GPS solution provides 3-minute tsunami alerts

Researchers have shown that, by using global positioning systems (GPS) to measure ground deformation caused by a large underwater earthquake, they can provide accurate warning of the resulting tsunami in just a few minutes after the earthquake onset. For the devastating Japan 2011 event, the team reveals that the analysis of the GPS data and issue of a detailed tsunami alert would have taken no more than three minutes. The results are published on 17 May in Natural Hazards and Earth System Sciences, an open access journal of the European Geosciences Union (EGU).

Most tsunamis, including those in offshore Sumatra, Indonesia in 2004 and Japan in 2011, occur following underwater ground motion in subduction zones, locations where a tectonic plate slips under another causing a large earthquake. To a lesser extent, the resulting uplift of the sea floor also affects coastal regions. There, researchers can measure the small ground deformation along the coast with GPS and use this to determine tsunami information.

“High-precision real-time processing and inversion of these data enable reconstruction of the earthquake source, described as slip at the subduction interface. This can be used to calculate the uplift of the sea floor, which in turn is used as initial condition for a tsunami model to predict arrival times and maximum wave heights at the coast,” says lead-author Andreas Hoechner from the German Research Centre for Geosciences (GFZ).

In the new Natural Hazards and Earth System Sciences paper, the researchers use the Japan 2011 tsunami, which hit the country’s northeast coast in less than half an hour and caused significant damage, as a case study. They show that their method could have provided detailed tsunami alert as soon as three minutes after the beginning of the earthquake that generated it.

“Japan has a very dense network of GPS stations, but these were not being used for tsunami early warning as of 2011. Certainly this is going to change soon,” states Hoechner.

The scientists used raw data from the Japanese GPS Earth Observation Network (GEONET) recorded a day before to a day after the 2011 earthquake. To shorten the time needed to provide a tsunami alert, they only used data from 50 GPS stations on the northeast coast of Japan, out of about 1200 GEONET stations available in the country.

At present, tsunami warning is based on seismological methods. However, within the time limit of 5 to 10 minutes, these traditional techniques tend to underestimate the earthquake magnitude of large events. Furthermore, they provide only limited information on the geometry of the tsunami source (see note). Both factors can lead to underprediction of wave heights and tsunami coastal impact. Hoechner and his team say their method does not suffer from the same problems and can provide fast, detailed and accurate tsunami alerts.

The next step is to see how the GPS solution works in practice in Japan or other areas prone to devastating tsunamis. As part of the GFZ-lead German Indonesian Tsunami Early Warning System project, several GPS stations were installed in Indonesia after the 2004 earthquake and tsunami near Sumatra, and are already providing valuable information for the warning system.

“The station density is not yet high enough for an independent tsunami early warning in Indonesia, since it is a requirement for this method that the stations be placed densely close to the area of possible earthquake sources, but more stations are being added,” says Hoechner.

Rio Grande rift: From tectonics to groundwater, north to south

This is the cover of GSA Special Paper 494: New Perspectives on Rio Grande Rift Basins: From Tectonics to Groundwater. -  Mark R. Hudson and V.J.S. (Tien) Grauch (editors)
This is the cover of GSA Special Paper 494: New Perspectives on Rio Grande Rift Basins: From Tectonics to Groundwater. – Mark R. Hudson and V.J.S. (Tien) Grauch (editors)

Extending from Colorado, USA, to the state of Chihuahua, Mexico, the Rio Grande rift divides the Colorado Plateau on the west from the interior of the North American craton on the east. The rift is named after the Rio Grande, the major river that flows through most of its extent, from southern Colorado, through New Mexico, and along the border between Texas, USA, and the Mexican states of Chihuahua, Coahuila, Nuevo León, and Tamaulipas.

Individual valleys of the Rio Grande rift are easy to recognize to the north, but more difficult in the Basin and Range in southern New Mexico, west Texas, and northern Mexico. This new book from The Geological Society of America focuses on the Rio Grande rift’s upper crustal basins.

Editors Mark R. Hudson and V.J.S. (Tien) Grauch of the U.S. Geological Survey have organized the book geographically, with study areas progressing from north to south. Eighteen chapters cover a variety of topics, including sedimentation history, rift basin geometries and the influence of older structure on rift basin evolution, faulting and strain transfer within and among basins, relations of magmatism to rift tectonism, and basin hydrogeology.

