Antarctica and its extraordinary icy landscapes may not be on our minds daily. Yet, this icy continent is changing rapidly, and these transformations are influencing everything from sea levels to ecosystems.
On most maps, Antarctica is shown as a thin strip at the bottom of the world. For oceanographers, however, Antarctica lies at the centre of the global ocean. The Pacific, Atlantic, and Indian Ocean basins extend north from the continent, and their currents converge around Antarctica, transporting water, heat, salt and nutrients.
“Sea ice, the thin layer of frozen sea water that forms in winter and melts during summer, plays a key role in driving these global ocean currents,” says Edward Doddridge, physical oceanographer from the Institute for Marine and Antarctic Studies in Tasmania.
Unprecedented sea ice loss: the bigger picture
“In recent years we have seen a collapse in Antarctic sea ice. Coverage in 2023 was the lowest ever recorded. And for the first time, sea ice loss was seen in Winter. The scale of ice loss was unprecedented.”
Doddridge is part an international cohort of scientists working to understand why this sea ice decline is occurring. His research focuses on how heat moves through the oceans to Antarctica, how subsurface heat affects sea ice, and whether observed changes are temporary ‘blips’ or permanent shifts.
His work advances the scientific community’s understanding of the global climate system. In particular, how it is changing, and the impacts of those changes on our world. This work directly informs Intergovernmental Panel on Climate Change (IPCC) reports, used by governments to inform policy.
The science beneath the ice
Doddridge and other ocean and climate scientists rely on computer modelling, satellite data, and more than 4,000 autonomous ocean floats to monitor ocean conditions and ice changes in near-real time.
A key part of Earth’s climate system is the ocean’s ‘overturning circulation’ — a global network of currents that move heat, carbon, and nutrients around the planet.
Warm, salty water flows from the tropics toward the poles. Around Antarctica, it cools, becomes denser, and sinks deep into the ocean. This water slowly returns to the north, bringing nutrients to the surface and helping to regulate the climate.
When sea ice melts, it releases fresh water, less dense than salty water. This stabilises the surface layer, making it less likely to sink, and slowing the deep circulation.
Rising global temperatures warm the upper ocean even further, weaking the sinking motion that drives this circulation.
“If this circulation weakens significantly, it can disrupt how the ocean stores and moves heat, carbon, and nutrients, with far-reaching effects on global climate systems including weather patterns, sea levels, and marine ecosystems.”
The loss of Antarctic sea ice not only threatens ecosystems. It also threatens wildlife.
“This ice loss heightens the extinction risk for Emperor Penguins. Their breeding colonies, that live on the frozen sea ice, are vulnerable. Their chicks rely on stable sea ice ahead of growing their waterproof feathers.”
“Antarctica and its changing ice and oceans are intrinsic to life on the planet. Antarctica Day is a day on which to pause and consider the importance of that thin strip at the bottom of the map and the alarming changes we have seen unfold in recent years.”
Read some of Doddridge’s work and recent contributions here:
Emerging evidence of abrupt changes in the Antarctic environment, published in Nature.
A multidisciplinary paper examining the impacts of Antarctic summer sea ice loss.
Record low Antarctic sea ice coverage indicates a new sea ice state, published in Nature.