‘Catastrophic’: Huge update on world’s largest iceberg
There has been a huge update on the world’s largest iceberg, known as A23a, that could have ‘catastrophic’ consequences for Australia.
The world’s largest iceberg is falling apart and melting. And it is sign of things to come for the enormous ice sheets of Antarctica.
The implications are severe.
The Australian fishing industry. Australian agriculture. Australian droughts and floods. And every Australian capital city.
New research warns this accelerated melting is slashing plankton populations, slowing Antarctic currents, and beginning to impact global sea levels.
And the changes are potentially as enormous as a new fleet of icebergs.
“The potential for abrupt changes is far less understood in the Antarctic compared with the Arctic, but evidence is emerging for rapid, interacting and sometimes self-perpetuating changes in the Antarctic environment,” the Australian National University authors of a new Nature study report.
The researchers point to evidence suggesting the West Antarctic Ice Sheet is on the verge of collapse. And the East Antarctic Ice Sheet, located closer to Australia, is also showing signs of similar stress.
Study lead author Professor Nerilie Abram says such a collapse would produce “catastrophic consequences for generations to come”.
“Rapid change has already been detected across Antarctica’s ice, oceans and ecosystems, and this is set to worsen with every fraction of a degree of global warming,” Professor Abrams, now Chief Scientist at the Australian Antarctic Division, warns.
Orphaned ice
When the massive A32a iceberg first broke free of the Antarctic sea floor in 2023, it covered an area of about 3900 sq km.
Before July, it had shrunk to 2500 sq km, roughly the size of New York’s Rhode Island and Australia’s Capital Territory (ACT). Now, Australia’s Bureau of Meteorology (BoM) has discovered that it has fractured, with two chunks - measuring approximately 160 sq km and 73 sq km - now drifting off into the South Atlantic.
And there are plenty more to come.
The D15 ice sheet is currently grounded in east Antarctica’s Prydz Bay, off the western edge of the West Ice Shelf, after splitting from a land-based glacier. But the Florida-sized mass is also steadily fracturing, threatening to cast enormous chunks into the South Atlantic.
But the East Antarctic Ice Sheet is also thinning.
Pools of water can be seen sitting on the ice’s surface. This has been found to seep into cracks in the ice, further weakening the structure. It also pools beneath the ice sheet, acting as a lubricant between the glaciers and the rock.
Researchers now say this is causing Antarctica to melt faster than expected.
It is already recording sea-ice levels far below the natural variations seen in recent centuries.
“The loss of Antarctic sea ice is another abrupt change that has a whole range of knock-on effects, including making the floating ice shelves around Antarctica more susceptible to wave-driven collapse,” the ANU researchers said in a statement.
The most obvious sign is the northward march of the orphaned ice.
A23a grounded on the Filchner Ice Shelf near South Georgia Island earlier this year. Since then, satellite observations have revealed that it has been shedding thousands of ice chunks from its edges.
This is only expected to accelerate once it continues its northward drift. But its largest “calves” are already on the move, prompting concerns over nearby shipping routes.
“Icebergs that make it this far north are increasingly at the mercy of warm water, waves, and seasonal weather—factors that contribute to a berg’s ultimate demise,” explains a NASA statement.
Broken cycles
“The decline in Antarctic sea ice and the slowdown of deep circulation in the Southern Ocean are showing worrying signs of being more susceptible to a warming climate than previously thought,” the ANU researchers report.
“As sea ice is lost from the ocean surface, it is also changing the amount of solar heat being retained in the climate system, and that is expected to worsen warming in the Antarctic region”.
Water is darker than ice. Instead of reflecting solar heat back into space, it absorbs it.
And that heat enters Earth’s ecosystem.
“Other changes to the continent could soon become unstoppable, including the loss of Antarctic ice shelves and vulnerable parts of the Antarctic ice sheet that they hold behind them,” the statement adds.
Study co-author Professor Matthew England of the UNSW says the knock-on effects are severe.
“Consequences for Australia include rising sea levels that will impact our coastal communities, a warmer and deoxygenated Southern Ocean being less able to remove carbon dioxide from the atmosphere, leading to more intense warming in Australia and beyond, and increased regional warming from Antarctic sea ice loss,” Professor England said.
Evidence of this devastating cascade is already being seen, he adds. Entire colonies of emperor penguin chicks have died.
Broken ice is tipping them into the frigid sea before their waterproof feathers grow. And their parents are struggling to find enough krill to feed them.
“Another potential risk is a collapse in the Antarctic overturning circulation, which would mean vital nutrients remain at the sea floor, instead of being recirculated back to the surface where biological systems, including marine animals, depend on them,” Professor England adds.
That will have a flow-on effect on Southern Ocean fish populations.
Climate lurch
“While it’s common to assume incremental warming will translate to gradual change, we’re seeing something very different in Antarctica,” the study’s authors write in The Conversation.
“The Antarctic environment had a much more muted response overall to human-caused climate warming compared to the Arctic. But about a decade ago, abrupt changes began to occur.”
The study highlights the self-amplifying effect of melting. Retreating ice leaves more ocean surface to warm more rapidly.
This melts more ice, faster. It’s a cascade that began in 2014.
“The expanse of sea ice is now shrinking at double the rate of Arctic sea ice,” the researchers write. “We found these unfolding changes are unprecedented – far outside the natural variability of past centuries.”
This is affecting deep-sea currents (the Antarctic Overturning Circulation) which acts as a Southern Hemisphere airconditioning system.
It’s slowing. That means warm water stays on the surface for longer, which, in turn, intensifies weather patterns. And it’s slowing the rate at which carbon captured on the surface is injected into the deeps.
Antarctica stores more than 90 per cent of the planet’s land-based fresh water.
And that meltwater must go somewhere.
“These enormous ice sheets represent the risk of a global tipping point,” the ANU researchers conclude. “They contribute the greatest uncertainty to projections of future sea level rise because we don’t know just how quickly they could collapse.”
Jamie Seidel is a freelance writer | @jamieseidel.bsky.social
Originally published as ‘Catastrophic’: Huge update on world’s largest iceberg
