This salt battery harvests osmotic energy where the river meets the sea

Estuaries -- where freshwater rivers meet the salty sea -- are great locations for birdwatching and kayaking. In these areas, waters containing different salt concentrations mix and may be sources of sustainable, "blue" osmotic energy. Researchers in ACS Energy Letters report creating a semipermeable membrane that harvests osmotic energy from salt gradients and converts it to electricity. The new design had an output power density more than two times higher than commercial membranes in lab demonstrations.

Osmotic energy can be generated anywhere salt gradients are found, but the available technologies to capture this renewable energy have room for improvement. One method uses an array of reverse electrodialysis (RED) membranes that act as a sort of "salt battery," generating electricity from pressure differences caused by the salt gradient. To even out that gradient, positively charged ions from seawater, such as sodium, flow through the system to the freshwater, increasing the pressure on the membrane. To further increase its harvesting power, the membrane also needs to keep a low internal electrical resistance by allowing electrons to easily flow in the opposite direction of the ions. Previous research suggests that improving both the flow of ions across the RED membrane and the efficiency of electron transport would likely increase the amount of electricity captured from osmotic energy. So, Dongdong Ye, Xingzhen Qin and colleagues designed a semipermeable membrane from environmentally friendly materials that would theoretically minimize internal resistance and maximize output power.

The researchers' RED membrane prototype contained separate (i.e., decoupled) channels for ion transport and electron transport. They created this by sandwiching a negatively charged cellulose hydrogel (for ion transport) between layers of an organic, electrically conductive polymer called polyaniline (for electron transport). Initial tests confirmed their theory that decoupled transport channels resulted in higher ion conductivity and lower resistivity compared to homogenous membranes made from the same materials. In a water tank that simulated an estuary environment, their prototype achieved an output power density 2.34 times higher than a commercial RED membrane and maintained performance during 16 days of non-stop operation, demonstrating its long-term, stable performance underwater. In a final test, the team created a salt battery array from 20 of their RED membranes and generated enough electricity to individually power a calculator, LED light and stopwatch.

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Viruses that can help 'dial up' carbon capture in the sea

Armed with a catalog of hundreds of thousands of DNA and RNA virus species in the world's oceans, scientists are now zeroing in on the viruses most likely to combat climate change by helping trap carbon dioxide in seawater or, using similar techniques, different viruses that may prevent methane's escape from thawing Arctic soil.

By combining genomic sequencing data with artificial intelligence analysis, researchers have identified ocean-based viruses and assessed their genomes to find that they "steal" genes from other microbes or cells that process carbon in the sea. Mapping microbial metabolism genes, including those for underwater carbon metabolism, revealed 340 known metabolic pathways throughout the global oceans. Of these, 128 were also found in the genomes of ocean viruses.

"I was shocked that the number was that high," said Matthew Sullivan, professor of microbiology and director of the Center of Microbiome Science at The Ohio State University.

Having mined this massive trove of data via advances in computation, the team has now revealed which viruses have a role in carbon metabolism and are using this information in newly developed community metabolic models to help predict how using viruses to engineer the ocean microbiome toward better carbon capture would look.

"The modeling is about how viruses may dial up or dial down microbial activity in the system," Sullivan said. "Community metabolic modeling is telling me the dream data point: which viruses are targeting the most important metabolic pathways, and that matters because it means they're good levers to pull on."

Sullivan presented the research today (Feb. 17, 2024) at the annual meeting of the American Association for the Advancement of Science in Denver.

Sullivan was the virus coordinator for the Tara Oceans Consortium, a three-year global study of the impact of climate change on the world's oceans and the source of 35,000 water samples containing the microbial bounty. His lab focuses on phages, viruses that infect bacteria, and their potential to be scaled up in an engineering framework to manipulate marine microbes into converting carbon into the heaviest organic form that will sink to the ocean floor.

"Oceans soak up carbon, and that buffers us against climate change. CO2 is absorbed as a gas, and its conversion into organic carbon is dictated by microbes," Sullivan said. "What we're seeing now is that viruses target the most important reactions in these microbial community metabolisms. This means we can start investigating which viruses could be used to convert carbon toward the kind we want.

"In other words, can we strengthen this massive ocean buffer to be a carbon sink to buy time against climate change, as opposed to that carbon being released back into the atmosphere to accelerate it?"

In 2016, the Tara team determined that carbon sinking in the ocean was related to the presence of viruses. It is thought that viruses help sink carbon when virus-infected carbon-processing cells cluster into larger, sticky aggregates that drop to the ocean floor. The researchers developed AI-based analytics to identify from thousands of viruses which few are "VIP" viruses to culture in the lab and work with as model systems for ocean geoengineering.

This new community metabolic modeling, developed by collaborator Professor Damien Eveillard of the Tara Oceans Consortium, helps them understand what unintended consequences might be of such an approach. Sullivan's lab is taking these oceanic lessons learned and applying them to using viruses to engineer microbiomes in human settings to aid recovery from spinal cord injury, improve outcomes for infants born to mothers with HIV, combat infection in burn wounds, and more.

"The conversation we're having is, 'How much of this is transferable?'" said Sullivan, also a professor of civil, environmental and geodetic engineering. "The overall goal is engineering microbiomes toward what we think is something useful."

He also reported on early efforts to use phages as geoengineering tools in an entirely different ecosystem: the permafrost in northern Sweden, where microbes both change the climate and respond to climate change as the frozen soil thaws. Virginia Rich, associate professor of microbiology at Ohio State, is co-director of the National Science Foundation-funded EMERGE Biology Integration Institute based at Ohio State that organizes the microbiome science at the Sweden field site. Rich also co-led previous research that identified a lineage of single-cell organisms in the thawing permafrost soil as a significant producer of methane, a potent greenhouse gas.

Rich co-organized the AAAS session with Ruth Varner of the University of New Hampshire, who co-directs the EMERGE Institute, which is focusing on better understanding how microbiomes respond to permafrost thaw and the resulting climate interactions.

Sullivan's talk was titled "From ecosystems biology to managing microbiomes with viruses," and was presented at the session titled "Microbiome-Targeted Ecosystem Management: Small Players, Big Roles."

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Climate change shown to cause methane to be released from the deep ocean

New research has shown that fire-ice -- frozen methane which is trapped as a solid under our oceans -- is vulnerable to melting due to climate change and could be released into the sea.

An international team of researchers led by Newcastle University found that as frozen methane and ice melts, methane -- a potent greenhouse gas -- is released and moves from the deepest parts of the continental slope to the edge of the underwater shelf.

They even discovered a pocket which had moved 25 miles (40 kilometres).

Publishing in the journal Nature Geoscience, the researchers say this means that much more methane could potentially be vulnerable and released into the atmosphere as a result of climate warming.

Methane hydrate

Methane hydrate, also known as fire-ice, is an ice-like structure found buried in the ocean floor that contains methane.

Vast amounts of methane are stored as marine methane under oceans.

It thaws when the oceans warm, releasing methane into oceans and the atmosphere -- known as dissociated methane -- contributing to global warming.

The scientists used advanced three-dimensional seismic imaging techniques to examine the portion of the hydrate that dissociated during climatic warming off the coast of Mauritania in Northwest Africa.

They identified a specific case where dissociated methane migrated over 40 kilometres and was released through a field of underwater depressions, known as pockmarks, during past warm periods.

Lead author, Professor Richard Davies, Pro-Vice-Chancellor, Global and Sustainability, Newcastle University, said: "It was a Covid lockdown discovery, I revisited imaging of strata just under the modern seafloor offshore of Mauritania and pretty much stumbled over 23 pockmarks. Our work shows they formed because methane released from hydrate, from the deepest parts of the continental slope vented into the ocean. Scientists had previously thought this hydrate was not vulnerable to climatic warming, but we have shown that some of it is."

Researchers have previously studied how changes in bottom water temperature near continental margins can affect the release of methane from hydrates.

However, these studies mainly focused on areas where only a small portion of global methane hydrates are located.

This is one of only a small number that investigate the release of methane from the base of the hydrate stability zone, which is deeper underwater.

