Climate change is one of the most urgent issues facing humanity and life on Earth.

Whilst our everyday understanding of climate concerns the warmth of the atmosphere, the ocean is critical in controlling how our planet’s climate changes. This is because the ocean absorbs vast quantities of heat and carbon dioxide which, if they had remained in the atmosphere, would have greatly accelerated the rate of climatic change there.

Since the industrial revolution, the global ocean has absorbed around 30% of anthropogenic (human-produced) CO₂ emissions. In addition, 93% of the total extra heat in the Earth System since the onset of global warming has been absorbed by the ocean. This is equivalent to around 170 terawatts, the power that would be required for each of the 7 billion people on Earth to continuously operate sixteen 1500 watt hairdryers.

Improving climate prediction thus requires us to learn more about how the ocean works, and how it interacts with the atmosphere to control the split of heat and carbon between them. A key region in this context is the Southern Ocean, the vast sea that encircles Antarctica.

Although the Southern Ocean occupies only around 20% of the total ocean area, it absorbs about three-quarters of the heat that is taken into the ocean, and approximately half of the CO_2. This is because of its unique pattern of ocean circulation: it is the key region globally where deep waters upwell to the surface from 1-2 km down, allowing new water masses to form and sink back into the ocean interior. This exposure of old waters to the atmosphere, and the production of new waters, is fundamental to the exchanges of heat and carbon with the atmosphere. More information on how the Southern Ocean influences global climate can be found in a recent article in Nature; click here.