Western Indian Ocean earthquake and tsunami hazard potential greater than previously thought

The location of the Makran subduction zone of Pakistan and Iran and locations of recorded earthquakes including the 1945 magnitude 8.1 earthquake (red dot to the north indicates the 1947 magnitude 7.3 earthquake). The profile for the thermal modelling of this study is the N-S trending black line, with distance given along the profile from the shallowest part of the subduction zone in the south (0 kilometers) to the most northern potential earthquake rupture extent (350 kilometers). -  University of Southampton Ocean and Earth Science
The location of the Makran subduction zone of Pakistan and Iran and locations of recorded earthquakes including the 1945 magnitude 8.1 earthquake (red dot to the north indicates the 1947 magnitude 7.3 earthquake). The profile for the thermal modelling of this study is the N-S trending black line, with distance given along the profile from the shallowest part of the subduction zone in the south (0 kilometers) to the most northern potential earthquake rupture extent (350 kilometers). – University of Southampton Ocean and Earth Science

Earthquakes similar in magnitude to the 2004 Sumatra earthquake could occur in an area beneath the Arabian Sea at the Makran subduction zone, according to recent research published in Geophysical Research Letters.

The research was carried out by scientists from the University of Southampton based at the National Oceanography Centre Southampton (NOCS), and the Pacific Geoscience Centre, Natural Resources Canada.

The study suggests that the risk from undersea earthquakes and associated tsunami in this area of the Western Indian Ocean – which could threaten the coastlines of Pakistan, Iran, Oman, India and potentially further afield – has been previously underestimated. The results highlight the need for further investigation of pre-historic earthquakes and should be fed into hazard assessment and planning for the region.

Subduction zones are areas where two of the Earth’s tectonic plates collide and one is pushed beneath the other. When an earthquake occurs here, the seabed moves horizontally and vertically as the pressure is released, displacing large volumes of water that can result in a tsunami.

The Makran subduction zone has shown little earthquake activity since a magnitude 8.1 earthquake in 1945 and magnitude 7.3 in 1947. Because of its relatively low seismicity and limited recorded historic earthquakes it has often been considered incapable of generating major earthquakes.

Plate boundary faults at subduction zones are expected to be prone to rupture generating earthquakes at temperatures of between 150 and 450 °C. The scientists used this relationship to map out the area of the potential fault rupture zone beneath the Makran by calculating the temperatures where the plates meet. Larger fault rupture zones result in larger magnitude earthquakes.

“Thermal modelling suggests that the potential earthquake rupture zone extends a long way northward, to a width of up to 350 kilometres which is unusually wide relative to most other subduction zones,” says Gemma Smith, lead author and PhD student at University of Southampton School of Ocean and Earth Science, which is based at NOCS.

The team also found that the thickness of the sediment on the subducting plate could be a contributing factor to the magnitude of an earthquake and tsunami there.

“If the sediments between the plates are too weak then they might not be strong enough to allow the strain between the two plates to build up,” says Smith. “But here we see much thicker sediments than usual, which means the deeper sediments will be more compressed and warmer. The heat and pressure make the sediments stronger. This results in the shallowest part of the subduction zone fault being potentially capable of slipping during an earthquake.

“These combined factors mean the Makran subduction zone is potentially capable of producing major earthquakes, up to magnitude 8.7-9.2. Past assumptions may have significantly underestimated the earthquake and tsunami hazard in this region.”

Research helps paint finer picture of massive 1700 earthquake

In 1700, a massive earthquake struck the west coast of North America. Though it was powerful enough to cause a tsunami as far as Japan, a lack of local documentation has made studying this historic event challenging.

Now, researchers from the University of Pennsylvania have helped unlock this geological mystery using a fossil-based technique. Their work provides a finer-grained portrait of this earthquake and the changes in coastal land level it produced, enabling modelers to better prepare for future events.

Penn’s team includes Benjamin Horton, associate professor and director of the Sea Level Research Laboratory in the Department of Earth and Environmental Science in the School of Arts and Sciences, along with then lab members Simon Engelhart and Andrea Hawkes. They collaborated with researchers from Canada’s University of Victoria, the National Taiwan University, the Geological Survey of Canada and the United States Geological Survey.

The research was published in the Journal of Geophysical Research: Solid Earth.

The Cascadia Subduction Zone runs along the Pacific Northwest coast of the United States to Vancouver Island in Canada. This major fault line is capable of producing megathrust earthquakes 9.0 or higher, though, due to a dearth of observations or historical records, this trait was only discovered within the last several decades from geology records. The Lewis and Clark expedition did not make the first extensive surveys of the region until more than 100 years later, and contemporaneous aboriginal accounts were scarce and incomplete.

