The Arctic is rapidly losing sea ice, and less ice means more open water, and more open water means more gas and aerosol emissions from the ocean into the air, warming the atmosphere and making it cloudier.
So when researchers from the lab of University of Michigan aerosol scientist Kerri Pratt collected aerosols from the Arctic atmosphere during summer 2015, Rachel Kirpes, then a doctoral student, discovered a curious thing: Aerosolized ammonium sulfate particles didn’t look like typical liquid aerosols.
Working with fellow aerosol scientist Andrew Ault, Kirpes discovered that ammonium sulfate particles, which should have been liquid, were actually solid. The team’s results are published in the Proceedings of the National Academy of Sciences.
Solid aerosols can change how clouds form in the Arctic. And, as the Arctic loses ice, researchers expect to see more of these unique particles formed from oceanic emissions combined with ammonia from birds, which will impact cloud formation and climate. Additionally, understanding the characteristics of aerosols in the atmosphere is critical for improving the ability of climate models to predict current and future climate in the Arctic and beyond.
“The Arctic is warming faster than anywhere else in the world. As we have more emissions from open water in the atmosphere, these types of particles could become more important,” said Pratt, associate professor of chemistry, and earth and environmental sciences. “These types of observations are so critical because we have so few observations to even evaluate the accuracy of models of the Arctic atmosphere.
“With so few observations, sometimes you get surprises like this when you make measurements. These particles didn’t look like anything we had ever seen in the literature, in the Arctic, or anywhere else in the world.”
The aerosols observed in the study were up to 400 nanometers, or about 300 times smaller than the diameter of a human hair. Ault, associate professor of chemistry, says that aerosols in the Arctic are typically assumed to be liquid.
Once the relative humidity of the atmosphere reaches 80%—about the level of a humid day—the particle becomes liquid. When you dry the aerosol back out, it doesn’t turn into a solid until the relative humidity is about 35%-40%. Because the air over the Arctic Ocean—or any ocean—is humid, researchers expect to see liquid aerosols.
“But what we saw is a pretty new phenomenon where a small particle collides with our droplets when it’s below 80% humidity, but above 40% humidity. Essentially, this provides a surface for the aerosol to solidify and become a solid at a higher relative humidity than you would have expected,” Ault said.
“These particles were much more like a marble than a droplet. That’s really important, particularly in a region where there haven’t been a lot of measurements because those particles can eventually end up acting as the seeds of clouds or having reactions happen on them.”
Additionally, the researchers say, the size, composition and phase of atmospheric aerosols impact climate change through water uptake and cloud formation.
“It’s our job to keep helping modelers refine their models,” Ault said. “It’s not that the models are wrong, but they always need more new information as events on the ground change, and what we saw was something completely unexpected.”
Pratt’s team collected aerosols in August-September 2015 in Utqiaġvik, the northernmost point of Alaska. To do this, they used what’s called a multistage impactor, a device that has several stages that collect particles according to their size. Kirpes later analyzed these particles in Ault’s lab using microscopy and spectroscopy techniques that can examine the composition and phase of particles less than 100 nanometers in size.
“If we were to go back several decades when there was ice near the shore, even in August and September, we would not be observing these particles. We’re observing the consequences of this climate already changing,” Pratt said. “We need to have the reality captured in models that simulate clouds and the atmosphere, which are critical for understanding the energy budget of the Arctic atmosphere, for this place that is changing faster than anywhere else.”
More information: Rachel M. Kirpes et al, Solid organic-coated ammonium sulfate particles at high relative humidity in the summertime Arctic atmosphere, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2104496119
It looks like fireflies flickering in the darkness. Slowly, more and more amass, lighting up the screen in large chunks and clusters.
But this is not a video about insects. It’s a simulation of the early universe, a time after the Big Bang when the cosmos transformed from a place of utter darkness to a radiant, light-filled environment.
