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Sea level rise caused by crucial ice sheet may be 30% higher



Illustration for an article titled Antarctica's Spring Rock could make sea level rise worse

Photo: Jeremy Harbeck (AP)

Watch out for the world – the ice sheet is coming. A new study says that the complete collapse of a crucial ice sheet in Antarctica could mean that sea levels will rise by another 30% more than scientists currently predict.

The study, published Friday in Science Advances, deals with how melting ice on the ice sheet of West Antarctica will affect the crust below. Current estimates say the ice sheet will increase sea level rise by 10.8 feet (3.3 meters) if it melts completely over the next 1,000 years, but taking the base into effect, this study found could add 1 meter to current forecasts. Moreover, the models used by researchers show that forecasts of sea level rise from the ice sheet at the end of this century may actually be 20% higher due to this major effect.

“Any published forecast of sea level rise due to melting ice cover in West Antarctica, which is based on climate modeling, whether the forecast extends to the end of this century or longer in the future, will have to be revised upwards, because of their work, “said Jerry Mitrovica, a geophysicist at Harvard University and author of the newspaper, in a press release. “Everyone.”

The rock that underlies the ice sheet of West Antarctica is below sea level, which means it is particularly sensitive to warm ocean currents. How this water can be buried under the ice is one of the biggest questions as we consider what could happen to sea levels as the planet continues to warm.

“Future changes in the West Antarctic ice sheet are the biggest uncertainty in forecasts of sea level rise,” wrote Robert Larter, a marine geophysicist from the British Antarctic Survey who was not involved in the survey. “Other contributions to sea level change (thermal expansion of the ocean, melting of mountain glaciers and ice caps and ice loss from Greenland) can be estimated with less uncertainty. The difficulty in predicting future changes in WAIS is that most of its bed is below sea level, and much of the bed goes deeper as you enter the ice sheet. “

Scientists believe that warm ocean currents are making the underwater bed on the ice sheet increasingly unstable. This instability can create feedback when the top of the sheet begins to melt, creating what Larter calls a “point of no return” for the ice sheet. “However, because in the history of modern science we have never been able to observe a retreat of the sea ice roof, we do not have good observational data to determine how strong the feedback is and how quickly the retreat can continue,” he continued. he.

One big factor in how this collapse can affect us is the surprising fact that the earth’s crust is beneath the ice sheets themselves. As the ice sheet melts and the weight of the ice decreases, the rock base will emerge as a mattress once you get out of bed. In the case of the ice sheet of West Antarctica, because its base is below sea level, the rising crust will take up more space in the ocean.

“This will reduce the amount of water storage space, which will lead to further sea level rise over thousands of years,” wrote Bethan Davis, a researcher on the glacier at King Holloway University in London, who was not involved in the study. .

It is this connection that is narrowed by the specific study: to what extent this rock base, and not the melting ice itself, can cause sea levels to rise. The base under the ice sheet, the study said, is a type of low-viscosity mantle that will “bounce quickly” as the ice melts. The authors of the study write that previous work has considered that this main effect is “small and appears slowly.” However, their models show that it can make a significant contribution to the influence of sea level from the melting of a particular ice sheet. In examining how the earth’s crust will react to melting ice, Davis said this particular study addresses a crucial figure in the overall impact of the ice sheet.

“One uncertainty in predicting the future is how the Earth’s lithosphere will respond to the glacier recession,” she wrote. “We are constantly trying to improve this aspect of glacier dynamics. Using a new model and applying it for a long time, [the study authors] study a hitherto unexplored aspect of the long-term evolution of the glacier. “

He later speculated that the large increase found in the study compared to previous estimates of sea level rise could simply mean that scientists from different disciplines were finally talking to each other.

“This result stems from the integrated modeling of ice sheets and solid Earth, studied areas that have traditionally been separate areas of glaciologists and geologists,” he said. “Over the last few decades, scientists have become increasingly aware that in order to solve very important environmental scientific issues, we need to work in different disciplines, and a concrete example of this is the realization that the characteristics and response of solid Earth under ice sheets are very important. will change. “

While scientists have built increasingly reliable models to investigate what could happen to glaciers and ice, this study shows how much more we have to learn about what we do as the planet continues to warm and enter unexplored territory. And it’s not really a great place.


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