Record-breaking 1.2-kilometer drill core unveils new insights into Earth's mantle

American Association for the Advancement of Science (AAAS)

A record-breaking 1268-meter drill core into Earth’s mantle, collected from the Mid-Atlantic Ridge in the North Atlantic, has provided a deep and detailed mineralogical glimpse of the oceanic mantle. The findings reveal new insights into mantle composition, Earth’s deep geology, and the potential biogeochemical conditions involved in the origins of life. Understanding the Earth’s mantle is crucial for comprehending important details of the Earth system, including terrestrial magmatism, crust formation, and the cycling of elements between the planet’s interior, hydrosphere, atmosphere, and biosphere. Much of what is known is based on rocks dredged off the ocean floor. However, these samples often lack critical geological context and are subject to altered mineralogy due to igneous processes and seafloor weathering, including serpentinization. Although rock cores of abyssal peridotites – the primary rock of Earth’s upper mantle – can provide a continuous record, drilling the kilometer-deep holes required to obtain them has proved challenging.

 

Now, Johan Lissenberg and colleagues report the recovery and characterization of a nearly continuous 1268-meter-long drill core of serpentinized abyssal mantle peridotite from the mid-Atlantic ridge. The drill core was collected in 2023 during the International Ocean Discovery Program (IODP) Expedition 399, from a hydrothermally active region called the Atlantis Massif. Lissenberg et al. documented significant mineralogical variations throughout the core at various scales, including in levels of serpentinization. The sample’s pyroxene content was also unexpectedly low compared to other abyssal peridotite samples worldwide, which could be due to high degrees of depletion and pyroxene dissolution during melt flow. And, contrary to common models, melt migration was found to be oblique to mantle upwelling. The authors observed hydrothermal fluid-rock interaction throughout the core, with oxidative weathering down to 200 meters. Gabbroic intrusions were also discovered to play an unexpected role in hydrothermal alteration and in regulating fluid compositions from peridotite-hosted hydrothermal vents, which have been proposed as models of environments where prebiotic chemistry may have led to the development of life on early Earth and other planetary bodies. “Decades of ocean floor sampling by dredging have painted a rough mineralogical picture of mantle. Yet, each new drilling mission reveals surprising views of mantle and formation of the oceanic crust,” writes Eric Hellebrand in a related Perspective. “More ambitious drilling projects will reveal important pieces to understand the biogeochemical effects of oceanic mantle.”

---

Journal

Science

DOI

10.1126/science.adp1058 

Article Title

A long section of serpentinized depleted mantle peridotite

Article Publication Date

9-Aug-2024

Record-breaking recovery of rocks that originated in Earth’s mantle could reveal secrets of planet’s history

International team begin to unravel mantle’s role in life on 

Earth, volcanism and global cycles

Woods Hole Oceanographic Institution

 

image: 

The researchers say the rocks recovered from the mantle bear a closer resemblance to those that were present on early Earth rather than the more common rocks that make up our continents today.

view more 

Credit: Professor Johan Lissenberg

Scientists have recovered the first long section of rocks that originated in the Earth’s mantle, the layer below the crust and the planet’s largest component.

The rocks will help unravel the mantle’s role in the origins of life on Earth, the volcanic activity generated when it melts, and how it drives the global cycles of important elements such as carbon and hydrogen, according to the team.

The nearly continuous 1,268 metres of mantle rock was recovered from a “tectonic window,” a section of the seabed where rocks from the mantle were exposed along the Mid-Atlantic Ridge, during Expedition 399 “Building Blocks of Life, Atlantis Massif” of the ocean drilling vessel JOIDES Resolution in Spring 2023.

With attempts dating back to the early 1960s, the recovery was a record-breaking achievement led by the International Ocean Discovery Program, an international marine research consortium of more than 20 countries that retrieves cores—cylindrical samples of sediment and rock—from the ocean floor to study Earth’s history.

Since then, the expedition team has been compiling an inventory of the recovered mantle rocks to understand their composition, structure and context.

Their findings, presented in the journal Science, reveal a more extensive history of melting in the recovered rocks than expected.

Lead author Professor Johan Lissenberg from Cardiff University’s School of Earth and Environmental Sciences, said: “When we recovered the rocks last year, it was a major achievement in the history of the Earth sciences, but, more than that, its value is in what the cores of mantle rocks could tell us about the makeup and evolution of our planet.

