Scientists have discovered a long-lost landscape that has been preserved for 30 million years under an Antarctic ice sheet.
The erosion by ancient rivers appears to have been carved large flat surfaces under the ice in the East Antarctica 80-34 million years ago. Understanding how these features are formed and how they continue to affect the landscape could help improve forecasts of future ice losses, the researchers reported July 11 in the journal Nature Geoscience.
“We have been baffled for a long time about fragments of “flat” landscapes,” said Neil Ross, co-author of geophysicists at Newcastle University in the UK, in a statement. “This study will bring together the jigsawpa data fragments to reveal the overall picture. It could affect how these ancient surfaces were formed, their role in determining the current flow of ice, and how the East Antarctic ice sheet evolves in the world of warming.”
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If the East Antarctic ice sheets are completely melted, they could raise global sea levels by more than 160 feet (50 meters). However, to accurately predict how melting an ice sheet will be in the coming years, scientists will need to know its past behavior and its underlying conditions.
In the new study, researchers used radar data from four previous studies to map the shape of bedrock beneath the ice.
“As we were looking at radar images of sub-ice topography in the area, these very flat surfaces began to pop out almost everywhere we saw,” Guy Paxman, co-author of a polar geophysicist at Durham University in the UK, said in a statement. “The flat surfaces we discovered have survived relatively unharmed for over 30 million years, indicating that parts of the ice sheet preserve rather than erode the landscape.”
The flat spread, studded with deep troughs, covered a 2,175-mile (3,500-kilometer) section of the East Antarctic Coastline. They were probably formed before the East Antarctic ice sheets existed, but after the supercontinent Gondwana (including modern Antarctica, Australia, Africa and India) broke.
This allowed researchers to date flat sections from 80 million to 34 million years ago.
On these flat surfaces, Antarctic ice moves quite slowly. However, in the trough between them, the ice flows much faster. Meltwater may have carved these valleys by flowing through natural dips as the East Antarctica ice sheet expanded millions of years ago.
Slow flow of ice on flat surfaces can regulate the loss of ice from the continent, the researchers wrote in their study. Further studies such as the acquisition and analysis of rock samples from underneath ice could improve future ice losses and projections of sea level rise.
“Information such as the shape and geology of the newly mapped surfaces will help us to better understand how ice flows at the edge of the East Antarctica,” Paxman said. “This will allow us to easily predict how the East Antarctic ice sheet will affect sea levels in the future under various levels of climate warming.”
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