Bright, Highly-Reflective Southern Ocean Clouds Influenced by Plankton

New research suggests that bright, highly-reflective Southern Ocean clouds are significantly influenced by phytoplankton activity intensification during summer. What’s more, the study also helps reaffirm the massive importance of the tiny marine organisms to our planet’s climate situation.

These findings were published in Friday’s issues of the journal Science Advances and hope to highlight the massive role that plankton plays in the Southern Ocean’s cloud formation patterns.

Daniel McCoy, study co-author, explains that there is a significantly higher reflectivity of Southern Ocean clouds during the summertime, and it stems from the massive plankton blooms contributing to increased concentrations of cloud droplets.

The NASA-funded study examined a compound called dimethylsulfoniopropionate (or, for short, DMSP) in order to be able to trace the different types of aerosols in a cloud’s composition back to the phytoplankton it stemmed from.

DMSP is particularly helpful for cloud formation as it converts into minute aerosol particles. Yet the question that Daniel McCoy, together with researchers from the Pacific Northwest National Laboratory and the University of Washington wanted to answer was: why are southern ocean clouds brighter during the summer?

With the help of satellite data and computer models, the team of researchers were able to learn more about the composition of these brighter clouds. They concluded that they were not only more condensed, but were also formed around smaller droplets.

The discovery itself was somewhat of an odd coincidence. Data from NASA’s MODIS satellite revealed that Southern Ocean clouds were reflecting significantly more sunlight in the summer, despite the fact that its surface waters were much calmer than in the winter. Calmer waters lead to less sea salt spraying in the atmosphere, and thus, less aerosols. So there must have been another explanation.

Researchers soon discovered that it was plankton that was responsible for this massive aerosol contribution. Because of the bubbly yet impressive quantities of organic particles that were being released into the atmosphere, phytoplankton nearly doubled the cloud droplet concentrations atop the Southern Ocean.

And this paper has significant ramifications. For one, land aerosols differ greatly in the sense that they are polluted with man-made particles (pollution). Yet in this pristine area, scientists were able to truly understand this cycle without any human influence. Their conclusions help paint a bigger picture: plankton plays a massive role in our planet’s ecosystem, not only because of the fact that they supply close to 50% of the Earth’s oxygen, but also because they contribute to the atmosphere’s cooling by forming highly-reflective clouds.
Photo credits: PNAS