Scientists will have to improve understanding of how these aerosol particles can brighten clouds.
Satellites use chlorophyll’s green color to detect biological activity in the oceans.
Published in the Science Advances journal on July 17th, the study took a closer look at the Southern Ocean plankton and its role in bright cloud formation. In fact, McCoy explains, during the summertime, the team identified approximately double the concentration of cloud droplets than they would have expected from a biologically dead ocean.
Although remote, the oceans in the study area between 35 and 55 degrees south is an important region for Earth’s climate. Over a one year timeframe, the cloud droplets that form thanks to the plankton lead to the formation of bright clouds that average a reflection of 4 watts/square meter in solar energy.
“The clouds over the Southern Ocean reflect significantly more sunlight in the summertime than they would without these huge plankton blooms”, said co-lead author Daniel McCoy, a UW doctoral student in atmospheric sciences, in a release. The data was collected using an imaging spectroradiometer, or MODIS, an instrument NASA first used in 1999 to measure the cloud droplet size for all Earth’s skies, a release said. Ocean aerosols, on the other hand, stem from sea salt being shot into the atmosphere.
The new study looked more closely at what else might be making the clouds more reflective.
Aerosol concentration is crucial for climate sensitivity to greenhouse gas inputs, says Susannah Burrows, an atmospheric scientist at the Pacific Northwest National Laboratory in Richland, Washington, and a co-author of the new study.
Tiny ocean life contribute to clouds directly, by being lofted up with sea spray, and indirectly, by producing sulfurous gas. As organic matter brimms at the surface of the Southern Ocean, the wind picks it up and stirs it through the air, adding to the organic component of bright cloud formation.
In an effort to determine the specific roles of different types of aerosols, Burrows, McCoy, and their colleagues simulated organic matter, sulfates, and sea salts with computer models. Marine organisms produce aerosols too but most evaporate. According to the research team, there are two mechanisms that lead to cloud droplets formation and to the bright clouds later one. It is necessary to stress once again that the position of the Southern Ocean is very important for research related to the level of purity of the environment. “Really the marine aerosols are running the show there”. And with the aerosol data duly simulated, they discovered it was quite similar to actual cloud droplet data.