Melting threat from West Antarctic Ice Sheet may be less than expected, could hit US hardest

While a total or partial collapse of the West Antarctic Ice Sheet as a result of warming would not raise global sea levels as high as some predict, levels on the U.S. seaboards would rise 25 percent more than the global average and threaten cities like New York, Washington, D.C., and San Francisco, according to a new study.

Long thought of as the sleeping giant with respect to sea level rise, Antarctica holds about nine times the volume of ice of Greenland. Its western ice sheet, known as WAIS, is of particular interest to scientists due to its inherent instability, a result of large areas of the continent’s bedrock lying below sea level. But the ice sheet’s potential contribution to sea level rise has been greatly overestimated, according to new calculations.

“There’s a vast body of research that’s looked at the likelihood of a WAIS collapse and what implications such a catastrophic event would have for the globe,” said Jonathan Bamber, lead author of the study published in Science May 15. “But all of these studies have assumed a 5-meter to 6-meter contribution to sea level rise. Our calculations show those estimates are much too large, even on a thousand-year timescale.”

Bamber and his colleagues found a WAIS collapse would only raise sea levels by 3.3 meters, or about 11 feet. Bamber, a professor at the University of Bristol in England, currently is a visiting fellow at the University of Colorado at Boulder’s Cooperative Institute for Research in Environmental Sciences, or CIRES.

The study authors used models based on glaciological theory to simulate how the massive ice sheet likely would respond if the floating ice shelves fringing the continent broke free. Vast ice shelves currently block WAIS from spilling into the Weddell and Ross seas, limiting total ice loss to the ocean.

According to theory, if these floating ice shelves were removed, sizeable areas of WAIS would essentially become undammed, triggering an acceleration of the ice sheet toward the ocean and a rapid inland migration of the grounding line. The grounding line is the point where the ice sheet’s margins meet the ocean and begin to float.

The most unstable areas of WAIS are those sections sitting in enormous inland basins on bedrock entirely below sea level. If the ice filling these basins becomes undammed by the disappearance of floating ice shelves, it quickly would become buoyant and form new floating ice shelves further inland, in time precipitating further breakup and collapse, according to existing theories.

The study authors assumed that only ice on the downward-sloping and inland-facing side of the basins would be vulnerable to collapse. They also assumed that ice grounded on bedrock that slopes upward inland or on bedrock that lies above sea level likely would survive.

“Unlike the world’s other major ice sheets — the East Antarctic Ice Sheet and Greenland — WAIS is the only one with such an unstable configuration,” said Bamber.

Just how rapid the collapse of WAIS would be is largely unknown. If such a large mass of ice steadily melted over 500 years, as has been suggested in earlier studies, it would add about 6.5 millimeters or a quarter of an inch per year to sea level rise — about twice the current rate due to all sources.

“Interestingly, the pattern of sea level rise is independent of how fast or how much of the WAIS collapses,” he said. “Even if the WAIS contributed only a meter of sea level rise over many years, sea levels along North America’s shorelines would still increase 25 percent more than the global average,” said Bamber.

Regional variations in sea level would largely be driven by the distribution of ice mass from the Antarctic continent to the oceans, according to the study. With less mass at the South Pole, Earth’s gravity field would weaken in the Southern Hemisphere and strengthen in the Northern Hemisphere, causing water to pile up in the northern oceans.

This redistribution of mass also would affect Earth’s rotation, which in turn would cause water to build up along the North American continent and in the Indian Ocean.

Well-oiled research plans to dip into new reserves




A 3-D model showing oil and gas flow pathways and accumulations in the Gippsland Basin. The model helps DPI and CSIRO scientists understand the geological 'plumbing' of the region. -  CSIRO
A 3-D model showing oil and gas flow pathways and accumulations in the Gippsland Basin. The model helps DPI and CSIRO scientists understand the geological ‘plumbing’ of the region. – CSIRO

A new research partnership between CSIRO and the Victorian Department of Primary Industries (VicDPI) will delve deep into Victoria’s basins to unearth new oil and gas reserves.

The three year agreement aims to assist energy companies to more effectively explore for new oil and gas reserves, reduce exploration risk and encourage investment in Victoria.

It was signed by CSIRO Petroleum Resources, Deputy Chief, Dr David Whitford and Victorian Department of Primary Industries, Deputy Secretary, Richard Aldous.