The 1700 Cascadia event was better documented in Japan than in the Americas. Records of the “orphan tsunami” – so named because its “parent” earthquake was too far away to be felt – gave earth scientists hints that this subduction zone was capable of such massive seismic activity. Geological studies provided information about the earthquake, but many critical details remained lost to history.

“Previous research had determined the timing and the magnitude, but what we didn’t know was how the rupture happened,” Horton said. “Did it rupture in one big long segment, more than a thousand kilometers, or did it rupture in parcels?”

To provide a clearer picture of how the earthquake occurred, Horton and his colleagues applied a technique they have used in assessing historic sea-level rise. They traveled to various sites along the Cascadia subduction zone, taking core samples from up and down the coast and working with local researchers who donated pre-existing data sets. The researchers’ targets were microscopic fossils known as foraminifera. Through radiocarbon dating and an analysis of different species’ positions with the cores over time, the researchers were able to piece together a historical picture of the changes in land and sea level along the coastline. The research revealed how much the coast suddenly subsided during the earthquake. This subsidence was used to infer how much the tectonic plates moved during the earthquake.

“What we were able to show for the first time is that the rupture of Cascadia was heterogeneous, making it similar to what happened with the recent major earthquakes in Japan, Chile and Sumatra,” Horton said.

This level of regional detail for land level changes is critical for modeling and disaster planning.

“It’s only when you have that data that you can start to build accurate models of earthquake ruptures and tsunami inundation,” Horton said. “There were areas of the west coast of the United States that were more susceptible to larger coastal subsidence than others.”

The Cascadia subduction zone is of particular interest to geologists and coastal managers because geological evidence points to recurring seismic activity along the fault line, with intervals between 300 and 500 years. With the last major event occurring in 1700, another earthquake could be on the horizon. A better understanding of how such an event might unfold has the potential to save lives.

“The next Cascadia earthquake has the potential to be the biggest natural disaster that the Unites States will have to come to terms with – far bigger than Sandy or even Katrina,” Horton said. “It would happen with very little warning; some areas of Oregon will have less than 20 minutes to evacuate before a large tsunami will inundate the coastline like in Sumatra in 2004 and Japan in 2011.”

Scientists find extensive glacial retreat in Mount Everest region

Researchers taking a new look at the snow and ice covering Mount Everest and the national park that surrounds it are finding abundant evidence that the world’s tallest peak is shedding its frozen cloak. The scientists have also been studying temperature and precipitation trends in the area and
found that the Everest region has been warming while snowfall has been declining since the early 1990s.

Members of the team conducting these studies will present their
findings on May 14 at the Meeting of the Americas in Cancun,
Mexico – a scientific conference organized and co-sponsored by
the American Geophysical Union.

Glaciers in the Mount Everest region have shrunk by 13 percent
in the last 50 years and the snowline has shifted upward by 180
meters (590 feet), according to Sudeep Thakuri, who is leading
the research as part of his PhD graduate studies at the University
of Milan in Italy.

Glaciers smaller than one square kilometer are
disappearing the fastest and have experienced a 43 percent
decrease in surface area since the 1960s. Because the glaciers are
melting faster than they are replenished by ice and snow, they are
revealing rocks and debris that were previously hidden deep
under the ice. These debris-covered sections of the glaciers have
increased by about 17 percent since the 1960s, according to
Thakuri. The ends of the glaciers have also retreated by an
average of 400 meters since 1962, his team found.

The researchers suspect that the decline of snow and ice in the
Everest region is from human-generated greenhouse gases
altering global climate. However, they have not yet established a
firm connection between the mountains’ changes and climate
change, Thakuri said.

He and his team determined the extent of glacial change on
Everest and the surrounding 1,148 square kilometer (713 square
mile) Sagarmatha National Park by compiling satellite imagery
and topographic maps and reconstructing the glacial history.
Their statistical analysis shows that the majority of the glaciers in
the national park are retreating at an increasing rate, Thakuri

To evaluate the temperature and precipitation patterns in the
area, Thakuri and his colleagues have been analyzing hydro-
meteorological data from the Nepal Climate Observatory stations
and Nepal’s Department of Hydrology and Meteorology. The
researchers found that the Everest region has undergone a 0.6
degree Celsius (1.08 degrees Fahrenheit) increase in temperature
and 100 millimeter (3.9 inches) decrease in precipitation during
the pre-monsoon and winter months since 1992.