The results show that methane released from the hydrate stability zone travelled a significant distance towards land.

Professor Dr Christian Berndt, Head of the Research Unit Marine Geodynamics, GEOMAR, in Kiel, Germany, added:

"This is an important discovery. So far, research efforts focused on the shallowest parts of the hydrate stability zone, because we thought that only this portion is sensitive to climate variations.

"The new data clearly show that far larger volumes of methane may be liberated from marine hydrates and we really have to get to the bottom of this to understand better the role of hydrates in the climate system."

Methane is the second most abundant anthropogenic greenhouse gas after carbon dioxide (CO2). Figures from the United States Environmental Protection Agency show that methane accounts for about 16% of global greenhouse gas emissions.

The study results can play a key role in helping to predict and address the impact of methane on our changing climate.

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Scientists identify 2022 sea urchin killer

The search for the 2022 killer that decimated the long-spined sea urchin population in the Caribbean and along Florida's east coast is over. A team of researchers organized by Mya Breitbart, Distinguished University Professor at the University of South Florida's College of Marine Science, identified a single-celled organism called a ciliate as the cause of a massive die-off event to a marine animal vital to coral reef health.

Their findings were reported in Science Advances.

"We're beyond thrilled to get to the bottom of the 2022 mystery and a bit stunned we did it so quickly," said Breitbart, senior author on the Science Advances study and an expert in marine genomics. "We had a great team in place and the tools needed to do the ocean science equivalent of a forensic investigation."

Ciliates are microscopic organisms covered in hair-like structures called cilia that help them move and eat. They are found almost anywhere there is water and most are not disease-causing agents. However, this specific species of ciliate -- called a scuticociliate -- has been implicated in die-offs of other marine species, such as sharks, in the past.

Examining urchins collected from 23 sites in the Caribbean, the research team used a series of techniques to confirm the source of the die-off event.

After identifying the ciliate in every affected urchin specimen using genomic techniques, the team grew ciliates in the lab and performed infection experiments at the USF College of Marine Science. When the pathogen was introduced to otherwise healthy urchins in an aquarium tank, the urchins died within a few days -- replicating what was taking place in the ocean and confirming the ciliate as the disease source.

"We're excited to share this information with everyone, from reef managers to additional scientists so we can explore it further and try to stop its spread," Breitbart said.

The long-spined sea urchins inhabit shallow tropical waters and feed on algae that would otherwise destroy a reef. They began to lose their spines within days of contracting an unknown disease and died in droves starting in January 2022.

A similar die-off event took place in the early 1980s, which wiped out 98 percent of the long-spined sea urchin population. The culprit of that die-off remains a mystery.

Breitbart first got the call about the unfolding die-off at the end of March 2022. She immediately assembled a team consisting of Ian Hewson, lead author on the publication and a marine ecologist at Cornell University; Christina Kellogg, a microbiologist from the U.S. Geological Survey in St. Petersburg, Fla. who has worked extensively on coral reef diseases; and USF graduate student Isabella Ritchie.

"At the time, we didn't know if this die-off was caused by pollution, stress, something else -- we just didn't know," said Hewson, an expert in diseases that cause mass die-offs of sea stars, who flew from New York to the Caribbean Islands to observe the situation.

Even with the source of the mysterious die-off uncovered, questions still remain. For example:
 

• Is this ciliate new to the area, or was it there prior to the die-off?
• If it has been there, what environmental conditions favored its growth and why did it infect the urchins?
• Can it affect other species of urchins?

"One theory we have is that the ciliate grew well under high-productivity conditions that were observed in the Caribbean when the die-off first started," Kellogg said. "We're also curious about the fact that there is some overlap in some geographic areas where this die-off occurred and where corals are declining from stony coral tissue loss disease."

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Shedding light on photosynthesis at sea

Plants that live on land, such as spinach, grow by using sunlight to perform photosynthesis. How, then, do algae photosynthesize in the deep sea, an environment where only a little light reaches them?

Land plants mainly absorb red and blue light from the sun and use it for photosynthesis. However, only weak blue-green light reaches the ocean floor. Therefore, macroalgae growing in the ocean have developed a protein, a so-called photosynthetic antenna, that efficiently utilizes this blue-green light. The photosynthetic antenna of marine macroalgae is very similar to that of land plants but differs in the structure of the pigments bound to it. Land plants have two types of pigments bound to their photosynthetic antennae, namely carotenoids and chlorophylls. In the marine green macroalga Codium fragile, the major carotenoids are substituted with siphonaxanthin while some chlorophyll a molecules are replaced by chlorophyll b molecules. Siphonaxanthin and chlorophyll b are known to contribute to increased absorption of green light and blue-green light, respectively, but the mechanism has not yet been fully understood.

Responding to this gap, a research team led by Associate Professor Ritsuko Fujii, from the Research Center for Artificial Photosynthesis (ReCAP) at Osaka Metropolitan University, and graduate student Soichiro Seki, from the Graduate School of Science at Osaka City University, used cryogenic electron microscopy to investigate the structures and binding environments of pigments bound to the photosynthetic antenna of C. fragile. The results allow for the elucidation of the molecular mechanism by which blue-green light -- the only light available in deep seawater -- is efficiently utilized for photosynthesis. Their findings were published in BBA Advances on November 11, 2022.

High-resolution analysis by cryogenic electron microscopy showed that siphonaxanthin in C. fragile is greatly distorted and forms hydrogen bonds with the surrounding protein at two locations. This structural feature is deemed a key factor in siphonaxanthin's ability to absorb green light. Additionally, the researchers successfully detected the difference between chlorophyll a and chlorophyll b, and they clarified several chlorophyll molecule substitution sites. When the substitution occurs, the adjacent region of chlorophyll b clusters becomes wider, enabling better absorption of blue-green light. In other words, the team was able to obtain information on the pigment coordinates, contributing to a better understanding of the mechanism of more efficient photosynthesis.

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Florida mints radiated as peninsula sank and resurfaced during ice ages

During the ice ages of the Pleistocene, the Florida peninsula regularly grew to twice its current size as glaciers expanded near the planet's poles, only to be reduced to a series of islands as melting ice returned to the sea during warm periods. All told, glaciers advanced and retreated 17 times, and according to a new study, the resulting environmental instability may have contributed to the incredible plant diversity found in Florida today.

Researchers from the Florida Museum of Natural History came to this conclusion while studying scrub mints, a unique group of plants endemic to the southeastern U.S. that radiated during the ice ages. Cyclically marooned on isolated islands as seas rose and fell, mint populations became genetically isolated and diverged over time, generating multiple new species.

Despite their long winning streak, scrub mints have recently been hit head on with the threat of extinction due to human-mediated habitat destruction and impending climate change. Of the 13 species endemic to Florida, eight are listed as either state or federally endangered.

"The most remarkable thing about this group is how rare they are," said lead author Andre Naranjo, who completed the study while working as a doctoral student in the University of Florida's department of biology. "One species, Conradina etonia, only grows within a 30-square mile area, and if you were to pave over that, that'd be it. The species would be gone."

Other scrub mints share a similar pattern. Lakela's mint (Dicerandra immaculata) has been reduced to just a single population, most of which is located on privately owned lands. Scrub balm (Dicerandra frutescens) is restricted to Highlands County, FL where it grows along an elevated ridge increasingly checkered by development. Further west, the Apalachicola rosemary (Conradina glabra) has been reduced to just ten known locations in a single region of the Florida panhandle.

The current plight of scrub mints and other groups like them offers only a partial explanation of why they have been pushed so far to the sidelines. To get the full picture, says Naranjo, you have to take a much longer view of how species have fared over time, one that covers several million years of their natural history.

Naranjo wanted to know where scrub mints came from, when they originated and how they ended up with their current distributions. Building on his previous work, Naranjo used a new method for reconstructing historical environments developed by co-author Ryan Folk, a former postdoctoral associate at the Florida Museum of Natural History who joined the faculty at Mississippi State University in 2019.

By inputting information about the plants' current habitats, such as temperature, precipitation and soil type, Naranjo could then trace their geographic history. The result was a detailed map that pinpointed the most suitable environments for each of the 22 species, half of which are endemic to Florida.

