“We find that the 2001-2011 decade was the warmest of the entire 1,000 years,” said Maria Harholt, lead author of the study and a scientist at the Alfred Wegener Institute in Bremerhaven, Germany.
Since warming has continued since then, this finding may underestimate how much climate has changed The highlands of northern and central Greenland have changed. That’s bad news for the planet’s coastlines, as it suggests a long-term melting process is in motion that could eventually yield some significant, if difficult to quantify, portion of Greenland’s total mass into the oceans. In total, Greenland has enough ice to raise sea level by more than 20 feet.
The study stitched temperature records revealed by ice sheets drilled in 2011 and 2012 with records from older and longer cores that reflect temperatures on top of the ice sheet a millennium ago. The youngest ice in these old cores was from 1995, which means they can’t tell us much about today’s temperatures.
Compared to the 20th century, this part of Greenland, the largest north-central part, is now 1.5 degrees Celsius (2.7 degrees Fahrenheit) warmer, with higher rates of melting and water loss from the ice sheet. The sheet — which raises sea level — has increased in tandem with these changes.
The research was published Wednesday in the journal Nature by Harholt and a team of researchers at the Alfred Wegener Institute, the Niels Bohr Institute in Denmark, and the University of Bremen in Germany.
The new research “uses data from within Greenland to push back the instrumental record by 1,000 years, showing unprecedented warming in recent times,” said Isabella Veligogna, a glaciologist at the University of California, Irvine, who was not involved in the research.
“It doesn’t change what we already know about the warming signal in Greenland, the melting and the rapid flow of ice into the ocean, and it’s going to be a challenge to slow it down,” Velikogna said. “Still, this adds momentum to the seriousness of the situation. This is bad, bad news for Greenland and for all of us.
Scientists have suggested that if the air over Greenland warms enough, a feedback loop will set in: the melting of the ice sheet will cause it to collapse to lower altitudes, which will naturally expose it to warmer air, which will cause more melting and collapse. And back and forth.
The fact that this north-central part of Greenland is now 1.5 degrees Celsius warmer than it was in the 1900s does not mean that the ice sheet has reached this feared “tipping point”.
There is recent research recommended Greenland’s dangerous threshold is about 1.5 degrees Celsius, or higher, of global warming — but that’s a different number than the ice sheet’s regional warming. When the planet reaches an average of 1.5C of warming, which could happen as soon as the 2030s, Greenland’s warming will exceed that – and even more than it is now.
Researchers consulted by The Washington Post noted that the northern part of Greenland, where these temperatures were recorded, is known for other factors that could trigger large sea-level rises.
“We should be worried about the warming of northern Greenland, because that area has vast tidewater glaciers and a dozen sleeping giants in the form of an ice stream… To increase Greenland sea level contributionsaid Jason Box, a scientist at the Geological Survey of Denmark and Greenland.
the box Published study Last year suggested that in the current climate, Greenland could already lose out An amount of ice equivalent to nearly a foot of sea level rise. This certainty of sea level rise will worsen as temperatures continue to warm.
Concern is focused on the Northeast Greenland Ice Stream, which carries most of the ice — 12 percent — toward the ocean. It is basically a large slow-moving river that ends in several large glaciers that drain into the Greenland Sea. It already is Getting thinnerAnd the glaciers at its terminus have lost mass—one of them, the Zacharias Istrom, has also lost the frozen shelf that once extended over the ocean.
A recent study It also demonstrates that during the past warm periods in Earth’s relatively recent history (ie, the last 50,000 years or so), this part of Greenland had less ice cover than it does today. In other words, the ice stream extends far from the center of Greenland than can be sustained at the present temperature, and will be Strongly prone to moving backwards and giving up a lot of snow.
“Paleoclimate and modeling studies suggest that Northeast Greenland is vulnerable to climate warming,” said Peeta Xadho, a glaciologist at the University at Buffalo.
In the same year, when the researchers drilled into the ice, the current work is based on — 2012 — Something happened In Greenland. That summer, in July, vast swaths of the ice cap saw surface melt conditions, with cold and high-altitude research taking place.
“This is the first year you’ve noticed melting at these elevations,” Harholt said. “And now it continues.”
An earlier version of this article stated that Niels Bohr’s company was based in Germany. It is in Denmark.
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