Dust from the Sahara and Sahel region of North Africa frequently blows west in giant dust storms that stretch across the entire Atlantic Ocean.
Just this past week (24 June 2014) NASA released the latest stunning space photo of just such a dust event.
Every year huge quantities of dust are carried by winds from Africa, across the Atlantic. No other ocean region is so extensively and persistently influenced by such high concentrations of dust. The dusted region extends over 7000 km from the coast of Africa to South America and Caribbean.
This African dust accounts for over half of all global dust in the wind. It is generally recognized that on a global scale mineral dust can affect many aspects of climate, marine productivity, soil fertility, and air quality.
This African dust provides vital mineral micro-nutrients, including iron, to both the Atlantic Ocean and the Amazon rain-forest of South America. 770-1600 million tons of dust is carried by the wind every year from Africa.
While some of this dust falls back to Earth before it leaves Africa, much of it streams out over the Atlantic Ocean where most of it falls into the sea, some is carried on the wind as far away as South America and the Southeastern United States. Dust in the wind provides 90% of the oceans vital iron, the remaining 10% coming from rivers and ocean upwellings according to a paper just published in Nature July 2014.
In recent decades the amount of dust blowing in the Earth’s winds has decreased dramatically as high and rising CO2 produces a global greening effect. As the land becomes greener, that greenery acts as good ground cover protecting soils from blowing away in the wind. The loss of this dust and its minerals is resulting in a loss of green in the oceans.
Dust scientist Dr. Amato Evan published a study in Science magazine March 2009 showing that 69% of the increase in Atlantic sea surface temperatures over the past 26 years could be attributed to decreases in the amount of dust in the atmosphere. While this increased heats in the Atlantic is likely fueling hurricanes of even greater concern is the dramatic drop in net primary productivity in oceans which depend on minerals from that dust to sustain vibrant ocean pastures. Less dust means less plankton.
Below is an animated movie of the movement of a similar African dust storm in 2013.
Here’s a couple of links for further reading.
Dust and Rain – Yin and Yang Of Pastures On Land And At Sea.
Atlantic dust forecast from the Tel-Aviv University Weather Research Center
The Saharan Air Layer (SAL) was first described in 1972, in this classic paper: Carlson, T. N., and J. M. Prospero (1972), The Large-Scale Movement of Saharan Air Outbreaks over the Northern Equatorial Atlantic, Journal of Applied Meteorology, 11(2), 283-297