CSIRO project leader Dr James Underschultz said CSIRO has the research expertise and laboratory facilities to evaluate all aspects of petroleum systems, from source rock to reservoir.

“CSIRO techniques will measure various properties of rock cores, organic mater, and formation fluids,” Dr Underschultz said.

“They will model the basins histories, including the generation, migration and trapping of oil and gas.

“This will improve the characterisation of Victoria’s sedimentary basins and the mechanisms that drive the petroleum systems, which could contribute to an increase in resource estimates, attracting industry to invest into the state.”

Victorian Minister for Energy and Resources, Peter Batchelor said that finding new reserves is a key challenge of national importance to the oil and gas industry and Australia’s energy security.

“Not only will the research benefit Victoria, but the advanced integrated technologies developed in the program can be applied to other basins throughout Australia,” Mr Batchelor said.

Our understanding of the potential for geological carbon dioxide storage and geothermal resources will also be boosted by information gathered from the research program.

Project leader for VicDPI, Dr Geoff O’Brien said VicDPI has expertise in characterising the geologic framework of sedimentary basins, in which petroleum systems may occur.

It also has an extensive dataset that will allow a 3D model of the State’s sedimentary basins to be built.

Dr Underschultz said the two organisations share complementary skills, expertise, facilities and background facilitating a more comprehensive petroleum systems analysis study.

The project is expected to be completed in 2011. Information will be released to the public through the VicDPI website as the research program progresses.

Natural petroleum seeps release equivalent of eight to 80 Exxon Valdez oil spills




There's an oil spill every day off the coast of Santa Barbara, Calif., where oil is seeping naturally from cracks in the seafloor into the ocean. Lighter than seawater, the oil floats to the surface. Some 20 to 25 tons of oil are emitted each day. (Photo by Dave Valentine, University of California, Santa Barbara)
There’s an oil spill every day off the coast of Santa Barbara, Calif., where oil is seeping naturally from cracks in the seafloor into the ocean. Lighter than seawater, the oil floats to the surface. Some 20 to 25 tons of oil are emitted each day. (Photo by Dave Valentine, University of California, Santa Barbara)

A new study by researchers at Woods Hole
Oceanographic Institution (WHOI) and the University of California, Santa Barbara (UCSB) is the first to quantify the amount of oil residue in seafloor sediments that result from natural petroleum seeps off Santa Barbara, California.

The new study shows the oil content of sediments is highest closest to the seeps and tails off with distance, creating an oil fallout shadow. It estimates the amount of oil in the sediments down current from the seeps to be the equivalent of approximately 8-80 Exxon Valdez oil spills.

The paper is being published in the May 15 issue of Environmental Science & Technology.

“Farwell developed and mapped out our plan for collecting sediment samples from the ocean floor,” said WHOI marine chemist Chris Reddy, referring to lead author Chris Farwell, at the time an undergraduate working with UCSB’s Dave Valentine. “After conducting the analysis of the samples, we were able to make some spectacular findings.”

There is an oil spill everyday at Coal Oil Point (COP), the natural seeps off Santa Barbara, California, where 20-25 tons of oil have leaked from the seafloor each day for the last several hundred thousand years.

Earlier research by Reddy and Valentine at the site found that microbes were capable of degrading a significant portion of the oil molecules as they traveled from the reservoir to the ocean bottom and that once the oil floated to sea surface, about 10 percent of the molecules evaporated within minutes.

“One of the natural questions is: What happens to all of this oil?” Valentine said. “So much oil seeps up and floats on the sea surface. It’s something we’ve long wondered. We know some of it will come ashore as tar balls, but it doesn’t stick around. And then there are the massive slicks. You can see them, sometimes extending 20 miles from the seeps. But what really is the ultimate fate?”

Based on their previous research, Valentine and Reddy surmised that the oil was sinking “because this oil is heavy to begin with,” Valentine said. “It’s a good bet that it ends up in the sediments because it’s not ending up on land. It’s not dissolving in ocean water, so it’s almost certain that it is ending up in the sediments.”

To conduct their sampling, the team used the research vessel Atlantis, the 274-foot ship that serves as the support vessel for the Alvin submersible.

