What the past tells us about modern sea-level rise

Researchers from the University of Southampton and the Australian National University report that sea-level rise since the industrial revolution has been fast by natural standards and – at current rates – may reach 80cm above the modern level by 2100 and 2.5 metres by 2200.

The team used geological evidence of the past few million years to derive a background pattern of natural sea-level rise. This was compared with historical tide-gauge and satellite observations of sea-level change for the ‘global warming’ period, since the industrial revolution. The study, which was funded by the Natural Environment Research Council (iGlass consortium) and Australian Research Council (Laureate Fellowship), is published in the journal Scientific Reports.

Lead author Professor Eelco Rohling, from the Australian National University and formerly of the University of Southampton, says: “Our natural background pattern from geological evidence should not be confused with a model-based prediction. It instead uses data to illustrate how fast sea level might change if only normal, natural processes were at work. There is no speculation about any new mechanisms that might develop due to man-made global warming. Put simply, we consider purely what nature has done before, and therefore could do again.”

Co-author Dr Gavin Foster, a Reader in Ocean and Earth Science at the University of Southampton, who is based at the National Oceanography Centre, Southampton (NOCS), explains: “Geological data showed that sea level would likely rise by nine metres or more as the climate system adjusts to today’s greenhouse effect. But the timescale for this was unclear. So we studied past rates and timescales of sea-level rise, and used these to determine the natural background pattern.”

Co-author Dr Ivan Haigh, lecturer in coastal oceanography at the University of Southampton and also based at NOCS, adds: “Historical observations show a rising sea level from about 1800 as sea water warmed up and melt water from glaciers and ice fields flowed into the oceans. Around 2000, sea level was rising by about three mm per year. That may sound slow, but it produces a significant change over time.”

The natural background pattern allowed the team to see whether recent sea-level changes are exceptional or within the normal range, and whether they are faster, equal, or slower than natural changes.

Professor Rohling concludes: “For the first time, we can see that the modern sea-level rise is quite fast by natural standards. Based on our natural background pattern, only about half the observed sea-level rise would be expected.

“Although fast, the observed rise still is (just) within the ‘natural range’. While we are within this range, our current understanding of ice-mass loss is adequate. Continued monitoring of future sea-level rise will show if and when it goes outside the natural range. If that happens, then this means that our current understanding falls short, potentially with severe consequences.”

Global map to predict giant earthquakes

A team of international researchers, led by Monash University’s Associate Professor Wouter Schellart, have developed a new global map of subduction zones, illustrating which ones are predicted to be capable of generating giant earthquakes and which ones are not.

The new research, published in the journal Physics of the Earth and Planetary Interiors, comes nine years after the giant earthquake and tsunami in Sumatra in December 2004, which devastated the region and many other areas surrounding the Indian Ocean, and killed more than 200,000 people.

Since then two other giant earthquakes have occurred at subduction zones, one in Chile in February 2010 and one in Japan in March 2011, which both caused massive destruction, killed many thousands of people and resulted in billions of dollars of damage.

Most earthquakes occur at the boundaries between tectonic plates that cover the Earth’s surface. The largest earthquakes on Earth only occur at subduction zones, plate boundaries where one plate sinks (subducts) below the other into the Earth’s interior. So far, seismologists have recorded giant earthquakes for only a limited number of subduction zone segments. But accurate seismological records go back to only ~1900, and the recurrence time of giant earthquakes can be many hundreds of years.

“The main question is, are all subduction segments capable of generating giant earthquakes, or only some of them? And if only a limited number of them, then how can we identify these,” Dr Schellart said.

Dr Schellart, of the School of Geosciences, and Professor Nick Rawlinson from the University of Aberdeen in Scotland used earthquake data going back to 1900 and data from subduction zones to map the main characteristics of all active subduction zones on Earth. They investigated if those subduction segments that have experienced a giant earthquake share commonalities in their physical, geometrical and geological properties.

They found that the main indicators include the style of deformation in the plate overlying the subduction zone, the level of stress at the subduction zone, the dip angle of the subduction zone, as well as the curvature of the subduction zone plate boundary and the rate at which it moves.

Through these findings Dr Schellart has identified several subduction zone regions capable of generating giant earthquakes, including the Lesser Antilles, Mexico-Central America, Greece, the Makran, Sunda, North Sulawesi and Hikurangi.

