Climate change could dramatically affect water supplies

It’s no simple matter to figure out how regional changes in precipitation, expected to result from global climate change, may affect water supplies. Now, a new analysis led by MIT researchers has found that the changes in groundwater may actually be much greater than the precipitation changes themselves.

For example, in places where annual rainfall may increase by 20 percent as a result of climate change, the groundwater might increase as much as 40 percent. Conversely, the analysis showed in some cases just a 20 percent decrease in rainfall could lead to a 70 percent decrease in the recharging of local aquifers – a potentially devastating blow in semi-arid and arid regions.

But the exact effects depend on a complex mix of factors, the study found – including soil type, vegetation, and the exact timing and duration of rainfall events – so detailed studies will be required for each local region in order to predict the possible range of outcomes.

The research was conducted by Gene-Hua Crystal Ng, now a postdoctoral researcher in MIT’s Department of Civil and Environmental Engineering (CEE), along with King Bhumipol Professor Dennis McLaughlin and Bacardi Stockholm Water Foundations Professor Dara Entekhabi, both of CEE, and Bridget Scanlon, a senior researcher at the University of Texas. The results are being presented Wednesday, Dec. 17, at the American Geophysical Union’s fall meeting in San Francisco.

The analysis combines computer modeling and natural chloride tracer data to determine how precipitation, soil properties, and vegetation affect the transport of water from the surface to the aquifers below. This analysis focused on a specific semi-arid region near Lubbock, Texas, in the southern High Plains.

Predictions of the kinds and magnitudes of precipitation changes that may occur as the planet warms are included in the reports by the Intergovernmental Panel on Climate Change (IPCC), and are expressed as ranges of possible outcomes. “Because there is so much uncertainty, we wanted to be able to bracket” the expected impact on water supplies under the diverse climate projections, Ng says.

“What we found was very interesting,” Ng says. “It looks like the changes in recharge could be even greater than the changes in climate. For a given percentage change in precipitation, we’re getting even greater changes in recharge rates.”

Among the most important factors, the team found, is the timing and duration of the precipitation. For example, it makes a big difference whether it comes in a few large rainstorms or many smaller ones, and whether most of the rainfall occurs in winter or summer. “Changes in precipitation are often reported as annual changes, but what affects recharge is when the precipitation happens, and how it compares to the growing season,” she says.

The team presented the results as a range of probabilities, quantifying as much as possible “what we do and don’t know” about the future climate and land-surface conditions, Ng says. “For each prediction of climate change, we get a distribution of possible recharge values.”

If most of the rain falls while plants are growing, much of the water may be absorbed by the vegetation and released back into the atmosphere through transpiration, so very little percolates down to the aquifer. Similarly, it makes a big difference whether an overall increase in rainfall comes in the form of harder rainfalls, or more frequent small rainfalls. More frequent small rainstorms may be mostly soaked up by plants, whereas a few more intense events may be more likely to saturate the soil and increase the recharging effect.

“It’s tempting to say that a doubling of the precipitation will lead to a doubling of the recharge rate,” Ng says, “but when you look at how it’s going to impact a given area, it gets more and more complicated. The results were startling.”

Some climate impacts happening faster than anticipated

A report released today at the annual meeting of the American Geophysical Union provides new insights on the potential for abrupt climate change and the effects it could have on the United States, identifying key concerns that include faster-than-expected loss of sea ice, rising sea levels and a possibly permanent state of drought in the American Southwest.

The analysis is one of 21 of its type developed by a number of academic and government agency researchers for the U.S. Climate Change Science Program. The work incorporates the latest scientific data more than any previous reports, experts say, including the 2007 Intergovernmental Panel on Climate Change.

While concluding that some projections of the impact of climate change have actually been too conservative – as in the case of glacier and ice sheets that are moving and decaying faster than predicted – others may not pose as immediate a threat as some scenarios had projected, such as the rapid releases of methane or dramatic shifts in the ocean current patterns that help keep Europe warm.

“We simulate the future changes with our climate models, but those models have not always incorporated some of our latest data and observations,” said Peter Clark, a professor of geosciences at Oregon State University and a lead author on the report. “We now have data on glaciers moving faster, ice shelves collapsing and other climate trends emerging that allow us to improve the accuracy of some of our future projections.”

