High ozone exposure linked to increased mortality: new insights from a comprehensive Chinese National Cohort study

Peer-Reviewed Publication

CHINESE SOCIETY FOR ENVIRONMENTAL SCIENCES

 

IMAGE: GRAPHICAL ABSTRACT view more 

CREDIT: ENVIRONMENTAL SCIENCE AND ECOTECHNOLOGY

In a new study published in Volume 15 of the journal Environmental Science and Ecotechnology, researchers from Wuhan University of Science and Technology revealed that even a modest increase of 10 μg m−3 in O3 concentration was associated with a hazard ratio of 1.18 for all-cause mortality, indicating an 18% higher risk of death. The investigation encompassed a robust cohort of 20,882 participants nationwide and spanned a comprehensive seven-year period from 2011 to 2018. An intriguing aspect of this study is its particular focus on warm-season O3 exposure, which, despite the implementation of the Air Pollution Prevention and Control Action Plan in 2013, remains a significant concern in China. Furthermore, the relationship between long-term O3 exposure and mortality risk exhibited a J-shaped pattern, implying a non-linear association with a potential threshold of O3 concentration. A crucial discovery highlights that people in colder climates face heightened mortality risks due to long-term O3 exposure. This underscores the necessity of considering geographical and climate factors when assessing the health impacts of air pollution. The study also revealed a notable regional discrepancy, with China exhibiting higher risk estimates than recent estimates from Europe and North America. These variations could be attributed to variances in exposure metrics, population susceptibility, and generally lower O3 concentrations in developed nations.

Highlights

•A national cohort study on O3 exposure and all-cause mortality is conceived in China.

•Long-term O3 exposure is associated with increased mortality risk.

•A J-shaped O3-mortality relationship is identified in middle-aged and older adults.

However, it is essential to note that despite the significant findings, the study had certain limitations. The assessment of O3 exposure was based on data at the city level rather than individual-level exposure Furthermore, the study did not consider factors such as indoor O3 exposure and potential unmeasured confounders (e.g., traffic noise or other climatic factors). Additionally, the lack of clinical diagnoses regarding the cause of death restricts the exploration of associations between O3 exposure and cause-specific mortality.

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References

Funding information

Youth Fund Project of Humanities and Social Sciences Research of the Ministry of Education (21YJCZH229).

DOI

10.1016/j.ese.2023.100241

About Environmental Science and Ecotechnology

Environmental Science and Ecotechnology (ISSN 2666-4984) is an international, peer-reviewed, and open-access journal published by Elsevier. The journal publishes significant views and research across the full spectrum of ecology and environmental sciences, such as climate change, sustainability, biodiversity conservation, environment & health, green catalysis/processing for pollution control, and AI-driven environmental engineering. ESE received its latest impact factor of 12.6, according to the Journal Citation ReportTM 2022.

The C–R curve for O3 and all-cause mortality was fitted using a natural cubic spline. A nonlinear association between long-term O3 exposure and mortality risk (P for nonlinearity < 0.001) was observed at 60.7–142.4 μg m−3. Intuitively, we observed a J-shaped relationship, revealing a relatively flat curve as O3 levels fell below approximately 110 μg m−3, while the slope (i.e., increase in mortality risk) was steeper at higher concentrations.

CREDIT

Environmental Science and Ecotechnology

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JOURNAL

Environmental Science and Ecotechnology

DOI

10.1016/j.ese.2023.100241 

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Excess mortality associated with high ozone exposure: A national cohort study in China

Eyes in the skies confirm the end of trash burning in the Maldives

A new AI approach needs only a small amount of visual data to identify and track plumes of smoke in satellite imagery

Peer-Reviewed Publication

DUKE UNIVERSITY

 

IMAGE: PLUMES OF SMOKE FROM BURNING TRASH RISE FROM THILAFUSHI ISLAND IN THE MALDIVES. NEW RESEARCH USING SATELLITE IMAGERY WAS ABLE TO CONFIRM THAT A RECENT BAN ON THE PRACTICE HAS BEEN EFFECTIVE AT ELIMINATING SUCH POLLUTION. view more 

CREDIT: CREATIVE COMMONS BY IBRAHIM ASAD

DURHAM, N.C. – White sand beaches. Crystalline waters. Toxic smoke plumes wafting across a paradise clogged with plastic trash. 

