|Abstract or Summary
- The distribution of Antarctic Intermediate Water in the South
Pacific has been examined using a model of horizontal advection,
along the Sigma-t surface 27.10, with three point vertical mixing.
The core of the Antarctic Intermediate Water mass was traced
from the Antarctic Convergence northward. The charts used to
describe the distribution were those of core depth, salinity, percentage
composition, Equivalent Thickness, and acceleration potential.
The percentage composition of Antarctic Intermediate Water
in the entire water column for all stations was computed and the
Equivalent Thickness determined. Intermediate water volume for
the South Pacific was then calculated. North-South geostrophic
velocities and transports were computed for two zonal sections.
The model agreed quite well with the flow patterns reported by
other investigators. The broad counterclockwise gyre in the central
South Pacific, the flow into the Tasman and Coral Seas, the localized flow near New Zealand, and the suggestion of southward flow near
the South American Coast are all indicated by the model. A previously
unreported small, counterclockwise gyre in the southeast
South Pacific was detected. The circulation within the small gyre
is consistent wity flow over a variable bottom in the Southern Hemisphere.
Antarctic Intermediate Water transport across selected
sections indicate a northward flow of 10 x 10⁶ m³ sec⁻¹. A low
salinity tongue was found on the salinity chart. This tongue extended
northward, then westward, into the northern Tasman Sea. The
salinity was over 34.50°/₀₀ in the center of this counterclockwise
motion east of New Zealand. The isohalines in the southeast Pacific
suggest the presence of the small counterclockwise gyre. A 20
percent drop in core percentage composition was noted in the 10 degrees
north of the Antarctic Convergence. A large uniform area
between 80 percent and 70 percent over the central portion of the
central South Pacific was bounded on the north by a 20 percent drop
near the equator, again supporting the general counterclockwise
The Equivalent Thickness distribution showed a general lenticular
shape, the thickest part lying in the center of the counterclockwise
gyre east of New Zealand. The Equivalent Thickness distribution,
as well as the core percentage, supported the hypothesis of
little or no flow into the Tasman Sea from the south. The volume of intermediate water obtained from surface area integration of the
Equivalent Thickness distribution was 59.44 x 10⁶ km³. This is
approximately 16% of the water volume in the South Pacific.