Salty water and gas sucked into Earth’s interior helps unravel planetary evolution

An international team of scientists has provided new insights into the processes behind the evolution of the planet by demonstrating how salty water and gases transfer from the atmosphere into the Earth’s interior.

The paper was published in Nature Geoscience today.

Scientists have long argued about how the Earth evolved from a primitive state in which it was covered by an ocean of molten rock, into the planet we live on today with a solid crust made of moving tectonic plates, oceans and an atmosphere.

Lead author Dr Mark Kendrick from the University of Melbourne’s School of Earth Sciences said inert gases trapped inside the Earth’s interior provide important clues into the processes responsible for the birth of our planet and the subsequent evolution of its oceans and atmosphere.

“Our findings throw into uncertainty a recent conclusion that gases throughout the Earth were solely delivered by meteorites crashing into the planet,” he said.

The study shows atmospheric gases are mixed into the mantle, inside the Earth’s interior, during the process called ‘subduction’, when tectonic plates collide and submerge beneath volcanoes in subduction zones.

“This finding is important because it was previously believed that inert gases inside the Earth had primordial origins and were trapped during the formation of the solar system,” Dr Kendrick said.

Because the composition of neon in the Earth’s mantle is very similar to that in meteorites, it was recently suggested by scientists that most of the Earth’s gases were delivered by meteorites during a late meteorite bombardment that also generated visible craters on the Earth’s moon.

“Our study suggests a more complex history in which gases were also dissolved into the Earth while it was still covered by a molten layer, during the birth of the solar system,” he said.

It was previously assumed that gases could not sink with plates in tectonic subduction zones but escaped during eruption of overlying volcanoes.

“The new study shows this is not entirely true and the gases released from Earth’s interior have not faithfully preserved the fingerprint of solar system formation.”

To undergo the study researchers collected serpentinite rocks from mountain belts in Italy and Spain. These rocks originally formed on the seafloor and were partially subducted into the Earth’s interior before they were uplifted into their present positions by collision of the European and African plates.

“The serpentinite rocks are special because they trap large amounts of seawater in their crystal structure and can be transported to great depths in the Earth’s mantle by subduction,” he said.

By analysing the inert gases and halogens trapped in these rocks, the team was able to show gases are incompletely removed by the mineral transformations that affect serpentinites during the subduction process and hence provide new insights into the role of these trapped gases in the evolution of the planet.

‘Drilling Down’

This is the cover of 'Drilling Down.' -  Springer
This is the cover of ‘Drilling Down.’ – Springer

While news of the tragic Gulf oil spill has faded from nightly television newscasts and newspaper front pages, the underlying complex causes of the tragic accident are still with us today. In their new book “Drilling Down: The Gulf Oil Debacle and Our Energy Dilemma,” Joseph Tainter and Tadeusz Patzek explain the real causal factors leading up to the worst environmental catastrophe in U.S. history.

This disaster was not an isolated incident. The same processes and causal factors are at work in all areas of society from technology to business operations to government oversight, and even drive many of the everyday challenges of modern life.

Tad Patzek, a world expert on oil technology, and Joseph A. Tainter, one of our foremost social commentators and author of The Collapse of Complex Societies, join forces to:

  • Lead you on a fascinating tour from the events on the Deepwater Horizon to the processes in society that made the tragedy nearly inevitable
  • Explain the energy-complexity spiral that governs our way of life
  • Take you beyond the headlines, finger pointing, and political punditry to the underlying causes of the Gulf catastrophe
  • Help decision-makers from all walks of life to understand the risks and challenges of managing complex organizations
  • Discuss energy options for the future

Praise for “Drilling Down”:


‘In this book, Joseph Tainter and Tadeusz Patzek use the Gulf oil spill as a point of entry to discuss our energy future. For those of us who watched the oil spill from afar, this book provides the technical background to help us understand it, something that was never available from the media. For those like me, who are interested in the role of energy in the rise and fall of civilizations, this is a must read.’

