April 28th, 2011 | By Thomas Lennartz | Filed in Global Warming, IN THE NEWS, SCIENCE
Science News has an intriguing story on the possibility of salt from sea spray entering the lower atmosphere and diffusing sunlight back, decreasing some of the warming.
The majority of sea-salt particles emitted into the air are well under a micrometer in diameter, notes climate scientist Hamish Struthers of Stockholm University. These tiny particles, known as aerosols, can persist in the air for days or even weeks, he says, and rise to altitudes of a kilometer or more. For the new study, he and his colleagues input into a computer program satellite measurements of seasonal changes in the Arctic albedo and surface measurements of a host of features including temperatures, ice cover and sea salt kicked up by waves on the ocean surface.
As expected, the salt clouds can exert a subtle cooling of the Arctic, the team reports online April 13 in Atmospheric Chemistry and Physics. Struthers says his group’s new calculations indicate that “the size of this [salt] aerosol effect is most likely 10 percent or less of the albedo [warming] effect” due to sea-ice melting. The effect is small, he acknowledges, but not negligible.
“Natural feedbacks in the climate system, such as the one described here, are potentially very important,” says Natalie Mahowald, an atmospheric scientist at Cornell University. “This is the first time I have seen this feedback mechanism discussed or quantified,” she says, making it “an interesting paper that describes a new mechanism for modulating climate in the Arctic region.”