Wednesday, March 2, 2011

How dry can the Earth's climate get? Researchers discover an ancient mega-drought.


Credit: Tomas Castelazo, Wikimedia Commons
Scientists have discovered one of the most intense and far-reaching droughts in the history of early modern humans, according to a new study recently published in Science magazine.  The drought, also referred to as the H1 Megadrought, affected large areas of Africa and Southern Asia, shrinking lakes, rivers, and vital freshwater supplies.  Lake Victoria, currently the world's largest tropical lake, dried up completely, as did Lake Tana, in Ethiopia.  Both lakes are primary water sources for the Nile River, suggesting that the mega-drought had severe ecological impacts on ecosystems and communities from East Africa to the Mediterranean coast.  

In addition, the study showed that the regular monsoon rains for these regions didn't just migrate south during the drought, as previously thought.  The rains weakened significantly as well, thus revealing that the mega-drought had a much greater geographical impact and was more catastrophic than previously believed.

Interestingly, an analysis of sediment cores revealed that the mega-drought took place roughly 16,000 to 17,000 years ago, which coincided with another major climate change event: the peak of the Heinrich Stadial 1, a massive surge of icebergs and meltwater into the North Atlantic at the end of the last ice age.  While it is still unknown whether the massive ice melt contributed or even caused the mega-drought, the study discusses possible ways that the Heinrich event may have influenced atmospheric and rainfall systems in favor of a drought.

The authors mention that the mechanisms that drive rainfall systems in the African-Asian region, which affect more than half of all humanity, are poorly understood and difficult to model. However, as the Arctic continues to melt at an unprecedented rate, the study raises valid questions about whether the current ice melt could, in theory, contribute to a similar drought.   

Sharinne Sukhnanand

These briefs are part of a weekly series of updates to the publication: Climate Change: Past, Present, and Future.  The entire series can be found here.

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