Saharan dust sustains Amazon forest
IT HAS been known for some time now that the health of the Amazon rain forest in Brazil depends on minerals that have their origin across the Atlantic in the African Sahara desert.
The minerals are washed off by Saharan rain and are carried across the Atlantic by Saharan desert dust.
Major supply
Researchers from the Weizmann Institute of Science, New York, have now discovered that a major percentage of the minerals supplied to the Amazon rain forest come from dust blown across the Atlantic from one particular valley in Northern Chad — the Bodele valley.
In a study published recently in Environmental Research Letters, Dr. Ilan Koren of the Weizmann Institute of Science's Environmental Sciences and Energy Research Department and fellow scientists have explained how the Bodélé valley's unique features might be responsible for making it such a major dust provider.
Important dust source
Resarchers suggest that the Bodélé valley is such an important source of dust due to its shape and geographic features: it is flanked on both sides by enormous basalt mountain ridges, which create a cone-shaped crater with a narrow opening in the northeast. , according to a Weizmann Institute of Science press release.
Winds that `drain' into the valley focus on this funnel-like opening similarly to the way light is focused by an optical lens, creating a large wind tunnel of sorts.
Life sustaining
As a result, gusts of surface wind that are accelerated and focused in the tunnel lift the dust from the ground and blow it toward the ocean, allowing the valley to export the vast amount of dust that makes a life-sustaining contribution to the Amazon rainforest.
By combining various types of satellite data, Dr. Koren and colleagues have now for the first time managed to obtain quantitative information about the weight of this dust.
Analytical approach
Analyses of dust quantities were performed near the Bodélé valley itself, on the shore of the Atlantic and at an additional spot above the ocean.
According to the data some 56 per cent of the dust reaching the Amazon forest originates in the Bodélé valley.
About 50 million tonnes of dust make their way from Africa to the Amazon region every year, a much higher figure than the previous estimates of 13 million tonnes.
The new estimate matches the calculations on the quantity of dust needed to supply the vital minerals for the continued existence of the Amazon rainforest. — Our Bureau
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