Tons of Sahara Desert dust crosses the Atlantic to fertilize the Amazon...

Tons of Sahara Desert dust crosses the Atlantic to fertilize the Amazon rainforest



New data from a NASA satellite reveals just how much the world’s largest rainforest relies on the world’s largest desert.

Every year, nearly 28 million tons of dust is swept from the Sahara Desert across the Atlantic Ocean to settle in South America, where it helps fertilize the Amazon rainforest, a NASA study found.

While scientists have known about the trans-Atlantic phenomenon for years, the researchers were able to estimate for the first time the amount of dust that makes the 3,000-mile journey. Using data from NASA’s CALIPSO satellite, researchers were able to track these massive plumes of dust in three dimensions.

The dust provides thousands of tons of much-needed phosphorus to the Amazon rainforest, where frequent rainfall and flooding wash away the essential nutrient. Much of this phosphorus comes from rock minerals made up of dead microorganisms that are picked up by wind from a long dry lake bed in Chad.

Scientists found that a total of 182 million tons of dust is lifted by winds past the western edge of the Sahara. Of that amount, an average of 27.7 million tons come to rest on the other side of the Atlantic. For perspective, the amount of dust that reaches South America is enough to fill 104,908 semi trucks, according to a NASA press release.

The amount of dust transported varied wildly from year to year, with an 86% difference between the highest and lowest years. The study said the fluctuation may depend on the amount of rainfall in the Sahel, a small strip of semi-arid land south of the Sahara. Rainfall fluctuations there have been linked to boom and bust cycles in Atlantic hurricane activity, too, since rainstorms drifting off the west coast of Africa often go on to form tropical cyclones.

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Each particle of dust is no bigger than a tenth of the width of a human hair. But in aggregate, they form large plumes that can be seen from space. The study is part of a larger effort to understand the effects of dust and small particles known as aerosols on local and global climate.

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