The Large-Scale Thermohaline Structure
of the Ross Gyre
V. Gouretski
WHP Spécial Analysis Centre (jointly operated by Max-Planck-Institut für Météorologie
und Bundesamt für Seeschiffahrt und Hydrographie), Bernhard-Nocht Str. 78,
20359 Hamburg, Germany
Abstract
This study describes the large-scale thermohaline structure and circulation patterns of the Ross Gyre and is based on a quality controlled data set including
about 7,000 historical and modem hydrographie stations. A new régional climatology was obtained through the objective analysys of the data on neutral surfaces. Steric height anomaly maps portray Ross Gyre as a dépréssion south of the
mid-ocean ridge between about 170°E and 140°W. The centre of the gyre shifts
with depth from about 68°S 164°W in near surface levels to about 63oS 150oW at
1500 meters. Maximum estimate of the geostrophic transport within the gyre is
8.5 Sv near 150°W, a factor of three lower than corresponding estimâtes for the
Weddell Gyre. Data from a quasi-synoptic survey made by three former U.S.S.R
vessels in 1985-86 are used for a more detailed description of the gyre’s northern, eastern and Southern boundaries. Similar to the Weddell Gyre the location
of the eastern boundary is controlled by the southward extension of the
Antarctic Circumpolar Current core flowing through the Udintsev Fracture Zone
with the geostrophic transport of 56 Sv. The Circumpolar Deep Water spreads
westwards along the Southern limb of the gyre with potential températures still
as high as 1.6 °C at 75°S, 150°W.
1 Introduction
The area of the Southern Océan south of the Antarctic Polar Front (APF) is characterized by a net heat loss to the atmosphère. This loss of heat is compensated by
the poleward heat transport in the océan [1]. A cyclonic wind-stress field exerted
on the océan surface south of the Antarctic Circumpolar Current (ACC) in combination with the bottom topography créâtes two large-scale cyclonic circulations
in the Southern Océan: the Weddell Gyre in the Atlantic sector and the Ross Gyre
in the Pacific sector. These cyclonic circulations facilitate southward transport of
the Circumpolar Deep Water (CDW) from the Southern margins of the ACC to the
Antarctic continental shelves, thus providing a large-scale mechanism for the
southward heat and sait transports. The CDW, entrained along the eastern limbs
of the gyres, is modified due to strong interaction with shelf and slope waters,
thus producing Antarctic Bottom water (AABW). Some of this cold and dense
of the Ross Gyre
V. Gouretski
WHP Spécial Analysis Centre (jointly operated by Max-Planck-Institut für Météorologie
und Bundesamt für Seeschiffahrt und Hydrographie), Bernhard-Nocht Str. 78,
20359 Hamburg, Germany
Abstract
This study describes the large-scale thermohaline structure and circulation patterns of the Ross Gyre and is based on a quality controlled data set including
about 7,000 historical and modem hydrographie stations. A new régional climatology was obtained through the objective analysys of the data on neutral surfaces. Steric height anomaly maps portray Ross Gyre as a dépréssion south of the
mid-ocean ridge between about 170°E and 140°W. The centre of the gyre shifts
with depth from about 68°S 164°W in near surface levels to about 63oS 150oW at
1500 meters. Maximum estimate of the geostrophic transport within the gyre is
8.5 Sv near 150°W, a factor of three lower than corresponding estimâtes for the
Weddell Gyre. Data from a quasi-synoptic survey made by three former U.S.S.R
vessels in 1985-86 are used for a more detailed description of the gyre’s northern, eastern and Southern boundaries. Similar to the Weddell Gyre the location
of the eastern boundary is controlled by the southward extension of the
Antarctic Circumpolar Current core flowing through the Udintsev Fracture Zone
with the geostrophic transport of 56 Sv. The Circumpolar Deep Water spreads
westwards along the Southern limb of the gyre with potential températures still
as high as 1.6 °C at 75°S, 150°W.
1 Introduction
The area of the Southern Océan south of the Antarctic Polar Front (APF) is characterized by a net heat loss to the atmosphère. This loss of heat is compensated by
the poleward heat transport in the océan [1]. A cyclonic wind-stress field exerted
on the océan surface south of the Antarctic Circumpolar Current (ACC) in combination with the bottom topography créâtes two large-scale cyclonic circulations
in the Southern Océan: the Weddell Gyre in the Atlantic sector and the Ross Gyre
in the Pacific sector. These cyclonic circulations facilitate southward transport of
the Circumpolar Deep Water (CDW) from the Southern margins of the ACC to the
Antarctic continental shelves, thus providing a large-scale mechanism for the
southward heat and sait transports. The CDW, entrained along the eastern limbs
of the gyres, is modified due to strong interaction with shelf and slope waters,
thus producing Antarctic Bottom water (AABW). Some of this cold and dense