Some of the changes that now appear both more immediate and more certain, the report concludes, are rapid changes at the edges of the Greenland and West Antarctic ice sheets, loss of sea ice that exceeds projections by earlier models, and hydroclimatic changes over North America and the global subtropics that will likely intensify and persist due to future greenhouse warming.

“Our report finds that drying is likely to extend poleward into the American West, increasing the likelihood of severe and persistent drought there in the future,” Clark said. “If the models are accurate, it appears this has already begun. The possibility that the Southwest may be entering a permanent drought state is not yet widely appreciated.”

Climate change, experts say, has happened repeatedly in Earth’s history and is generally believed to be very slow and take place over hundreds or thousands of years. However, at times in the past, climate has also changed surprisingly quickly, on the order of decades.

“Abrupt climate change presents potential risks for society that are poorly understood,” researchers wrote in the report.

This study, in particular, looked at four mechanisms for abrupt climate change that have taken place prehistorically, and evaluated the level of risks they pose today. These mechanisms are rapid changes in glaciers, ice sheets and sea level; widespread changes to the hydrologic cycle; abrupt changes in the “Atlantic Meridional Overturning Circulation,” or AMOC, an ocean current pattern; and rapid release to the atmosphere of methane trapped in permafrost or on continental margins.

Considering those mechanisms, the report concluded:

  • Recent rapid changes at the edges of the Greenland and West Antarctic ice sheets show acceleration of flow and thinning, with the speed of some glaciers more than doubling. These “changes in ice dynamics can occur far more rapidly than previously suspected,” the report said, and are not reflected in current climate models.
  • Inclusion of these changes in models will cause sea level rises that “substantially exceed” levels now projected for the end of this century, which are about two feet – but data are still inadequate to specify an exact level of rise.
  • Subtropical areas around the world, including the American West, are likely to become more arid in the future due to global warming, with an increasing likelihood of severe and persistent drought. These are “among the greatest natural hazards facing the United States and the globe today,” the report stated, and if models are correct, this has already begun.
  • The strength of “AMOC” ocean circulation patterns that help give Europe a much warmer climate than it would otherwise have may weaken by about 25-30 percent during this century due to greenhouse gas increases, but will probably not collapse altogether – although that possibility cannot be entirely excluded.
  • Climate change will accelerate the emissions of methane, a potent greenhouse gas, from both hydrate sources and wetlands, and they quite likely will double within a century – but a dramatic, potentially catastrophic release is very unlikely.

The “overarching” recommendation of the report is the need for committed and sustained monitoring of these climatic forces that could trigger abrupt climate change, the researchers concluded.

Better observing systems are needed, better forecasting of droughts should be developed, a more comprehensive understanding of the AMOC system is needed, and monitoring of methane levels should be maintained, among other needs.

Lifecycles of tropical cyclones predicted in global computer model

The initial results of the first computer model that simulates the global atmosphere with a detailed representation of individual clouds have been analyzed by a team of scientists at the International Pacific Research Center (IPRC) at the University of Hawai’i at Mānoa, Japan-Agency for Marine Earth Science and Technology (JAMSTEC), and the University of Tokyo.

The model, called the Nonhydrostatic ICosahedral Atmospheric Model (NICAM), was developed for the supercomputer Earth Simulator at JAMSTEC. Given the atmospheric conditions that were present 1-2 weeks before the observed cyclones formed, the model successfully reproduced the birth of two real tropical cyclones that formed in the Indian Ocean in December 2006 and January 2007.

The model captured the timing and location of the formation of the observed cyclones as well as their paths and overall evolution. “We attribute the successful simulation to the realistic representation of both the large-scale circulation and the embedded convective vortices and their merging,” says Hironori Fudeyasu, lead author of the study and IPRC postdoctoral fellow.

Atmospheric computer models with sufficient detail to represent clouds have greatly added to an understanding of local and regional climate, but huge computational needs in the past have allowed these models to be run only for small areas. “The high temporal and spatial resolution datasets provided by NICAM in this and future simulations will allow detailed studies of tropical cyclone genesis and evolution, as well as other weather and climate-related phenomena,” says co-author Yuqing Wang, UH meteorology professor and IPRC research team leader. He believes the results will usher in a new era in weather and climate prediction.

