Recent efforts using computer modeling to understand how melting Antarctic ice will affect the planet’s oceans have focused on ice sheet geometry, fracturing, and surface melting—processes that could potentially cause or to accelerate ice mass loss. Now, researchers from Stanford University have identified an additional process that could have a similarly significant effect on the ice sheet’s future: the thawing of the bed, known as basal thaw, at the interface of the Earth and the ice sheet above it. The new study identifies areas that are not currently losing large amounts of mass, but could be poised to match some of the biggest contributors to sea-level rise – such as Thwaites Glacier – if they thaw. Antarctica is roughly the size of the United States, and sensitive areas include an area larger than California. The research was published on September 14 at Nature communications. “You can’t necessarily assume that everywhere that’s currently frozen will stay frozen,” said senior study author Dustin Schroeder, an associate professor of geophysics at the Stanford Doerr School of Sustainability. “These areas may be underestimated potential contributors.” Unusual suspects The simulations were based on recent theoretical work showing that core thawing could occur on short time scales. Using numerical ice sheet models, the study authors tested hypotheses about whether the onset of such a thaw could lead to significant ice loss over a 100-year period. They found that triggering the thaw led to mass loss in regions of the ice sheet not normally associated with instability and contributions to sea level on that time scale. “There’s really been little to no work across the continent that looks at the onset of thawing — that transition from frozen ice to ice at the melting point, where a little water in the bed can cause the ice to slide,” he said. lead study author Eliza Dawson, Ph.D. student in geophysics. “We were interested in learning how much of an effect the thaw could have and which areas of the ice sheet were potentially more sensitive.” The researchers modeled temperature changes at the base of Antarctica according to changes in friction caused by the ice sheet sliding over the land beneath it. The simulations revealed that in East Antarctica, which is now considered a relatively stable region compared to West Antarctica, the Enderby-Kemp and George V Land regions would be more sensitive to thawing in their beds. In George V Land, they also highlighted the Wilkes Basin as capable of becoming the leading contributor to sea level if thaw were to occur—a feature comparable in size to the rapidly advancing and potentially unstable Thwaites Glacier in West Antarctica. “The whole community is really focused on Thwaites right now,” said Schroeder, who is also an associate professor of electrical engineering. “But some of the areas that are the usual suspects for large, impactful changes are not the most challenging and dangerous areas in this study.” Temperature matters Due to Antarctica’s location and extreme conditions, information on the ice sheet is sparse. Even less is known about the land beneath its icy facade. “Measuring the bed is a huge effort in these remote places – we have the technology to do it, but you really have to pick the spot and sometimes it takes years, camps and special equipment to do that,” Schroeder said. “It’s difficult and expensive.” To fill in the information gaps, the researchers looked to the physics of how ice slides—how changes in temperature affect how the ice sheet flows and evolves. In subsequent work, the authors plan to develop and apply radar-based analysis approaches to study ice sheet temperature in these critical regions. “You have to know the areas where it matters, and that’s the transformative contribution of Eliza’s paper,” Schroeder said. “It asks these general questions: Does this matter? And if it matters, where? We hope this approach gives the community some priorities about where to look and why, and avoids going down blind alleys.” Sleeping giants? Scientists don’t currently know what forces are most capable of triggering bed thawing in the potentially sensitive areas identified in this study—or how soon they might be able to do so. One possible driver could be changing ocean conditions, which is happening elsewhere in Antarctica. “Warm ocean water doesn’t necessarily reach these areas of East Antarctica like it does in parts of West Antarctica, but it’s close, so there’s a possibility that could change,” Schroeder said. “When you consider recent theoretical work showing that thermal processes in the bed can be easily triggered—even spontaneously—it makes the short-term thawing of the ice sheet seem like a much easier switch to flip than we thought. “ The study shows that measuring, understanding and modeling the temperature at the base of the ice sheets is important to understanding our future, as the biggest uncertainty in sea level rise predictions is the contribution from processes that can change the behavior of large ice sheets such as Greenland and Antarctica. “Further work will be needed to take a closer look at these areas identified by this paper,” Dawson said. “Showing that bed thawing can lead to mass loss from the ice sheet is a process that the community needs to understand and really start to look at — especially in these potentially vulnerable areas.” World’s largest ice sheet more vulnerable to global warming than scientists previously thought More information: Ice mass loss sensitivity to Antarctic ice sheet basal thermal state, Nature communications (2022). DOI: 10.1038/s41467-022-32632-2 Provided by Stanford University Report: Are We Missing a Crucial Element of Sea Level Rise? (2022, September 14) retrieved September 14, 2022 by
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