Observations of internal tides in the Mozambique Channel

Abstract

Internal waves in the Mozambique Channel were studied, in the narrowest passage between Mozambique and Madagascar. Seven current meter moorings were deployed for a year and a half. The observed baroclinic flow in the semidiurnal frequency band exhibited strong intermittency. Internal tides could be detected at nearly all times from differences between current meter records in amplitude and phase, varying in time. To study the long‐term average of the internal tidal field, the overall energy in the semidiurnal bands was computed for each location. Internal tidal currents were everywhere strongest near the surface (around 4 cm/s at 250 m depth up to 12 cm/s near the pycnocline in the generation area), decreased to less than 3 cm/s at 600 m depth, and increased a little near the bottom. The results were compared with numerical results from a two‐dimensional internal‐tide generation model allowing a description of beam scattering at the pycnocline and repeated reflection. Model results and observations were in qualitative agreement.