If human societies don’t sharply curb emissions of greenhouse gases, Greenland’s rate of ice loss this century is likely to greatly outpace that of any century since shortly after the end of the last ice age, a new study concludes.
The findings place the ice sheet’s modern decline in a solid historical context for probably the first time, highlighting just how extreme projected losses for the 21st century could be, researchers say. The research was published this week in the journal Nature.
Scientists used new, detailed reconstructions of ancient climate to drive a model of the past, present and future of the Greenland ice, and validated the model against real-world measurements of the ice sheet’s contemporary and ancient size.
“Basically, we’ve altered our planet so much that the rates of ice sheet melt this century are on pace to be greater than anything we’ve seen under natural variability [over] the past 12,000 years,” said study leader Jason Briner, a geologist at the University at Buffalo.
The researchers say that under a best-case scenario, with society greatly reducing emissions, melting in Greenland in the 21st century will be just slightly higher than that of any other century of the past 12 millennia. But under a high-emissions scenario—the one the Greenland Ice Sheet is now following—the rate of mass loss could be about four times higher.
The study brought together climate modelers, ice core scientists, remote sensing experts and paleoclimate researchers at eight institutions including Columbia University’s Lamont-Doherty Earth Observatory. The team used a state-of-the-art ice sheet model to simulate changes to the southwestern sector of the ice sheet, starting from some 12,000 years ago and extending forward 80 years to 2100. They tested the model’s accuracy by comparing results of the model’s simulations to historical evidence. The modeled results matched up well with data tied to actual measurements of the ice sheet made by satellites and aerial surveys in recent decades, and with field work identifying the ice sheet’s ancient boundaries.
Lamont-Doherty geochemists Nicolás Young and Joerg Schaefer helped build a detailed geologic history of how the margin of the ice sheet moved through time by measuring isotopes of beryllium in boulders left by retreating ice at various times. “Amazingly, the model reproduced the geologic reconstruction really well,” said Young. “This gave us confidence that the ice sheet model was performing well and giving us meaningful results.” Though the project focused on southwestern Greenland, research shows that changes in the rates of ice loss there tend to correspond tightly with changes across the entire ice sheet.
Researchers at the University of California, Irvine and NASA’s Jet Propulsion Laboratory led the modeling. They leveraged the work of colleagues at the University of Washington, who used data from ice cores to create maps of temperatures and precipitation in the study region that were used to drive the ice sheet model simulations up to the year 1850. Previously published climate data was used to drive the simulations after that date. Lamont-Doherty and the University at Buffalo partnered on field work that helped validate the model by identifying the ice sheet’s previous boundaries.
“It is no secret that the Greenland Ice Sheet is in rough shape and is losing ice at an increasing rate,” Young said. But, he said, “I think this is the first time that [its] current health has been robustly placed into a long-term context.”
Despite the sobering results, one vital takeaway is that it is still possible for people around the world to make an important difference by cutting emissions. “Our findings are yet another wake-up call, especially for countries like the U.S.,” said Briner.
The research was largely funded by the U.S. National Science Foundation. The scientists also received support from the Natural Sciences and Engineering Research Council of Canada, Fonds de recherche du Québec, and NASA.
Adapted from a press release by the University at Buffalo.
