Drift of the node of the semidiurnal tide in Northumberland Strait

Abstract

Long series of observations on the water level inside Northumberland Strait reveal that the M 2 tide varies between the winter and the summer months. This implies that the semidiurnal node, which is assumed to exist in the northern extremity of the strait, is displaced over the seasons. Sets of additional observations in the immediate vicinity of the node contain such a weakened and irregular semidiurnal signal that there is no possibility of resolving from them the components that make up the semidiurnal band. When handling and interpreting the field data, it is preferable to conceive of a zone of minimum semidiurnal activity in the northern extremity of the strait, which is displaced by ice and storms, by cycles of neap and spring tides in the Gulf of Saint Lawrence and by short lived weather events rather than assume the existence of a fixed point of no vertical motion.