That was the Republic of Maldives in early 2021, which prompted its government to ban open trash burning and single-use plastics later that year. But until recently, uncertainty remained as to whether or not the government actually put its money where its mouth was and enforced the policy changes.

New research from Duke University which used advanced AI techniques to analyze satellite images of the nation of islands in the middle of the Indian Ocean has demonstrated that the government’s ban on open burning has indeed effectively stamped out the smoke plumes.

This approach has the potential to spot similar plumes generated by wildfires, power plants, or industrial facilities. The findings were published on July 7th in Environmental Science & Technology Letters.

The Maldives is made of 1200 islands. Its largest, Male, is one of the most densely populated places on earth, generating hundreds of tons of waste every day. A nearby artificial island named Thilafushi serves as its dump — but at sea level, much of the plastic trash deposited there was washing into the ocean. Much more of it was being burned, sending toxic smoke drifting across the islands and pristine Indian Ocean. There was massive plastic contamination at every level.

Mike Bergin, the Sternberg Family Professor of Civil & Environmental Engineering at Duke, runs a large global air quality program that uses low-cost sensors to gather information. Bergin’s group was working with collaborators in the Maldives to install air quality sensors when he first heard about the situation on Thilafushi. He wanted to know what kind of air quality data was available for the island country, so he turned to satellite imagery from a commercial data company called PlanetLabs. What he saw troubled him. 

“The island was smoking all the time,” said Bergin. He asked colleague David Carlson, assistant professor of civil and environmental engineering at Duke and a machine learning expert, if there was anything they could do to help track who was being exposed to the toxic smoke.  

The two decided to develop an AI tool that used advanced image segmentation and something called transfer learning to examine satellite imagery of the island to see whether or not they could identify the smoke plumes from space. 

Soon after Bergin and Carlson began, however, the Maldivian government banned both trash burning and single-use plastics on its islands. The massive policy changes created a unique opportunity for the pair to see whether an AI tool could tell the difference between images of Thilafushi before and after the ban — and to confirm whether the ban had actually been enacted.

Training AI tools to recognize a certain shape usually requires thousands of images, but environmental applications generally don’t have huge data sets to work from. To get around this shortfall, the team turned to an approach called transfer learning, which borrows from lessons already learned by existing convolutional neural networks trained on similar tasks, allowing the AI to gain accuracy from far fewer images.

Carlson started with a model trained on a canonical image recognition task — classifying an unnamed animal as either a cat or a dog. “It initializes your AI tool, so that when you apply it in a new area, the established baseline allows it to succeed with far less data,” said Carlson. 

Image segmentation — the ability of an AI tool to recognize a shape and lift it from the background — has gotten a lot better in recent years, and those advances also played a big role. “Highlighting the area in each image that might be a plume provides a lot of additional information to the AI tool, so that it continues to learn,” said Carlson. “Localized info teaches it exactly what is relevant, so that it gets better and better at the task.”

They were then able to apply their AI tool to the image classification problem at hand. The verdict? There were no smoke plumes in the images of Thilafushi after the burning ban was instated. 

And after comparing the AI’s abilities against its human teachers’, the researchers found that the tool achieved 88% accuracy in its classification task. Through the process, it also learned the typical shape of a plume and how to distinguish between plumes and clouds, which have similar diffuse boundaries.

“Asking a human to identify a plume is such an objective task,” said CEE PhD student Sarah Scott, the paper’s first author. “That’s why we had several people performing it, and why we blended plume images together  — to show how different people might perceive the shapes. But the computer is looking at when the signals change within the image, pixel by pixel. Humans can’t see change at that level.” 

