A massive ice shelf the size of New York City or Rome has completely collapsed in East Antarctica.
Satellite images posted to social media late last week show the 1,200-square-kilometre Conger ice shelf collapsed on or around March 15.
The collapse seems to have coincided with an extreme heatwave that saw parts of Antarctica experience temperatures 40 degrees Celsius above their monthly averages and records broken at several locations earlier this month.
NASA earth scientist Catherine Colello Walker tweeted images of the collapse on March 25, and said it was one of the most significant events in Antarctica since the Larsen B ice shelf collapsed in 2002.
The Larsen B ice shelf off the Antarctic Peninsula in West Antarctica covered around 3,250 square kilometres.
"[It's] possible it hit its tipping point following the Antarctic atmospheric river and heatwave too?" Dr Colello Walker said alongside the post.
More research will be needed to determine whether the recent heatwave was directly related to the collapse, but Matt King, who is the director of the Australian Centre for Excellence in Antarctic Science at the University of Tasmania, says it could have been one factor.
"We don't know [what impact the heatwave had] and that's something to dig into further," Professor King said.
"What is clear is that this area had been retreating since the 1970s.
Ice shelf collapse like releasing handbrake
Attached to land ice sheets and glaciers, ice shelves are the floating protrusion of ice that extends seaward from the coast.
The collapse of ice shelves themselves has little direct impact in terms of sea-level rise, Professor King said.
"[Ice shelves] are already floating, so their break-up doesn't do anything much other than cool the ocean down," he said.
But it's the destabilisation of land ice following a collapse where scientists focus their attention.
Ice shelves are described as the "safety belts" on the oceanic margins of Antarctica.
They work to hold back the advance of glaciers toward the ocean, according to Ben Galton-Fenzi, a glaciologist and senior scientist with the Australian Antarctic Division.
"Ice shelves play what's called a buttressing role," Dr Galton-Fenzi said.
"What that means is that there's friction between the glacier and the side walls, and the glacier and the bed."
When an ice shelf goes, that can act like releasing the handbrake on that land ice, allowing it to accelerate towards the ocean.
"The Larsen ice shelf is a classic example [where] there was a 4 per cent increase in sea level rise in the year after it collapsed," Dr Galton-Fenzi said.
Sea level rise will not be as much of an issue if the Conger ice shelf collapses, Professor King said.
"That's not as big a deal here because there's not as much ice sitting behind it on the land," he said.
"It will still be scientifically interesting to watch and we'll learn new things from it, but it's not going to flood New York City any time soon."
Antarctica melting still unpredictable
But the event is a worrying sign as East Antarctica is considered the "highest, driest, coldest region" on the continent, glaciologist and climate scientist Peter Neff explained in a video posted to TikTok.
The event is a reminder of the unknowns in predicting how fast sea-level may rise in future, according to Professor King.
Large punctuated events like this, especially if they happen in parts of Antarctica where an ice shelf is helping hold back large amounts of ice, can throw out projections.
"This is the first time we've seen an [East Antarctic] ice shelf disintegrate away," he said.
"It's a good reminder that the East Antarctic could change dramatically and quickly, and there are key areas we need to understand better."
One of those factors is called gravitational self-attraction, according to Dr Galton-Fenzi.
In short, everything with mass has gravity, and the greater the mass, the greater the gravitational force.
The shrinking of the Greenland and Antarctic ice sheets will see their masses greatly diminished.
"When they start to shrink, they don't pull the water up to them as much as they did before," Dr Galton-Fenzi said.
Instead, that sea-level rise will push further away from the poles, he said.
"The estimated sea-level rise in the latest IPCC report is [as much as 1.1 metres] by 2100, but we'd expect double that around Australia and the Pacific islands."
Professor King says we're yet to see warming really ramp up the rate of melting in Antarctica, but it's only a matter of time before we start seeing it.
"If you look in the Arctic, you see degrees of warming and dramatic sea ice retreat," he said.
"Antarctica hasn't seen that yet, but it's going to come to us. The question of how much and how soon is down to how well we can mitigate carbon emissions."