To improve forecasting earthquakes, mathematician studies grains

A four-year, $378,603 National Science Foundation grant has been awarded to Louis Kondic, associate professor of mathematical sciences at New Jersey Institute of Technology. -  New Jersey Institute of Technology
A four-year, $378,603 National Science Foundation grant has been awarded to Louis Kondic, associate professor of mathematical sciences at New Jersey Institute of Technology. – New Jersey Institute of Technology

A new and better way to predict earthquakes and avalanches may soon be available to forecasters thanks to mathematical research underway at NJIT. Using mathematical modeling, researchers are investigating how forces and pressures propagate through granular materials.

“Computational Homology, Jamming and Force Chains in Dense Granular Flows,” a four-year, $378,603 National Science Foundation grant has been awarded to Louis Kondic, associate professor of mathematical sciences at NJIT. Kondic will study how the physical properties of granular materials, like sand or salt, can lead to jamming, large force fluctuations and ultimately how they can pressure a building to topple. Both earthquakes and avalanches involve similar materials and reactions.

“The mystery is to learn how forces and pressure propagate or move through grains,” said Kondic. “We know the answer for liquids, but for granular materials, we do not. As a result, it is difficult to build efficient devices for dealing with them. Silos can collapse due to non-uniform pressures on their walls. Salt, sand or coal often jams when flowing out of hoppers. But why they behave like this remains unknown.”

2006, Kondic was the co-author of “On Velocity Profiles and Stresses in Sheared and Vibrated Granular Systems Under Variable Gravity” which appeared in Physics of Fluids. Other articles by him investigating similar research have appeared in Applied Mathematics and Mechanics (2008), SIAM News (2007) and Physics Review E (2005). To view Louis Kondic’s bio, please visit this link http://www.njit.edu/publicinfo/newsroom/kondic_bio.php.

(ATTENTION EDITORS: To receive copies of the articles or to interview Kondic, call Sheryl Weinstein, 973-596-3436.)

The current project centers on so-called force chains, which are crucial for understanding granular systems. The attached figure shows computer simulations of heterogeneous, ramified structures (colored yellow). “Similar forces do not propagate uniformly, but instead form chain-like structures,” said Kondic. “We will propose new mathematical methods for quantifying these structures. The algorithms will account for the geometrical properties of the forces. Such a generalized model that describes the properties of these features does not exist.”

According to Kondic, the research applies to earthquakes and avalanches because when tectonic plates move, they can cause an earthquake. Where the points of these plates meet, the material will typically be in a granular form. Researchers now believe that a better understanding of the forces that exist in this granular state can lead to new methods for predicting when and where earthquakes and/or avalanches will occur.

This project will employ a highly interdisciplinary approach that integrates new geometrical techniques, modeling, and experiments. It will address fundamental questions concerning the physical properties of granular media and other jammed materials such as glasses, foams, and colloids.

Although the existence of force chains has been known for decades, a quantitative understanding of their role in physical processes has proved to be elusive because previous studies have been unable to devise an unbiased and general definition for them. Precise identification and characterization of force chains and the response of jammed materials to applied forces will likely have a transformative impact in many arenas.

The NJIT study is part of a larger NSF project involving Robert P. Behringer, professor of physics, Duke University; Konstantin Mischaikow, professor, department of mathematics, Rutgers University-New Brunswick; Corey O’Hern, associate professor, departments of mechanical engineering and physics, Yale University.

New ‘seawater’ — the way ahead for ocean science

Dr. Trevor McDougall (left), who leads the project defining 'seawater,' and research project colleague Dr. David Jackett are pictured. -  CSIRO
Dr. Trevor McDougall (left), who leads the project defining ‘seawater,’ and research project colleague Dr. David Jackett are pictured. – CSIRO

The science case for a change in the definition of seawater was first agreed to in 2006 when the international guiding body, the Scientific Committee on Oceans Research (SCOR) established a working group, chaired by Dr Trevor McDougall, of CSIRO’s Wealth from Oceans Flagship.

“The changes are important because variations of salinity and temperature are responsible for driving deep ocean currents and the major vertical overturning circulations of the world’s oceans,” Dr McDougall says. “Getting these circulations right is central to the task of quantifying the ocean’s role in climate change.”

