Cloud formation in Southern Ocean linked to plankton

Science : Clouds are created as water droplets nucleate around air-borne particles. In the Northern Hemisphere, about half those particles come from manmade pollution. But in the Southern Hemisphere, particularly over the Southern Ocean, where there is less human activity but significant cloudiness, a considerable amount comes from marine organisms, according to a study published in Science Advances. Daniel McCoy of the University of Washington and his colleagues studied NASA satellite data for clouds over the Southern Ocean. They found that the summer months had twice the droplet concentration as other times of the year, which they determined was due to the active phytoplankton population. Plankton seed clouds either by emitting a gas such as dimethyl sulfide or by leaving behind organic matter on the water’s surface, which gets tossed into the air by the ocean waves. Because clouds play a key role in climate and one that is not yet well understood, an international project—SOCRATES (Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study)—has been proposed to collect more data on the mechanisms of cloud formation.