Observations of the suppression of tide-generated nonlinear internal wave packets in the Strait of Gibraltar

An examination of October 1983 instrumented moorings data from the western Alboran Sea indicates that nonlinear internal wave packets that normally emanate from the Strait of Gibraltar into the Alboran Sea, were absent during a period when tide conditions should have generated such waves. Other long-term mooring data of the region shows that on occasion, non tide-related absences or reductions in strength of the wave packets has occurred. Available data for wind, atmospheric pressure, surface and deep flow for the period were examined to derive possible causes for the absence of the internal waves. A hypothesis is presented that suggests an increase in the outflow of Mediterranean Water over the main bathymetric sill east of the Strait of Gibraltar may have been the cause. Such an increase may have hindered or strongly limited the generation of internal waves at and near high tide. (C) 1999 Elsevier Science B.V. All rights reserved.