The stunning video is part of a large suite of simulations described in a series of three papers accepted to the Monthly Notices of the Royal Astronomical Society. Created by researchers at the Center for Astrophysics | Harvard & Smithsonian, the Massachusetts Institute of Technology and the Max Planck Institute for Astrophysics, the simulations represent a monumental advancement in simulating the formation of the first galaxies and reionization—the process by which neutral hydrogen atoms in space were transformed into positively charged, or ionized, hydrogen, allowing light to spread throughout the universe.
The simulated period, known as the epoch of reionization, took place some 13 billion years ago and was challenging to reconstruct, as it involves immensely complicated, chaotic interactions, including those between gravity, gas and radiation, or light.
“Most astronomers don’t have labs to conduct experiments in. The scales of space and time are too large, so the only way we can do experiments is on computers,” explains Rahul Kannan, an astrophysicist at the Center for Astrophysics and the lead author of the first paper in the series. “We are able to take basic physics equations and governing theoretical models to simulate what happened in the early universe.”
The team’s simulations—named Thesan after the Etruscan goddess of dawn—resolve interactions in the early universe with the highest detail and over the largest volume of any previous simulation. Physics in the early universe are captured down to scales that are a million times smaller than the simulated regions, providing unprecedented detail on properties of early galaxies and how light from these galaxies impacted gas.
The team accomplishes this by combining a realistic model of galaxy formation with a new algorithm that tracks how light interacts with gas, along with a model for cosmic dust.
With Thesan, researchers can simulate a piece of our universe spanning over 300 million light years across. The team can run the simulation forward in time to track and visualize the first appearance and evolution of hundreds of thousands of galaxies within this space, beginning around 400,000 years after the Big Bang, and through the first billion years.
The simulations reveal a gradual change in the universe from complete darkness to light.
“It’s a bit like water in ice cube trays; when you put it in the freezer, it does take time, but after a while it starts to freeze on the edges and then slowly creeps in,” says study co-author Aaron Smith, a NASA Einstein Fellow in MIT’s Kavli Institute for Astrophysics and Space Research. “This was the same situation in the early universe—it was a neutral, dark cosmos that became bright and ionized as light began to emerge from the first galaxies.”
The simulations were created to prepare for observations from the James Webb Space Telescope (JWST), which will be able to peer further back in time—approximately 13.5 billion years—than predecessors like the Hubble Space Telescope.
Evolution of simulated properties in the main Thesan run. Time progresses from left to right. The dark matter (top panel) collapse in the cosmic web structure, composed of clumps (haloes) connected by filaments, and the gas (second panel from the top) follows, collapsing to create galaxies. These produce ionising photons that drive cosmic reionization (third panel from the top), heating up the gas in the process (bottom panel). Credit: Credits: THESAN Simulations
“A lot of telescopes coming online, like the JWST, are specifically designed to study this epoch,” Kannan says. “That’s where our simulations come in; they are going to help us interpret real observations of this period and understand what we’re seeing.”
Real telescope observations and data will soon be compared to Thesan simulations, the team explains.
“And thats the interesting part,” says study co-author Mark Vogelsberger, an associate professor of physics at MIT. “Either our Thesan simulations and model will agree with what JWST finds, which would confirm our picture of the universe, or there will be a significant disagreement showing that our understanding of the early universe is wrong.”
The team, however, won’t know how various aspects of their model fares until the first observations roll in, which will cover a wide range of topics, including galaxy properties and the absorption and escape of light in the early universe.
“We have developed simulations based on what we know,” Kannan says. “But while the scientific community has learned a lot in recent years, there is still quite a bit of uncertainty, especially in these early times when the universe was very young.”
The simulations were created using one of the world’s largest supercomputers, the SuperMUC-NG, over the course of 30 million CPU-hours. The same simulations would have required more than 3,500 years to complete on a normal computer.
