By 2100, Greenland will be shedding ice faster than at any time in the past 12,000 years, scientists report October 1 in Nature.
Since the 1990s, Greenland has shed its ice at an increasing rate (SN: 8/2/19). Meltwater from the island’s ice sheet now contributes about 0.7 millimeters per year to global sea level rise (SN: 9/25/19). But how does this rapid loss stack up against the ice sheet’s recent history, including during a 3,000-year-long warm period?
Glacial geologist Jason Briner of the University at Buffalo in New York and colleagues created a master timeline of ice sheet changes spanning nearly 12,000 years, from the dawn of the Holocene Epoch 11,700 years ago and projected out to 2100.
The researchers combined climate and ice physics simulations with observations of the extent of past ice sheets, marked by moraines. Those rocky deposits denote the edges of ancient, bulldozing glaciers. New fine-tuned climate simulations that include spatial variations in temperature and precipitation across the island also improved on past temperature reconstructions.
During the past warm episode from about 10,000 to 7,000 years ago, Greenland lost ice at a rate of about 6,000 billion metric tons each century, the team estimates. That rate remained unmatched until the past two decades: From 2000 to 2018, the average rate of ice loss was similar, at about 6,100 billion tons per century.
Over the next century, that pace will accelerate, the team says. How much depends on future greenhouse gas emissions: Under a lower-emissions scenario, ice loss is projected to average around 8,800 billion tons per century by 2100. With higher emissions, the rate of loss could ramp up to 35,900 billion tons per century.
Lower emissions could slow the loss, but “no matter what humanity does, the ice will melt this century at a faster clip than it did during that warm period,” Briner says.