The tides of the Atlantic Ocean, 60° N to 30° S

Abstract

This paper is a sequel to Cartwright, Edden, Spencer & Vassie (1980) (henceforth C.E.S.V.), which concentrated on the tides of a small portion of the North Atlantic between the MidAtlantic Ridge and the west European shelf. In both works we have aimed to discover what can be learnt of the spatial dynamic properties of the ocean tides from direct measurements in the open sea, with a minimum of prejudice from the artefacts of computer models. An essential background has been a development over roughly 15 years (1970—1985) of the instrumental technique of recording pressure variations on the ocean floor for long periods, together with their associated acoustic recall systems and calibrating devices. This instrumental development has been led principally by one of the authors (R. S.) with the help of colleagues at the Bidston and Wormley laboratories of the Institute of Oceanographic Sciences (IOS). The sea-going activity described in C.E.S.V. had seemed adventurous, because tidal variations offshore had not been measured before in that part of the Atlantic Ocean, but when compared with computer-generated tidal maps of the world ocean the distances reached appear small on the scale of the principal wavelengths. Similar measurements in the Atlantic by other authorities were concentrated in a narrow band within a few hundred kilometres of the east coasts of Canada and the U.S.A. (Cartwrightet al. 1979). With the sanction of the IOS we decided to bridge the gap between east and west Atlantic by a few supplementary lines of pressure recordings between the existing sets. Some pressure records from the equatorial zone taken later as part of a climate research programme (Cartwright al. 1987) extended the network further to the south. We shall be concerned here with the analysis of these new data sets and with the interpretation of the whole available set of tidal constants from the Atlantic Ocean including islands and coasts.