“The results were impressive, and confirmed the time the ban was implemented,” said Noora Khaleel, a PhD student at the University of Malaya, who worked with the Duke team on the project. “It is encouraging for a small developing country like the Maldives to be recognized for its efforts to regulate environmental problems.”

In the future, if the AI tool is made more robust — something that Carlson and Bergin acknowledge will take much more data and the participation of a large citizen science effort — it could give people more power to surveil numerous environmental problems around the world.

“It would be amazing to be able to scan for plumes, find them and keep track of them,” said Bergin. “We could let the public know when they’re being exposed to pollution from plumes, and they could hold parties accountable to clean up their acts.”  

This material is based upon work supported by the Department of Energy/National Nuclear Security Administration (DE-NA0003921) and a grant from the US Department of State.

CITATION: “Identifying Waste Burning Plumes Using High Resolution Satellite Imagery and Machine Learning: A Case Study in the Maldives,” Sarah R. Scott, Philemon E. Hailemariam, Prakash V. Bhave, Michael H. Bergin, David E. Carlson. Environmental Science & Technology Letters, July 7, 2023. DOI: 10.1021/acs.estlett.3c00225

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JOURNAL

Environmental Science & Technology Letters

DOI

10.1021/acs.estlett.3c00225 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Identifying Waste Burning Plumes Using High Resolution Satellite Imagery and Machine Learning: A Case Study in the Maldives

Drexel’s titanium oxide material lets sunlight drive green hydrogen production

Stable photocatalyst material opens new possibilities for harvesting hydrogen

Peer-Reviewed Publication

DREXEL UNIVERSITY

 

IMAGE: RESEARCHERS FROM DREXEL UNIVERSITY AND THE NATIONAL INSTITUTE OF MATERIALS PHYSICS IN ROMANIA, HAVE DISCOVERED A TITANIUM OXIDE-BASED PHOTOCATALYTIC MATERIAL THAT COULD OPEN A NEW PATH FOR GREEN HYDROGEN PRODUCTION. view more 

CREDIT: DREXEL UNIVERSITY

Clean energy plans, including the U.S. Infrastructure Investment Act’s “Clean Hydrogen Road Map,” are counting on hydrogen as a fuel of the future. But current hydrogen separation technology is still falling short of efficiency and sustainability goals. As part of ongoing efforts to develop materials that could enable alternative energy sources, researchers in Drexel University’s College of Engineering have produced a titanium oxide nanofilament material that can harness sunlight to unlock the ubiquitous molecule’s potential as a fuel source.

The discovery offers an alternative to current methods that generate greenhouse gas and require a great deal of energy. Photocatalysis, a process that can split hydrogen from water using only sunlight, has been explored for several decades, but has remained a more distant consideration because the catalyst materials enabling the process can only survive it for a day or two, which limits its long-term efficiency and, as a result, its commercial viability.

Drexel’s group, led by College of Engineering researchers Michel Barsoum, PhD, and Hussein O. Badr, PhD, in collaboration with scientists from the National Institute of Materials Physics in Bucharest, Romania, recently reported its discovery of photocatalytic titanium oxide-based, one-dimensional nanofilament material that can help sunlight glean hydrogen from water for months at a time. Their article “Photo-stable, 1D-nanofilaments TiO2-based lepidocrocite for photocatalytic hydrogen production in water-methanol mixtures,” published in the journal Matter, presents a sustainable and affordable path for creating hydrogen fuel, according to the authors.

“Our titanium oxide one-dimensional nanofilaments photocatalyst showed activity that is substantially higher — by an order of magnitude — than its commercial titanium oxide counterpart,” Hussein said. “Moreover, our photocatalyst was found to be stable in water for 6 months — these results represent a new generation of photocatalysts that can finally launch the long-awaited transition of nanomaterials from lab to market.”

Barsoum’s group discovered hydroxides-derived nanostructures (HDNs) — the family of titanium oxide nanomaterials, to which the photocatalytic material belongs — two years ago, as it was working out a new process for making MXene materials, which Drexel researchers are exploring for a number of applications. Instead of using the standard, caustic hydrofluoric acid to chemically etch out the layered two-dimensional MXenes from a material called a MAX phase, the group used an aqueous solution of a common organic base, tetramethylammonium hydroxide.

