Large icebergs float away as the sun rises near Kulusuk, Greenland, last year. Photos / AP file
Large icebergs float away as the sun rises near Kulusuk, Greenland, last year. Photos / AP file
Greenland's ice sheet will shrink more this century than at any point in the past 12,000 years, outstripping an earlier period of warming that began 10,000 years ago, scientists predict.
Between 2000 and 2018 the ice sheet shrank at a rate of 6100 billion tonnes per century, but that ratecould accelerate to unprecedented levels, a team from the US, Canada and Denmark concluded.
The paper, published in the journal Nature, compares rates of mass loss to those seen during a natural period of warming in the early Holocene era, between 10,000 and 7000 years ago.
While current levels of loss are comparable to the highest rate of shrinkage during that period, which were around 6000 billion tonnes per century, this will not be be the case over the rest of the century, the team's models show.
On average over the 21st century the ice sheet will lose between 8800 and 10,600 billion tons in a low-emissions scenario and 14,000 to 35,900 billion tonnes in a high-emissions scenario, the model predicts.
"Our results suggest that the rate of mass loss from the Greenland Ice Sheet this century will be unprecedented in the context of natural variability over the past 12,000 years, unless a low-carbon-emission scenario is followed," the authors conclude.
A boat navigates at night next to large icebergs in eastern Greenland. Greenland's ice has been melting for more than 20 years.
A separate study published earlier this year in the journal Nature Climate Change found that mass loss from both Greenland and Antarctica was tracking the upper end of projections by the Intergovernmental Panel on Climate Change, which assume a high level of fossil fuel emissions.
This is the first time a group of scientists has modelled long-term historic levels of Greenland ice sheet loss alongside future levels.
During the earlier warm period, temperatures in the far northern hemisphere increased by up to 4C, an effect thought to be caused by the angle of the earth's orbit at the time.
Lead author Jason Briner, professor of geology at the University at Buffalo, said the results showed that man-made climate change was having a more extreme impact on the ice sheet than natural changes.
"The Greenland Ice Sheet hasn't seen anything like this ... Even when the Arctic was warmer because the northern hemisphere was getting more energy from the sun thousands of years ago, it didn't melt like it's melting today."
The team took data from ice cores to map temperatures and precipitation levels up until 1850, and used existing climate data to drive the model beyond that date.
Previous studies suggested that melting could lead to global sea level rises of between 4cm and 27cm this century, depending on emissions levels.