Nearly four million years ago, a scrub mint species growing in the Apalachicola River Basin of Florida shed a fine layer of seeds on the sandy soil below. Each no larger than a coarse grain of sand, the seeds don't often travel far, which researchers suspect is a major cause of their rarity. But they're also equipped with an opportunistic deployment mechanism that occasionally enables long-distance transport.

Scrub mint seed coats are perforated with glands that exude small amounts of viscous oil, Naranjo said. "When it rains really hard, the water forms little streams that drain the sand away from the scrub habitats. If the seeds land in these streams, their mucilaginous coating reduces friction, which helps carry them a few meters away from the parent plant."

Whether all at once or in stages, a seed or seeds from the original population in Apalachicola somehow traveled potentially hundreds of miles east, ultimately leading to the establishment of mints in the Altamaha region of Georgia. Seeds from these newly established populations may have floated down rivers and streams into peninsular Florida, where they washed ashore on the ancient Lake Wales and Atlantic Coastal Ridges.

Throughout the ice ages, the population that remained in the west radiated into the false rosemaries (genus Conradina), while those in the east gave rise to the genus Dicerandra. The groups occasionally crisscrossed in a complex migration pattern that resulted in distant relatives sharing the same environment, a family reunion on a millennial timescale.

Scrub mints are merely one example of unique Florida plants that originated in the peninsula that are now imperiled due to habitat destruction, fire suppression and competition with invasive species. The Lake Wales Ridge, where many scrub mints evolved and which functioned as an ark for plants and animals retreating from rising seas, has lost more than 85% of its natural habitat to urbanization and agriculture.

Florida is also part of the North American Coastal Plain, which was listed in 2015 as one of Earth's 36 biodiversity hotspots, defined as a region harboring at least 1,500 endemic species and which has lost 70% or more of its original vegetation.

"We need to start thinking about conservation in a broader context than just individual species," Naranjo said, emphasizing the focus instead should be shifted toward preserving entire regions and environments. "Our hope is that this research can be used as a rubric to study other endemic plants and further refine a comprehensive conservation approach for those areas most at risk of being developed."

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Tiniest ever ancient seawater pockets revealed

Trapped for millennia, the tiniest liquid remnants of an ancient inland sea have now been revealed. The surprising discovery of seawater sealed in what is now North America for 390 million years opens up a new avenue for understanding how oceans change and adapt with the changing climate. The method may also be useful in understanding how hydrogen can be safely stored underground and transported for use as a carbon-free fuel source.

"We discovered we can actually dig out information from these mineral features that could help inform geologic studies, such as the seawater chemistry from ancient times," said Sandra Taylor, first author of the study and a scientist at the Department of Energy's Pacific Northwest National Laboratory.

Taylor worked with PNNL colleagues Daniel Perea, John Cliff, and Libor Kovarik to perform the analyses in collaboration with geochemists Daniel Gregory of the University of Toronto and Timothy Lyons of the University of California, Riverside. The research team reported their discovery in the December 2022 issue of Earth and Planetary Science Letters.

Ancient seas; modern tools

Many types of minerals and gems contain small pockets of trapped liquid. Indeed, some gemstones are prized for their light-catching bubbles of liquid trapped within. What's different in this study is that scientists were able to reveal what was inside the tiniest water pockets, using advanced microscopy and chemical analyses.

The findings of the study confirmed that the water trapped inside the rock fit the chemistry profile of the ancient inland saltwater sea that once occupied upstate New York, where the rock originated. During the Middle Devonian period, this inland sea stretched from present day Michigan to Ontario, Canada. It harbored a coral reef to rival Australia's Great Barrier Reef. Sea scorpions the size of a pickup truck patrolled waters that harbored now-extinct creatures like trilobites, and the earliest examples of horseshoe crabs.

But eventually the climate changed, and along with that change, most of the creatures and the sea itself disappeared, leaving behind only fossil remains embedded in sediments that eventually became the pyrite rock sample used in the current experiment.

Clues to an ancient climate and to climate change

Scientists use rock samples as evidence to piece together how the climate has changed over the long span of geologic time.

"We use mineral deposits to estimate the temperature of the ancient oceans," said Gregory, a geologist at the University of Toronto, and one of the study leaders. But there are relatively few useful examples in the geological record.

"Salt deposits from trapped seawater [halite] are relatively rare in the rock record, so there are millions of years missing in the records and what we currently know is based on a few localities where there is halite found," Gregory said. By contrast, pyrite is found everywhere. "Sampling with this technique could open up millions of years of the geologic record and lead to new understanding of changing climate."

Seawater surprise

The research team was trying to understand another environmental issue -- toxic arsenic leaching from rock -- when they noticed the tiny defects. Scientists describe the appearance of these particular pyrite minerals as framboids -- derived from the French word for raspberry -- because they look like clusters of raspberry segments under the microscope.

"We looked at these samples through the electron microscope first, and we saw these kind of mini bubbles or mini features within the framboid and wondered what they were," Taylor said.

Using the precise and sensitive detection techniques of atom probe tomography and mass spectrometry -- which can detect minuscule amounts of elements or impurities in minerals -- the team worked out that the bubbles indeed contained water and their salt chemistry matched that of ancient seas.

From ancient sea to modern energy storage

These types of studies also have the potential to provide interesting insights into how to safely store hydrogen or other gases underground.

"Hydrogen is being explored as a low-carbon fuel source for various energy applications. This requires being able to safely retrieve and store large-amounts of hydrogen in underground geologic reservoirs. So it's important to understand how hydrogen interacts with rocks," said Taylor. "Atom probe tomography is one of the few techniques where you can not only measure atoms of hydrogen, but you can actually see where it goes in the mineral. This study suggests that tiny defects in minerals might be potential traps for hydrogen. So by using this technique we could figure out what's going on at the atomic level, which would then help in evaluating and optimizing strategies for hydrogen storage in the subsurface."

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Early evolution of sea urchins

New insight on the origins and early evolution of echinoids, a group that includes the sea urchins, the sand dollars, and their relatives, has been published today in the journal eLife.

The study suggests that modern echinoids emerged approximately 300 million years ago, survived the Permo-Triassic mass extinction event -- the most severe biodiversity crisis in Earth's history -- and rapidly diversified in its aftermath. These findings help address a gap in knowledge caused by the relative lack of fossil evidence for this early diversification.

There are more than 1,000 living species of echinoids, including sea urchins, heart urchins, sand dollars and sea biscuits, which live across different ocean environments ranging from shallow waters to abysses. Throughout history, the hard spine-covered skeletons of these creatures have left an impressive number of fossils. However, despite this remarkable fossil record, their emergence is documented by few fossil specimens with unclear affinities to living groups, making their early history uncertain.

"There are still debates among scientists about when the ancestors of echinoids emerged and what role the mass extinction event that occurred between the Permian and Triassic periods may have played in their evolution," says first author Nicolás Mongiardino Koch, who completed the work while he was at Yale University, New Haven, Connecticut, US, and is now a postdoctoral fellow at Scripps Institution of Oceanography at UC San Diego, US.

"We set out to help resolve these debates by combining genomic and paleontological data to disentangle their evolutionary relationships. The extraordinary fossil record of echinoids and the ease with which these fossils can be incorporated in phylogenetic analyses make them an ideal system to explore their early evolution using this approach."

Mongiardino Koch and the team built upon available molecular resources with 18 novel genomic datasets, creating the largest existing molecular matrix for echinoids. Using this dataset, they were able to reconstruct the phylogenetic relationships and divergence times of the major lineages of living echinoids and place their diversification within broader evolutionary history. They did so by applying a 'molecular clock' technique to their dataset, whereby the rate at which mutations accumulated in the echinoid genomes is translated into geological time with the use of fossil evidence, allowing researchers to determine when different lineages first diversified.

Their analyses suggest that the ancestors of modern echinoids likely emerged during the Early Permian, and rapidly diversified during the Triassic period in the aftermath of a mass extinction event, even though this evolutionary radiation does not seem to have been captured by the fossil record.

