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Weisen Shen

From left, graduate students Thomas Reilly and Hanxiao Wu with Weisen Shen. Wu and Shen are holding two of the 183 sensors they will place in the Antarctic. The team is shipping the sensors in the black container, which will travel through Port Hueneme, California and New Zealand before reaching the South Pole. Photo by Maeve McCarthy/ Angela Gruo

By Daniel Dunaief

While it’s easy to see and study materials in valleys or on the tops of bare mountains, it’s much more difficult to know what’s beneath 2.7 kilometers of ice. Turns out, that kind of question is much more than academic or hypothetical.

At the South Pole, glaciers sit on top of land that never sees the light of day, but that is relevant for the future of cities like Manhattan and Boston.

The solid land beneath glaciers has a strong effect on the movement of the ice sheet, which can impact the melting rate of the ice and sea level change.

Weisen Shen, Assistant Professor in the Department of Geosciences at Stony Brook University, recently received over $625,000 over the course of five years from the National Science Foundation to study the unexplored land beneath the East Antarctic Ice Sheet at the South Pole.

The subglacial water and hydrosystems, together with geology such as sediment or hard rocks, affect the dynamics and contribute to the movement speed of the ice sheet.

Once Shen provides a better understanding of the material beneath the ice, including glacial water, he can follow that up with other researchers to interpret the implications of ice sheet dynamics.

“We can predict better what’s the contribution of the Antarctic ice sheet to the sea level change” which will offer modelers a way to gauge the likely impact of global warming in future decades, he said.

Using seismic data

Starting this November, Shen and graduate students Siyuan Sui, Thomas Reilly and Hanxiao Wu will venture for two months to the South Pole with seismic monitors.

By placing 183 seismic nodes and installing an additional eight broad-band seismic stations, Shen and his team will quantify the seismic properties and, eventually, use them to infer the composition, density and temperature structure of the crust and the uppermost mantle.

The temperature when they place these monitors will be 10 to 30 degrees below 0 degrees Fahrenheit. They will need to do some digging as they deploy these sensors near the surface.

While the South Pole is believed to be geologically stable, signs of sub-glacial melting suggest the crust may bear a higher concentration of highly radioactive elements such as uranium, thorium and potassium.

Those natural elements “produce heat all the time,” said Shen. 

The process and analysis of seismic waves works in the same way it would for the study of a prism. Looking at the refraction of light that enters and leaves the prism from various angles can help researchers differentiate light with different frequencies, revealing clues about the structure and composition of the prism.

Earth materials, meanwhile will also cause a differentiation in the speed of surface waves according to their frequencies. The differentiation in speeds is called “dispersion,” which Shen and his team will use to quantify the seismic properties. The area has enough natural waves that Shen won’t need to generate any man-made energy waves.

“We are carefully monitoring how fast [the seismic energy] travels” to determine the temperature, density and rock type, Shen said.

The water beneath the glacier can act like a slip ’n slide, making it easier for the glacier to move.

Some large lakes in Antarctica, such as Lake Vostok, have been mapped. The depth and contours of sub glacier lakes near the South Pole, however, are still unclear.

“We have to utilize a lot of different methods to study that,” said Shen.

The Stony Brook researcher will collaborate with colleagues to combine his seismic results with other types of data, such as radar, to cross examine the sub ice structures.

The work will involve three years of gathering field data and two years of analysis.

Educational component

In addition to gathering and analyzing data, Shen has added a significant educational component to the study. For the first time, he is bringing along Brentwood High School science teacher Dr. Rebecca Grella, A PhD graduate from Stony Brook University’s Ecology and Evolutionary Biology program, Grella will provide lectures and classes remotely from the field.

In addition to bringing a high school teacher, Shen will fund graduate students at Stony Brook who can help Brentwood students prepare for the Earth Science regents exam.

Shen is working with Kamazima Lwiza, Associate Professor in the School of Marine and Atmospheric Sciences at Stony Brook, to bring Earth Science, including polar science, to schools in New York City and on Long Island with a bus equipped with mobile labs.

Lwiza, who is the Principal Investigator on the EarthBUS project, will work together with Shen to build a course module that includes a 45-minute lecture and exhibition.

Shen feels that the project will help him prepare to better educate students in graduate school, college, and K-12 in the community.

He feels a strong need to help K-12 students in particular with Earth Science.

As for students outside Brentwood, Shen said he has an open door policy in which the lab is receptive to high school and undergraduate students who would like to participate in his research all year long.

Once he collects the first batch of data from the upcoming trip to the South Pole, he will have to do considerable data processing, analysis and interpretation.

While Shen is looking forward to the upcoming field season, he knows he will miss time in his Stony Brook home with his wife Jiayi Xie, and his four-and-a-half year old son Luke and his 1.5 year old son Kai.

“It’s a huge burden for my wife,” Shen said, whose wife is working full time. When he returns, he “hopes to make it up to them.”

Shen believes, however, that the work he is doing is important in the bigger picture, including for his children.

