Perturbations on the surface of the Sea of Japan can be seen in this photograph due to the reflection of the Sun off the water. This phenomenon is called sunglint. Two types of disturbances of the sea surface are seen in the sunglint. First, a large spiral eddy dominates the upper right portion of this scene off the coast of Honshu, Japan. This feature attests to the dynamic nature of the ocean system.
Second, the V-shaped features in the center of the scene are ship wakes that record the ship traffic in this area. Among these ship wakes, the wider V’s indicate slower-moving ships, such as tankers or freighters, while acute-angled V’s indicate faster moving ships, such as naval vessels. Shipment of goods with a high cost-to-weight ratio, such as oil and wheat, typically occurs via tankers and freighters. Transport of goods by sea is generally less expensive than by land, and much less expensive than by air.
Sunglint highlights many of the surface features in this oceanic scene. The only land visible in this scene is the dark fingerlike protrusion on the left side. The other dark spots are located on the surface of the water in areas where either the sea surface is relatively undisturbed by currents or winds or where the angle of the Sun is too high to distinguish features.
June 1991, image STS-40-72-98.