The Southern Ocean has the earth’s cleanest air — scientists finally know why

The Southern Ocean is renowned for having the cleanest air on Earth. But the precise reasons why have remained a mystery, until now.

There’s more to it than just a lack of human activity. Yes, there are fewer people down there using industrial chemicals and burning fossil fuels. But there are natural sources of fine particles too, such as salt from sea spray or dust whipped up by the wind.

Regardless of origin, fine solid particles or liquid droplets suspended in air are known as “aerosols”. We consider clean air to have low levels of aerosols, without discriminating between natural or industrial sources.