On July 3, 2014 NASA’s Aqua satellite passed over Crete and the Aegean Islands, allowing the Moderate Resolution Imaging Spectroradiometer (MODIS) to capture an unusual true-color image of the scene. Like all true-color images, vegetated land appears green, sparsely vegetated soils appear greenish-tan, arid desert is seen as light tan, and the basic color of water is blue. What is unusual about this image, however, is the presence of milky silver tones – a result of reflected light.
The silvery colors are the result of “sunglint” – sunlight reflected from the ocean surface directly back at the satellite imager. If the ocean water were perfectly smooth, like a mirror, the reflection of the sun could be viewed very brightly. The surface of even the most peaceful oceans is textured by small waves, so the light is not perfectly reflected. Where the surface is the smoothest, it appears the brightest; rougher water reflects less light and is dark.
The movement of water around islands causes turbulent flow as it passes the obstruction and can roil the surface of the ocean. Winds moving over obstructions also create turbulence on the lee side, and where a breeze blows against water the surface also becomes roughened. In sunglint areas, the play of moving wind and water changes the surface reflectivity, much like streaks on a mirror. The view that results can reveal much about the surface of the ocean that is not normally visible.