“Our study begins to look at the composition of the mantle by documenting the mineralogy of the recovered rocks, as well as their chemical makeup.

“Our results differ from what we expected. There is a lot less of the mineral pyroxene in the rocks, and the rocks have got very high concentrations of magnesium, both of which results from much higher amounts of melting than what we would have predicted.”

This melting occurred as the mantle rose from the deeper parts of the Earth towards the surface.

Results from further analysis of this process could have major implications for the understanding of how magma is formed and leads to volcanism, the researchers claim.

“We also found channels through which melt was transported through the mantle, and so we are able to track the fate of magma after it is formed and travels upwards to the Earth’s surface.

“This is important because it tells us how the mantle melts and feeds volcanoes, particularly those on the ocean floor that account for the majority of volcanism on Earth. Having access to these mantle rocks will allow us to make the connection between the volcanoes and the ultimate source of their magmas.”

The study also provides initial results on how olivine, an abundant mineral in mantle rocks, reacts with seawater, leading to a series of chemical reactions that produce hydrogen and other molecules that can fuel life.

Scientists believe this might have been one of the underpinning processes in the origin of life on Earth.

Dr Susan Q Lang, an associate scientist in Geology and Geophysics at the Woods Hole Oceanographic Institution, who was a co-chief scientist on the expedition and part of a team continuing to analyse rock and fluid samples, said: “The rocks that were present on early Earth bear a closer resemblance to those we retrieved during this expedition than the more common rocks that make up our continents today.

“Analysing them gives us a critical view into the chemical and physical environments that would have been present early in Earth’s history, and that could have provided a consistent source of fuel and favorable conditions over geologically long timeframes to have hosted the earliest forms of life.”

The international team of more than 30 scientists from the JOIDES Resolution expedition will continue their research on the recovered drill cores to address a wide range of problems.

Dr. Andrew McCaig, an Associate Professor in the School of Earth and Environment at the University of Leeds, who was the lead proponent of Expedition 399 and a co-chief scientist on the Expedition added: “Everyone involved in Expedition 399, starting with the first proposal in 2018, can be proud of the achievements documented in this paper. Our new deep hole will be a type section for decades to come in disciplines as diverse as melting processes in the mantle, chemical exchange between rocks and the ocean, organic geochemistry and microbiology. All data from the expedition will be fully available, an exemplar of how international science should be conducted.”

Their paper, ‘A long section of serpentinized depleted mantle peridotite,’ is published in Science.

 

Core Description 

Caption: Professor Johan Lissenberg (left) and colleagues analysing the cores, which were recovered from a “tectonic window” on the Mid-Atlantic Ridge.

Credit

Lesley Anderson, Exp. 399, JRSO_IODP

JOIDES Resolution 

Expedition 399 “Building Blocks of Life, Atlantis Massif” of the ocean drilling vessel JOIDES Resolution which recovered the 1,268m of near continuous mantle rock in Spring 2023.

Credit

Thomas Ronge (Exp. 399, JRSO_IODP)

Cardiff University is recognised in independent government assessments as one of Britain’s leading teaching and research universities and is a member of the Russell Group of the UK’s most research intensive universities. The 2021 Research Excellence Framework found 90% of the University’s research to be world-leading or internationally excellent.  Among its academic staff are two Nobel Laureates, including the winner of the 2007 Nobel Prize for Medicine, Professor Sir Martin Evans. Founded by Royal Charter in 1883, today the University combines impressive modern facilities and a dynamic approach to teaching and research. The University’s breadth of expertise encompasses: the College of Arts, Humanities and Social Sciences; the College of Biomedical and Life Sciences; and the College of Physical Sciences and Engineering. Its University institutes bring together academics from a range of disciplines to tackle some of the challenges facing society, the economy, and the environment. More at www.cardiff.ac.uk

The Woods Hole Oceanographic Institution (WHOI) is a private, non-profit organization on Cape Cod, Massachusetts, dedicated to marine research, engineering, and higher education. Established in 1930, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate an understanding of the ocean’s role in the changing global environment. WHOI’s pioneering discoveries stem from an ideal combination of science and engineering—one that has made it one of the most trusted and technically advanced leaders in basic and applied ocean research and exploration anywhere. WHOI is known for its multidisciplinary approach, superior ship operations, and unparalleled deep-sea robotics capabilities. We play a leading role in ocean observation and operate the most extensive suite of data-gathering platforms in the world. Top scientists, engineers, and students collaborate on more than 800 concurrent projects worldwide—both above and below the waves—pushing the boundaries of knowledge and possibility. For more information, please visit www.whoi.edu

