Changing currents

Image of the month - September 2001

Speed of currents due to the semi-diurnal lunar tides M2 close to the Faroes and Shetland islands (North of Scotland). (Credits CLS/Legos).

The tide move water masses, which causes currents. These currents, sometimes violent in straits, are particular in that they change in intensity and direction according to the tides. It is vital for coastal navigation, for preventing pollution and protecting the shoreline, that we understand them and are able to predict them. Project of undersea turbine -like an immersed windmill- to generate electricity from these currents are currently under study.

Altimetry enables tide forecasting to within 2 to 3 centimetres in the middle of the ocean. This helps to constrain local tide models, and to forecast tidal currents near the coasts, where they are the strongest and the most changing -and where their knowledge is the most critical.

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