But rather than producing a MXene, the reaction produced thin, fibrous titanium oxide-based strands — that the team would come to find possessed the ability to facilitate the chemical reaction that splits hydrogen out of water molecules when exposed to sunlight.

“Titanium-oxide materials have previously demonstrated photocatalytic abilities, so testing our new nanofilaments for this property was a natural part of our work,” he said. “But we did not expect to find that not only are they photocatalytic, but they are extremely stable and productive catalysts for hydrogen production from water-methanol mixtures.”

The group tested five photocatalyst materials — titanium oxide-based HDNs, derived from various low-cost and readily available precursor materials — and compared them to Evonik Aeroxide’s titanium oxide material, called P25, which is widely accepted as the photocatalyst material closest to commercial viability.

Each material was submerged in a water-methanol solution and exposed to ultraviolet-visible light produced by a tunable illuminator lamp that mimics the spectrum of the sun. The researchers measured both the amount of hydrogen produced and duration of activity in each reactor assembly, as well as the number of photons from the light that produced hydrogen when they interacted with the catalyst material — a metric for understanding the catalytic efficiency of each material.

They found that all five titanium oxide-based HDNs photocatalysts performed more efficiently at using sunlight to produce hydrogen than the P25 material. One of them, derived from binary titanium carbide, is 10 times more efficient than P25 at enabling photons to split off hydrogen from the water.

This improvement is quite significant on its own, the team reports, but an even more significant finding was that the material remained active after more than 180 days of exposure to the simulated sunlight.

“The fact that our materials appear to possibly be thermodynamically stable and photochemically active in water-methanol mixtures for extended durations cannot be overemphasized,” Hussein said. “Since our material is not costly to make, easy to scale up, and incredibly stable in water, its applications in various photocatalytic processes become worth exploring.”

The next step for the research is better understanding why the material behaves this way, so it can be further optimized as a photocatalyst. The team’s current theory posits that the one-dimensional nature and theoretical high surface area of the material contribute to its sustained activity, but additional testing is needed to confirm these suggestions.

The group is also working to find other additives, aside from methanol, to serve as “hole quenchers” — chemicals that prevent the water-splitting reaction from reversing course, which is a common occurrence due to the somewhat chaotic nature of photocatalytic reactions.

The results are so promising that the group has founded a green hydrogen startup around the technology and is working with the Drexel Office of Innovation and the National Science Foundation’s Innovation Corps to move toward commercializing it.

“We are very excited about the possibilities of this discovery,” Barsoum said. “The world needs massive new clean fuels that can supplant fossil fuels. We believe this material can unlock the potential of green hydrogen.”

In addition, the group is exploring a number of other applications for HDNs, including using them in batteries, solar cells, water purification and medical treatments. Their ability to be easily and safely produced in large quantities, sets HDNs apart from other nanomaterials, which opens them to a variety of possible uses, according to Hussein.

“Our HDNs family of nanostructures continue to impress the very different communities with whom we are collaborating. These titanium oxide nanofilaments can be used for number of applications including water purification, dye degradation, perovskite solar cells, lithium-ion and lithium-sulfur batteries, urea dialysis and breast cancer therapy, among many more.”

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JOURNAL

Matter

DOI

10.1016/j.matt.2023.05.026 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Photo-stable, 1D-nanofilaments TiO2-based lepidocrocite for photocatalytic hydrogen production in water-methanol mixtures

How businesses can cultivate wisdom

Peer-Reviewed Publication

UNIVERSITY OF FLORIDA

THAT DOG DON'T HUNT

We probably all know wise people, mentors and leaders who possess a certain perspective that radiates out and makes us appreciate their presence in our lives. But it can be hard to pinpoint the source of their wisdom. Sometimes it feels like wisdom is one of life’s little secrets, left only for wise people to truly understand.