“We were conducting research at the seeps using Alvin during the summer of 2007,” recalls Reddy. “One night during that two-week cruise, after the day’s Alvin dive was complete and its crew prepared the sub for the next day’s dive, Captain AD Colburn guided the Atlantis on an all-night sediment sampling campaign. It was no easy task for the crew of the Atlantis. We were operating at night, awfully close to land with a big ship where hazards are frequent. I tip my hat to Captain Colburn, his crew, and the shipboard technician for making this sampling effort so seamless.”

The research team sampled 16 locations in a 90 km2 (35 square mile) grid starting 4 km west of the active seeps. Sample stations were arranged in five longitudinal transects with three water depths (40, 60, and 80 m) for each transect, with one additional comparison sample obtained from within the seep field.

To be certain that the oil they measured in the sediments came from the natural seeps, Farwell worked in Reddy’s lab at WHOI using a comprehensive two-dimensional gas chromatograph (GC×GC), that allowed them to identify specific compounds in the oil, which can differ depending on where the oil originates.

“The instrument reveals distinct biomarkers or chemical fossils — like bones for an archeologist — present in the oil. These fossils were a perfect match for the oil from the reservoir, the oil collected leaking into the ocean bottom, oil on the sea surface, and oil back in the sediment. We could say with confidence that the oil we found in the sediments was genetically connected to the oil reservoir and not from an accidental spill or runoff from land.”

The oil that remained in the sediments represents what was not removed by “weathering” — dissolving into the water, evaporating into the air, or being degraded by microbes. Next steps for this research team involve investigating why microbes consume most, but not all, of the compounds in the oil.

“Nature does an amazing job acting on this oil but somehow the microbes stopped eating, leaving a small fraction of the compounds in the sediments,” said Reddy. “Why this happens is still a mystery, but we are getting closer.”

Cold water ocean circulation doesn’t work as expected

The familiar model of Atlantic ocean currents that shows a discrete “conveyor belt” of deep, cold water flowing southward from the Labrador Sea is probably all wet.

New research led by Duke University and the Woods Hole Oceanographic Institution relied on an armada of sophisticated floats to show that much of this water, originating in the sea between Newfoundland and Greenland, is diverted generally eastward by the time it flows as far south as Massachusetts. From there it disburses to the depths in complex ways that are difficult to follow.

A 50-year-old model of ocean currents had shown this southbound subsurface flow of cold water forming a continuous loop with the familiar northbound flow of warm water on the surface, called the Gulf Stream.

“Everybody always thought this deep flow operated like a conveyor belt, but what we are saying is that concept doesn’t hold anymore,” said Duke oceanographer Susan Lozier. “So it’s going to be more difficult to measure these climate change signals in the deep ocean.”

And since cold Labrador seawater is thought to influence and perhaps moderate human-caused climate change, this finding may affect the work of global warming forecasters.

“To learn more about how the cold deep waters spread, we will need to make more measurements in the deep ocean interior, not just close to the coast where we previously thought the cold water was confined,” said Woods Hole’s Amy Bower.

Lozier, a professor of physical oceanography at Duke’s Nicholas School of the Environment and Bower, a senior scientist in the department of physical oceanography at the Woods Hole Institution, are co-principal authors of a report on the findings to be published in the May 14 issue of the research journal Nature.

Their research was supported by the National Science Foundation.

Climatologists pay attention to the Labrador Sea because it is one of the starting points of a global circulation pattern that transports cold northern water south to make the tropics a little cooler and then returns warm water at the surface, via the Gulf Stream, to moderate temperatures of northern Europe.

Since forecasters say effects of global warming are magnified at higher latitudes, that makes the Labrador Sea an added focus of attention. Surface waters there absorb heat-trapping carbon dioxide from the atmosphere. And a substantial amount of that CO2 then gets pulled underwater where it is no longer available to warm Earth’s climate.

“We know that a good fraction of the human caused carbon dioxide released since the Industrial revolution is now in the deep North Atlantic” Lozier said. And going along for the ride are also climate-caused water temperature variations originating in the same Labrador Sea location.

The question is how do these climate change signals get spread further south? Oceanographers long thought all this Labrador seawater moved south along what is called the Deep Western Boundary Current (DWBC), which hugs the eastern North American continental shelf all the way to near Florida and then continues further south.

