Antarctica: from ‘refrigerator’ to ‘heater’ of the planet – 09/17/2023 – Environment

The sea ice surrounding Antarctica has reached a level well below any previous measurement, according to satellite data. This is causing alarm among scientists who saw the region as resistant to global warming.

“(The levels) are so far removed from anything we’ve ever seen, it’s almost hair-raising,” says Walter Meier, who monitors sea ice at the US Snow and Ice Data Center.

Instability in Antarctica could have far-reaching consequences, according to polar ecosystem experts.

The massive Antarctic ice floe helps regulate the planet’s temperature, as the white surface reflects the sun’s energy back into the atmosphere and cools the water below and around it.

With the reduction of this ice block, Antarctica could transform from “Earth’s refrigerator” into the planet’s “heater”.

The ice floating on the surface of the Southern Ocean today measures less than 17 million square kilometers. This is 1.5 million less sea ice than the historical average for the month of September, and well below the lowest levels measured in the region’s winter period.

Meier is not optimistic that this loss will be recovered significantly.

Scientists are still trying to identify all the factors leading to the record lows, but studying trends in Antarctica has always been a challenge.

In a year in which several records for high land and ocean temperatures were broken, scientists insist that it is necessary to pay attention to what is happening at the planet’s South Pole.

“We see how vulnerable it is,” says Robbie Mallet, of the University of Manitoba and currently based on the Antarctic Peninsula.

He says the thin sea ice observed this year has made field work even more difficult. “There is a risk that (the ice) will break off and float out to sea with us on top,” Mallet explains.

Sea ice forms during the Antarctic winter (March to October), before largely melting during the summer, and belongs to an interconnected system that also encompasses icebergs, land ice and huge ice shelves — which are floating extensions close to each other. the coast.

Sea ice acts as a protective layer that prevents excessive ocean warming.

Caroline Holmes, from the British Antarctic Survey project, explains that the impact of this layer’s shrinkage could become evident in the transition to summer — when uninterrupted melting could potentially occur.

The reason is that as more sea ice disappears, dark areas of the ocean will be exposed, absorbing heat from the sun rather than reflecting it. This will cause more heat to be incorporated into the water, which in turn will cause more ice to melt.

It is this cycle that could add even more heat to the planet, disrupting Antarctica’s typical role as a regulator of global temperatures.

“Are we waking up the Antarctic giant?” asks Professor Martin Siegert, a glacial specialist at the University of Exeter (United Kingdom). It would be, according to him, “an absolute disaster” for the world.

Since the 1990s, the loss of land ice in Antarctica has contributed to a 7.2 mm rise in sea levels. And even small increments produce huge storms that can sweep away coastal communities. In other words, the melting of sea ice could, in theory, be catastrophic for millions of people around the world.

As a continent surrounded by water, Antarctica has its own climate and system. Until 2016, the region’s ice was actually increasing during the winter months.

However, an extreme heat wave hit the continent in March 2022, leaving temperatures at -10°C when they should have been around -50°C.

Over the past seven years, sea ice has fallen to record low levels, including in February 2023.

Some scientists think this signals a fundamental change on the continent — including in the characteristics that kept this region isolated.

At the same time, this isolation also means that there is little historical information about Antarctica, called by Mallet the “Wild West” of science.

For example, scientists know the extent of sea ice, but not its thickness. Uncovering this type of information could be crucial for preparing climate models for the region.

At the Rothera science base, Mallet is using radar instruments to study the thickness of the ice and better understand the reasons behind the thinning of the ice layer. And the record heat recorded this year is probably one of the factors, as it makes it difficult for the water to freeze there.

There may also have been changes in ocean currents and winds that shape the temperature in Antarctica.

Furthermore, the natural phenomenon El Niño is another possible factor involved.

Either way, Mallet says there are “many, many reasons to worry.”

“It’s potentially a very alarming sign of changes in Antarctica’s climate that haven’t occurred in the last 40 years. And that are only now emerging.”