Diapycnal mixing and internal waves in the Saint John River Estuary, New Brunswick, Canada with a discussion relative to the Baltic Sea; pp. 157–175Full article in PDF format
| doi: 10.3176/eng.2010.2.05
Abstract Results of a detailed oceanographic survey in the Saint John River Estuary, New Brunswick, Canada are presented. It is shown that interfacial mixing occurs in this highly stratified basin at discrete locations at a particular phase of the tide leading to a plunging pycnocline at most of these locations. This process is possibly initiated by different kind of internal waves or/and the changing velocity direction on interaction with the irregular bathymetry. Analysis of the flow structure in terms of the critical Richardson number, based on previous studies in the Baltic Sea, shows that these mechanisms and similar phenomena evidently occur at strong density interfaces in the Baltic Sea area where internal waves are less regular but still essentially contribute to interfacial mixing.
1. Mann, K. H. and Lazier, J. R. N. Dynamics of Marine Ecosystems: Biological–Physical Interactions of the Oceans. Blackwell, UK, 2006.
2. Thorpe, S. Turbulence in stably stratified fluids: A review of laboratory experiments. Boundary Layer Meteorol., 1973, 5, 95–119.
3. Apel, J. R. An Atlas of Oceanic Internal Solitary Waves: Oceanic Internal Waves and Solitons. Global Ocean Associates, prepared for Office of Naval Research, USA, Code 322PO, 2002.
4. Smyth, W. D. and Winters, K. D. Turbulence and mixing in Holmboe waves. J. Phys. Oceanogr., 2003, 33, 694–711.
5. Burchard, H., Craig, P. D., Gemmrich, J. R., van Haren, H., Mathieu, P.-P., Meier, H. E. M., Smith, W. A. M. N., Prandke, H., Rippeth, T. P., Skyllingstad, E. D., Smyth, W. D., Welsh, D. J. S. and Wijesekera, H. W. Observational and numerical modeling methods for quantifying coastal ocean turbulence and mixing. Progr. Oceanogr., 2008, 76, 399–442.
6. Geyer, W. R. and Farmer, D. M. Tide-induced variation of the dynamics of a salt wedge estuary. J. Phys. Oceanogr., 1989, 19, 1060–1072.
7. Yoshida, S., Ohtani, M., Nishida, S. and Linden, P. F. Mixing processes in a highly stratified river. Physical Processes in Lakes and Oceans: Coastal and Estuarine Studies, 1998, 54, 389–400.
8. Holmboe, J. On the behavior of symmetric waves in stratified shear layers. Geophys. Publ., 1962, 24, 67–113.
9. Caulfield, C. P. and Peltier, W. R. The anatomy of the mixing transition in homogeneous and stratified free shear layers. J. Fluid Mech., 2000, 413, 1–47.
10. Farmer, D. M. and Smith, J. D. Tidal interaction of stratified flow with a sill in Knight Inlet. Deep Sea Res., 1980, 27A, 239–254.
11. Trites, R. W. An oceanographic and biological reconaissance of Kennebecasis Bay and the Saint John River Estuary. J. Fisheries Res. Board Canada, 1959, 17, 377–408.
12. Metcalfe, C. C., Dadswell, M. J., Gillis, G. F. and Thomas, M. L. H. Physical, Chemical and Biological Parameters of the Saint John River Estuary, New Brunswick, Canada. Department of the Environment Fisheries and Marine Service, Canada. Technical Report No 686, 1976.
13. Reissmann, J. H., Burchard, H., Feistel, R., Hagen, E., Lass, H. U., Mohrholz, V., Nausch, G., Umlauf, L. and Wieczorek, G. Vertical mixing in the Baltic Sea and consequences of eutrophication – a review. Progr. Oceanogr., 2009, 82, 47–80.
14. Richardson, L. F. The supply of energy from and to atmospheric eddies. Proc. Roy. Soc. London, 1920, A97(686), 354–373.
15. Miles, J. On the stability of heterogeneous shear flows. J. Fluid Mech., 1961, 10, 496–508.
16. Miles, J. and Howard, L. N. Note on heterogeneous shear flow. J. Fluid Mech., 1964, 20, 331–336.
17. Lawrence, G. A., Browand, F. K. and Redekopp, L. G. The stability of a sheared density interface. Phys. Fluids A, 1991, 3, 2360–2370.
18. Haigh, S. P. Non Symmetric Holmboe waves. Ph.D. thesis. Department of Mathematics, University of British Columbia, Vancouver, BC, Canada, 1995.