More information: The THESAN project: Lyman-α emission and transmission during the Epoch of Reionization , Monthly Notices of the Royal Astronomical Society (2022). DOI: 10.1093/mnras/stac713 , academic.oup.com/mnras/advance … nras/stac713/6553849
Helium-3, a rare isotope of helium gas, is leaking out of Earth’s core, a new study reports. Because almost all helium-3 is from the Big Bang, the gas leak adds evidence that Earth formed inside a solar nebula, which has long been debated.
Helium-3 has been measured at Earth’s surface in relatively small quantities. But scientists did not know how much was leaking from the Earth’s core, as opposed to its middle layers, called the mantle.
The new study pins down the core as a major source of helium-3 on the Earth. Some natural processes can generate helium-3, such as the radioactive decay of tritium, but helium-3 is made primarily in nebulae—massive, spinning clouds of gas and dust like the one that gave rise to our Solar System. Because helium is one of the earliest elements produced in the universe, most helium-3 can be traced back to the Big Bang.
As a planet grows, it accumulates material from its surroundings, so its composition reflects the environment in which it formed. To get high concentrations of helium-3 deep in the core, Earth would have had to form inside a thriving solar nebula, not on its fringes or during its waning phase.
The new research adds further clues to the mystery surrounding Earth’s formation, lending additional evidence to the theory that our planet formed inside the solar nebula.
The study was published in the AGU journal Geochemistry, Geophysics, Geosystems, which publishes research on the chemistry, physics, geology and biology of Earth and planetary processes.
About 2,000 grams of helium-3 leak out of the Earth every year, “about enough to fill a balloon the size of your desk,” said lead study author Peter Olson, a geophysicist at the University of New Mexico. “It’s a wonder of nature, and a clue for the history of the Earth, that there’s still a significant amount of this isotope in the interior of the Earth.”
The researchers modeled helium during two key stages of Earth’s history: early formation, when the planet was accumulating helium, and following the formation of the Moon, after which helium was lost. Evidence suggests an object one-third the size of the Earth hit the planet early in its history, around 4 billion years ago and that impact would have re-melted the Earth’s crust, allowing much of the helium to escape. The gas continues escaping to this day.
Using the modern helium-3 leak rate along with models of helium isotope behavior, the researchers estimated there are between 10 teragrams (1013 grams) to a petagram (1015 grams) of helium-3 in the core—a vast quantity that Olson said points to Earth’s formation inside the solar nebula, where high concentrations of the gas would have allowed it to build up deep in the planet.
However, future work looking for other nebula-created gasses, such as hydrogen, leaking in similar rates and locations as helium-3 could be a “smoking gun” for the core as the source, Olson said. “There are many more mysteries than certainties.”
More information: Peter L. Olson et al, Primordial Helium‐3 Exchange Between Earth’s Core and Mantle, Geochemistry, Geophysics, Geosystems (2022). DOI: 10.1029/2021GC009985
Mysterious giant jars that may have been used for burial rituals have been unearthed across four new sites in Assam, India. The discovery comes from a major collaboration involving researchers at The Australian National University (ANU).
The 65 newly discovered sandstone jars vary in shape and decoration, with some tall and cylindrical, and others partly or fully buried in the ground. Similar jars, some of which span up to three meters high and two meters wide, have previously been uncovered in Laos and Indonesia.
“We still don’t know who made the giant jars or where they lived. It’s all a bit of a mystery,” ANU Ph.D. student Nicholas Skopal said.
Another mystery is what the giant jars were used for. The researchers believe it is likely they were associated with mortuary practices.
“There are stories from the Naga people, the current ethnic groups in north-east India, of finding the Assam jars filled with cremated remains, beads and other material artifacts,” Mr. Skopal said. This theory aligns with findings from the other jar sites in countries including Laos, which are also tied to burial rituals.