Additionally, the results suggest that sand dollars and sea biscuits likely emerged much earlier than thought, during the Cretaceous period about 40 to 50 million years before the first documented fossils of these creatures. The authors say this result is remarkable, as the tough skeleton of the sand dollars, their buried lifestyles, and their extremely distinct morphologies imply that their fossil record should faithfully reflect their true evolutionary history.

The team also developed a multivariate statistical approach called a 'chronospace' to help them visualise and assess the robustness of their evolutionary timeline to different choices in their analyses. They found that different implementations of the molecular clock model had the strongest impact on divergence times, while other decisions showed minimal effects.

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How inland and coastal waterways influence climate

"Streams to the river, river to the sea." If only it were that simple.

Most global carbon-budgeting efforts assume a linear flow of water from the land to the sea, which ignores the complex interplay between streams, rivers, lakes, groundwater, estuaries, mangroves and more. A study co-led by climate scientist Laure Resplandy, an assistant professor of geosciences and the High Meadows Environmental Institute (HMEI) at Princeton University, details how carbon is stored and transported through the intricacy of inland and coastal waterways. Published in the current issue of the journal Nature, the work has significant implications for enforcing the carbon calculations that are part of international climate accords.

Terrestrial and marine ecosystems have a powerful influence on climate by regulating the level of atmospheric carbon dioxide (CO2). These ecosystems, however, are often viewed as disconnected from each other, which ignores the transfer of carbon from land to the open ocean through a complex network of water bodies -- the continuum of streams, rivers, estuaries and other bodies carrying water from land to the sea.

In a detailed analysis, the team of researchers from Belgium, the United States and France discovered that this land-to-ocean aquatic continuum (LOAC) carries a substantial amount of carbon of anthropogenic (e.g., fossil-fuel) origin. Thus, the carbon removed from the atmosphere by terrestrial ecosystems is not all stored locally, as is commonly assumed, which has implications for global agreements that require countries to report their carbon inventories. The researchers also found that the land-to-ocean carbon transfer of natural origin was larger than previously thought, with far-reaching implications for the assessment of the anthropogenic CO2 uptake by the ocean and the land.

"The complexity of the LOAC, which includes rivers, groundwater, lakes, reservoirs, estuaries, tidal marshes, mangroves, seagrasses, and waters above continental shelves, has made it challenging to assess its influence on the global carbon cycle," said Pierre Regnier, a professor at the University of Brussels who co-led the study with Resplandy.

Because of that complexity, important global carbon-budgeting efforts, such as those of the U.N. Intergovernmental Panel on Climate Change and the Global Carbon Project, typically assume a direct "pipeline" transfer of carbon from river mouths to the open ocean. Another common assumption is that all the transported carbon is natural, neglecting the impacts of human perturbations on this aquatic continuum, such as damming and the decimation of coastal vegetation.

In this study, the researchers synthesized more than 100 individual studies of the various components of the continuum. From this synthesis, LOAC carbon budgets were developed for two time periods: the pre-industrial period and the present day. Their results confirm the well-known pre-industrial carbon "loop" in which carbon is taken up from the atmosphere by terrestrial ecosystems, transferred by rivers to the ocean, and then outgassed back to the atmosphere.

"We find the amount of carbon carried by this natural land-to-ocean loop, 0.65 billion tons per year, is roughly 50% greater than previously thought," Resplandy said.

Furthermore, this loop is comprised of two smaller loops, one that transfers carbon from terrestrial ecosystems to inland waters and another from coastal vegetation (so-called "blue carbon ecosystems") to the open ocean.

"A larger pre-industrial land-to-ocean carbon transport implies that the ocean uptake of anthropogenic CO2 previously inferred from observations was underestimated," Resplandy said.

"The flip side is that the land uptake of anthropogenic CO2 was overestimated," added Regnier.

The study demonstrates that anthropogenic carbon carried by rivers is either outgassed back to the atmosphere or eventually stored in aquatic sediments and the open ocean.

Philippe Ciais, a research director at the Laboratoire des Sciences du Climat et de l'Environnement and a co-author of the study explained: "This new view of the anthropogenic CO2 budget may have a silver lining because sediments and the ocean offer arguably more stable repositories than terrestrial biomass and soil carbon, which are vulnerable to droughts, fires and land-use change."

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How land birds cross the open ocean

Researchers at the Max Planck Institute of Animal Behavior and University of Konstanz in Germany have identified how large land birds fly nonstop for hundreds of kilometers over the open ocean—without taking a break for food or rest. Using GPS tracking technology, the team monitored the global migration of five species of large land birds that complete long sea crossings. They found that all birds exploited wind and uplift to reduce energy costs during flight—even adjusting their migratory routes to benefit from the best atmospheric conditions. This is the most wide-ranging study of sea-crossing behavior yet and reveals the important role of the atmosphere in facilitating migration over the open sea for many terrestrial birds.

Flying over the open sea can be dangerous for land birds. Unlike seabirds, land birds are not able to rest or feed on water, and so sea crossings must be conducted as nonstop flights. For centuries, bird-watchers assumed that large land birds only managed short sea crossings of less than 100 kilometers and completely avoided flying over the open ocean.

However, recent advances in GPS tracking technology have overturned that assumption. Data obtained by attaching small tracking devices on wild birds has shown that many land birds fly for hundreds or even thousands of kilometers over the open seas and oceans as a regular part of their migration.

But scientists are still unraveling how land birds are able to accomplish this. Flapping is an energetically costly activity, and trying to sustain nonstop flapping flight for hundreds of kilometers would not be possible for large, heavy land birds. Some studies have suggested that birds sustain such journeys using tailwind, a horizontal wind blowing in the bird’s direction of flight, which helps them save energy. Most recently, a study revealed that a single species—the osprey—used rising air thermals known as “uplift” to soar over the open sea.

Now, the new study has examined sea-crossing behavior of 65 birds across five species to gain the most wide-ranging insight yet into how land birds survive long flights over the open sea. The researchers analyzed 112 sea-crossing tracks, collected over nine years, with global atmospheric information to pinpoint the criteria that the birds use for selecting their migration routes over the open sea. A large international collaboration of scientists shared their tracking data to make this study possible.

The findings not only confirm the role of tailwind in facilitating sea-crossing behavior, but also reveal the widespread use of uplift for saving energy during these nonstop flights. Suitable uplift means less drag, making sea crossing less energetically demanding.

“Until recently, uplift was assumed to be weak or absent over the sea surface. We show that is not the case,” says first author Elham Nourani, a DAAD PRIME postdoctoral fellow at the Department of Biology at the University of Konstanz, who did the work when she was at the Max Planck Institute of Animal Behavior.

“Instead, we find that migratory birds adjust their flight routes to benefit from the best wind and uplift conditions when they fly over the sea. This helps them sustain flight for hundreds of kilometers,” says Nourani.

The oriental honey buzzard, for example, flies 700 kilometers over the East China Sea during its annual migration from Japan to southeast Asia. The roughly 18-hour nonstop sea crossing is conducted in autumn when the air movement conditions are optimal. “By making use of uplift, these birds can soar up to one kilometer above the sea surface,” says Nourani.

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Sharks use Earth's magnetic fields to guide them like a map

Sea turtles are known for relying on magnetic signatures to find their way across thousands of miles to the very beaches where they hatched. Now, researchers reporting in the journal Current Biology on May 6 have some of the first solid evidence that sharks also rely on magnetic fields for their long-distance forays across the sea.

"It had been unresolved how sharks managed to successfully navigate during migration to targeted locations," said Save Our Seas Foundation project leader Bryan Keller, also of Florida State University Coastal and Marine Laboratory. "This research supports the theory that they use the earth's magnetic field to help them find their way; it's nature's GPS."

Researchers had known that some species of sharks travel over long distances to reach very specific locations year after year. They also knew that sharks are sensitive to electromagnetic fields. As a result, scientists had long speculated that sharks were using magnetic fields to navigate. But the challenge was finding a way to test this in sharks.

"To be honest, I am surprised it worked," Keller said. "The reason this question has been withstanding for 50 years is because sharks are difficult to study."

