From Eos: “Cores 3.0- Future-Proofing Earth Sciences’ Historical Records”

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From Eos

24 June 2021
Jane Palmer

Core libraries store a treasure trove of data about the planet’s past. What will it take to sustain their future?

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The main storage room at the National Science Foundation Ice Core Facility currently holds approximately 22,000 meters of ice cores. The room temperature is kept at about –36°C. Credit: National Science Foundation (US) Ice Core Facility.

In September 2013, a major storm dumped a year’s worth of rain on the city of Boulder, Colo., in just 2 days. Walls of water rushed down the mountainsides into Boulder Creek, causing it to burst its banks and flood nearby streets and buildings.

Instead of trying to escape the flood, Tyler Jones, a biogeochemist at the Institute of Arctic and Alpine Research at CU-Boulder(US), drove directly toward it. His motive? Mere meters from the overflowing creek, a large freezer housed the lab’s collection of precious ice cores.

“We didn’t know if the energy was going to fail in the basement,” Jones said. “So I am scrambling around with a headlamp on, less than a hundred yards from a major flood event, trying to figure out what is going on.”

The INSTAAR scientists were lucky that year, as their collection survived unscathed. But devastating core culls have happened in the past decade. In a 2017 freezer malfunction at the University of Alberta (CA) in Edmonton, Canada, part of the world’s largest collection of ice cores from the Canadian Arctic was reduced to puddles. “Thinking of those kinds of instances makes me lose sleep at night,” said Lindsay Powers, technical director of the National Science Foundation Ice Core Facility in Denver.

Collections of cores—including ice cores, tree ring cores, lake sediment cores, and permafrost cores—represent the work of generations of scientists and sometimes investments of millions of dollars in infrastructure and field research. They hold vast quantities of data about the planet’s history ranging from changes in climate and air quality to the incidence of fires and solar flares. “These materials cover anywhere from decades to centuries and even up to millions of years,” said Anders Noren, director of the NSF Facilities for Continental Scientific Drilling & Coring-U Minnesota (US) in Minneapolis, which includes a library of core samples. “It’s a natural archive and legacy that we all share and can tap into—it’s a big deal.”

Historically, some individual scientists or groups have amassed core collections, and on occasion, centralized libraries of cores have emerged to house samples. But irrespective of the types of cores stored or their size, these collections have faced a series of growing pains. Consequently, facilities have had to adapt and evolve to keep pace and ensure that their collections are available for equitable scientific research.

“We spend a lot of time in science thinking about open access when it comes to data,” said Merritt Turetsky, director of INSTAAR. Scientists should be having similar conversations about open access to valuable core samples, she said. “It is important to make science fair.”

Cores and Cookies

After 30 years of collecting wood samples for his research, astronomer Andrew Ellicott Douglass founded the Laboratory of Tree-Ring Research-UArizona (US) in 1937. With its creation at the University of Arizona in Tucson, Douglass formalized the world’s first tree ring library. Its development in the years since is a paradigm for the way core libraries are subject to both luck and strategy.

Dendrochronologists use tools to extract cores from trees to date structures and reconstruct past events such as fire regimes, volcanic activity, and hydrologic cycles. In addition to these narrow cores, they can also saw across tree stumps to get a full cross section of the trunk, called a cookie.

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At the Laboratory of Tree-Ring Research in Tuscon, Ariz, curators are cataloging a more than a century’s worth of wood samples. Credit: Peter Brewer.

Douglass originally collected cores and cookies to study the cycle of sunspots, as astronomers had observed that the number of these patches on the Sun increased and decreased periodically. The number of sunspots directly affects the brightness of the Sun and, in turn, how much plants and trees grow. By looking at the thickness of the tree rings, Douglass hoped to deduce the number of sunspots in a given year and how that number changed over the years. Douglass also went on to date archaeological samples from the U.S. Southwest using his tree ring techniques. On the way, he amassed an impressive volume of wood.

Douglass’s successors at LTRR were equally fervent in their collection. Thomas Swetnam, the director of LTRR between 2000 and 2014, estimated that his collection of cores and cookies gathered in a single decade occupied about 100 cubic meters.

During the turn of the 20th century, loggers felled a third of the giant sequoias in what is now Sequoia National Park in California. The only upside to the environmental tragedy was that it afforded researchers like Swetnam, who studies past fire regimes, the opportunity to collect cookies. “We were able to go with very large chainsaws and cut slabs of wood out of these sequoia stumps, some of them 30 feet [9 meters] in diameter,” Swetnam said. “Then we would rent a 30-foot U-Haul truck, fill it up, and bring it back to the lab.”

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Tree trunks, cores, and cookies are stored in a humidity-controlled environment at the Laboratory of Tree-Ring Research in Tuscon, Ariz. Credit: Peter Brewer.