“We feel we are sufficiently well-advanced with our arguments to now go out to the oceanographic community and propose adoption of new and more accurate oceanographic variables that we suggest be called ‘Absolute Salinity’, and ‘Conservative Temperature’.” These more accurate variables will take the place of today’s Practical Salinity and Potential Temperature.

He says the new description of seawater is the result of many years of research into ocean energy and the properties of seawater. This work was mainly done in Germany (Dr Rainer Feistel), the US (Dr Frank Millero) and Australia.

Dr McDougall said the new definition allows, for the first time, an accurate measure of the heat content of seawater for inclusion in ocean models and climate projections.

“To date, ocean models assume that the heat content of seawater is proportional to a particular temperature variable called “potential temperature”. The new description of seawater allows us to measure the errors involved by using this approximation while presenting a much more accurate measure of the heat content of seawater, namely Conservative Temperature. The difference is mostly less than 1ยบ C at the sea surface, but it is important to correct for these biases in ocean models.”

Sea water is a mixture of 96.5 per cent pure water and 3.5 per cent other material, such as salts, dissolved gases, organic substances, and undissolved particles. Salinity, comprising the salts washed from rocks, is measured using the conductivity of seawater. This technique assumes that the composition of seawater is the same in all the world’s oceans. It has been known for some time that there are small variations in the composition of seawater around the globe, and the SCOR working group is now in a position to recommend a practical method for taking these variations into account. The changes in salinity, while small, are a factor of about ten larger than the accuracy with which scientists can measure salinity at sea.

Dr McDougall believes the new values for salinity will be in widespread use by 2010.

Abrupt climate change: United States report findings

The United States faces the potential for abrupt climate change in the 21st century that could pose clear risks to society in terms of our ability to adapt.

“Abrupt” changes can occur over decades or less, persist for decades more, and cause substantial disruptions to human and natural systems.

A new report, based on an assessment of published science literature, makes the following conclusions about the potential for abrupt climate changes from global warming during this century.

Climate model simulations and observations suggest that rapid and sustained September arctic sea ice loss is likely in the 21st century.

The southwestern United States may be beginning an abrupt period of increased drought.

It is very likely that the northward flow of warm water in the upper layers of the Atlantic Ocean, which has an important impact on the global climate system, will decrease by approximately 25 percent. However, it is very unlikely that this circulation will collapse or that the weakening will occur abruptly during the 21st century and beyond

An abrupt change in sea level is possible, but predictions are highly uncertain due to shortcomings in existing climate models.

There is unlikely to be an abrupt release of methane, a powerful greenhouse gas, to the atmosphere from deposits in the earth. However, it is very likely that the pace of methane emissions will increase.

The U.S. Geological Survey led the new assessment, which was authored by a team of climate scientists from the federal government and academia. The report was commissioned by the U.S. Climate Change Science Program with contributions from the National Oceanic and Atmospheric Administration and the National Science Foundation.

“This report was truly a collaborative effort between world renowned scientists who provided objective, unbiased information that is necessary to develop effective adaptation and mitigation strategies that protect our livelihood,” said USGS Director Mark Myers. “It summarizes the scientific community’s growing understanding regarding the potential for abrupt climate changes and identifies areas for additional research to further improve climate models.”

Further research is needed to improve our understanding of the potential for abrupt changes in climate. For example, the report’s scientists found that processes such as interaction of warm ocean waters with the periphery of ice sheets and ice shelves have a greater impact than previously known on the destabilization of ice sheets that might accelerate sea-level rise.

No quick or easy technological fix for climate change, researchers say

Global warming, some have argued, can be reversed with a large-scale “geoengineering” fix, such as having a giant blimp spray liquefied sulfur dioxide in the stratosphere or building tens of millions of chemical filter systems in the atmosphere to filter out carbon dioxide.

But Richard Turco, a professor in the UCLA Department of Atmospheric and Oceanic Sciences and a member and founding director of UCLA’s Institute of the Environment, sees no evidence that such technological alterations of the climate system would be as quick or easy as their proponents claim and says many of them wouldn’t work at all.

Turco will present his new research on geoengineering – conducted with colleague Fangqun Yu, a research professor at the State University of New York-Albany’s atmospheric sciences research center – today and Thursday at the American Geophysical Union’s annual meeting in San Francisco.

