Into the unknown: Exploring caves to uncover climate change clues

Into the unknown: Exploring caves to uncover climate change clues

By Christian Elliott and Brittany Edelmann, Dec. 8, 2021 –

Nearly 20 years ago, then Ph.D. student Gina Moseley walked into a bar in Bristol to meet fellow members of the University of Bristol Spelæological Society caving club. An older caver talked with her over drinks about some small caves in northeastern Greenland he’d always dreamed of organizing an expedition to explore. But, “logistically, it’s a nightmare to get out there,” said Moseley, now a professor in the Institute of Geology at the University of Innsbruck in Austria. The caver gave her all the papers he’d collected on the caves, and for years she kept them filed away.

Much later, a 1960 article by U.S. military geologists among the papers caught her eye. In their search for prime airfield locations, the geologists discovered caves with interesting geological features — crystalline calcite, stalagmites and flowstone deposits. To Moseley, that was proof Greenland’s caves contained something critical to scientists’ understanding of Earth’s ancient climate.

Moseley took her first steps into caving years earlier with her mom on a holiday trip when she was 12. She loved it. As she started grad school in Bristol, she discovered she could bring together her fascination with caves and her interest in studying paleoclimate to understand how future climate change — pushed by fossil fuel emissions of human activities — will affect the Earth.

Caves are normally “not altered or impacted by other processes” and “they’re so well-preserved over thousands of years,” Moseley said. That makes them a great location for climate research and creating records that can function as important analogs for future climate change.

The 2021 Comer Climate Conference on Oct. 4 – 5 brought together scientists from around the world, including Moseley and fellow paleoclimate researcher Kathleen Wendt.

Devil’s Hole

“Devils Hole was where it all began. That was the start of cave paleoclimate research,” Moseley said. Paleoclimate scientists first rappelled down into the deep, narrow cave in the Amargosa Desert in southwest Nevada in the late 1980s.

Using cores of the thick calcite crusts on the cave walls, which accumulated steadily over time, researchers reconstructed 500,000 years of climate history here with Uranium-thorium dating. Uranium-thorium dating provides insight into when a rock was formed– giving a date to the origin of the rock.

Devil’s Hole was also where Moseley and Wendt, who has her Ph.D. from the University of Innsbruck in Austria, got their start in cave paleoclimate science. In 2017, they returned to Devils Hole to extend the climate record further and validate the older results.

In their research Moseley and Wendt focused on oxygen isotopes, which provide temperature information about historic temperatures. During ice ages, a heavier isotope of oxygen forms at higher levels than during warm spells.

Wendt is getting ready to submit a new paper on the oxygen isotope record from Devils Hole. By showing the fluctuation in types of isotopes, heavier versus lighter forms of oxygen, this will give “clues into changes in temperature and a little bit about the source of precipitation over time,” Wendt said.

They found the water table dropped below modern levels during the last interglacial, 120,000 years ago, when Earth’s orbit brought the planet closer to the sun. That time period is an analog for southern Nevada’s hotter and drier future that will be accelerated beyond natural planetary fluctuations with human-forced extremes of climate change.

“Studying the paleoclimate tells us what nature is capable of,” Wendt said.

The Greenland caves

Paleoclimatologists who focus on caves often study speleothems — mineral deposits formed by dripping water. Protected within caves from the elements, these dripstones (stalagmites and stalactites) and flowstones grow as layers of calcium carbonate carried by rainwater add up over hundreds of thousands of years.

One of the flowstones Moseley found in the caves was specifically mentioned in the 1960 paper that inspired the expedition.

In Greenland, now a rainless polar desert, speleothems formed during a time when the island’s climate was warmer and wetter. By collecting and sampling speleothems, Moseley can reconstruct that ancient climate period as an analog for the future, when Greenland will once again be warmer and wetter.

Over millions of years due to orbital changes, Earth’s climate alternates between warm and cold periods — interglacials and ice ages called glacials. Paleoclimatologists rely on air bubbles in cores taken from ice sheets in Greenland and the Antarctic to study the composition of the ancient climate’s atmosphere, but there’s a problem — during warm periods, the ice sheet melts. That’s where the caves come in.

“So the caves offer the polar opposite of what the ice cores do because the ice cores tend to be cold-based climate records and the caves can give us warm-based climate records. So, we get to the two different parts together,” Moseley said.

