by The morning is a construction in the Antarctic summer. It’s 7.30am and Nerilie Abram, professor of climate sciences 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 horizon last night and won’t fall below it for weeks.
Constant daylight may be disconcerting to first-time visitors to Antarctica, but for experienced researchers like Abram, it’s just the backdrop for life at the end of the Earth. This year, however, there is something more profoundly strange.
When Abram was here a decade ago, there was a mass of ice floating off the coast. It’s a very altered scene as he now looks out the window. “There’s no sea ice,” he says. “It is a magnificent landscape. “To think about what we are doing to it and the changes that are taking place here is a punch in the stomach.”
Related: Full History Revised: Where Did All the Antarctic Sea Ice Go? – podcast
That blow has left scientists and policymakers around the planet breathless this year. As the hottest year on record nears its mark, they’ve been wondering: Will 2023 be the year humanity leaves its mark on Antarctica in ways that will be felt for centuries to come?
The southern continent has undergone dramatic changes that raise serious concerns about its immediate health. They have coincided with evidence that the long-term transformations linked to the climate crisis have begun much earlier than was assumed likely.
The changes have ramifications for local wildlife, but also for people around the world in ways that are often not as well understood.
A catalog of concerns
Antarctica’s sea ice sheet plummeted for six months straight, to a level so below anything recorded by satellite that scientists struggled to find adjectives to describe what they were witnessing.
While the full effect has yet to be documented, a peer-reviewed paper published in August gave some insight into what it might mean. Examining satellite images, researchers from the British Antarctic Survey found that the record drop in sea ice in late 2022, before this year’s biggest drop, could have killed thousands of emperor penguin chicks. The normally stable sea ice that colonies depend on to raise their young in the Bellingshausen Sea simply wasn’t there, likely leading to “catastrophic reproductive failure.”
That event in the west of the continent followed parts of the east, the coldest place on Earth, where last year there was what scientists believe is the biggest heat wave ever recorded, with temperatures reaching a high of 39 °C above normal.
Looking ahead, a study published in Nature in March found that meltwater from the continent’s ice sheets could dramatically slow the Southern Ocean reversal circulation, a deep ocean current, by 2050 if greenhouse gas emissions greenhouse will continue at their 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 1970s. 1990.
Related: ‘We’ve lost control’: what will happen when the West Antarctic ice sheet melts? – podcast
Separate research by a different team of scientists suggested that accelerated melting of the ice shelves stretching over the Amundsen Sea in West Antarctica is locked in and out of human control for the rest of this century, even if emissions are significantly reduced.
The new element here is the rate of melting, which triples 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 doomed to collapse in a much longer time frame. .
Australian Center for Excellence in Antarctic Science Matt King says it has been a year in which “even scientists have become serious”.
“It’s not often in my career that scientists are really stunned by what they’re seeing, but people have been very alarmed. It caught them in the moment,” she says. “We knew that substantial changes were coming, but we have seen processes that we thought could develop by mid-century develop much sooner.”
The link seems broken
The fall of the floating ice was particularly abrupt. In the middle of winter, the frozen part of the Southern Ocean was about 2.5 million square kilometers smaller than the 40-year average. This is an area slightly larger than Western Europe.
Scientists are naturally cautious and have stressed that the debate remains open as to 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 most of the heat trapped by rising greenhouse gases is absorbed by the oceans.
A study by Australian researchers in September found that hemispheric wind patterns this year and last would normally have been associated with above-average sea ice cover. They concluded that the link appears to have been broken, probably due to warming of the ocean between 100 and 200 meters below the surface.
Related: Without the Southern Ocean we cannot survive on Earth. Our investigation should not wait any longer | Nathan Bindoff
Experts have different ways of describing the decline in sea ice. Tony Press, former head of the Australian Antarctic Division, says it is “statistically not predictable.”
What does that mean? “There is a possibility that it will reappear, but there is also a very, very high possibility that the Antarctic sea ice has moved to a new state,” Press says. “It wouldn’t be alarmist if he said he’s really worried about it.”
Researchers say a permanent decline in sea ice will likely accelerate ocean warming, as dark water absorbs more heat than ice and amplifies the rate of global sea level rise by removing a buffer that protects ice shelves. of the continent. It will also have an immediate impact on the species that depend on it for food, reproduction and shelter: not just penguins, but also krill, fish and seals.
Press, now an associate professor at the University of Tasmania, says that, along with other changes, it should be seen as the “awakening of a sleeping giant” that will resonate globally. He describes the evidence of a slowdown and possible collapse of the Southern Ocean circulation, in particular, as a “wake-up call.”
The inverted circulation originates in the cold, dense waters more than 4,000 meters deep off 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 that fresh water from melting Antarctic glacial ice was already reducing water density and slowing circulation.
Matt England, an oceanographer at the University of New South Wales and co-author of the two reverse circulation studies, says the slowdown could last for centuries and affect reserves of heat, oxygen, nutrients and carbon, but what worried him most was the next. Few decades.
‘Incredible geopolitical consequences’
Press says the potential ramifications are far-reaching. Take fish stocks as an example. “The world depends on fishing for protein and sustenance. If fisheries move north and south, away from the equator, where almost the entire world’s population lives, there will be incredible geopolitical consequences,” he says.
Many scientists emphasize the need for leaders to understand the global effect of what is happening and the scale of work and funding that will be needed to understand it.
Kaitlin Naughten, an ocean modeler at the British Antarctic Survey who led research into the inevitable increase in melting of the West Antarctic ice shelves, says “just because Antarctica is far away and uninhabited doesn’t mean it won’t affect you.” .
He emphasizes that he does not want to “feed the fatalistic narrative.” Reducing fossil fuels may not save the West Antarctic Ice Sheet, but other climate impacts can be avoided through decisive action. “East Antarctica has about 10 times the volume of ice as West Antarctica, and we think it’s generally stable and will probably stay that way as long as emissions don’t increase much further,” he says.
This is what Abram is examining over the summer. In November, he was preparing to travel about 500 kilometers to drill an ice core from the Denman Glacier. The objective is to compare the climate of the last 1,000 years with the current one.
The Denman Glacier is part of the massive East Antarctic Ice Sheet, which until a few years ago scientists had thought was largely immune to global warming. As Naughten says, it is still seen as likely to remain stable if the world can get a grip on fossil fuels.
But at least on the Denman Glacier there are “worrying signs.” “The elevation of the ice sheet is reducing,” says Abram. “There are signs that it is losing ice and contributing to sea level rise.”
If this sounds exhausting (one more thing to worry about in Antarctica), Matt England can relate.
“If you look at the results, it’s really confronting,” he says. “For me, I hope that 2023 is the year in which all doubts about the urgency of this problem disappear.”