Keller realized the needed studies would be easier to do in smaller sharks. They also needed a species known for returning each year to specific locations. He and his colleagues settled on bonnetheads (Sphyrna tiburo).

"The bonnethead returns to the same estuaries each year," Keller said. "This demonstrates that the sharks knows where 'home' is and can navigate back to it from a distant location."

The question then was whether bonnetheads managed those return trips by relying on a magnetic map. To find out, the researchers used magnetic displacement experiments to test 20 juvenile, wild-caught bonnetheads. In their studies, they exposed sharks to magnetic conditions representing locations hundreds of kilometers away from where the sharks were actually caught. Such studies allow for straightforward predictions about how the sharks should subsequently orient themselves if they were indeed relying on magnetic cues.

If sharks derive positional information from the geomagnetic field, the researchers predicted northward orientation in the southern magnetic field and southward orientation in the northern magnetic field, as the sharks attempted to compensate for their perceived displacement. They predicted no orientation preference when sharks were exposed to the magnetic field that matched their capture site. And, it turned out, the sharks acted as they'd predicted when exposed to fields within their natural range.

The researchers suggest that this ability to navigate based on magnetic fields may also contribute to the population structure of sharks. The findings in bonnetheads also likely help to explain impressive feats by other shark species. For instance, one great white shark was documented to migrate between South Africa and Australia, returning to the same exact location the following year.

"How cool is it that a shark can swim 20,000 kilometers round trip in a three-dimensional ocean and get back to the same site?" Keller asked. "It really is mind blowing. In a world where people use GPS to navigate almost everywhere, this ability is truly remarkable."

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Climate change responsible for record sea temperature levels

 Global warming is driving an unprecedented rise in sea temperatures including in the Mediterranean, according to a major new report published by the peer-reviewed Journal of Operational Oceanography.

Data from the European Union's (EU) Copernicus Marine Environment Monitoring Service (CMEMS) will increase concerns about the threat to the world's seas and oceans from climate change.

The Ocean State Report reveals an overall trend globally of surface warming based on evidence from 1993 to 2018, with the largest rise in the Arctic Ocean.

European seas experienced record high temperatures in 2018, a phenomenon which the researchers attribute to extreme weather conditions -- a marine heat wave lasting several months.

In the same year, a large mass of warm water occurred in the northeast Pacific Ocean, according to the report. This was similar to a marine heatwave -- dubbed 'the Blob' -- which was first detected in 2013 and had devastating effects on marine life.

Now the study authors are calling for improved monitoring to provide better data and knowledge. They argue this will help countries progress towards sustainable use of seas and oceans which are an essential source of food, energy and other resources.

Findings from the report confirm record rises in sea temperatures

"Changes to the ocean have impacted on these (ocean) ecosystem services and stretched them to unsustainable limits," says Karina von Schuckmann and Pierre-Yves Le Traon, the report's editors.

"More than ever a long term, comprehensive and systematic monitoring, assessment and reporting of the ocean is required. This is to ensure a sustainable science-based management of the ocean for societal benefit."

The Ocean State Report identifies other major strains on the world's seas and oceans from climate change including acidification caused by carbon dioxide uptake from the atmosphere, sea level rise, loss of oxygen and sea ice retreat.

Long-term evidence of global warming outlined in the report includes a decrease over 30 years of up to two days in the period of Baltic Sea ice cover and an acceleration in the global mean sea level rise.

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Coastal cities leave up to 75% of seafloor exposed to harmful light pollution

The global expansion of coastal cities could leave more than three quarters of their neighbouring seafloor exposed to potentially harmful levels of light pollution.

A study led by the University of Plymouth (UK) showed that under both cloudy and clear skies, quantities of light used in everyday street lighting permeated all areas of the water column.

This could pose a significant threat to coastal species, with recent research showing the presence of artificial skyglow can disrupt the lunar compass species use when covering long distances.

However, the current study found that the colour of the wavelengths shone at the surface had a marked difference on how much biologically important light pollution reached the seafloor.

Many of the white LEDs now being used to illuminate the world's towns and cities use a mixture of green, blue and red wavelengths to generate their brightness.

Green and blue wavelengths left up to 76% and 70% of the three-dimensional seafloor area exposed to light pollution respectively, while the presence of red light was less than 1%.

The research -- which also involved Bangor University, the University of Strathclyde and Plymouth Marine Laboratory -- is published in Scientific Reports, an online journal from the publishers of Nature.

It is the first study in the world to quantify the extent to which biologically important artificial light is prevalent on the seafloor and could, in turn, be having a detrimental effect on marine species.

Dr Thomas Davies, Lecturer in Marine Conservation at the University of Plymouth and the paper's lead author, said: "The areas exposed here are not trivial. Our results focused on a busy marine area and demonstrate the light from coastal urban centres is widespread across the sea surface, sub surface and seafloor of adjacent marine habitats. But Plymouth is still just one coastal city with a population of 240,000 people.

"Seventy-five per cent of the world's megacities are now located in coastal regions and coastal populations are projected to more than double by 2060. So unless we take action now it is clear that biologically important light pollution on the seafloor is likely to be globally widespread, increasing in intensity and extent, and putting marine habitats at risk."

The study focussed on Plymouth Sound and the Tamar Estuary which together form a busy waterway and are home to the largest naval port in Western Europe.

It was conducted over four nights in 2018, when there was little or no moonlight, and blue, green, and red artificial light was shone at the sea surface during both clear and cloudy conditions, and at low and high tide.

A combination of mapping and radiative transfer modelling tools were then used to measure exposure at the surface, beneath the surface, and at the seafloor.

The researchers are now calling for a more comprehensive review of the full impacts of coastal light pollution, to try and mitigate against the most harmful effects as coastal cities grow globally.

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Discovery of life in solid rock deep beneath sea may inspire new search for life on Mars

Newly discovered single-celled creatures living deep beneath the seafloor have given researchers clues about how they might find life on Mars. These bacteria were discovered living in tiny cracks inside volcanic rocks after researchers persisted over a decade of trial and error to find a new way to examine the rocks.

Researchers estimate that the rock cracks are home to a community of bacteria as dense as that of the human gut, about 10 billion bacterial cells per cubic centimeter (0.06 cubic inch). In contrast, the average density of bacteria living in mud sediment on the seafloor is estimated to be 100 cells per cubic centimeter.

"I am now almost over-expecting that I can find life on Mars. If not, it must be that life relies on some other process that Mars does not have, like plate tectonics," said Associate Professor Yohey Suzuki from the University of Tokyo, referring to the movement of land masses around Earth most notable for causing earthquakes. Suzuki is first author of the research paper announcing the discovery, published in Communications Biology.

Magic of clay minerals

"I thought it was a dream, seeing such rich microbial life in rocks," said Suzuki, recalling the first time he saw bacteria inside the undersea rock samples.

Undersea volcanoes spew out lava at approximately 1,200 degrees Celsius (2,200 degrees Fahrenheit), which eventually cracks as it cools down and becomes rock. The cracks are narrow, often less than 1 millimeter (0.04 inch) across. Over millions of years, those cracks fill up with clay minerals, the same clay used to make pottery. Somehow, bacteria find their way into those cracks and multiply.

"These cracks are a very friendly place for life. Clay minerals are like a magic material on Earth; if you can find clay minerals, you can almost always find microbes living in them," explained Suzuki.

The microbes identified in the cracks are aerobic bacteria, meaning they use a process similar to how human cells make energy, relying on oxygen and organic nutrients.

"Honestly, it was a very unexpected discovery. I was very lucky, because I almost gave up," said Suzuki.

Cruise for deep ocean samples

Suzuki and his colleagues discovered the bacteria in rock samples that he helped collect in late 2010 during the Integrated Ocean Drilling Program (IODP). IODP Expedition 329 took a team of researchers from the tropical island of Tahiti in the middle of the Pacific Ocean to Auckland, New Zealand. The research ship anchored above three locations along the route across the South Pacific Gyre and used a metal tube 5.7 kilometers long to reach the ocean floor. Then, a drill cut down 125 meters below the seafloor and pulled out core samples, each about 6.2 centimeters across. The first 75 meters beneath the seafloor were mud sediment and then researchers collected another 40 meters of solid rock.