–Lester R. Brown, President of Earth Policy Institute and author of “World on the Edge.”

Researchers’ chance viewing of river cutoff forming provides rare insight

Illinois professors Bruce Rhoads (left) and Jim Best (right) and graduate student Jessica Zinger (center) documented development of two cutoff channels in a bend in the Wabash River, pictured in the background. The cutoffs released huge amounts of sediment into the river. -  L. Brian Stauffer
Illinois professors Bruce Rhoads (left) and Jim Best (right) and graduate student Jessica Zinger (center) documented development of two cutoff channels in a bend in the Wabash River, pictured in the background. The cutoffs released huge amounts of sediment into the river. – L. Brian Stauffer

For University of Illinois river researchers, new insight into river cutoffs was a case of being in the right place at the right time.

Geography professor Bruce Rhoads and geology professor Jim Best were conducting research where the Wabash River meets the Ohio River in the summer of 2008 when they heard about a new channel that had just formed, cutting off a bend in the winding Wabash just upstream from the confluence. That serendipity gave the researchers a rare view of a dynamic, little-understood river process that changed the local landscape and deposited so much sediment into the river system that it closed the Ohio River.

“It was fortunate to be there right when it was beginning to happen, because these are hard-to-predict, unusual events, particularly on large rivers,” Rhoads said.

While cutoffs are common in meandering rivers, or rivers that wander across their floodplains, the conditions surrounding cutoff events are poorly understood. Most cutoffs are discovered long after they first develop. The Illinois team’s quick response to the 2008 Wabash cutoff, and witnessing of a second cutoff in the same bend a year later, allowed them to monitor the huge amounts of sediment the cutoffs released into the river. The researchers published their findings in the journal Nature Geoscience.

“Cutoffs occur in just about every meandering river on the face of the earth,” said Jessica Zinger, a graduate student and lead author of the paper. “Although it’s unusual to capture one like this, they are ubiquitous events, so it’s important to understand what happens when these cutoffs occur, why they occur when they do, and how they evolve after they occur.”

The two cutoffs, both 1 kilometer long, delivered about 6 million tons of sediment from the floodplain into the river – equivalent to 6.4 percent of the total annual sediment load of the entire Mississippi River basin (which the Wabash contributes to) – in a matter of days. It would take nearly 250 years of bank erosion to displace the same amount of sediment along the bend, had the cutoff not occurred. Such sediment pulses, as they are known, are more often associated with mountain rivers, rather than the relatively level landscape of rural Illinois.

“The first kilometer-long channel was cut in eight days, which is a phenomenal rate of erosion,” Best said. “There were banks collapsing, sediment moving; it’s probably one of the most dynamic river environments you’ll ever see, and you don’t expect that in lowland, flat-grade rivers.”

The researchers found that, after each cutoff, the majority of the sediment was deposited locally. In particular, a large percentage of the sediment accumulated where the Wabash joins the Ohio River. The new layer of sediment, up to 7 meters thick, raised the bed of the Ohio River and required dredging so that barges could continue to use the river.

The Wabash River study demonstrated that cutoffs can have large, immediate effects on sediment transport and deposition in a river – processes not accounted for in current models of meandering rivers.

“If we look at river systems and their role in the landscape, one of their most fundamental roles from a geoscience perspective is that they transport sediment from the land surfaces to ocean basins,” Rhoads said. “What has not been recognized is that these cutoff events can actually deliver large amounts of sediment to the river very rapidly. Then, the question is, since cutoffs are ubiquitous along a lot of meandering rivers, could this be something that we have not recognized fully as a major sediment delivery mechanism for all meandering rivers?”

The researchers plan to continue monitoring the cutoff and the areas just upstream and downstream to document how the cutoffs contribute to the river’s evolution. They anticipate that the river will abandon the bend and the first cutoff as more water is directed through the second cutoff, a more direct route for the river to flow. The abandoned bend will become a new wetland area, shaping the local ecology. The researchers will continue to measure and model changes in flow velocity, sediment transport and morphology in the river as the cutoff channel widens, providing valuable insight into cutoff effects and perhaps contributing to a model that could predict where such sediment pulses could occur.