Initially, the aim of the new research was to survey the existing sites in Assam. However, as the researchers moved about the landscape they realized there was more to be uncovered. ”At the start the team just went in to survey three large sites that hadn’t been formally surveyed. From there grids were set up to explore the surrounding densely forested regions,” Mr. Skopal said. ”This is when we first started finding new jar sites. The team only searched a very limited area so there are likely to be a lot more out there, we just don’t yet know where they are.”
The surveying and reporting of these sites is of great importance in regards to heritage management in India.
“It seems as though there aren’t any living ethnic groups in India associated with the jars, which means there is an importance to maintain the cultural heritage,” Mr. Skopal said. ”The longer we take to find them, the greater chance that they will be destroyed, as more crops are planted in these areas and the forests are cut down.”
The researchers worked with local communities on the ground to uncover potential jar sites, often through areas of mountainous jungle that were difficult to navigate.
“Once the sites have been recorded, it becomes easier for the government to work with the local communities to protect and maintain them so they are not being destroyed,” Mr. Skopal said.
The research was led by Tilok Thakuria, from North Eastern Hill University and Uttam Bathari, from Gauhati University.
The study’s findings are published in the Journal of Asian Archaeology.
The Federal Court recently quashed a duty of care owed by the environment minister to Australian children, to protect them from the harms of climate change.
The duty was attached to Australia’s federal environment law, the Environment Protection and Biodiversity Conservation (EPBC) Act. In reversing the decision that had established the duty, the new judgment shone a spotlight on the EPBC Act’s limitations. Or at least, it should have.
Much of the commentary around the judgment focused on lamenting the hands-off position the court took in its unwillingness to delve into so-called political territory.
Less attention was paid to a key take-home message: the EPBC Act gives the minister power to approve coal projects, even if they’ll have adverse effects.
It doesn’t, in a general sense, protect the environment from these effects. It doesn’t protect the public from consequent harm, even if deadly. And it doesn’t, actually, tackle climate change at all.
Alarmed? You should be.
Why the duty was quashed
The appeal was heard by three judges, each with a different opinion on why there shouldn’t be a duty.
One key problem was that the class of victims won’t just include the children represented in the case. Currently unborn children will be affected too. The judges also found issues with the minister’s relationship with the children given the intervening steps that will lead to climate change, extreme weather events, and future harm.
To help resolve novel disputes, courts look to previous cases. One case that featured prominently was about protecting the public from contaminated oysters. In that case, a council wasn’t liable for failing to prevent water pollution that caused hepatitis infection. In another case, where there was no way of identifying the source of asbestos fibers that caused mesothelioma, it was found that whoever materially increased the risk of harm could be liable for it.
The fact these were considered the most relevant cases just goes to show how unprecedented the problem of climate change is. There was no case directly on point, which could help with the complex and cumulative cause-and-effects.
The problem of ‘incoherence’
Another important problem for two of the three judges was that the duty wasn’t coherent—meaning consistent or compatible—with the EPBC Act. That’s because the EPBC Act doesn’t squarely address climate change or human safety, and yet the duty concerns precisely those two things.
For decades, it’s been recognized that humans depend on the environment for survival, and that a stable climate system is necessary for life as we know it.
The third judge thought the minister’s obligations, embedded in an environment protection framework, could therefore sit side by side with a duty of care. Our environment, he said, “is not just there to admire and objectify.”
But the other two were dissuaded by their view that the EPBC Act doesn’t in fact protect the environment in a general sense. Nor does it explicitly aim to mitigate climate change. It operates in a piecemeal way, rather than concerning ecosystems as a whole, or our dependency on them.
Can this really be how the EPBC Act operates in practice? Well, yes.
We heard this same message just recently via the ten-yearly, independent review of the legislation. It concluded that the EPBC Act is outdated, and not fit for the purpose of environment protection.
What does the EPBC Act do, then?
For the most part, the EPBC Act is an impact assessment law. It’s triggered when specific environmental matters, like individual threatened species, are likely to be harmed by a proposed project (such as a coal mine). When it’s triggered, it sets in motion a procedural process that requires the minister to consider whether to approve the project given its impacts.
