U.S.-U.K. science armada to target vulnerable Antarctic ice sheet | Science

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U.S.-U.K. science armada to target vulnerable Antarctic ice sheet | Science

Planes, ships, and submersibles: Operating on the Thwaites glacier will require a heavy logistic lift from the United States and the United Kingdom.

Mike Lucibella/U.S. National Science Foundation U.S. Antarctic Program

An armada of 100 scientists will soon be descending on West Antarctica, and understanding the future of global sea levels might depend on what they find. Today, after several years of planning, the U.S. and U.K. science agencies announced the details of a joint $50 million (or more) plan to study the Thwaites glacier, the Antarctic ice sheet most at risk of near-term melting.

The International Thwaites Glacier Collaboration plans to deploy six teams to the remote ice sheet, where they will study it using a host of tools, including instrument-carrying seals and earth-sensing seismographs. The researchers will concentrate their work in the Antarctic summers of 2019–20 and 2020–21. An additional two teams will channel the findings of the field teams into global models.

Overall, the collaboration is the largest joint effort between the two nations in Antarctica since the 1940s. “We’ll see what until now has been inferred playing out right in front of our sensors,” says Ted Scambos, a glaciologist at the National Snow and Ice Data Center in Boulder, Colorado, who is serving as the lead U.S. scientific coordinator.

Over the past decade, thanks to a variety of satellite and aircraft observations and modeling insights—including signs that the glacier’s ice has started thinning and flowing faster toward the ocean—scientists have been paying special attention to Thwaites. It is, they believe, the Antarctic ice sheet most at risk of accelerated melting in the next century, making it the wild card in projections of sea level rise. But its remote location, 1600 kilometers from the nearest research station, has made it inaccessible to scientists seeking to understand these risks up close.

Thwaites, a 182,000-square-kilometer glacier in the Amundsen Sea, acts as a plug, blocking the rest of the West Antarctic Ice Sheet from flowing into the ocean. Melt from the glacier already accounts for 4% of modern sea level rise, an amount that has doubled since the 1990s. Scientists are concerned that if it retreats, it could become unstable, making the collapse of the ice sheet irreversible and ultimately increasing sea levels by 3.3 meters over the span of centuries or millennia.

“It could contribute to sea level in our lifetimes in a large way, in a scale of a meter of sea level rise,” says Sridhar Anandakrishnan, a glacial seismologist at Pennsylvania State University in State College who is co-leading one Thwaites project. “Which is just an unthinkable possibility.”

Over the past decade, the Thwaites glacier has risen to the forefront of scientists’ Antarctic melt concerns.

Jeremy Harbeck

Overall, the U.S. National Science Foundation and the United Kingdom’s Natural Environment Research Council will spend $25 million on the science, with each of the eight teams led by researchers from both countries. Funders expect to spend another $25 million or more on the logistics of moving so much heavy equipment toward the shelf. Several ships will work off the coastline while scientists will be based at the former drilling site of the West Antarctic Ice Sheet Divide ice core, flying from there to their research sites in small airplanes or helicopters.

The scientific teams will focus on what puts Thwaites particularly at risk. Researchers have noticed that shifts in winds seem to be pushing warm, deep ocean waters on to Antarctica’s continental shelf at the base of its glaciers. Thwaites is perched on a ridge that holds these waters back, but beyond that ridge, the land under the glacier slopes downward, creating an inland bowl that is below sea level. But the researchers are uncertain about the composition and slipperiness of that geologic bowl.

One study, co-led by Anandakrishnan, will seek to understand the actual composition of the bowl and a second ridge, 70 kilometers inland, on which the glacier might catch. “In some models [the melting glacier] stabilizes” on that ridge, Anandakrishnan says. “In some it doesn’t.” By detonating explosives on the surface of the ice sheet and using seismic sensors to measure their reflections, his team will tease out whether the rock underlying Thwaites, including this critical ridge, is soft and pliable or hard and crystalline.

Another project will target the warm intruding waters. “We plan to have a pincer movement,” says Karen Heywood, an oceanographer at the University of East Anglia in Norwich, U.K., who will be co-leading the team. One effort will involve drilling sensors through the ice and then driving several autonomous submersibles and gliders toward these stations. Another, starting this year, will involve outfitting 10 seals a year with scientific instruments, using the animals to make routine, repeated studies of the ocean. The technique that should produce a torrent of sustained data. They’ll be running similar measures on the nearby Dotson Ice Shelf, seeking to understand whether differences in the ocean waters explain why Thwaites is retreating so rapidly compared with Dotson.

Scientists also expect to explore the glacier’s grounding zone, planning to drill through 800 meters of ice to observe over several seasons where the triangle of ice, ocean, and rock meet. That will include dropping a new autonomous vehicle, developed by the Georgia Institute of Technology in Atlanta, that can deploy through a borehole and explore the grounding zone—an unprecedented view.

Other projects will seek geological evidence of whether Thwaites has previously retreated and reformed in the past 10,000 years, giving a clue to whether the modern melting threat is truly unprecedented. And another team will examine the glacier’s connections to the broader ice sheet—its shear margins—using radar and seismic reflections to detect whether neighboring ice helps hold it in place or lets it go, like a game of high-stakes red rover.

For now, the researchers are eager to get started. The United States and United Kingdom announced the opportunity almost a year and a half ago and it took some time to come together. This project is expected to launch a new generation of Antarctic researchers and, in the process, might reduce some uncertainty about the future of climate change. “No doubt we’re going to learn something that’s important to refining those predictions,” Scambos says. “This is kind of the missing piece right now.”

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