“We’re talking about tinkering with the climate system that affects everybody on Earth,” said Turco, an atmospheric chemist with expertise in the microphysics of fine particles suspended in the atmosphere. “Some of the ideas are extreme. There would certainly be winners and losers, but no one would know who until it’s too late.

“If people are going to pursue geoengineering, they have to realize that it won’t be quick, cheap or easy; indeed, suggestions that it might be are utter nonsense, and possibly irresponsible. Many of these ideas would require massive infrastructure and manpower commitments. For example, one concept to deliver reflective particles to the upper atmosphere on aircraft would require numerous airports, fleets of planes and a weather forecasting network dedicated only to this project. Its operation might be comparable to the world’s entire commercial flight industry. And even after that massive investment, the climatic response would be highly uncertain.”

Given the difficulties of reducing greenhouse gas emissions, the idea of a simple large-scale technological solution to climate change can seem very appealing.

“Global warming due to carbon dioxide emissions appears to be happening even faster than we expected,” Turco said. “Carbon dioxide emissions are continuing to grow despite all of the warnings about climate change, despite all of the data showing such change is occurring and despite all of the efforts to control carbon emissions. The emissions are rising, in part, because China and India are using increasingly more energy and because fossil fuels still represent the cheapest source of energy.

“If we continue down this path, the climate is likely to change dramatically – major ice sheets could melt, sea levels could rise, it may evolve into a climate catastrophe. So it is tempting to seek an alternative response to climate change in case we can’t get emissions under control. The result is that more and more geoengineering proposals are surfacing. Some of the people developing such proposals know what they’re talking about; many don’t.”

Turco and Yu have been studying a particular geoengineering approach that involves the injection of nanoparticles, or their precursor gases – such as sulfur dioxide or hydrogen sulfide – into the stratosphere from aircraft or large balloons.

While our climate system normally involves a balance between incoming sunlight and outgoing heat radiation, excess atmospheric greenhouse gases trap additional heat and cause the Earth’s temperature to rise, Turco noted. “One way to control the potential warming is to reduce the emissions of greenhouse gases,” he said. “We haven’t been able to get a handle on that. Another idea, instead of reducing emissions, is to somehow compensate for them.”

The idea of injecting sulfur dioxide or other toxic gases into the stratosphere in gaseous or liquefied form would mean that planes or balloons would have to fly as high as 13 miles – higher than any commercial aircraft can reach. And the amounts involved range to many millions of tons.

“Some of these proposals are preposterous, mind-boggling,” Turco said. “What happens, for example, when you spray liquefied sulfur dioxide into the stratosphere? Nobody knows.”

In a study published earlier this year, Turco analyzed what happens when a stream of very small particles is injected into the atmosphere. He showed that when the particles are first emitted, they are highly concentrated, collide frequently and coagulate to much larger sizes than expected.

“To create the desired climate outcomes, you would need to insert roughly 10 million tons of optimally-sized particles into the stratosphere,” he said. “You would have to disperse these particles very quickly over the entire stratosphere or they would coagulate into much larger sizes. At such enhanced sizes, the particles do not have the same effect; they’re much less effective in forcing climate compensation. In the end, you would have to fly thousands of high-altitude jets every day to get enough particles into the atmosphere to achieve your goal. And this activity would have to be sustained for hundreds of years.”

The basic idea behind stratospheric particle injections is that the Earth’s temperature depends on the reflectivity of the atmosphere. About one-third of the energy from the sun hitting the Earth is reflected back into space. That fraction is called the “albedo.” If the albedo increases, the average global temperature decreases because less energy is available to warm the planet. So if we can increase the albedo sufficiently, we can compensate for global warming.

“The size distribution of the particles is critical,” Turco said. “If the particles are too large, that will actually create a warming effect, a greenhouse warming. Small particles are not useful because they don’t reflect much radiation; you need something in between, and we have shown that is hard to achieve reliably.”

Turco and Yu have simulated, for the first time, the actual injection processes that might be used, focusing on the early evolution of the injection plumes created from aircraft or balloon platforms. They used an advanced computer model developed by Yu to calculate the detailed microphysical processes that ensue when reactive, particle-forming vapors are emitted into the atmosphere. They also accounted for the photochemical reactions of the injected vapors, as well as the mixing and dilution of the injection plume.