Year after year, nearly every single project that is put forward is approved. In fact, the coal mine that was the subject of the case was approved even before the appeal went to court. This explains why so many, including the independent review, feel the EPBC Act doesn’t really do enough to adequately safeguard against environmental loss.
The review recommended the introduction of science-backed environmental standards. If this happened, it may be easier for courts to judge ministerial decisions, with a legal reference point for what’s considered politically acceptable. It also recommended decision-making incorporate climate scenarios.
BREAKING: The kids’ climate case, establishing a duty of care on the federal environment minister to protect young people from climate change has been overturned by the full bench of the federal court.
Back in 2020, I wrote that whether the children win or lose, their case would make a difference.
Although not over yet (they have two more weeks to lodge an application to appeal to the High Court), it already has. It’s drawn attention to the fact that Australia doesn’t have a climate law to protect its children. That it has no law to protect against harmful floods and fire that have already manifest since the case began. And it’s forced the Federal Court to acknowledge the uncontested risks of climate change.
Let’s look at this case as a call to action. The Federal Court has essentially said it can’t act. Reading the judgment closely, there are hints to suggest the High Court might be able to, and that eventually, the law will have to evolve to manage complex causation.
But the decision certainly doesn’t mean the government can’t act. In fact, that’s exactly who the judges indicated must.
As comets approach the Sun, they release gas and dust known to astronomers as cometary activity. For comets passing near or inside Earth’s orbit, this activity slows over successive orbits. University of Oklahoma astronomer Nathan Kaib has found this same comet-fading phenomenon occurs as comets make repeated passages through the more distant region beyond Saturn.
Kaib, an associate professor in the Homer L. Dodge Department of Physics and Astronomy in the Dodge Family College of Arts and Sciences at OU, is the lead author of the article “Comet Fading Begins Before Saturn,” published in Science Advances.
“Long-period comets, those that take at least hundreds of years to go around the Sun once, spend most of their lives thousands of times further from the Sun than the Earth is,” said Kaib. “However, sometimes they develop highly elliptical orbits and, in turn, make regular incursions toward the Sun and its nearby planets. As these comets approach the Sun, its intense heat turns their icy surfaces into gas.
This cometary activity is what gives comets their striking appearance in the sky and makes them relatively easy for astronomers to find. As extreme heating from the Sun steadily depletes their surface ice supply, the activity of comets passing near Earth diminishes, or fades, over time.”
In this study, Kaib discovered that this fading phenomenon also occurs among comets passing through the outer solar system near or beyond Saturn’s orbit. What makes his findings surprising is that such comets experience much weaker heating from the Sun compared to those nearer Earth. In fact, unlike nearer comets, the Sun’s heating is so weak that water-based ice cannot evaporate on these comets.
By running computer simulations of comets traveling near the outer solar system’s giant planets, Kaib showed the gravity of the giant planets quickly shrinks the orbits of distant comets so they make smaller excursions away from the Sun in between passages through the outer solar system.
“We should therefore expect that the outer solar system has many more comets on these shrunken orbits compared to those on larger orbits,” he said. “Instead, astronomers see the opposite; distant comets with shrunken orbits are almost entirely absent from astronomers’ observations, and comets with larger orbits dominate our census of the outer solar system. Rapid comet fading that occurs during this orbit-shrinking explains this paradox, since it will effectively make older comets invisible to astronomers’ searches.”
Given that distant comets are hard to study due to their remoteness, astronomers’ understanding of comets is mostly based on studying the ones on orbits near Earth. Kaib’s finding suggests that passages through the outer solar system may alter the physical properties of many near-Earth comets before they are discovered.
“Fading among distant comets was discovered by combining the results of computer simulations of comet production with the current catalog of known distant comets,” said Kaib. “These distant comets are faint and extremely difficult to detect, and comet-observing campaigns have taken great pains to build this catalog over the past 20 years. Without it, this current work would not have been possible.”
