Ancient Antarctic ice melt caused a sea level rise of nearly 10 feet about 129,000 years ago – and it could happen again, scientists have warned.
Experts discovered that rising ocean temperatures caused massive melting of the West Antarctic ice sheet, which, unlike its eastern counterpart, rests on the seabed.
The episode took place during a period of warmer temperatures known as the “Last Interglacial,” which lasted about 129,000-116,000 years ago.
Less than 3.6 ° F (2 ° C) ocean warming was needed to bring about the flood, suggesting that a similar extreme rise in sea level could be the result of climate change.
The Paris Climate Agreement has required signatory countries to limit global warming to 2 ° C – but the team warns that we do not want to get close to this.
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Ancient Antarctic ice melt caused a sea level rise of nearly 10 feet about 129,000 years ago – and it could happen again, scientists have warned. Pictured, a blue ice field in Antarctica
WHAT WAS THE LAST INTERGLACIAL?
Also known as the “Eemian,” the last Interglacial was a warmer period in the history of the earth that lasted about 129,000-116,000 years ago.
Interglacials separate ice ages that occur every 100,000 years thanks to changes in the Earth’s orbit around the sun that change how much warming solar radiation arrived on the Earth’s surface.
We are currently living in another interglacial, which scientists have called the “Holocene.”
Man-made global warming in the Holocene makes the current interglacial unique in the history of our planet.
However, experts are studying the Last Interglacial to see how our planet has responded to extreme environmental changes in the past.
During the last Interglacial, sea levels were about 10 feet higher – and experts have now shown that the melting of the West Antarctica was largely responsible.
In their research, Earth scientist Chris Turney of the University of New South Wales in Australia and colleagues traveled to a so-called ‘blue ice’ area near the Patriot Hills on the edge of the West Antarctic Ice Sheet.
Blue ice areas are areas where surface snow and ice are gradually stripped off by strong, dense winds to leave a smooth, sometimes rippled surface that – unlike the typical white landscapes of Antarctica – has a blue tint.
While the surface is being removed, old ice flows up to replace it, giving scientists a window on the history of the ice sheet that is easily accessible.
“Instead of drilling for miles in the ice, we can simply walk across a blue ice area and travel back through millennia,” said Professor Turney.
“By taking ice samples from the surface, we can reconstruct what happened to this precious environment in the past.”
The researchers used a combination of the order of fine layers of ash deposited by volcanic eruptions and analyzes of gas bubbles and DNA from bacteria trapped in the ice to date the different parts of the blue ice surface.
From this, the team concluded that there was a gap in the record of preserved ice dating from just before the last Interglacial – one that coincides with the well-known period of exceptionally high sea levels.
This suggests that the West Antarctic is currently melting rapidly in response to warmer global temperatures.
Warmer ocean water is said to have melted and thinned the floating ice sheets around the West Antarctic ice sheet, making it vulnerable.
The researchers used a combination of the order of fine layers of ash deposited by volcanic eruptions and analyzes of gas bubbles, depicted, and DNA from bacteria trapped in the ice to date the different parts of the blue ice surface
“We not only lost much of the West Antarctic ice sheet, but this happened very early during the last Interglacial,” said Professor Turney.
The findings provide the first important evidence that the melting of the West Antarctica caused much of the sea level rise to be the last Interglacial – thought to be between 19-7-29.5 feet (6-9 meters) higher then was today.
Scientists were rather uncertain where all the extra water came from.
The melting of the Greenland ice sheet, the loss of mountain glaciers and the internal expansion of the warming ocean could only have accounted for a rise in sea level in total around 9.8 feet (3 meters).
“The melting was probably caused by ocean warming of less than 2 ° C – and that is something that has major implications for the future, given the rising temperature of the ocean and the West Antarctic melting that is happening today,” said Professor Turney.
Less than 3.6 ° F (2 ° C) ocean warming was needed to bring about the flood, suggesting that a similar extreme rise in sea level could be the result of climate change. The Paris Climate Agreement has required signatory countries to limit global warming to 2 ° C – but the team warns that we do not want to get close to this. Pictured, fine layers of ash in an ice sample
The severity of the ice loss of the West Antarctica in the last Interglacial raises the fear that the ice sheet may be equally sensitive to global warming in the future.
“The ice cap of the West Antarctica is in water and today this water is getting warmer and warmer,” said Professor Turney.
After studying the ice sheet, the team conducted simulations to investigate how rising temperatures could affect the floating ice sheets around the West Antarctic plate and act as a buffer that slows the continent’s ice flow.
The team discovered that a warmer ocean of 3.6 ° F (2 ° C) in the first thousand years would generate about 3.8 meters (12.5 feet) of sea level rise – a large proportion of which after the loss of the ice shelves. two hundred years in global warming.
“The positive feedback between a warming ocean, the collapse of ice plates and the melting of ice plates suggests that the West Antarctica may be vulnerable to passing a tipping point,” said paper co-author and Earth scientist Zoë Thomas of the University from New South Wales.
“When it reaches the tipping point, only a slight rise in temperature can lead to abrupt ice sheet melting and a sea level rise of several meters,” she added.
“We would lose most of the West Antarctic ice sheet in a warmer world,” says Professor Turney.
In their research, Earth scientist Chris Turney from the University of New South Wales in Australia and colleagues traveled to a so-called ‘blue ice’ area near the Patriot Hills on the edge of the West Antarctic Ice Sheet
According to the predictions of the Intergovernmental Panel on Climate Change, global sea level is expected to rise by about 40-80 cm by about 15.7 – 31.5 inches in the coming century, with Antarctica contributing only about 5 cm. .
However, the researchers fear that the southernmost continent can melt considerably more than expected.
“Recent projections suggest that the Antarctic contribution can be up to ten times higher than the IPCC prediction, which is very worrying,” said co-author and glaciologist Christopher Fogwill of the University of Keele in the UK.
“Our study emphasizes that the Antarctic ice sheet can be close to a tipping point, which can lead to a rapid rise in sea levels for the coming millennia.”
“This underlines the urgent need to reduce and control greenhouse gas emissions that are warming up today.”
Now that their first study has been completed, the researchers now want to expand the scope of their research to find out how quickly the West Antarctic ice sheet responded to global warming – and which areas were first affected.
“We only tested one location, so we don’t know if it was the first sector in Antarctica that melted, or whether it melted relatively late,” said Professor Turney.
“How these changes in Antarctica have affected the rest of the world is still an enormously unknown fact as the planet warms up in the future.”
“Testing other locations gives us a better idea of the areas that we really need to monitor if the planet keeps warming up.”
The full findings of the study were published in the journal Proceedings of the National Academy of Sciences.