'Antarctica's seemingly impregnable ice sheet is melting from below'

According to experts writing in The Conversation, today, deep polar waters are getting warmer, as the oceans absorb almost all of the excess heat on Earth from burning fossil fuels. 'The seemingly impenetrable ice layer in Antarctica is melting from below,' the article commented.

Looking back more than 100 years ago

In 1897, the RV Belgica (once a whaling ship ) left Antwerp, Belgium, heading south. It was the first voyage of the 'heroic age' of Antarctic exploration. This voyage, however, did not go according to plan.

After a six-month journey, they began encountering sea ice. Many times the ship was stuck in ice for a day or two. A crew member fell overboard and was lost in the icy water. But the team continued to take measurements on the go. Expedition leader Adrien de Gerlache recorded the process as follows:

'At noon, we made deep-sea acoustic measurements, with a range of temperatures at various depths. We dropped 560 meters of rope and brought back a block of blue clay. Sea surface temperatures are above freezing and a little warmer below.'

Their discovery of warm deep waters was very important. Since then it has been named 'polar deep water'.

Today, deep polar waters are getting warmer, as oceans absorb almost all of Earth's excess heat from burning fossil fuels. (Illustration)

In the years 1897-1898, the power of the frost was still very formidable. At that time, the expedition on the RV Belgica was often stuck in thick ice, and the members experienced winter for months on end, with cold and darkness. The cold was so intense that they often wrote their wills before going to bed. It was not until January 1899, after many attempts to use explosives to break the ice, that they were able to free the ship to return home.

Today's scientists, when comparing the data with what the RV Belgica team found many years ago, have extracted invaluable information.

Ice declines by 12% every decade

If RV Belgica were in the same location in the Bellingshausen Sea off the coast of the Antarctic Peninsula, but in 2023, instead of 1897, the story would be very different.

Over the past 126 years, humans have contributed to changing Earth's climate. Fossil fuels have given us more energy, but with unpredictable consequences – burning these fuels releases carbon dioxide and other long-buried gases into the atmosphere. These gases magnify the natural greenhouse effect that keeps the Earth from freezing. Almost all of the heat trapped by human activities has entered the ocean.

Just like that, in the north, Arctic sea ice began to disappear from the 1970s onwards, decreasing by about 12% per decade.

An expedition ship was stuck in ice for more than a year.

Antarctic sea ice lasts longer. A ship like the Belgica might still be stuck in sea ice at the end of 2015. But not now. Over the past eight years, Antarctic sea ice has begun to seriously melt. And in the past three years, this melting has especially accelerated. Now, new research shows that Antarctic sea ice has undergone an 'abrupt transition'.

As of March 2023, the waters RV Belgica once passed through no longer have cracked ice blocks. There is almost no ice in the Bellinghausen Sea from February to April.

In early 2024, the Australian marine research vessel RV Investigator traveled 12,000 km from Hobart down the Antarctic coast and back to Fremantle. What's shocking is how easy this cruise was.

When the sea ice is at its thickest, even modern ships have difficulty navigating. But on this trip, scientists on board collected huge amounts of data from dark oceans that should have been covered by thick sea ice.

In 2024, a ship will reach the South Pole with almost no problems.

"Doomsday Glacier"

In the ice continent, climate change is causing long-worrying changes.

The Antarctic Peninsula – the long tail closest to South America, where most cruise ships dock – is starting to turn green. More algae grows on snow, while two native flowering plants, Antarctic pearlgrass and Antarctic hairgrass, are also expanding their range on the islands.

In the 19th century, reaching the South Pole was a dangerous journey, pushing the limits of human endurance. But as sea ice recedes, it is becoming increasingly easier for cruise ships to make the journey from ports in Argentina and Chile to the polar region. The number of tourists on this route has increased tenfold since the 1990s, growing especially rapidly in the past two years.

The ice continent has long been protected by cold, fast-flowing waters in the surrounding oceans. But now heat enters this area through water, not through air. The Antarctic Circumpolar Current is accelerating and warmer water is flooding into these icy waters. Antarctica's sea ice is being 'eroded' from within.

That means the so-called 'doomsday glacier' is in danger. Thwaites Glacier is the size of the UK and holds enough water to raise sea levels by 60cm. But the real threat lies behind Thwaites. This glacier is also a stopper, preventing much larger glaciers from flowing into the ocean. If this happens, sea level rise will accelerate.

Antarctica was once a place where humans found their limits. Enduring cold, endless darkness, and days drifting helplessly in the ice, the Belgica crew found themselves.

'More than a century later, we realize that ice has its limits,' the experts wrote.