Study Sees Ocean Impact on Amazon
12/24/99
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Title: Study sees ocean impact on Amazon
Source: Environmental News Network, http://www.enn.com/
Status: Copyright 1999, contact source for permission to reprint
Date: December 24, 1999
Byline: Robinson Shaw
Dec. 24 - New research shows that the sea surface temperature of the
Atlantic and Pacific oceans surrounding South America has as much of
an influence on rainfall as do changes in land cover, according to
Rong Fu, an atmospheric scientist at the Georgia Institute of
Technology.
"I WAS SURPRISED by the strength and influence of the western
Pacific's sea surface temperatures on Amazon rainfall because
moisture from the Pacific Ocean has to travel over the Andes
Mountains before it reaches the Amazon region," said Fu.
The results of his research were presented at the American
Geophysical Union's fall meeting in San Francisco, California. The
new finding will help scientists better predict impending drought or
floods.
Fu linked rainfall patterns over the Amazon with sea surface
temperatures in the tropical Atlantic and Pacific oceans using a
computer climate model. When he plugged El Nio data into the model,
he found that the rainfall pattern in the eastern equatorial Amazon
region of Brazil was extremely sensitive to temperature changes on
the sea's surface. When the sea surface temperature increased,
drought conditions appeared. When it dropped, flooding resulted.
Fu was surprised to find that precipitation was relatively unaffected
by El Nio in Columbia and Peru, two countries west of Brazil.
To determine which ocean had the greatest effect on rainfall changes,
Fu removed Atlantic sea surface temperature readings from the model.
Spring, normally Brazil's dry season, registered as its wettest. When
Fu removed the eastern Pacific Ocean, sea surface temperature showed
a similar, if weaker, effect on rainfall.
It wasn't until Fu removed western Pacific sea surface temperature
readings that an unexpected result occurred. Water evaporating from
the Atlantic Ocean takes a direct route to Brazil and returns to
Earth in the form of rain. Thus, Fu expected the Atlantic to have a
greater impact on rainfall patterns in the Amazon. But the Pacific
influence proved stronger even though evaporation from the Pacific
must travel over mountains to reach Brazil.
Fu plans to mimic the effects of deforestation by changing the lush
rain forest cover to semi-arid grasslands in the model. He believes
the change will show the likelihood of drought conditions.