The University of Leeds is one of the largest higher education institutions in the UK, with more than 40,000 students from more than 137 different countries. We are renowned globally for the quality of our teaching and research. We are a values-driven university, and we harness our expertise in research and education to help shape a better future for humanity, working through collaboration to tackle inequalities, achieve societal impact and drive change. The University is a member of the Russell Group of research-intensive universities, and is a major partner in the Alan Turing, Rosalind Franklin and Royce Institutes www.leeds.ac.uk

---

Journal

Science

DOI

10.1126/science.adp1058 

Method of Research

Observational study

Subject of Research

Not applicable

Article Title

A long section of serpentinized depleted mantle peridotite

Article Publication Date

8-Aug-2024

 

Leading causes of death in the US, 2019-2023

JAMA Network

About The Article: This Viewpoint from the National Center for Health Statistics reports the leading causes of death in the U.S. from 2019 to 2023, including the emergence of COVID-19 and shifts in other top causes as pandemic deaths decreased.

Corresponding Author: To contact the corresponding author, Farida Bhuiya Ahmad, MPH, email hhi0@cdc.gov.

To access the embargoed study: Visit our For The Media website at this link https://media.jamanetwork.com/

(doi:10.1001/jama.2024.15563)

Editor’s Note: Please see the article for additional information, including other authors, author contributions and affiliations, conflict of interest and financial disclosures, and funding and support.

#  #  #

Embed this link to provide your readers free access to the full-text article This link will be live at the embargo time https://jamanetwork.com/journals/jama/fullarticle/10.1001/jama.2024.15563?guestAccessKey=ded802ef-b956-4519-a43e-984ebe99e270&utm_source=For_The_Media&utm_medium=referral&utm_campaign=ftm_links&utm_content=tfl&utm_term=080824

---

Journal

JAMA

 

Money trees: WVU researchers looking at local benefits from climate fighting ability in Appalachian forests

West Virginia University

 

image: 

In Central Appalachia, programs that manage forested lands to enhance the carbon-storing capabilities of trees and soil are paying dividends for large corporate landowners but leaving small landholders out, according to WVU research. Biologist Steven Kannenberg is working to ensure local communities benefit from the carbon credits their forests generate. 

view more 

Credit: (WVU Photo/Alyssa Reeves)

Researchers at West Virginia University are working to ensure small landowners and local communities, instead of large corporations, profit from the ability of Central Appalachian forests to remove greenhouse gas carbon dioxide from the atmosphere.

So-called “forest-based climate solution programs” manage forest ecosystems in a way that enhances carbon storage by planting trees, for example, or by restricting logging. To ensure these programs benefit both forests and local communities, a WVU team will spend the next four years investigating how different management practices affect Appalachian forest life — from the trees and other flora that grow there to the loggers, farmers, trail riders and ginseng gatherers who are also part of those ecosystems.

The project is supported by $1.7 million from the National Science Foundation.

“To curb climate change, we have to reduce fossil fuel emissions. But we can also take advantage of our forests’ ability to remove the carbon dioxide in our atmosphere and store it long term in wood and soils,” said Steven Kannenberg, assistant professor of biology at the WVU Eberly College of Arts and Sciences. “In particular, the forests of the eastern U.S. are an incredibly large carbon sink. The amount of carbon dioxide they capture is equivalent to 40-60% of the region’s fossil fuel emissions.”

There’s money to be made from that carbon capture. In 2023, the Biden Administration poured $150 million into forest-based climate solution programs targeting small-acreage landowners. The financial markets trade billions of dollars in carbon offset credits every year.

However, although about 70% of eastern U.S. forests are under small individual or family ownership, little revenue has made its way to local communities. Instead, Kannenberg said forest-based climate projects “are overwhelmingly conducted on corporate landholdings owned by entities outside the region.”

He said he believes identifying incentives for local landowners to allow carbon management programs on their properties is essential to combatting climate change. Landowners who agree to host these programs contract with companies to receive regular payments, based on acreage and the estimated amount of carbon stored, over a set number of years.

