Mass loss from the Greenland Ice Sheet is likely to be higher in this century than at any time in the past 12,000 years, according to a new study in the journal Nature.
The findings are based on simulations of high-carbon-emission scenarios for the southwest region, but the researchers say rates of ice loss there tend to correspond tightly with changes across the entire ice sheet.
The project was led by the University at Buffalo, US, and brought together climate modellers, ice core scientists, remote sensing experts and paleoclimate researchers from a range of institutions.
They used a state-of-the-art ice sheet model to simulate changes starting from the beginning of the Holocene epoch some 12,000 years ago and extending forward to 2100.
The modelled results matched up well, they say, with data tied to actual measurements of the ice sheet made by satellites and aerial surveys in recent decades, and with fieldwork identifying the ice sheet’s ancient boundaries.
“We have long timelines of temperature change, past to present to future, that show the influence of greenhouse gases on Earth’s temperature,” says lead author Jason Briner.
“[N]ow, for the first time, we have a long timeline of the impacts of that temperature – in the form of Greenland Ice Sheet melt – from the past to present to future. And what it shows is eye-opening.”
The simulations, as reported, found the largest mass losses in the past (between 10,000 and 7000 years ago) were at rates of around 6000 billion tonnes per century, similar to the estimated 6100 billion for the start of this century (2000–2018).
However, projected mass losses for the rest of this century are in the range of 8800 to 35,900 billion tonnes, based on the lowest and highest greenhouse gas emissions scenarios, respectively.
If that’s correct, ice losses this century could reverse 4000 years of cumulative ice growth and exceed previous mass-loss rates by about fourfold, the authors say.
“We built an extremely detailed geologic history of how the margin of the southwestern Greenland Ice Sheet moved through time by measuring beryllium-10 in boulders that sit on moraines,” says co-author Nicolás Young from Columbia University.
“Moraines are large piles of debris that you can find on the landscape that mark the former edge of an ice sheet or glacier. A beryllium-10 measurement tells you how long that boulder and moraine have been sitting there, and therefore tells you when the ice sheet was at that exact spot and deposited that boulder.
“Amazingly, the model reproduced the geologic reconstruction really well. This gave us confidence that the ice sheet model was performing well and giving us meaningful results.”
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