“For the Australian region subduction zones of particular significance are the Sunda subduction zone, running from the Andaman Islands along Sumatra and Java to Sumba, and the Hikurangi subduction segment offshore the east coast of the North Island of New Zealand. Our research predicts that these zones are capable of producing giant earthquakes,” Dr Schellart said.

“Our work also predicts that several other subduction segments that surround eastern Australia (New Britain, San Cristobal, New Hebrides, Tonga, Puysegur), are not capable of producing giant earthquakes.”

Study uncovers new evidence for assessing tsunami risk from very large volcanic island landslides

A core is extracted from the seabed. -  Russell Wynn
A core is extracted from the seabed. – Russell Wynn

The risk posed by tsunami waves generated by Canary Island landslides may need to be re-evaluated, according to researchers at the National Oceanography Centre. Their findings suggest that these landslides result in smaller tsunami waves than previously thought by some authors, because of the processes involved.

The researchers used the geological record from deep marine sediment cores to build a history of regional landslide activity over the last 1.5 million years. They found that each large-scale landslide event released material into the ocean in stages, rather than simultaneously as previously thought.

The findings – reported recently in the scientific journal Geochemistry Geophysics Geosystems – can be used to inform risk assessment from landslide-generated tsunamis in the area, as well as mitigation strategies to defend human populations and infrastructure against these natural hazards. The study also concluded that volcanic activity could be a pre-condition to major landslide events in the region.

The main factor influencing the amplitude of a landslide-generated tsunami is the volume of material sliding into the ocean. Previous efforts, which have assessed landslide volumes, have assumed that the entire landslide volume breaks away and enters the ocean as a single block. Such studies – and subsequent media coverage – have suggested an event could generate a ‘megatsunami’ so big that it would travel across the Atlantic Ocean and devastate the east coast of the US, as well as parts of southern England.

The recent findings shed doubt on this theory. Instead of a single block failure, the landslides in the past have occurred in multiple stages, reducing the volumes entering the sea, and thereby producing smaller tsunami waves. Lead author Dr James Hunt explains: “If you drop a block of soap into a bath full of water, it makes a relatively big splash. But if you break it up into smaller pieces and drop it in bit by bit, the ripples in the bath water are smaller.”

The scientists were able to identify this mechanism from the deposits of underwater sediment flows called turbidity currents, which form as the landslide mixes with surrounding seawater. Their deposits, known as ‘turbidites’, were collected from an area of the seafloor hundreds of miles away from the islands. Turbidites provide a record of landslide history because they form from the material that slides down the island slopes into the ocean, breaks up and eventually settles on this flatter, deeper part of the seafloor.

However, the scientists could not assume that multistage failure necessarily results in less devastating tsunamis – the stages need to occur with enough time in between so that the resulting waves do not compound each other. “If you drop the smaller pieces of soap in one by one but in very quick succession, you can still generate a large wave,” says Dr Hunt.

Between the layers of sand deposited by the landslides, the team found mud, providing evidence that the stages of failure occurred some time apart. This is because mud particles are so fine that they most likely take weeks to settle out in the ocean, and even longer to form a layer that would be resistant enough to withstand a layer of sand moving over the top of it.

While the authors suggest that the tsunamis were not as big as originally thought, they state that tsunamis are a threat that the UK should be taking seriously. The Natural Environment Research Council (NERC) is investing in a major programme looking at the risk of tsunamis from Arctic landslides as part of the Arctic Research Programme, of which NOC is the lead collaborator. The EU have also just funded a £6 million FP7 project called ASTARTE, looking at tsunami risk and resilience on the European North Atlantic and Mediterranean coasts, of which NOC is a partner.

The current study was funded by NERC, through a NOC studentship.

East Antarctica is sliding sideways

It’s official: East Antarctica is pushing West Antarctica around.

Now that West Antarctica is losing weight–that is, billions of tons of ice per year–its softer mantle rock is being nudged westward by the harder mantle beneath East Antarctica.

The discovery comes from researchers led by The Ohio State University, who have recorded GPS measurements that show West Antarctic bedrock is being pushed sideways at rates up to about twelve millimeters–about half an inch–per year. This movement is important for understanding current ice loss on the continent, and predicting future ice loss.

They reported the results on Thursday, Dec. 12 at the American Geophysical Union meeting in San Francisco.

Half an inch doesn’t sound like a lot, but it’s actually quite dramatic compared to other areas of the planet, explained Terry Wilson, professor of earth sciences at Ohio State. Wilson leads POLENET, an international collaboration that has planted GPS and seismic sensors all over the West Antarctic Ice Sheet.