The contracts have been a hard sell among small landholders in Appalachia, partly because revenues are only significant for large parcels. Owners typically must allow forestry management practices to happen on the land, and the long contracts restrict owners’ abilities to use the land for some commercial purposes or as collateral on loans.

Kannenberg also noted that while forestry management practices for improving soil health or biodiversity yield several potentially profitable “co-benefits” beyond just carbon capture, neither landowners nor forestry managers have the data they need to forecast those revenues.

The team will ask about problems like those in the surveys they’ll send to thousands of small landowners across the region, and in interviews with loggers, sawmill operators, tourism small business operators and other participants in the forest economy of a former Clearfork Valley mining community on the Tennessee-Kentucky border.

The researchers will also fill serious knowledge gaps about how different management practices affect forests’ carbon sequestration capabilities, looking to sites where detailed logging records have been kept for a century: Fernow Experimental Forest, WVU Research Forest, Summit Bechtel Reserve and Monongahela National Forest. Each forest contains mature, undisturbed areas as well as areas that have been logged using a variety of common practices.

By measuring factors like tree height, leaf area, the mass of root systems, the nutrients in the soil and annual growth using tree rings, the team will quantify the impacts of human intervention on the ecosystem over time.

Already, preliminary data has revealed how forestry management in those zones changed the species distribution and weakened resilience to climate change. At Fernow, red oaks became less prevalent after timber was harvested, replaced by trees without the oak’s ability to store large amounts of carbon and resist drought conditions.

“Eastern U.S. forests are critical to meeting greenhouse gas emission targets,” Kannenberg said. “Eastern forests are more resilient to climate change than the arid forests of the western U.S. because stressors such as rising temperatures, increasing drought, and enhanced pest and pathogen presence are projected to be less severe.

“That’s why projects exploring forest-based climate solutions are exploding in Central Appalachia. This region is going to be the model for how forested communities worldwide will transition out of economies based on fossil fuel extraction.”

Decarbonization seed funding secured by the WVU Research Office permitted the acquisition of some initial data.

The WVU research team also includes Kathryn Gazal, associate professor of forest resources management in the WVU Davis College of Agriculture and Natural Resources, as well as Brenden McNeil, professor of geography, and Edward Brzostek, associate professor and associate chair for graduate studies, both from the Eberly College.

 

Millions of years for plants to recover from global warming

ETH Zurich

In brief:

• Disruption of the functioning of vegetation due to warming can lead to the failure of climate regulating mechanisms for millions of years.
• Vegetation changes can alter the planet’s climate equilibrium.
• Geological and climatic history provide insight into the effects of global warming today.

Scientists often seek answers to humanity’s most pressing challenges in nature. When it comes to global warming, geological history offers a unique, long-term perspective. Earth’s geological history is spiked by periods of catastrophic volcanic eruptions that released vast amounts of carbon into the atmosphere and oceans. The increased carbon triggered rapid climate warming that resulted in mass extinctions on land and in marine ecosystems. These periods of volcanism may also have disrupted carbon-climate regulation systems for millions of years.

Ecological imbalance

Earth and environmental scientists at ETH Zurich led an international team of researchers from the University of Arizona, University of Leeds, CNRS Toulouse, and the Swiss Federal Institute for Forest Snow and Landscape Research (WSL) in a study on how vegetation responds and evolves in response to major climatic shifts and how such shifts affect Earth’s natural carbon-climate regulation system.

Drawing on geochemical analyses of isotopes in sediments, the research team compared the data with a specially designed model, which included a representation of vegetation and its role in regulating the geological climate system. They used the model to test how the Earth system responds to the intense release of carbon from volcanic activity in different scenarios. They studied three significant climatic shifts in geological history, including the Siberian Traps event that caused the Permian-Triassic mass extinction about 252 million years ago. ETH Zurich professor, Taras Gerya points out, “The Siberian Traps event released some 40,000 gigatons (Gt) of carbon over 200,000 years. The resulting increase in global average temperatures between 5 - 10°C caused Earth’s most severe extinction event in the geologic record”.

Move, adapt, or perish 

“The recovery of vegetation from the Siberian Traps event took several millions of years and during this time Earth’s carbon-climate regulation system would have been weak and inefficient resulting in long-term climate warming,” explains lead author, Julian Rogger, ETH Zurich.