That’s a common theme in paleoclimatology — no one climate proxy shows the big picture. To fully understand Earth’s ancient climate, scientists must piece together hundreds of pieces from data from sources across the world.

“If you have one cave in one location, that’s kind of interesting. But if you can relate that to other caves in other locations, ice cores in other locations, deep sea sediments in other locations and get the whole picture, that’s where it really gets interesting. That’s where we can answer the big questions and tackle the big issues,” Moseley said.

As the Arctic continues to warm at twice the rate of the rest of the world, understanding what warm and wet historic climate periods were like can help scientists know what to expert in the imminent future.

This leads to Moseley’s next adventure in 2023, where she will explore completely untouched caves in Northern Greenland. This was only made possible with an award from Rolex — which provides funding for such an endeavor.

Christian Elliott and Brittany Edelmann are science and environmental reporters at Medill. You can follow them on Twitter at @csbelliott. and @brittedelmann.

Enhanced weathering: When climate research takes unexpected turns

Enhanced weathering: When climate research takes unexpected turns

By Brittany Edelmann and Carly Menker, Dec. 5, 2021 –

Oxford University Ph.D. student Frankie Buckingham collected the 30, 1-meter-long cylindrical tubes of soil she needed for climate research in August 2018 on a British farm in North Oxfordshire. The farm had previously cultivated oats and barley in the soil. A variety of crushed rocks and minerals, such as basalt, olivine and volcanic ash, were added to the 30 cores and then positioned on the roof of Oxford’s Earth Sciences Department building. From October 2018 to June 2021, Buckingham analyzed the soils to watch for the effects of enhanced weathering on climate change impacts. But, what she found wasn’t quite what she expected.

Buckingham’s study focused on “enhanced weathering” as a carbon dioxide removal technique involving the application of crushed rock to agricultural soil.

Carbon dioxide in the atmosphere is a thermostat for climate change, holding in heat that drives global warming and driving changes in our climate as we know it. Carbon dioxide levels today are more than 35% higher than at any point in at least the past 800,000 years and rose 30% just since 1970. The last time the atmospheric CO2 levels matched today’s concentrations was over 3 million years ago, during the Mid-Pliocene Warm Period. Temperatures then ranged from 2 degrees to 3 degrees Celsius (3.6 degrees to 5.4 degrees Fahrenheit) higher than during the pre-industrial era and sea level leveled off at 15 to 25 meters (50 to 80 feet) higher than today, according to the National Oceanic and Atmospheric Administration (NOAA).

Enhanced weathering is a process that aims to accelerate natural silicate weathering during which carbon dioxide reacts with rocks, a process that usually takes millions of years. Silicate weathering begins with the reaction between water, carbon dioxide and silicate rocks, which breaks down the rock. Eventually, the dissolved components are washed into the ocean where the carbon is stored for hundreds of thousands of years, either as mineral sediments or dissolved in the water, according to Buckingham. Enhanced weathering amps up this process by breaking down silicate rocks, such as basalt, into tiny pieces in a way of skipping slow weathering processes. The powder made from this is spread on agricultural land and the process can be further accelerated by fungi and roots in the soil.

Buckingham, on the roof of her research building, extracts water from the soil cores for further analysis of enhanced weathering processes. (Photo credit: Frankie Buckingham)

As a young child, Buckingham was already interested in climate change. She obtained a master’s degree in Earth Sciences from the University of Oxford, focusing on past periods of climate change and studying cave deposits.  During her Ph.D. program, she switched gears to try to answer the question of “how we might be able to prevent rising global temperatures?”

“The emergency of the climate crisis makes it a thrilling area to work in,” Buckingham said.

Buckingham started her presentation about her research at the 2021 Comer Climate Conference talking about The Paris Agreement, an international treaty pledging to limit greenhouse gas emissions so that the average global temperature rise is kept under 2 degrees Celsius and preferably under 1.5 degrees. Despite having already sparked low-carbon solutions and new markets, there are still many actions that need to be implemented, one of them being negative emission technologies to help remove carbon dioxide from the atmosphere. This is where enhanced weathering comes in.