“Our study brings attention to a whole range of elements – the basic science, the local effects, the ecological effects, the commercial effects – all from this one mechanism of channel change,” s said. “A lot of the meandering models that are out there treat cutoffs very schematically and they don’t deal with the processes that are occurring once a cutoff develops. I think that our work could really make people rethink that aspect of modeling the long-term evolution of meander bends.”

Finance sector top industry for geoscientist salaries

The American Geological Institute’s Workforce Program today released an analysis of salaries for geoscientists by industry relative to those of other scientific fields. Geoscience Currents 51 shows that in 2010, average aggregated salaries for geoscience-related occupations ranged from $137,660 for geoscience-related occupations in the finance and insurance industry to $69,949 for geoscience-related occupations in state government. Salary ranges for the aggregated occupations were as narrow as $26,250 for geoscience-related occupations in the health care industry ($102,640-$76,390) to as wide as $96,960 for geoscience-related occupations in the finance and insurance industry ($179,610-$82,650).

AGI will be hosting a free webinar discussion of the issue of geoscience salaries and the details of this and related recent Geoscience Currents on October 3 at 1 pm EDT. To register for the webinar, please visit : www.agiweb.org/workforce/webinars.html

A PDF version of this Geoscience Current is available for free download at http://www.agiweb.org/workforce/currents.html

3-D microscope opens eyes to prehistoric oceans and present-day resources

A University of Alberta research team has turned their newly developed 3-D microscope technology on ancient sea creatures and hopes to expand its use.

U of A engineering professor Dileepan Joseph and two graduate students produced a 3-D imaging system called Virtual Reflected-Light Microscopy. The technology consists of a regular optical microscope, a light source, a platform that moves the objects being photographed and software programs that extract shape and reflectance from images and transform this digital information into a 3-D image. To see the full effect on a computer screen viewers wear simple, paper framed 3-D glasses with red and cyan colored lenses. Viewers also control a virtual light source, which they reposition using their web browser.

The test subjects used in the development of the VRLM were drilling core samples taken from beneath the floor of the Pacific Ocean. Joseph, Ph.D candidate Adam Harrison and master’s student Cindy Wong produced 3-D images of ancient protozoa or microfossils that were mixed in with the sand and rock in the core samples.

Joseph says the VRLM gives geoscientists and computer programs in development much more information than simple images. The goal is to accelerate species identification of the tiny and numerous microfossils. Such identifications are used to date the rock from which the creatures are pulled. The microfossil species digitized by the U of A’s VLRM prototype were found in rock known by geologists to be 60 million years old.

Geoscientists can use that kind of strata dating information in Earth sciences research and in the search for energy resources. The U of A researchers say there are multiple industrial and academic uses for their 3-D microscope technology.

Deep oceans may mask global warming for years at a time

Earth’s deep oceans may absorb enough heat at times to flatten the rate of global warming for periods of as long as a decade–even in the midst of longer-term warming. This according to a new analysis led by scientists at the National Center for Atmospheric Research (NCAR).

The study, based on computer simulations of global climate, points to ocean layers deeper than 1,000 feet as the main location of the “missing heat” during periods such as the past decade when global air temperatures showed little trend.

The findings also suggest that several more intervals like this can be expected over the next century, even as the trend toward overall warming continues.

“We will see global warming go through hiatus periods in the future,” says NCAR’s Gerald Meehl, lead author of the study.

“However, these periods would likely last only about a decade or so, and warming would then resume. This study illustrates one reason why global temperatures do not simply rise in a straight line.”

The research, by scientists at NCAR and the Bureau of Meteorology in Australia, was published online Sunday in Nature Climate Change.

Funding for the study came from the National Science Foundation (NSF), NCAR’s sponsor.

