Antarctica Undergoing Abrupt Change
Antarctica and the Southern Ocean are experiencing abrupt changes due to human-caused climate change, according to research published in Nature on Thursday.
The research review, led by Professor Nerilie Abram from the Australian National University (now Australian Antarctic Division Chief Scientist), shows that multiple rapid changes across the Antarctic environment are already underway, or imminent.
These abrupt changes include a rapid decline in sea-ice coverage, weakening of ice sheet and ice shelf stability, and population declines in some marine and terrestrial species, due to habitat loss.
“Human-caused climate warming can result in abrupt and unanticipated impacts on the environment that have far-reaching consequences, and can be difficult or impossible to reverse,” Abram said.
“It is worrying that the abrupt changes emerging in Antarctica have many interconnections, so that a change in one part of the system can trigger further impacts on Antarctica’s ice, ocean and ecosystems.
"Antarctic changes also have global consequences, including accelerating sea-level rise along our coasts, and amplifying human-caused climate warming."
The research team reviewed advances in knowledge since the last Intergovernmental Panel on Climate Change Assessment Report.
Their analysis also examined the impact of regime shifts – where the structure and function of a biological or physical system transitions from one state to another – on the functioning of Antarctica and its influence on the planet.
One of the key drivers of regime shifts in Antarctica is a change in sea-ice cover, itself a consequence of global warming.
Record summer sea-ice lows in 2017, 2022 and 2023 led scientists to suggest that a regime shift could be underway, resulting in a new state of diminished sea-ice cover.
Co-author and Australian Antarctic Division sea-ice scientist, Dr Petra Heil, said the team’s research review showed that the sea-ice cover deficit, in winter and summer, is far below what would be expected from natural variability.
Importantly, the rate of decline is dramatic when compared to the Arctic.
“In summer, the Antarctic sea-ice minimum has declined 1.9 times faster in 10 years than the summer sea-ice decline in the Arctic in 46 years, which is the length of the satellite record,” Heil said.
“The winter deficit of Antarctic sea ice over the past 10 years is of similar magnitude to the total Arctic winter sea-ice deficit over the past 46 years.”
The research team said there was overwhelming evidence of a regime shift in Antarctic sea ice, which will have flow-on effects to other parts of the environment.
These effects include the slowing of a global network of ocean currents (the Antarctic Overturning Circulation), which plays an important role in Earth’s climate stability by removing heat and carbon from the atmosphere and transporting these around the globe.
Sea-ice loss also exposes glacial ice shelves, which fringe the Antarctic continent, to damaging ocean swells and storms that weaken them, promoting iceberg calving from their front.
As ice shelves reduce the flow of glacial ice from the Antarctic interior to the coast, increased iceberg calving will speed the flow of glacial ice from the continent, directly contributing to sea-level rise.
The unseasonal or complete absence of sea ice, along with other climate-related changes such as atmospheric warming and ocean acidification, also contribute to habitat loss for marine and terrestrial species.
Emperor penguins, for example, which depend on land-fast sea ice to raise their chicks, are struggling to adapt to rapid changes in their environment, with several studies warning of their potential extinction by 2100.
Scientists are also reporting a regime shift in phytoplankton species, with a decline in those preferred by Antarctic krill – a critical food source for other marine creatures.
Abram said multiple aspects of climate change were now driving physical and biological changes in Antarctica and the Southern Ocean, rapidly modifying a complex system that is still to be fully understood.
“To improve the predictability of abrupt and potentially irreversible change in Antarctica and the Southern Ocean we need additional and year-round observations from satellites, autonomous technologies and targeted field campaigns, as well as better models and simulations,” Abram said.
“However, the only sure way of reducing the risk of abrupt changes is for the world to achieve true net zero emissions by the middle of this century, to limit further warming and stabilize climate change to as close to 1.5°C as possible.”