A long-lost soil sample taken from beneath the Greenland ice sheet in 1966 but rediscovered in 2017 after being stored in a Danish freezer for five decades, shows that the stability of the ice sheet is far more tenuous and could lead to a far faster increase in sea levels than thought, CNN reports.
The 12-foot core shows that Greenland was essentially ice-free as late as 400,000 years ago, when temperatures were moderately above the norm; scientists previously believed the ice sheet had been stable for millions of years. The discovery means the ice sheet could be lost under far less harsh conditions than previously thought.
With carbon levels in the atmosphere already 1.5 times higher than they were during the last melt, a new melt could be more rapid. However, when the Greenland ice sheet completely melted away 400 millennia ago, it resulted in a sea level rise of roughly seven meters, a result that would devastate human populations.