Global warming is spiking in one of the world’s coldest places, atop the 2-mile thick ice sheet in central Greenland, where new research shows that the first decade of the 2000s was clearly the warmest 10 years on record in at least 1,000 years.
The findings, published today in Nature, are based on some of the most detailed ice core sampling ever done in the region, which is a critical part of the planet’s cooling system. By measuring chemical traces in the ice, the scientists were able to determine exact annual temperature readings for the region, and they found that, for the years 2001 to 2011, the temperature in the study area was 1.5 degrees Celsius warmer than the 20th century average .
What makes the new temperature record unique is that it’s based on a consistent record of ice core data, while most other Arctic temperature histories are derived from a combination of measurements from more indirect sources like tree rings, said co-author Thomas Laepple, a climate researcher with the Alfred Wegener Institute in Potsdam, Germany.
The study, he said, is “clear evidence” that the effects of global warming have reached the remote, high-elevation areas of central-north Greenland. Many previous research efforts suggested it’s still hard to distinguish a clear global warming signal in the region against the backdrop of annual and decadal changes driven by regional wind shifts and atmospheric pressure patterns that also affect temperatures.
The scientists also analyzed how the melting of the Greenland Ice Sheet is connected with the warming they measured. The meltwater from the ice is a big contributor to global sea level rise, and they were “amazed” to see how the temperatures around the summit of the 3,200-meter (10,500-foot) elevation ice sheet are “closely connected with Greenland-wide meltwater drainage,” even though most of the melting is along the rim of the ice sheet near the coast, said lead author Maria Hörhold.
The research team found that correlation by matching temperature records from a climate model covering the years from 1871 to 2011 with measurements of ice mass changes from 2002 to 2021 gathered by the international GRACE and GRACE-FO Earth observation missions, which use twinned satellites to make detailed gravity measurements.
The comparison enabled the scientists to convert the temperature variations identified in the ice cores into melting rates for the past 1,000 years, she said. The Greenland Ice Sheet is larger than Alaska, covering about 660,000 square miles, and if it keeps melting at the current pace, it would raise global sea level by about 50 centimeters (20 inches) by 2100, adding to the growing flooding woes in coastal communities. A 2022 study showed that the melting ice sheet will add at least 10 inches of sea level rise by the end of the century, no matter what climate actions are taken in the near future.
The study provides valuable new information that can help people vulnerable to sea level rise adapt in the decades ahead, said Jason Boxa Greenland Ice Sheet expert with the Geological Survey of Denmark and Greenland who was not involved with the research.
“We should be very concerned about North Greenland warming because that region has a dozen sleeping giants in the form of wide tidewater glaciers and an ice stream,” he said. Awakening those giants will “ramp up” Greenland’s contribution to sea level rise. He said the study’s finding of a rapidly steepening trend line reinforces the understanding of how industrialization has driven warming.
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Warming has serious consequences
While warming of 1.5 degrees Celsius may not sound like much in one of the world’s ice boxes, there are other ominous signs of change. In 2012, following what the new study identified as the warmest decade on record in Greenland, there was a super-melt event, with surface melting across about 97 percent of the island’s ice for several days. The National Snow and Ice Data Center called the 2012 melting “intense,” noting that the melt season lasted two months longer than usual, and that for the first time in the satellite record that stretches back to 1979, “the entire ice sheet experienced melt at some point in the season. “
There have been several other extreme melting events since then, and in 2021, there was extensive surface melting during September for the first time on record, showing that the melt season is also getting longer. In that same year, it also rained for the first time ever at the top of the ice sheet. More rain triggers more melting, other recent studies show.
The findings also show that the high temperature on the ice sheet isn’t increasing as fast as it is in the rest of the Arctic, which is warming at three to four times the globally average rate, Box said.
The data shows that the warming from 2001 to 2011 differs from that resulting from natural variations during the past 1,000 years, Laepple, at the Alfred Wegener Institute, said. The team was “surprised” by how distinctly the warming showed against the cyclical fluctuations from year to year and decade to decade, he said. Previous ice cores obtained at similar sites starting in the 1990s, did not indicate clear warming in central-north Greenland.
Laepple said the findings show that the warming in central Greenland has a “dynamic of its own,” distinct from the warming in the rest of the Arctic, because the ice sheet summit is so high that it’s differently affected by regional wind shifts than other parts of the Arctic.
There don’t seem to be any signs the warming is slowing down at the top of the Greenland Ice Sheet, said Ingo Sasgen, another co-author, also with the Alfred Wegener Institute.
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“I would say there’s a lot of fluctuation, but there’s a general warming trend that sort of continues what we’ve seen in the past decade,” he said, noting the clusters of extreme melt years. The findings in one of the coldest places on Earth are cause for concern, he added.
“You’re going and taking these cores in one of the most remote places on earth… you expect that climate change hasn’t sort of influenced this remote area that much,” he said. “And when you do the statistical analysis and find these results that are so far outside of this range of natural variability, I think this was most surprising.”
Research has pointed to increased warming pushing the melting at the fringes of the ice sheet upward toward its summit, he said.
“But then, all of a sudden, you get an ice sheet-wide melt event for a year, or rain,” he said. “And all these things that you feared could happen, maybe in some distant future, all of a sudden you detect them in your ice core.”