In a study published in Nature, a team led by Nerilie Abram suggests that the shrinking of Antarctic sea ice may have crossed into a new and possibly irreversible state, the kind of threshold that reshapes the whole planet rather than a single corner of it. The ice that once girdled the southern continent is now far smaller than anything the past several centuries would have led us to expect, and its retreat seems to feed on itself. What it means, in the long human story of this planet, is that the bottom of the world may be quietly rewriting the terms on which oceans, wildlife and the air its
Rapid Antarctic Sea Ice Loss May Be a Climate Tipping Point, Scientists Warn
Even if we stabilise the climate, we are committed to still losing Antarctic sea ice
Mark
What's actually new in this paper? We've heard that sea ice is shrinking for years.
Mimi
It's the scale of the comparison. The authors combined observations, ice cores and ship logbooks to look back across centuries, and they say the recent drop sits far below natural variability over that span.
Mark
And they call it a regime shift.
Mimi
Yes, and they say in some respects it's more abrupt and potentially irreversible than the Arctic loss. That's a notable contrast, since the Arctic usually gets the attention.
Luke
Let me slow that down. "May be a tipping point" is the study's framing, and the lead author says "may actually be." That's not the same as a confirmed threshold being crossed.
Mark
Fair. So what is firmly described?
Mimi
The mechanisms: less ice reflects less sunlight, the Antarctic Overturning Circulation will probably weaken, penguins and krill are being harmed, and phytoplankton that absorb carbon are expected to decline.
Luke
Note the wording, though. "Probably" weaken, and "will further reduce" phytoplankton is a projection. The harm to wildlife is described as increasing, but the report gives no numbers.
Mark
What about the centuries claim?
Mimi
Abram says that even if the climate is stabilised, loss continues for many centuries. That's her statement of the study's conclusion about commitment.
Luke
And it's one study, reported through a wire summary. I'd want to know how other researchers respond before treating the irreversibility as settled.
Mark
So emissions cuts still matter?
Mimi
The paper says they'd reduce the risk of major changes, even if they may not prevent them.
Il Polso
- A new Nature study warns that Antarctic sea ice has fallen far below anything seen in centuries, pushing the system into an unfamiliar regime.
- Less ice means less sunlight reflected back to space, so the ocean absorbs more heat and the ice loss accelerates itself.
- Emperor penguins that breed on the ice and the krill that feed beneath it are already suffering as their habitat disappears.
- Researchers warn that the weakening of the Antarctic Overturning Circulation and falling phytoplankton could cut carbon uptake and reshape global currents.
- Even if emissions are curbed and the climate stabilises, scientists say the loss may continue for centuries, leaving little room for quick reversal.
In a study published in Nature, a team led by Nerilie Abram suggests that the shrinking of Antarctic sea ice may have crossed into a new and possibly irreversible state, the kind of threshold that reshapes the whole planet rather than a single corner of it. The ice that once girdled the southern continent is now far smaller than anything the past several centuries would have led us to expect, and its retreat seems to feed on itself. What it means, in the long human story of this planet, is that the bottom of the world may be quietly rewriting the terms on which oceans, wildlife and the air itself keep their balance.
A paper published in Nature this week makes a sobering claim about Antarctica: the rapid loss of sea ice there may be a tipping point for the global climate, with effects that could include rising seas, altered ocean currents and the decline of marine life, and some of these may not be reversible.
The study drew on modern satellite observations, ice cores and historical ship logbooks to place recent decline against a far longer record. Its central finding is that Antarctic sea-ice extent has shifted into a new regime, well outside the natural variability of past centuries. The authors argue the change is more abrupt and potentially irreversible than what has been seen in the Arctic, with interacting processes that can sustain themselves.
Nerilie Abram, the lead author and now chief scientist at the Australian Antarctic Division, described how the pieces feed one another. Less ice reflects less sunlight, so more heat is absorbed, which is likely to weaken the Antarctic Overturning Circulation, the vast ocean current that moves heat and nutrients around the globe. Wildlife is already paying the price: emperor penguins breed on the ice and krill feed beneath it, and both are increasingly harmed. Warmer surface waters also threaten phytoplankton, which pull large amounts of carbon from the air.
"Antarctic sea ice may actually be one of those tipping points in the Earth's system," Abram said, warning that once the decline begins, it becomes self-perpetuating.
The outlook offers little comfort. Cutting carbon emissions would lower the risk, the study says, but may not prevent the change. Even if the climate is stabilised, the loss of Antarctic sea ice is expected to continue for many centuries. The open question now is whether climate assessments will treat Antarctic ice as a distinct and possibly irreversible shift, rather than simply a counterpart to the Arctic.
A paper published in the journal Nature on Thursday makes a stark claim about the bottom of the world: the rapid loss of Antarctic sea ice may be a tipping point for the global climate, with consequences that include sea level rise, altered ocean currents and loss of marine life, none of which could be reversed.
The study set out to describe, in more detail than had been possible before, how the effects of global warming on the frozen continent interlock. Its authors drew on three kinds of evidence: modern observations, ice cores and ship logbooks. Together these let them chart long-term changes in the area covered by sea ice, and so set the steep declines of recent years against a much longer record.
That comparison is the core of the finding. According to the paper, a regime shift has pushed Antarctic sea-ice extent far below its natural variability of past centuries. In some respects, it says, the change is more abrupt, non-linear and potentially irreversible than the loss of sea ice in the Arctic. The authors write that evidence is emerging for rapid, interacting and sometimes self-perpetuating changes in the Antarctic environment.
Nerilie Abram, the study's lead author, stressed how the changes feed one another across the ecosystem. Abram is a former professor at the Australian National University and is now chief scientist at the Australian Antarctic Division. A smaller expanse of ice reflects less solar radiation, so the planet absorbs more heat. That, the study says, will probably speed the weakening of the Antarctic Overturning Circulation, an ocean-spanning current that distributes heat and nutrients and helps regulate weather.
Wildlife is already feeling the loss. Emperor penguins breed on the ice, and krill feed beneath it; both are increasingly harmed as the ice shrinks. The paper adds that warming surface water will further cut phytoplankton populations, which draw vast quantities of carbon out of the atmosphere. Less phytoplankton means less of that natural carbon removal.
Abram put the conclusion plainly. "Antarctic sea ice may actually be one of those tipping points in the Earth's system," she said. Once the ice starts disappearing, she explained, a self-perpetuating process begins.
The study offers only qualified comfort on emissions. Reining in global carbon dioxide output would reduce the risk of major changes in the Antarctic, it says, but may still not prevent them. Abram was more direct about the timescale: even if the climate is stabilised, she said, the world is committed to continued loss of Antarctic sea ice over many centuries to come.
What to watch is whether the finding changes how Antarctic sea ice is treated in climate assessments, given the paper's argument that its loss is a distinct and possibly irreversible shift rather than a mirror of the Arctic.
Citazioni salienti
Antarctic sea ice may actually be one of those tipping points in the Earth's system.— Nerilie Abram, lead author
Even if we stabilise the climate, we are committed to still losing Antarctic sea ice over many centuries to come.— Nerilie Abram, lead author
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Climate & Environment