But studies in the 1990s using submersible floats that followed underwater currents “showed little evidence of southbound export of Labrador sea water within the Deep Western Boundary Current (DWBC),” said the new Nature report.

Scientists challenged those earlier studies, however, in part because the floats had to return to the surface to report their positions and observations to satellite receivers. That meant the floats’ data could have been “biased by upper ocean currents when they periodically ascended,” the report added.

To address those criticisms, Lozier and Bower launched 76 special Range and Fixing of Sound floats into the current south of the Labrador Sea between 2003 and 2006. Those “RAFOS” floats could stay submerged at 700 or 1,500 meters depth and still communicate their data for a range of about 1,000 kilometers using a network of special low frequency and amplitude seismic signals.

But only 8 percent of the RAFOS floats’ followed the conveyor belt of the Deep Western Boundary Current, according to the Nature report. About 75 percent of them “escaped” that coast-hugging deep underwater pathway and instead drifted into the open ocean by the time they rounded the southern tail of the Grand Banks.

Eight percent “is a remarkably low number in light of the expectation that the DWBC is the dominant pathway for Labrador Sea Water,” the researchers wrote.

Studies led by Lozier and other researchers had previously suggested cold northern waters might follow such “interior pathways” rather than the conveyor belt in route to subtropical regions of the North Atlantic. But “these float tracks offer the first evidence of the dominance of this pathway compared to the DWBC.”

Since the RAFOS float paths could only be tracked for two years, Lozier, her graduate student Stefan Gary, and German oceanographer Claus Boning also used a modeling program to simulate the launch and dispersal of more than 7,000 virtual “efloats” from the same starting point.

“That way we could send out many more floats than we can in real life, for a longer period of time,” Lozier said.

Subjecting those efloats to the same underwater dynamics as the real ones, the researchers then traced where they moved. “The spread of the model and the RAFOS float trajectories after two years is very similar,” they reported.

“The new float observations and simulated float trajectories provide evidence that the southward interior pathway is more important for the transport of Labrador Sea Water through the subtropics than the DWBC, contrary to previous thinking,” their report concluded.

“That means it is going to be more difficult to measure climate signals in the deep ocean,” Lozier said. “We thought we could just measure them in the Deep Western Boundary Current, but we really can’t.”

New Danish research shows how oil gets stuck underground

Now, new Danish research may have come up with an explanation as to where and how North Sea oil clings to underground rocks. This explanation could turn out to be the first step on the way to developing improved oil production techniques with the intent of increasing oil production from Danish oil fields.

A research group at the Nano-Science Center, part of the Institute of Chemistry at University of Copenhagen has investigated drill cores collected from North Sea oil fields using an atomic force microscope. Their investigations show that the spaces which contain oil have totally different surface qualities than expected from our knowledge of the minerals which make up the rock. The rocks which contain oil in the Danish part of the North Sea are primarily chalk – the same type of rock that the cliffs of Stevns and Møns in Denmark are made of. Assistant Professor Tue Hassenkam lead the research, whose preliminary results were published in the respected scientific publication PNAS (Proceedings of the National Academy of Sciences) this week. He says that this is the first time that investigations of this type have been carried out on chalk from an oil field in the North Sea.

“Previous investigations were carried out on the surface properties of pure mineral crystals. But our investigation has shown that this chalk has a different and more complex structure” says Tue Hassenkam.

The oil bearing layers in the subsurface are reminiscent of a sponge. The oil “hides” in tiny pores and gaps and only some of the oil can be pressed out of the chalk and into the borehole by injecting water into the chalk layer. The rest is left behind as small droplets of oil surrounded by water either in small gaps in the rock or stuck to the walls of the pores. The chalk particles ought to repel oil if they act like particles of the mineral calcite, which chalk is almost 100% made up of. However the new investigations, carried out with a particularly powerful microscope, have shown that the surfaces of the pores in the chalk are partially covered in a material which oil can stick to. Ass. Prof. Hassenkam believes that the surprising behaviour of the material in the surface of the chalk can be explained by studying how the chalk was formed.

“Chalk is actually the casings of ancient algae. The algae gave their cases a type of “surface coating” to make them resistant to water. And it is probably this surface coating that we can see in action here, even 60 million years later” according to Ass. Prof. Hassenkam.

