Home > Publications > Le point sur les marées d’équinoxes dans l’estuaire du Saint-Laurent

Daniel Bourgault, Cédric Chavanne, Dany Dumont, Émilie Morin, Peter S. Galbraith et Louis Gostiaux

Le point sur les marées d’équinoxes dans l’estuaire du Saint-Laurent

Le naturaliste canadien, 140 (1) 2016

According to a study published in Le Naturaliste canadien, tides in the St. Lawrence Estuary would not be any greater at the equinoxes than they are at any other moment of the year. According to the study, the idea that tides may be larger at the equinoxes is a popular unfounded belief that is widespread, even among scientists. Here, it is emonstrated that these conclusions contradict the theory of tides and arise from a problem in the subsampling of tide data.

A statistical analysis based on 30 years of hourly water level observations at Rimouski, shows that tides are indeed more energetic around the equinoxes, which is in agreement with the theory of tides. However, this conclusion does not necessarily indicate that the greatest tides always appear precisely at the equinoxes in a given year. This is because the increase in the tidal range as the equinoxes are approached is rather small in comparison with the large neap-spring tidal variability, which is not synchronized with the equinoxes. The theory of tides is explained in simple terms and a schematic diagram is proposed to explain the effect on tides during the equinox-solstice cycle.

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