Depending on the location, the rock samples were estimated to be 13.5 million, 33.5 million and 104 million years old. The collection sites were not near any hydrothermal vents or sub-seafloor water channels, so researchers are confident the bacteria arrived in the cracks independently rather than being forced in by a current. The rock core samples were also sterilized to prevent surface contamination using an artificial seawater wash and a quick burn, a process Suzuki compares to making aburi (flame-seared) sushi.

At that time, the standard way to find bacteria in rock samples was to chip away the outer layer of the rock, then grind the center of the rock into a powder and count cells out of that crushed rock.

"I was making loud noises with my hammer and chisel, breaking open rocks while everyone else was working quietly with their mud," he recalled.

How to slice a rock

Over the years, continuing to hope that bacteria might be present but unable to find any, Suzuki decided he needed a new way to look specifically at the cracks running through the rocks. He found inspiration in the way pathologists prepare ultrathin slices of body tissue samples to diagnose disease. Suzuki decided to coat the rocks in a special epoxy to support their natural shape so that they wouldn't crumble when he sliced off thin layers.

These thin sheets of solid rock were then washed with dye that stains DNA and placed under a microscope.

The bacteria appeared as glowing green spheres tightly packed into tunnels that glow orange, surrounded by black rock. That orange glow comes from clay mineral deposits, the "magic material" giving bacteria an attractive place to live.

Whole genome DNA analysis identified the different species of bacteria that lived in the cracks. Samples from different locations had similar, but not identical, species of bacteria. Rocks at different locations are different ages, which may affect what minerals have had time to accumulate and therefore what bacteria are most common in the cracks.

Suzuki and his colleagues speculate that the clay mineral-filled cracks concentrate the nutrients that the bacteria use as fuel. This might explain why the density of bacteria in the rock cracks is eight orders of magnitude greater than the density of bacteria living freely in mud sediment where seawater dilutes the nutrients.

From the ocean floor to Mars

The clay minerals filling cracks in deep ocean rocks are likely similar to the minerals that may be in rocks now on the surface of Mars.

"Minerals are like a fingerprint for what conditions were present when the clay formed. Neutral to slightly alkaline levels, low temperature, moderate salinity, iron-rich environment, basalt rock -- all of these conditions are shared between the deep ocean and the surface of Mars," said Suzuki.

Suzuki's research team is beginning a collaboration with NASA's Johnson Space Center to design a plan to examine rocks collected from the Martian surface by rovers. Ideas include keeping the samples locked in a titanium tube and using a CT (computed tomography) scanner, a type of 3D X-ray, to look for life inside clay mineral-filled cracks.

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How squid communicate in the dark

In the frigid waters 1,500 feet below the surface of the Pacific Ocean, hundreds of human-sized Humboldt squid feed on a patch of finger-length lantern fish. Zipping past each other, the predators move with exceptional precision, never colliding or competing for prey.

How do they establish such order in the near-darkness of the ocean's twilight zone?

The answer, according to researchers from Stanford University and the Monterey Bay Aquarium Research Institute (MBARI) may be visual communication. Like the illuminated words on an e-book reader, these researchers suggest that the squid's ability to subtly glow -- using light-producing organs in their muscles -- can create a backlight for shifting pigmentation patterns on their skin. The creatures may be using these changing patterns to signal one another.

The research is published March 23 in the journal Proceedings of the National Academy of Sciences.

"Many squid live in fairly shallow water and don't have these light-producing organs, so it's possible this is a key evolutionary innovation for being able to inhabit the open ocean," said Benjamin Burford, a graduate student in biology in the School of Humanities and Sciences at Stanford and lead author of the paper. "Maybe they need this ability to glow and display these pigmentation patterns to facilitate group behaviors in order to survive out there."

Seeing the deep sea

Humboldt squid behavior is nearly impossible to study in captivity, so researchers must meet them where they live. For this research, Bruce Robison of MBARI, who is senior author of the paper, captured footage of Humboldt squid off the coast of California using remotely operated vehicles (ROVs), or unmanned, robotic submarines.

While the ROVs could record the squid's skin patterning, the lights the cameras required were too bright to record their subtle glow, so the researchers couldn't test their backlighting hypothesis directly. Instead, they found supporting evidence for it in their anatomical studies of captured squid.

Using the ROV footage, the researchers analyzed how individual squid behaved when they were feeding versus when they were not. They also paid attention to how these behaviors changed depending on the number of other squid in the immediate area -- after all, people communicate differently if they are speaking with friends versus a large audience.

The footage confirmed that squid's pigmentation patterns do seem to relate to specific contexts. Some patterns were detailed enough to imply that the squid may be communicating precise messages -- such as "that fish over there is mine." There was also evidence that their behaviors could be broken down into distinct units that the squid recombine to form different messages, like letters in the alphabet. Still, the researchers emphasize that it is too early to conclude whether the squid communications constitute a human-like language.

"Right now, as we speak, there are probably squid signaling each other in the deep ocean," said Burford, who is affiliated with the Denny lab at Stanford's Hopkins Marine Station. "And who knows what kind of information they're saying and what kind of decisions they're making based on that information?"

Although these squid can see well in dim light, their vision is probably not especially sharp, so the researchers speculated that the light-producing organs help facilitate the squid's visual communications by boosting the contrast for their skin patterning. They investigated this hypothesis by mapping where these light organs are located in Humboldt squid and comparing that to where the most detailed skin patterns appear on the creatures.

They found that the areas where the illuminating organs were most densely packed -- such as a small area between the squid's eyes and the thin edge of their fins -- corresponded to those where the most intricate patterns occurred.

Familiar aliens

In the time since the squid were filmed, ROV technology has advanced enough that the team could directly view their backlighting hypothesis in action the next time the squid are observed in California. Burford would also like to create some sort of virtual squid that the team could project in front of real squid to see how they respond to the cyber-squid's patterns and movements.

The researchers are thrilled with what they have found so far but eager to do further research in the deep sea. Although studying the inhabitants of the deep sea where they live can be a frustratingly difficult endeavor, this research has the potential to inform a new understanmetimes think of squid as crazy lifeforms living in this alien world but we have a lot in common -- they live in groups, they're social, they talkding of how life functions.

"We so to one another," Burford said. "Researching their behavior and that of other residents of the deep sea is important for learning how life may exist in alien environments, but it also tells us more generally about the strategies used in extreme environments on our own planet."

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Sea level rise could reshape the United States, trigger migration inland

Water coming over road in Kemah, Texas during Hurricane Harvey

When Hurricane Harvey slammed into the Texas coast in 2017, displaced residents flocked inland, trying to rebuild their lives in the disaster's aftermath. Within decades, the same thing could happen at a much larger scale due to rising sea levels, says a new study led by USC Computer Science Assistant Professor Bistra Dilkina.

The study, published in PLOS ONE, Jan. 22, is the first to use machine learning to project migration patterns resulting from sea-level rise. The researchers found the impact of rising oceans will ripple across the country, beyond coastal areas at risk of flooding, as affected people move inland.

In the US alone, 13 million people could be forced to relocate due to rising sea levels by 2100. As a result, cities throughout the country will grapple with new populations. Effects could include more competition for jobs, increased housing prices, and more pressure on infrastructure networks.

"Sea level rise will affect every county in the US, including inland areas," said Dilkina, the study's corresponding author, a WiSE Gabilan Assistant Professor in computer science at USC and associate director of USC's Center for AI for Society.

"We hope this research will empower urban planners and local decision-makers to prepare to accept populations displaced by sea-level rise. Our findings indicate that everybody should care about sea-level rise, whether they live on the coast or not. This is a global impact issue."

According to the research team, most popular relocation choices will include land-locked cities such as Atlanta, Houston, Dallas, Denver and Las Vegas. The model also predicts suburban and rural areas in the Midwest will experience disproportionately large influx of people relative to their smaller local populations.