“We found that schemes to emit precursor gases in large quantities would be extremely difficult to design and implement within the constraints of a narrow tolerance for error, and in addition, the outcomes would be very sensitive to variables over which we would have little control, such as the stability and mixing conditions that occur locally,” Turco said.

“Advocates of geoengineering have tried to make climate engineering sound so simple,” he added. “It’s not simple at all. We now know that the properties and effects of a geoengineered particle layer in the stratosphere would be far more unpredictable, for example, than the physics of global warming associated with carbon dioxide emissions. Embarking on such a project could be foolhardy.”

How can global warming be combated?

“We must reduce carbon emissions,” Turco said. “We need to invest big-time in alternative energy sources with minimal carbon footprints.”

CAT scan reveals inner workings of volcano island

This image shows Soufriere Hills Volcano erupting. -  Barry Voight, Penn State
This image shows Soufriere Hills Volcano erupting. – Barry Voight, Penn State

On the ground and in the water, an international team of researchers has been collecting imaging data on the Soufriere Hills Volcano in Montserrat to understand the internal structure of the volcano and how and when it erupts.

“Using land-based measurement, we can see that over the time periods when the magma is erupting, the ground surface deflates into a bowl of subsidence and when the magma is sealed underground, the ground surface inflates like a balloon,” says Barry Voight, professor emeritus of geosciences, Penn State. “The interesting thing is that much more magma is erupting than appears represented by the subsiding bowl.”

Voight suggests a simple model to explain this discrepancy seen through the various eruptive phases and pauses of the volcano.

In 1995, Soufriere Hills volcano began the current series of eruptions and pauses, with each episode lasting from one to three years. The November 1995 event lasted until March 1998, during which time a thick dome of sticky andesite lava — a volcanic rock — grew continuously within the crater, punctuated by occasional and lethal explosions. From March 1998 until November 1999, there was a pause in above-ground volcanic activity and the lava dome collapsed from its own weight and inactivity.

Beginning in December 1999, the second eruptive episode continued until mid-July 2003 followed by a pause until October 2005. The third episode began then and ended in April 2007, followed by a pause, which still continues — although, according to Voight, “a series of explosions started just a few days ago (early December) and this might mark the onset of the next eruptive period. We will need to wait and see if continuous lava extrusion follows.”

The measurements taken during the on-going CALIPSO project, the ground-based phase of this study, uses Global Positioning Systems and strain meters to measure the exact up-and-down and sideways movements of numerous points over the volcano island. However, the volume changes represented by those measurements did not match measured volumes of the actual lava flows during the various eruption episodes, raising an intriguing puzzle.

The SEA CALIPSO project, involving a research consortium directed by Voight and S. Sparks, professor, earth sciences, University of Bristol, UK, used seismic waves caused by underwater air gun explosions at sea to map inside and under the volcano island in the same way as images inside the human body are revealed by a hospital CAT scan.

“In SEA-CALIPSO, we are using a variety of research tools to image the internal structure of the Earth’s crust under the volcano island,” says Voight. “Our knowledge of the deeper structure under any of the Caribbean Islands is very limited and the internal structure of an active volcano is one of the most puzzling questions in the Earth sciences. It is nearly impossible to get direct measurements inside the volcano, so we rely largely on remote sensing methods

The researchers used seismic wave arrivals at over 200 land and sea floor seismometers to give CAT-scan like images of structure to about 5 miles deep. They were also able to map how the seismic energy bounces off key reflecting layers near the crust-mantle boundary, around 20 miles down. The basalt at those depths forms horizontal layers that partly crystallize and generate residual melts enriched in silica, water and sulfur. These melts rise in pulses to shallower levels, where they define magma chambers of andesite composition – the lava now erupting on Montserrat.

The researchers are able to image the location of these chambers by their pressure centers, which are approximately 6 miles deep and defined by continuously measured GPS surface stations.

Reporting in three sessions beginning today (Dec. 19), at the American Geophysical Union Conference in San Francisco, CALIPSO researchers discussed many aspects of the project. Voight’s model of the Soufriere Hills Volcano accounts for the volume mismatch in erupted magma and ground movement by suggesting an elongated magma chamber beginning below 3 miles and centered about 6 miles beneath the mountain. This chamber fills with magma, but the magma already in the chamber is rich in water, carbon dioxide and sulfur dioxide gases, making it very compressible.

