78
v- Gouretski
water escapes to the north, filling large areas of the deep océan in the lower latitudes. Whereas a large number of studies hâve been conducted for the Weddell
Gyre, the Ross Gyre (with the exception of the offshore areas of the Ross Sea) still
remains one of the least sampled in the Southern Océan.
The first maps indicative of a cyclonic circulation pattern south of the
Antarctic Polar Front (APF) in the Pacific sector of the Southern Océan were compiled by Treshnikov [2]. Reid and Mantyla [3] produced dynamic height maps,
which implied a single cyclonic gyre from about 160°E to 130°W or a number of
dosed circulations between these longitudes. Reid [4] hypothesised an extension
of the Ross Gyre to the Antarctic Peninsula, though his property maps were based
on only 1780 stations for the whole South Pacific. Levitus [5] and later Olberset
al. [6] used much larger datasets to produce new maps of the Southern Océan,
which indicate the eastern boundary of the Gyre at about 140°W. The first quasisynoptic description of the Ross Gyre was given by Antipov et al. [7] and
Maslennikov [8]. It was based on quasi-synoptic data from nine méridional sections between 167.5°E and 132.5°W. The authors put the eastern boundary of the
Gyre at about 140°W and give detailes of the northern boundary. A descriptive
study of the physical oceanography of the South Pacific is given by Patterson and
Whitworth [9], Locarnini [10] présents a comprehensive analysis of the Ross Gyre
and its environs. He also locates the eastern end of the Ross Gyre near 140°W in
the upper and mid-depth levels.
The goal of this study is to improve the climatological description of the Ross
Gyre. In a déviation from earlier studies our results are based on a much larger
dataset of modem and historical hydrographie data. These quality controlled data
with accounts made for inter-cruise offsets for salinity, oxygen and nutrients
allow a detailed description of the water masses, fronts and circulation within the
offshore area of the Ross Gyre.
2 Data and Methods
A set of hydrographie data for the area between 130°E and 100°W is used here
to inter large-scale thermohaline and circulation patterns of the Ross Gyre.
Most of the data came from the World Océan Atlas [11], Southern Océan
Hydrographie Atlas Data Base [6] and hydrographie lines S4, P16A and P17A,
occupied during the World Océan Circulation Experiment (WOCE). Figure 1
shows the location of 7164 hydrographie stations south of 40°S used for this
study. South of 57°S (taken crudely as a mean position of the APF) the dataset
consists of 3597 stations. Our collection differs from the previous studies in the
inclusion of additional data collected in the Ross Gyre area in the 1980s and
1990s. Thus, Russian expéditions from 1985 to 1986 [7,12] contributed with 272
profiles, and WOCE Pacific lines S4, P16A and P17A provided 338 profiles. Since
t e focus of this study is on the deep océan we used only bottle and low-resoution CTD casts obtained over depths greater than 200 m with up to six parameters gis en at observed levels: température, salinity, oxygen, silicate, nitrate
and phosphate. Despite the inclusion of the additional data the data coverage is
still insufficient south of 70°S and east of 150°W. A survey in early 1994 made
v- Gouretski
water escapes to the north, filling large areas of the deep océan in the lower latitudes. Whereas a large number of studies hâve been conducted for the Weddell
Gyre, the Ross Gyre (with the exception of the offshore areas of the Ross Sea) still
remains one of the least sampled in the Southern Océan.
The first maps indicative of a cyclonic circulation pattern south of the
Antarctic Polar Front (APF) in the Pacific sector of the Southern Océan were compiled by Treshnikov [2]. Reid and Mantyla [3] produced dynamic height maps,
which implied a single cyclonic gyre from about 160°E to 130°W or a number of
dosed circulations between these longitudes. Reid [4] hypothesised an extension
of the Ross Gyre to the Antarctic Peninsula, though his property maps were based
on only 1780 stations for the whole South Pacific. Levitus [5] and later Olberset
al. [6] used much larger datasets to produce new maps of the Southern Océan,
which indicate the eastern boundary of the Gyre at about 140°W. The first quasisynoptic description of the Ross Gyre was given by Antipov et al. [7] and
Maslennikov [8]. It was based on quasi-synoptic data from nine méridional sections between 167.5°E and 132.5°W. The authors put the eastern boundary of the
Gyre at about 140°W and give detailes of the northern boundary. A descriptive
study of the physical oceanography of the South Pacific is given by Patterson and
Whitworth [9], Locarnini [10] présents a comprehensive analysis of the Ross Gyre
and its environs. He also locates the eastern end of the Ross Gyre near 140°W in
the upper and mid-depth levels.
The goal of this study is to improve the climatological description of the Ross
Gyre. In a déviation from earlier studies our results are based on a much larger
dataset of modem and historical hydrographie data. These quality controlled data
with accounts made for inter-cruise offsets for salinity, oxygen and nutrients
allow a detailed description of the water masses, fronts and circulation within the
offshore area of the Ross Gyre.
2 Data and Methods
A set of hydrographie data for the area between 130°E and 100°W is used here
to inter large-scale thermohaline and circulation patterns of the Ross Gyre.
Most of the data came from the World Océan Atlas [11], Southern Océan
Hydrographie Atlas Data Base [6] and hydrographie lines S4, P16A and P17A,
occupied during the World Océan Circulation Experiment (WOCE). Figure 1
shows the location of 7164 hydrographie stations south of 40°S used for this
study. South of 57°S (taken crudely as a mean position of the APF) the dataset
consists of 3597 stations. Our collection differs from the previous studies in the
inclusion of additional data collected in the Ross Gyre area in the 1980s and
1990s. Thus, Russian expéditions from 1985 to 1986 [7,12] contributed with 272
profiles, and WOCE Pacific lines S4, P16A and P17A provided 338 profiles. Since
t e focus of this study is on the deep océan we used only bottle and low-resoution CTD casts obtained over depths greater than 200 m with up to six parameters gis en at observed levels: température, salinity, oxygen, silicate, nitrate
and phosphate. Despite the inclusion of the additional data the data coverage is
still insufficient south of 70°S and east of 150°W. A survey in early 1994 made