According to a study published today in Atmospheric Chemistry and Physics, the teeming life in the Southern Ocean, which encircles Antarctica, helps to brighten the clouds that form there.
The clouds are bright because of their high density of water droplets, which is caused by a chain of atmospheric processes that eventually connects back to the Southern Ocean's extraordinary phytoplankton productivity.
Aerosols and clouds
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Clouds are made of water droplets and ice crystals, despite their dreamlike wispiness or fluffiness.
Water vapor condenses around something in the atmosphere, such as an aerosol particle, which is also known as a "cloud condensation nucleus," to form those droplets, as per ScienceDaily.
According to Mace, the amount of water available to condense to form a cloud is fixed in most situations, but the number of droplets that form from that fixed amount of water vapor depends on the number of aerosol particles present.
So, when a region of the atmosphere contains a high number of aerosols, clouds that form have a large number of cloud condensation nuclei available, as well as a high density of cloud droplets, or the number of droplets per volume of the cloud.
Mace and his colleagues, including scientists from Australia's CSIRO Oceans and Atmosphere and the University of Tasmania, wanted to study droplet density in Southern Ocean clouds.
The researchers examined the properties of clouds in the Southern Ocean using satellite data from 2014 to 2019.
They focused on a region between Madagascar and New Zealand that had been visited by research vessels and aircraft during the summer of 2017 to 2018.
These research missions' on-the-ground data supplemented the satellite observations.
The researchers worked to determine where clouds had traveled before arriving in the "airspace" around Antarctica while studying cloud trends.
They noticed a distinct difference between the two groups of clouds.
Clouds with low droplet densities were likely to have migrated from higher latitudes, where salt in the air from spraying ocean water is one of the primary cloud condensation nuclei.
Clouds with relatively high droplet densities, on the other hand, were more likely to have formed over the Antarctic continent and passed only over the waters of the Southern Ocean.
The primary distinction between the two groups of clouds was the productivity of plankton in the Southern Ocean.
Plankton, which thrives in the cold, nutrient-rich Antarctic water, emit sulfate gases as part of their metabolism.
Those gases can cause atmospheric chemical reactions that form aerosols in the relatively still summer air of the Southern Ocean.
Because it is atmospherically isolated from the rest of the world, the Southern Ocean is an ideal location for studying natural cloud formation processes.
That is, it is free of the aerosols produced by anthropogenic (caused by humans) activity, as per Phys.org.
The Southern Ocean also has a significant impact on the global climate.
Plankton productivity aids the Southern Ocean in removing carbon dioxide from the atmosphere and "sequestering" it in the oceanic food chain.
However, the productivity of the ocean is linked to how much sunlight its waters receive, which is linked to cloud reflectivity and droplet densities.
He claimed that the process occurs in all of the world's oceans, but that it is more pronounced in the Southern Ocean due to its isolation from other aerosol sources.
Phytoplankton are essential components of marine ecosystems.
They are producers, or autotrophs, who serve as the foundation of the majority of marine food webs.
They can convert solar energy into chemical energy and store it as sugars because they are photosynthetic organisms.
Heterotrophs, or consumers, must consume energy that has already been converted into chemical energy.
Consumers can consume autotrophs directly or consume other consumers.
Other small organisms, such as zooplankton, consume phytoplankton.