She and her team weren’t surprised to detect the horizontal motion. After all, they’ve been using GPS to observe vertical motion on the continent since the 1990’s.

They were surprised, she said, to find the bedrock moving towards regions of greatest ice loss.

“From computer models, we knew that the bedrock should rebound as the weight of ice on top of it goes away,” Wilson said. “But the rock should spread out from the site where the ice used to be. Instead, we see movement toward places where there was the most ice loss.”

The seismic sensors explained why. By timing how fast seismic waves pass through the earth under Antarctica, the researchers were able to determine that the mantle regions beneath east and west are very different. West Antarctica contains warmer, softer rock, and East Antarctica has colder, harder rock.

Stephanie Konfal, a research associate with POLENET, pointed out that where the transition is most pronounced, the sideways movement runs perpendicular to the boundary between the two types of mantle.

She likened the mantle interface to a pot of honey.

“If you imagine that you have warm spots and cold spots in the honey, so that some of it is soft and some is hard,” Konfal said, “and if you press down on the surface of the honey with a spoon, the honey will move away from the spoon, but the movement won’t be uniform. The hard spots will push into the soft spots. And when you take the spoon away, the soft honey won’t uniformly flow back up to fill the void, because the hard honey is still pushing on it.”

Or, put another way, ice compressed West Antarctica’s soft mantle. Some ice has melted away, but the soft mantle isn’t filling back in uniformly, because East Antarctica’s harder mantle is pushing it sideways. The crust is just along for the ride.

This finding is significant, Konfal said, because we use these crustal motions to understand ice loss.

“We’re witnessing expected movements being reversed, so we know we really need computer models that can take lateral changes in mantle properties into account.”

Wilson said that such extreme differences in mantle properties are not seen elsewhere on the planet where glacial rebound is occurring.

“We figured Antarctica would be different,” she said. “We just didn’t know how different.”

Ohio State’s POLENET academic partners in the United States are Pennsylvania State University, Washington University, New Mexico Tech, Central Washington University, the University of Texas Institute for Geophysics and the University of Memphis. A host of international partners are part of the effort as well. The project is supported by the UNAVCO and IRIS-PASSCAL geodetic and seismic facilities.

Supervolcanoes discovered in Utah

Brigham Young University geologists found evidence of some of the largest volcanic eruptions in earth’s history right in their own backyard.

These supervolcanoes aren’t active today, but 30 million years ago more than 5,500 cubic kilometers of magma erupted during a one-week period near a place called Wah Wah Springs. By comparison, this eruption was about 5,000 times larger than the 1980 Mount St. Helens eruption.

“In southern Utah, deposits from this single eruption are 13,000 feet thick,” said Eric Christiansen, the lead author for the BYU study. “Imagine the devastation – it would have been catastrophic to anything living within hundreds of miles.”

Dinosaurs were already extinct during this time period, but what many people don’t know is that 25-30 million years ago, North America was home to rhinos, camels, tortoises and even palm trees. Evidence of the ancient flora and fauna was preserved by volcanic deposits.

The research group, headed by Christiansen and professor emeritus Myron Best, measured the thickness of the pyroclastic flow deposits. They used radiometric dating, X-ray fluorescence spectrometry, and chemical analysis of the minerals to verify that the volcanic ash was all from the same ancient super-eruption.

They found that the Wah Wah Springs eruption buried a vast region extending from central Utah to central Nevada and from Fillmore on the north to Cedar City on the south. They even found traces of ash as far away as Nebraska.

But this wasn’t an isolated event; the BYU geologists found evidence of fifteen super-eruptions and twenty large calderas. The scientific journal Geosphere recently published two of their papers detailing the discoveries.

Despite their enormous size, the supervolcanoes have been hidden in plain sight for millions of years.

“The ravages of erosion and later deformation have largely erased them from the landscape, but our careful work has revealed their details,” said Christiansen. “The sheer magnitude of this required years of work and involvement of dozens of students in putting this story together.”

Supervolcanoes are different from the more familiar “straddle” volcanoes – like Mount St. Helens – because they aren’t as obvious to the naked eye and they affect enormous areas.

“Supervolcanoes as we’ve seen are some of earth’s largest volcanic edifices, and yet they don’t stand as high cones,” said Christiansen. “At the heart of a supervolcano instead, is a large collapse.”

