In winter, winds known as the Harmatten blow west over the Sahara Desert. In the process the winds pick up sand and dust from the Sahara and blow it over the Atlantic. This year, at the end of January, NASA’s satellites picked up images of the Saharan sand over the ocean and over the Cape Verde islands.
The mountainous islands, such as Santiago, São Nicolau and Santo Antão block some of the sand. As a result there is less dust on the west side of the archipelago. The sand blows across the Atlantic to the Caribbean and the Gulf of Mexico. The sand fertilises the sea with nutrients, which can promote the growth of plankton, but can also bring about damage to coral reefs, because of micro-organisms it contains.