The Southern Ocean (also known as the Antarctic Ocean) is one of the five great ocean basins on Earth. It was formed around 34 million years ago when Antarctica and South America drifted apart, creating the Drake Passage. This makes it the youngest ocean basin on earth.
Today, it is the only ocean that flows around the globe uninterrupted by land, encircling Antarctica like a moat. The Southern Ocean plays an important role in regulating the global climate by absorbing heat and carbon dioxide from the atmosphere and driving global ocean circulation.
The planet is heating up. Over the past 50 years, the ocean has absorbed over 90 percent of the excess heat produced by human activity. Most of this has taken place in the Southern Ocean, where a unique network of currents connecting surface waters with the deep ocean take extra heat from the surface to the depths, where it can be stored for centuries.
Ocean currents play a vital role in regulating the earth’s climate by moving water, heat, carbon and nutrients from one part of the ocean to another. Cold, salty water produced around Antarctica drives the deep, slow-moving currents that help regulate the earth’s climate.
Around Antarctica, the composition of the ocean is changing. In some areas it is becoming warmer, fresher and less dense. As Antarctic water becomes lighter its pumping action could become less powerful, leading to disruptive changes in global ocean circulation.
The ocean absorbs almost half of the carbon dioxide released into the atmosphere by human activity. Although the Southern Ocean only makes up 10-15% of the global ocean, it absorbs almost half of all the carbon dioxide taken in by the ocean.
If we continue on our current emissions trajectory, by 2300 the ocean will be more acidic than it has been in around 20 million years, and the rate of change could be faster than any time in history. We are entering uncharted territory, racing towards an ocean with a chemical composition we have never seen before.
Almost all Antarctic life begins and ends in the Southern Ocean. As the global climate changes, the Southern Ocean is becoming warmer and more acidic, which is having impacts on many Antarctic species.
On the West Antarctic Peninsula, this is happening faster than almost any other place on earth. Scientists report that Antarctic krill swarms and some penguin species appear to be migrating southward to cooler waters. Some colonies of ‘true’ Antarctic species, such as Adélie penguins, have disappeared, while species adapted to warmer conditions flourish.