A three-dimensional finite-element model of wind effects upon higher harmonics of the internal tide
- 59 Downloads
A non-linear three-dimensional unstructured grid model of the M2 tide in the shelf edge area off the west coast of Scotland is used to examine the spatial distribution of the M2 internal tide and its higher harmonics in the region. In addition, the spatial variability of the tidally induced turbulent kinetic energy and associated mixing in the area are considered. Initial calculations involve only tidal forcing, although subsequent calculations are performed with up-welling and down-welling favourable winds to examine how these influence the tidal distribution (particularly the higher harmonics) and mixing in the region. Both short- and long-duration winds are used in these calculations. Tidal calculations show that there is significant small-scale spatial variability particularly in the higher harmonics of the internal tide in the region. In addition, turbulence energy and mixing exhibit appreciable spatial variability in regions of rapidly changing topography, with increased mixing occurring above seamounts. Wind effects significantly change the distribution of the M2 internal tide and its higher harmonics, with appreciable differences found between up- and down-welling winds and long- and short-duration winds because of differences in mixing and the presence of wind-induced flows. The implications for model validation, particularly in terms of energy transfer to higher harmonics, and mixing are briefly discussed.
KeywordsFinite-element model Wind effects Internal tide
The authors are indebted to Mrs. L. Parry for typing the paper and Mr. R.A. Smith for help in figure production. Access to bottom topography and open boundary forcing were provided by Dr. J. Xing and are gratefully acknowledged. Access to the QUODDY code via the website is much appreciated.
- Blumberg AF, Mellor GL (1987) A description of a three-dimensional coastal ocean circulation model. In: Heaps NS (ed) Three-dimensional coastal ocean models. American Geophysical Union, Washington, DC, pp 1–16 Coastal and Estuarine Sciences, No. 4Google Scholar
- Davies AM, Kwong SCM (2000) Tidal energy fluxes and dissipation on the European continental shelf. J Geophys Res 105:21,969–21,989Google Scholar
- Flather RA (1976) A tidal model of the north west European continental shelf. Mem Soc R Sci Liege 10:141–164Google Scholar
- Jones JE, Davies AM (2006b) On the sensitivity of computed higher tidal harmonics to mesh size in a finite element model (submitted)Google Scholar
- Vlasenko V, Stashchuk N, Hutter K (2005) Baroclinic tides: theoretical modeling and observational evidence. Cambridge University Press, CambridgeGoogle Scholar
- Werner FE (1995) A field test case for tidally forced flows: a review of the tidal flow forum. In: Lynch DR, Davies AM (eds) Quantitative skill assessment for coastal ocean models. American Geophysical Union, Washington, DC, pp 269–284Google Scholar