Iconic Antarctic species at risk amid 'regime shift', scientists say, with 'rapid and self-perpetuating changes'

Australia Broadcast Center

a day ago

Scientists say there is emerging evidence of abrupt and potentially unstoppable changes in the Antarctic environment.
The changes are heightening the risk of significant sea level rise and the extinction of species, including emperor penguins.
The research, led by ANU climate scientist Professor Nerilie Abram and co-authored by 20 other scientists, has been published in the science journal, Nature.
"We're seeing really worrying changes starting to develop across the ice and the ocean and the biological systems in Antarctica," said Professor Abram, who is now the chief scientist at the Australian Antarctic Division (AAD).
"Importantly, we're seeing that those changes are all interlinked.
The report synthesises multiple recent studies that examined four key parts of the Antarctic and Southern Ocean environment:
"Evidence is emerging for rapid, interacting and sometimes self-perpetuating changes in the Antarctic environment," the report states.
It says reducing greenhouse gas emissions is the best way to mitigate the impact of the broad-scale changes affecting the polar region.
"Stabilising Earth's climate with minimal overshoot of 1.5 degrees Celsius will be imperative alongside global adaptation measures to minimise and prepare for the far-reaching impacts of Antarctic and Southern Ocean abrupt changes," the report says.
However, it warns it may be too late to prevent some changes due to human-caused climate change.
Antarctic sea ice contracts and expands around the continent between the summer and winter months.
But the report says significant declines in its seasonal extent have been observed over the past decade.
"A regime shift has reduced Antarctic sea-ice extent far below its natural variability of past centuries, and in some respects is more abrupt, non-linear and potentially irreversible than Arctic sea-ice loss," it says.
Since 2014, the report says the median contraction of the Antarctic sea-ice edge has been around 120 kilometres.
The most significant decline was in the winter of 2023, which was so far below previous satellite records and historical modelling that scientists described it as "gobsmacking".
Since then, the extent of sea ice has remained at near record lows.
"So we've lost areas of ice somewhere between the size of NSW and WA," Dr Edward Doddridge, a physical oceanographer from the Australian Antarctic Program Partnership, told the ABC.
The report says the abrupt decline in Antarctica's winter sea-ice extent over the past decade has been 4.4 times faster than reductions seen in the Arctic over the past 46 years.
It suggests ocean warming is contributing to the recent decline in sea-ice extent, which in turn is exacerbating the problem by creating a "self-perpetuating process".
"Thinning of Antarctic winter sea ice has resulted in earlier retreat that has increased ocean surface warming and delayed the formation and thickening of sea ice the following winter," the report says.
It says the process "may be irreversible", even if global temperature rises remain under 2 degrees Celsius, compared with pre-industrial levels.
Deep ocean currents, known as the Antarctic Overturning Circulation, help regulate the climate by transporting heat, carbon, nutrients and oxygen to other areas.
But observations and modelling show the process is rapidly slowing down, according to the report.
"The Antarctic Overturning Circulation is already undergoing rapid change at current warming levels and will continue to decline in the 21st century," it says.
"This decline may be even more abrupt than the equivalent Northern Hemisphere processes."
The report says the slowdown could reduce the ability of the Southern Ocean to sequester anthropogenic CO2, "generating an amplifying feedback that intensifies climate warming over multiple centuries".
"Slowdown or collapse of the Antarctic Overturning Circulation would lead to widespread climate and ecosystem impacts," it says.
Antarctica's landmass is covered in a vast ice sheet, with ice shelves on the perimeter.
The most vulnerable region is in the west of the continent, which has the potential to raise sea levels by several metres if it were to melt, according to scientists.
"The tipping point for unstoppable ice loss from the West Antarctic Ice Sheet could be exceeded even under best-case CO2 reduction pathways, potentially initiating global tipping cascades," the report says.
Professor Abram said the instability of ice shelves across the continent was particularly concerning, given their role in buttressing large glaciers from the impact of the ocean.
"Where the ice is in contact with the ocean, it makes it particularly vulnerable to being able to be eroded by that warm water and can set up processes that once they start, they become unstable," she told the ABC.
The report points to the sudden collapse of the Conger-Glenzer ice shelf in 2022 as an example of the abrupt changes taking in in Antarctica.
Sustained climate pressures are also impacting the region's plant and animal species, the report says.
"Regime shifts are occurring in Antarctic and Southern Ocean biological systems through habitat transformation, or exceedance of physiological thresholds, and compounding breeding failures are increasing extinction risks."
The report highlights the existential threat faced by emperor penguins.
To breed, the species needs to remain for much of the year on stable sea ice near the land, known as fast ice.
But that critical breeding habitat is undergoing rapid change.
"Many regions of multi-year fast ice are now transitioning to seasonal fast ice, and this shift is expected to continue with potential for extinction of emperor penguins by 2100," the report states.
There are about 60 colonies of emperor penguins across the Antarctic coast.
But since 2016, 30 of them have experienced increased or complete breeding failure due to early fast-ice loss, the report says.
Sixteen of the colonies have suffered two or more such events during that time.
The report says other species also depend on sea ice and fast ice for breeding, including different types of seals, krill and Antarctic silverfish.
"The observed impacts highlight the potential for reduced survival capacity of some Antarctic ice-dependent species under the current regime shift in the Antarctic Sea ice and expected ongoing future climate changes."
Dr Barbara Wienecke, a senior research scientist at the AAD, said the situation was grim.
"The long-term consequences for emperor penguins are not looking good," Dr Wienecke told the ABC.
Professor Abram said the report's findings highlight the need to reduce carbon emissions.
"The changes that we're seeing in Antarctica and the Southern Ocean really reinforce the importance of these international agreements that we have for how we're going to tackle climate change," she said.