Fortunately, Monika Ardelt has dedicated herself to revealing these secrets. For decades, Ardelt, a professor of sociology at UF, has studied what makes people wise and how this quality benefits wise individuals and their communities. Her research has established the essential components of wisdom and developed ways to measure the trait.

Ardelt has recently turned her attention to studying wisdom in organizations and businesses to understand how institutions can cultivate wisdom that benefits themselves and their communities. Wise organizations can deepen employee connection to the firm, reducing turnover and improving their work.

So we asked Ardelt about her latest research, which she published recently in the Business and Professional Ethics Journal with her graduate student Bhavna Sharma. They uncovered these elements of organizational wisdom and how businesses can ensure they act wisely.

Q: What is wisdom?

A: Wisdom includes three components: cognitive, reflective and compassionate. This is the three-dimensional wisdom model I developed based on earlier research by neuropsychologist Vivian Clayton.

Wise people don’t necessarily know more than other people, but they understand the deeper meaning of their knowledge and of life in general. They know about themselves, they know who they are. They know about their strengths, but they also know about their weaknesses. They also know how to interact with other people.

This introspection requires the reflective component. Wise people look at events from different angles. This also includes looking at yourself from different angles. In this way, one can judge oneself a little bit more objectively, see one’s own weaknesses. By seeing our own weaknesses, we might become more tolerant of the faults of others.

This tolerance reduces our own ego and therefore makes us more compassionate, which is the third dimension.

Those three dimensions work together and reinforce each other.

Q: What are the benefits of wisdom for individuals?

A: Wise individuals are able to look at things from different perspectives, develop compassion for others and for themselves and have a deeper understanding of life. People are better able to deal with the vicissitudes of life and hardships. Therefore, wise people tend to be more content and satisfied with life.

Q: What makes an organization wise?

A: The ultimate goal of a wise organization is to make the world a better place. That can be done through their products or services. But it’s also about providing a work environment for their employees to make a good living that helps the employees fulfill their potential and flourish.

Q: How do organizations develop wisdom?

A: In our latest study, we uncovered a particular connection to supervisor support. Having a supportive supervisor was linked to organizational wisdom and job fulfillment, which was itself associated with physical and subjective well-being. Wise organizations must develop supportive supervisors to most benefit their employees.

We also developed a new model for studying wise organizations. We merged the three-dimensional wisdom model I developed earlier with self-determination theory, which proposes that people flourish when their basic psychological needs of autonomy, competence, and relatedness are met.

In a wise organization, the cognitive dimension merges with competence. A wise organization serves and benefits all stakeholders. They want to benefit their customers, their employees, the surrounding community, and the environment. 

The reflective element of wisdom is reflected in the autonomy fostered by an organization. Wise organizations don’t treat their employees as pieces of machinery. They treat their employees as human beings and give them enough autonomy to decide how they want to do their work. And wise organizations give their employees enough time for reflection and recuperation so they can achieve a satisfactory work-life balance.

Lastly, the compassionate component of wisdom is tied to the relatedness nurtured in an organization. Organizations bolster relatedness by fostering an ethical and moral culture. This culture creates fairness, appreciation and respect for all employees. Fair pay is one component, because pay inequity does not create a feeling of togetherness but a feeling of separation.

Q: What are the benefits of being a wise organization?

A: You can imagine that an employee who feels fulfilled and energized at their job is more likely to give their all. In this way, wise organizations avoid high turnover or “quiet quitting” and hold on to employees that are committed to the organization.

But this is something we’re still testing. One particular question we have is: Does a wise organization succeed, particularly in the long term? We see some companies, like Purdue Pharma (which was fined heavily for misleading the public about the addictiveness of the opioid OxyContin), that were not acting wisely and have suffered for it. Is the reverse true as well, that wise organizations thrive over time? That’s something we want to answer.

