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The Tiny Cloud Factories of the Southern Ocean

ByTim De ChantNOVA NextNOVA Next

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It’s thanks to microbes that the dark and stormy Southern Ocean that encircles Antarctica is so dark and stormy. Whipped up by churning waters, they turn into a cloud-seeding aerosol froth that significantly cools the air over the ocean, according to new research.

Those tiny but mighty microbes double the density of cloud droplets in the summertime and raise the annual average by 60%, numbers that were derived using satellite data combined with computer models developed by a research team led by Daniel McCoy of the University of Washington and Susannah Burrows of the Department of Energy’s Pacific Northwest National Laboratory. Their results were published this month in the journal Science Advances.

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Wave clouds form over Île aux Cochons in the Southern Ocean.

The summery burst of activity is due to what you’d expect—the longer days. Here’s David Biello, reporting for Scientific American:

When the sunlight shines on the region from spring until fall, an array of photosynthetic life-forms bloom in the water. “The return of light in the summer ignites an amazing flurry of activity in phytoplankton,” says atmospheric scientist Daniel McCoy of U.W., who co-led the research with fellow atmospheric scientist Susannah Burrows of the Pacific Northwest National Laboratory.

It’s not unusual for biological processes to generate cloud cover—the Amazon is a perfect example of that—but the strength of the interaction between marine microbes and a large and volatile airmass is striking. The Southern Oceans’s clouds reflect up to 10 watts per square meter in the summer, which helps keep temperatures down.

The added albedo from the cloud cover helps keep temperatures in the Southern Ocean down, slowing the melting of the Antarctic ice sheet. But the plankton that help keep it cloudy are also at risk from carbon emissions—many of them have calcareous skeletons, which makes them especially vulnerable to rising ocean acidity.

Photo credit: NASA