Global warming: Tropical storms revealed as new factor in heat mix
Pastor Dale Morgan
Global warming: Tropical storms revealed as new factor in heat mix*
PARIS, May 30 (AFP) May 30, 2007
Hurricanes and typhoons play a significant role in distributing the
ocean's heat, say US researchers, who believe they have uncovered a
major, but hitherto-ignored aspect of global warming.
Driven by mighty circular winds, cyclones in the western Atlantic,
western Pacific and Indian Ocean have long been known to whip up the sea
and leave its local surface areas cooler than before.
In a paper appearing on Thursday in Nature, the weekly British science
journal, Matthew Huber and Ryan Sriver of Purdue University in Indiana
make the first stab at calculating how and where this displaced heat,
driven from the surface by the cyclone, ends up.
Their computer model factors in surface sea temperatures before and
after a storm's passage, as well as ocean depth and currents.
They found that a cyclone acts rather like the spinning steel blades of
a food mixer as it is lowered into a bowl of batter.
The whirling winds so churn the sea that the surface heat is distributed
down vertically, towards the depths of the local ocean area, but also
circulating it towards the poles.
As much as a seventh of heat transported by the oceans could be linked
to cyclones, the paper says.
The finding is important, because future climate change depends to a
very high degree on the oceans, which cover two-thirds of the planet's
surface and soak up massive amounts of heat from the atmosphere.
The role of cyclones has been overlooked until now, Huber and Sriver
believe, because computer models of the world's climate systems only
factor in sustained winds that last longer than five days, which would
leave out most storms.
Further investigation into cyclone mixing is needed, they say.
If cyclones become more frequent as a result of higher sea temperatures,
this in turn will step up the distribution of warm waters to higher
latitudes, they warn.
That, in turn, would have plenty of potential for knock-on effects to
the climate system.
"Cyclone-induced mixing is a fundamental physical mechanism that may act
to stabilise tropical temperatures, mix the upper ocean and cause polar
amplification of climate change," the researchers say.