A recent study studying the composition of cloud-forming aerosols has concluded that phytoplankton is responsible for half the droplets covering the Southern Ocean. These findings may represent an important piece of the climate change puzzle. Because of their slightly different composition, the clouds formed during the summer are brighter and highly reflective, contributing to a cooling effect.
Marine phytoplankton has often been overlooked. In all honesty, the tiny marine organisms aren’t that imposing, however, we may have underestimated their effects. Phytoplankton is represented by tiny organisms relying on light to grow and reproduce, however, they are also responsible for producing tiny aerosols contributing to the droplets serving as a precursor to the bright clouds atop the Southern Ocean.
Researchers from the University of Washington and the Pacific Northwest National Laboratory have been investigating exactly how phytoplankton contributes to cloud formation. There are different types of aerosols: on land, aerosols are a combination of dust, pollution and vegetation-stemming ones. Ocean aerosols differ in the sense that they are mostly comprised of sea salt that is spewed into the atmosphere. But aside from the large amounts of sea salt, marine organisms such as phytoplankton also contribute to aerosol levels.
Differentiating between the multiple types of aerosols isn’t an easy task. Once aerosols enter the atmosphere, it’s particularly difficult to connect them to certain sources, however, the team of researchers used satellite data as well as computer modelling programs in order to determine the origin of these aerosols.
They concluded that in those areas of the Southern Ocean where green phytoplankton was abundant, so were clouds wealthy in water droplets. Using dimethyl sulfide to track the aerosols produced by phytoplankton (it transforms into sulfate once entering the atmosphere), the team of scientists could deduce that phytoplankton was responsible for half of the droplets covering the Southern Ocean.
What’s more, the number of cloud droplets was then linked to the sunlight reflective capacity of the clouds. Researchers observed that the amount of light reflected by these highly reflective summer clouds was over 60 percent higher than that of clouds formed in other periods of the year. As compared to the 4 watt per meter capacity in reflected sunlight throughout the year, phytoplankton-improved aerosols contributed to clouds amounting to 10 watt per square meter sunlight reflective capacity during the summer.
“The return of light in the summer ignites an amazing flurry of activity in phytoplankton communities across the Southern Ocean. This seasonality leads to an enhancement in cloud brightness when it will be able to reflect the most sunlight,” Daniel McCoy, study co-author explains.
Photo credits: Wired