Kaib expects the Legacy Survey of Space and Time, a 10-year mission to survey the southern sky at the Vera C. Rubin Observatory in Chile, to rapidly increase comet discoveries.
“The comet fading characterized in my work will be critical to properly understanding and interpreting this imminent deluge of newly discovered comets,” he said.
The computer simulations for this work were performed at the OU Supercomputing Center for Education & Research. Kaib is currently on sabbatical leave at Case Western Reserve University in Cleveland, Ohio.
New research, led by the University of Massachusetts Amherst and published recently in the journal Climate of the Past, is the first to provide a continuous look at a shift in climate, called the Mid-Pleistocene Transition, that has puzzled scientists. Kurt Lindberg, the paper’s first author and currently a graduate student at the University at Buffalo, was only an undergraduate when he completed the research as part of a team that included world-renowned climate scientists at UMass Amherst.
Somewhere around 1.2 million years ago, a dramatic shift in the Earth’s climate, known as the Mid-Pleistocene Transition, or MPT, happened. Previously, ice ages had occurred, with relative regularity, every 40,000 years or so. But then, in a comparatively short window of geological time, the time between ice ages more than doubled, to every 100,000 years. “It’s a real puzzle,” says Isla Castañeda, professor of geosciences at UMass Amherst and one of the paper’s co-authors. “No one really knows why this shift occurred.”
One of the big barriers to understanding the MPT is that very little data exists. The oldest Arctic ice cores only go back approximately 125,000 years. And older sedimentary cores are almost nonexistent, because as ice ages have come and gone, the advancing and retreating ice sheets have acted like enormous bulldozers, scraping much of the exposed land down to bedrock.
However, there is one place in the world, in far northeastern Russia, that is both above the Arctic Circle and which has never been covered by glaciers: Lake El’gygytgyn. This is where the world-renowned polar scientist, Julie Brigham-Grette, professor of geosciences at UMass Amherst and one of the paper’s co-authors, comes in.
In 2009, Brigham-Grette led an international team of scientists to Lake El’gygytgyn, where they drilled a 685.5 meter sediment core, representing approximately the last 3.6 million years of Earth’s history. Lindberg and his co-authors used the portion of this sedimentary core that spanned the MPT and looked for specific biomarkers that could help them ascertain temperature and vegetation. With this information, they were able to reconstruct, for the first time, climactic conditions in the Arctic during the MPT.
While the team did not solve the mystery of the MPT, they did make a few surprising discoveries. For example, an interglacial period, or era when ice was in retreat, known as MIS 31 is widely recognized as having been abnormally warm—and yet the records at Lake El’gygytgyn show only moderate warmth. Instead, three other interglacial periods, MIS 21, 27 and 29 were as warm or warmer. Finally, the team’s research shows a long-term drying trend throughout the MPT.
“This couldn’t have been done without Lindberg’s enthusiasm,” says Castañeda. “I’ve always had lots of undergrads in my lab, and I love working with them. Kurt took off with this project, and did a wonderful job.”
More information: Kurt R. Lindberg et al, Biomarker Proxy Records of Arctic Climate Change During the Mid-Pleistocene Transition from Lake El’gygytgyn (Far East Russia), Climate of the Past (2021). DOI: 10.5194/cp-2021-66
Journal information: Climate of the PastProvided by University of Massachusetts Amherst
On January 15, the volcano Hunga Tonga-Hunga Ha’apai devastated the nation of Tonga. The eruption triggered tsunamis as far afield as the Caribbean and generated atmospheric waves that traveled around the globe several times. Meanwhile, the volcano’s plume shot gas and ash through the stratosphere into the lower mesosphere.
