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Re: Global oceanic tides, was: Navigating Around Hills and Dips in the Ocean
From: Trevor Kenchington
Date: 2003 Aug 16, 22:16 -0300
From: Trevor Kenchington
Date: 2003 Aug 16, 22:16 -0300
Fred Hebard wrote: > Trevor, > > Tidal levels may be calculated, but have satisfactory descriptions of > currents been acheived? I believe George Huxtable was including both > in his description. Good point, Fred. I don't know whether anyone has attempted to model tidal streams in the ocean. (They are usually tiny: The tidal heights are not great, while the volume of water needed to make the difference between high water and low can often move as a current 4,000 metres deep. That means that the rate of drift is very small.) Where coastal tidal streams are concerned: Yes, they have been satisfactorily modelled, in some cases. I'm a tidal enthusiast, not a tidal expert, and I don't pretend to be up to date with the scientific literature. However, I'll offer the example of the Canadian Hydrographic Service's tidal atlases. Those are based entirely on the output from computer models (at least the Bay of Fundy/Gulf of Maine atlas and the Strait of Georgia atlas both are -- I think the St.Lawrence River one is too but I am not fully certain). [CHS publishes only the three tidal atlases.] Then again, I am not sure to what extent those models use empirical observations of the tide as input data (rather than just seabed morphology and astronomic tide-generating forces) so it might be argued that they do not truly represent observed tidal streams by calculating from theory alone. Trevor Kenchington -- Trevor J. Kenchington PhD Gadus@iStar.ca Gadus Associates, Office(902) 889-9250 R.R.#1, Musquodoboit Harbour, Fax (902) 889-9251 Nova Scotia B0J 2L0, CANADA Home (902) 889-3555 Science Serving the Fisheries http://home.istar.ca/~gadus