The increase in geological evidence suggests that the Arctic was once much warmer than it is today, which means big problems as we continue to pump greenhouse gases into the atmosphere with abandonment. The latest development is one to study published Wednesday in Science Advances, which uses geological deposits from caves to deduce that the region was at least 3.5 degrees Celsius (6.3 degrees Fahrenheit) warmer than it is today just over 500,000 years ago.
To try to understand what the Arctic past might have been like, researchers analyzed a 4.73-inch-thick (12-centimeter-thick) calcite mineral deposit they found in a cave in northeast Greenland. Even though things in the Arctic heat up quickly, they are still largely cold and covered in ice. Calcite needs much warmer, wetter conditions to form than those currently in the area. The researchers dated the sample by dating uranium series and analyzed the oxygen composition of the formation, which was formed by flowing water.
Gina Moseley, a researcher at the University of Innsbruck in Austria and the lead author of the paper, told Earther in an email.
Although it is difficult to accurately date a piece of old rock, dating with uranium allowed researchers to identify the origin of the site in 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, wetter climate. This, Moseley said, meant the first time cave deposits were used to give us a record of Greenland’s paleoclimate and reveals important information about how the Arctic might have been then.
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Our prior knowledge of Greenland’s historic climate comes from samples drawn from the ice sheet that covers the island. This gives us a lot of information about what Greenland was like when that ice sheet formed, but it’s not very helpful to try to figure out what happened. before. The ice cores that scientists have are limited to a warm interglacial period about 130,000 years ago. (Earlier this month, researchers said sediments were found in the dredges of an ice core had plant fossils suggesting that Greenland was once warm enough to leave it free of ice
“Greenland’s ice core records are … skewed towards cold climates and the chances of extending back in time to warm periods are limited because the ice sheet does not tend to survive warm periods,” he said. explain Moseley. “The new record of the caves has allowed us to take advantage of a warm period past beyond the boundary of Greenland’s ice cores.”
Bogdan Onac, a geologist at the University of South Florida who did not participate in the study, considers the results to be “a great success” and “a solid and carefully crafted research.” He warns that more research and samples are needed to fully specify the climate profile initiated by this work.
“This research highlights that you could have times throughout Earth’s history where temperatures were higher than they are today, and that was a natural trend,” he said. “Having these high temperatures means there’s more melting in the central part of Greenland, where the ice sheet is. More melting means more water in the ocean.”
Finding out as much as possible about the Arctic past is of great importance in predicting how your future may be increasingly in jeopardy. Some estimates project that the Greenland ice sheet could raise sea level by 6.1 meters if it melted completely, which, in addition to affecting coastal cities around the world, would also wreak havoc on ocean currents injecting huge amounts of fresh water to the sea. Knowing that Greenland used to be much warmer than it was natural is worrying given how we are currently overloading climate change with carbon dioxide (the ice sheet is now melting six times faster than it was in the 1980s).
“We know what’s happening in Greenland now,” Onac said. “Imagine temperatures that were three or four degrees warmer than today, how much ice would be made. This study notes that the [levels of] greenhouse gases at that time were very low. Today we have a greenhouse [gases] it crashed a lot. What will happen in a couple of centuries or millennia? ”