PARIS: Ice loss from Greenland’s massive ice sheet will cause sea levels to rise more during the 21st century than they have during any 100-year period in the last 12,000 years, even if global warming is held in check, scientists said Wednesday.
The study — based on ice core data and models and published in the journal Nature — is the first to painstakingly reconstruct Greenland’s ice loss record over the entire course of the Holocene, the geological epoch that has allowed civilisation to flourish.
It found that if greenhouse gas emissions continue unabated, the kilometres-thick ice block will shed some 36 trillion tonnes of mass from 2000 to 2100, enough to lift the global ocean waterline by 10 centimetres.
Until the late 1990s, Greenland’s ice sheet was roughly in balance, gaining as much mass through snowfall as it lost in summer from crumbling glaciers and melt-off.
But accelerating climate change has destroyed that balance, with the net loss flowing into the north Atlantic.
The northern hemisphere’s only ice sheet ultimately holds enough frozen water to raise seas by seven metres. If it were to pass a temperature “tipping point” into irreversible decline — a threshold that could be as low as two degrees Celsius above preindustrial levels — the ice sheet would likely take thousands of years to melt away, scientists say.
But even in the short term, increases in sea level measured in tens of centimetres will devastate coastal communities around the world.
Areas currently home to 300 million people — mostly in poorer nations — will be vulnerable by 2050 to regular flooding from storm surges, earlier research has shown.
Last year, Greenland cast off more than 500 billion tonnes of ice and meltwater — 40 percent of total sea level rise in 2019 and the most in a single year since satellite records began in 1978.