Sledgehammering the South Pole: What It’s Like to Do Fieldwork in Antarctica
(Editor’s note: Zhongwen Zhan recently delivered a Watson Lecture on his work in Antarctica. That video is embedded below.)
Zhongwen Zhan got illuminating data—and a touch of frostbite—during his time on the icy continent.
By Andrew Moseman
Zhongwen Zhan (PhD ’14) simply couldn’t wait. When he saw the first readings from his Antarctic experiment, he had to run out into the blistering cold and sledgehammer the ice.
Zhongwen Zhan getting read to embark on his flight to Antarctica.
Zhan, a Caltech professor of geophysics, specializes in turning underground telecommunications networks into earthquake detectors. In Pasadena, for example, he figured out how unused strands of optical fiber in the city’s telecommunication cables could detect seismic waves and do the work of 5,000 sensors. In January 2023, he traveled to the end of the earth for a National Science Foundation–funded project to prove a similar approach could work in Antarctica. The goal: to listen for seismic waves in the ice that could signify “icequakes” and other seismic activity, which could help scientists understand the physics and deep structure of glaciers and ice sheets, and how the polar regions are changing under ongoing climate change. Zhan also hopes to use these waves to study the hidden base layers of the ice.
He knew that the United States’ Amundsen-Scott Station, located at the South Pole, had spare fibers in the telecommunications lines that formerly connected it to a nearby geophysical research station. In the 20 years since that station had been relocated, the cable had become buried in 10 meters of new ice. Still, Zhan thought that if the cable remained in good enough condition, it could still be possible to use it to detect seismic waves traveling through the ice, just as he typically does in California and with cables running under the sea to detect earthquakes.
“By converting cable into a sensor, you have a very dense array of sensors that you couldn't deploy otherwise,” Zhan says. “I felt like this must be a very good idea for studying glaciers.”
To find out if that was indeed the case, he and his fellow researchers would need to create their own vibrations on the surface of the ice and see how well the repurposed telecom lines could pick up the resulting seismic waves. Hence the thumping. On their long journey, first to the McMurdo Station on Antarctica’s coast and finally to the South Pole deep in the heart of the frozen continent, Zhan and colleagues lugged an old-fashioned 8 kilogram sledgehammer as well as a 40 kg piston-powered mechanical hammer mounted to the back of a snowplow that could pound the frozen surface. Once he saw that Amundsen-Scott’s old telecom lines had enough remaining strands of fiber intact for his experiment, he couldn’t wait to get started—even though the plow-mounted hammer wasn’t ready yet.
“I grabbed my sledgehammer and ran outside,” Zhan says. “I had to do some tests, and I hammered there about 40 times.”
The findings shook him: Because the South Pole is such a quiet place, the detection instrument Zhan had linked to the old buried telecom lines could detect seismic waves from a sledgehammer strike from more than a kilometer away, 10 to 20 times farther than would be possible in noisy California. And once the mechanical hammer was up and running, its signal could be heard 10 km away. (The team also brought a blasting gun that uses an explosive shell to see how far its waves might travel. However, during their tests on the ice, it turned out that the shell used up its energy blowing a hole in the snow rather than sending waves many kilometers in all directions.)
These early findings were actually a long time coming. Zhan’s trip had been delayed multiple years because of the COVID-19 pandemic. When he finally got the all-clear to travel last year, he began the frenzied process of shipping all the necessary science equipment to Antarctica and preparing himself to work in the extreme environment. Still, Zhan says, nothing—not even all the excellent cold-weather gear he packed—quite prepared him for the experience of conducting field work in such a frigid place. He even got a small spot of frostbite on his face his first day working outdoors at the pole.
“Even with all those preparations, when you first go there, it still is amazing how cold it is,” he says. “Especially your face. Whenever it’s exposed, it just feels so cold, and the air coming out immediately freezes on [your glasses]. There’s no way for you to wipe it off.”
Back in the Northern Hemisphere, Zhan is still receiving readings from the detector his team left behind. It will continue to gather data throughout the Antarctic winter, which is too inhospitable for human scientists to hang around. For Zhan, fieldwork at the South Pole certainly gave him a new understanding of the meaning of cold.
“When we first arrived at McMurdo station on the edge of Antarctica, which is only -5 to -10 degrees Celsius, we were like, ‘This is so cold,’” he says. “But when we came back from South Pole, we thought, ‘Oh, this is summer.’”
Editor’s note: While the article states that the Antarctic winter is too inhospitable for research, some scientists do stay there year-round inside the shelter of places like McMurdo.