Just two months after the eruption, geologists have put together a preliminary account of how it unfolded. UC Santa Barbara’s Melissa Scruggs and emeritus Professor Frank Spera were part of an international team of researchers that published the first holistic account of the event in the journal Earthquake Research Advances. The authors think that an eruption the day before may have primed the volcano for the violent explosion by sinking its main vent below the ocean’s surface. This enabled molten rock to vaporize a large volume of seawater, intensifying the volcanic eruption the very next day.
“This is definitely, without a doubt, the largest eruption since Mt. Pinatubo in 1991,” said corresponding author Scruggs, who studies magma mixing and eruption triggering mechanisms, and recently completed her doctorate at UC Santa Barbara. She compared January’s event to the 1883 eruption of Krakatoa, which was heard 3,000 miles away.
Hunga Tonga-Hunga Ha’apai (HTHH) is a stratovolcano: a large, cone-shaped mountain that is prone to periodic violent eruptions, but which usually experiences milder activity. It’s one of many along the Tofua Volcanic Arc, a line of volcanoes fed by magma from the Pacific Plate diving beneath the Indo-Australian Plate. Heat and pressure cook the rocks of the descending plate, driving out water and other volatiles. That same water decreases the melting temperature of the rock above, leading to a chain of volcanoes about 100 kilometers from the plate boundary.
A submerged danger
The islands of Hunga Tonga and Hunga Ha’apai—after which the volcano is named—are merely the two highest points along the rim of the caldera, or central crater. Or they were, until the eruption blew most of the islands sky high.
Scruggs first heard about the eruption as she scrolled through her Twitter feed while getting ready for bed. “I saw a GIF of the satellite eruption, and my heart just stopped,” she said, pausing to find her words. She immediately knew that the event would cause massive devastation. “The scariest part was that the entire country was cut off, and we didn’t know what had happened.”
She was already messaging other volcanologists as the events unfolded, trying to understand the images that satellites had so clearly captured. “We really just set out to try to understand what happened,” Scruggs said. “So, we gathered all the information that we could, anything that was available within the first few weeks.” The authors drew on whatever resources they could find to quickly characterize this eruption, including publicly available data, videos and even tweets.
Using a variety of data sets, the team calculated that the January 15 event began at 5:02 p.m. local time (0402 ±1 UTC). The U.S. Geological Survey recorded a seismic event around 13 minutes later at the vent location. The first two hours of the eruption were particularly violent, with activity fading after about 12 hours.
Top: Hunga Tonga and Hunga Ha’apai were separate islands that grew together over the course of seven years. Bottom: The eruption on Jan. 14, 2022 sunk the main vent below sea level, enabling the eruption the following day to all but obliterate the islands. Dates: Nov. 16, 2021; Jan. 7, 2022; Jan. 15, 2022; and Jan. 18, 2022. Credit: PLANET LABS PBC
But eruption activity had actually started all the way back on December 20, 2021. And before that, the volcano had erupted in 2009 and again in 2014 and 2015. Scruggs believes these earlier episodes are key to understanding the violence behind HTHH’s recent eruption, perhaps related to changes in the magma plumbing system at depth or the chemistry of the magma over time.
Hunga Tonga and Hunga Ha’apai had been separate islands until they were united by eruptions from the volcano’s main vent, which created a land bridge. “This island was just born in 2015,” said Scruggs. “And now it’s gone. Were it not for the satellite era, we would not have even known it ever existed.”
On January 14, 2022 an explosion from the main vent razed this connection, sinking the vent beneath the ocean’s surface. “Had that land bridge not been taken out, the January 15 eruption might have behaved just like the day before because it would not have had that excess seawater,” Scruggs remarked.
A staggering explosion
Same volcano, one day’s difference: On Friday the vent was above the water, and by Saturday it was below. “That made all of the difference in the world,” Scruggs said.
The team believes that the seawater played a large part in the violence and force behind the Jan. 15 eruption. Much like a bottle rocket, an eruption of this scale takes the right ratio of water and gas to provide the force to send it skyward.
