68
A. Russo et al.
New Zealand coast and our XBT launches started quite offshore, so STF was not
detected. In the same area, the Southern front and the Boundary are very close to
each other and are not distinguished, so we will deal with the Southern front only,
intending that the Boundary is close or coincident with it.
To define these fronts, a number of tracers has been used (température, salinity, dissolved oxygen, nutrient salts content, etc.). We hâve only upper-layer température data available; nevertheless, they can be identified using the following
définitions derived from the previously reported authors:
SAF:
T > 4 °C at 400 m [3]
PF:
northern limit of subsurface Tmin < 2 °C at z < 200 m [2,3]
Southern front: northern limit of subsurface Tmin < 0 °C and T > 1.8 °C at
depth > 500 m [3]
A brief description of data set and methodology is reported in Section 2. In
Section 3 the fronts are defined, and a splitting into a “northern” and a “Southern”
part of the SAF as a permanent feature of this sector, rather than occasional, as
observed in the Tasmanian sector by Belkin and Gordon [2] and Rintoul et al. [4],
is sustained; consequently, names and définitions for these two fronts are given. A
description of the thermal characteristics of the six sections follows, with a number of observed cold eddies and/or meanders, in particular water bodies detached
from the Polar Front. In the final section, results are summarised.
2 Data
In the framework of the CLIMA (Climatic Long-term Interaction for the Mass
balance in Antarctica) project, six high-resolution XBT sections were obtained by
the R/V “Italica” during its routes from New Zealand to the Ross Sea and return.
Four sections were collected during the austral spring/summer 1994-1995 and
two sections during the austral summer 1995-1996 (see Fig. 1 for the local
bathimetry, XBT launch positions and cruise dates). The used XBTs were Sippican
T-7, characterised by a maximum depth of 760 m and a depth resolution of 0.6 m.
The probes were not calibrated onboard; we accepted the factory declared accuracy of 0.15 °C as they were built and shipped by the factory just before the beginning of each expédition. Spacing between launches varied from 10 to 40 km, with
an increased resolution in the area in which the PF was supposed to be. In a few
cases the resolution was coarser due to poor weather or to marine ice cover; most
of the faulty probes (less than 10% in total) were recognised during the data
acquisition and these launches were immediately repeated. In the post-processing
phase, other erroneous profiles were detected and partially or totally rejected.
A. Russo et al.
New Zealand coast and our XBT launches started quite offshore, so STF was not
detected. In the same area, the Southern front and the Boundary are very close to
each other and are not distinguished, so we will deal with the Southern front only,
intending that the Boundary is close or coincident with it.
To define these fronts, a number of tracers has been used (température, salinity, dissolved oxygen, nutrient salts content, etc.). We hâve only upper-layer température data available; nevertheless, they can be identified using the following
définitions derived from the previously reported authors:
SAF:
T > 4 °C at 400 m [3]
PF:
northern limit of subsurface Tmin < 2 °C at z < 200 m [2,3]
Southern front: northern limit of subsurface Tmin < 0 °C and T > 1.8 °C at
depth > 500 m [3]
A brief description of data set and methodology is reported in Section 2. In
Section 3 the fronts are defined, and a splitting into a “northern” and a “Southern”
part of the SAF as a permanent feature of this sector, rather than occasional, as
observed in the Tasmanian sector by Belkin and Gordon [2] and Rintoul et al. [4],
is sustained; consequently, names and définitions for these two fronts are given. A
description of the thermal characteristics of the six sections follows, with a number of observed cold eddies and/or meanders, in particular water bodies detached
from the Polar Front. In the final section, results are summarised.
2 Data
In the framework of the CLIMA (Climatic Long-term Interaction for the Mass
balance in Antarctica) project, six high-resolution XBT sections were obtained by
the R/V “Italica” during its routes from New Zealand to the Ross Sea and return.
Four sections were collected during the austral spring/summer 1994-1995 and
two sections during the austral summer 1995-1996 (see Fig. 1 for the local
bathimetry, XBT launch positions and cruise dates). The used XBTs were Sippican
T-7, characterised by a maximum depth of 760 m and a depth resolution of 0.6 m.
The probes were not calibrated onboard; we accepted the factory declared accuracy of 0.15 °C as they were built and shipped by the factory just before the beginning of each expédition. Spacing between launches varied from 10 to 40 km, with
an increased resolution in the area in which the PF was supposed to be. In a few
cases the resolution was coarser due to poor weather or to marine ice cover; most
of the faulty probes (less than 10% in total) were recognised during the data
acquisition and these launches were immediately repeated. In the post-processing
phase, other erroneous profiles were detected and partially or totally rejected.