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JOURNAL

Business and Professional Ethics Journal

DOI

10.5840/bpej2023614140 

ARTICLE TITLE

The Benefits of Wise Organizations for Employee Well-Being

Rising non-native cover in the Santa Monica Mountains threatens native biodiversity and increases fire risk

Analysis shows non-native cover is rising in the Santa Monica Mountains without the influence of fire since 2014, with compounding effects after the 2018 Woolsey Fire

Peer-Reviewed Publication

ARIZONA STATE UNIVERSITY

July 13, 2023 -- The National Park Service has been monitoring plants in hundreds of sites throughout the Santa Monica Mountains National Recreation Area in Southern California since 2014.

A new analysis of these data published in the journal Ecosphere shows a steady increase in non-native plant cover since 2014, and rapid regrowth of non-native annual grass and herbaceous species after the 2018 Woolsey Fire, which burned nearly 80% of the entire region.

Furthermore, a region of dense non-native cover was found in the Northern Simi Hills region where biodiversity is significantly low and the native species are at risk of further reduction.

These results indicate that the Santa Monica Mountains are at high risk of losing the native plants that support their unique ecosystem. In addition, the invasive plants that are spreading bring with them an increased risk of damaging wildfires.

Healthy native plant communities are typically resistant to invasion since they are uniquely adapted to Southern California’s dry climate. However, there has been a sharp increase in non-native cover from 4% in 2014 to 29% in 2018, before the Woolsey Fire. Ecosystem stressors such as changing climatic patterns, habitat fragmentation, and alterations in soil chemical properties reduce the resilience of the native plant communities and open the opportunity for invasion.

Nicoletta Stork, the lead author of the study and research analyst in Arizona State University’s Center for Global Discovery and Conservation Science says, “The rise in non-native cover identified in this study is a signal of ecosystem stress from intrinsic and extrinsic factors. The prolonged effects of chronic ecosystem stress are still unknown, but this study has shown a glimpse of the negative repercussions at this moment in time.”

Fire is typically beneficial for native plant communities in this region. However, when invasive seedbanks are prolific in the soil, the reduced shrub cover and newly available resources allow non-natives to germinate and spread. In the Santa Monica Mountains National Recreation Area, invasive non-native annual grasses and annual herbaceous plants regrew to exceed pre-fire cover percentages within a year after the Woolsey fire, reaching 34% in 2020, while native communities underwent natural, albeit slower, regrowth.

The speed at which non-natives regrew after the Woolsey Fire raises concerns as ecosystem stressors continue to affect native resiliency. Amy Mainzer, professor in the Lunar and Planetary Laboratory at the University of Arizona and co-author of the study notes, “This study shows that the weeds are spreading and becoming more prevalent in certain key areas after the fire, pointing to the need to locate and control them because they contribute to the increasing wildfires we are experiencing in the American Southwest.”

The invasive annuals seen growing in the Santa Monica Mountains National Recreation Area accumulate layers of senesced plant material that is easily ignitable, creating a fire hazard that threatens property, the ecosystem, and human lives.

Other negative effects of non-native invasion include reduced biodiversity and altered ecosystems, therefore, locating regions with high non-native cover is crucial to controlling the spread of invasive populations. From this study, a non-native hotspot was located in the Northern Simi Hills region where non-native annual grass species were prominent before the fire. After the fire, certain invasive annual grasses increased, along with invasive mustard and thistle species.

Assessment of the species diversity in this hotspot shows the non-native community is significantly less diverse than native communities. Furthermore, while native communities have notably high shrub cover, non-native communities are comprised of highly flammable annual grasses and herbaceous species.

Robin Martin, associate professor in the School of Ocean Futures at Arizona State University and co-author of the study mentions, “Conversion from one functional group to another is another aspect that can give insight into how ecosystem structure is changing. In this case, the transition from perennial shrublands to annual grasslands could have significant effects on the ecosystem’s hydrologic, carbon, and nutrient cycles, which can lead to more drastic positive feedback loops that eventually extinguish native species.”

