Hurricanes linked to sea colour

2010-08-16 07:24

Washington - A change in the colour of the ocean could dramatically impact the number and intensity of hurricanes, according to US researchers.

A team of researchers with National Oceanic and Atmospheric Administration (NOAA) ran computer simulations of such a change in the North Pacific, a region that accounts for more than half the world's hurricane-force winds.

The main factor is the green tint ocean water takes when there are large concentrations of chlorophyll, a pigment that helps tiny organisms known as phytoplankton convert sunlight into food for the rest of the marine ecosystem.

"We think of the oceans as blue, but the oceans aren't really blue, they're actually a sort of greenish colour," said lead researcher Anand Gnanadesikan in a statement released on Friday.

"The fact that (the oceans) are not blue has a (direct) impact on the distribution of tropical cyclones," Gnanadesikan said.

Without chlorophyll, sunlight penetrates deeper into the ocean, leaving the surface water cooler.

Cold water in turn causes changes in air circulation patterns, forcing strong winds aloft, "which tend to prevent thunderstorms from developing the necessary superstructure that allows them to grow into hurricanes," the researchers said.

Phytoplankton populations around the world have been declining over the last century, the researchers said, citing recently published research.

The study is to appear in an upcoming issue of the journal Geophysical Research Letters.

- AFP

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