120
A. Bergamasco et al.
At the moment, the hypothesis about the circulation of the area is inferred by
different temperature-salinity data sets, mainly vertical profiles, and by a few
time sériés of current meter moorings displaced in the area. The mean circulation of the Ross Sea is mainly west-north-westward; in the western part, waters
seem to describe a cyclonic gyre, with a flow directed southward, which later on
turns back equatorward and closes the gyre itself.
In the eastern part of the Ross Sea, waters along the coast seem partially
directed southward beneath the coast and the Ross Island, entering the RIS, and
partially moving equatorward until Cape Adare, thus originating two separate
gyres [1, 2]. The development of a numerical model could be seen as a tool to
gain more information about the general circulation of the examined area using
dynamic constrains,and to check these results against the patterns up until now
proposed, based merely on T-S distribution.
This work refers to the general circulation of the Ross Sea during JanuaryFebruary 1995, when the second leg of the tenth Italian expédition in Antarctica
took place. Cast profiles explore the major areas; the first one along the RIS
edge, the second one going from mooring F to mooring H, cutting the Ross Sea
from south to north, and the third one from the continental shelf to Terra Nova
Bay and the Drygalsky basin. Unfortunately, the bad weather conditions did not
allow us to completely cover the south-west région, and this will reflect using
traditional objective analysis methods, which could hâve some reliability problems during the reconstruction of the variable fields.
Therefore, a numerical model used for a dynamic adjustment of the interpolated fields can give estimations of T and S consistent with the dynamics
involved. Comparisons between data averages of current meter moorings and
reconstructed current fields give us first validation of the model to reach a
complété vision of the quasi-steady summer circulation of this Antarctic
région.
Phenomenologically speaking, the tenth Antarctic campaign confirmed the
presence of the locally most common water masses: the Antarctic Surface Water
(ASW), the Low Salinity Shelf Water (LSSW), the Deep Ice Water (DIW) and the
High Salinity Shelf Water (HSSW). Figure 1 shows the ensemble plot of ail 152
T-S density casts, measured during the cruise.
From the density plot we can easily see two different bottom water masses,
which are the dense Ross Sea basin water and the lighter circumpolar one. A
clear différentiation is also visible for températures, which are clustered in two
major groups, with an interesting and important température homogeneity for
inside basin waters. Salinity signatures show the HSSW (34.8 PSU, Practical
Salinity Unit) even in the slope, at depths of about 1200 m, while the typical
océan basin salinity near the Ross Sea is about 34.67 PSU. The surface salinity
high variability in the upper 200-m layer is a confirmation of the summer melting processes.
In the following sections, a brief description of the numerical model characteristics and implémentation adopted is given; then a section is dedicated to the
description of forcings factors used. Finally, the discussion of numerical results
and some conclusions and suggestions for future activity are given.
A. Bergamasco et al.
At the moment, the hypothesis about the circulation of the area is inferred by
different temperature-salinity data sets, mainly vertical profiles, and by a few
time sériés of current meter moorings displaced in the area. The mean circulation of the Ross Sea is mainly west-north-westward; in the western part, waters
seem to describe a cyclonic gyre, with a flow directed southward, which later on
turns back equatorward and closes the gyre itself.
In the eastern part of the Ross Sea, waters along the coast seem partially
directed southward beneath the coast and the Ross Island, entering the RIS, and
partially moving equatorward until Cape Adare, thus originating two separate
gyres [1, 2]. The development of a numerical model could be seen as a tool to
gain more information about the general circulation of the examined area using
dynamic constrains,and to check these results against the patterns up until now
proposed, based merely on T-S distribution.
This work refers to the general circulation of the Ross Sea during JanuaryFebruary 1995, when the second leg of the tenth Italian expédition in Antarctica
took place. Cast profiles explore the major areas; the first one along the RIS
edge, the second one going from mooring F to mooring H, cutting the Ross Sea
from south to north, and the third one from the continental shelf to Terra Nova
Bay and the Drygalsky basin. Unfortunately, the bad weather conditions did not
allow us to completely cover the south-west région, and this will reflect using
traditional objective analysis methods, which could hâve some reliability problems during the reconstruction of the variable fields.
Therefore, a numerical model used for a dynamic adjustment of the interpolated fields can give estimations of T and S consistent with the dynamics
involved. Comparisons between data averages of current meter moorings and
reconstructed current fields give us first validation of the model to reach a
complété vision of the quasi-steady summer circulation of this Antarctic
région.
Phenomenologically speaking, the tenth Antarctic campaign confirmed the
presence of the locally most common water masses: the Antarctic Surface Water
(ASW), the Low Salinity Shelf Water (LSSW), the Deep Ice Water (DIW) and the
High Salinity Shelf Water (HSSW). Figure 1 shows the ensemble plot of ail 152
T-S density casts, measured during the cruise.
From the density plot we can easily see two different bottom water masses,
which are the dense Ross Sea basin water and the lighter circumpolar one. A
clear différentiation is also visible for températures, which are clustered in two
major groups, with an interesting and important température homogeneity for
inside basin waters. Salinity signatures show the HSSW (34.8 PSU, Practical
Salinity Unit) even in the slope, at depths of about 1200 m, while the typical
océan basin salinity near the Ross Sea is about 34.67 PSU. The surface salinity
high variability in the upper 200-m layer is a confirmation of the summer melting processes.
In the following sections, a brief description of the numerical model characteristics and implémentation adopted is given; then a section is dedicated to the
description of forcings factors used. Finally, the discussion of numerical results
and some conclusions and suggestions for future activity are given.