Register      Login
Marine and Freshwater Research Marine and Freshwater Research Society
Advances in the aquatic sciences
Shopping Cart: ( empty )
You are here: Home > Journals > MF > MF05059 > Fulltext
RESEARCH FORUM
Contents Vol 57(3)

Tidal stirring and mixing on the Australian North West Shelf

K. Katsumata
+ Author Affiliations
- Author Affiliations

A School of Physical, Environmental, and Mathematical Sciences, University of New South Wales, Australian Defence Force Academy, Canberra, ACT 2600, Australia.

B Present address: CSIRO Marine and Atmospheric Research, Hobart, Tas. 7001, Australia.

C Email: katsuro.katsumata@csiro.au

Marine and Freshwater Research 57(3) 243-254 https://doi.org/10.1071/MF05059
Submitted: 31 March 2005  Accepted: 4 January 2006   Published: 1 May 2006

Abstract

Strong tides on the Australian North West Shelf lead to vigorous vertical stirring and mixing. This activity near the shelf break is directly quantified with a numerical model. The model has a spatial and temporal resolution of about 800 m and 13 s respectively. The model result shows internal tides steepening as they shoal onto the slope, which is near critical for the semidiurnal tide. The main energy balance of the internal tides is between incoming internal tidal energy flux and the dissipation. The vertical and horizontal distribution of the heat flux carried by the internal tides is complex and difficult to parameterise. When area-averaged in the model region (38 km by 36 km), the vertical heat flux is in the order of –10−5 deg m s−1 (positive upward). This translates to a vertical diffusivity of 10−4 to 10−2 m2 s−1, which is an order of magnitude larger than the subgrid vertical diffusion. Both the warming and cooling rates caused by the convergence and divergence of the heat flux are in the order of 10−6 deg s−1. The neap-spring modulation of the semidiurnal tide did not significantly modify these estimates. These values can explain the vertical heat exchange inferred from large-scale analysis of the heat budget on the Shelf.

Extra keywords: internal tide, numerical model.


Acknowledgment

This work is supported by an ARC Discovery grant awarded initially to the late Dr Peter Holloway. The idea to run a nested POM is also attributed to him. The author gratefully acknowledges his support in different ways throughout the project. Computing has been made possible through a grant from the Australian Partnership for Advanced Computing National Facility.


References

Blumberg A. F., and Mellor G. L. (1987). A description of a three-dimensional coastal ocean circulation model. In ‘Three-Dimensional Coastal Ocean Models’. (Ed. N. S. Heaps.) pp. 1–16. (American Geophysical Union: Washington, DC.)

Brenner, S. (2003). High-resolution nested model simulations of the climatological circulation in the Southeastern Mediterranean Sea. Annales Geophysicae 21, 267–280.
Holloway P. E. (1991). On the dissipation of internal tides. In ‘Tidal Hydrodynamics’. (Ed. B. B. Parker.) pp. 449–468. (John Wiley and Sons: New York.)

Holloway, P. E. (2001). A regional model of the semidiurnal internal tide on the Australian North West Shelf. Journal of Geophysical Research 106, 19 625–19 638.
| Crossref | GoogleScholarGoogle Scholar | Levitus S. (1982). ‘Climatological Atlas of the World Ocean.’ (NOAA/ERL GFDL Professional Paper 13: Princeton, NJ.)

Lien, R.-C. , and Sanford, T. B. (2004). Turbulence spectra and local similarity scaling in a strongly stratified oceanic bottom boundary layer. Continental Shelf Research 24, 375–392.
| Crossref | GoogleScholarGoogle Scholar |

Mellor, G. L. , and Yamada, T. (1982). Development of a turbulent closure model for geophysical fluid problems. Review of Geophysics and Space Physics 20, 861–875.


Osborn, T. R. (1980). Estimates of the local rate of vertical diffusion from dissipation measurements. Journal of Physical Oceanography 10, 83–89.
| Crossref | GoogleScholarGoogle Scholar |

Oey, L.-Y. , and Chen, P. (1992). A nested-grid ocean model: with application to the simulation of meander and eddies in the Norwegian Coast Current. Journal of Geophysical Research 97, 20 063–20 086.


Rochford, D. J. (1991). ‘Upwelling’: does it need a stricter definition? Australian Journal of Marine and Freshwater Research 42, 45–46.
| Crossref | GoogleScholarGoogle Scholar |

Sandstrom, H. , and Elliott, J. A. (1984). Internal tide and solitons on the Scotian Shelf: a nutrient pump at work. Journal of Geophysical Research 89, 6415–6426.


Slinn, D. N. , and Riley, J. J. (1996). Turbulent mixing in the oceanic boundary layer caused by internal wave reflection from sloping terrain. Dynamics of Atmospheres and Oceans 24, 51–62.
| Crossref | GoogleScholarGoogle Scholar |

Smith, W. H. F. , and Wessel, P. (1990). Gridding with continuous curvature splines in tension. Geophysics 55, 293–305.
| Crossref | GoogleScholarGoogle Scholar |

Smyth, N. F. , and Holloway, P. E. (1988). Hydraulic jump and undular bore formation a shelf break. Journal of Physical Oceanography 18, 947–962.
| Crossref | GoogleScholarGoogle Scholar |

Winters, K. B. , and D’Asaro, E. A. (1996). Diascalar flux and the rate of fluid mixing. Journal of Fluid Mechanics 317, 179–193.


Winters, K. B. , Lombard, P. N. , Riley, J. J. , and D’Asaro, E. A. (1995). Available potential energy and mixing in density-stratified fluids. Journal of Fluid Mechanics 289, 115–128.


Wolanski, E. (1993). Water circulation in the Gulf of Carpentaria. Journal of Marine Systems 4, 401–420.
| Crossref | GoogleScholarGoogle Scholar |

Wunsch, C. (1968). On the propagation of internal waves up a slope. Deep-Sea Research 15, 251–258.