Greenland’s ice sheets are melting faster than at any time in the last 400 years, researchers have warned.
The lead scientist on the paper, Dr Luke Trusel, said: “Melting of the Greenland ice sheet has gone into overdrive.
“As a result, Greenland melt is adding to sea level more than any time during the last three-and-a-half centuries, if not thousands of years.
“And increasing melt began around the same time as we started altering the atmosphere in the mid-1800s.”
Dr Trusel’s co-author, Dr Sarah Das, said that from a historical perspective “today’s melt rates are off the charts”.
Compared to the start of the industrial era, 50 per cent more ice sheet meltwater is running off Greenland and into the Arctic Ocean today, she said.
There has been a 30 per cent increase since the 20th century alone.
“Rather than increasing steadily as the climate warms, Greenland will melt increasingly more and more for every degree of warming,” Dr Trusel said.
“The melting and sea level rise we’ve observed already will be dwarfed by what may be expected in the future as the climate continues to warm.”
The Greenland ice sheet is a mile-thick layer of frozen water which melts back into liquid on the surface of the sheet during warm summer days.
Meltwater then either runs off the sheet into the ocean, pushing up sea levels worldwide, or it refreezes, forming layers of densely packed ice over time.
The scientists running the study used a drill longer than a traffic light pole to extract ice cores from the ice sheet itself, to examine what kind of melting took place as far back as the 17th century.
This method provides much deeper historical evidence for how much melting is caused by climate change than the normal satellite images, which only date back to the 1970s.
Matt Osman, a graduate student who also worked on the study, said: “We have had a sense that there’s been a great deal of melting in recent decades, but we previously had no basis for comparison with melt rates going further back in time.
“By sampling ice, we were able to extend the satellite data by a factor of ten and get a clearer picture of just how extremely unusual melting has been in recent decades compared to the past.”
And the results show that even small amounts of additional warming could cause a huge spike in ice sheet melting.
Dr Das said this underlined how sensitive the Arctic ice was to climate change.
Sea levels have gone up an average of 10 to 20cm over the past century, but this has rapidly sped up in the last 20 years.
Even small increases can cause devastation in coastal countries and communities, through habitat erosion, flooding and more powerful storm surges.
The Intergovernmental Panel on Climate Change has predicted the oceans worldwide could rise as much as 98cm by the end of the century, which would be high enough to swamp major cities across the world including Rio de Janeiro, Shanghai, Osaka, Hong Kong and Miami.
If the most pessimistic outcomes arise and the entire Greenland ice sheet melts, the sea would rise by a huge 700cm, enough to entirely submerge London.
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