The “surprising” change in Antarctica that experts are concerned about

Sea ice around Antarctica is well below all previously measured winter levels, satellite data shows, a worrying new benchmark for a region that once seemed resilient to global warming.

“It’s so far removed from anything we’ve ever seen that it’s almost astonishing,” said Walter Meier, who monitors sea ice at the U.S. National Snow and Ice Data Center.

An unstable Antarctica could have far-reaching consequences, experts warn.

Antarctica’s vast expanse of ice regulates the planet’s temperature because its white surface reflects the sun’s energy back into the atmosphere and also cools the water beneath and next to it.

Without the planet-cooling ice, Antarctica could turn from Earth’s refrigerator into a radiator, experts say.

The ice floating on the surface of the Southern Ocean now measures less than 17 million square kilometers, or 1.5 million square kilometers of sea ice less than the September average and well below last winter’s record depths.

This is an area lacking ice and about five times the size of the British Isles.

An important measure

Walter Meier does not believe that the sea ice will recover to a large extent.

Scientists are still trying to identify all the factors that led to this year’s sea ice decline, but studying trends in Antarctica has historically been challenging.

In a year in which that has been the case several world heat records have been broken and ocean temperatures, some scientists argue that low sea ice is the metric to pay attention to.

“We can see how fragile it is,” said Dr. Robbie Mallet of the University of Manitoba, based on the Antarctic Peninsula.

This year’s thin sea ice, already dealing with insulation, extreme cold and high winds, has made his team’s task even more difficult.

“There is a risk that it will break and float out to sea with us at the top,” says Mallet.

Sea ice forms in the continent’s winter (March to October) before largely melting in summer, and is part of an interconnected system that also includes icebergs, land ice and huge ice shelves – floating ice sheets. .

Sea ice acts as a protective layer for the ice covering the land and prevents the ocean from warming.

The albedo effect

Dr. Caroline Holmes of the British Antarctic Survey explains that the consequences of reducing sea ice may become apparent as the season transitions into summer, when there is the potential for an unstoppable feedback loop of melting ice.

As more sea ice disappears, darker parts of the ocean are exposed absorb sunlight instead of reflecting itmeaning thermal energy is added to the water, causing more ice to melt.

Scientists call this the ice albedo effect.

That would add much more heat to the planetchanging Antarctica’s usual role as a regulator of global temperatures.

“We woke up this Antarctic giant?” asks Professor Martin Siegert, a glaciologist at the University of Exeter.

I would be “an absolute disaster for the world“, there stands that.

There are signs that what is already happening to the Antarctic ice sheets is predicting the worst, says Professor Anna Hogg, an earth scientist at the University of Leeds in the United Kingdom.

Since the 1990s, land ice loss in Antarctica has contributed 7.2 mm to sea level rise.

Even modest sea level rise can cause dangerously high storm surges that can wipe out coastal communities.

If large amounts of land ice were to begin to melt, the consequences would be catastrophic for millions of people around the world.

The ‘wild west’ of the scientific world

As a self-contained continent surrounded by water, Antarctica has its own weather and climate system.

Until 2016, winter sea ice in Antarctica had been increasing.

But in March 2022, an extreme heatwave hit East Antarctica, sending temperatures as high as -10°C when they should have been closer to -50°C.

“When I started studying Antarctica 30 years ago, we never imagined that extreme weather events could occur there,” says Professor Siegert.

The sea ice has record lows broken in the summer for three of the past seven years, including February 2023.

Some scientists even believe that this data on low ice levels could indicate that a fundamental change is happening on the continent: a change in the conditions that have kept the region isolated.

The remoteness of Antarctica and the scarcity of historical information mean that much is still unknown.

In scientific terms, the region remains the ‘wild west’, according to Dr Robbie Mallet.

Scientists know how far sea ice extends, but not how thick it is, for example.

Unlocking that puzzle could revolutionize climate models in the region.

Lots of reasons to be concerned

On the scientific basis of Rothera, Dr. Mallet radar instruments to Study the thickness of sea ice for an international research project called Defiant.

He and other scientists are still trying to unravel the causes of the disappearance of winter ice.

“There’s a chance that this is a very strange expression of natural variability,” he says, meaning that many natural factors could have accumulated and influenced the region at the same time.

This year’s record-breaking ocean temperatures will likely be a contributing factor, scientists suggest: warm water won’t freeze.

And there may also have been changes in the ocean currents and winds that push up temperatures in Antarctica.

The meteorological phenomenon of The boycurrently developing in the Pacific Ocean could also subtly contribute to sea ice reduction, although it is still weak.

Dr. Mallet says there are many “reasons to be concerned.”

“It’s potentially a very alarming sign of climate change in Antarctica that hasn’t occurred in the last 40 years. And it’s only now coming to light.” (JO)