Sahara Dust

This was originally written four years ago as a Maho Newsletter by Bob Carmody.

SAHARA DUST

A meteorology report from the Pennsylvania State University on July 30 this year stated that satellite pictures were showing a vast plume of dust spreading across the eastern tropical Atlantic. The brown swirls shown in the pictures were dust from the Sahara desert blowing over the Atlantic Ocean toward the Caribbean and the Americas. By the end of August, the dust had passed over the Virgin Islands.

This Sahara dust has a mixed impact: The dust is a boom for life in the ocean and for vegetation on land. It acts as kind of vitamin supplement to nutrient poor soils. It helps give us some of those extraordinary sunsets that you can often see from the Maho pavilion and the marvelous sunrises you can see from Concordia. It also gives some of those rare, overcast gray days; and it also gives us that gritty feeling underfoot particularly on the tile floors in the studios at Harmony and Concordia.

The dust was initially lofted into the atmosphere by currents of hot air rising from the floor of the Sahara Desert. It is common for weather disturbances to carry dust from the Sahara toward the Caribbean and the Americas. Research suggests that dust from Africa makes up at least half the particles in the air in the southeast United States

Giant sand storms — often larger than Spain — routinely blow all the way across the Atlantic, reaching South America, the Caribbean, and the southeastern United States. "There have been times when airports in the Caribbean have been closed down for lack of visibility from these dust storms," said Eugene Shinn, a senior geologist at the U.S. Geological Survey in St. Petersburg, Fla. "It shows we're all linked together in one way or the other, that's for sure." It is a global phenomenon. Windstorms in China have darkened cities in Australia; dust from Mongolia has turned up in Denver. ‘You would be surprised, he said. "It's a complete chemical soup," said Shinn."It's full of living microbes, it has a little mercury in it, small bits of arsenic, you name it, and it’s in there."

Shinn and his colleagues surprised their fellow scientists two years ago, when they published a study showing that bacteria and fungi could survive transoceanic trips in the upper atmosphere. Apparently, they ride on grains of sand, carried by winds to altitudes of 10,000 feet or more where many scientists believed they would be killed off by the ultraviolet rays of the Sun.

Biologists suspect the dust may be responsible for damage to coral reefs off the coast of Florida; the coral has no immunity to diseases that settle in the water, carried from places thousands of miles away. Two Billion Tons a Year But the dust is also an essential part of life on Earth. Two billion tons of it routinely cross the oceans every year, so much that it's become part of nature's routine. "African dust blows over almost on a daily basis during our summer, falling in the Caribbean," says Dale Griffin, a microbiologist at the U.S. Geological Survey. "A good number of the plants in the upper canopy of the Amazon rainforest derive all their nutrients from African dust." As one scientist said, the whole planet is intermixing. If you see a truly spectacular sunset, you may be able to thank a distant desert.

(Thanks to the New York Times and ABC News Internet Ventures from whom we have borrowed heavily)