Researchers found that the severity of such events is determined by how fast emitted carbon can be returned to Earth’s interior – sequestered through silicate mineral weathering or organic carbon production, removing carbon from Earth’s atmosphere. They also found that the time it takes for the climate to reach a new state of equilibrium depended on how fast vegetation adapted to increasing temperatures. Some species adapted by evolving and others by migrating geographically to cooler regions. However, some geological events were so catastrophic that plant species simply did not have enough time to migrate or adapt to the sustained increase in temperature. The consequences of which left its geochemical mark on climate evolution for thousands, possibly millions, of years.  

Today’s human-induced climate crisis

What does this mean for human induced climate change? The study found that a disruption of vegetation increased the duration and severity of climate warming in the geologic past. In some cases, it may have taken millions of years to reach a new stable climatic equilibrium due to a reduced capacity of vegetation to regulate Earth’s carbon cycle.

“Today, we find ourselves in a major global bioclimatic crisis,” comments Loïc Pellissier, Professor of Ecosystems and Landscape Evolution at ETH Zurich and WSL. “Our study demonstrates the role of a functioning of vegetation to recover from abrupt climatic changes. We are currently releasing greenhouse gases at a faster rate than any previous volcanic event. We are also the primary cause of global deforestation, which strongly reduces the ability of natural ecosystems to regulate the climate. This study, in my perspective, serves as ‘wake-up call’ for the global community.”

---

Journal

Science

DOI

10.1126/science.adn3450 

Method of Research

Computational simulation/modeling

Subject of Research

Not applicable

Article Title

Biogeographic climate sensitivity controls Earth system response to large igneous province carbon degassing

Article Publication Date

8-Aug-2024

 

The threat of mpox has returned, but public knowledge about it has declined

Annenberg Public Policy Center of the University of Pennsylvania

 

image: 

How worried U.S. adults are about contracting mpox in the next three months. From the Annenberg Public Policy Center's ASAPH survey in July 2024.

view more 

Credit: Annenberg Public Policy Center

PHILADELPHIA – It has been two years since the World Health Organization declared a global health emergency over an outbreak of mpox, a disease endemic to Africa that had spread to scores of countries. Now, in the summer of 2024, a deadlier version of the infectious disease has spread from the Democratic Republic of Congo to other African nations, the strain that originally hit the United States has shown signs of a resurgence, and this week the Centers for Disease Control and Prevention (CDC) issued a new alert on mpox to health care providers.

But while the American public quickly learned about the disease during the summer of 2022, as the number of cases declined and media attention waned, much of that knowledge appears to have been lost, according to new survey data from the Annenberg Public Policy Center of the University of Pennsylvania.

In a nationally representative survey of about 1,500 U.S. empaneled adults conducted in July 2024, the policy center finds that knowledge about mpox – which increased from July to August 2022 – has declined, along with fear of the disease (which was previously called monkeypox). This wave of the Annenberg Science and Public Health (ASAPH) knowledge survey finds that:

• Only 1 in 20 Americans (5%) are worried about contracting mpox in the next three months, down from 21% in August 2022. In addition, fewer than 1 in 10 (9%) are worried that they or their families will contract mpox.

• Fewer than 1 in 5 people (17%) know that mpox is less contagious than Covid-19, down from 41% in August 2022. Nearly two-thirds (63%) are not sure.

• Just a third of people (34%) know that men who have sex with men are at a higher risk of infection with mpox, down from nearly two-thirds (63%) in August 2022.

• Less than half (45%) know that a vaccine for mpox exists, down from 61% in August 2022.

• Fewer people (58%) know that it’s false to say that getting a Covid-19 vaccine increases your chances of getting mpox, down from 71%.

“The speed with which the public learned needed information about mpox in the summer of 2022 was a tribute to effective communication by the public health community,” said Kathleen Hall Jamieson, director of the Annenberg Public Policy Center (APPC) and director of the survey. “That same expertise should now be deployed to ensure that those at risk remember mpox’s symptoms, modes of transmission, and the protective power of vaccination.”