Predicting relocation areas

Sea-level rise is caused primarily by two factors related to global warming: added water from melting ice sheets and glaciers and the expansion of sea water as it warms. Within just a few decades, hundreds of thousands homes on the US coast will be flooded. In fact, by the end of the century, 6 feet of ocean-level rise would redraw the coastline of southern Florida, parts of North Carolina and Virginia and most of Boston and New Orleans.

To predict the trajectory of sea-level rise migration, the researchers took existing projections of rising sea levels and combined this with population projections. Based on migration patterns after Hurricane Katrina and Hurricane Rita, the team trained machine learning models -- a subset of artificial intelligence -- to predict where people would relocate.

"We talk about rising sea levels, but the effects go much further than those directly affected on the coasts," said Caleb Robinson, a visiting doctoral researcher from Georgia Tech advised by Dilkina and the study's first author. "We wanted to look not only at who would be displaced, but also where they would go." Dilkina and Robinson worked with co-author Juan Moreno Cruz, an economist and professor at the University of Waterloo.

As expected, the researchers found the greatest effects of sea-level rise migration will be felt by inland areas immediately adjacent to the coast, as well as urban areas in the southeast US. But their model also showed more incoming migrants to Houston and Dallas than previous studies, which flagged Austin as the top destination for climate migrants from the southeastern coast.

This result, notes the researchers, shows that population movement under climate change will not necessarily follow previously established patterns. In other words: it is not business as usual.

Sea-level rise could also reroute people relocating from unaffected areas. Counties surrounding Los Angeles, in particular, could see tens of thousands of migrants whose preferred coastal destinations are now flooded choosing alternative destinations.

The results of this study could help city planners and policymakers plan to expand critical infrastructure, from roads to medical services, to ensure the influx of people has a positive impact on local economies and social well-being.

"When migration occurs naturally, it is a great engine for economic activity and growth," said co-author Juan Moreno Cruz, an economist and professor at the University of Waterloo.

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Lightning 'superbolts' form over oceans from November to February

Lightning storm over ocean.

The lightning season in the Southeastern U.S. is almost finished for this year, but the peak season for the most powerful strokes of lightning won't begin until November, according to a newly published global survey of these rare events.

A University of Washington study maps the location and timing of "superbolts" -- bolts that release electrical energy of more than 1 million Joules, or a thousand times more energy than the average lightning bolt, in the very low frequency range in which lightning is most active. Results show that superbolts tend to hit the Earth in a fundamentally different pattern from regular lightning, for reasons that are not yet fully understood.

The study was published Sept. 9 in the Journal of Geophysical Research: Atmospheres, a journal of the American Geophysical Union.

"It's very unexpected and unusual where and when the very big strokes occur," said lead author Robert Holzworth, a UW professor of Earth and space sciences who has been tracking lightning for almost two decades.

Holzworth manages the World Wide Lightning Location Network, a UW-managed research consortium that operates about 100 lightning detection stations around the world, from Antarctica to northern Finland. By seeing precisely when lightning reaches three or more different stations, the network can compare the readings to determine a lightning bolt's size and location.

The network has operated since the early 2000s. For the new study, the researchers looked at 2 billion lightning strokes recorded between 2010 and 2018. Some 8,000 events -- four millionths of a percent, or one in 250,000 strokes -- were confirmed superbolts.

"Until the last couple of years, we didn't have enough data to do this kind of study," Holzworth said.

The authors compared their network's data against lightning observations from the Maryland-based company Earth Networks and from the New Zealand MetService.

The new paper shows that superbolts are most common in the Mediterranean Sea, the northeast Atlantic and over the Andes, with lesser hotspots east of Japan, in the tropical oceans and off the tip of South Africa. Unlike regular lightning, the superbolts tend to strike over water.

Explore a visualization of the data at https://public.tableau.com/profile/uw.news#!/vizhome/Superbolts/Dashboard1.

"Ninety percent of lightning strikes occur over land," Holzworth said. "But superbolts happen mostly over the water going right up to the coast. In fact, in the northeast Atlantic Ocean you can see Spain and England's coasts nicely outlined in the maps of superbolt distribution."

"The average stroke energy over water is greater than the average stroke energy over land -- we knew that," Holzworth said. "But that's for the typical energy levels. We were not expecting this dramatic difference."

The time of year for superbolts also doesn't follow the rules for typical lightning. Regular lightning hits in the summertime -- the three major so-called "lightning chimneys" for regular bolts coincide with summer thunderstorms over the Americas, sub-Saharan Africa and Southeast Asia. But superbolts, which are more common in the Northern Hemisphere, strike both hemispheres between the months of November and February.

The reason for the pattern is still mysterious. Some years have many more superbolts than others: late 2013 was an all-time high, and late 2014 was the next highest, with other years having far fewer events.

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Evidence for past high-level sea rise

An international team of scientists, studying evidence preserved in speleothems in a coastal cave, illustrate that more than three million years ago -- a time in which the Earth was two to three degrees Celsius warmer than the pre-industrial era -- sea level was as much as 16 meters higher than the present day. Their findings represent significant implications for understanding and predicting the pace of current-day sea level rise amid a warming climate.

The scientists, including Professor Yemane Asmerom and Sr. Research Scientist Victor Polyak from The University of New Mexico, the University of South Florida, Universitat de les Illes Balears and Columbia University, published their findings in today's edition of the journal Nature. The analysis of deposits from Artà Cave on the island of Mallorca in the western Mediterranean Sea produced sea levels that serve as a target for future studies of ice sheet stability, ice sheet model calibrations and projections of future sea level rise, the scientists said.

Sea level rises as a result of melting ice sheets, such as those that cover Greenland and Antarctica. However, how much and how fast sea level will rise during warming is a question scientists have worked to answer. Reconstructing ice sheet and sea-level changes during past periods when climate was naturally warmer than today, provides an Earth's scale laboratory experiment to study this question according to USF Ph.D. student Oana Dumitru, the lead author, who did much of her dating work at UNM under the guidance of Asmerom and Polyak.

"Constraining models for sea level rise due to increased warming critically depends on actual measurements of past sea level," said Polyak. "This study provides very robust measurements of sea level heights during the Pliocene."

"We can use knowledge gained from past warm periods to tune ice sheet models that are then used to predict future ice sheet response to current global warming," said USF Department of Geosciences Professor Bogdan Onac.

The project focused on cave deposits known as phreatic overgrowths on speleothems. The deposits form in coastal caves at the interface between brackish water and cave air each time the ancient caves were flooded by rising sea levels. In Artà Cave, which is located within 100 meters of the coast, the water table is -- and was in the past -- coincident with sea level, says Professor Joan J. Fornós of Universitat de les Illes Balears.

The scientists discovered, analyzed, and interpreted six of the geologic formations found at elevations of 22.5 to 32 meters above present sea level. Careful sampling and laboratory analyses of 70 samples resulted in ages ranging from 4.4 to 3.3 million years old BP (Before Present), indicating that the cave deposits formed during the Pliocene epoch. The ages were determined using uranium-lead radiometric dating in UNM's Radiogenic Isotope Laboratory.

"This was a unique convergence between an ideally-suited natural setting worked out by the team of cave scientists and the technical developments we have achieved over the years in our lab at The University of New Mexico," said Asmerom. "Judicious investments in instrumentation and techniques result in these kinds of high-impact dividends."

"Sea level changes at Artà Cave can be caused by the melting and growing of ice sheets or by uplift or subsidence of the island itself," said Columbia University Assistant Professor Jacky Austermann, a member of the research team. She used numerical and statistical models to carefully analyze how much uplift or subsidence might have happened since the Pliocene and subtracted this from the elevation of the formations they investigated.

One key interval of particular interest during the Pliocene is the mid Piacenzian Warm Period -- some 3.264 to 3.025 million years ago -- when temperatures were 2 to 3º Celsius higher than pre-industrial levels. "The interval also marks the last time the Earth's atmospheric CO2 was as high as today, providing important clues about what the future holds in the face of current anthropogenic warming," Onac says.

