Monday, May 7, 2001
Scripps Scientists Show for the First Time How Much Ocean Whitecaps Impact Global Temperatures
Scripps Institution of Oceanography / University of California, San Diego
FOR RELEASE: May 7, 2001
SCIENTISTS SHOW FOR THE FIRST TIME HOW MUCH OCEAN WHITECAPS IMPACT GLOBAL
A new study by scientists at Scripps Institution of Oceanography at the University of California, San Diego, has dramatically elevated the importance and influence of oceanic whitecaps on global climates.
Whitecaps, the bright, wind-driven result of breaking wave crests, have been mostly ignored by climate models.
In a paper that appeared in the April 15 edition of Geophysical
"Our estimate of the global radiative forcing by oceanic whitecaps is small, yet not negligible compared with the direct forcing by some greenhouse gases and even anthropogenic aerosols," said Frouin. "In contrast to well-mixed greenhouse gases, whitecaps are more localized, and their forcing may be much larger on regional and seasonal scales, with definite effects on climate."
Basing their new research on Frouins earlier findings that identified the spectral dependence of whitecap reflectance, the researchers used satellite data and other measurements to calculate how much solar radiation whitecaps reflect away from the surface. They found a global average of .03 watts per meter squared. However in certain regions, such as parts of the Indian Ocean, this average jumped significantlyin some cases up to .7 watts per meter squared.
This was particularly true in the case of the Arabian Sea, which can exhibit cloudless skies and great wind speedtwo important factors in increasing the role of whitecaps.
Previously, white caps were largely disregarded in climate models. Historically, they played a stagnant and incomplete role in these models. Most models pegged their importance on a broad brush figure, rather than a calculated global and regional influence factoring wind speed and cloud cover, as Frouin, Iacobellis, and Deschamps have done.
"Weve demonstrated that in certain cases these whitecaps might be important players in evaluating how regions respond to climate change," said Iacobellis. "Hopefully weve shown that whitecaps should be included in climate models."
The authors note that compared with carbon dioxide, whitecaps have a relatively small influence on climate. With other gases, however, such as nitrous oxide, whitecaps can have a comparable effect.
The authors also note that their findings play into the tangled equation of changes due to greenhouse gases. Greenhouse warming may change wind speed, thus altering the amount of whitecaps, and as a result changing the amount of radiation white caps reflect, ultimately changing heat content and temperatures.
"Many competing effects and feed-backs may be involved, and are difficult to untangle," said Frouin.
The research was supported by the National Aeronautics and Space Administration, the Department of Energy, the California Space Institute, the Centre National dEtudes Spatiales, and the Centre National de la Recherche Scientifique.
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Scripps Institution of Oceanography, at University of California, San Diego, is one of the oldest, largest and most important centers for global science research and education in the world. The National Research Council has ranked Scripps first in faculty quality among oceanography programs nationwide Now in its second century of discovery, the scientific scope of the institution has grown to include biological, physical, chemical, geological, geophysical and atmospheric studies of the earth as a system. Hundreds of research programs covering a wide range of scientific areas are under way today in 65 countries. The institution has a staff of about 1,300, and annual expenditures of approximately $155 million from federal, state and private sources. Scripps operates one of the largest U.S. academic fleets with four oceanographic research ships and one research platform for worldwide exploration.
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