Mpox outbreaks in 2024 and 2022

Discovered in 1958, mpox is a rare disease caused by an orthopox virus, and is a less deadly member of the family of viruses that cause smallpox, according to the CDC. Mpox may cause fever, chills, headaches, muscle aches, swollen lymph nodes, and painful rashes, particularly on the hands, feet, face, chest, mouth, or near the genitals. According to the CDC, the disease can spread through contact with infected wild animals, close (including sexual) contact with an infected individual, including contact with scabs or body fluids, or contact with contaminated materials such as towels or bedding.

The current outbreak involves an mpox strain known as clade I, which is especially virulent and dangerous to infants and children under the age of 5, according to the World Health Organization (WHO), whose director general announced this week that he was convening a panel of experts to advise him whether the outbreak should be declared a global health emergency. (The WHO called an end to the 2022 mpox global health emergency in May 2023.) The WHO says there have been over 14,000 cases this year, with at least 511 deaths, according to STAT News. In the Democratic Republic of Congo (DRC), 62% of the deaths involved children under age 5. The current subtype appears to be spread through routine close contact between individuals, though in November 2023 the WHO confirmed that this strain was also being sexually transmitted.

This deadlier strain of monkeypox has not been reported outside central and east Africa, the CDC said.

A different strain of mpox in the 2022 outbreak, known as the clade II subtype, which spread across the United States, was less deadly and largely transmitted through sexual contact, and men who have sex with men were at higher risk of the disease. That earlier strain never disappeared entirely, though new cases are at a much lower level, according to the CDC. The majority of cases are in people who are not vaccinated against mpox or have received only one of the two recommended doses, the CDC reported.

Vaccination against mpox

While knowledge concerning mpox has declined significantly, there has been a less pronounced drop in people’s intentions to get vaccinated against the disease. The CDC has urged individuals to be vaccinated with two doses of the vaccine Jynneos four weeks apart – both for people who have been exposed to mpox virus to help prevent its spread and for people with risk factors for mpox, including men who have sex with men.

An earlier APPC survey, in October 2022, found that 76% of respondents said they were “very likely” or “somewhat likely” to get an mpox vaccine if they were exposed to mpox. The current survey, in July 2024, found a slight decline – 70% of respondents reported that they were either very/somewhat likely to get the vaccine (68%) or were already vaccinated against mpox (2%). However, 3 in 10 (30%) said they were “not too likely” or “not at all likely” to get vaccinated against mpox if exposed to the virus. In addition, 70% reported in July 2024 that they thought the benefits of vaccination against mpox outweighed the risks.

Knowledge about mpox 

Responses to knowledge questions concerning mpox, from Annenberg Public Policy Center ASAPH surveys in July and August 2022 and July 2024.

Likelihood of mpox vaccination 

The likelihood of mpox vaccination, from the Annenberg Public Policy Center's ASAPH survey in August and October 2022 and July 2024.

Credit

Annenberg Public Policy Center

APPC’s ASAPH survey

The survey data come from the 20th wave of a nationally representative panel of 1,496 U.S. adults, first empaneled in April 2021, conducted for the Annenberg Public Policy Center by SSRS, an independent market research company. This wave of the Annenberg Science and Public Health Knowledge (ASAPH) survey was fielded July 11-18, 2024, and has a margin of sampling error (MOE) of ± 3.6 percentage points at the 95% confidence level. All figures are rounded to the nearest whole number and may not add to 100%. Combined subcategories may not add to totals in the topline and text due to rounding.

Download the topline and methodology statement.

The policy center has been tracking the American public’s knowledge, beliefs, and behaviors regarding vaccination, Covid-19, mpox, flu, maternal health, climate change, and other consequential health issues through this Annenberg Science and Public Health (ASAPH) knowledge survey panel for over three years. In addition to Jamieson, the APPC team includes senior data analyst Laura Gibson; research analyst Shawn Patterson Jr.; Patrick E. Jamieson, director of the Annenberg Health and Risk Communication Institute, and Ken Winneg, managing director of survey research.

The Annenberg Public Policy Center was established in 1993 to educate the public and policy makers about communication’s role in advancing public understanding of political, science, and health issues at the local, state, and federal levels.

---

Method of Research

Survey

 

Researchers find unexpectedly large methane source in overlooked landscape

University of Alaska Fairbanks

 

image: 

The study’s research team samples soil cores at a site near Fairbanks, Alaska, in winter.

view more 

Credit: Photo by Katey Walter Anthony

When Katey Walter Anthony heard rumors of methane, a potent greenhouse gas, ballooning under the lawns of fellow Fairbanks residents, she nearly didn’t believe it.

