Gulf of Tonkin

The Gulf of Tonkin is a semi-enclosed basin with Hainan Island (China) located to the southeast. Although the gulf is relatively shallow with a depth of less than 100 m (330 ft), it features complex bottom topography. The gulf is strongly influenced by the Red River delta system in the west (Vietnam) and intense summer monsoons. The eastern gulf is characterized by counterclockwise circulation and tides are a major factor driving changes in the speed, direction, and intensity of surface currents. Green colors in the ocean indicate high productivity, fueled by nutrients that are stirred by the ocean’s motion or delivered from rivers. This image was taken by the OCI sensor aboard the PACE spacecraft on January 12, 2026.

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