“The research shows that the natural variability of the climate system can produce periods of a decade or more in which Earth’s temperature does not rise, despite an increase in greenhouse gas concentrations,” says Eric DeWeaver, program director in NSF’s Division of Atmospheric and Geospace Sciences.

“These scientists make a compelling case that the excess energy entering the climate system due to greenhouse gas increases may not be immediately realized as warmer surface temperatures, as it can go into the deep ocean instead.”

The 2000s were Earth’s warmest decade in more than a century of weather records.

However, the single-year mark for warmest global temperature, which had been set in 1998, remained unmatched until 2010.

Yet emissions of greenhouse gases continued to climb during this period, and satellite measurements showed that the discrepancy between incoming sunshine and outgoing radiation from Earth actually increased.

This implied that heat was building up somewhere on Earth, according to a 2010 study by NCAR researchers Kevin Trenberth and John Fasullo.

The two scientists, who are both co-authors on the new study, suggested that the oceans might be storing some of the heat that would otherwise go toward other processes, such as warming the atmosphere or land, or melting more ice and snow.

Observations from a global network of buoys showed some warming in the upper ocean, but not enough to account for the global build-up of heat.

Although scientists suspected the deep oceans were playing a role, few measurements were available to confirm that hypothesis.

To track where the heat was going, Meehl and colleagues used a powerful software tool known as the Community Climate System Model, which was developed by scientists at NCAR and the Department of Energy with colleagues at other organizations.

Using the model’s ability to portray complex interactions between the atmosphere, land, oceans and sea ice, they performed five simulations of global temperatures.

The simulations, which were based on projections of future greenhouse gas emissions from human activities, indicated that temperatures would rise by several degrees during this century.

But each simulation also showed periods in which temperatures would stabilize for about a decade before climbing again.

For example, one simulation showed the global average rising by about 2.5 degrees Fahrenheit (1.4 degrees Celsius) between 2000 and 2100, but with two decade-long hiatus periods during the century.

During these hiatus periods, simulations showed that extra energy entered the oceans, with deeper layers absorbing a disproportionate amount of heat due to changes in oceanic circulation.

The vast area of ocean below about 1,000 feet (300 meters) warmed by 18 percent to 19 percent more during hiatus periods than at other times.

In contrast, the shallower global ocean above 1,000 feet warmed by 60 percent less than during non-hiatus periods in the simulation.

“This study suggests the missing energy has indeed been buried in the ocean,” Trenberth says. “The heat has not disappeared and so it cannot be ignored. It must have consequences.”

The simulations also indicated that the oceanic warming during hiatus periods has a regional signature.

During a hiatus, average sea-surface temperatures decrease across the tropical Pacific, while they tend to increase at higher latitudes, especially in the Atlantic, where surface waters converge to push heat into deeper oceanic layers.

These patterns are similar to those observed during a La Niña event, according to Meehl.

He adds that El Niño and La Niña events can be overlaid on top of a hiatus-related pattern.

Global temperatures tend to drop slightly during La Niña, as cooler waters reach the surface of the tropical Pacific, and they rise slightly during El Niño, when those waters are warmer.

“The main hiatus in observed warming has corresponded with La Niña conditions, which is consistent with the simulations,” Trenberth says.

Understanding methane’s seabed escape

A shipboard expedition off Norway, to determine how methane escapes from beneath the Arctic seabed, has discovered widespread pockets of the gas and numerous channels that allow it to reach the seafloor.

Methane is a powerful “greenhouse” gas and the research, carried out over the past week aboard the Royal Research Ship James Clark Ross, will improve understanding of its origins in this area, its routes to the sea floor and how the amount of gas escaping might increase as the ocean warms. This could have important implications for global climate change and ocean acidification.

At the high pressures and low temperatures which are found at the bottom of the deep ocean, methane gas and water combine to form a solid, crystalline substance – methane hydrate. It is very widespread in the parts of the deep ocean nearest to the continents. If the ocean warms, the hydrate can become unstable and methane gas is unlocked and can make its way into the ocean, forming plumes of bubbles.

