The ice sheets of Greenland are melting, and it may very well be worse than we thought.
A brand new study suggests the ice sheets may very well be way more sensitive to human-driven climate change than previously estimated. Understanding the geological past of Greenland is significant for predicting sea-level rise, because of this of worldwide warming. That is because its ice holds enough water to cause 23 feet (7 meters) of sea-level rise, which is a risk to each coastal region on Earth, the authors state.
Greenland’s ice sheet is about 2 miles (3.2 km) thick and spans an area thrice the scale of Texas. And it’s already shrunk in the traditional past. Between 374,000 years and 424,000 years ago, moderate warming caused the ice sheet to melt, resulting in a dramatic sea-level rise of around five feet, the study shows.
The brand new study contradicts previous estimates that the Greenland ice sheet has endured for many of the last 2.5 million years. The melting of a few of Greenland’s ice around 416,000 years ago left behind an ice-free tundra landscape that will have been covered by trees and roaming woolly mammoths.
The melting also took place despite carbon dioxide levels in Earth’s atmosphere being lower on the time than today: just 280 parts per million (ppm), versus 420 ppm (and rising) in modern times. (Carbon, a greenhouse gas that traps heat easily in Earth’s atmosphere, is considered one of the drivers of worldwide warming.)
The findings were reached by a team of scientists from various institutions, including the University of Vermont and Utah State University, who studied sediment from a long-lost ice core drilled from the Greenland ice sheet.
“It’s really the primary bulletproof evidence that much of the Greenland ice sheet vanished when it got warm,” research co-leader and University of Vermont scientist Paul Bierman said in a press release.
The ice core was collected during a secret mission within the Nineteen Sixties, when the U.S. Army drilled through greater than 4,500 feet of ice at Camp Century in northwestern Greenland. They were working only 800 miles (1,300 km) from the north pole, and about 38 miles (61 km) inland from the coast.
The mission recovered a 12-foot (4-meter) tube of soil and rock from below the ice, which was then lost in a freezer. Happily, the sample was found again in 2017. Upon reinspection, scientists found the cored material not only had rock and soil, however it also harbored leaves and moss.
This plant material suggested the existence of an ice-free landscape in Greenland’s recent geological past, and maybe even the presence of a boreal forest. Ancient greenery suggests that the ice sheet had melted in some unspecified time in the future previously million years of Earth’s history, but scientists weren’t sure when.
Using advanced luminescence technology and the evaluation of rare types of chemical elements, with differing atomic compositions called isotopes, Bierman and the team developed a stark picture that implies large parts of Greenland melted way more recently than 1,000,000 years ago.
“We had all the time assumed that the Greenland ice sheet formed about two and a half million years ago—and has just been there this whole time and that it’s very stable,” research co-author and Utah State University scientist Tammy Rittenour said in the identical statement.
“Possibly the sides melted, or with more snowfall, it got a bit fatter—however it doesn’t go away, and it doesn’t dramatically melt back. But this paper shows that it did.”
The research shows that sediment below the ice sheet was deposited by flowing water during an ice-free period that coincided with a moderate warming period in Earth’s history.
The period, called Marine Isotope Stage 11, took place roughly 424,000 to 374,000 years ago. It was a protracted interglacial period, with temperatures much like or barely warmer than those today.
This finding suggests that Greenland ice is way more sensitive to warming than previously predicted. It also suggests the danger of an irreversible melting of ice.
“Greenland’s past, preserved in twelve feet of frozen soil, suggests a warm, wet, and largely ice-free future for planet Earth unless we will dramatically lower the concentration of carbon dioxide within the atmosphere,” Bierman said.
The team investigated something throughout the sample called a luminescence signal, which arises as the results of trapped electrons (charged particles) when materials are buried.
As pieces of rock and sand are transported because of this of water or the wind, they’re exposed to sunlight, which “resets” that luminescence signal. This process implies that the variety of trapped electrons can function a rudimentary “clock” that shows when the sediments were last exposed to the sun.
The one way these sediments on this core could have seen sunlight could be if there was lower than a mile (1.6 km) of ice excessive of them. That light would even have been essential for the plant matter within the sample.
Also serving to disclose when these sediments were exposed to the sky were isotopes of beryllium and aluminum, in quartz. These isotopes are only created when sediment is on the surface and exposed to cosmic rays, that are charged particles that stream into the atmosphere from beyond the solar system.
Ratios of beryllium and other isotopes gave the scientists an idea of how long rocks within the sample were exposed, and the way long they were buried under layers of ice. The ratios revealed that sediments on this sample were exposed to the sky lower than 14,000 years before being deposited under the ice. Finding this timeline narrowed down the window when this area of Greenland will need to have been ice-free.
The ocean-level rise triggered is estimated by the team to have been between 5 feet and 20 feet (1.5 meters to six meters), a relative melt of a two-floor office constructing. After all, the numerous difference between then and today is that there was no climate change made by humans.
“If we melt just portions of the Greenland ice sheet, the ocean level rises dramatically,” Rittenour said, estimating that modern-day sea rise will probably go by tens of feet or meters.
the coast, Rittenour added, such a melt would put many urban centers and seaside populations in danger. “Take a look at the elevation of Latest York City, Boston, Miami, and Amsterdam. Take a look at India and Africa—most global population centers are near sea level.”
The team’s results were published July 20 within the journal Science.