The laboratory’s collection catalogs about 10,000 years of history, Swetnam said. It also amounts to a big space issue. “We’re talking about probably on the order of a million samples, maybe more,” Swetnam said. “We’re not even sure exactly what the total count is.”

The tree ring samples had been temporarily stored under the bleachers of Arizona Stadium in Tucson for nearly 70 years, but with generous funding from a private donor, a new structure was built to house the laboratory and its collection in 2013. The building, shaped like a giant tree house, solved the space issue, and in 2017 the lab received further funding to hire its first curator, who was charged with the gigantean task of organizing more than a hundred years of samples.

“It is a very long term endeavor,” said Peter Brewer, the LTRR curator who now works with a 20-person team on the collection. Brewer set to standardizing the labeling for the samples and is the co-lead on an international effort to produce a universal data standard for dendrochronological data. With this in place, LTRR will soon be launching a public portal for its collections, where scientists can log on and request a sample loan. This portal will make the collection more accessible to researchers around the world.

Ice Issues

In the early 1900s, around the same time that Douglass was collecting his first wood samples, James E. Church devised a tool to sample ice cores 9 meters below the ground. By the 1950s, scientists were able to extract cores from depths of more than 400 meters in the Greenland Ice Sheet. In the following years, scientists have drilled deeper and deeper to extract and collect ice cores from glaciers around the world.

Ice cores can reveal a slew of information, including data about past climate change and global atmospheric chemistry. “We’ve learned so much already about environmental challenges from ice cores, and we think that there is so much more to learn,” said Patrick Ginot of the Institute of Research for Development at the Institute of Environmental Geosciences in Grenoble, France.

Some labs, such as INSTAAR, maintain their own collections, but space can quickly become an issue, and there’s constant concern about keeping the samples frozen and safe. Taking into consideration the massive effort involved in securing a single ice core, each sample is akin to an irreplaceable work of art. “Recovering ice from 2 miles [3.2 kilometers] beneath an ice sheet in extreme cold environments is a massive challenge,” Jones said. “You can’t just go back and repeat that…. It’s a one-time deal.”

The National Ice Core Lab (US) in Denver houses many ice cores collected by scientists on National Science Foundation–funded projects. The goal is to provide a fail-safe storage environment and open access to researchers wishing to use the samples. Denver’s altitude and low humidity make running the freezers more efficient, and a rolling rack system in a new freezer will increase storage capacity by nearly a third. The facility also has backups galore: “We have redundancy on everything, and everything is alarmed,” Powers said.

The carbon footprint of running giant freezers at −36°C is high, but the lab is in the process of installing a new freezer that uses carbon dioxide refrigeration, the most environmentally friendly refrigeration system on the market. “We are at work here promoting climate research, so we want to be using the best technology possible to have the lowest impact on our environment,” Powers said.

Science Without Borders

The ice core community has adapted to various challenges that come with sustaining their libraries and working toward making the samples available on an open-access basis. But other parts of the cryosphere community are still catching up, Turetsky said.

Turetsky collects hundreds of northern soil and permafrost cores each year with her INSTARR team, and scores of other permafrost researchers are amassing equal numbers of cores from across the United States and Canada on a yearly basis. The U.S. permafrost community has more samples than the U.S. ice core community—but still doesn’t have a centralized library.

Turetsky said she is looking to learn from the ice core community while recognizing that the challenges are different for permafrost researchers. Because it is easier and less expensive to collect samples, the community hasn’t needed to join forces and pool resources in the same way the ice core community has, leading to a more distributed endeavor.

Turetsky’s vision is to establish a resource for storing permafrost samples that anyone can tap into, as well as for the U.S. permafrost community to come together to develop guiding principles for the data collected. The University of Alberta’s Permafrost Archives Science Laboratory, headed by Duane Froese, is a great example of a multiuser permafrost archive, Turetsky said. Ultimately, the community may need to think about a regional hub with international connections to propel scientific inquiry.

“We can’t do our best science siloed by national borders,” Turetsky said. “I would love to see sharing of permafrost samples or information be a type of international science diplomacy.”

A Race Against Time

The need for the cryosphere community (encompassing both ice core and permafrost researchers) to come together and collect data in such a way that they can be shared and used in the future has never been greater, Turetsky said. The Arctic is warming faster than anywhere else on the planet, and simultaneously warming sea ice, ice sheets, and permafrost have great potential to influence Earth’s future climate. “So not only are [ice and permafrost environments] the most vulnerable to change, they also will change and dictate our climate future,” Turetsky said.

In the worst-case scenario, the Arctic may lose all sea ice or permafrost, and scientists will lose the ability to collect core samples. “So it is a race against time to get cores, to learn, and to communicate to the public how dire the situation is,” Turetsky said.