Those collapses in supervolcanoes occur with the eruption and form enormous holes in the ground in plateaus, known as calderas.

Not many people know that there are still active supervolcanoes today. Yellowstone National Park in Wyoming is home to one roughly the same size as the Wah Wah Springs caldera, which was about 25 miles across and 3 miles deep when it first formed.

Runaway process drives intermediate-depth earthquakes, scientists find

Stanford scientists may have solved the mystery of what drives a type of earthquake that occurs deep within the Earth and accounts for one in four quakes worldwide.

Known as intermediate-depth earthquakes, these temblors originate farther down inside the Earth than shallow earthquakes, which take place in the uppermost layer of the Earth’s surface, called the crust. The kinds of quakes that afflict California and most other places in the world are shallow earthquakes.

“Intermediate-depth earthquakes occur at depths of about 30 miles down to about 190 miles,” said Greg Beroza, a professor of geophysics at Stanford and a coauthor of a new study that will be published in an upcoming issue of the journal Geophysical Research Letters.

Unlike shallow earthquakes, the cause of intermediate quakes is not well-understood. Part of the problem is that the mechanism for shallow earthquakes should not physically work for quakes at greater depths.

“Shallow earthquakes occur when stress building up at faults overcomes friction, resulting in sudden slip and energy release,” Beroza said. “That mechanism shouldn’t work at the higher pressures and temperatures at which intermediate depth earthquakes occur.”

A better understanding of intermediate-depth quakes could help scientists forecast where they will occur and the risk they pose to buildings and people.

“They represent 25 percent of the catalog of earthquakes, and some of them are large enough to produce damage and deaths,” said study first author Germán Prieto, an assistant professor of geophysics at the Massachusetts Institute of Technology.

A tale of two theories

There are two main hypotheses for what may be driving intermediate depth earthquakes. According to one idea, water is squeezed out of rock pores at extreme depths and the liquid acts like a lubricant to facilitate fault sliding. This fits with the finding that intermediate quakes generally occur at sites where one tectonic plate is sliding, or subducting, beneath another.

“Typically, subduction involves oceanic plates whose rocks contain lots of water,” Beroza said.

A competing idea is that as rocks at extreme depths deform, they generate heat due to friction. The heated rocks become more malleable, or plastic, and as a result slide more easily against each other. This can create a positive feedback loop that further weakens the rock and increases the likelihood of fault slippage.

“It’s a runaway process in which the increasing heat generates more slip, and more slip generates more heat and so on,” Prieto said.

To distinguish between the two possible mechanisms, the scientists studied a site near the city of Bucaramanga in Colombia that boasts the highest concentration of intermediate quakes in the world. About 18 intermediate depth temblors rattle Bucaramanga every day. Most are magnitude 2 to 3, weak quakes that are detectable only by sensitive instruments.

But about once a month one occurs that is magnitude 5 or greater – strong enough to be felt by the city’s residents. Moreover, past studies have revealed that most of the quakes appear to be concentrated at a site located about 90 miles beneath the Earth’s surface that scientists call the Bucaramanga Nest.

A natural laboratory

This type of clustering is highly unusual and makes the Bucaramanga Nest a “natural laboratory” for studying intermediate depth earthquakes. Comparison studies of intermediate quakes from different parts of the world are difficult because the makeup of the Earth’s crust and mantle can vary widely by location.

In the Bucaramanga Nest, however, the intermediate quakes are so closely packed together that for the purposes of scientific studies and computer models, it’s as if they all occurred at the same spot. This vastly simplifies calculations, Beroza said.

“When comparing a magnitude 2 and a magnitude 5 intermediate depth earthquake that are far apart, you have to model everything, including differences in the makeup of the Earth’s surface,” he said. “But if they’re close together, you can assume that the seismic waves of both quakes suffered the same distortions as they traveled toward the Earth’s surface.”

By studying seismic waves picked up by digital seismometers installed on the Earth’s surface above the Bucaramanga Nest, the scientists were able to measure two key parameters of the intermediate quakes happening deep underground.

One, called the stress drop, allowed the team to estimate the total amount of energy released during the fault slips that caused the earthquakes. The other was radiated energy, which is a measure of how much of the energy generated by the fault slip is actually converted to seismic waves that propagate through the Earth to shake the surface.

Two things immediately stood out to the researchers. One was that the stress drop for intermediate quakes increased along with their magnitudes. That is, larger intermediate quakes released proportionally more total energy than smaller ones. Second, the amount of radiated energy released by intermediate earthquakes accounted for only a tiny portion of the total energy as calculated by the stress drop.

