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A massive dust cloud that had been journeying 5,000 miles from the Sahara Desert across the Atlantic Ocean since June 15, 2020, finally hit the United States mainland on June 26, 2020. Nicknamed "Godzilla," the 3,500 mile-long plume broke into two chunks, thanks to the split in the mid-levels of the atmosphere.
One part drifted northwards towards the Plains States and the Midwest before moving up to the Canadian border on Monday, June 29, 2020. While cities like Minneapolis and Chicago witnessed hazier than usual skies over the past weekend, the dust had diffused and thinned out substantially by the time it reached the areas. However, the second batch of dust, which lingered over Texas, the Carolinas, and Florida for a couple of days, was thick enough to pose health risks to residents, causing authorities to recommend they stay indoors, if possible. Fortunately, the dust has since moved towards the tropical Eastern Pacific Ocean, where it will eventually dump its swirling mass of particles.
The "Saharan Air Layer" is not an entirely unknown phenomenon. Each year, windstorms pick up182 million tons of sand — enough to fill 689,290 semi-trucks — from the Sahara Desert. The sand cloud's ultimate destination depends on the time of the year. In the winter and spring, the winds usually direct the dust plumes to land directly in the Amazon rainforest in South America. In the summer, it sends them towards North America.
However, the dust layer, which begins about one mile into the atmosphere and extends upward for about two miles, typically disperses by the time it reaches the US coast, leaving little visible impact. But this year the cloud was unusually large both in volume and density. "In terms of concentration and density and size, it is the most dust we've seen in 50 or 60 years," Pablo Méndez Lázaro, an environmental health researcher at the University of Puerto Rico, told The Atlantic.
Though the massive amounts of sand can result in respiratory issues, especially among those that suffer from allergies, it does have some benefits. For one, it results in spectacular sunrises and sunsets. "Typically, you lose the blue sky for more hazy, milky sky," Dr. J Marshall Shepherd, director of the Atmospheric Sciences Program at the University of Georgia, told NPR. "You tend to see more vivid sunsets and sunrises because of the scattering properties of the dust interacting with the sunlight." The dry, dusty storms also help prevent massive hurricanes from forming over the Atlantic Ocean, by soaking up the moist, storm-friendly air.
And that is not all. The large amounts of minerals and nutrients in the sand help fuel the local ecosystems in which it lands. The Saharan dust storms are believed to be an essential source of phosphorus for plants in the Amazon rainforest, particularly those growing high up in the Amazon canopy. Some researchers believe the dust storms are also responsible for the beautiful coral reef that encrusts the Bahamas. They assert that the waters around the islands lack the nutrients to create such an oasis.
What is unclear, however, is the effect the current dust plume will have on Pacific Ocean ecosystems, given that they are typically untouched by the yearly sand migration. A 2001 study by the University of South Florida suggests that the deluge of nutrients, particularly iron, could result in a proliferation of algal blooms that cover the water's surface and deplete large areas of oxygen, causing harm to marine animals. Hopefully, that will not be the case!
Resources: TheAtlantic.com,NPR.org, ScientificAmerican.com,CBSnews.com