“I ignored it for years because I thought ‘I am a limnologist, methane is in lakes,’” she said.

But when a local reporter contacted Walter Anthony, who is a research professor at the Institute of Northern Engineering at University of Alaska Fairbanks, to inspect the waterbed-like ground at a nearby golf course, she started to pay attention. Like others in Fairbanks, they lit “turf bubbles” on fire and confirmed the presence of methane gas.

Then, when Walter Anthony looked at nearby sites,  she was shocked that methane wasn’t just coming out of a grassland. “I went through the forest, the birch trees and the spruce trees, and there was methane gas coming out of the ground in large, strong streams,” she said.

“We just had to study that more,” Walter Anthony said.

With funding from the National Science Foundation, she and her colleagues launched a comprehensive survey of dryland ecosystems in Interior and Arctic Alaska to determine whether it was a one-off oddity or unforeseen concern.

Their study, published in the journal Nature Communications this July, reported that upland landscapes were releasing some of the highest methane emissions yet documented among northern terrestrial ecosystems. Even more, the methane consisted of carbon thousands of years older than what researchers had previously seen from upland environments.

“It’s a totally different paradigm from the way anyone thinks about methane,” Walter Anthony said.

Because methane is 25 to 34 times more potent than carbon dioxide, the discovery brings new concerns to the potential for permafrost thaw to accelerate global climate change.

The findings challenge current climate models, which predict that these environments will be an insignificant source of methane or even a sink as the Arctic warms.

Typically, methane emissions are associated with wetlands, where low oxygen levels in water-saturated soils favor microbes that produce the gas. Yet methane emissions at the study’s well-drained, drier sites were in some cases higher than those measured in wetlands.

This was especially true for winter emissions, which were five times higher at some sites than emissions from northern wetlands.

Digging into the source

“I needed to prove to myself and everyone else that this is not a golf course thing,” Walter Anthony said.

She and colleagues identified 25 additional sites across Alaska’s dry upland forests, grasslands and tundra and measured methane flux at over 1,200 locations year-round across three years. The sites encompassed areas with high silt and ice content in their soils and signs of permafrost thaw known as thermokarst mounds, where thawing ground ice causes some parts of the land to sink. This leaves behind an “egg carton” like pattern of conical hills and sunken trenches.

The researchers found all but three sites were emitting methane.

The research team, which included scientists at UAF’s Institute of Arctic Biology and the Geophysical Institute, combined flux measurements with an array of research techniques, including radiocarbon dating, geophysical measurements, microbial genetics and directly drilling into soils.

They found that unique formations known as taliks, where deep, expansive pockets of buried soil remain unfrozen year-round, were likely responsible for the elevated methane releases.

These warm winter havens allow soil microbes to stay active, decomposing and respiring carbon during a season that they normally wouldn’t be contributing to carbon emissions. 

Walter Anthony said that upland taliks have been an emerging concern for scientists because of their potential to increase permafrost carbon emissions. “But everyone's been thinking about the associated carbon dioxide release, not methane,” she said.

The research team emphasized that methane emissions are especially high for sites with Pleistocene-era Yedoma deposits. These soils contain large stocks of carbon that extend tens of meters below the ground surface. Walter Anthony suspects that their high silt content prevents oxygen from reaching deeply thawed soils in taliks, which in turn favors microbes that produce methane.

Walter Anthony said it’s these carbon-rich deposits that make their new discovery a global concern. Even though Yedoma soils only cover 3% of the permafrost region, they contain over 25% of the total carbon stored in northern permafrost soils. 

The study also found through remote sensing and numerical modeling that thermokarst mounds are developing across the pan-Arctic Yedoma domain. Their taliks are projected to be formed extensively by the 22nd century with continued Arctic warming.

“Everywhere you have upland Yedoma that forms a talik, we can expect a strong source of methane, especially in the winter,” Walter Anthony said.

“It means the permafrost carbon feedback is going to be a lot bigger this century than anybody thought,” she said.

 

---

Journal

Nature Communications

DOI

10.1038/s41467-024-50346-5 

Article Title

Upland Yedoma taliks are an unpredicted source of atmospheric methane