If we can manage to squeeze even a few percent more oil out of the seabed under the North Sea it could be worth millions of kroner for Denmark. Therefore Mærsk Oil and Gas AS on behalf of DUC (Dansk Un-dergrunds Consortium) along with Danish National Advanced Technology Foundation are supporting a project being carried out by Professor Susan Stipps’ research group – the Nano-Chalk Venture, which has been ongoing for the last two years. Tue Hassenkam originally became interested in chalk because he found the algae casings so beautiful. Today, after a year’s work in front of a microscope, he is glad that his work also has a practical application. An understanding of how the oil clings to the chalk can possibly help develop a method to release it. And that will be the second part of the Nano-Chalk Venture.

Global monsoon drives long-term carbon cycles in the ocean

Monsoon is a global system, and many arrays of evidence indicate that it drives long-term cyclicity of the carbon reservoir in the global ocean. The new view is introduced in a substantial paper in Issue 7 (April 2009) of Chinese Science Bulletin.

For over 300 years, monsoon has been considered as a gigantic land-sea breeze of regional scale, but now it is considered as a global system over all continents but Antarctica. This new develoment in modern climatology, however, has not yet been responded by paleo-climatology.

Prof. Pinxian Wang from Tongji University, Shanghai, reviews the geological evolution of the global monsoon and its impact, showing that the global monsoon exists through all geological history since at least 600 million years ago. It covaries with various geological cycles including those caused by the geometric changes of the Earth’s orbits. The 20,000-year precessional cycle of the global monsoon, for example, is responsible for the collapse of several Asian and African ancient cultures at ~ 4000 years ago. The same cyclicity is seen in the chemical composition of the air, such as methane concentration and isotope composition of air-bubbles captured in ice cores.

Now Wang found that the long-term cycles in the oceanic carbon reservoir also has a global monsoon origin. This 400,000-year cyclicity related to “long eccentricity” of the Earth’s orbit, is best seen in carbon isotope compositions of calcite test of foraminifera, a single-cell animal in the ocean. The rhythmic changes in oceanic carbon reservoir were likened to “heartbeat” of the Earth system. This cyclicity becomes longer since 1.6 million years ago, displaying a kind of “arrhythmia” in the Earth system, probably resulting from the growth of the Arctic ice. Although the mechanism of how monsoon drives oceanic carbon cycle remains unclear, the monsoon-related long-term cyclicity should not be overlooked in carbon-cycle modeling for long-term climate prediction.

“It is an authoritative review”, said Prof. Andre Berger, University of Louvain, in his commentary, “and probably also the first in which the monsoon issues are reviewed in a global scale through a so long geological history?.I totally agree with Wang’s argumentation about paying more attention to the importance of the tropical forcing in modulating the Earth’s climate system”. The geological evolution of the global monsoon is a new topic attracting growing interest from both modern and paleo-climatologic communities. An international symposium on global monsoon was organized by the PAGES (Past Global Changes) project in Shanghai in 2008, and the next symposium is scheduled in 2010.

The rise of oxygen caused Earth’s earliest ice age

Geologists may have uncovered the answer to an age-old question – an ice-age-old question, that is. It appears that Earth’s earliest ice ages may have been due to the rise of oxygen in Earth’s atmosphere, which consumed atmospheric greenhouse gases and chilled the earth.

Alan J. Kaufman, professor of geology at the University of Maryland, Maryland geology colleague James Farquhar, and a team of scientists from Germany, South Africa, Canada, and the U.S.A., uncovered evidence that the oxygenation of Earth’s atmosphere – generally known as the Great Oxygenation Event – coincided with the first widespread ice age on the planet.

“We can now put our hands on the rock library that preserves evidence of irreversible atmospheric change,” said Kaufman. “This singular event had a profound effect on the climate, and also on life.”

Using sulfur isotopes to determine the oxygen content of ~2.3 billion year-old rocks in the Transvaal Supergroup in South Africa, they found evidence of a sudden increase in atmospheric oxygen that broadly coincided with physical evidence of glacial debris, and geochemical evidence of a new world-order for the carbon cycle.

“The sulfur isotope change we recorded coincided with the first known anomaly in the carbon cycle. This may have resulted from the diversification of photosynthetic life that produced the oxygen that changed the atmosphere,” Kaufman said.

