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Ice sheets can retreat much faster than previously thought

According to a new study led by Newcastle University, ice sheets can retreat at an astonishing rate of up to 600 meters per day during periods of climate warming. The experts used high-resolution seafloor imagery to map more than 7,600 small-scale landforms called “corrugation ridges” to reveal the speed at which a former ice sheet that extended from Norway retreated about 20,000 years ago, at the end of the last Ice Age.

These ridges, less than 2.5 meters high and spaced between about 25 and 300 meters apart, were formed when the ice sheet’s retreating margin moved up and down with the tides, pushing seafloor sediments into a ridge at every low tide.

By calculating the rate at which the ridges were produced, the researchers found that the former ice sheet underwent pulses of rapid retreat at a speed of 50 to 600 meters per day – 20 times faster than the highest rate of retreat previously measured. This is much faster than any ice sheet retreat rate observed from satellites or inferred from similar landforms in Antarctica.

These findings could inform computer simulations that predict future ice-sheet and sea-level change, by showing how rates of ice-sheet retreat averaged over several years or longer can conceal shorter episodes of more rapid retreat. “It is important that computer simulations are able to reproduce this ‘pulsed’ ice-sheet behavior,” said study co-author Professor Julian Dowdeswell, a glaciologist at the University of Cambridge.

The seafloor landforms also provide insight into the mechanism by which such rapid retreat can occur. The analysis revealed that the former ice sheet had retreated fastest across the flattest parts of its bed, where less melting was required to thin the overlying ice to the point where it starts to float. According to the scientists, pulses of similarly rapid retreat could soon be observed in parts of Antarctica, including at West Antarctica’s vast Thwaites Glacier, which has recently retreated close to a flat area of its bed.

“Our findings suggest that present-day rates of melting are sufficient to cause short pulses of rapid retreat across flat-bedded areas of the Antarctic Ice Sheet, including at Thwaites,” said study lead author Christine Batchelor, a physical geographer at Newcastle. “Satellites may well detect this style of ice-sheet retreat in the near-future, especially if we continue our current trend of climate warming.”

“Our research provides a warning from the past about the speeds that ice sheets are physically capable of retreating at. Our results show that pulses of rapid retreat can be far quicker than anything we’ve seen so far,” she concluded.

About ice sheets

Ice sheets are enormous masses of ice that cover large areas of land. These ice sheets are found mostly in Antarctica and Greenland.

Ice sheets form when snow that falls on the land does not melt, but instead piles up over time. As more snow falls, the weight of the snow on top compresses the snow underneath. This compression causes the snow to turn into ice, and over time, the ice can become thousands of meters thick.

Ice sheets are important because they play a critical role in regulating the Earth’s climate. They reflect sunlight back into space, which helps to cool the planet. They also store massive amounts of freshwater, which can affect ocean currents and sea level.

Unfortunately, ice sheets are also at risk due to climate change. As the Earth’s temperature rises, the ice sheets are melting at an alarming rate. This melting can lead to rising sea levels, which can have devastating effects on coastal communities.

Scientists are studying ice sheets to better understand how they work and how they are changing. By studying ice sheets, we can better predict the impacts of climate change and take steps to mitigate its effects.

Ice sheets are fascinating and important features of our planet. While they are at risk due to climate change, we can work together to better understand them and protect them for future generations.

The study is published in the journal Nature.

Image Credit: ©NASA/USGS, processed by Dr. Frazer Christie, Scott Polar Research Institute, University of Cambridge

By Andrei Ionescu, Staff Writer

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