The world’s largest ice caps may be less at risk of sudden collapse than expected, a new study finds.
The study in Science includes the simulation of the disappearance of the Thwaites Glacier from West Antarctica, one of the largest and most unstable glaciers in the world.
The researchers modeled the collapse of varying heights of ice cliffs, almost vertical formations that occur where glaciers and ice shelves meet the ocean. They discovered that instability does not always lead to rapid disintegration.
“What we found is that over long time scales, ice behaves like a viscous fluid, much like a pancake spreading out in a frying pan,” says Jeremy Bassis, associate professor at climate and space science and engineering at the University of Michigan. “So the ice is expanding and thinning faster than it can fail and that can stabilize the collapse. But if the ice can’t thin out fast enough, then you have the possibility of a rapid glacier collapse. “
Researchers combined the variables of ice breakage and ice flow for the first time, finding that stretching and thinning of ice, as well as the strengthening of trapped chunks of ice, can moderate the effects of l fracture-induced sea ice cliff instability.
The new findings add nuance to a previous theory called sea ice cliff instability, which suggests that if the height of an ice cliff reaches a certain threshold, it can suddenly disintegrate under its own weight in a chain reaction. of ice fractures.
The Thwaites Glacier in Antarctica, sometimes referred to as the “Doomsday Glacier,” is approaching this threshold and could contribute nearly 3 feet to sea level rise in the event of a complete collapse. At 74,000 square miles, it is roughly the size of Florida and is particularly sensitive to climate and ocean changes.
“The ocean is still there, tickling the ice in a very complex way, and we’ve only known for a decade or two how important that is.”
The researchers also found that icebergs that crack and fall from the main glacier in a process known as “iceberg calving” can actually prevent, rather than contribute to, catastrophic collapse. If the chunks of ice get stuck on outcrops on the ocean floor, they can put back pressure on the glacier to help stabilize it.
Bassis notes that even if the glacier does not collapse catastrophically, the exposure of a high cliff could still trigger a retreat of a few kilometers per year, or the length of about 20 football fields, which would result in a important contribution to future sea level rise.
The complete collapse of the Thwaites Glacier?
While it is clear that Thwaites and other glaciers are melting, the speed of their disappearance is of great interest to coastal areas as they develop strategies to adapt and build resilience.
But predicting the retreat of glaciers is an incredibly complex endeavor, as they are affected by the interplay of a myriad of factors – the stress and strain of billions of tons of moving ice, changes in air temperature and of water, and the effects of liquid flow. water on ice, to name a few.
As a result, predictions of the collapse of the Thwaites Glacier range from a few decades to several centuries. The new study, says Bassis, is an important step towards producing accurate and actionable predictions.
“There is no doubt that sea levels are rising and that this will continue for the next several decades,” says Bassis. “But I think this study offers hope that we are not approaching a complete collapse, that there are measures that can ease and stabilize things. And we always have the opportunity to make a difference by making decisions about things like energy emissions – methane and CO.2. “
The fate of the Antarctic and Greenland ice caps
The study results will also be useful in predicting the fate of other glaciers and ice formations in the Arctic and Antarctic, says Anna Crawford of the University of St. Andrews.
“This important information will inform future research on the retreat of the Thwaites Glacier and other large outlet glaciers from the West Antarctic ice sheet that are likely to retreat due to the breaking of ice cliffs and instability. sea ice cliffs, ”she said. “They highlight the conditions that facilitate recoil, demonstrate the terminal’s stabilizing potential, and show how sea ice can actually slow down the collapse process.”
The research team is already working to further refine their models by incorporating additional variables that affect glacial retreat, including how the shapes of individual glaciers affect their stability and the interaction between glacial ice and the liquid ocean that l ‘surrounds, explains Bassis.
“The ocean is still there, sort of tickling the ice in a very complex way, and we’ve only known for a decade or two how important that is,” he says. “But we’re starting to understand that this is the root of a lot of the changes we’re seeing, and I think this will be the next big frontier in our research.”
Additional researchers from the University of Michigan and the University of St. Andrews contributed to the work.
The study is part of the International Thwaites Glacier Collaboration. The DOMINOS project, a component of the International Thwaites Glacier Collaboration, the National Science Foundation and the Natural Environment Research Council funded the work.
Source: University of Michigan