Wednesday, October 12, 2005
Warming Atlantic linked to both US hurricanes and rainforest drought.
Michael Hopkin
A boat tries to make its way through a section of the Amazon River suffering from lower water levels near Uricurituba, in northern Brazil, on Tuesday, Oct. 4, 2005.
© AP Photo/A Critica, Euzivaldo Que
Parts of the Amazon rainforest are enduring the worst drought for 40 years, prompting local government to declare several cities in the Brazilian state of Amazonas as disaster areas. Researchers say that rising sea temperatures in the North Atlantic, perhaps prompted by climate change, are probably to blame.
Researchers at a forest monitoring station in Santarém, where the Amazon and Tapajós rivers meet, report that water levels are some 15 metres lower than usual.
"Everybody has been taken by surprise," says Paul Lefebvre, a researcher at the Woods Hole Research Center in Massachusetts, which runs the station.
Droughts in South America are often associated with El Niño climate events - oscillating changes to weather patterns that occur as a result of periodic warming of southern Pacific waters. But researchers have not spotted any such warming this year, Lefebvre says.
Instead, rising surface temperatures in the North Atlantic could be the culprit. The waters have been unusually warm this year - as shown to devastating effect by this year's unusually destructive tropical hurricane season.
The pressure's on
The warm waters tend to encourage evaporation, leading to low pressure systems over the Atlantic. This creates storm conditions that carry water and energy towards the United States. But it also sets up high pressure systems over neighbouring regions further south, such as the Amazon. High pressure systems tend to carry less cloud and provide less rainwater.
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