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East Antarctic Ice Sheet may be melting much faster than previously thought: Study


Press Trust of India London
There are more than 65,000 supraglacial lakes -- water bodies formed on the top of glaciers as they melt -- in the East Antarctic Ice Sheet, which is a significantly greater number than what was previously thought, according to a study.
The research, published in the journal Scientific Reports, was carried out using high-resolution satellite imagery covering five million square kilometres of the ice sheet, and found that the glaciers were forming meltwater, including in areas where the process was believed to be less intense.
The authors of the study, including those from Durham University in the UK, mapped for the first time the widespread distribution of lakes across a vast area of the East Antarctic Ice Sheet, which is the world's largest ice mass.
"We've known for some time that lakes are forming in East Antarctica, but we were surprised at quite how many had formed and all around the ice sheet margin," said lead author of the study Chris Stokes of Durham University.
According to the researchers, even if the ice sheet was incredibly cold most of the year, reaching -40 degrees Celsius in winter, the summer temperatures, they said, can often reach above zero and melt the surface of the glaciers.
The puddles and lakes formed in most of the coastal regions of the ice sheet.
This according to the researchers meant that East Antarctica could be more susceptible to the effects of global warming than previously thought.
When the researchers looked at satellite images of the East Antarctic Ice Sheet, acquired in January 2017, they found that the meltwater lakes often clustered a few kilometres from where the ice sheet began to float on the sea.
They found that some of the supraglacial lakes can exist hundreds of kilometres inland, and at elevations of upto a kilometre.
They added that about 60 per cent of the lakes developed on floating ice shelves, some of which were at risk of collapsing when the stagnating puddle became large enough to fracture and drain through the ice.
Through this study, the researchers could see where the lakes were forming in the highest densities because of the surface melting.
They could also see which parts of the ice sheet might be the most vulnerable to climate change.
Many of the lakes were the size of a standard swimming pool, while the largest measured over 70 square kilometres, the study noted.
"The density of lakes in some regions is similar to the densities we've observed on the Greenland Ice Sheet, and on the Antarctic Peninsula, which are generally viewed as much warmer," Stokes said.
The major concern, according to the researchers was that in other areas, large numbers of lakes draining can "fracture apart floating ice shelves, causing the inland ice to speed-up."

The study also noted that the number of lakes mapped was a lower estimate as some small lakes might have been missed, while others might have grown bigger in December or February.
"This dataset should help us better understand why lakes are forming where they are, and that will help us predict how the distribution of lakes will change in the future, especially if air temperatures warm," Stokes said.
While there is no imminent threat to the ice sheet's stability, the study, according to the researchers, revealed which areas we should keep an eye on for the next few years.

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First Published: Sep 27 2019 | 4:20 PM IST

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