If you thought the heat wave-induced melting of half of Greenland’s surface was alarming, wait until you hear the long-term projections for its ice sheet.
Research published last week in Science Advances finds that if emissions continue to climb at their current rate, all of Greenland’s ice could melt by the year 3000, causing sea levels to rise 23 feet and redrawing coastlines around the world. On timescales a bit closer to home, doing nothing to rein in carbon emissions soon could translate to ice losses from Greenland that raise sea levels six inches to a foot by 2100, and 2-5 feet by 2200, permanently inundating low-lying coastal cities and island nations.
The researchers arrived at their grim findings by using supercomputers to run ice sheet models out to the end of the millennium. They looked at three different carbon emissions scenarios, one in which we rapidly ratchet down global carbon emissions, a middle of the road scenario, and a worst-case scenario where we keep burning fossil fuels with abandon, modelling each one 500 times. The models featured improved representation of the flow and speed of outlet glaciers, those frozen rivers that drain ice from Greenland’s interior and dump it out to sea.
The findings show the stark choices we have before us today. Under the optimistic scenario known as RCP 2.6, Greenland is unlikely to lose more than a quarter of its ice over the next millennium, an amount that could still have major consequences for low-lying coastlines by raising sea levels up to six feet. But take the RCP 8.5 road of higher and higher emissions, and we’re looking at future where many of today’s coastal cities are permanently underwater. And this, of course, is just considering melting of Greenland, say nothing of the impacts of ice losses from its much larger cousin at the South Pole and the world’s rapidly-vanishing mountain glaciers.
Penn State glaciologist Richard Alley, who wasn’t involved with the paper, called it “impressive” in an email to us.
“Of particular importance, the authors have used the greatly improved data sets that have been collected over Greenland, and run a good model with quite high resolution to capture what the details in those better data mean for the ice sheet,” Alley said. “No one model is ever the last word, but this is an important contribution, and again highlights that human decisions are important in controlling how much sea-level rise we face in the future.”
Glaciologist Mathieu Morlighem of the University of California, Irvine, who also wasn’t involved, also praised the study’s use of the latest datasets, including data on the topography of Greenland’s bedrock, an important factor controlling how glaciers recede. He found the conclusion that Greenland’s ice will be gone in a millennium if we don’t alter course unsurprising, adding that it was “probably a conservative estimate as the model is not coupled to a climate system and feedbacks are not accounted for.”
This kind of a long-term view may feel esoteric, but 1,000 years is nothing in geologic time, and the reality that one of our planet’s vast ice sheets could be lost that quickly speaks to just how profound of an impact we’re having. But lead study author Andy Aschwanden of the University of Alaska Fairbanks prefers to take a glass-half-full perspective.
“[W]e do not have to follow the RCP 8.5 path and lose the Greenland Ice Sheet,” Aschwanden wrote in an email to us. “Our actions over the next few decades will determine the future.”
Featured image: NASA’s Scientific Visualization Studio