Ice cores, unprecedented in quality and length, retrieved in central Greenland, reconstructed past temperatures in the highest elevations of the massive ice sheet and melting rates.
The results were alarming and pronounced. The most recent decade for available data (2001 to 2011) was the warmest in at least 1000 years, and the region of two-mile-thick ice is now 1.5 celsius warmer than the 20th century. The peer-review findings were from the Alfred Wegener Institute and Helmhlotz Center for Polar and Marine Research and were published in Nature.
Greenland and Antarctica are the world's two refrigerators. And Greenland's has begun to defrost. Greenland plays a critical role in the planet's climate system. The hydrology system of the sheet threatens world coastlines and the North Atlantic circulation patterns.
From the Alfred Wegener Institute news presser:
“The time series we recovered from ice cores now continuously covers more than 1,000 years, from year 1000 to 2011. This data shows that the warming in 2001 to 2011 clearly differs from natural variations during the past 1,000 years. Although grimly expected in the light of global warming, we were surprised by how evident this difference really was,” says AWI glaciologist Dr Maria Hörhold, lead author of the study. Together with colleagues from AWI and the University of Copenhagen’s Niels Bohr Institute, she analysed the isotope composition in shallow ice cores gathered in central-north Greenland during dedicated AWI expeditions.
Previous ice cores obtained at co-located sites starting in the 1990s, did not indicate clear warming in central-north Greenland, despite rising global mean temperatures. Part of the reason is substantial natural climate variability in the region.
In addition to the temperature, the team reconstructed the melt production of the ice sheet. Melting has increased substantially in Greenland since the 2000s and now significantly contributes to global sea-level rise. “We were amazed to see how closely temperatures inland are connected to Greenland-wide meltwater drainage – which, after all, occurs in low-elevation areas along the rim of the ice sheet near the coast,” says Maria Hörhold.
In order to quantify this connection between temperatures in high-elevation parts and melting along the edges of the ice sheet, the authors used data from a regional climate model for the years 1871 to 2011 and satellite observations of ice-mass changes for the years 2002 to 2021 from the GRACE/GRACE-FO gravimetry missions. This allowed them to convert the temperature variations identified in the ice cores into melting rates and provide estimates for the past 1,000 years. This represents an important dataset for climate research: better understanding of the melt dynamics of the ice sheet in the past improves projections of related future sea-level rise; reduced uncertainties in projections is one step to help optimize adaptation measures.
Another exciting finding from the study: the climate of the Greenland Ice Sheet is largely decoupled from the rest of the Arctic. This could be shown in comparison with the Arctic-wide temperature reconstruction ‘Arctic 2k’ (https://www.nature.com/articles/sdata201426). Although ‘Arctic 2k’ is an accurate representation of the circumpolar region, it does not reflect the conditions in central Greenland. “Our reconstruction now offers a robust representation of temperature evolution in central Greenland, which has proven to have a dynamic of its own,” says Prof. Thomas Laepple, AWI climate researcher and co-author of the study. “Actually, we had expected the time series to strongly covary with the warming of the Arctic region,” Laepple reports. But the authors have an explanation for these differences: the ice sheet is several kilometres thick; because of its height, Greenland is more affected by atmospheric circulation patterns than other parts of the Arctic. Temperature time series on the Arctic with regional resolution are needed, says Laepple, in order to reliably describe climate change in the Arctic.
Central Greenland was thought to be somewhat isolated from melting. In 2021, that rainfall fell on the summit of Greenland shocking the world with the state of the ice. An event that had never occurred before.
Greenland is melting four times faster than at any time in thousands of years. The planet has been so altered by climate change that Greenland's ice melt is comparable to the end of the last ice age.
Four months ago, Zombie Ice, along the ice sheets margin, which will never grow again due to consistent warming and feedback loops, was identified as contributing ten inches of sea level rise shortly.
The bombshell news out of Greenland comes when climate trolls are swarming Twitter and other social media.
See Meteor Blades diary:
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