Monitoring efforts such as the Park Service’s Inventory and Monitoring program provide insight into the non-native species that are most invasive and the native species that are most at risk of eradication or extinction. While more research must be done to identify the driving factors of invasive spread, studies like this one provide measures of how the ecosystem is changing over time and can point out the locations where management of invasive weeds is most essential.

 

Citation:

Stork, Nicoletta, Amy Mainzer, and Roberta Martin. 2023. “Native and Non-Native Plant Regrowth in the Santa Monica Mountains National Recreation Area after the 2018 Woolsey Fire.” Ecosphere 14(6): e4567. https://doi.org/10.1002/ecs2.4567

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JOURNAL

Ecosphere

DOI

10.1002/ecs2.4567 

METHOD OF RESEARCH

Meta-analysis

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Native and non-native plant regrowth in the Santa Monica Mountains National Recreation Area after the 2018 Woolsey Fire

A new method allows quantifying the spatial intermittency of ocean currents

The new methodology, developed by an ICM-CSIC team, accurately estimates the horizontal diffusion of water masses in different ocean regions

Peer-Reviewed Publication

SPANISH NATIONAL RESEARCH COUNCIL (CSIC)

 

IMAGE: THE NEW METHODOLOGY ACCURATELY ESTIMATES THE HORIZONTAL DIFFUSION OF WATER MASSES IN DIFFERENT OCEAN REGIONS view more 

CREDIT: INSTITUTO ESPAÑOL DE OCEANOGRAFÍA

Understanding Atlantic Ocean circulation is key for assessing the global ocean interconnections, in what is known as the "global conveyor belt". This is because the latitudinal ends of the Atlantic, bordering the polar regions, are cold-water formation regions that trigger the onset of the global conveyor belt. Because of their high density, each winter the waters of these polar regions sink and initiate the conveyor belt, thus helping to redistribute heat on a planetary scale, which ultimately influences the climate, especially in Europe.

To quantify this circulation on a planetary scale, it is necessary to understand the intensity of all those processes that cause the spatial and temporal intermittency of the large currents, i.e. the diffusive processes. A new study led by the Institut de Ciències del Mar (ICM-CSIC) in Barcelona, which delves into the processes of horizontal diffusion in the South Atlantic, has developed a new methodology for calculating this diffusion at both regional and global levels.

"The new methodology, which we have named ROD (Radial Offset by Diffusion), allows us to determine the horizontal diffusion coefficients in the ocean and to estimate their spatial variability," states Anna Olivé, leading author of the study.

To carry out this work, published in the prestigious Journal of Atmospheric and Oceanic Technology, researchers analysed the displacements, between 2002 and 2020, of more than 600 drifting buoys, that is, dragged buoys that drift with the ocean currents and hence allow knowing their direction and speed.

"We then numerically simulated these buoys’ trajectories and calculated the distance between the final position of the drifting buoys and that estimated with the numerical simulations, which allowed us to quantify the horizontal diffusive processes existing in the region," adds Anna Olivé.

The study shows that the maximum horizontal diffusion occurs near the ocean surface, in the first 200 m depth, while the minimum values are observed between 1400 and 2000 m depth. Diffusion also increases in the northernmost Antarctic fronts due to the presence of the strong Falkland Current, which flows northwards along the Atlantic coast of Patagonia, reaching La Plata River.

"This important spatial difference confirms the large variability of horizontal diffusion in the ocean, which highlights that a constant coefficient cannot be used throughout the ocean," explains Josep Lluís Pelegrí, co-author of the study.

Unlike others, the ROD method is easy to implement and does not require excessive computational use. According to Anna Olivé, "this facilitates its application and makes it an effective tool for understanding the processes of diffusion and turbulent mixing in regions as dynamic as the Antarctic fronts".

For example, the new methodology will make it possible to know which horizontal diffusion coefficient is most appropriate for studying each oceanic region. Until now, the uncertainties in this parameter has limited the predictive capacity of oceanographic numerical models.

"Thanks to the increase in the number of drifting buoys and the continuous improvements in high-resolution numerical models and reanalysis, the ROD method will provide us with more precise estimates that will allow us to better predict the temporal evolution of large-scale processes that have a major impact on the climate of our planet, such as the global conveyor belt," concludes Anna Olivé.