As the chamber fills, part of the new magma pushes against the chamber walls, elevating the island surface, as detected by GPS; but most of the magma fits into the existing space by squeezing the bubbly resident magma. When the volcano erupts, the magma stuffed into the chamber decompresses and the amount of magma erupted is greater than the amount implied by ground subsidence.

“The magma volume in Montserrat eruptions is much larger than anyone would estimate from the surface deformation, because of the elastic storage of magma in what is effectively a huge magma sponge,” says Voight. “Magma is continually fed into the chamber from below at a rate of about two cubic meters per second — about the volume of a large refrigerator every second.”

In the long term, the magma released in the eruptive periods is approximately balanced by the accumulated input during the eruptive episode and the preceding inflation. There is no evident depletion of the chamber, so the eruption could be long lasting

Abrupt climate shifts may move faster than thought

The United States could suffer the effects of abrupt climate changes within decades-sooner than some previously thought–says a new government report. It contends that seas could rise rapidly if melting of polar ice continues to outrun recent projections, and that an ongoing drought in the U.S. west could be the start of permanent drying for the region. Commissioned by the U.S. Climate Change Science Program, the report was authored by experts from the U.S. Geological Survey, Columbia University’s Lamont-Doherty Earth Observatory and other leading institutions. It was released at this week’s meeting of the American Geophysical Union.

Many scientists are now raising the possibility that abrupt, catastrophic switches in natural systems may punctuate the steady rise in global temperatures now underway. However, the likelihood and timing of such “tipping points,” where large systems move into radically new states, has been controversial. The new report synthesizes the latest published evidence on four specific threats for the 21st century. It uses studies not available to the Intergovernmental Panel on Climate Change (IPCC), whose widely cited 2007 report explored similar questions. “This is the most up to date, as it includes research that came out after IPCC assembled its data,” said Edward Cook, a climatologist at Lamont-Doherty and a lead author of the new study.

The researchers say the IPCC’s maximum estimate of two feet of sea level rise by 2100 may be exceeded, because new data shows that melting of polar ice sheets is accelerating. Among other things, there is now good evidence that the Antarctic ice cap is losing overall mass. At the time of the IPCC report, scientists were uncertain whether collapses of ice shelves into the ocean off the western Antarctica were being offset by snow accumulation in the continent’s interior. But one coauthor, remote-sensing specialist Eric Rignot of the Jet Propulsion Laboratory, told a press conference at the meeting: “There is a new consensus that Antarctica is losing mass.” Seaward flow of ice from Greenland is also accelerating. However, projections of how far sea levels might rise are “highly uncertain,” says the report, as researchers cannot say whether such losses will continue at the same rates.

In the interior United States, a widespread drought that began in the Southwest about 6 years ago could be the leading edge of a new climate regime for a wider region. Cook, who heads Lamont’s Tree Ring Lab, says that periodic droughts over the past 1,000 years have been driven by natural cycles in air circulation, and that these cycles appear to be made more intense and persistent by warming. Among the new research cited is a 2007 Science paper by Lamont climate modeler Richard Seager, showing how changes in temperature over the Pacific have driven large-scale droughts across western North America. “We have no smoking gun saying that humans are causing the current changes. But the past is a cautionary tale,” Cook told the press conference. “What this tells us is that the system has the ability to lock into periods of profound, long-lasting aridity. And there is the suggestion that these changes are related to warmer climate.” Cook added: “If the system tips over, that would have catastrophic effects no human activities and populations over wide areas.”

The panel said two other systemic changes seem less imminent, but are still of concern. Vast quantities of methane, a potent greenhouse gas, have long been locked up in ocean sediments, wetlands and permafrost. These could be destabilized by climate change, leading to blowouts of gas, and thus even more abrupt temperature shifts. The panel said blowouts appear unlikely in the next 100 years-but that steady emissions could double, especially in the north, as land and water warm up. The panel also looked at the continuous circulation of the Atlantic Ocean, which sends warm water northward and cold water southward, controlling the climate of western Europe and beyond. Some scientists say this circulation could collapse if enough northern ice melts and dilutes the salty water. The panel found this scenario unlikely in the short term, but warned that the circulation’s strength might decline 25% to 30% by 2100.

