A crucial threat to rising seas may have been underestimated


Stanford researchers have identified an additional process that could have a significant effect on the melting of the Antarctic ice sheet and the rise in sea level.

They refer to the melting of the bed, known as basal melting, at the interface of the earth and the kilometer-thick ice sheet above it.

The new study identifies areas of the ice sheet 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 were to thaw. Antarctica is about the size of the United States, and the susceptible regions comprise an area larger than California. The research was published in Nature Communications.

“You cannot necessarily assume that everything that is currently frozen will remain frozen,” he said. it’s a statement the study’s lead author, Dustin Schroeder, an associate professor of geophysics. “These regions may be underestimated potential contributors.”

The simulations were based on recent theoretical work showing that basal melting could occur on short time scales. Using numerical ice sheet models, the study co-authors tested hypotheses about whether the onset of such melting could lead to significant ice loss within a 100-year period. They found that triggering melting caused mass loss in regions of the ice sheet. which are generally not associated with instability and sea level contributions on that time scale.

“There really has been little to no work at the continental level looking at the onset of melting, that transition from frozen ice to ice at the melting point, where a little bit of water in the bed can make the ice slide,” said study lead author Eliza Dawson, a geophysics doctoral student. “We were interested in how big the effect of melting might be and which regions of the ice sheet were potentially most susceptible.”

The researchers modeled temperature changes at the base of Antarctica based on changes in friction caused by the ice sheet sliding on the land below it. The simulations revealed that in East Antarctica, which is currently considered a relatively stable region compared to West Antarctica, the Enderby-Kemp and George V Land areas would be more sensitive to melting of their beds. Within George V Land, they also highlighted that the Wilkes Basin is capable of becoming a leading contributor to sea level should a melt occur, a feature comparable in size to the rapidly evolving and likely unstable Thwaites Glacier in West Antarctica.

“The whole community is really focusing on Thwaites right now”said Schroeder, who is also an associate professor of electrical engineering. “But some of the regions that are the usual suspects for large and shocking changes are not the most provocative and shocking areas in this study.”

Due to the location and extreme conditions of Antarctica, information on the ice sheet is scarce. Even less is known about the land beneath its frozen facade.

“Measuring the bed is a huge effort in these remote places; we have the technology to do it, but you really need to pick the spot, and sometimes it takes years, camps and special equipment to do it,” Schroeder said. “It’s difficult and expensive.”

To fill in the information gaps, the researchers drew on the physics of how ice slides: how changes in temperature affect the way the ice sheet flows and evolves. In follow-up work, the authors plan to develop and apply radar-based analysis approaches to study ice sheet bed temperature in these critical areas.

Scientists currently do not know what forces are most capable of triggering bed thaw in the potentially susceptible regions identified in this study, or how soon they may do so. One possible driver could be changing ocean conditions, which is the case in other parts of Antarctica.

“Warm ocean water doesn’t necessarily reach these regions of East Antarctica like it does parts of West Antarctica, but it’s close by, so there’s a chance that could change,” Schroeder said. “When considering recent theoretical work showing that thermal processes in the bed can be easily triggered, even spontaneous, makes short-term thawing of the ice sheet bed 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 ice sheets is important to understanding our future, as the greatest uncertainty in sea level rise projections is the contribution of processes that can change the behavior of massive ice sheets like Greenland and Antarctica.

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