the India
n Ocean is examined using World Ocean Circulation Experiment and National O
ceanic and Atmospheric Administration conductivity-temperature-depth data a
nd historical bottle data. The distribution of the potential vorticity is s
et by the Indian Ocean's source waters and their circulation inside the bas
in. The lower thermocline has a high potential vorticity signal extending w
estward from northwest of Australia and a low signal from the Subantarctic
Mode Water in the south. The Antarctic Intermediate Water inflow creates pa
tches of high potential vorticity at intermediate depths in the southern In
dian Ocean, below which the field becomes dominated by planetary vorticity,
indicating a weaker meridional circulation and weaker potential vorticity
sources. Wind-driven gyre depths have lower potential vorticity gradients p
rimarily due to same-source waters. Homogenization and western shadow zones
are not observed. The P-effect dominates the effect of the Somali Current
and the Red Sea Water on the potential vorticity distribution. Isopleths ti
lt strongly away from latitude lines in the deep and abyssal waters as the
Circumpolar Deep Water fills the basins in deep western boundary currents,
indicating a strong meridional circulation north of the Antarctic Circumpol
ar Current. The lower-gradient intermediate layer surrounded vertically by
layers with higher meridional potential vorticity gradients in the subtropi
cal Indian Ocean suggests that Rossby waves will travel similar to 1.3 time
s faster than standard theory predicts. To the south, several pools of homo
genized potential vorticity appear in the upper 2000 m of the Southern Ocea
n where gyres previously have been identified. South of Australia the abyss
al potential vorticity structure is set by a combination of the Antarctic C
ircumpolar Current and the bathymetry.