Wind currents insulate Southern Ocean air from man-made contaminants
Although the Covid-19 pandemic has led to a remarkable decrease in the world’s air pollution, air quality prior to the global shutdown was notably poor in cities from Los Angeles to Delhi. Now researchers have found a pocket of pure air—apparently uncontaminated by human activity—along a latitude north of Antarctica.
The study—the first of its kind to survey the air of the Southern Ocean—was led by Sonia Keidenwies, professor of atmospheric sciences at Colorado State University. It found the atmosphere over the Southern Ocean to be “pristine.”
Airborne contaminants include man-made sources such as fuel combustion and energy production and can cause serious health issues such as increased cancer risk. According to the World Health Organization, airborne pollution kills an estimated 7 million people per year.
But particulate matter from pollution is not confined to the exact location where it is produced. Wind currents can spread contaminants from one region to another, for example, through intercontinental microbial transport. According to the study, “Airborne microorganisms may be transported thousands of kilometers by atmospheric winds due to the long residence time of typical cell sizes.”
“Airborne microorganisms may be transported thousands of kilometers by atmospheric winds”
Scientists used a technology called high-throughput sequencing to identify airborne microorganisms. By discovering which microorganisms are present in a sample, they can determine where the air came from and thus the origins of airborne contaminants.
In the CSU study, researchers analyzed the contents of boundary-level air—the air that comes in direct contact with the ocean—above the Southern Ocean and found that the microorganisms in the air had almost all originated in the ocean, either from the west or south. They concluded that the air in the Southern Ocean was isolated from air from continents to the north, shielding it from contamination from human pollution. What accounts for this? The Southern Ocean region is protected by two unique wind currents, the Antarctic circumpolar current, and the atmospheric circumpolar vortex. These currents block warm air coming from the north and protect the Antarctic’s sheet ice, but they also serve to protect the air.
As climate change and pollution threaten human health, pure air that may be insulated from pollution is a welcome discovery. Thomas Hill of CSU, a coauthor of the study, told CNN that the team’s work “suggests that the Southern Ocean is one of the very few places on Earth that has been minimally affected by anthropogenic activities.”