Climate Number: 1.52 Teragrams
While Lake Chad today covers an area of around 115-200 square miles, at the end of the last ice age (12,000 years ago), there was Lake Megachad, which covered an area as large as 154,000 square miles. Rivers flowing into the lake brought in sediments from the surrounding landscape, and the bodies of plankton growing on the lake surface became deposits on the lake bed as they died and sank to the bottom. The lake bed became a nutrient rich sedimentary layer full of minerals such as iron and phosphorous. The lake has shrunk as the climate has changed over the past 10,000 years, and this rich deposit is now dry, easily erodible and exposed to the surface winds that carry it away during dust storms. One particularly rich deposit from Lake Megachad is known as the Bodélé Basin, which is Earth’s largest single source of atmospheric dust. During the winter months, the Bodélé Low Level Jet carries dust plumes from this basin westward across the Sahara and even across the Atlantic Ocean to the Amazon rainforest. This dust is a fertilizer for the rainforest, and helps to sustain the rich ecosystems there that play considerable roles in the global nitrogen and carbon cycles. One key nutrient transported out of the Bodélé Basin is iron. Each year, up to 1.52 teragrams (1.52 trillion grams) of iron travel from the Bodélé Basin across the Atlantic and into the Amazon rainforest. The total amount of dust transported from the Bodélé Basin to the Amazon may be as high as 277 teragrams annually.
For Comparison: 1.52 teragrams is about the same weight as 125,000 Boeing 757-200′s.
Seasons: Winter, Spring, Summer, Fall
Source: Bristow, CS et al. “Fertilizing the Amazon and equatorial Atlantic with West African dust.” Geophysical Research Letters 37 (2010): L14807.
