116
P. Picco et al.
5 Conclusions
The analysis of more than 1 year of temporal sériés of currents, température and
salinity in six different sites of the central western part of the Ross Sea Shelf has
permitted us to outline some main characteristics of the circulation in the area
and its temporal variability. In spite of the presence of several water masses in the
Ross Shelf, the strong air-sea-ice interactions and the complicated topography,
the circulation in the layer below 240 m is mainly barotropic with a limited seasonal variability. This suggests that the important current Systems out of the
shelf break (such as the Antarctic Circumpolar Current) could act as a prevailing force for the circulation in the whole shelf, as also indicated by results from
numerical simulations [16].
Spectral analysis shows a large amount of energy on mesoscale frequencies in
ail the moorings. Tidal currents are important, showing a diurnal component
prevalence, sided only in one case (mooring B) by an analogous semidiurnal component. Fortnightly tidal periods are relevant features only far from land and the
ice shelf. Energy distribution on spectra does not change significantly with depth.
Température and salinity time sériés at the depth around 240 m display a limited
seasonal cycle due to the surface processes of ice formation and retreat, but, in
some cases, are modified by the intrusion of different water masses. Higher salinity is found in polynya areas, decreasing moving east and south. Near-bottom température and salinity do not présent any seasonal variation, indicating the constant
presence of the so-called High Salinity Shelf Water, with a température of -1.9 °C
and salinity around 34.8, spreading on the lower levels of the whole shelf.
The resulting annual mean pattern of circulation in the central western sector of the Ross Sea Shelf describes a clockwise gyre with waters moving mainly
northwest along the coasts and the Ice Shelf barrier and recirculating southeast
along the northern part; some slight modifications due to the topography are
observed in the near-bottom level. Currents in front of Cape Adare seem to be
scarcely représentative of the the shelf area, being more directly linked to the
open sea circulation.
Acknowledgements. This work was carried out in the framework of the Italian
National Programme for Antarctic Research.
References
1. PNRA (1995) Rapporto sulla Campagna Antartica Estate Australe 1994/95 X Spedizione. Progetto
Antartide ANT 95/02
2. PNRA (1996) Rapporto sulla Campagna Antartica Estate Australe 1995/96 XI Spedizione. Progetto
Antartide ANT 96/07
3. Kurtz DD, Bromwich DH (1985) A recurring atmospherically forced polynya in Terra Nova Bay. In:
Budillon et al. Oceanology of the Antarctic Continental Shelf. Antarct Res Ser 43:177-202, AGU,
Washington, DC
4. Manzella GMR, Meloni R, and Picco P (1998) Current, température and salinity observations in
the Terra Nova Bay polynya area (This Volume)
P. Picco et al.
5 Conclusions
The analysis of more than 1 year of temporal sériés of currents, température and
salinity in six different sites of the central western part of the Ross Sea Shelf has
permitted us to outline some main characteristics of the circulation in the area
and its temporal variability. In spite of the presence of several water masses in the
Ross Shelf, the strong air-sea-ice interactions and the complicated topography,
the circulation in the layer below 240 m is mainly barotropic with a limited seasonal variability. This suggests that the important current Systems out of the
shelf break (such as the Antarctic Circumpolar Current) could act as a prevailing force for the circulation in the whole shelf, as also indicated by results from
numerical simulations [16].
Spectral analysis shows a large amount of energy on mesoscale frequencies in
ail the moorings. Tidal currents are important, showing a diurnal component
prevalence, sided only in one case (mooring B) by an analogous semidiurnal component. Fortnightly tidal periods are relevant features only far from land and the
ice shelf. Energy distribution on spectra does not change significantly with depth.
Température and salinity time sériés at the depth around 240 m display a limited
seasonal cycle due to the surface processes of ice formation and retreat, but, in
some cases, are modified by the intrusion of different water masses. Higher salinity is found in polynya areas, decreasing moving east and south. Near-bottom température and salinity do not présent any seasonal variation, indicating the constant
presence of the so-called High Salinity Shelf Water, with a température of -1.9 °C
and salinity around 34.8, spreading on the lower levels of the whole shelf.
The resulting annual mean pattern of circulation in the central western sector of the Ross Sea Shelf describes a clockwise gyre with waters moving mainly
northwest along the coasts and the Ice Shelf barrier and recirculating southeast
along the northern part; some slight modifications due to the topography are
observed in the near-bottom level. Currents in front of Cape Adare seem to be
scarcely représentative of the the shelf area, being more directly linked to the
open sea circulation.
Acknowledgements. This work was carried out in the framework of the Italian
National Programme for Antarctic Research.
References
1. PNRA (1995) Rapporto sulla Campagna Antartica Estate Australe 1994/95 X Spedizione. Progetto
Antartide ANT 95/02
2. PNRA (1996) Rapporto sulla Campagna Antartica Estate Australe 1995/96 XI Spedizione. Progetto
Antartide ANT 96/07
3. Kurtz DD, Bromwich DH (1985) A recurring atmospherically forced polynya in Terra Nova Bay. In:
Budillon et al. Oceanology of the Antarctic Continental Shelf. Antarct Res Ser 43:177-202, AGU,
Washington, DC
4. Manzella GMR, Meloni R, and Picco P (1998) Current, température and salinity observations in
the Terra Nova Bay polynya area (This Volume)