A research cruise to the same area in 2008, also aboard RRS James Clark Ross, discovered numerous such plumes, as well as evidence for the presence of gas and the movement of fluids beneath the seabed. What was unclear though was how the gas was escaping into the ocean.

The current expedition is led by the University of Southampton’s Professor Tim Minshull, who is based at the National Oceanography Centre, Southampton. The shipboard team – which includes scientists from the National Oceanography Centre Southampton, its French counterpart, the French Research Institute for Exploration of the Sea (Ifremer) and the University of Tromsoe in Norway – used a range of new technologies to probe the seabed beneath areas where methane gas was found to be escaping, due partly to recent warming of the ocean.

Ifremer’s SYSIF sonar system produced detailed images reaching 100 to 200 meters beneath the seafloor, which show how gas is in some places trapped and in some places is traveling upwards through narrow fractures and pipes to the seafloor. A seismic system towed across the sea surface provided images of deeper gas pockets beyond the reach of the towed sonar.

Professor Minshull, who is Head of Ocean and Earth Science at the University of Southampton, said: “Methane gas escaping from the Arctic seabed might make an important contribution to global climate change, but we need to understand the origin of this gas and its escape route to work out how the amount of gas escaping might change as the ocean warms. We now have very clear images of the gas escape routes and also of many places where gas is trapped and not yet escaping.”

Some of the team will return next summer to work with an electromagnetic sounding system that will allow better estimates to be made of the amount of methane stored beneath the seabed in this sensitive area.

The work forms part of an international effort involving scientists in Britain, France, Germany and Norway that has brought research vessels to the same small area every year since 2008, including two vessels in 2011. The expedition was one of two in this area this year funded by the Natural Environment Research Council.

Geophysicists to develop computer simulations of earthquake fault systems

James Dieterich is a distinguished professor of geophysics at UC Riverside. -  UCR Strategic Communications.
James Dieterich is a distinguished professor of geophysics at UC Riverside. – UCR Strategic Communications.

Geophysicists at the University of California, Riverside have received a $4.6 million grant from the National Science Foundation to study the dynamics of earthquake fault systems. Such systems occur where the world’s tectonic plates meet, and control the occurrence and characteristics of the earthquakes they generate.

The UC Riverside-led team will develop and use large-scale computer simulations to investigate these systems, and will focus first on the North American plate boundary and the San Andreas fault system of Northern and Southern California. The simulations can be performed, however, for any earthquake-prone region on Earth.

“Observations of earthquakes go back to only about 100 years, resulting in a relatively short record,” said James Dieterich, a distinguished professor of geophysics in the Department of Earth Sciences and the five-year grant’s principal investigator. “If we get the physics right, our simulations of plate boundary fault systems – at 1-kilometer resolution for California – will span more than 10,000 years of plate motion and consist of up to a million discrete earthquake events, giving us abundant data to analyze.”

Dieterich, a member of the National Academy of Sciences, explained that his simulations will provide the means to integrate a wide range of observations from seismology and earthquake geology into a common framework. In particular, the fault system models will integrate advanced ground motion simulations to better characterize the magnitude and variability of ground shaking in damaging earthquakes.

“A computer model of the kind we are developing is an excellent experimental tool for understanding how fault systems organize themselves, how earthquake stresses build up in the Earth,” he said. “The simulations will help us better understand the interactions that give rise to observable effects. They are computationally fast and efficient, and one of the project goals is to improve our short- and long-term earthquake forecasting capabilities. More accurate forecasting has practical advantages – earthquake insurance, for example, relies heavily on forecasts. More important, better forecasting can save more lives.”

Dieterich and colleagues also will study in detail the long-term processes that condition fault systems to fail in great earthquakes (larger than 8 on the Richter scale). An increasing fraction of the world’s population lives in regions where great earthquakes occur – or could occur – and is exposed to high seismic risk as a result. Great earthquakes, such as the 1906 earthquake in San Francisco and the one off the coast of Japan earlier this year, occur every 300-500 years.

