Clean Air at the End of the World

From the depths of the deepest ocean trenches to the seemingly pristine snow atop mountains, traces of human-related activities in the form of pollution such as microplastics and atmospheric aerosols keep turning up wherever scientists look. A 2020 expedition, however, led by researchers from Colorado State University, has identified the air just above the surface of the Southern Ocean, surrounding Antarctica, as one of the few places on Earth that has been relatively untouched by anthropogenic activities.

The research team sailed south from Tasmania to just off the coast of Antarctica taking numerous measurements of the marine bacteria in the ocean water samples at various depths, samples of air quality, including bacteria and microorganisms in the air, as well as soil samples in Tasmania and the coasts of Australia. In the northernmost areas studied, the team found a wide array of airborne bacteria, much of it originating from winds from the continent transporting dust over the ocean. In fact, bacteria can stay aloft and remain alive for several days after getting carried away from their continental sources. South of 60°S, which is considered the boundary of the Southern Ocean, they found much less diversity of airborne bacteria life and microorganisms, with virtually all of it coming from the surface of the ocean itself, carried aloft by the wind in sea spray.

The reason why the air surrounding Antarctica is so devoid of airborne pollutants is linked to one of the mechanisms keeping the continent so cold, namely the Antarctic Circumpolar Current. This eastward flowing current is one the fastest in the world, and completely encircles the globe around the periphery of the Antarctic continent. Reinforced by persistent west-to-east winds, the combination of the ocean and wind currents effectively seals off Antarctica from any significant intrusions of warmer ocean waters and also keeps pollutants from other continents away.