Researchers from the National Geological Survey of Denmark and Greenland (GEUS) studied two decades of measurements to predict the minimum ice loss from the Greenland Ice Sheet from climate warming so far. Their findings suggest that, under the best-case scenario, the Greenland ice sheet will lose about 110 trillion tons of ice. “Under the foreseeable scenario that global warming only continues, the contribution of the Greenland ice sheet to sea level rise will continue to increase,” said Professor Jason Box, lead author of the study. “When we take the extreme melt year of 2012 and assume an average stable climate later this century, the locked mass loss from the Greenland ice sheet more than doubles to 78 cm [30 inches].’ Melting of the Greenland ice sheet will cause sea levels to rise by more than 10 inches (27 cm) – even if the entire world stops burning fossil fuels, a new study has warned Their findings suggest that at best, at least 3.3 percent of the ice sheet would be lost, equal to 110 million tons of ice, or a 10-inch (27-centimeter) rise in sea level.
What time frame are we looking at?
While previous studies have estimated sea-level rise with climate models, this is the first time researchers have made estimates based on measurements.
Unfortunately, the downside of this method is that it doesn’t give a time frame.
“To get the number we have, we had to factor time into the calculation,” added Professor Box.
“But our observations show that most of the committed sea-level rise will occur this century.”
In the study, the researchers looked at changes in the snow line — the boundary between areas exposed to net melt during the summer and areas that are not — of the Greenland ice sheet from 2000 to 2019.
Ice along the sheet does not melt equally, with ice along the edges at lower elevations melting faster.
Higher up on the ice sheet, it is too cold for melting to occur, even in summer.
The snow line is defined by the line where the top layer of winter snow does not melt in the summer, but remains on top, feeding the ice sheet.
This line varies from year to year, depending on the weather.
For example, a warm summer can move the line further up the ice sheet, while a colder year can push the line down towards the edges of the ice.
Snow that falls on the ice during the winter turns into new ice over time—that is, if it doesn’t melt during the summer.
For the ice sheet to be in equilibrium, the mass added must equal the mass lost.
While this occurs in a stable climate, a hot summer causes the snowpack to melt.
Professor Jason Box samples ice standing on exposed ice below the snow line of the Greenland Ice Sheet in West Greenland during the melt season
“When we take the extreme melt year of 2012 and assume an average stable climate later this century, the locked mass loss from the Greenland ice sheet more than doubles to 78 cm [30 inches]” said Professor Box
This snow will be missing from the mass budget for years to come, creating an imbalance.
Using rigorous glacial theory, the researchers calculated the average snowline required to bring the ice sheet back into equilibrium.
Their findings suggest that at best, at least 3.3 percent of the ice sheet would be lost, equal to 110 million tons of ice or a 10-inch (27-centimeter) rise in sea level.
“It’s a very conservative minimum,” Professor Box said.
“Realistically, we will see that rate more than double within this century.”
The researchers only looked at the Greenland ice sheet and did not consider sea level rise as a result of melting in Antarctica.
The team of glaciologists sets up an automatic weather station on the snowy surface above the snow line during the melt season
While previous studies have estimated sea-level rise with climate models, this is the first time researchers have made estimates based on measurements.
This radically different method has raised some eyebrows in the scientific community according to Professor Box.
“Ice flow models are not ready in this area,” he explained. “This is a complementary way of accounting for the missing mass loss.”
Unfortunately, the downside of this method is that it doesn’t give a time frame.
“To get the number we have, we had to factor time into the calculation,” added Professor Box.
“But our observations show that most of the committed sea-level rise will occur this century.”
SEA LEVELS MAY RISE UP TO 4 FEET BY 2300
Global sea levels could rise by as much as 1.2 meters (4 feet) by 2300 even if we meet the 2015 Paris climate targets, scientists have warned. The long-term change will be caused by the melting of ice from Greenland to Antarctica, which is set to reshape the world’s coastlines. Rising sea levels threaten cities from Shanghai to London, low-lying areas of Florida or Bangladesh, and entire nations like the Maldives. It is vital to 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 predicted sea levels would rise by 0.7-1.2 meters, even if nearly 200 nations fully meet the targets under the 2015 Paris Agreement. The goals set by the agreements include reducing greenhouse gas emissions to net zero by the second half of this century. Ocean levels will rise inexorably because the heat-trapping industrial gases already emitted will remain in the atmosphere, melting more ice, he said. In addition, water naturally expands as it is heated above four degrees Celsius (39.2°F). Every five years of delay after 2020 in the peak of global emissions would mean an additional 20 cm (8 in) of sea level rise by 2300. “Sea level is often communicated as a very slow process that you can’t do much about… but the next 30 years really matter,” said lead author Dr Matthias Mengel, of the Potsdam Institute for Climate Impact Research, Potsdam . Germany. None of the nearly 200 governments that signed the Paris Agreements are on track to meet their commitments.
