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A mean synoptic view of the Subantarctic Front south of Australia


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Phillips, HE and Rintoul, SR 2002 , 'A mean synoptic view of the Subantarctic Front south of Australia' , Journal of Physical Oceanography, vol. 32, no. 5 , pp. 1536-1553 , doi: 10.1175/1520-0485(2002)032<1536:AMSVOT>2.0.CO;2.

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A mean synoptic view of the subantarctic front (SAF) is obtained from current meter and hydrographic data
by averaging absolute and baroclinic velocity measurements in bins defined by a cross-stream coordinate that
moves with the current. The cross-stream coordinate is derived from current meter measurements of vertical
shear of the horizontal velocity and is expressed in terms of specific volume anomaly at 780 dbar (d780). By
averaging absolute and baroclinic velocity measurements in stream coordinates, the spatial smoothing that results
from Eulerian averaging of measurements of a meandering current is avoided. The mean SAF velocity profile
is composed of one central peak and several smaller peaks. In the central peak, the 2-yr mean absolute velocity
from current meters reaches 52 cm/s at 420 dbar; the mean baroclinic velocity from six CTD sections reaches
34 cm/s. The SAF flow is coherent at all levels, reaches the seafloor, and is at least 220 km wide. The crossstream
structure of baroclinic and absolute transport of the SAF has been characterized for the first time. The
integrated mean transport is 116+/-10 (x 10^6 m3/s), of which approximately 14% is barotropic, where barotropic
transport is defined to be the velocity at the deepest current meter (3320 dbar) multiplied by the water depth.
Comparison of the current meter measurements with hydrographic sections suggest this estimate is likely a lower bound on the absolute transport, as part of the 'cold side' of the SAF is not sampled by the moored array. Linear conditions for baroclinic and barotropic instability of the mean flow are satisfied at the array, consistent with earlier work that showed baroclinic conversion is the dominant mechanism for eddy growth at the array, with weaker barotropic conversion also occurring.

Item Type: Article
Authors/Creators:Phillips, HE and Rintoul, SR
Keywords: Antarctic Circumpolar Current, velocity, current meter, instability
Journal or Publication Title: Journal of Physical Oceanography
ISSN: 1520-0485
DOI / ID Number: 10.1175/1520-0485(2002)032<1536:AMSVOT>2.0.CO;2
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