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Greenland’s ice sheets are being melted by both rising air and ocean temperatures




Photo: Pixabay/JChristophe_André

Scientists have warned that due to warming atmospheric temperatures, Greenland’s ice sheets are melting rapidly and may even soon reach a point of no return.

Now, new research suggests the situation is particularly dire because Greenland’s ice sheets are exposed to both rising air temperatures and warming ocean waters, with the former amplifying the effects of the latter.

“[T]Through the release of meltwater from the surface of the ice sheet into the ocean, which excites the ocean circulation near the glaciers and, in turn, the transfer of heat from the ocean to the ice, a warming of the atmosphere may increase underwater melting even in the absence of ocean warming,” note the scientists behind a study published in the journal nature geoscience.

The researchers, who are from the University of Edinburgh in Scotland and the University of California, San Diego, in the United States, reconstructed the rate of underwater melting of Greenland’s marine glaciers between 1979 and 2018 to estimate the resulting loss of ice in the sheet, which covers more than 650,000 square miles in all.

They concluded that in the southern part of Greenland “submarine melt variability was indeed governed by the ocean, but, in contrast, the atmosphere dominated in the northwest”, as they put it. .

“At the scale of the ice sheet, the atmosphere plays a primary role in controlling submarine melting and the resulting dynamic mass loss. Our results challenge the attribution of dynamic mass loss to ocean warming alone and show that a warming atmosphere amplified the impact of the ocean on the Greenland Ice Sheet,” explain the authors. scientists.

Simply put, the process is analogous to ice cubes melting faster when placed in a stirred drink, as the combination of hotter liquid and movement impacts the melting of the ice cubes.

“In Greenland, amplification occurs when warm air temperatures melt the surface of the ice sheet, generating meltwater. Meltwater flowing into the ocean creates turbulence that makes melting more heat on the edges of the ice cap submerged in the ocean [in] so-called underwater fusion,” they explain.

Rising air temperatures have had an impact almost as marked as rising ocean temperatures on submarine melting, although the effect has not been observed at the same rate in various regions around Greenland. While ocean temperature is the main factor driving underwater ice melt in south and west-central Greenland, atmospheric warming is equally damaging in north-west Greenland. ‘island.

The edges of the Greenland Ice Sheet are melting faster when the ocean is warmer, and because rising air temperatures effectively cause the ocean to churn near the ice sheet, this causes the ice sheet to melt faster. the ice cap by the ocean.

“This sadly adds to the overwhelming body of evidence showing the sensitivity of the Greenland Ice Sheet to climate change, hence the need for urgent action to reduce greenhouse gas emissions,” Donald notes. Slater, a scientist from the School of GeoSciences at the University of Edinburgh who conducted the research.

“The results suggest that if the atmosphere had not warmed since 1979, Greenland’s glacier retreat, driven by underwater melting, could have been halved in the northwest region and a third in the whole of Greenland,” the scientists said. conclude.