Short-period vertical displacements of the upper layers in the Strait of Gibraltar: part 1 - text: part 2 - diagrams

Abstract

The report is principally based on observations of short-term displacements made by the author in the summers of 1958, 1959, and 1961, using a thermistor chain. Pilot tubes installed on the thermistor chain made simultaneous current measurements, which indicated particle velocities that suggest that the short-term vertical displacements may be interpreted as internal waves. The record revealed independent trains of internal waves superimposed on each of the semidiurnal waves of the tidal period. The internal waves generally formed over the submarine sill that lies west of Tarifa and moved eastwards into the Mediterranean at speeds that increased up to 5 kn by the time they had travelled 16 miles. They were found to have vanished completely within a distance of 50 miles. Above the crests of these leading waves, long bands of ripples were seen to form at the surface and, in favourable wind conditions, to form breakers visible on a radar screen.