Far to the south, where the sea freezes and thaws in slow rhythms older than any human record, the ice that girdles Antarctica has reached a low that satellites have never before witnessed. A review published this week in Frontiers in Environmental Science gathers the evidence and concludes that a warming world is leaving the continent more exposed to heatwaves, ice shelf collapse and the thinning of its frozen cover, and that these shocks are likely to grow in size and frequency. The scientists who speak in the study do not promise a return to what was; they describe a sea ice cover that may
No Quick Fix for Antarctic Sea Ice Loss as Warming Pushes Record Lows, Scientists Warn
Decades if not centuries for these things to recover
Mark
Sea ice has hit a record low again. Why does a second record in two years matter?
Mimi
Because of the threshold. Last year the summer minimum went below 2 million square kilometres for the first time since satellite monitoring began in 1978. This February it went lower still. That's a pattern, not a one-off.
Mark
How big is the loss, in plain terms?
Mimi
Tim Naish says this year's minimum is 20% below the 40-year average, which he equates to nearly ten times the area of New Zealand.
Luke
Worth noting Naish wasn't part of the study. That comparison is his framing, not the paper's headline finding.
Mark
Holmes says recovery could take decades or centuries. How firm is that?
Luke
It's her judgment at a briefing, and she hedged it: even if recovery is possible. It's not a modelled timeline we've been shown.
Mimi
Still, it's a clear message that nobody is expecting a quick rebound.
Mark
And the heat event last year?
Mimi
An atmospheric river from Australia brought temperatures up to 38.5 Celsius above normal. The study calls it the biggest variance from the norm the world has seen. It happened in winter, so there was no surface melt. Siegert says a summer event would have melted the East Antarctic ice sheet's surface.
Luke
That's a hypothetical, though. It didn't happen. And the report admits scientists have struggled to measure how warming affects ice thickness, so the link to individual events is reasoned, not proven. Siegert's own wording is that it's scientifically reasonable to expect intensification.
Mark
What about the tipping points?
Luke
Naish says in some cases we're getting close. The article doesn't say which systems or how close, so that remains unknown.
Il Polso
- Antarctic summer sea ice dropped below two million square kilometres for the first time since satellites began watching in 1978, and then fell lower still in February.
- This year's minimum sits roughly 20 percent beneath the 40-year average, a loss close to ten times the area of New Zealand.
- A single atmospheric river from Australia drove temperatures as much as 38.5 degrees Celsius above normal, the largest departure from the norm the study says the world has ever recorded.
- Researchers warn that heatwaves and ice shelf collapses will intensify, and some parts of the system may be nearing tipping points that cannot be reversed.
- Recovery, scientists say, is measured in decades or centuries, and the next Antarctic summer will reveal how far the decline has already gone.
Far to the south, where the sea freezes and thaws in slow rhythms older than any human record, the ice that girdles Antarctica has reached a low that satellites have never before witnessed. A review published this week in Frontiers in Environmental Science gathers the evidence and concludes that a warming world is leaving the continent more exposed to heatwaves, ice shelf collapse and the thinning of its frozen cover, and that these shocks are likely to grow in size and frequency. The scientists who speak in the study do not promise a return to what was; they describe a sea ice cover that may take decades or centuries to mend, if it mends at all, and they ask us to notice how much of the planet's future is held in this distant, fragile white.
The number that anchors this story is two million square kilometres. Last year, the summer sea ice around Antarctica sank below that line for the first time since satellites began measuring the continent in 1978. In February, it dropped further, to a new record low.
A study published in Frontiers in Environmental Science draws together evidence from the Antarctic ocean, atmosphere, ice and living systems. Its core message is that fossil-fuel warming has made Antarctica more vulnerable, and that the damage from heatwaves, ice shelf collapses and sea ice loss is virtually certain to worsen. Caroline Holmes of the British Antarctic Survey, a co-author, told reporters there is no quick repair: recovery could take decades, perhaps centuries, and may never fully arrive.