In subsequent research, Thakuri plans on exploring the climate-
glacier relationship further with the aim of integrating the
glaciological, hydrological and climatic data to understand the
behavior of the hydrological cycle and future water availability.

“The Himalayan glaciers and ice caps are considered a water
tower for Asia since they store and supply water downstream
during the dry season,” said Thakuri. “Downstream populations
are dependent on the melt water for agriculture, drinking, and
power production.”

The drones of oil

Researcher Aleksandra Sima at Bergen's Centre for Integrated Petroleum Research (CIPR) is part of the Norwegian research team using drones to look for oil. -  Photo: Eivind Senneset/UiB
Researcher Aleksandra Sima at Bergen’s Centre for Integrated Petroleum Research (CIPR) is part of the Norwegian research team using drones to look for oil. – Photo: Eivind Senneset/UiB

Geologists have long used seismology on the bottom of the ocean or have been throwing dynamite from snowmobiles when they look for oil. But now researchers at Centre for integrated petroleum research (CIPR), a joint venture between the University of Bergen (UiB) and Uni Research, have found a new preferred method – using drones to map new oil reserves from the air.

- In reality the drones can be viewed as an advanced camera tripod, which helps geologists to map inaccessible land in an efficient manner. The use of drones facilitates our efforts to define the geology and to find oil, says researcher Aleksandra Sima at CIPR about the drone that she and her fellow researchers have just acquired to take aerial shots of rocks.

Virtual fieldwork

Sima is a member of CIPR’s Virtual Outcrop Geology (VOG) group. The group’s main task is to create digital maps in 3D of potential oil fields. Using laser scanners, infrared sensors and digital cameras, the researchers create realistic, virtual models. Every tiny pixel of an image can store information on minerals and rocks.

These high-tech models help the geologists to criss-cross the landscape, not unlike what you will find on Google Earth. This virtual fieldwork enables the researchers to gather information on anything from the type of rock to the thickness of the sedimentation; all with the help of a few mouse clicks on the computer.

- A landscape’s surface often reflects what lies beneath ground and corresponds with the rocks below the seabed. When we have an overview of the rocks and minerals in one area, it is far easier to make estimates about where to find oil and how the oil flows, says Simon Buckley, senior researcher at CIPR and head of the VOG group.

Quick and affordable

So far, the researchers have used ground-based laser scanners (LIDAR), infrared sensors and cameras to replicate the landscape. But putting instruments on the ground is both time-consuming and limited to lower ground areas.

In higher elevations in the shadows of sensors, for instance behind rocks or high mountains, the researchers have had to mount the cameras and laser sensors to helicopters, which they have leased.

- Using drones is more affordable. All places can be reached quickly and you can shoot in inaccessible areas, Buckley explains.

Pictures shot with the help of a drone complement the images from low-level terrain that the researchers already have in hand. The end result is more precise and complete 3D models.

- The aim is to bring all models together to get the best possible geological map of an area, says Buckley.

The use of drones in the search for oil is similar to techniques used in Switzerland and Germany to look for minerals. The models created by the CIPR researchers can also be used for research on CO2 storage.

- It isn’t hard to collect a point cloud of laser readings and present these. The challenge is to use the data for geological analysis, Buckley points out.

A helicopter in the office

The drone is operated from the ground just like a radio-controlled plane, shooting images of the earth’s surface from the air. The pilot on the ground also operates the camera.

There are plenty of restrictions in place, though, and not anyone can fly a drone. Norwegian aviation authorities put strict regulations on anyone wanting to use drones for research. Aleksandra Sima has been practising in a flight simulator and has tested mini helicopters in her office.

- The worst thing that can happen is that a drone crashes and hurts people, says Sima before reassuringly adding.

- But we won’t be flying drones in populated areas.

Groundwater unaffected by shale gas production in Arkansas

A new study by scientists at Duke University and the U.S. Geological Survey (USGS) finds no evidence of groundwater contamination from shale gas production in Arkansas.

“Our results show no discernible impairment of groundwater quality in areas associated with natural gas drilling and hydraulic fracturing in this region,” said Avner Vengosh, professor of geochemistry and water quality at Duke’s Nicholas School of the Environment.

The scientists sampled 127 shallow drinking water wells in areas overlying Fayetteville Shale gas production in north-central Arkansas. They analyzed the samples for major and trace elements and hydrocarbons, and used isotopic tracers to identify the sources of possible contaminants. The researchers compared the chemical composition of the contaminants to those found in water and gas samples from nearby shale gas drilling sites.

