“We found that the decade 2001-2011 was the warmest of the entire 1,000-year period,” said Maria Hörhold, lead author of the study and a scientist at the Alfred Wegener Institute in Bremerhaven, Germany.
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And since warming has only continued since then, the finding is likely an underestimate of how much the climate in the high altitude areas of northern and central Greenland have changed. That’s bad news for the planet’s shorelines, because it suggests a long-term melting process is getting underway that could ultimately deliver a significant, if hard-to-quantify, fraction of Greenland’s total mass to the planets. oceans. Overall, Greenland contains enough ice to raise sea levels by more than 20 feet.
The study matched temperature records revealed by ice cores drilled in 2011 and 2012 with records contained in older, longer cores that reflect temperatures on top of the ice sheet a millennium ago. The youngest ice contained in these older cores was from 1995, meaning they couldn’t tell much about temperatures today.
The work also found that, compared to the 20th century as a whole, this part of Greenland, the huge north-central region, is now 1.5 degrees Celsius (2.7 degrees Fahrenheit) warmer, and that the rate of Melting and loss of water from sheet ice, which raises sea levels, has increased along with these changes.
The research was published in the journal Nature on Wednesday by Hörhold and a group of researchers from the Alfred Wegener Institute, the Neils Bohr Institute in Denmark and the University of Bremen in Germany.
The new research “rolls back the instrument’s record 1,000 years using data from Greenland that show unprecedented warming in the recent period,” said Isabella Velicogna, a glaciologist at the University of California, Irvine who was not involved in the research.
“This doesn’t change what we already knew about the warming signal in Greenland, increased melting and accelerating flow of ice into the ocean, and it will be challenging to slow down,” Velicogna said. “Still, it adds momentum to the gravity of the situation. This is bad, bad news for Greenland and for all of us.”
Scientists have postulated that if the air over Greenland warmed enough, a feedback loop would occur: melting of the ice sheet would cause it to sink to a lower altitude, naturally exposing it to warmer air, making it which would cause more melting and subsidence. Etc.
However, the fact that this north-central part of Greenland is now 1.5 degrees Celsius warmer than it was in the 20th century does not necessarily mean that the ice sheet has reached this dreaded “tipping point.”
Recent research has He suggested that Greenland’s dangerous threshold is at about 1.5 degrees Celsius or more of global warming, but that’s a different figure than regional ice sheet warming. When the globe reaches an average of 1.5°C of warming, which could happen as early as the 2030s, Greenland’s warming will likely be even greater than that, and greater than it is now.
The researchers consulted by The Washington Post also highlighted that the northern region of Greenland, where these temperatures have been recorded, is known for other reasons to have the potential to trigger a large rise in sea level.
“We should be concerned about the warming of northern Greenland because that region has a dozen sleeping giants in the form of wide tidal glaciers and an ice stream… that will wake up increase Greenland’s sea level contributionsaid Jason Box, a scientist with the Geological Survey of Denmark and Greenland.
Cash register published research last year suggesting that in the current climate, Greenland is already destined to lose an amount of ice equivalent to nearly a foot of sea level rise. This committed sea level rise will only get worse as temperatures continue to warm.
Concern centers on the Northeast Greenland Ice Stream, which funnels a significant portion, 12 percent, of the ice sheet out to sea. It is essentially a massive, slow-moving river that ends in several very large glaciers that spill into the Greenland Sea. it is already losing weightand the glaciers at their end point have lost mass; one of them, the Zachariae Isstrom, has also lost its frozen shelf that once spanned the ocean.
recent research has also shown that in past warm periods within Earth’s relatively recent history (i.e., the last 50,000 years or so), this part of Greenland has often had less ice than it does today. In other words, the ice stream could extend farther from the center of Greenland. that can be sustained at current temperatures, and be strongly prone to moving back and giving up a lot of ice.
“Paleoclimate and modeling studies suggest that northeast Greenland is especially vulnerable to climate warming,” said Beata Csatho, an ice sheet expert at the University at Buffalo.
In the same year that the researchers were drilling the ice cores on which the current work is based, 2012, something striking happened in Greenland. That summer, in July, vast portions of the ice sheet experienced surface melt conditions, even in the cold, high-altitude locations where the research was conducted.
“It was the first year that melting has been observed at these elevations,” Hörhold said. “And now continue.”
An earlier version of this article said that the Neils Bohr Institute is in Germany. He is in Denmark.
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