Buckingham’s results so far focus strictly on crushed basalt instead of crushed olivine, which most researchers have used. Why has research favored olivine? It has been shown to dissolve the quickest, absorbing CO2 in the process, Buckingham said. But further research indicated that olivine releases harmful chromium and nickel into the soils, something that takes a toll on the environment.

Assumptions made from previous research using simple experiments conducted in the laboratory – beaker experiments – gave a more optimistic view of the weathering process, Buckingham said. Her research differed because it was conducted in a way that was “as close to the field (as) you can get.”

Buckingham explained findings on why some mineral treatments dissolve quicker. She connected her field research back to beaker research with olivine, which revealed that olivine is one of the mineral that dissolves the quickest. Contrary to original expectations, Buckingham’s research showed crushed basalt actually dissolves three to four orders slower than previously expected.

Buckingham cuts soil core into 10-centimeter segments and measures for different physical properties. (Photo credit: Frankie Buckingham)

She elaborated on how many current enhanced weathering calculations assume that basalt can be applied to crops year after year – safely compared with olivine – and that it will dissolve. But, when looking at the crushed basalt in the soil cores, her research revealed that 99% of the crushed basalt does not dissolve.

“Within 50 years, you will have 25 centimeters (10 inches) of a basalt layer,” Buckingham said, which can affect agriculture and farmers who use the crushed basalt in their soil.

Previous thinking also expected the dissolution products (the components that separated from the rock) to travel from the soil into the oceans to help stem ocean acidification and increase the pH content within the ocean water. By consuming acidic ions during dissolution and by releasing important ions such as calcium and magnesium,  enhanced weathering sequesters CO2  and helps counteract ocean acidification.

But, Buckingham found that the “dissolution products were retained in the core.”

“The dissolution products can be sticky and can be chemically removed from the water,” Buckingham said, which prevents the dissolution products from getting into the oceans.

Negative emission technologies

Enhanced weathering is one type of negative emission technology to remove CO2 from the environment. And, as Buckingham’s research shows, more than one process is needed to have an impact on the pace at which the world generates CO2 emissions from fossil fuel use. There are “a plethora of negative emissions technologies” to help combat climate change, according to Buckingham. We cannot rely on just one, she said.

Some other examples include planting new trees, biochar, ocean alkalinization and bioenergy carbon capture and storage. Mature trees don’t sequester carbon dioxide as quickly, so this is where young trees come in to help. Organic material is burned into biochar, which then locks up the carbon. Ocean alkalinization can help to draw down carbon dioxide by spreading alkaline crushed rocks directly into oceans, which ultimately will raise the alkalinity of the ocean water. Bioenergy with carbon capture and storage (BECCS) is a process where biomass, such as crops or wood, that sequester carbon dioxide when grown, are burned for heat and electricity. The carbon dioxide emitted during burning is captured and transported for underground storage.

Where do we go from here?

Buckingham emphasized how her research shows that enhanced weathering may not draw down as much carbon dioxide as previously anticipated and can have “major impacts to soil chemistry.” But “that’s not a reason to lose hope,” she said. Her research was done in the U.K., as opposed to a warmer, more humid climate like the tropics. In tropical climates, more CO2 is drawn out faster due to the quicker breakdown of crushed rock and minerals.

Research is done to figure out answers to questions. The hope is that positive findings result, she said.

This research showed different results from previous assumptions. Jeff Servinghaus, professor of Geosciences at the Scripps Institution of Oceanography at the University of California, San Diego, expressed gratitude to Buckingham at the conference.

“It’s very important work, because you know if we chase down dead ends, that’s just wasted time and money, right? So thank you for that,” he said

Geologist Richard Alley, emcee of the Comer Conference and a geosciences professor at Pennsylvania State University, said the more research that is done, the clearer it is that it’s easier to keep carbon dioxide out of the air than taking it out.

“If you can enrich your soil that’s good and if you can take a little carbon dioxide down that’s great, but don’t count on that to solve the problem,” Alley said.

“And although this might sound quite negative, it highlights the more realistic situation that we need to be aware of,” Buckingham said.

Brittany Edelmann is a registered nurse. She is health, environment and science reporter and a Comer Scholar at Medill. Follow her on twitter @brittedelmann

Carly Menker is a health, environment and science reporter for the Medill News Service and a Comer Scholar at Medill.  Follow her on Twitter @carlymenker.

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