Signatures of underwater bottom topography in the Straits of Malacca in images from the SPOT satellites

Abstract

On visible/near-infrared images of the Straits of Malacca, taken by the SPOT satellites, signatures of the underwater bottom topography can be seen. These signatures consist of bright lines and patches which occur roughly at the location of underwater ridges (water depth less than 20 m). We show that the signatures are caused by a surface phenomenon: namely, the modulation of the strong tidal current in the Straits of Malacca by the bottom topography in turn modulates the sea surface roughness. This affects the sun glitter radiance of the sea surface and thus can become visible in the image, provided the imaging geometry is suitable. This is substantiated by simulation calculations. This study shows that qualitative information about the position of shoals can be derived from SPOT images.