Study shows warmest decade in the middle of Greenland in a thousand years | Polarjournal
The north of Greenland has long been considered somewhat more resistant to global warming than the rest of the island, in part because of the remaining multi-year ice cover in the region. But in recent years, the ice here has also been breaking up with increasing frequency, and the ice sheet has shown increased runoff and glacier movement. Now it is clear why. Photo: NASA Earth Observatory

It is now scientifically proven that the Arctic is warming up to four times faster than the rest of the world. But regions exist within the Arctic that were thought to respond less rapidly than other parts. The center and the north of Greenland belong to these regions, or rather “belonged”. Because a study has now shown that these parts of Greenland have warmed much more than previously thought.

A 1.5°C temperature increase from 2001 to 2011 compared to 20th century temperatures in the northern and central areas of Greenland and an associated increase in meltwater runoff from the Greenland Ice Sheet are the results of a study conducted under the direction of the Alfred Wegener Institute AWI in Bremerhaven. Such warming has not been recorded in the last 1,000 years and, according to the research team, shows that global warming had also reached that area of Greenland that was expected to have greater resilience. “We feared this in light of global warming, but the uniqueness and conciseness is unexpected,” explains the study’s lead author, Dr. Maria Hörhold of AWI. The study has now been published in the renowned journal Nature.

The research team, which included scientists from AWI and the Niels Bohr Institute at the University of Copenhagen, examined new ice cores obtained by AWI from re-drilling in the northern and central parts of the Greenland ice sheet. Until now, there was no evidence from cores that the region would behave like the rest of the Arctic, the natural variations were too strong. Furthermore, the ice core data series only went back to the 1990s. So, to get a meaningful temperature reconstruction, the team used a consistent method to analyze the ice cores and focused on measuring stable oxygen isotopes trapped in the ice. This allowed them to eliminate procedural uncertainties. By analyzing a total of 21 standardized processed data sets, the team succeeded in reconstructing a temperature history of the last 1,000 years. “And the warming in the phase between 2001 and 2011 clearly sets itself apart from natural fluctuations over the past 1,000 years,” Dr. Hörhold continues.

In the past, other work had already shown that, especially since the 2000s, the Greenland rim areas in the west, south and east and also other parts of the Arctic had warmed massively. One indication of this was the more frequent meltwater streams and pools at the edges of the ice sheet. The reconstruction of temperatures from the center of the shield now presented shows a clear link between it and the melting processes at the edge. “We were amazed at how closely the temperature in the middle of the ice sheet is related to the Greenland-wide meltwater runoff,” Dr. Hörhold says. And more is likely to come in the future, the authors are sure. “The close relationship between temperature and meltwater runoff means that further warming will lead to increased meltwater runoff, accelerating sea level rise.”

The study also shows that Greenland’s ice sheet has its own climate dynamics and does not react like the rest of the Arctic. The authors see the reason in the altitude of the shield, which rises to over 3,000 meters. Image: Dr Michael Wenger

In the course of the study, the researchers compared the temperature trend of Greenland with that of the Arctic and it was found that it does not follow the general trend, but runs separately. The researchers see the reason for this in the height of the ice sheet, which at over 3,000 meters is higher than many mountains in the Arctic. And this is where the researchers see room for improvement for a more reliable description of warming in Greenland: more cores from different parts of Greenland, all studied with the same method, to create regional temperature time series that include the last decade. Because just in these last ten years the ice sheet made headlines worldwide with several massive melting events, indications of an even faster spreading warming on the second largest ice sheet in the world.

Dr Michael Wenger, PolarJournal

Link to the study: Hörhold et al. (2023) Nature 613 503-507 Modern temperatures in central-north Greenland warmest in past millennium; doi.org/10.1038/s41586-022-05517-z .

Featured image: (C) NASA Earth Observatory

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