The research team, however, strongly suspected that the air over the Southern Ocean would be protected from human activity and pollution.
The researchers found that the air of the boundary layer, which feeds the lower clouds over the Antarctic Ocean, was free of aerosol particles produced by human activity- including the combustion of fossil fuels, the planting of certain crops, the production of fertilizers and the disposal of waste water - or transport from other countries of the world.
In 2019, researchers had identified Cape Grim in Tasmania, near the northern edge of the Southern Ocean, as the previous site with the cleanest air in the world. Sure, it's refreshing, but according to scientists at Colorado State University, the cleanest air on Earth isn't near your home or any area where humans have settled.
Weather and climate are complex processes connecting each part of the world to every other region, and with climate changing rapidly as a result of human activity, it's hard to find any area or process on Earth untouched by people. They studied the composition of microbes found in the air, which may offer a clue to where the air has been.
"The aerosols controlling the properties of SO (Southern Ocean) clouds are closely linked to ocean biological processes, which Antarctica seems to be isolated from southward dispersal of microorganisms and nutrient deposition from southern continents", Thomas Hill, co-author of this analysis, said in a statement.
Scientists gathered samples during the NSF-funded SOCRATES field campaign, led by research scientist and coauthor Paul DeMott.
The examination of the composition of airborne microbes, which can be dispersed thousands of miles by wind, helped immensely with the study.
Aerosol filter samplers probe the air over the Southern Ocean on the Australian Marine National Facility's R/V Investigator. Using DNA sequencing and tracking methods, the study's first author Jun Uetake discovered that the microbes' origins, in fact, were from the ocean. They discovered that the microbes likely originated in the ocean.
The team's samples showed no aerosols or other particles that were connected to human pollution or other activity. Plants and soil are strong sources of particles that trigger the freezing of supercooled cloud droplets, known as ice-nucleating particles. There is so little on Earth that we haven't been impacted in one way or another, but the fresh, clean air over the cold Southern Ocean still remains. Thanks to some disturbances of global climate and weather patterns, clouds over the Southern Ocean are natural.