New research suggests that the Antarctic Ice Sheet in the past was more unstable than previously thought and was at times close to collapse.
The findings raise concerns that in warmer climates, exposing the land beneath the ice sheet as it retracts will increase Antarctica rainfall and potentially trigger a process that further accelerates ice loss.
The research is based on climate modeling and data comparisons for the Middle Miocene (13-17 million years ago) when the atmospheric carbon dioxide and global temperature reached similar levels predicted by the end of the century.
The study was conducted by the Met Office, the University of Exeter, Bristol, Cardiff and Stockholm, NORCE and the Bjerknes Center for Climate Research.
“As the ice sheet melts, the new exposed ground below reflects less light and the temperature in the area warms up,” said lead author Dr. Catherine Bradshaw from the Met Office and Global Systems Institute at the University of Exeter. say
“This can drastically change weather patterns.
“With the huge ice sheets on the continent like we have today, Antarctic winds tend to blow from the continent to the sea.
“However, if the continent is warmer, this can be reversed, with winds from cooler seas to warmer land, just as we see with monsoons around the world.
“That would cause more rain in the Antarctic, bringing more fresh water into the sea.
“Fresh water is less dense than salt water, so it can sit on the surface of the sea instead of sinking and circulating like salt water.
“This effectively disrupts the connection between the deep and subsurface oceans, causing warm water to accumulate at depths.”
The study suggests that processes resulting from increasing rainfall will reduce the ability of the climate system to maintain large Antarctic ice sheets.
“Basically, if more Antarctica land was revealed, massive ice sheet reform would be more difficult, and without a good orbital position in Middle Myocene playing a role, perhaps the ice sheet would collapse in time. That, ”Dr. Bradshaw said.
During the warm Middle Ages, unusual swings in deep sea temperatures were recorded.
Studies show that fluctuations in ice-covered areas are a key factor in the dramatic changes in deep sea temperatures. Ice volume fluctuations were found to be much less important.
Variations in the Earth’s position relative to the Sun cause the ice sheet to move and reverse, and this changing weather pattern creates a process that can accelerate or accelerate ice loss or increase.
Rain on the ice sheet can cause fractures, melting surfaces and excess fresh water flowing off the continent, which, in turn, could raise deep-sea temperatures that could affect the Antarctic ice from below.
The new study suggests that the Antarctic ice sheet significantly reversed during the middle meocene and then stabilized when the warm period ended.
Associate Professor Agatha de Bourget, a co-author from the University of Stockholm, said: “As the weather in the middle of meocene cools, the link we found between ice sheet areas and deep sea temperatures through the hydrological cycle arrived. Finish.
“When Antarctica was fully covered by the ice sheet, the winds would always blow from land to sea, and as a result, rainfall would drop to the snow-like low levels across the continent we see today.”
Petra Langebroek, senior researcher at NORCE and the Bjerknes Center for Climate Research, another co-author, added: “The findings indicate changes in the ocean’s sensitivity to ice sheet dynamics occur as the ice sheet retreat. Revealing the ground previously covered with ice. “
Professor Carrie Lear from Cardiff University, who invented the project for the first time, concluded: “This study suggests that in the warm times about 15 million years ago, the Antarctic myocene was able to advance and Can retreat across continents
“This is a relevant matter. But more research is needed to determine what this means for the long-term future of the modern Antarctic Ice Sheet.
Dr Bradshaw stressed that the conditions at this time were not the same in middle myocene, and the models used in the study did not exclude the effects of the response from the carbon cycle or ice sheet.
Paper published in journals Natural geosciencePrivilege: “Hydrological impact of Antarctic ice-free areas, Middle Myocene, coupled with deep ocean temperatures.”
Modeling the ancient Antarctic ice sheet allows us to glimpse the future of global warming.
Hydrological effects of Miocene’s mid-Antarctic ice-free area coupled with deep ocean temperatures Natural geoscience (2021). FDA: 10.1038 / s41561-021-00745-w
Provided by University of Exeter
Reference: Antarctic ice sheet retreat may cause a chain reaction (2021, May 13) .Retrieved May 14, 2021 from https://phys.org/news/2021-05-antarctic-ice-sheet-retreat-trigger.html.
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