The so-called Doomsday Glacier in Antarctica is losing ice at its fastest rate in 5,500 years, raising concerns about the future of the ice sheet and the possibility of catastrophic sea level rise due to the frozen continent’s melting ice.
The finding comes from a study of prehistoric marine deposits found on the shores around the “doomsday” Thwaites Glacier and neighboring Pine Island Glacier, both located on the West Antarctic Ice Sheet. The startling news? Antarctica’s glacial melt, driven by climate changeis progressing faster than at any time in recorded history, researchers reported June 9 in the journal nature geosciences (opens in new tab).
“These current elevated rates of ice melt may indicate that these vital arteries have been ruptured from the heart of the West Antarctic Ice Sheet, resulting in accelerated flow into the ocean that can be potentially catastrophic for future global sea levels in a warming world,” co -Author Dylan Rood, geoscientist at Imperial College London, said in a statement.
“Is it too late to stop the bleeding?” asked Rood.
As one of Antarctic fastest melting glacier, Thwaites has earned the nickname”Doomsday Glacier.“Since the 1980s, Thwaites has lost an estimated 595 billion tonnes (540 billion tonnes) of ice, contributing to a 4% rise in global sea levels. Thwaites and its northern neighbor, Pine Island Glacier, cover enormous areas; Thwaites has an area of about 74,130 sq mi (192,000 sq km) (almost the size of Britain) and Pine Island 62,660 sq mi (162,300 sq km).
Because the sea-facing ends of the glaciers are positioned over a bowl-like ocean basin, both glaciers are exposed to currents of warm, dense, salty water underneath. This warm water not only melts the glaciers where they jut into the Amundsen Sea, but also cuts them away from below and loosens them from their main anchor points to the north. In addition, this melt from below weakens glaciers, making them more vulnerable to surface fractures that can spread across the ice sheet and potentially lead to fracturing. If the entire West Antarctic Ice Sheet were to break up and melt at sea, it would raise global sea levels by about 11 feet (3.4 meters).
To compare glacier melt rates today with those of the distant past, scientists looked for clues on Antarctic beaches near where the glaciers meet the ocean. Ice weighs on land, and when some of that frozen weight melted and drained into the sea towards the end of the last Ice Age (about 11,500 years ago), the land recovered, revealing coastlines previously hidden beneath the waves. By measuring the age and elevation of nearly two dozen shorelines, the scientists hoped to find out how quickly the ice disappeared from land before re-encroaching.
The researchers estimated the age of the shorelines by collecting ancient shells and tiny fragments of penguin bones before analyzing the ancient biomatter with radiocarbon dating. This method identifies the age of organic material by measuring the amount of carbon-14, a radioactive isotope of carbon or a variant with a different number of neutrons, found everywhere on Earth and easily ingested by plants and animals. When animals die, they stop accumulating carbon-14 in their tissues and what they’ve already absorbed begins to break down. The half-life of carbon-14 (or the time it takes for half of it to decay) is 5,730 years, and scientists can date animals that died thousands of years ago by measuring the amounts of undecomposed carbon Measure -14 in the remains.
After dating penguin bones and shells from more than 20 different shorelines, the scientists found that the oldest and tallest beach began forming about 5,500 years ago. From that point until about 30 years ago, ice loss exposed shorelines at a rate of about 0.14 inches (3.5 millimeters) per year, the researchers reported. But over the past three decades, the rate of shoreline advance has skyrocketed — up to 40 mm (1.6 inches) per year.
“Although these endangered glaciers have been relatively stable over the past millennia, their current rate of retreat is accelerating and already raising global sea levels,” Rood said.
What this means for the future of Antarctica’s glaciers and ice sheets – and vulnerable coastlines around the globe – is unclear. The researchers’ findings, while alarming, do not address how many times glaciers may have retreated and advanced in recorded history. The scientists hope to find out by drilling through the ice to take rock samples from the underlying landmass that could show if the current rate of melt is reversible, or if the glaciers really have passed a point of no return.
Originally published on Live Science.
https://www.livescience.com/penguin-bones-reveal-secrets-of-ddomsday-glacier Antarctica’s ‘Doomsday Glacier’ is hemorrhaging ice faster than in the past 5,500 years