Ice sheets could melt 20 times faster than previously thought

An international research team led by Dr Christine Batchelor of the University of Newcastle, England, used high-resolution images of the seafloor to confirm how quickly an ancient ice sheet stretched out from Norway at the end of the last Ice Age. 20,000 years ago. From there, it was concluded what could happen today.

The method followed to discover it

The team, which includes researchers from the Universities of Cambridge and Loughborough (UK) and the Norwegian Geological Survey, has mapped more than 7,600 small landforms on the seafloor called ripple ridges. These ridges are less than 2.5 meters high and are separated by a distance of between 25 and 300 meters.

These ridges are thought to form when the edge of the retreating ice sheet rises and falls with the tides, pushing seafloor sediments up a hill at each tide. Because two ridges would occur each day (with two tidal cycles per day), the researchers were able to calculate how fast the ice sheet was retreating.

Their results show that the old ice sheet is receding at a rate of between 50 and 600 meters per day. a much higher velocity than other ice sheets observed from satellites or extracted from similar formations in Antarctica.

According to Dr Batchelor, “This research is a warning from the past about the rate at which ice sheets are physically retreating.. Our results show that rapid recoil pulses can be much faster than anything we’ve seen so far.”

Information about the behavior of ice sheets during past periods of climate warming is important for computer simulations that predict future changes in ice sheets and sea level.

“This studio demonstrates the value of obtaining high-resolution images of glacial landscapes preserved on the seafloor“, says study co-author Dr. Dag Ottesen from the Norwegian Geological Survey.

New research shows thatPeriods of such rapid retraction of the ice sheet can be very short (from days to months)..

“This suggests that average rates of ice sheet retreat for several years or longer may hide shorter episodes of retreat,” said study co-author Professor Julian Dowdeswell, of the University of Cambridge. this ‘pulsed’ behavior of the ice sheet.”

Seafloor shapes also shed light on the mechanism by which such rapid retreat could occur. Dr Batchelor and colleagues discovered that the old ice sheet retreated faster along the flatter parts of its bed.

“An ice floe can break off the seafloor and retract almost instantly once it becomes buoyant,” explains Frazer Christie, “This type of retreat only occurs on relatively flat beds.” where less melting is needed to dilute the overlying ice to the point where it starts to float.”

Could be soon in Antarctica

The researchers conclude that similarly fast-receiving pulses could soon be observed in parts of Antarctica.. This includes the vast Thwaites Glacier, which has been the subject of significant international research due to West Antarctica’s potential susceptibility to unstable retreat. The authors of this new study suggest that the Thwaites Glacier may be experiencing a rapid retreat pulse as it recently retreated near a flat area of ​​its bed.

“Our findings show that current snowmelt rates It is sufficient to cause brief flashes of rapid rebound in flat areas of the Antarctic ice sheet.Including Thwaites,” Batchelor said. It is quite possible that satellites will detect such ice sheet retreat in the near future, especially if the current warming trend in the climate continues.”

Reference work: https://www.nature.com/articles/s41586-023-05876-1

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