Are we missing a critical component of sea level rise?

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Recent efforts using computer modeling to understand how melting ice in Antarctica affects the planet’s oceans has focused on ice sheet geometry, breakage, and surface melt — processes that can lead to or accelerate ice sheet mass loss. Now, researchers from Stanford University have identified an additional process that could have a similarly important impact on the future of the ice sheet: melting ice, known as basal melt, at the Earth’s interface and a layer of ice miles thick above it.

The new study identifies areas that do not currently lose significant amounts of mass but could fit in with some of the biggest contributors to sea level rise – such as the Thwaites Glacier – if they were thawed. Antarctica is roughly the size of the United States, and vulnerable areas include an area larger than California. The research was published on September 14 in Nature Connections.

“You can’t necessarily assume that every place that is currently frozen will remain frozen,” said study senior author Dustin Schroeder, associate professor of geophysics at the Stanford Doyr School of Sustainability. “These areas of potential contributors may be underestimated.”

Unusual suspects

The simulations build on recent theoretical work showing that primary melting can occur over short time scales. Using numerical models of the ice sheets, the study’s co-authors tested hypotheses about whether the onset of ice melt could lead to significant ice loss over a 100-year period. They found that melt release led to mass loss in areas of the ice sheet that is not normally associated with instability and sea level contributions in that time scale.

He said, “There has been little, or no, work on the continent, looking at the onset of thawing – this transition from frozen ice to ice at melting point, where a little bit of water on the bottom of the ice can cause it to slide.” . Study lead author Elisa Dawson, PhD. Student in geophysics. “We were interested to see how much of an impact the thaw could have and what areas of the ice sheet are likely to be most vulnerable to injury.”

The researchers modeled temperature changes at the base of Antarctica according to shifts in friction caused by the ice sheet sliding over the land beneath. The simulations revealed that in East Antarctica, which is currently a relatively stable region compared to West Antarctica, the Enderby Kemp and George V Land regions would be more sensitive to melting in their beds. Within George V Land, they also highlighted the Wilkes Basin as having the potential to become a leading contributor to sea level if ice melt occurred—a feature comparable in size to the rapid and likely unstable development of the Thwaites Glacier in West Antarctica.

“The whole community is really focused on Thwaites right now,” said Schroeder, who is also an assistant professor of electrical engineering. “But some of the areas that are the usual suspects of significant and impactful changes are not the most provocative and influential areas in this study.”

The temperature is important

Because of Antarctica’s location and harsh conditions, information about the ice cover is scarce. Little is known about the land beneath its frozen facade.

“Measuring a 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, field camps, and special equipment to do it,” Schroeder said. “It is difficult and expensive.”

To fill in the information gaps, the researchers relied on the physics of how ice slides — how changes in temperature affect the way ice sheets flow and develop. In follow-up work, the authors plan to develop and apply radar-based analysis approaches to study ice sheet temperature in these critical regions.

“You need to know the areas that interest you, and that is the transformative contribution of the Elisa paper,” Schroeder said. “It asks these general questions: Does it matter? And if it matters, where? Hopefully this approach will give the community some priority as to where to look and why, and avoid going down blind alleys.”

sleeping giants?

Scientists do not currently know what forces are most capable of causing bed dissolution in the potentially vulnerable areas identified in this study – or when they will be able to do so. One possible driver could be changing ocean conditions, as they are elsewhere in Antarctica.

“The warm ocean waters don’t necessarily reach these areas of East Antarctica as they do in parts of West Antarctica, but they are close, so there is a possibility that could change,” Schroeder said. “When you think about recent theoretical work showing that thermal processes in the bed can be easily activated – even spontaneously – it makes near-term thaw seem like a much easier switch 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 greatest uncertainty in the world. sea ​​level rise The projections are a contribution from processes that can alter the behavior of massive ice sheets such as Greenland and Antarctica.

“Follow-up work will be needed to take a closer look at these areas identified in this paper,” Dawson said. “Showing that melting in the bed can lead to mass loss from the ice sheet is a process that the community needs to understand and really start looking at – especially in these potentially vulnerable areas.”

The world’s largest ice sheet is more vulnerable to global warming than scientists previously thought

more information:
The sensitivity of ice mass loss to the basal thermal state of the Antarctic ice sheet, Nature Connections (2022). DOI: 10.1038 / s41467-022-32632-2

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