198
S. Tucci et al.
Program organized the X Italian Expédition in the Ross Sea. Within this framework, the C.L.I.M.A. Project (Climatic Long-term Interaction for the Massbalance
in Antarctica) carried out its first océanographie cruise. The aim was to improve
the characterization of the most important water masses and to study the general circulation inside the Ross Sea. From 7 January to 20 February 1995 a sériés of
154 CTD casts were performed, and 3 moorings were deployed in order to monitor the annual variability of water fluxes and suspended sédiments. One year later,
during the XI Expédition from 12 January to 5 February 1996, the moorings were
recovered and repositioned; 28 sampling stations were also recorded during these
operations.
This paper discusses some parameters regarding suspended matter in the
water off the Ross Ice Shelf (RIS). These results hâve enabled us to define the origin and dynamics of the suspended matter and outline a general hypothesis on
actual sédimentation during the austral summer. Data on the composition of the
suspended matter will be assessed together with seasonal flow values in Chapter
by Accornero et al., this volume [3].
2 Instrumentation and Analysis
The hydrological stations used a multi-parameter SBE 9/11 plus probe from SeaBird Electronics equipped with a Carousel SBE 32 unit with 24 121-bottles.
Samples of suspended matter were taken at 122 of the stations at depths calculât -
ed according to the hydrological profile (always one sample on the surface, one
under the thermocline, one in the intermediate waters and one close to the bottom); on board, the samples were subdivided and subjected to different filtrations
in order to préparé them for the subséquent laboratory investigations to be performed on the suspended load. Déterminations were performed according to the
methods reported in Strickland and Parsons [4]. In this phase the total concentration data related to dimensional analyses of suspended matter were used [5].
The dimensional analyses were carried out on board using a Coulter® Counter
Multisizer with a double sampling cell; a 30pm capillary was used to define the
fine fraction and a 140pm capillary to define the larger fraction; this dual analysis provided reliable results in the range 0.6 to lOOpm [6].
3 Results and Discussion
The first step was to locate the température minimum along the RIS, as these waters
are thought, to play an important rôle in the general dynamics of the Ross Sea. For
this purpose a survey was carried out along the RIS front from longitude 170° E to
167° W (Stations 3-21; Fig. 1). A water mass of interest was identified at 178° W,centered on stations 9 to 15; it has température values lower than -2.00 °C at depths in
the range 300 to 500 m. In this sector, sampling was performed northwards, with
stations 85 and 86 up to the limit of the shelf. This confirms the results of Jacobs et
al. [7] who identified the presence of“supercold waters” that defined Ross Ice Shelf
Waters (RISW). Finding this situation almost in the same sector of the shelf and at
S. Tucci et al.
Program organized the X Italian Expédition in the Ross Sea. Within this framework, the C.L.I.M.A. Project (Climatic Long-term Interaction for the Massbalance
in Antarctica) carried out its first océanographie cruise. The aim was to improve
the characterization of the most important water masses and to study the general circulation inside the Ross Sea. From 7 January to 20 February 1995 a sériés of
154 CTD casts were performed, and 3 moorings were deployed in order to monitor the annual variability of water fluxes and suspended sédiments. One year later,
during the XI Expédition from 12 January to 5 February 1996, the moorings were
recovered and repositioned; 28 sampling stations were also recorded during these
operations.
This paper discusses some parameters regarding suspended matter in the
water off the Ross Ice Shelf (RIS). These results hâve enabled us to define the origin and dynamics of the suspended matter and outline a general hypothesis on
actual sédimentation during the austral summer. Data on the composition of the
suspended matter will be assessed together with seasonal flow values in Chapter
by Accornero et al., this volume [3].
2 Instrumentation and Analysis
The hydrological stations used a multi-parameter SBE 9/11 plus probe from SeaBird Electronics equipped with a Carousel SBE 32 unit with 24 121-bottles.
Samples of suspended matter were taken at 122 of the stations at depths calculât -
ed according to the hydrological profile (always one sample on the surface, one
under the thermocline, one in the intermediate waters and one close to the bottom); on board, the samples were subdivided and subjected to different filtrations
in order to préparé them for the subséquent laboratory investigations to be performed on the suspended load. Déterminations were performed according to the
methods reported in Strickland and Parsons [4]. In this phase the total concentration data related to dimensional analyses of suspended matter were used [5].
The dimensional analyses were carried out on board using a Coulter® Counter
Multisizer with a double sampling cell; a 30pm capillary was used to define the
fine fraction and a 140pm capillary to define the larger fraction; this dual analysis provided reliable results in the range 0.6 to lOOpm [6].
3 Results and Discussion
The first step was to locate the température minimum along the RIS, as these waters
are thought, to play an important rôle in the general dynamics of the Ross Sea. For
this purpose a survey was carried out along the RIS front from longitude 170° E to
167° W (Stations 3-21; Fig. 1). A water mass of interest was identified at 178° W,centered on stations 9 to 15; it has température values lower than -2.00 °C at depths in
the range 300 to 500 m. In this sector, sampling was performed northwards, with
stations 85 and 86 up to the limit of the shelf. This confirms the results of Jacobs et
al. [7] who identified the presence of“supercold waters” that defined Ross Ice Shelf
Waters (RISW). Finding this situation almost in the same sector of the shelf and at