File:English Channel (MODIS 2019-02-27).jpg

English: The waters of the English Channel were colored by streaks and swirls of tans and green in late February 2019. The Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Aqua satellite acquired a true-color image of the scene on February 25.

The English Channel connects the waters of the Atlantic Ocean in the south and the North Sea, and also separates England (west) from France (east). At the Strait of Dover—the narrowest point of the Channel—the waters separate the two country by just 33.3 km (20.7 mi). This narrow strait has been cited by Guinness World Records as the “world’s busiest shipping lane”, with 500-600 ships passing through the narrow passage on a daily basis.

The discoloration of the water appears to be primarily caused by sediment flowing from many of the major rivers or the region, including the Thames, which flows by London, England before reaching the English Channel. Another plume along the English coast comes from Southampton Water a tidal estuary north of the Solent and Isle of Wight. Along the coast of France, tan sediment pours from the Sée and Sélune Rivers at the bay of Mont Saint Michael. Further north another tan plume pours from the River Seine.

When sediment pours into a body of water, it typically stays near the surface for a time before it begins to sink. When it is near the surface, sediment usually appears tan. The light reflectance of sediment changes as it begins to sink and the appearance changes from tan to green. While most of the colors in the English Channel come from suspended sediment, some of the green color may also be due phytoplankton—microscopic plant-like organisms that live in small numbers year-round in the waters of the North Sea and English Channel. When conditions are right, phytoplankton can reproduce explosively, creating large blooms that can be seen from space.