Two and a half billion years ago, before the Earth’s atmosphere contained appreciable oxygen, photosynthetic bacteria gave off oxygen that first likely oxygenated the surface of the ocean, and only later the atmosphere. The first formed oxygen reacted with iron in the oceans, creating iron oxides that settled to the ocean floor in sediments called banded iron-formations – layered deposits of red-brown rock that accumulated in ocean basins worldwide. Later, once the iron was used up, oxygen escaped from the oceans and started filling up the atmosphere.

Once oxygen made it into the atmosphere, Kaufman’s team suggests that it reacted with methane, a powerful greenhouse gas, to form carbon dioxide, which is 62 times less effective at warming the surface of the planet. “With less warming potential, surface temperatures may have plummeted, resulting in globe-encompassing glaciers and sea ice” said Kaufman.

In addition to its affect on climate, the rise in oxygen stimulated the rise in stratospheric ozone, our global sunscreen. This gas layer, which lies between 12 and 30 miles above the surface, decreased the amount of damaging ultraviolet sunrays reaching the oceans, allowing photosynthetic organisms that previously lived deeper down, to move up to the surface, and hence increase their output of oxygen, further building up stratospheric ozone.

“New oxygen in the atmosphere would also have stimulated weathering processes, delivering more nutrients to the seas, and may have also pushed biological evolution towards eukaryotes, which require free oxygen for important biosynthetic pathways,” said Kaufman.

The result of the Great Oxidation Event, according to Kaufman and his colleagues, was a complete transformation of Earth’s atmosphere, of its climate, and of the life that populated its surface. The study is published in the May issue of Geology.

New research study reveals origin of volcano’s carbon-based lavas

Researchers from the University of New Mexico camped inside the active crater of Oldoinyo Lengai May 2006. -  University of New Mexico.
Researchers from the University of New Mexico camped inside the active crater of Oldoinyo Lengai May 2006. – University of New Mexico.

Scientists studying the world’s most unusual volcano have discovered the reason behind its unique carbon-based lavas. The new geochemical analysis reveals that an extremely small degree of partial melting of typical minerals in the earth’s upper mantle is the source of the rare carbon-derived lava erupting from Tanzania’s Oldoinyo Lengai volcano.

Although carbon-based lavas, known as carbonatites, are found throughout history, the Oldoinyo Lengai volcano, located in the East African Rift in northern Tanzania, is the only place on Earth where they are actively erupting. The lava expelled from the volcano is highly unusual in that it contains almost no silica and greater than 50 percent carbonate minerals.Typically lavas contain high levels of silica, which increases their melting point to above 900°C (1652°F). The lavas of Oldoinyo Lengai volcano erupt as a liquid at approximately 540°C (1004°F). This low silica content gives rise to the extremely fluid lavas, which resembles motor oil when they flow.

A team of scientists from University of New Mexico, Scripps Institution of Oceanography at UC San Diego and Centre de Recherches Petrographiques et Geochimiques in Nancy, France, report new findings of volcanic gas emissions in a paper published in the May 7 issue of the journal Nature.

“The chemistry and isotopic composition of the gases reveal that the CO2 is directly sourced from the upper mantle below the East African Rift,” said David Hilton, professor of geochemistry at Scripps Institution of Oceanography at UC San Diego and coauthor of the paper. “These mantle gases allow us to infer the carbon content of the upper mantle that is producing the carbonatites to be around 300 parts per million, a concentration that is virtually identical to that measured below mid-ocean ridges.”

Mid-ocean ridges are underwater mountain ranges where the seafloor is spreading due to tectonic plates moving away from one another.Rift valleys, such as the one where Oldoinyo Lengai volcano is located, and mid-ocean ridges are considered to be distinct tectonic regions. However, this study has shown that their chemistries are identical, which led the scientists to suggest that the carbon contents of their mantle sources were not different but due to partial melting of typical minerals located in the earth’s mantle.

“Since the volcano was under magma pressure during the eruption, we were able to collect pristine samples of the volcanic gases, with minimal air contamination,” said Tobias Fischer, volcanologist at the University of New Mexico. The pristine samples collected during a 2005 eruption offered the scientists a deeper look at the processes taking place in the earth’s upper mantle.

The geochemical analyses, some of which were conducted at Hilton’s geochemical lab at Scripps Oceanography, revealed that magma from the upper mantle below both the oceans and continents is a uniform and well-mixed reservoir of “typical” volcanic gases such as carbon dioxide, nitrogen, argon and helium.

