A building in the morning in Antarctic summer. It’s 7.30am and Nerilie Abram, a professor of climate science at the Australian National University, is eating breakfast at Casey station when she gets the call from Guardian Australia in late November. The sun barely kissed the horizon the night before and won’t drop below it for weeks.
Constant daylight can be confusing for first-time visitors to Antarctica, but for experienced researchers like Abram, it’s just the backdrop to life at the end of the Earth. But there is something else that is very strange this year.
When Abram was here ten years ago there was a block of ice floating on the shore. Now when you look out the window, there is a much changed scene. “There is no ice in the sea,” he says. “It’s an amazing sight. It’s a gut punch to think about what we’re doing about it and the changes that are happening here.”
Relating to: The Whole Story Reexamined: Where did Antarctic sea ice go? – digital audio file
That punch shook scientists and policymakers around the planet this year. As the hottest year on record approaches the finish line, they ask the question: Will 2023 be the year humanity leaves its mark on Antarctica in a way that will be felt for centuries?
The southern continent has experienced dramatic changes that have raised serious concerns about the health emergency. These dovetail with evidence that long-term transformations linked to the climate crisis are likely starting much earlier than assumed.
While the changes have consequences for local wildlife, they also have often less well-understood consequences for people around the world.
An alarming catalog
Sea ice cover in Antarctica collapsed over the course of six months to levels far below any in satellite records, and scientists struggled to find adjectives to describe what they witnessed.
While the full impact has not yet been documented, a peer-reviewed paper in August provided some insight into what it might mean. Analyzing satellite images, researchers from the British Antarctic Survey found that a record decline in sea ice in late 2022 (before a larger decline this year) may have killed thousands of emperor penguin chicks. In the Bellingshausen Sea, the usually stable sea ice that colonies use to raise their young was not there, possibly causing a “catastrophic reproductive failure.”
This event in the west of the continent followed parts of the east (the coldest place on Earth) last year, recording what scientists think is the largest heatwave ever recorded; temperatures rose to 39°C above normal.
Looking ahead, a study published in March in the journal Nature found that if greenhouse gas emissions continue at their current levels, meltwater from the continent’s ice sheets could significantly slow the circulation of a deep ocean current that disrupts the circulation of the Southern Ocean by 2050. Two months later, a paper by some of the same researchers estimated that circulation, which affects global weather, ocean temperatures and nutrient levels, had slowed by about 30% since the 1990s.
Relating to: ‘We lost control’: What happens when the West Antarctic ice sheet melts? – digital audio file
A separate study by a different team of scientists suggested that the rapid melting of ice shelves along the Amundsen Sea in West Antarctica remains within and beyond human control for the rest of this century, even as emissions are significantly reduced.
The new element here is the melting rate, which has tripled compared to the last century. Previous studies have already found that the entire West Antarctic ice sheet, which is protected by ice shelves and whose complete disappearance would raise global sea levels by five meters, may be doomed to collapse in the much longer term.
Matt King of the Australian Antarctic Science Center of Excellence says this has been a year “even scientists have been sobering up”.
“It’s not often in my career that scientists are stunned by what they see, but people were genuinely alarmed. “He caught them on the jump,” he says. “We knew significant change was coming, but we found that processes we thought might occur by mid-century would occur much sooner.”
The link seems broken
The decline in floating ice was particularly abrupt. At midwinter, the frozen portion of the Southern Ocean was about 2.5 million square kilometers less than the 40-year average. This is an area slightly larger than Western Europe.
Scientists are inherently cautious and emphasized that it is open to debate whether this change can be attributed mainly to global warming caused by the burning of fossil fuels and deforestation. However, it is clear that the weather is warming and most of the heat trapped by increasing greenhouse gases is being absorbed by the oceans.
A September study by Australian researchers found that hemispheric wind patterns this year and last were generally associated with above-average sea ice cover. They concluded that the connection appeared to have been lost, possibly due to warming of the ocean 100 to 200 meters below the surface.
Relating to: We cannot survive on Earth without the Southern Ocean. Our research must wait no longer | Nathan Bindoff
Experts have different ways to explain the decline in sea ice. Tony Press, former head of the Australian Antarctic Division, says this is “not statistically predictable”.
What does this mean? “There’s a chance it will come back again, but there’s also a very, very high chance that sea ice in Antarctica will transition to a new state,” Press says. “If you said you were really worried about this you wouldn’t be alarmed.”
A permanent decline in sea ice would likely accelerate ocean warming because dark water absorbs more heat from ice and removes the buffer that protects the continent’s ice shelves, increasing the rate of global sea level rise, researchers say. It will also have an immediate impact not only on penguins but also on species that depend on it for food, reproduction and shelter, such as krill, fish and seals.
Press, now an adjunct professor at the University of Tasmania, says this, among other changes, should be seen as “the awakening of a sleeping giant” that will reverberate globally. He describes the evidence of a slowdown and potential collapse that would disrupt circulation, particularly in the Southern Ocean, as a “wake-up call”.
The overturning circulation is caused by cold, dense waters 4,000 meters below the Antarctic continental shelf. It spreads globally to ocean basins, bringing oxygen to the depths and nutrients to the surface. Australian scientists have found that freshwater from melting glacier ice in Antarctica has already reduced water density and slowed circulation.
Matt England, an oceanographer at the University of New South Wales and co-author of two reversal circulation studies, says the slowdown could last for centuries, affecting heat, oxygen, nutrients and carbon stores, but he is most concerned about what comes next. several decades.
‘Incredible geopolitical consequences’
The potential consequences are far-reaching, the press says. Take fish populations. “The world relies on fishing for protein and livelihood. “If fishing shifts north and south from the equator, where nearly all people on Earth live, that would have incredible geopolitical consequences,” he says.
Many scholars emphasize that leaders need to understand the global impact of what is happening and the extent of work and funding that will be needed to understand it.
“Just because Antarctica is so remote and isolated doesn’t mean it won’t affect you,” says Kaitlin Naughten, an ocean modeler with the British Antarctic Survey who is leading research on the inevitable increasing melting of West Antarctic ice shelves.
He emphasizes that he does not want to “feed the apocalypse narrative.” Reducing fossil fuels may not save the West Antarctic ice sheet, but other climate impacts can be prevented with decisive action. “East Antarctica has about 10 times the volume of ice as West Antarctica, and we think that’s generally stable and will likely stay that way unless emissions increase further,” he says.
This is what Abram spent the summer studying. In November, he was preparing to travel nearly 500 km to extract an ice core from the Denman glacier. The aim is to see how the climate of the past 1,000 years compares to today.
The Denman glacier is part of the massive east Antarctic ice sheet, which until a few years ago scientists thought was largely unaffected by global warming. If the world can get fossil fuels under control, this situation is likely to remain mostly stable, Naughten says.
But at least there are “worrying signs” on the Denman glacier. “The height of the ice sheet is decreasing,” says Abram. “There are signs that it is losing ice and contributing to sea level rise.”
If that sounds overwhelming (one more thing to worry about in Antarctica), Matt England can understand.
“You look at the results and it’s really confronting,” he says. “For me, I hope that 2023 will be the year when all questions about the urgency of this problem disappear.”