by It’s morning lifting in the Antarctic summer. It’s 7.30am and Nerilie Abram, professor of climate science at the Australian National University, is having breakfast at Casey station when she takes Guardian Australia’s call in late November. The sun barely kissed the sky the night before, and it won’t set for weeks.
The constant daylight can be disorienting to first-time visitors to Antarctica, but to seasoned explorers like Abram, it’s just the backdrop to life at the end of the Earth. This year, however, there is something else very strange.
When Abram was here ten years ago there was a mass of ice floating off the coast. It is a much changed scene when she looks out the window now. “There is no sea ice at all,” she says. “It’s a wonderful landscape. To think about what we’re doing for him and the changes that are happening here, it’s amazing.”
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That punch has galvanized scientists and policymakers around the world this year. As the hottest year on record nears its finish line, they are asking: Will 2023 be the year humanity leaves its stamp on Antarctica in ways that will be felt for centuries to come?
The southern continent has undergone major changes that immediately raise serious concerns about its health. They coincided with evidence that longer-term transformations associated with the climate crisis had begun much earlier than thought likely.
The changes have consequences for local wildlife, and also for people around the world in ways that are often not well understood.
Catalog of concerns
Antarctic sea ice cover fell for six months straight, to a level so far below anything else in the satellite record that scientists were struggling for adjectives to describe what they were seeing.
Although the full effect has yet to be documented, a peer-reviewed paper in August offered some insight into what it might entail. Examining satellite images, researchers from the British Antarctic Survey found that a record-breaking drop in sea ice in late 2022 – ahead of a bigger slump this year – could kill thousands of emperor penguin chicks. The normally stable sea ice that colonies rely on to raise their young in the Bellingshausen Sea was not stable, resulting in a “catastrophic breeding failure”.
That event happened in the west of the continent after parts of the east – the coldest place on earth – last year recorded what scientists believe is the biggest heatwave ever recorded, with temperatures peaking at 39C above the normal levels.
Looking ahead, a study published in Nature in March found that meltwater from continental ice sheets could significantly slow the Southern Ocean’s overturning circulation, a deep ocean current, by 2050 if greenhouse gas emissions continue to the current level. Two months later, a paper by some of the same researchers estimated that the circulation, which influences global weather patterns and ocean temperatures and nutrient levels, had already slowed by about 30% since the 1990s.
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Separate research by another team of scientists suggested that the accelerated melting of the ice shelves extending over the Amundsen Sea in western Antarctica is locked in and beyond human control for the rest of this century even if emissions are reduced significantly.
The new element here is the speed of melting – a threefold increase compared to the last century. Previous studies have already found that the entire west Antarctic ice sheet, which is protected by ice shelves and would raise global sea levels by five meters if completely lost, could be at risk of collapse in the long term.
Australian Center of Excellence in Antarctic Science Matt King says it was a year “even the scientists sobered up”.
“It’s not often in my career that scientists are really happy with what they see, but people are really scared. He caught them off guard,” he says. “We knew a significant change was coming, but we’ve seen processes that we thought might be mid-century much earlier.”
The link appears to be broken
The fall in the floating ice was very sudden. In mid-winter, the frozen part of the Southern Ocean was about 2.5m square kilometers less than the 40-year average. That is an area slightly larger than western Europe.
Scientists are cautious by nature, and have said it is still open to debate whether this change is primarily attributable to global warming caused by the burning of fossil fuels and deforestation. But it is clear that the air is warming and that the oceans absorb most of the heat trapped by increased greenhouse gases.
A study conducted by Australian researchers in September found hemispheric wind patterns this year and would normally be associated with above-average sea ice cover. They concluded that the link appears to be broken, probably due to ocean warming between 100 and 200 meters below the surface.
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Experts have different ways of describing the decline of sea ice. Tony Press, former head of the Australian Antarctic Division, says it is “not statistically predictable”.
What does that mean? “There’s a chance that it will come back, but there’s also a very high chance that Antarctic sea ice has moved into a new state,” says Press. “You wouldn’t be alarmist if you said you were very worried about that.”
Researchers say a permanent decline in sea ice is likely to accelerate ocean warming, as dark water absorbs more heat than ice and will increase the rate of global sea level rise by removing a buffer that protects continental ice shelves . It will also have an immediate impact on the species that depend on it for food, breeding and shelter – not just penguins but krill, fish and seals.
Press, now an assistant professor at the University of Tasmania, says the other changes should be seen as “awakening a sleeping giant” that will reverberate around the world. He describes the evidence of a slowdown and possible collapse in the Southern Ocean overturning circulation, in particular, as a “wake up call”.
The overturning circulation originates from the cold and dense waters more than 4,000 meters down from the Antarctic continental shelf. It spreads to ocean basins around the world, bringing oxygen to the depths and nutrients to the surface. Australian scientists found fresh water from melting Antarctic glacial ice was already reducing the density of the water and slowing the circulation.
Matt England, an oceanographer at the University of New South Wales and co-author of the two overturning circulation studies, says the slowdown could take effect over centuries, affecting heat, oxygen, nutrients and carbon stores, but most he was worried about the next one. a few decades.
‘Unbelievable geopolitical consequences’
Press says the potential consequences are far-reaching. Build fish populations. “The world depends on fisheries for protein and nutrition. If fisheries move north and south of the equator, where almost everyone in the world lives, there will be incredible geopolitical consequences,” he says.
Many scientists emphasize the need for leaders to understand the global impact of what is happening and the scale of work and funding that will be needed to understand it.
Kaitlin Naughten, a British Antarctic Survey ocean modeler who led the research into the inevitable increased melting of the west Antarctic ice shelves, says, “just because Antarctica is remote and uninhabited doesn’t mean it won’t bother you”.
She emphasizes that she does not want to “perpetuate the doom story”. A reduction in fossil fuels may not save the West Antarctic ice sheet, but other climate impacts can be avoided through decisive action. “East Antarctica and West Antarctica have about 10 times the volume of ice, and we think it’s generally stable and likely to remain that way as long as emissions don’t rise much more,” she says.
This is how Abram is spending the summer examining. In November, she was preparing to travel about 500km to drill an ice core from the Denman glacier. The goal is to see how the climate has been over the past 1,000 years compared to today.
The Denman glacier is part of the vast east Antarctic ice sheet, which scientists until a few years ago thought was largely immune to global warming. As Naughten says, if the world can get fossil fuels under control, it is likely to be largely stable.
But on the Denman glacier, at least, there are “worrisome signs”. “The rise of the ice sheet is decreasing,” says Abram. “There are signs that it is losing ice and contributing to sea level rise.”
If this plays out – one more thing to worry about in Antarctica – Matt England can relate.
“You look at the results and it’s really superficial,” he says. “For me, I hope 2023 is the year when all questions about the urgency of this problem are gone.”