The lava expelled from the volcano is highly unusual in that it contains almost no silica and greater than 50 percent carbonate minerals.Typically lavas contain high levels of silica, which increases their melting point to above 900°C (1652°F). The lavas of Oldoinyo Lengai volcano are comprised of carbonatites, which erupts as a liquid at approximately 540°C (1004°F). This low silica content gives rise to the extremely fluid lavas, which resembles motor oil when they flow.

“These finding are significant because it shows that these extremely bizarre lavas and their parent magmas, nephelinites, were produced by melting of a typical upper mantle mineral assemblage without an extreme carbon content in the magma source,” said geochemist Bernard Marty at the Centre de Recherches Petrographiques et Geochimiques in Nancy, France. “Rather, in order to make carbonatite lavas, all you need is a very low melt fraction of 0.3 percent or less.”

Oldoinyo Lengai, like all volcanoes, emits carbon dioxide into the atmosphere as a gas. However, Lengai’s magma is unusual in that it also contains high sodium contents. About one percent of the mantle-derived carbon emitted from Lengai goes into the carbonatite melt with the remainder being emitted into the atmosphere as CO2 gas. The CO2 released into the atmosphere by volcanoes worldwide is a small fraction when compared to man-made emissions.

New Antarctic seabed sonar images reveal clues to sea-level rise

British Antarctic Survey ship RRS James Clark Ross is equipped with sonar technology to map the seabed. -  British Antarctic Survey
British Antarctic Survey ship RRS James Clark Ross is equipped with sonar technology to map the seabed. – British Antarctic Survey

Motorway-sized troughs and channels carved into Antarctica’s continental shelves by glaciers thousands of years ago could help scientists to predict future sea-level rise according to a report in the journal Geology this month (May).

Using sonar technology from onboard ships, scientists from British Antarctic Survey (BAS) and the German Alfred Wegener Institute (AWI) captured the most extensive, continuous set of images of the seafloor around the Amundsen Sea embayment ever taken. This region is a major drain point of the West Antarctic Ice Sheet (WAIS) and considered by some scientists to be the most likely site for the initiation of major ice sheet collapse.

The sonar images reveal an ‘imprint’ of the Antarctic ice sheet as it was at the end of the last ice age around 10 thousand years ago. The extent of ice covering the continent was much larger than it is today. The seabed troughs and channels that are now exposed provide new clues about the speed and flow of the ice sheet. They indicate that the controlling mechanisms that move ice towards the coast and into the sea are more complex than previously thought.

Lead author Rob Larter from British Antarctic Survey said, “One of the greatest uncertainties for predicting future sea-level rise is Antarctica’s likely contribution. It is very important for scientists and our society to understand fully how polar ice flows into the sea. Indeed, this issue was highlighted in 2007 by the Intergovernmental Panel on Climate Change (IPCC). Our research tells us more about how the ice sheet responded to warming at the end of the last ice age, and how processes at the ice sheet bed controlled its flow. This is a big step toward understanding of how the ice sheets are likely to respond to future warming.

Erosion of the Yucca Mountain crest

Yucca Mountain proposed nuclear waste depository
Yucca Mountain proposed nuclear waste depository

The Yucca Mountain crest in Nevada, USA has been proposed as a permanent site for high level radioactive waste. But a new study, already published as an article in press by Elsevier’s journal Geomorphology (http://www.elsevier.com/locate/geomorph) and recently included in the Research Highlights of Nature, shows that there may be erosion of the crest.

Kurt Stüwe of the University of Graz, Austria, together with his colleagues, used a simple numerical landscape evolution model to explore the rate of erosional decay of the Yucca Mountain crest. The model they used is well established in the expert literature, but Kurt Stüwe and his coauthors used it for the first time for a subject of economic relevance.

The researchers predict that the crest could be denuded within 500.000 years to 5 million years, using conservative parameters as the local geology of the region. It may be even more rapid if other factors are involved. The erosion procession also have the potential to affect the long-term stability of this repository.

“In our research of the morphological imprint of tectonics in mountain belts around the world, it was exciting to be able to apply our numerical models to a subject of high interest to experts outside the narrow field of geomorphology or tectonics”.commented Dr. K. Stüwe, the study’s lead investigator.