Tim Naish of Victoria University of Wellington, who was not involved in the study, offered a sense of scale. This year's minimum lies about 20 percent below the 40-year average, a loss nearly ten times the size of New Zealand. Some parts of the system, he warned, are approaching tipping points that, once passed, could trigger changes no one can stop.
Not everything is certain. Scientists still struggle to pin down exactly how climate change is reshaping Antarctica and its surrounding waters, and how much the ice sheet's thickness is changing. Still, co-author Martin Siegert of the University of Exeter argued that the sea ice decline alone makes it reasonable to expect extreme events to grow as the planet warms. Last year offered a stark example: an atmospheric river from Australia pushed subtropical heat deep into the continent, lifting temperatures to as much as 38.5 degrees above normal. Because it arrived in winter, it caused no surface melt, but a summer event could have begun melting the East Antarctic ice sheet, which has so far escaped.
"Antarctica is fragile as an environment, but extreme events test that fragility," Siegert said. The worry, he added, lies in the rising intensity and frequency of such shocks and in the cascading effects they set off elsewhere. As the next Antarctic summer approaches, these are the signals to watch.
The number that frames this story is two million square kilometres. Last year, the minimum summer sea ice cover around Antarctica dropped below that line for the first time since satellites began watching the continent in 1978. In February of this year, it fell lower still, setting a new record.
The finding comes from a study published on August 8 in the journal Frontiers in Environmental Science, which reviews recent evidence from studies of the Antarctic ocean, atmosphere, cryosphere and biosphere. Its central conclusion is that global warming, driven by the burning of fossil fuels, has left Antarctica more vulnerable to extreme events, and that the impact is "virtually certain" to get worse. Climate change, the authors write, will increase both the size and the frequency of heatwaves, ice shelf collapses and sea ice declines.
Caroline Holmes, a polar climate scientist at the British Antarctic Survey and a co-author, told a briefing with journalists that there is no quick way to put the ice back. Recovery, she said, will take decades if not centuries, and it will take a long time even if it proves possible at all.
Tim Naish, director of the Antarctic Research Centre at Victoria University of Wellington in New Zealand, did not take part in the study but put the scale in terms of area. This year's sea ice minimum is 20% below the average of the past 40 years, he said, a loss equal to nearly ten times the area of New Zealand. He added that in some cases the system is nearing tipping points, which once crossed lead to irreversible changes with unstoppable consequences for future generations.
The science is not settled on everything. The precise effect of climate change on Antarctica and the surrounding ocean has been uncertain, and researchers have struggled to measure how much global warming is changing the thickness of Antarctic ice. Martin Siegert, a glaciologist at the University of Exeter and another co-author, argued that the rapid decline in sea ice is enough to make it "scientifically reasonable" to expect extreme events to intensify as global temperatures rise.
He pointed to an episode last year as an example. An atmospheric river originating from Australia pushed subtropical heat and moisture into the continent, producing temperatures as much as 38.5 degrees Celsius (69.3 Fahrenheit) above normal. The study describes that as the largest departure from the norm the world has ever experienced. Siegert called it "absolutely astonishing." Because it struck in the Antarctic winter, it did not cause surface melting. Had it come in summer, he said, it would have triggered melt on the surface of the East Antarctic ice sheet, which has so far been spared.
"Antarctica is fragile as an environment, but extreme events test that fragility," Siegert said. What worries scientists most, he added, is the growing intensity and frequency of such events and the cascading effects they have in other areas.
The record low in February, the study's warnings about heatwaves and ice shelf collapses, and the open question of how close the system sits to its tipping points are what to watch as the next Antarctic summer approaches.
Citazioni salienti
It's going to take decades if not centuries for these things to recover. There's no quick fix to replacing this ice.— Caroline Holmes, British Antarctic Survey
Antarctica is fragile as an environment, but extreme events test that fragility.— Martin Siegert, University of Exeter
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Climate & Environment