20 Jan. () –
Dust signatures from southern Africa -more specifically, from the coast of Namibia- have been found in the Atlantic sector of the Southern Ocean and on the periphery of the eastern Antarctic plateau.
Until recently, it was believed that southern South America was the main source of the dust landing in Antarctica. Fine particles, or aerosols, are often transported long distances by atmospheric circulation.
This dust comes mainly from desert areas where the soil is eroded by the wind. Its origin gives us information about the atmospheric composition, climatic changes and the direction of the wind.
However, a recent study published in Communications Earth & Environment reports dust in Antarctica that came from Africa thousands of years ago.
Geomorphologist James King, a professor in the department of geography at the University of Montreal, was part of the research team that traced the journey of these particles from their region of origin to their final destination.
“This discovery helps us understand wind currents at different climatic periods,” says King it’s a statement. “Until now, we didn’t know how far south the air currents were blowing from Antarctica. Now, we have evidence that Berg winds, which are katabatic winds caused by temperature differences between the ocean and the African continent, lift dust and transport it south during arid periods.”
To make this discovery, the team of researchers He used very sophisticated methods and instruments.
When dust is blown up by the wind, it remains suspended in the atmosphere until the right physical and chemical conditions exist for it to fall to the ground. Part of that deposited dust is “archived” in places like ice cores, seabeds, and peat bogs.
King and his master’s student Amélie Chaput collected sediment samples in four areas of the Namibian coast. Meanwhile, his colleagues went to Antarctica to take ice core samples.
Next, the team performed geochemical and isotopic characterization of the sediments collected on both continents. The chemical composition and properties of the dust were analyzed to compare the two regions.
“So we don’t capture dust in Antarctica, strictly speaking, but more precisely the isotopic signature of African dust.“, King explained. “The analysis confirmed that Namibia has had a much greater impact than previously thought; It’s the second or third source of dust in the southern hemisphere, after South America.”
Analysis of archived dust particles in ice cores also revealed that their origins have varied in different climatic periods. The Namibian dust particles found in Antarctica were deposited during interglacial periods such as the Holocene, the geological era that began about 12,000 years ago.
“We already knew that the Holocene was a period in which high temperatures and evapotranspiration caused increased aridity and the expansion of desert vegetation in southern Africa,” says King. “Our most recent study confirms the existence of drought-like conditions during interglacial periods, particularly the Holocene.