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JOURNAL

Journal of Atmospheric and Oceanic Technology

DOI

10.1175/JTECH-D-22-0097.1 

METHOD OF RESEARCH

Observational study

ARTICLE TITLE

A Simple Method for Estimating Horizontal Diffusivity

Despite doubts from quantum physicists: Einstein's theory of relativity reaffirmed

Research teams from Leibniz University Hannover and University of Bremen confirm another equivalence principle

Peer-Reviewed Publication

LEIBNIZ UNIVERSITY HANNOVER

 

IMAGE: BINARY SYSTEM EARTH-MOON view more 

CREDIT: AEOS MEDIALAB, ESA 2002

Joint press release by Leibniz University Hannover and ZARM of the University of Bremen

One of the most basic assumptions of fundamental physics is that the different properties of mass – weight, inertia and gravitation – always remain the same in relation to each other. Without this equivalence, Einstein's theory of relativity would be contradicted and our current physics textbooks would have to be rewritten. Although all measurements to date confirm the equivalence principle, quantum theory postulates that there should be a violation. This inconsistency between Einstein's gravitational theory and modern quantum theory is the reason why ever more precise tests of the equivalence principle are particularly important. A team from the Center of Applied Space Technology and Microgravity (ZARM) at University of Bremen, in collaboration with the Institute of Geodesy (IfE) at Leibniz University Hannover, has now succeeded in proving with 100 times greater accuracy that passive gravitational mass and active gravitational mass are always equivalent – regardless of the particular composition of the respective masses. The research was conducted within the framework of the Cluster of Excellence "QuantumFrontiers". Today, the team published their findings as a highlights article in the scientific journal "Physical Review Letters".

 

Physical context
Inertial mass resists acceleration. For example, it causes you to be pushed backwards into your seat when the car starts. Passive gravitational mass reacts on gravity and results in our weight on Earth. Active gravitational mass refers to the force of gravitation exerted by an object, or more precisely, the size of its gravitational field. The equivalence of these properties is fundamental to general relativity. Therefore, both the equivalence of inertial and passive gravitational mass and the equivalence of passive and active gravitational mass are being tested with increasing precision.

What was the study about?
If we assume that passive and active gravitational mass are not equal – that their ratio depends on the material – then objects made of different materials with a different centre of mass would accelerate themselves. Since the Moon consists of an aluminium shell and an iron core, with centres of mass offset against each other, the Moon should accelerate. This hypothetical change in speed could be measured with high precision, via "Lunar Laser Ranging". This involves pointing lasers from Earth at reflectors on the Moon placed there by the Apollo missions and the Soviet Luna programme. Since then, round trip travel times of laser beams are recorded. The research team analysed “Lunar Laser Ranging” data collected over a period of 50 years, from 1970 to 2022, and investigated such mass difference effects. Since no effect was found, this means that the passive and active gravitational masses are equal to approximately 14 decimal places. This estimate is a hundred times more accurate than the best previous study, dating back to 1986.

Unique expertise
LUH's Institute of Geodesy – one of only four centres worldwide analysing laser distance measurements to the Moon – has unique expertise in assessing the data, particularly for testing general relativity. In the current study, the institute analysed the Lunar Laser Ranging measurements, including error analysis and interpretation of the results.

Vishwa Vijay Singh, Jürgen Müller and Liliane Biskupek from the Institute of Geodesy at Leibniz University Hannover, as well as Eva Hackmann and Claus Lämmerzahl from the Center of Applied Space Technology and Microgravity (ZARM) at the University of Bremen published their findings in the journal Physical Review Letters, where the paper was highlighted in the category "editors' suggestion”.

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JOURNAL

Physical Review Letters

DOI

10.1103/PhysRevLett.131.021401 

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Equivalence of active and passive gravitational mass tested with lunar laser ranging

ARTICLE PUBLICATION DATE

13-Jul-2023