The Southern Ocean
445
Fig. 12.2 Regional circulation pattern of the Southern Ocean, as influenced by land mass distribution,
to show the arrangement of the ecological provinces of austral regions, viz. APLR, ANTA, SANT, SSTC;
(AD = Antarctic divergence, APF = Antarctic Polar Front, SAF = Subantarctic Front, STC = Subtropical
Convergence).
This zone is associated with a zonal band of strong mesoscale meanders and eddies that
occupy ∼5
of latitude. Meander formation is strongest to the east of Patagonia, of South
Africa, and of Tasmania and New Zealand, and also in the South Pacific at Crozet Island
and the Kerguelen-Heard plateau. Motion of the detached eddies is complex and depends
on interaction with the general field of potential vorticity.
The transitions to subtropical and to subantarctic surface waters on either side of the
zone have frontal characteristic; the term Subtropical Front (STF) is now usually applied
to the more poleward of the pair. Here, the entire convergence zone between these fronts
shall be referred to as the South Subtropical Convergence Province (SSTC). The STF,
therefore, lies on the poleward side of a fast zonal jet that occupies the upper 1000 m as
it flows to the east (Stramma and Petersen, 1990; Stramma, 1992). On the cold side of
the STF, low-salinity subantarctic surface water converges with the modified subtropical
surface water of the frontal jet and passes beneath it. The STF forms an almost continuous
and prominent feature around the entire Southern Ocean.
Subantarctic Water Ring. This is the most complex entity to grasp. It comprises the
two current cores within the ACC and the slower-moving flow of the subantarctic surface
water mass between these cores and the STF. The two relatively fast, constricted flows lie
to the south of the slower flow and together form the Polar Frontal Zone (Anonymous,
1989). This zone, which is embedded in the Subantarctic Water Ring, is defined by two
fronts at which the shoaling, upsloping isotherms and isohalines are more tightly clustered
than elsewhere in the ACC: these fronts are the relatively weak Subantarctic Front (SAF)
and the stronger Polar Front (PF). The location of the latter corresponds approximately
445
Fig. 12.2 Regional circulation pattern of the Southern Ocean, as influenced by land mass distribution,
to show the arrangement of the ecological provinces of austral regions, viz. APLR, ANTA, SANT, SSTC;
(AD = Antarctic divergence, APF = Antarctic Polar Front, SAF = Subantarctic Front, STC = Subtropical
Convergence).
This zone is associated with a zonal band of strong mesoscale meanders and eddies that
occupy ∼5
of latitude. Meander formation is strongest to the east of Patagonia, of South
Africa, and of Tasmania and New Zealand, and also in the South Pacific at Crozet Island
and the Kerguelen-Heard plateau. Motion of the detached eddies is complex and depends
on interaction with the general field of potential vorticity.
The transitions to subtropical and to subantarctic surface waters on either side of the
zone have frontal characteristic; the term Subtropical Front (STF) is now usually applied
to the more poleward of the pair. Here, the entire convergence zone between these fronts
shall be referred to as the South Subtropical Convergence Province (SSTC). The STF,
therefore, lies on the poleward side of a fast zonal jet that occupies the upper 1000 m as
it flows to the east (Stramma and Petersen, 1990; Stramma, 1992). On the cold side of
the STF, low-salinity subantarctic surface water converges with the modified subtropical
surface water of the frontal jet and passes beneath it. The STF forms an almost continuous
and prominent feature around the entire Southern Ocean.
Subantarctic Water Ring. This is the most complex entity to grasp. It comprises the
two current cores within the ACC and the slower-moving flow of the subantarctic surface
water mass between these cores and the STF. The two relatively fast, constricted flows lie
to the south of the slower flow and together form the Polar Frontal Zone (Anonymous,
1989). This zone, which is embedded in the Subantarctic Water Ring, is defined by two
fronts at which the shoaling, upsloping isotherms and isohalines are more tightly clustered
than elsewhere in the ACC: these fronts are the relatively weak Subantarctic Front (SAF)
and the stronger Polar Front (PF). The location of the latter corresponds approximately