Study reveals Greenland meltdown and warns of future risk – 07/21/2023 – Environment

A 1.5 km thick ice sheet disappeared in Greenland about 416,000 years ago during a period of moderate natural warming, which caused sea levels to rise to levels that today would be a catastrophe for coastal regions, according to a study published on Thursday (20).

The results contradict the long-held view that the world’s largest island has been an impenetrable ice fortress for the past 2.5 million years, and show instead that it will be much more vulnerable than previously thought to man-made climate change.

“If we want to understand the future, we need to understand the past,” Paul Bierman, a scientist at the University of Vermont, in the United States, and author of the article published in the journal Science, told AFP.

The research was based on an ice core mined 1,390 meters below the surface of northwest Greenland by scientists at Camp Century, a secret military base operating in the 1960s.

The 3.6-metre long tube of earth and rock was forgotten in a freezer until it was rediscovered in 2017.

Scientists were astonished to find that it contained not only sediment but also leaves and moss, irrefutable evidence of an ice-free landscape, perhaps covered in ancient forest where woolly mammoths roamed.

a green greenland

Although the researchers were denied access to the sample for decades, Bierman said this was, in a way, providential, as the most accurate techniques used to date the core are very recent.

Among them, luminescence dating stands out, which allowed scientists to determine the last time sediment buried under the Earth’s surface was exposed to sunlight.

“As the sediment is buried, background radiation from the soil fills in small holes or imperfections of minerals such as quartz or feldspar, accumulating over time what we call a luminescence signal,” explained Drew Christ, co-author of the study.

In a dark room, the scientists cut internal strips of the ice core and exposed them to blue-green or infrared light, releasing the trapped electrons that form a kind of antique clock, showing the last time they were exposed to light, which erases the luminescence signal.

“And the only way to do that at Camp Century is to remove a mile of ice,” explained Tammy Rittenour, another co-author of the research, from Utah State University (USA). “Besides, to have plants, you have to have light.”

Luminescence dating provided the endpoint of the ice-free period, while the starting point came from another technique.

Within the quartz found in the Camp Century core, rare forms — called isotopes — of the elements beryllium and aluminum accumulate when the sediment is exposed to the sky and cosmic rays.

By looking at the ratio between the normal forms of these elements and the rare isotopes, scientists were able to deduce how long the rocks were on the surface and how long they remained buried.

Thus, they found that the sediments were exposed for less than 14,000 years, which means that this was the time that the area was ice-free.

Coastal cities in danger

The core of Camp Century was taken just 1,200 km from the North Pole and his study showed that the entire region would have been covered by vegetation.

This occurred in a period of natural warming called the interglacial period, when temperatures were similar to today, about 1°C to 1.5°C warmer than in the pre-industrial era.

The simulation done by the research team showed that the melting of the ice sheet caused a rise in sea level of between 1.5 and 6 meters at that time.

This suggests that all of the world’s coastal regions, home to many of the world’s populations, are at risk of being submerged in the coming centuries.

Joseph MacGregor, a climate scientist at NASA who was not involved in the study, pointed out that the interglacial period that warmed Greenland lasted tens of thousands of years, much longer than human-induced so far.

However, “we far exceeded the magnitude of the inducing effect of greenhouse gases at that time”, he said.

Levels of carbon dioxide in the atmosphere, a heat-trapping gas, are currently 420 parts per million (ppm), compared with 280 ppm in Greenland’s ice-free period, and will remain in the skies for thousands of years.

“We’re doing a gigantic experiment in the Earth’s atmosphere and we don’t know the results,” commented Bierman. “I don’t see it as ‘My God, the sky is falling’, I see it as a call to action.”