Frozen Greenland is on track to be significantly less frozen before the 21st century is over. By 2055, winter snow on the Greenland ice sheet will no longer be enough to replenish the ice that Greenland loses every summer, new research shows.
This dramatic change is caused by rising global temperatures. If the Earth continues to warm at its current rate, Earth’s average temperature should rise by nearly 5 degrees Fahrenheit (2.7 degrees Celsius) by 2055. Regional averages in Greenland are getting even hotter, rising by about 8 F (4.5 C), scientists reported in a new study.
Under those conditions, Greenland’s annual ice loss could cause sea levels to rise by up to 13 centimeters by 2100 unless drastic measures are taken from now on to greenhouse gas emissions and slow global warming trends.
Related: Photos of Greenland’s beautiful glaciers
Ice sheets are all thick masses of ice that cover more than 20,000 square miles (50,000 square kilometers) of land, and they grow their icy layers from snow that has built up over thousands of years, according to the National Snow and Ice Data Center (NSIDC). During the last ice age (about 115,000 to 11,700 years ago), ice sheets covered much of North America and Scandinavia. But today there are only two ice sheets left – in Greenland and in Antarctica – with about 99% of the world’s freshwater resources, says NSIDC.
Ice sheets are not static – their own weight slowly pushes them towards the ocean, where they release ice and meltwater from ice shelves, streams and glaciers. An ice sheet can only remain stable as long as the lost ice is supplemented seasonally by winter snow.
The Greenland Ice Sheet is about three times the size of Texas and measures about 656,000 square miles (1.7 million square kilometers), according to NSIDC. If all of Greenland’s ice melted at once, sea levels would rise by about 20 feet (6 meters). While that catastrophic scenario is unlikely to happen anytime soon, Greenland has been steadily losing ice for decades, at a rate of about 500 gigatonnes per year since 1999, another study was found and published in August 2020.
Those scientists said Greenland was already losing more ice every winter than it gained. Their models took into account ice loss from iceberg calving, which can be significant; a huge iceberg that separated in 2018 and drifted disturbingly close to a Greenlandic village would weigh more than 12 million tons (11 million tons), Live Science previously reported.
The processes that cause icebergs to detach from the ice sheet are complex and unpredictable, says Brice Noël, lead author of the new study and researcher at the Institute for Marine and Atmospheric Research (IMAU) at Utrecht University in the Netherlands. For the new study, the researchers analyzed the surface of the Greenland ice sheet to determine when melt would surpass snowfall, Noël told Live Science in an email.
“We investigate the sensitivity of the Greenland Ice Sheet’s mass loss to atmospheric warming using a much higher resolution climate model – 1 km – compared to previous work (20 to 100 km),” said Noël. “A higher spatial resolution means that we can now better capture the high mass losses of small glaciers;” this source of melt runoff was previously excluded from models, but contributes significantly to the total mass of ice lost, he explained.
“This will allow us to more accurately predict the future evolution of the Greenland Ice Sheet’s mass loss and its contribution to sea level rise,” said Noël.
Accelerated exposure
The stability of the ice sheet began to slide after the 1990s, as atmospheric warming stimulated meltwater runoff during warm summer months, the study said. Models showed that most of the discharge was produced at the edges of the ice sheet, in a narrow band called the ablation zone. As the Earth warms, it melts the protective layer of tightly compressed snow in the ablation zone. Once this layer is gone, the ice underneath – which is much less reflective than the bright snow – absorbs more sunlight, causing more to melt.
“The accelerated exposure of bare ice increases runoff production and thus surface mass loss,” said Noël.
In a scenario where humans fail to reduce greenhouse gas emissions and current warming continues, Greenland ice loss will cross a new threshold within a few decades – with the ice sheet shrinking every year – according to the study. And that’s a conservative estimate; that threshold could be exceeded even sooner, depending on how much extra ice is lost annually to crumbling icebergs, the authors reported.
It may then take thousands of years for the ice sheet to fully melt, but to prevent Greenland’s ice from disappearing, global warming should be halted or reversed sooner rather than later – “in this century,” said Noël.
The findings were published online Jan. 19 in the journal Geophysical Research Letters.
Originally published on Live Science.