The sea ice cover in the Antarctica is shrinking much faster than in the north with “abrupt changes” now happening.
That was the finding of Australian research published in the prestigious journal Nature recently by a team led by Professor Nerilie Abram, chief scientists of the Australian Antarctic Division (AAD).
The findings reveal rapid changes in Antarctica and Great Southern Ocean such as shrinking sea-ice cover, a weakening of ice shelf stability and falling populations in some species as their habitat disappears.
“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,” Prof. Abram said.
“It is worrying that the abrupt changes emerging in Antarctica have many interconnections; 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 other research made since the last Intergovernmental Panel on Climate Change Assessment Report (sixth) was released in March 2023. (The authors for a seventh panel are currently being assembled.)
Their analysis examined the impact of ‘regime shifts’ (when a biological or physical system changes states) on Antarctica and its planetary influence.
SEA ICE EXPLAINED
- NASA explains that sea ice is frozen seawater floating on the ocean surface.
- It forms in at the poles in each hemisphere’s winter; it retreats in summer but does not disappear.
- This floating ice has a profound influence on the polar environment, influencing ocean circulation, weather, and regional climate.
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SHIFTING REGIME
The research reports that a key driver of regime shifts in Antarctica is changing sea-ice cover, itself the result of planetary warming.
Scientists say that record summer lows in sea-ice (2017, 2022 and 2023) suggest that such a regime shift could be under way, causing the sea-ice cover to shrink.
Study co-author and sea-ice scientist, Dr Petra Heil says the team’s research shows that the year-round sea-ice coverage is far smaller that could be expected from natural changes.
The rate of decline is also dramatic compared to that in the Arctic, they say.
“In summer, the Antarctic sea-ice minimum declined 1.9 times faster in 10 years than the summer decline in the Arctic in 46 years, which is the length of the satellite record,” Dr Heil says.
“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 is “overwhelming evidence” of a regime shift in Antarctic sea ice, which will be felt elsewhere.
GOING WITH THE FLOES
These effects include a slowing in global ocean currents (the Antarctic Overturning Circulation), which usually removes heat and carbon from the atmosphere and circulates them around the globe.
Sea-ice loss is also exposing glacial ice shelves on the edge of the Antarctic continent to damaging ocean swells and storms that weaken them, promoting iceberg calving (when icebergs separate from the shelf).
Ice shelves reduce the flow of glacial ice from the continent’s interior to the coast but more calving will speed that flow to the coast and directly contribute to rising sea-levels, the division says.
The unseasonal absence of sea ice, and other climate 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 chicks, are struggling to adapt to rapid changes in their environment; several studies warn of their potential extinction by 2100.
Scientists are also reporting a regime shift in phytoplankton species with a fall in those preferred by Antarctic krill, a critical source of food for other marine creatures like whales.
WHAT NEXT?
Professor Abram says climate change is driving physical and biological changes in Antarctica and the Southern Ocean, environments that still have to be fully understood.
“To improve the predictability of abrupt and potentially irreversible change in Antarctica and the Southern Ocean we need additional year-round observations from satellites, autonomous technologies and targeted field campaigns, as well as better models and simulations,” Prof. Abram says.
“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 stabilise climate change to as close to 1.5 degrees Celsius as possible.”
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