Dieterich is an internationally renowned authority in rock mechanics, seismology and volcanology. His research has led to a new understanding of the Earth’s crust. He is the recipient on numerous awards including the Bucher Medal from the American Geophysical Union; and the Distinguished Service Award from the US Department of Interior. He is a fellow of the American Geophysical Union.

He will be joined in the research project by researchers at UCR, Brown University, Columbia University, the University of Southern California, San Diego State University, UC San Diego and the US Geological Survey. The UCR researchers are David Oglesby, an associate professor of geophysics; Elizabeth Cochran, an assistant adjunct professor; Keith Richards-Dinger, an assistant researcher; and graduate students.

Journey to the lower mantle and back

The theory of plate tectonics is at the center of our understanding of how the Earth works. It has been known for decades that new crust is formed at mid-ocean ridges and that this crust is subducted as plates dive underneath other plates in regions such as the Pacific Ring of Fire and descend into the Earth’s mantle. What is not so well known is the fate of these subducted plates.

In this week’s edition of the journal Science, scientists from the University of Bristol (Prof. M. Walter, Dr. S. Kohn, Dr. G. Bulanova, Mr. C. Smith), Universidade de Brasilia (Prof. D. Araujo), and the Carnegie Institution of Washington (Dr. E. Gaillou, Dr. J. Wang, Dr. A. Steele, Dr. S. Shirey), show that oceanic crust can make its way right down to the lower mantle (deeper than 660km) and then be transported back to the surface.

The samples studied are tiny inclusions of minerals trapped in diamonds from the Juina region of Brazil. Diamonds are extremely durable, and so they make excellent hosts for the trapped minerals they contain. However, the original minerals can change as the pressure and temperature conditions of the diamond change, and the inclusions record that history.

Walter and coworkers discovered, for the first time, a set of mineral inclusions with compositions matching the entire mineral assemblage characteristic of oceanic crust subducted into the lower mantle (depth > ~ 700 km). Trapped originally as single mineral phases, the inclusions become multi-mineral assemblages upon uplift. The authors suggest that the diamonds were transported from the lower to upper mantle via large-scale upwelling beneath Brazil during the Cretaceous Era, possibly in a mantle plume. The diamonds were ultimately exhumed rapidly to the surface in kimberlite magmas (kimberlites are the main volcanic rock to transport diamonds to the surface).

The authors also observe that four of the six diamonds studied have extremely low amounts of 13C, a feature never previously seen in diamonds from the lower mantle. Low 13C is consistent with an origin of the carbon in oceanic crust at the Earth’s surface. These and future results from investigations of diamonds and their inclusions could transform our understanding of the oxidation state, volatile content, and geological history of the lower mantle. They certainly mean that recycling of crustal materials, including carbon, is not limited to the upper mantle but extends deeper into the lower mantle.

Dr. Simon Kohn said “The amazing thing about the diamonds from Juina is that each new batch we study provides something unexpected. As we investigate them in more detail with new techniques they continue to give up more of their remarkable secrets.”

Prof. Michael Walter said “Inclusions in diamonds are fantastically useful for studying the inaccessible part of the deep Earth. It’s a bit like studying extinct insects in amber. Although we can’t extract DNA and grow dinosaurs, we can extract their chemical compositions and tell where they formed by growing minerals in the lab at extreme conditions!”

Prof Débora Araujo said “It is really exciting to see Brazilian diamonds playing such an important role in this scientific breakthrough. Samples from this region have been investigated for several years and yet we are not running out of exciting new discoveries. We are all very pleased to be involved in such a successful international collaboration”

Dr Steven Shirey said “I find it astonishing that we can use the tiniest of mineral grains to show some of the largest scale motions of the Earth’s mantle.”

Reinforcing gas hydrate strategy

Their critics weren’t convinced the first time, but Rice University researchers didn’t give up on the “ice that burns.”

A paper by a Rice team expands upon previous research to locate and quantify the amount of methane hydrates — a potentially vast source of energy — that may be trapped under the seabed by analyzing shallow core samples. The paper published this week by the Journal of Geophysical Research- Solid Earth should silence the skeptics, the researchers said.