This study found that during this period, global mean sea level was as high as 16.2 meters (with an uncertainty range of 5.6 to 19.2 meters) above present. This means that even if atmospheric CO2 stabilizes around current levels, the global mean sea level would still likely rise at least that high, if not higher, the scientists concluded. In fact, it is likely to rise higher because of the increase in the volume of the oceans due to rising temperature.

"Considering the present-day melt patterns, this extent of sea level rise would most likely be caused by a collapse of both Greenland and the West Antarctic ice sheets," Dumitru said.

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Scientists map huge undersea fresh-water aquifer off U.S. Northeast

Aerial view of the ocean at Chatham, Cape Cod.

In a new survey of the sub-seafloor off the U.S. Northeast coast, scientists have made a surprising discovery: a gigantic aquifer of relatively fresh water trapped in porous sediments lying below the salty ocean. It appears to be the largest such formation yet found in the world. The aquifer stretches from the shore at least from Massachusetts to New Jersey, extending more or less continuously out about 50 miles to the edge of the continental shelf. If found on the surface, it would create a lake covering some 15,000 square miles. The study suggests that such aquifers probably lie off many other coasts worldwide, and could provide desperately needed water for arid areas that are now in danger of running out.

The researchers employed innovative measurements of electromagnetic waves to map the water, which remained invisible to other technologies. "We knew there was fresh water down there in isolated places, but we did not know the extent or geometry," said lead author Chloe Gustafson, a PhD. candidate at Columbia University's Lamont-Doherty Earth Observatory. "It could turn out to be an important resource in other parts of the world." The study appears this week in the journal Scientific Reports.

The first hints of the aquifer came in the 1970s, when companies drilled off the coastline for oil, but sometimes instead hit fresh water. Drill holes are just pinpricks in the seafloor, and scientists debated whether the water deposits were just isolated pockets or something bigger. Starting about 20 years ago, study coauthor Kerry Key, now a Lamont-Doherty geophysicist, helped oil companies develop techniques to use electromagnetic imaging of the sub-seafloor to look for oil. More recently, Key decided to see if some form of the technology could also be used also to find fresh-water deposits. In 2015, he and Rob L. Evans of Woods Hole Oceanographic Institution spent 10 days on the Lamont-Doherty research vessel Marcus G. Langseth making measurements off southern New Jersey and the Massachusetts island of Martha's Vineyard, where scattered drill holes had hit fresh-water-rich sediments.

They dropped receivers to the seafloor to measure electromagnetic fields below, and the degree to which natural disruptions such as solar winds and lightning strikes resonated through them. An apparatus towed behind the ship also emitted artificial electromagnetic pulses and recorded the same type of reactions from the subseafloor. Both methods work in a simple way: salt water is a better conductor of electromagnetic waves than fresh water, so the freshwater stood out as a band of low conductance. Analyses indicated that the deposits are not scattered; they are more or less continuous, starting at the shoreline and extending far out within the shallow continental shelf -- in some cases, as far as 75 miles. For the most part, they begin at around 600 feet below the ocean floor, and bottom out at about 1,200 feet.

The consistency of the data from both study areas allowed to the researchers to infer with a high degree of confidence that fresh water sediments continuously span not just New Jersey and much of Massachusetts, but the intervening coasts of Rhode Island, Connecticut and New York. They estimate that the region holds at least 670 cubic miles of fresh water. If future research shows the aquifer extends further north and south, it would rival the great Ogallala Aquifer, which supplies vital groundwater to eight Great Plains states, from South Dakota to Texas.

The water probably got under the seabed in one of two different ways, say the researchers. Some 15,000 to 20,000 years ago, toward the end of the last glacial age, much of the world's water was locked up in mile-deep ice; in North America, it extended through what is now northern New Jersey, Long Island and the New England coast. Sea levels were much lower, exposing much of what is now the underwater U.S. continental shelf. When the ice melted, sediments formed huge river deltas on top of the shelf, and fresh water got trapped there in scattered pockets. Later, sea levels rose. Up to now, the trapping of such "fossil" water has been the common explanation for any fresh water found under the ocean.

But the researchers say the new findings indicate that the aquifer is also being fed by modern subterranean runoff from the land. As water from rainfall and water bodies percolates through onshore sediments, it is likely pumped seaward by the rising and falling pressure of tides, said Key. He likened this to a person pressing up and down on a sponge to suck in water from the sponge's sides. Also, the aquifer is generally freshest near the shore, and saltier the farther out you go, suggesting that it mixes gradually with ocean water over time. Terrestrial fresh water usually contains less than 1 part per thousand salt, and this is about the value found undersea near land. By the time the aquifer reaches its outer edges, it rises to 15 parts per thousand. (Typical seawater is 35 parts per thousand.)

Read more at Science Daily

Researchers create hydrogen fuel from seawater

A prototype device used solar energy to create hydrogen fuel from seawater.

Stanford researchers have devised a way to generate hydrogen fuel using solar power, electrodes and saltwater from San Francisco Bay.

The findings, published March 18 in Proceedings of the National Academy of Sciences, demonstrate a new way of separating hydrogen and oxygen gas from seawater via electricity. Existing water-splitting methods rely on highly purified water, which is a precious resource and costly to produce.

Theoretically, to power cities and cars, "you need so much hydrogen it is not conceivable to use purified water," said Hongjie Dai, J.G. Jackson and C.J. Wood professor in chemistry at Stanford and co-senior author on the paper. "We barely have enough water for our current needs in California."

Hydrogen is an appealing option for fuel because it doesn't emit carbon dioxide, Dai said. Burning hydrogen produces only water and should ease worsening climate change problems.

Dai said his lab showed proof-of-concept with a demo, but the researchers will leave it up to manufacturers to scale and mass produce the design.

Tackling corrosion

As a concept, splitting water into hydrogen and oxygen with electricity -- called electrolysis -- is a simple and old idea: a power source connects to two electrodes placed in water. When power turns on, hydrogen gas bubbles out of the negative end -- called the cathode -- and breathable oxygen emerges at the positive end -- the anode.

But negatively charged chloride in seawater salt can corrode the positive end, limiting the system's lifespan. Dai and his team wanted to find a way to stop those seawater components from breaking down the submerged anodes.

The researchers discovered that if they coated the anode with layers that were rich in negative charges, the layers repelled chloride and slowed down the decay of the underlying metal.

They layered nickel-iron hydroxide on top of nickel sulfide, which covers a nickel foam core. The nickel foam acts as a conductor -- transporting electricity from the power source -- and the nickel-iron hydroxide sparks the electrolysis, separating water into oxygen and hydrogen. During electrolysis, the nickel sulfide evolves into a negatively charged layer that protects the anode. Just as the negative ends of two magnets push against one another, the negatively charged layer repels chloride and prevents it from reaching the core metal.

Without the negatively charged coating, the anode only works for around 12 hours in seawater, according to Michael Kenney, a graduate student in the Dai lab and co-lead author on the paper. "The whole electrode falls apart into a crumble," Kenney said. "But with this layer, it is able to go more than a thousand hours."

Previous studies attempting to split seawater for hydrogen fuel had run low amounts of electric current, because corrosion occurs at higher currents. But Dai, Kenney and their colleagues were able to conduct up to 10 times more electricity through their multi-layer device, which helps it generate hydrogen from seawater at a faster rate.

"I think we set a record on the current to split seawater," Dai said.

The team members conducted most of their tests in controlled laboratory conditions, where they could regulate the amount of electricity entering the system. But they also designed a solar-powered demonstration machine that produced hydrogen and oxygen gas from seawater collected from San Francisco Bay.

And without the risk of corrosion from salts, the device matched current technologies that use purified water. "The impressive thing about this study was that we were able to operate at electrical currents that are the same as what is used in industry today," Kenney said.

Surprisingly simple

Looking back, Dai and Kenney can see the simplicity of their design. "If we had a crystal ball three years ago, it would have been done in a month," Dai said. But now that the basic recipe is figured out for electrolysis with seawater, the new method will open doors for increasing the availability of hydrogen fuel powered by solar or wind energy.

In the future, the technology could be used for purposes beyond generating energy. Since the process also produces breathable oxygen, divers or submarines could bring devices into the ocean and generate oxygen down below without having to surface for air.

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