Saturday, September 21, 2019

Winds Across the Ocean: Sahara Dust

Stepping Stones


Photo by Bob McConville |
Dust from the Sahara Desert travels 5,000 miles across the Atlantic to create some magnificent Marco Island sunsets.

We hear about some incredible journeys that take place around our planet annually. The migration of the Wildebeest in Africa is second to none regarding land animals. In the water, millions of sardines make an amazing journey, attracting tens of thousands of marine and aviary predators each year. Right there with the above mentioned is another unbelievable traveler that arrives in the southern United States this time of year, dust.

What!?!? You may ask yourself, “What is so special about dust and why should I even care?” Well, you know those extraordinary sunsets that we might see during the summer months? They are the result of dust in our sky that makes its way here all the way from Africa.

The trade winds have redirected for the summer, blowing from east to west. As a result, the sands from the Sahara Desert are whipped up into the middle atmosphere and carried all the way across the Atlantic Ocean. The sands will make it into the Gulf Stream winds that will reach Florida, and sometimes Texas, Alabama, Louisiana, and Georgia. What an amazing journey!

During the day you may notice what appears to be a halo or ring around the sun. This is a result of the dust particles in the air which causes the halo effect. In the evening, as the sun sets, those magnificent golden colors along the skyline are also a creation of the dust. Thank you, Mother Nature, for this fabulous pallet of colors!

There’s another nice fact about these particles. As long as they are in the atmosphere, making their way across the vast Atlantic, we are assured that moisture is not present in any significant amount to stem any tropical storms or hurricanes. Conclusions can be drawn that the more we see this Sahara dust in the air, the less apt we are to have severe storms.

A few caveats should be noted here as well. Extreme concentrations of this dust could result in respiratory issues. It’s important to know your body and its tolerance for high dust levels in your area. There is no sense in risking your health.

Second, this dust contains a high volume of iron. The Sahara Desert developed between two and seven million years ago when two supercontinents were divided by what was known then as the Tethys Sea. As recently as six thousand years ago there was a dramatic climate shift and a land with lakes, grass plains, giraffes, and hippos was quickly transformed into the region we recognize today. The dust produced at that time was about twenty percent of today’s level, and the Sahara is expected to re-evolve into grassland in about fifteen thousand years. For now, the iron rich dust produced by the sand travels to our region but consequences can be expected.

In 2018 there was a strong outbreak of Red Tide from north Naples to Tampa Bay. There is evidence to suggest that the dust carried here from Africa helped to sustain the longevity of this outbreak. The Red Tide algal blooms have plagued coastal communities for hundreds of years and the Saharan dust could be food for the ominous Red Tide.

As this foreign dust settles on our Gulf waters it fertilizes the surface with iron. Some studies indicate that plant-like bacteria use this iron to set the stage for red tides. When iron levels rise, the bacteria, called Trichodesmium, convert the nitrogen in the water to a form that can be absorbed by other marine life.

And so, the first ingredients for a chemical cocktail are now in place. Iron concentrations could increase by three hundred percent when this dust drops on the water, causing Trichodesmium to increase by ten times its normal state. Mix in other enzymes available in the environment and the result could be a toxic bloom similar to one that spread 8,100 miles in 2018 from Collier County to Tampa Bay.

Good vs Evil: The evidence and presence of the Saharan dust assure us that no huge storms are brewing in the Atlantic, and we are given some of the most fantastic sunsets imaginable. On the other hand, let’s hope, when the dust settles, that conditions are not right for another toxic bloom!

Bob is a naturalist, studying the habits and movement of area dolphins on board the Dolphin Explorer. He is the author of two books and a speaker at many area venues. Bob loves his wife very much!

One response to “Winds Across the Ocean: Sahara Dust”

  1. WOW….how very interesting this article is. I didn’t know all this. Thanks for the education and your research with the dolphins. I imagine you are away from your wife a lot with your travels.

    M.V.

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