Record high temperatures, which are occurring in the United States and elsewhere this summer, will “definitely have an impact on the dynamics of the ice sheet.” At the same time, the Antarctic ice sheet is at a record low.

“This is concerning and makes [it] more urgent to finish our work there,” he added.

Weisen Shen. Photo by John Griffen/SBU

By Daniel Dunaief

Like so many others during the pandemic, Weisen Shen has had to pivot in his job.

An Assistant Professor in the Department of Geosciences at Stony Brook University, Shen has historically focused his efforts on understanding the geothermal heat flux, or the movement of heat from the core of the Earth, in Antarctica.

Constrained by travel restrictions created by the COVID-19 pandemic, Shen has decided to put his 180 seismometers to good use on Long Island.

“We have seismometers that stay in the basement of our building,” Shen said. “We can’t use them in Antarctica because of the travel ban and other complexities, and we want to make use of them in our community to understand the geology of Long Island.”

Shen is looking for students who might be interested in geology and who might like to plant a seismometer in their backyard, gathering information about how the flow of seismic waves deep beneath their homes and backyards reveals details about the structure, temperature and composition of the land miles below the surface.

Shen, who lives in Syosset, installed a seismometer in his own backyard, which has allowed him to see the signal from the local train station in Sayville. “We seek help from [the local community] to allow us to deploy a seismometer in their back or front yard for a month or so,” Shen said.

Planting a seismometer would involve digging a 15 centimeter by 15 centimeter hole that is 5 inches deep. Shen and his team would cover it. The seismometer wouldn’t need local electricity because it has a lithium battery. 

After about a month, the scientists would dig it out, put dirt back in, and return the backyard to the way it looked prior to taking these measurements.

The machine doesn’t make any noise and does not pick up any sounds from inside people’s homes.

The signal will contribute “to our understanding of the Earth,” Shen explained, including details about the crustal and mantle structure, seismic activities, and the Earth’s vibrations due to civil activities such as the rumbling of trains.

Shen is “more than happy to share data” with the people who host his seismometers. He also expects to produce a research paper based on his studies from Long Island.

He is charging the batteries and testing the instruments and plans to plant them in the field as early as the end of February.

People who would like to participate can reach out to Shen by sending him an email at [email protected]. Please include “Volunteer Long Island Imager” in the subject line.

Recent Antarctica Studies

While Shen is focusing his geothermal expertise on Long Island, he hasn’t abandoned or ignored Antarctica, a region he has focused research efforts on because of the vulnerability of the ice sheet amid climate change. He is also interested in the geothermal structure in the area, which reveals information about its geology and tectonics, which remain mysteries residing below the ice. 

Grounded during the pandemic, Shen spent several months gathering and analyzing considerable available data, hoping to understand what happens deep below the frozen surface.

“We are trying to analyze so-called ‘legacy data’ that has been collected over the past two decades,” he said.

On a fundamental level, Shen is trying to quantify how much heat is coming out through the crust, which includes heat coming from the deeper earth in the mantle and the core as well as within the crust.

Traveling beneath the oceans towards the center of the Earth, which would be considerably hotter and more difficult than 19th century author Jules Verne’s fantastic fictional voyages, would expose people to temperatures that increase, on average, about 10 to 30 degrees celsius per kilometer.

Some of the heat comes from the way the planet formed. In addition, unstable isotopes of potassium, uranium and thorium release heat as they decay, which mostly happens within the Earth’s crust. 

In areas with large ice sheets sitting on top of the land, the geothermal heat can melt some of that ice, creating a layer of water that accelerates the ice sheet movement. Indeed, pulling an ice cube across dry ground takes more energy than dragging that same cube across a wet surface.

Moving ice more rapidly towards the periphery will increase melting which, coupled with climate change, could increase the amount of water in Antarctica, particularly in the western region.

Comparing the two ice melting effects, Shen believes global warming, which is more rapid and has shorter term outcomes, plays a more important role in changing the liquid characteristics of Antarctica than geothermal heating, which is longer term.

In collecting available legacy data, Shen analyzed information from the entire western part of Antarctica, as well as parts of the central and eastern regions.

Using a measure of the geothermal heat flux, Shen found some unexpected results, particularly on Thwaites Glacier, beneath which he found a large area with elevated geothermal heat flux. 

Studying geomagnetic data, he compared their results with the results from geomagnetically derived results. In the future, he will combine the two different methods to improve the assessment. 

In a publication last summer in Geophysical Research Letters, Shen presented a new map of the geothermal heat flux for Antarctica with a new resolution of 100 kilometers by 100 kilometers, which is a much higher resolution than earlier studies, which are typically done at 600 kilometer by 600 kilometer ranges.

In West Antarctica, he found a more modest heat flux, despite the area being more tectonically active.

Finally, a major take of the paper, Shen said, is that the Thwaites glacier has a high geothermal heat flux, which could explain why the ice moves more rapidly and readily.

