Ancient Greenland Cave Sediments Contain Climate Change Warning


An iceberg in western Greenland.

An iceberg in western Greenland.
Photo: Sean Gallup (fake images)

Mounting geological evidence suggests that the Arctic was once much warmer than it is today, which means a big problem as we continue to pump greenhouse gases into the atmosphere with abandon. The latest development is a study published Wednesday in Science Advances, which uses geological cave deposits to deduce that the region was at least 6.3 degrees Fahrenheit (3.5 degrees Celsius) warmer than today just over 500,000 years ago.

To try to understand what the Arctic’s past might have been like, the researchers analyzed a 12-centimeter-thick deposit of calcite they found in a cave in northeast Greenland. Even though things in the Arctic are heating up rapidly, it is still very cold and covered in ice. Calcite needs much warmer and more humid conditions to form than those that exist in the area today. The researchers dated the sample using uranium series and analyzed the oxygen composition of the formation, which was formed by the flow of water.

“Our goal was to produce a paleoclimate record from a time period in the past when the Arctic was warmer and more humid than today, as that knowledge will allow us to improve predictions for the future,” said Gina Moseley, a researcher at the University. from Innsbruck in Austria and the lead author of the article, Earther was told in an email.

While it is difficult to accurately date an old piece of rock, dating the uranium allowed researchers to determine the origin of the deposit to a period between 588,000 and 549,000 years ago. The carbon-13 isotope profile of the sample and oxygen composition also pointed to signs of a warmer and more humid climate. This, Moseley said, marked the first time that cave deposits have been used to give us a record of Greenland’s paleoclimate and reveals important information about what the Arctic might have looked like back then.

Our prior knowledge of Greenland’s historical climate comes from samples taken from the ice sheet that covers the island. This gives us some great information about what Greenland was like when that ice sheet was formed, but it is not very helpful in trying to understand what came. prior to. The ice cores that scientists have are limited to an interglacial warm period of about 130,000 years ago. (Earlier this month, the researchers said that sediment found in the ice core dredgers had plant fossils that suggested Greenland was once warm enough to be ice-free).

“Greenland ice core records are … biased towards cold climates and the possibilities of extending further back into warm periods are limited because the ice sheet does not tend to survive warm periods,” Moseley explained. “The new cave record has allowed us to take advantage of a past warm period beyond the limit of Greenland’s ice cores.”

Bogdan Onac, a geologist at the University of South Florida who was not involved in the study, calls the findings “a great achievement” and “solid and carefully crafted research.” He cautions that more research and samples are needed to fully develop the climate profile initiated by this work.

“This research highlights that there could be a time in Earth’s history where temperatures were higher than today, and that was a natural trend,” he said. “Having those high temperatures means there is likely to be more melting in central Greenland, where the ice sheet is located. More melting means more water in the ocean. “

Finding out as much as possible about the Arctic’s past is of great importance in predicting how its future will be increasingly threatened. Some estimates project that the Greenland ice sheet could raise sea level by 6.1 meters (20 feet) if it melted completely, which, in addition to plaguing coastal cities around the world, would also wreak havoc on ocean currents by injecting huge amounts of fresh water in the ocean. Knowing that Greenland was once much warmer than it was today is naturally concerning considering how we are overloading climate change today with carbon dioxide (the ice sheet is now melting six times faster than in the 1980s).

“We know what is happening in Greenland now,” Onac said. “Imagine temperatures three or four degrees warmer than today, how much more ice would be melting. This study indicates that the [levels of] Greenhouse gases at that time were very low. Today we have a greenhouse [gases] went up a lot. What is going to happen in a couple of centuries or millennia? ”

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