“For these intermediate-depth earthquakes in Colombia, the amount of energy converted to seismic waves is only a small fraction of the total energy,” Beroza said.

The implication is that intermediate earthquakes are expending most of their energy locally, likely in the form of heat.

“This is compelling evidence for a thermal runaway failure mechanism for intermediate earthquakes, in which a slipping fault generates heat. That allows for more slip and even more heat, and a positive feedback loop is created,” said study coauthor Sarah Barrett, a Stanford graduate student in Beroza’s research group.

Rising mountains dried out Central Asia, scientists say

A record of ancient rainfall teased from long-buried sediments in Mongolia is challenging the popular idea that the arid conditions prevalent in Central Asia today were caused by the ancient uplift of the Himalayas and the Tibetan Plateau.

Instead, Stanford scientists say the formation of two lesser mountain ranges, the Hangay and the Altai, may have been the dominant drivers of climate in the region, leading to the expansion of Asia’s largest desert, the Gobi. The findings will be presented on Thursday, Dec. 12, at the annual meeting of the American Geophysical Union (AGU) in San Francisco.

“These results have major implications for understanding the dominant factors behind modern-day Central Asia’s extremely arid climate and the role of mountain ranges in altering regional climate,” said Page Chamberlain, a professor of environmental Earth system science at Stanford.

Scientists previously thought that the formation of the Himalayan mountain range and the Tibetan plateau around 45 million years ago shaped Asia’s driest environments.

“The traditional explanation has been that the uplift of the Himalayas blocked air from the Indian Ocean from reaching central Asia,” said Jeremy Caves, a doctoral student in Chamberlain’s terrestrial paleoclimate research group who was involved in the study.

This process was thought to have created a distinct rain shadow that led to wetter climates in India and Nepal and drier climates in Central Asia. Similarly, the elevation of the Tibetan Plateau was thought to have triggered an atmospheric process called subsidence, in which a mass of air heated by a high elevation slowly sinks into Central Asia.

“The falling air suppresses convective systems such as thunderstorms, and the result is you get really dry environments,” Caves said.

This long-accepted model of how Central Asia’s arid environments were created mostly ignores, however, the existence of the Altai and Hangay, two northern mountain ranges.

Searching for answers

To investigate the effects of the smaller ranges on the regional climate, Caves and his colleagues from Stanford and Rocky Mountain College in Montana traveled to Mongolia in 2011 and 2012 and collected samples of ancient soil, as well as stream and lake sediments from remote sites in the central, southwestern and western parts of the country.

The team carefully chose its sites by scouring the scientific literature for studies of the region conducted by pioneering researchers in past decades.

“A lot of the papers were by Polish and Russian scientists who went there to look for dinosaur fossils,” said Hari Mix, a doctoral student at Stanford who also participated in the research. “Indeed, at many of the sites we visited, there were dinosaur fossils just lying around.”

The earlier researchers recorded the ages and locations of the rocks they excavated as part of their own investigations; Caves and his team used those age estimates to select the most promising sites for their own study.

At each site, the team bagged sediment samples that were later analyzed to determine their carbon isotope content. The relative level of carbon isotopes present in a soil sample is related to the productivity of plants growing in the soil, which is itself dependent on the annual rainfall. Thus, by measuring carbon isotope amounts from different sediment samples of different ages, the team was able to reconstruct past precipitation levels.

An ancient wet period

The new data suggest that rainfall in central and southwestern Mongolia had decreased by 50 to 90 percent in the last several tens of million of years.

“Right now, precipitation in Mongolia is about 5 inches annually,” Caves said. “To explain our data, rainfall had to decrease from 10 inches a year or more to its current value over the last 10 to 30 million years.”

That means that much of Mongolia and Central Asia were still relatively wet even after the formation of the Himalayas and the Tibetan Plateau 45 million years ago. The data show that it wasn’t until about 30 million years ago, when the Hangay Mountains first formed, that rainfall started to decrease. The region began drying out even faster about 5 million to 10 million years ago, when the Altai Mountains began to rise.

The scientists hypothesize that once they formed, the Hangay and Altai ranges created rain shadows of their own that blocked moisture from entering Central Asia.

“As a result, the northern and western sides of these ranges are wet, while the southern and eastern sides are dry,” Caves said.