“Only a fraction of the groundwater samples we collected contained dissolved methane, mostly in low concentrations, and the isotopic fingerprint of the carbon in the methane in our samples was different from the carbon in deep shale gas in all but two cases,” Vengosh said. This indicates that the methane was produced primarily by biological activity in the region’s shallow aquifers and not from shale gas contamination, he said.

“These findings demonstrate that shale gas development, at least in this area, has been done without negatively impacting drinking water resources,” said Nathaniel R. Warner, a PhD student at Duke and lead author of the study.

Robert Jackson, a professor of environmental sciences at Duke, added, “Overall, homeowners typically had good water quality, regardless of whether they were near shale gas development.”

Vengosh, Warner, Jackson and their colleagues published their peer-reviewed findings in the online edition of the journal Applied Geochemistry.

Hydraulic fracturing, also called hydrofracking or fracking, involves pumping water, sand and chemicals deep underground into horizontal gas wells at high pressure to crack open hydrocarbon-rich shale and extract natural gas. Accelerated shale gas drilling and hydrofracking in recent years has fueled concerns about water contamination by methane, fracking fluids and wastewater from the operations.

Previous peer-reviewed studies by Duke scientists found direct evidence of methane contamination in drinking water wells near shale-gas drilling sites in the Marcellus Shale basin of northeastern Pennsylvania, as well as possible connectivity between deep brines and shallow aquifers, but no evidence of contamination from fracking fluids.

“The hydrogeology of Arkansas’s Fayetteville Shale basin is very different from Pennsylvania’s Marcellus Shale,” Vengosh noted. Far from contradicting the earlier studies, the Arkansas study “suggests that variations in local and regional geology play major roles in determining the possible risk of groundwater impacts from shale gas development. As such, they must be taken into consideration before drilling begins.”

Human factors — such as the drilling techniques used and the integrity of the wellbores – also likely play a role in preventing, or allowing, gas leakage from drilling sites to shallow aquifers, Vengosh said.

“The take-home message is that regardless of the location, systematic monitoring of geochemical and isotopic tracers is necessary for assessing possible groundwater contamination,” he said. “Our findings in Arkansas are important, but we are still only beginning to evaluate and understand the environmental risks of shale gas development. Much more research is needed.”

Climate record from bottom of Russian lake shows Arctic was warmer millions of years ago

The Lake El'gygytgyn drilling rig is shown at night. -  The Lake El'gygytgyn Drilling Project
The Lake El’gygytgyn drilling rig is shown at night. – The Lake El’gygytgyn Drilling Project

The Arctic was very warm during a period roughly 3.5 to 2 million years ago–a time when research suggests that the level of carbon dioxide in the atmosphere was roughly comparable to today’s–leading to the conclusion that relatively small fluctuations in carbon dioxide levels can have a major influence on Arctic climate, according to a new analysis of the longest terrestrial sediment core ever collected in the Arctic.

“One of our major findings is that the Arctic was very warm in the middle Pliocene and Early Pleistocene–roughly 3.6 to 2.2 million years ago–when others have suggested atmospheric carbon dioxide was not much higher than levels we see today,” said Julie Brigham-Grette, of the University of Massachusetts Amherst.

Brigham-Grette is a National Science Foundation- (NSF) funded researcher on the sediment core project and a lead author of a new paper published this week in the journal Science that describes the results.

She added that “this could tell us where we are going in the near future. In other words, the Earth system response to small changes in carbon dioxide is bigger than suggested by earlier climate models.”

The data come from the analysis of a continuous cylinder of sediments collected by NSF-funded researchers from the bottom of ice-covered Lake El’gygytgyn, pronounced El-Guh-Git-Kin, the oldest deep lake in the northeast Russian Arctic, located 100 kilometers (62 miles) north of the Arctic Circle. The drilling was an international project.

Drilling took place in the early months of 2009. The Earth Sciences and Polar Programs divisions of NSF’s Geosciences Directorate funded the drilling and analysis.

Analysis of the sediment core provides “an exceptional window into environmental dynamics” never before possible, noted Brigham-Grette.

“While existing geologic records from the Arctic contain important hints about this time period, what we are presenting is the most continuous archive of information about past climate change from the entire Arctic borderlands,” she said. “Like reading a detective novel, we can go back in time and reconstruct how the Arctic evolved with only a few pages missing here and there.”

Results of the core analysis, according to Brigham-Grette, have “major implications for understanding how the Arctic transitioned from a forested landscape without ice sheets to the ice- and snow-covered land we know today.”

