Water covers 71 percent of Earth’s surface, giving rise to the nickname “the Blue Marble” or “the Blue Planet.” Satellites that observe ocean color, however, show that it’s not that simple. Materials in the water—living or otherwise—are often stirred and mixed until the surface swirls with hints of blue, green, tan, white, and brown.
“The region of Bohai Sea, Yellow Sea, and East China is one of the most turbid and dynamic ocean areas in the world,” said ocean color expert Menghua Wang of the National Oceanic and Atmospheric Administration.
In the image, the brown area along China’s Subei Shoal is turbid water commonly seen in coastal regions. According to Wang, shallow water depths, tidal currents, and strong winter winds likely contributed to the mixing of sediment through the water.
Some of the swirls in the image might be due to the Yellow Sea Warm Current, which intrudes into the Yellow Sea in wintertime. This branch of the Kuroshio Current changes the temperature of the sea surface and brings instability that could be the cause of the relatively dark swirls in the lower-middle part of the image.
Interpreting satellite images of ocean color can be a challenge, especially in complex regions like the Yellow Sea. Upcoming missions such as the Pre-Aerosol, Clouds, and ocean Ecosystem (PACE) should help scientists to better distinguish the particles and materials in the atmosphere and ocean.
NASA images by Norman Kuring, NASA’s Ocean Color web. Caption by Kathryn Hansen.
Submerged in the Atlantic Ocean off the coast of Spain and Portugal are giant, salty whirlpools of warm water. These deep-water whirlpools are part of the ocean’s circulatory system, and they help drive the ocean currents that moderate Earth’s climate. Warm water ordinarily sits at the ocean’s surface, but the warm water flowing out of the Mediterranean Sea is so salty (and therefore dense) that when it enters the Atlantic Ocean at the Strait of Gibraltar, it sinks to depths of more than 1,000 meters (one-half mile) along the continental shelf. This underwater river then separates into clockwise-flowing eddies that may continue to spin westward for more than two years, often coalescing with other eddies to form giant, salty whirlpools that may stretch for hundreds of miles. Because the eddies originate from the Mediterranean Sea, scientists call them “Meddies.”