“Abrupt climate change presents potential risks for society that are poorly understood,” the researchers write. [There is an] urgent need for committed and sustained monitoring of those components [that] are particularly vulnerable.”

Professor ‘follows the elements’ to understand evolution in ancient oceans

In the search for life beyond Earth, scientists ‘follow the water’ to find places that might be hospitable. However, every home gardener knows that plants need more than water, or even sunshine. They also need fertilizer – a mixture of chemical elements that are the building blocks of the molecules of life. Scientists at Arizona State University are studying how the distribution of these elements on Earth – or beyond – shapes the distribution of life, the state of the environment and the course of evolution.

Ariel Anbar, a professor in ASU’s Department of Chemistry and Biochemistry and the School of Earth and Space Exploration in the College of Liberal Arts and Sciences weaves together threads from geoscience, chemistry, biochemistry and biology in his article published in the Dec. 5 issue of Science. The “Perspectives” article reviews what we know about changes in the availability of some key nutrients in the oceans over the sweep of geologic time and suggests future directions for research.

“The history of our planet is like a natural laboratory of ‘alternative worlds,'” says Anbar. “The chemical composition of the oceans has changed dramatically over billions of years. Elements that are abundant today were once scarce, and elements that are scarce today were once abundant. So Earth’s ancient oceans are a good place to go if we want to understand how organisms and ecosystems evolve to cope with changing abundances of elements. Studying the ancient oceans also stretches our minds to imagine what we might find someday in alien oceans on other worlds.”

Visiting billion-year-old oceans is not so easy, however. Anbar explains that biogeochemists cannot directly sample oceans of the past but make inferences about their compositions by examining sedimentary rocks that were deposited on ancient sea floors. For example, the ocean floor rocks from the first half of Earth history include massive deposits of iron oxide – essentially, rust. Those rusty rocks tell us that the oceans in those days were rich in dissolved iron. Today, iron is so scarce in seawater that organisms living in vast areas of the oceans are literally starved for this biologically essential element. These organisms have evolved clever strategies to find and capture this key nutrient.

But Anbar stresses that iron is only one of many critical nutrient elements to consider. Sulfur, nitrogen, phosphorus, copper, zinc, nickel and even obscure elements like molybdenum are all essential nutrients whose abundances have gone up and down in the oceans over geological time. These changes are a consequence of increases in the amount of oxygen in the atmosphere and oceans.

Different elements are important in different ways for biological processes that affect the environment. As a result, Anbar says that changes in ocean chemistry probably had many unusual consequences in Earth history. For instance, he points to a suggestion made by a colleague, Professor Roger Buick of the University of Washington, that changes in the availability of copper could have affected the amount of the gas nitrous oxide – so-called ‘laughing gas’ – in the atmosphere. The idea follows from the fact that copper is present in the reaction center of the enzyme that bacteria use to convert nitrous oxide to ordinary nitrogen gas. Buick proposes that copper-poor oceans could have led to a ‘laughing gas’ atmosphere between 1.8 and 0.7 billion years ago. “Ironically, it’s no laughing matter,” says Anbar. “Nitrous oxide is a powerful greenhouse gas. It may be that copper scarcity helped keep the Earth warm at that time.”

Anbar is most excited by the possibility that changes in ocean chemistry affected the makeup of life itself. “Take iron, for example,” he contemplates. “It’s needed by virtually every organism on the planet. Is that because the basic biochemistry of life on Earth developed in the iron-rich oceans of Earth’s distant past? Or is it because the chemical properties of iron are so special that evolution would have selected for it even if it was always rare?”

The answers to such questions will come from continued study of the past combined with research into how the use of elements by organisms is affected by changes in element abundances in their environment. Much of this biological work will take place at ASU in a project Anbar is undertaking with Profs. James Elser and Susanne Neuer in the School of Life Sciences, Everett Shock in the School of Earth and Space Exploration and the Department of Chemistry and Biochemistry, and other ASU scientists. That effort is supported by a new, $7 M grant from the NASA Astrobiology Institute. “NASA is really interested in the idea that they should ‘follow the elements’ in addition to water when searching for life out there,” says Anbar. “They recognize that ASU is an exceptional place for such research.”