19. Hughes Clarke, J. E. and Haigh, S. P. Observations and interpretation of mixing and exchange over a sill at the mouth of the Saint John River Estuary. In Proc. 2nd CSCE Speciality Conference on Coastal Estuary and Offshore Engineering. Toronto, Ontario, Canada, 2005.
20. Delpeche, N. D. Observations of Advection and Turbulent Interfacial Mixing in the Saint John River Estuary. M.Sc.E. thesis, University of New Brunswick, Canada, 2006.
21. Apel, J. R., Ostrovsky, L. A., Stepanyants, Y. A. and Lynch, J. F. Internal Solitons in the Ocean. Technical Report. Woods Hole Oceanographic Institution, Woods Hole, USA, 2006.
22. Armi, L. and Farmer, D. M. The flow of Mediterranean water through the Straits of Gibraltar. Progr. Oceanogr., 1988, 21, 1–105.
23. Farmer, D. M. and Armi, L. The generation and trapping of solitary waves over topography. Science, 1999, 283, 188–190.
24. Stigebrandt, A. A model for the exchange of water and salt between the Baltic and the Skagerrak. J. Phys. Oceanogr., 1983, 13, 411–427.
25. Leppäranta, M. and Myrberg, K. Physical Oceanography of the Baltic Sea. Springer Praxis, Chichester, U. K., 2009.
26. Wulff, F., Rahm, L. and Larsson, P. (eds.). A Systems Analysis of the Baltic Sea. Springer, Berlin, Heidelberg, 2001.
27. Elken, J., Malkki, P., Alenius, P. and Stipa, T. Large halocline variations in the Northern Baltic Proper and associated meso and basin-scale processes. Oceanologia, 2006, 48(S), 91–117.
28. Kuzmina, N., Rudels, B., Stipa, T. and Zhurbas, V. The structure and driving mechanisms of the Baltic intrusions. J. Phys. Oceanogr., 2005, 35, 1120–1137.
29. Gargett, A. E. Vertical eddy diffusivity in the ocean interior. J. Marine Res., 1984, 42, 359–393.
30. Gargett, A. E. and Holloway, G. Dissipation and diffusion by internal wave breaking. J. Marine Res., 1984, 42, 15–27.
31. Meier, H. E. M., Feistel, R., Piechura, J., Arneborg, L., Burchard, H., Fiekas, V., Golenko, N., Kuzmina, N., Mohrholz, V., Nohr, C., Paka, V. T., Sellschopp, J., Stips, A. and Zhurbas, V. Ventilation of the Baltic Sea deep water: A brief review of present knowledge from observations and models. Oceanologia, 2006, 48(S), 133–164.
32. Stigebrandt, A., Lass, H. U., Liljebladh, B., Alenius, P., Piechura, J., Hietala, R. and Beszczynska, A. DIAMIX – an experimental study of diapycnal deepwater mixing in the virtually tideless Baltic Sea. Boreal Envir. Res., 2002, 7, 363–369.
33. Lundhansen, L. C. and Skyum, P. Changes in hydrography and suspended particulate matter during a barotropic forced inflow. Oceanologica Acta, 1992, 15, 339–346.
34. Friedrichs, C. T. and Wright, L. D. Resonant internal waves and their role in transport and accumulation of fine sediment in Eckernförde Bay, Baltic Sea. Cont. Shelf Res., 1995, 15, 1697–1721.
35. Talipova, T. G., Pelinovsky, E. N. and Kõuts, T. Kinematic characteristics of internal wave field in the Gotland deep of the Baltic Sea. Oceanologiya, 1998, 38, 37–46.
36. Vadov, R. A. Long-range sound propagation in the central region of the Baltic Sea. Acoust. Phys., 2001, 47, 150–159.
37. Lilover, M.-J. Vertical Fine Structure of Currents in the Baltic Sea. Ph.D. thesis. Institute of Thermo- and Electrophysics, Tallinn, 1989.
38. Lilover, M.-J. Vertical structure of mesoscale currents in the Baltic Sea. Ann. Geophys., 1992, 10, Suppl. II, C196.
39. Lilover, M.-J. and Otsmann, M. On the vertical run of inertial waves in the Baltic Sea. In Proc. 15th Conference of Baltic Oceanographers. Copenhagen, 1987, 374–387.
40. Lilover, M.-J., Otsmann, M. and Tamsalu, R. Near-inertial waves and shear instability. In Proc. 16th Conference of Baltic Oceanographers. Kiel, 1989, 648–652. 41. Polzin, K. L., Toole, J. M., Ledwell, J. R. and Schmitt, R. W. Spatial variation of turbulent mixing in the abyssal ocean. Science, 1998, 276, 93–96.
doi:10.1126/science.276.5309.93Back to Issue