The team is not discounting the effect of the Himalayas and the Tibetan Plateau entirely, because portions of the Gobi Desert likely already existed before the Hangay or Altai began forming.

“What these smaller mountains did was expand the Gobi north and west into Mongolia,” Caves said.

The uplift of the Hangay and Altai may have had other, more far-reaching implications as well, Caves said. For example, westerly winds in Asia slam up against the Altai today, creating strong cyclonic winds in the process. Under the right conditions, the cyclones pick up large amounts of dust as they snake across the Gobi Desert. That dust can be lofted across the Pacific Ocean and even reach California, where it serves as microscopic seeds for developing raindrops.

The origins of these cyclonic winds, as well as substantial dust storms in China today, may correlate with uplift of the Altai, Caves said. His team plans to return to Mongolia and Kazakhstan next summer to collect more samples and to use climate models to test whether the Altai are responsible for the start of the large dust storms.

“If the Altai are a key part of regulating Central Asia’s climate, we can go and look for evidence of it in the past,” Caves said.

Shale sequestration, water for energy & soil microbes

Scientists from the Department of Energy’s Pacific Northwest National Laboratory will present a variety of their research at the 2013 American Geophysical Union Fall Meeting, which runs Monday, Dec. 9 through Friday, Dec. 13 at the Moscone Convention Center in San Francisco. Among the noteworthy PNNL research scheduled to be discussed are carbon sequestration in empty shale reservoirs, water needs for future energy production and how soil microbes adjust to climate change. More information is below.

Chemistry informs economics of carbon sequestration at shale gas sites

Shale formations – underground mixes of mud, minerals and gas that have sparked a natural gas drilling boom in the United States – could also help power plants meet proposed EPA emission regulations by permanently storing carbon dioxide. But while many pollution-emitting power plants are located near shale formations, little is known about the complex chemistry of shales reacting with pumped-in carbon emissions. The issue is complicated by the variety of different clay minerals that make up shales. PNNL scientists are getting to the bottom of these details by conducting laboratory experiments and computer modeling research to determine how carbon dioxide, methane and common power plant byproducts such as sulfur dioxide react with the four clays common in shales. Early results show the clay mineral montmorillonite expands to hold more carbon emissions under certain conditions. Tests also show the clay kaolinite has a sweet spot to absorb emissions with an ideal combination of pressure and carbon dioxide concentrations. PNNL geologist Todd Schaef will present these and other results, including a preliminary cost-benefit analysis of carbon sequestration at the United States’ shale gas reservoirs.

MR21B-5: “CO2 Utilization and Storage in Shale Gas Reservoirs,” 9-9:15 a.m., Tuesday, Dec. 10, 301 (Moscone South).

Water consumption to increase with future U.S. energy needs

Future power plants can use more water-efficient cooling technologies to withdraw less water from rivers and ponds, but PNNL research shows there is a tradeoff. Water-efficient cooling technologies typically reuse water instead of using it just once, but they also warm the reused water and cause evaporation that removes water from the local ecosystem. PNNL used a computer model to estimate future energy generation and associated water use for each of the 50 states. The detailed analysis found while the nation’s energy sector could withdraw less water with advanced cooling technologies, the amount of water consumed through evaporation would increase. The study also identified several other trends, such as energy-related water withdrawals decreasing in the Eastern U.S. while they increase in the West. PNNL environmental scientist Lu Liu will present a poster on this research.

H11J-1274: “An integrated assessment of energy-water nexus at the state level in the United States: Projections and analyses under different scenarios through 2095,” 8 a.m. – 12:20 p.m., Tuesday, Dec. 10, Hall A-C (Moscone South).

Climate change alters bacteria behavior

Climate change doesn’t affect just polar bears and ice caps; it also impacts the tiny microbes that help plants soak up nutrients in the soil. New research shows transplanted soil bacteria adjust their enzyme production to better survive in a new climate. The findings are a result of a unique study where soil samples were transplanted between two elevations about 1700 feet apart on an isolated mountain in rural Washington state. The scientists gave the transplanted soil about 17 years to settle into its new surroundings and then compared its bacteria with bacteria in unmoved soil samples. The researchers found bacteria made more of some enzymes in the higher-up soil, where it’s wetter and cooler and there’s more vegetation. The enzymes found in greater abundance break down cellulose – the tough, pithy material that gives plants structure – and chitin – another tough material that strengthens fungal cell walls. The researchers hypothesize the higher-elevation bacteria produce more of those enzymes because the richer soils there are home to more plants and fungi for the bacteria to digest. Better understanding how climate impacts microbes can also help us better understand climate change, as many of the greenhouse gases that contribute to climate change occur as a result of interactions with microbes. PNNL microbiologist Vanessa Bailey will present a poster on this research.