Chemical engineers George Hirasaki and Walter Chapman and oceanographer Gerald Dickens headed the team.

In 2007, Hirasaki and former graduate student Gaurav Bhatnagar theorized that gas hydrates — methane that freezes at low temperatures and high pressures — could be detected via transition zones 10 to 30 meters below the seafloor near continental shores; at that level, sulfate (a primary component of seawater) and methane react and consume each other.

As sulfate migrates deeper into the sediment below the seafloor, it decreases in concentration, as evidenced by measurements of pore water (water trapped between sediment particles) from core samples. The depth at which the sulfate in pore water gets completely consumed upon contact with methane rising from below is the sulfate-methane transition (SMT) zone.

In the 2007 paper, Bhatnagar argued the depth of this transition zone serves as a proxy for quantifying the amount of gas hydrates that lie beneath; the shallower the SMT, the more likely methane will be found in the form of hydrates in abundance at greater depth.

Though hydrates may be as deep as 500 meters below the seafloor, locating deposits through shallow coring using such proxies should aid selection of deep, expensive exploratory drilling sites, the researchers said.

The controversy that followed the publication of the original paper focused on sulfate consumption processes in shallow sediment and whether methane or organic carbon was responsible. Skeptics felt the basis of Bhatnagar’s model, which assumes methane is a dominant consumer of pore-water sulfate, was not typical at most sites.

“They believed that particulate organic carbon (primarily from ocean-borne dead matter) was responsible for reducing sulfate,” said Sayantan Chatterjee, lead author of the new paper. “According to their assumption, the depth of the SMT, upward methane flux and hydrate occurrence cannot be related. That would nullify all that we have done.”

So Chatterjee, a fifth-year graduate student in Hirasaki’s lab, set out to prove the theory by bringing more chemical hitchhikers into the mix.

“In addition to methane and sulfate profiles, I added bicarbonate, calcium and carbon isotope profiles of bicarbonate and methane to the model,” Chatterjee said. “Those four additional components gave us a far more complete story.”

By including a host of additional reactions in their calculations on core samples from the coastline of Oregon and the Gulf of Mexico, “we can give a much stronger argument to say that methane flux from below is responsible for the SMT,” said Hirasaki, Rice’s A.J. Hartsook Professor of Chemical and Biomolecular Engineering. “The big picture gives more evidence of what’s happening, and it weighs toward the methane/sulfate reaction and not the particulate organic carbon.”

The work is important not only for a natural gas industry eyeing an energy resource estimated to outweigh the world’s oil, gas and coal reserves — as much as 20 trillion tons — but also for environmental scientists who see methane as the mother of all greenhouse gases, Hirasaki said.

“There’s a hypothesis by Dickens that says if the ocean temperature starts changing, the stability of the hydrate changes. And instability of the hydrates can release methane, a more severe greenhouse gas than carbon dioxide.

“That can create more warming, which then feeds back on itself,” Hirasaki said. “It can have a cascade effect, which is an implication for global climate change.”

Chatterjee had the chance to discuss his results with his peers in July at the seventh International Conference on Gas Hydrates in Edinburgh, Scotland, where he presented a related paper that focused on the accumulation of hydrates in heterogeneous submarine sediment.

Chatterjee said a number of eminent experts commended him after his talk. “I got a chance to show my recent findings on our 2-D model. This will simplify the search and locate isolated pockets where hydrates have accumulated in deep ocean sediments,” he said.

Chatterjee’s conference paper was awarded a first prize at the prestigious Society of Petroleum Engineers’ Young Professionals meeting and second at the Gulf Coast Regional student paper competition.

Co-authors include Chapman, the William W. Akers Professor of Chemical Engineering; Brandon Dugan, an assistant professor of Earth science; Glen Snyder, a research scientist in Earth science; Dickens, a professor of Earth science, and Bhatnagar, all of Rice.