Greenland’s Ice Sheet Weaker Than Expected Due To Climate Change

The ice sheet may be more sensitive to human-induced climate change than previously thought, a new study suggests. Understanding Greenland’s geological history is crucial to predicting rising sea levels due to global warming. The authors say that its ice contains enough water to cause a 23-foot (7-meter) rise in sea level, a risk to every coastal region on Earth.

The Greenland ice sheet is about 2 miles (3.2 kilometers) thick and covers an area three times the size of Texas. It has shrunk in the ancient past. Moderate warming between 374,000 and 424,000 years ago caused the ice sheet to melt. Contributing to a significant sea level rise of about 5 feet, the study shows.

The new study contradicts previous estimates that the Greenland ice sheet has existed for most of the past 2.5 million years. About 416,000 years ago, some of Greenland’s ice melted. Leaving behind an ice-free landscape probably covered in trees and roaming woolly mammoths.

The melt occurred despite lower levels of carbon dioxide in Earth’s atmosphere at the time than they are today. Just 280 parts per million, compared with modern levels of 420 parts per million (and rising). Carbon is a greenhouse gas that easily traps heat in Earth’s atmosphere and is one of the drivers of global warming.

A team of scientists from multiple institutions, including the University of Vermont and Utah State University. It made the findings after studying sediments in long-gone ice cores drilled from the Greenland ice sheet.

“This is really the first solid evidence that a large portion of the Greenland Ice Sheet is disappearing as the weather warms,” ​​Paul Berman. A scientist at the University of Vermont and one of the study leaders said.

Rivers flow between cracks in the ice sheet.

The ice cores were collected during a secret mission in the 1960s. When the U.S. military drilled more than 4,500 feet of ice at Camp Century in northwest Greenland. Their operation was just 800 miles (1,300 kilometers) from the North Pole and about 38 miles (61 kilometers) from the coast.

The expedition recovered a 12-foot (4 m) long tube filled with soil and rocks from under the ice. But it was then placed in a freezer. Fortunately, the sample was discovered again in 2017. Upon re-examination, scientists found that the extracted material contained not only rocks and soil but also leaves and moss.

This plant material suggests ice-free landscapes and possibly even boreal forests existed in Greenland’s recent geological history. The ancient green plants suggest that the ice sheet melted at some point in Earth’s millions of years, but scientists are unsure exactly when.

Iceberg was seen from a distance, with rugged slopes, soil, and snow underneath

Using advanced luminescence techniques and analyzing rare forms of chemical elements, as well as different atomic structures called isotopes. Berman and his team painted a grim picture suggesting that much of Greenland melted more than a million years ago.

“We’ve always thought that the Greenland ice sheet formed about 2.5 million years ago. It’s always been there, and it’s been very stable,” said Tami Ritenour of Utah, a study co-author. University scientists made the same statement.

“Maybe the edges have melted, or maybe they’ve gotten thicker with more snowfall. But they’re not going away, and they’re not flowing.”

Maybe the edges have melted, or they’ve gotten a little thicker as more snow fell, but they’re not going away or melting dramatically. But this paper suggests that’s the case.”

The study shows that the sediments beneath the ice sheet were deposited by flowing water during an ice-free period that coincides with moderate warming in Earth’s history.

This period, called Marine Isotope Phase 11, occurred between about 424,000 and 374,000 years ago. It was a long ice age with temperatures similar to or slightly higher than today.

The result suggests Greenland’s ice is more sensitive to global warming than previously thought. It also suggests there’s a risk of irreversible ice melt.

“Greenland’s past, preserved in twelve feet of frozen soil, predicts a future for the planet that will be warm, wet, and largely ice-free. Unless we can drastically reduce atmospheric carbon dioxide concentrations,” Berman said. ”

The team studied a scintillation signal inside the samples, which is produced by electrons (charged particles) captured when the material was buried.

When rocks and sand are moved by water or wind, they are exposed to sunlight, which “resets” the scintillation signal. This process means the number of captured electrons can act as a primitive “clock,” telling when the sediment was last exposed to sunlight.

The only way these sediments in the core could have seen sunlight was if there was less than a mile (1.6 kilometers) of ice above them. This light is also necessary for plant material in the sample.

Isotopes of beryllium and aluminum found in the quartz also help reveal when these sediments were exposed to the sky. These isotopes are only produced when sediments are at the surface and exposed to cosmic rays. Which are charged particles that flow into the atmosphere outside the solar system.

The ratios of beryllium and other isotopes give scientists an idea of ​​how long the rocks in the sample were exposed. How long they were buried under ice. These ratios show that the sediments in this sample were exposed to the sky. For less than 14,000 years before being deposited under ice. Finding this timeline has narrowed the window of time when this region of Greenland should be ice-free.

Final thoughts

The team estimates the sea level rise was 1.5 to 6 meters (5 to 20 feet), much more than the height of a two-story office building. Of course, the big difference between then and today is the absence of human-caused climate change.

“If we melted just a portion of the Greenland ice sheet, sea levels would rise dramatically,” Ritnoor said. Estimating that sea levels today could rise by tens of feet or meters.

Ritnoor added that this melt would put many urban centers and coastal residents at risk if we look at the coast. “Look at the elevation of New York City, Boston, Miami, and Amsterdam. Look at India and Africa: Most of the world’s population centers are around sea level.”