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The Southern Ocean (also called the Antarctic Ocean) encircles Antarctica, connecting the Atlantic, Indian and Pacific Oceans together and makes up about 15% of the world’s ocean surface.It supports global ocean circulation and plays a vital role in moderating the rate of climate change.
Despite its remoteness, the Southern Ocean is under mounting pressure by the worsening impacts of climate change–accelerating ice sheet loss, killing off marine populations, and threatening local ecosystems.
These changes will have global implications.
Pressing Threats to Climate and Biodiversity in the Southern Ocean
Ice Sheet Loss and Warming Waters
Estimates show that the Southern Ocean has absorbed 75 percent of excess heat trapped by greenhouse gases since the 1970s, making it the largest oceanic heat sink. This intense warming largely drives the acceleration of ice sheet loss in the Antarctic.
In March 2025, Antarctic sea ice extent reached a near-record low of 1.98 million square kilometers, tied with 2022 and 2024 for second lowest minimum recorded in the satellite’s 47 year history.
Thwaites Glacier, nicknamed Antarctica’s ‘Doomsday Glacier’ is melting even faster than scientists originally thought. The glacier already loses 50 billion tons of ice annually, but if it collapses, it could raise sea levels by 65 centimeters.
Industrial Fishing and Declining Krill Populations
Antarctic krill are a crucial part of the Antarctic food web, acting as a vital source of food for whales, seals, and penguins. They also act as carbon-storing powerhouses, with estimates showing that they can sink 23 megatonnes of carbon annually, with the carbon to be stored in the ocean for up to 100 years.
Rapidly declining sea ice, a key feeding ground for krill in the Southern Ocean, is taking krill populations with it, threatening the entire food chain in Antarctica. An estimated 80% of the krill population has declined since the 1970s.
Commercial fisheries in the Southern Ocean are further threatening the livelihoods of marine ecosystems, primarily targeting Antarctic krill and Patagonian and Antarctic toothfish. These fisheries also introduce invasive species and worsen levels of plastic pollution.
Ocean Acidification and Ecosystem Vulnerability
The Southern Ocean absorbs around 40% of anthropogenic carbon dioxide emissions taken up by the world’s oceans, making it a crucial carbon sink. Because of this, the Southern Ocean is particularly vulnerable to ocean acidification–the decrease of pH in ocean water caused by rising levels of atmospheric CO2.
Although slow-setting, the Southern Ocean is said to be one of the first places to be impacted by ocean acidification, particularly so for calcifying organisms like krill, sea snails and coral.
As it intensifies, the Southern Ocean’s ability to function as a carbon sink could also weaken, reducing the ocean’s capacity to buffer climate change.
Green Party Responses and Plans of Action
The Australian Greens have been vocal about the importance of Antarctic research and protection. Their spokesperson for Science Steph Hodgins-May states:
“Antarctica and the Southern Ocean play a significant role in regulating global weather patterns and studying them is critical to understanding our planet’s rapidly changing climate”.
The Greens have pushed for better funding for the Australian Centre for Excellence in Antarctic Science, noting that now is the most important time to invest in Antarctic science. They have also condemned Japan for the possibility of resuming whaling in the Southern Ocean.
More largely, the Greens are committed to the protection of the world’s oceans and its supported livelihoods, including through investing in sustainable fisheries, banning seismic blasting, and protecting and restoring coral reefs.
The Green Party of Aotearoa New Zealand plays a significant role in vying for the protection of the world’s oceans and its marine life.
The New Zealand Greens consistently support and call for increasing marine protected areas, such as the one that spans 72% of the Ross Sea region of the Southern Ocean. These marine protected areas are vital to the protection of complex ecosystems and allow for research of the impacts of overfishing on krill populations.
Largely, the Greens also want to pass a legally binding Healthy Oceans Act to protect 30% of local oceans by 2030, establish a Healthy Oceans Commission that works iwi, hapū, and local communities to advise the government on solutions that work for people and nature, and calls for bans on destructive corporate fishing methods and a moratorium on deep sea mining.
While not close in proximity to the Southern Ocean, the European Greens deem Antarctica a part of the ‘common heritage of mankind’, calling for the protection of the global commons–including the high seas and Antarctica.
The European Greens also call on the withdrawal of territorial claims on Antarctica and to minimise the impact of human activities, and further welcome the establishment of the Ross Sea and additional areas of the Southern Ocean as marine protected areas.
Opportunities for Future Action
The Southern Ocean is critical to the fight against climate change. It moderates global temperatures, stores massive amounts of carbon, and supports unique marine life. Even so, its resilience is being pushed to the limit by warming waters, melting ice sheets, collapsing krill populations, and ocean acidification.
To preserve the Southern Ocean and the Antarctic region is of utmost importance. With stronger coordination, Green parties can help to build momentum, spread awareness, and contribute to saving our world’s oceans.