B51D-0311: “Bacterial Community Structure after a 17-year Reciprocal Soil Transplant Simulating Climate Change with Elevation,” 8 a.m. – Noon, Friday, Dec. 13, Hall A-C (Moscone South).

Hard rock life

Scientists are digging deep into the Earth’s surface collecting census data on the microbial denizens of the hardened rocks. What they’re finding is that, even miles deep and halfway across the globe, many of these communities are somehow quite similar.

The results, which were presented at the American Geophysical Union conference Dec. 8, suggest that these communities may be connected, said Matthew Schrenk, Michigan State University geomicrobiologist.

“Two years ago we had a scant idea about what microbes are present in subsurface rocks or what they eat,” he said. “We’re now getting this emerging picture not only of what sort of organisms are found in these systems but some consistency between sites globally – we’re seeing the same types of organisms everywhere we look.”

Schrenk leads a team funded by the Alfred P. Sloan Foundation’s Deep Carbon Observatory studying samples from deep underground in California, Finland and from mine shafts in South Africa. The scientists also collect microbes from the deepest hydrothermal vents in the Caribbean Ocean.

“It’s easy to understand how birds or fish might be similar oceans apart,” Schrenk said. “But it challenges the imagination to think of nearly identical microbes 16,000 kilometers apart from each other in the cracks of hard rock at extreme depths, pressures and temperatures.”

Cataloging and exploring this region, a relatively unknown biome, could lead to breakthroughs in offsetting climate change, the discovery of new enzymes and processes that may be useful for biofuel and biotechnology research, he added.

For example, Schrenk’s future efforts will focus on unlocking answers to what carbon sources the microbes use, how they cope in such extreme conditions as well as how their enzymes evolved to function so deep underground.

“Integrating this region into existing models of global biogeochemistry and gaining better understanding into how deep rock-hosted organisms contribute or mitigate greenhouse gases could help us unlock puzzles surrounding modern-day Earth, ancient Earth and even other planets,” Schrenk said.

Collecting and comparing microbiological and geochemical data across continents is made possible through the DCO. The DCO has allowed scientists from across disciplines to better understand and describe these phenomena, he added.

Ocean crust could store many centuries of industrial CO2

Researchers from the University of Southampton have identified regions beneath the oceans where the igneous rocks of the upper ocean crust could safely store very large volumes of carbon dioxide.

The burning of fossil fuels such as coal, oil, and natural gas has led to dramatically increasing concentrations of CO2 in the atmosphere causing climate change and ocean acidification. Although technologies are being developed to capture CO2 at major sources such as power stations, this will only avoid further warming if that CO2 is then safely locked away from the atmosphere for centuries.

PhD student Chiara Marieni, who is based at the National Oceanography Centre, Southampton, investigated the physical properties of CO2 to develop global maps of the ocean floor to estimate where CO2 can be safely stored.

At high pressures and low temperatures, such as those in the deep oceans, CO2 occurs as a liquid that is denser than seawater. By estimating temperatures in the upper ocean crust, Chiara and her colleagues identified regions where it may be possible to stably store large volumes of CO2 in the basalts. These fractured rocks have high proportions of open space, and over time may also react with the CO2 so that it is locked into solid calcium carbonate, permanently preventing its release into the oceans or atmosphere. As a precaution, Chiara refined her locations to areas that have the additional protection of thick blankets of impermeable sediments to prevent gas escape.

They identified five potential regions in off-shore Australia, Japan, Siberia, South Africa and Bermuda, ranging in size from ½ million square kilometres to almost four million square kilometres.

Postgraduate researcher Chiara says: “We have found regions that have the potential to store decades to hundreds of years of industrial carbon dioxide emissions although the largest regions are far off shore. However, further work is needed in these regions to accurately measure local sediment conditions and sample the basalt beneath before this potential can be confirmed.”

The new work, which is published in Geophysical Research Letters, shows that previous studies, which concentrated on the effect of pressure to liquefy the CO2 but ignored temperature, have pointed to the wrong locations, where high temperatures mean that the CO2 will have a low density, and thus be more likely to escape.