- Written by Georgina Ranard, Becky Dale, Erwan Riveaux
- BBC News Climate, Science and Data Journalism Team
Satellite data shows sea ice surrounding Antarctica is well below winter levels ever recorded, an alarming new benchmark for a region once thought to be resilient to global warming. .
“It’s so far removed from anything we’ve seen before that it’s almost mind-boggling,” said Walter Meyer, who monitors sea ice at the National Snow and Ice Data Center.
An unstable Antarctic could have far-reaching implications, polar experts have warned.
Antarctica’s huge expanse of ice regulates Earth’s temperature because its white surface reflects the sun’s energy back into the atmosphere, cooling the water beneath and nearby.
Without ice to cool the planet, Antarctica could turn from a refrigerator to a radiator for the planet, experts say.
There is now less than 17 million square kilometers of ice on the surface of the Southern Ocean, which is 1.5 million square kilometers less than the September average and well below the previous winter record low.
This is equivalent to an area approximately five times the size of the British Isles being lost.
Dr. Meyer is not optimistic that sea ice will recover significantly.
Scientists are still trying to determine all the factors that led to this year’s sea ice loss, but studying trends in Antarctica has historically been difficult.
“It shows how vulnerable it is,” says Dr. Robbie Mallett of the University of Manitoba, who is based on the Antarctic Peninsula.
Already enduring isolation, frigid temperatures and high winds, thinner sea ice this year has made the team’s job even more difficult. “There’s a risk it could break and end up adrift at sea with us on board,” Dr Mallett said.
Sea ice forms during the continental winter (March to October) and mostly melts in the summer. Sea ice is also part of an interconnected system of icebergs, land ice, and giant ice shelves, which are floating extensions of land ice that protrude from the coast.
Sea ice protects the ice that covers land and prevents ocean temperatures from rising.
Dr Caroline Holmes from the British Antarctic Survey said the effects of shrinking sea ice could become apparent as the season moves into summer, with the potential for an unstoppable feedback loop of ice melting at this time of year. It is explained that there is.
As sea ice continues to disappear, dark areas of the ocean are exposed, absorbing sunlight instead of reflecting it. This means that heat energy is added to the water, causing more ice to melt. Scientists call this the ice albedo effect.
That could add more heat to Earth and disrupt Antarctica’s normal role in regulating Earth’s temperature.
“Are we awakening this Antarctic giant?” asks Professor Martin Siegert, a glaciologist at the University of Exeter. It would be an “absolute disaster for the world,” he says.
Professor Anna Hogg, a geoscientist at the University of Leeds, said there were signs that what was already happening to the Antarctic ice sheet was within the worst-case scenario forecast.
Even small increases in sea levels can cause dangerously high storm surges that can devastate coastal communities. If large amounts of land ice begin to melt, the effects will be devastating for millions of people around the world.
“I never thought that extreme weather would occur there.”
A self-contained continent surrounded by water, Antarctica has its own weather and climate system. Until 2016, Antarctic winter sea ice actually continued to expand.
However, in March 2022, an extreme heatwave hit East Antarctica, sending temperatures that should have been close to -50C to -10C.
“When I started researching Antarctica 30 years ago, I never imagined that extreme weather would occur there,” says Professor Siegert.
There are still many unknowns about Antarctica due to its remoteness and lack of historical information.
According to Dr Robbie Mallett, the region remains scientifically the “wild west”.
Scientists know how far sea ice extends, but they don’t know, for example, how thick it is. Solving that puzzle could fundamentally change climate models for the region.
At Science Station Rothera, Dr. Mallet uses radar equipment to study sea ice thickness for an international research project called Defiant.
He and other scientists are still working to understand why the winter ice disappears.
“It can be a highly unusual expression of natural variability,” he says, meaning many natural factors can be accumulating and affecting the area at the same time. Masu.
This year’s record warming temperatures are likely to blame, and scientists suggest that warm water will not freeze.
There may also have been changes in ocean currents and winds that could be warming Antarctica.
Although the El Niño phenomenon currently underway in the Pacific Ocean is still weak, it may be subtly contributing to the shrinkage of sea ice.
Dr. Mallett said: “There is good reason to be concerned.”
“This could be a really worrying sign of climate change in Antarctica that hasn’t been present for the past 40 years, and it’s only now becoming apparent.”