Greenland is on track to lose ice mass faster at the end of this century than during any other century over the last 12,000 years, according to a new study.
US researchers simulated high-carbon-emission scenarios of the Greenland Ice Sheet – a 660,000 square mile body of ice that covers around 80 per cent of the surface of the island.
Under a scenario of high greenhouse gas emissions, ice mass loss could be four times higher than anything experienced over the past 12,000 years.
Their new prediction is conditional on whether human societies ‘sharply curb’ emissions of greenhouse gases like carbon dioxide, which cause global warming.
Reducing carbon emissions is needed to decrease the contribution of the Greenland Ice Sheet to rising sea levels, which could flood cities in the next 50 years.
The edge of the Greenland Ice Sheet – the second-largest ice body in the world, after the Antarctic Ice Sheet. If human societies don’t sharply curb emissions of greenhouse gases, Greenland’s rate of ice loss this century is likely to outpace that of any century over the past 12,000 years
‘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 of the ice sheet over the past 12,000 years,’ said lead author Jason Briner at the University at Buffalo in the US.
‘We’ll blow that out of the water if we don’t make severe reductions to greenhouse gas emissions.’
Scientists used new, detailed reconstructions of ancient climate for their simulation model, which was validated against real-world measurements of the ice sheet’s contemporary and ancient size, taken from samples in the field.
Samples from Greenland boulders, for example, contain chemical isotopes that can help scientists determine the ancient boundaries of Greenland Ice Sheet.
The experts simulated changes in the sheet from the beginning of the Holocene epoch, around 12,000 years ago, and extending into the future up to 2100.
Although the current rate of ice loss in Greenland is comparable to the highest rates during the Holocene, the researchers believe future rates are likely to exceed them.
The research team’s data shows Greenland ice loss has veered below zero at points throughout the last 6,000 years, but is set to soar upwards at the end of the 21st century.
The project focused on southwestern Greenland. The largest ice mass losses in the past, between 10,000 and 7,000 years ago, were at rates of around 6,000 billion tonnes per century
In their simulations, the researchers found that the largest ice mass losses in the past, between 10,000 and 7,000 years ago, were at rates of around 6,000 billion tonnes per century.
This is similar to the estimated rates of the first two decades of this century (2000–2018) of around 6,100 billion tonnes per century.
However, projected mass losses for the rest of this century are expected to exceed those maximum rates, they say.
The melting of the Greenland Ice Sheet is also currently causing sea levels to rise by about 0.02 inches (0.7mm) per year.
But new model predicts it could reach somewhere between 0.07 inches and 0.27 inches (2mm to 7mm) per year by 2100.
a) Map of the present-day Greenland Ice Sheet, showing commonly used domains (as labelled) and our model domain (outlined in red). NO, north; NE, northeast; NW, northwest; CW, central–west; SE, southeast; SW, southwest. b) and c) show moraine sequences – accumulations of unconsolidated glacial debris
A rise in sea levels would see many cities around the world exposed to coastal flooding, which could lead to mass evacuations.
Researchers took into account the different climate eventualities as outlined in the UN’s Intergovernmental Panel on Climate Change ‘RCP’ system.
The RCP trajectory ranges from RCP1.9 – where global warming is limited below 2.7°F (1.5°C) as per the goal of the Paris Agreement – to the dreaded RCP8.5, where emissions continue to rise throughout the 21st century.
In the RCP scenario with the lowest greenhouse gas emissions in this study (RCP2.6), the predicted mass loss is around 8,800 billion tonnes per century.
But this increases to around 35,900 billion tonnes in the scenario with the highest emissions, RCP8.5 – where emissions would continue to rise throughout the 21st century.
‘If the world goes on a massive energy diet, in line with RCP2.6, our model predicts that the Greenland Ice Sheet’s rate of mass loss this century will be only slightly higher than anything experienced in the past 12,000 year,’ said Briner.
Scientists collect samples from boulders in Greenland. These samples contain chemical isotopes that can help scientists determine the ancient boundaries of the ice sheet
‘But more worrisome is that under a high-emissions RCP8.5 scenario – the one the Greenland Ice Sheet is now following – the rate of mass loss could be about four times the highest values experienced under natural climate variability over the past 12,000 years.’
The amount of ice lost this century could reverse 4,000 years of cumulative ice growth and exceed previous mass-loss rates by about fourfold.
The authors conclude that unprecedented rates of mass loss will occur unless a low-carbon-emission scenario is followed
Describing their findings as ‘yet another wake-up call’, researchers say the study highlights the ‘extreme and unusual’ projected Greenland ice sheet losses for the 21st century.
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.
The study has been published in Nature.
SEA LEVELS COULD RISE BY UP TO 4 FEET BY THE YEAR 2300
Global sea levels could rise as much as 1.2 metres (4 feet) by 2300 even if we meet the 2015 Paris climate goals, scientists have warned.
The long-term change will be driven by a thaw of ice from Greenland to Antarctica that is set to re-draw global coastlines.
Sea level rise threatens cities from Shanghai to London, to low-lying swathes of Florida or Bangladesh, and to entire nations such as the Maldives.
It is vital that we curb emissions as soon as possible to avoid an even greater rise, a German-led team of researchers said in a new report.
By 2300, the report projected that sea levels would gain by 0.7-1.2 metres, even if almost 200 nations fully meet goals under the 2015 Paris Agreement.
Targets set by the accords include cutting greenhouse gas emissions to net zero in the second half of this century.
Ocean levels will rise inexorably because heat-trapping industrial gases already emitted will linger in the atmosphere, melting more ice, it said.
In addition, water naturally expands as it warms above four degrees Celsius (39.2°F).
Every five years of delay beyond 2020 in peaking global emissions would mean an extra 20 centimetres (8 inches) of sea level rise by 2300.
‘Sea level is often communicated as a really slow process that you can’t do much about … but the next 30 years really matter,’ lead author Dr Matthias Mengel, of the Potsdam Institute for Climate Impact Research, in Potsdam, Germany, told Reuters.
None of the nearly 200 governments to sign the Paris Accords are on track to meet its pledges.