General Characteristics of Density-Turbidity Currents in the Ross Sea (Antarctica)
231
tuai along-canyon falling velocity and consequently this “ignition time” of 5 x
104 represents an upper limit for t*.
Ail these considérations underline the fact that no such “ignition” of turbidity
currents has effectively been observed off Victoria land, but also stress that the
general conditions are such that similar phenomena are probable. Indeed, if the
effective pathway of the deep current is questionable (reasonable sources being
possible in many points from the Weddell sea to the Ross Sea), if some rough
topographie particularity or some dynamic external forcing, such as a violent
storm, affects the shelf water then the sinking and ignition of a density-turbidity current appears probable. This is one of the aspects that deserves further
analysis on experimental grounds, also taking into account the climatological
importance of these phenomena.
Acknowledgements. We warmly thank Prof. G. Spezie and Dr. G. Budillon for providing the hydrologie data shown in Fig. 4. We also thank Profs. Pantin, Parker,
Bignami, Levi and Seymour for their help and criticism, as well as Mrs. L.
Santonastaso and R. De Gregorio for typing this manuscript and Dr G.M.R.
Manzella for the valuable help in redrafting it.
References
1. Cavalieri DJ, Martin S (1994) The contributions of Alaskan, Siberian, and Canadian Coastal
polynyas to the cold halocline layer of the Arctic Océan. J Geophys Res 99(18):343-362
2. Caserta A, Mieli E, Salusti E (1990) On a model of bottom érosion by dense water steady veins.
Geophys Astrophys Fluid Dyn 55:117-135
3. Salusti E (1996) A new model for marine density-turbidity currents with criteria for ignition.
Geophys Astrophys Fluid Dyn 83:233-260
4. Nansen F (1906) Northern waters: Captain Roald Amundsen's océanographie observations in the
Arctic Seas in 1901. Skr Nor Vidensk Akad Kl 1 Mat Naturvidensk Kl 3:145
5. Gardner WD (1989) Periodic resupension in Baltimore canyon by focusing of internai waves. J
Geophys Res 94,012:18185-18194
6. Bignami F, Salusti E, Schiarini S (1990) Observations on a bottom vein of dense water in the
Southern Adriatic and Jonian Seas. J Geophys Res 95:7249-7259
7. Chapman DC, Gawarkiewicz G (1995) Offshore transport of dense shelf water in the presence of
a submarine canyon. J Geophys Res 100,07:13373-13387
8. Jiang L, Garwood RW )r ( 1996) Three-dimensional simulations of overflows on continental slopes
J Phys Océan 26:1214-1233
9. Sugimoto T, Whitehead JA (1983) Laboratory models for bay-type continental shelves in the winter. J Phys Océan 13,1819-1828
10. Quadfasel D, Rudels B, Kurz K (1988) Outflow of dense water from a Svalbard fjord into the Fram
strait. Deep Sea Res 35:1143-1150
11. Garrison GR, Becker P (1976) The Barrow submarine canyon: a drain for the Chukchi sea. J
Geophys Res 81:4445-4453
12. Ellison TH, Turner JS (1959) Turbulent entrainment in stratified flows. J Fluid Mech 6:432-448
13. Simpson JE (1982) Gravity currents in the laboratory. Atmos Océan Anny Rev Fluid Mech 14:213234
14. Emms PW (1997) Streamtube models of gravity currents in the océan. Deep-Sea Res in press.
15. Drake DE, Cacchione DA (1986) Field observations of bed shear stress and sédiment resuspension on continental shelves, Alaska and California. Cont Shelf Res 6:415-429
231
tuai along-canyon falling velocity and consequently this “ignition time” of 5 x
104 represents an upper limit for t*.
Ail these considérations underline the fact that no such “ignition” of turbidity
currents has effectively been observed off Victoria land, but also stress that the
general conditions are such that similar phenomena are probable. Indeed, if the
effective pathway of the deep current is questionable (reasonable sources being
possible in many points from the Weddell sea to the Ross Sea), if some rough
topographie particularity or some dynamic external forcing, such as a violent
storm, affects the shelf water then the sinking and ignition of a density-turbidity current appears probable. This is one of the aspects that deserves further
analysis on experimental grounds, also taking into account the climatological
importance of these phenomena.
Acknowledgements. We warmly thank Prof. G. Spezie and Dr. G. Budillon for providing the hydrologie data shown in Fig. 4. We also thank Profs. Pantin, Parker,
Bignami, Levi and Seymour for their help and criticism, as well as Mrs. L.
Santonastaso and R. De Gregorio for typing this manuscript and Dr G.M.R.
Manzella for the valuable help in redrafting it.
References
1. Cavalieri DJ, Martin S (1994) The contributions of Alaskan, Siberian, and Canadian Coastal
polynyas to the cold halocline layer of the Arctic Océan. J Geophys Res 99(18):343-362
2. Caserta A, Mieli E, Salusti E (1990) On a model of bottom érosion by dense water steady veins.
Geophys Astrophys Fluid Dyn 55:117-135
3. Salusti E (1996) A new model for marine density-turbidity currents with criteria for ignition.
Geophys Astrophys Fluid Dyn 83:233-260
4. Nansen F (1906) Northern waters: Captain Roald Amundsen's océanographie observations in the
Arctic Seas in 1901. Skr Nor Vidensk Akad Kl 1 Mat Naturvidensk Kl 3:145
5. Gardner WD (1989) Periodic resupension in Baltimore canyon by focusing of internai waves. J
Geophys Res 94,012:18185-18194
6. Bignami F, Salusti E, Schiarini S (1990) Observations on a bottom vein of dense water in the
Southern Adriatic and Jonian Seas. J Geophys Res 95:7249-7259
7. Chapman DC, Gawarkiewicz G (1995) Offshore transport of dense shelf water in the presence of
a submarine canyon. J Geophys Res 100,07:13373-13387
8. Jiang L, Garwood RW )r ( 1996) Three-dimensional simulations of overflows on continental slopes
J Phys Océan 26:1214-1233
9. Sugimoto T, Whitehead JA (1983) Laboratory models for bay-type continental shelves in the winter. J Phys Océan 13,1819-1828
10. Quadfasel D, Rudels B, Kurz K (1988) Outflow of dense water from a Svalbard fjord into the Fram
strait. Deep Sea Res 35:1143-1150
11. Garrison GR, Becker P (1976) The Barrow submarine canyon: a drain for the Chukchi sea. J
Geophys Res 81:4445-4453
12. Ellison TH, Turner JS (1959) Turbulent entrainment in stratified flows. J Fluid Mech 6:432-448
13. Simpson JE (1982) Gravity currents in the laboratory. Atmos Océan Anny Rev Fluid Mech 14:213234
14. Emms PW (1997) Streamtube models of gravity currents in the océan. Deep-Sea Res in press.
15. Drake DE, Cacchione DA (1986) Field observations of bed shear stress and sédiment resuspension on continental shelves, Alaska and California. Cont Shelf Res 6:415-429