Tree ring researchers are facing their own race against time, Swetnam said. As wildfires rage across the United States, scientists are trying to collect as much as possible from older trees before they are claimed by flames. “The history that’s contained in the rings is not renewable,” Swetnam said. “It’s there, and if it’s lost, it’s lost.”

That scientists may lose the ability to collect some samples makes maintaining core libraries and sharing their resources all the more important, Brewer said. “A good chunk of what we have no longer exists in the forests. All that is left are the representative pieces of wood that are in our archives.”

A Futuristic Vision

Recognizing threats posed by climate change, one group of cryosphere scientists has set out to create a visionary ice core library for future generations. Instead of housing core samples from around the world in one country, the group plans to store them in Antarctica, a continent dedicated to science and peace; the 1959 Antarctic Treaty specifies that “scientific observations and results from Antarctica shall be exchanged and made freely available.”

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Ice cores stored in the temporary core storage in the underground ice cave constructed by the EastGRIP – The East Greenland Ice-core Project – University of Copenhagen [Københavns Universitet](DK). Credit: Tyler R. Jones/INSTAAR.

And the ice cores won’t be stored in a building. They’ll be buried deep in the largest natural freezer of them all: the Antarctic Ice Sheet. This core library will act as a heritage data set, a legacy for future generations of scientists from all over the world. Researchers can access the cores in the interim, especially those taken from glaciers that no longer exist, and the Ice Memory project’s organizers are currently addressing how to grant access to the cores in a way that is equitable, as travel to Antarctica is cost prohibitive for many researchers.

The first stage of the project has focused on how to store the cores in the ice sheet. The plan is to store them about 10 meters deep, where the temperature is a stable −50°C throughout the year. “Even if there are a few degrees of warming in the next decades or centuries, it will still be kept at minus 50° or 45°,” said Ginot, one of the coordinators of the Ice Memory project.

Researchers from the French and Italian polar institutes have already trialed the best storage techniques on Dome Concordia in Antarctica. They dug 8-meter-deep, 100-meter-long trenches and inserted giant sausage-shaped balloons on the ice floors. Then they used the dug-out snow to cover the balloons and allowed the snow to harden. “When they disassembled the sausage, they had a cave under the snow,” Ginot said.

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Constructing giant trenches at Dome Concordia in Antarctica. Digging these trenches was the first step in trialing how to store ice cores in underground caves. Credit: Armand Patoir, French Polar Institute Paul-Émile Victor [Institut polaire français Paul-Émile Victor] (FR).

The project’s models forecast that the cavities will last for 20–30 years, at which time the scientists will create more caves at a minimal cost, Ginot said. The current focus of the team is to collect samples from glaciers that are quickly disappearing, such as the northern ice field near the summit of Mount Kilimanjaro in Tanzania.

Recognizing the Value

Core libraries provide a vital window into events that happened before human records began, a repository for data to better understand Earth systems, and resources to help forecast future scenarios. Researchers believe that as science and technology evolve, they’ll be able to extract even more information from core collections. “We recognize that this is a library of information, and we’ve just read some of the pages of some of the books,” Swetnam said. “But as long as the books are still there, we can go back and interrogate them.”

While the libraries for ice, tree ring, and sediment cores are maintained, scientists are able to access the “books” for further analysis whenever they want.

“We see all kinds of cases where a new analytical technique becomes available, and people can ask new questions of these materials without having to go and collect them in the field,” Noren said. New analytical techniques have led to more accurate reconstruction of past temperatures from lake core sediments, for example, and by integrating several core data sets, scientists have revealed that humans began accelerating soil erosion 4,000 years ago.

The multifaceted value of the core collections has become even more pronounced during the COVID-19 pandemic, Noren said. Core libraries have allowed scientists to continue moving forward with their research even when they can’t do fieldwork. As recently as March 2021, for example, scientists published research on the multimillion-year-old record of Greenland vegetation and glacial history that was based on existing cores, not those collected by the scientists’ field research.

Although some libraries struggle with space constraints, maintaining suitable environmental conditions, cataloging samples, or ensuring open access, every scientist or curator of a core collection shares one concern: sustaining funding.

It costs money to run a core library: money to house samples, money to employ curators, and money to build systems that allow equal and fair access to data. Securing that financial support is a challenge. “Funding priority is about exciting research or a new instrument,” Brewer said. “Updating or maintaining a collection of scientific samples is not such an easy sell.”

Core libraries represent millions of years of history and hold keys to understanding and protecting Earth’s future. They are natural archives of ice-covered continents, forested lands, and ancient cultures. As such, they are a legacy to be preserved and protected for future generations, Noren said. “But if you view it from another lens, they are just storage,” he explained. “So we need to elevate that conversation and make it clear that these materials are essential for science.”

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