SAR observations of internal solitary waves generated at the Estremadura Promontory off the west Iberian coast

A comprehensive dataset of Synthetic Aperture Radar (SAR) images from the west Iberian coast is used to identify the Estremadura Promontory as an oceanic hotspot for internal solitary waves. The full two-dimensional structure and the main physical properties of these waves are revealed for the first time. Composite maps and a statistical analysis show that these waves have two main propagation paths coming from the northern and southern slopes of the promontory, and that on average they have horizontal scales of the order of 400 m and crestlengths around 9 km. The overall propagation of the internal solitary wave field observed in the SAR images is evaluated, using a proxy measure for energy based on observed wavelengths, crestlengths and radar backscatter intensities. A refraction pattern is found to divert the meridionally propagating waves to the east, where they eventually dissipate in the inner-shelf regions close to shore. The barotropic body force is calculated and the most likely generation locations are identified. It is found that there is more energy emanating from the south while the tidal forcing seems to be equally divided between both flanks of the promontory. Calculations using the vertical excursion inverse Froude number (defined by Legg and Klymak, 2008) indicate that this is probably related to the steeper slopes located in the northern side. This pronounced bathymetry is more likely to generate internal hydraulic jumps and overturning, which may inhibit the disintegration of the internal tide into solitary waves.

► Estremadura Promontory is a major hotspot for oceanic internal solitary waves.
► Two-dimensional structure and main properties revealed.
► Waves generated with meridional propagation direction refract towards the coast.
► Main generation locations studied using Baines (1982) body force.