And it took off like a rocket, too. “It went halfway to space,” Scruggs exclaimed. The ash plume shot 58 kilometers into the atmosphere, past the stratosphere and into the lower mesosphere. This is more than twice the height reached by the plume from Mt. Saint Helens in 1980. It was the tallest volcanic plume ever recorded.
A truly staggering amount of lightning also accompanied the eruption. The authors suspect that vaporizing seawater caused the lava to fragment into microscopic ash particles, which were joined by tiny ice crystals once the steam froze in the upper atmosphere. The motion, temperature change and size of the particles generated incredible amounts of static charge separation that flashed above the eruption. For the first two hours of the eruption, about 80% of all lightning strikes on Earth split the sky above Hunga Tonga-Hunga Ha’apai.
The authors estimate around 1.9 km3 of material, weighing 2,900 teragrams, erupted from HTHH on Jan. 15. “But the volume of the eruption was not the big deal,” said Spera, a co-author on the paper and Scruggs’ doctoral advisor. “What was special is how the energy of the eruption coupled to the atmosphere and oceans: A lot of the energy went into moving air and water on a global scale.”
The shockwave traveling through the ocean triggered tsunamis throughout the Pacific, and beyond. What’s more, the wave arrived faster than tsunami warning models predicted because the models aren’t calibrated for volcanic eruptions—they’re based on equations that describe tsunamis generated by earthquakes.
A second tsunami followed the atmospheric pressure wave. This shockwave even triggered a meteo-tsunami in the Caribbean, which has no direct connection to the South Pacific. Scruggs called it unprecedented: “Basically the whole ocean just kind of sloshed around for five days after the eruption,” she added.
Plenty of work to do
Scientists are still piecing together what happened at the volcano, so they have yet to develop a complete understanding of the tsunami wave. However, it’s an important task needed to update tsunami travel forecast systems so they account for this type of mechanism. Otherwise, warnings could be incorrect the next time a volcano like HTHH erupts, potentially costing more lives.
Indeed, the event highlights the danger posed by unmonitored submarine volcanoes. Despite the devastation, the people of Tonga were relatively well prepared for the Jan. 15 eruption. The government had issued warnings based on the previous day’s activity, and the nation had plans in place for eruptions and tsunamis.
HTHH has experienced similarly violent eruptions in the past. A recent paper by researchers at the University of Otago, New Zealand revealed that a large eruption destroyed the caldera at the summit of the undersea volcano about 1,000 years ago. And similar volcanoes could well erupt in the same manner. Consider Kick ’em Jenny, another submarine volcano whose main vent is a mere 150 meters underwater. It’s located just 8 km north of the island of Grenada. “Imagine if something like the Tonga eruption happened in the Caribbean,” Scruggs said.
The researchers worked quickly with only publicly available data. They plan to revisit all their findings as more information and samples become available and as more researchers publish their own findings on this groundbreaking eruption. Their primary goal was to provide a point of departure for future work on the topic.
Scruggs is particularly keen on learning about the ash collected from this eruption. Volcanic rock provides a wealth of information to a trained geologist. Examining the material could shed light on the type of magma that erupted, how much of it there was and perhaps even how much seawater was involved in the eruption.
“There’s so many questions that have been raised,” said Scruggs. “Things we didn’t even think were possible have now been recorded.”
The UC Santa Barbara researchers will lead a special invited session on the Hunga Tonga-Hunga Ha’apai eruption at the Geological Society of America’s 2022 annual meeting in Denver this October. “It will be exciting to see what scores of other earth scientists can discover about this unique volcano,” Spera said. “We are just at the beginning.”
More information: David A. Yuen et al, Under the Surface: Pressure-Induced Planetary-Scale Waves, Volcanic Lightning, and Gaseous Clouds Caused by the Submarine Eruption of Hunga Tonga-Hunga Ha’apai Volcano Provide an Excellent Research Opportunity, Earthquake Research Advances (2022). DOI: 10.1016/j.eqrea.2022.100134