As for his future work, in addition to exploring the seismology of Long Island, Shen said he would pursue his National Science Foundation grant to look for additional water in the boundary between the ice sheet and the mantle.

He is working on “using high frequency seismic records to look for data,” he said.

Weisen Shen in front of a twin-otter airplane in the Antarctic during the 2017-18 season. Photo by Zhengyang Zhou

By Daniel Dunaief

Ever sit alone in a house and hear noises you can’t explain? Was that the wind, the house settling (whatever that means) or the cat swatting at the string hanging from the blinds?

Those sounds, which are sometimes inexplicable and are called ambient noise, are often hard to trace, even if we walk around the house and listen outside every room.

Weisen Shen
Photo by John Griffin

For Weisen Shen, an assistant professor in the Department of Geosciences at Stony Brook University, ambient noises deep below the Antarctic continent and elsewhere can be and often are clues that unlock mysteries hidden miles below the frozen surface.

A geoscientist who uses computer programs in his research, Shen would like to study the temperature well below the surface. He developed an in-house code to understand and interpret seismic data.

The speed at which Earth rumbling passes from one area to another can indicate the relative temperature of an area. Seismic activity moves more slowly through warmer rocks and moves more rapidly through colder crust, which has a higher rigidity. According to Shen, these temperature readings can help provide a clearer understanding of how much heat is traveling through the surface of the solid Earth into the ice sheet.

Shen traveled to the Ross Ice Shelf in the 2015-16 season and ventured to the South Pole in the 2017-18 season. He is currently seeking funding to go back to the Antartica. Earlier this year, he published an article in the journal Geology in which he found evidence that the lithosphere beneath the Transantarctic Mountains is thinner than expected.

Shen pointed out that seismic properties aren’t just related to temperature: They can help determine the density of the material, the composition and the existence of fluid such as water. He looks for surface geology and other types of geophysical data to detect what is the dominant reason for seismic structure anomalies. He also uses properties other than speed, such as seismic attenuation and amplitude ratios, in his analysis.

This kind of information can also provide an idea of the underlying support for mountain ranges, which get built up and collapse through a lithographic cycling.

As for ambient noises, Shen explained that they can come from ocean fluctuations caused by a hurricane, from human activities or, most commonly, from the bottom of the ocean, where the dynamic ocean wave constantly pushes against the bottom of the earth. By processing the noises in a certain way, he can extract information about the materials through which the noise traveled.

Shen published an article in the Journal of Geophysical Research in which he discussed a noise source in Kyushu Island in the Japanese archipelago. “The noise is so subtle that people’s ears will never catch it,” he said. “By deploying these very accurate seismic sensors, we will be able to monitor and study all the sources of those noises, not just the earthquakes.”

Studying these lower volume, less violent noises is especially helpful in places like Antarctica, which is, Shen said, a “quiet continent,” without a lot of strong seismic activity. He also uses the images of earthquakes that occur elsewhere, which travel less violently and dramatically through Antarctica.

Shen decided to study Antarctica after he earned his doctorate at the University of Colorado at Boulder. “I have this ambition to get to all the continents,” he said. In graduate school he told himself, “If you ever want to get that work done, you have to crack this continent.”

During his postdoctoral work, Shen moved to St. Louis, where he worked at Washington University in the laboratory of Doug Wiens, professor of Earth and planetary sciences.

In addition to conducting research in Antarctica, Shen collaborated with Chen Cai, a graduate student in Wiens’ lab. Together with other members of the Washington University team, they used seismic data in the Mariana Trench to show that about three to four times more water than previously estimated traveled beneath the tectonic plates into the Earth’s interior.

That much water rushing further into the Earth, however, is somehow offset by water returning to the oceans, as ocean levels haven’t changed dramatically through this part of the water cycle process.

“People’s estimates for the water coming out is probably out of balance,” Wiens said. “We can’t through millions of years bring lots of water through the interior. The oceans would get lower. There’s no evidence” to support that, which means that “an upward revision of the amount of water coming out of the Earth” is necessary. That water could be coming out through volcanoes or perhaps through the crust or gas funnels beneath the seafloor, he suggested.

Wiens praised all the researchers involved in the study, including Shen, whom he said was “very important” and “wrote a lot of the software we used to produce the final images.”

A resident of Queens, Shen lives with his wife Jiayi Xie, who works as a data scientist at Xaxis, a subcompany of the global media firm GroupM. The couple has an infant son, Luke.

Shen grew up in the southwestern part of China. When he was younger, he was generally interested in science, although his particular passion for geoscience started when he was in college at the University of Science and Technology of China, USTC, in Hefei, Anhui, China.

The assistant professor, who teaches a geophysics class at Stony Brook University, currently has two graduate students in his lab. He said he appreciates the support Stony Brook provides for young faculty.

As for his work, Shen is excited to contribute to the field, where he enjoys the opportunity and camaraderie that comes from exploring parts of Earth that are relatively inaccessible. He feels his detailed studies can help change people’s understanding of the planet.