“Lake E,” as it is often called, was formed 3.6 million years ago when a meteorite, perhaps a kilometer in diameter, hit the Earth and blasted out an 18-kilometer (11-mile) wide crater. The lake bottom has been accumulating layers of sediment ever since the initial impact.

The lake also is situated in one of the few areas of the Arctic that was not eroded by continental ice sheets during ice ages. So a thick, continuous sediment record was left remarkably undisturbed. Cores from Lake E reach back in geologic time nearly 25 times farther than Greenland ice cores that span only the past 140,000 years.

Important to the story are the fossil pollen found in the core, including Douglas fir and hemlock, clearly not found in this part of the Arctic today. The pollen allows the reconstruction of the vegetation living around the lake in the past, which in turn paints a picture of past temperatures and precipitation.

Another significant finding is documentation of sustained warmth in the Middle Pliocene, with summer temperatures of about 15 to 16 degrees Celsius (59 to 61 degrees Fahrenheit), about 8 degrees Celsius (14.4 degrees Fahrenheit) warmer than today, and regional precipitation three times higher.

“We show that this exceptional warmth well north of the Arctic Circle occurred throughout both warm and cold orbital cycles and coincides with a long interval of 1.2 million years when other researchers from the ANDRILL project have shown the West Antarctic Ice Sheet did not exist,” the authors point out.

Hence both poles share some common history, but the pace of change differed.

Along with Brigham-Grette, her co-authors Martin Melles of the University of Cologne, Germany, and Pavel Minyuk of Russia’s Northeast Interdisciplinary Scientific Research Institute, Magadan, led research teams on the project. Robert DeConto, also at the University of Massachusetts, led the climate-modeling efforts. These data were compared with ecosystem reconstructions performed by collaborators at University of Berlin and University of Cologne.

The Lake E cores provide a terrestrial perspective on the stepped pacing of several portions of the climate system through the transition from a warm, forested Arctic to the first occurrence of land ice, Brigham-Grette says, and the eventual onset of major glacial-interglacial cycles.

“It is very impressive that summer temperatures during warm intervals even as late as 2.2 million years ago were always warmer than in our pre-Industrial reconstructions,” she added.

Minyuk notes that they also observed a major drop in Arctic precipitation at around the same time large Northern Hemispheric ice sheets first expanded and ocean conditions changed in the North Pacific. This has major implications for understanding what drove the onset of the ice ages.

The sediment core also reveals that even during the first major “cold snap” to show up in the record 3.3 million years ago, temperatures in the western Arctic were similar to recent averages of the past 12,000 years. “Most importantly, conditions were not ‘glacial,’ raising new questions as to the timing of the first appearance of ice sheets in the Northern Hemisphere,” the authors add.

This week’s paper is the second article published in Science by these authors using data from the Lake E project. Their first in July 2012 covered the period from the present to 2.8 million years ago, while the current work addresses the record from 2.2 to 3.6 million years.

“This latest paper completes our goal of providing an overview of new knowledge of the evolution of Arctic change across the Western borderlands back to 3.6 million years and places this record into a global context with comparisons to records in the Pacific, the Atlantic and Antarctica,” Melles points out.

The Lake E paleoclimate reconstructions and climate modeling are consistent with estimates made by other research groups that support the idea that Earth’s climate sensitivity to carbon dioxide may well be higher than suggested by the 2007 report of the Intergovernmental Panel on Climate Change.

The effect of climate change on iceberg production by Greenland glaciers

While the impact of climate change on the surface of the Greenland ice sheet has been widely studied, a clear understanding of the key process of iceberg production has eluded researchers for many years. Published in Nature this week, a new study presents a sophisticated computer model that provides a fresh insight into the impact of climate change on the production of icebergs by Greenland glaciers, and reveals that the shape of the ground beneath the ice has a strong effect on its movement.

Over the past decade, ice-loss from the Greenland Ice Sheet has been accelerating, raising concerns about runaway losses and consequent sea-level rise. But research into the four major Greenland fast-flowing glaciers has enabled scientists to show that while these glaciers may show several bursts of retreat and periods of high iceberg formation in future, the rapid acceleration seen in recent years is unlikely to continue unchecked.

This is a crucial step forward in understanding how Greenland’s glaciers will contribute to sea-level rise in the future and indicates, say the scientists, how important a more detailed knowledge of such glaciers is.
The scientists first investigated the current behaviour of the four glaciers and found that the rate at which they lose ice depends critically on the shape of the fjords in which they sit, and the topography of the rock below them.

A computer model for fast-flowing outlet glaciers was then specifically designed from their investigations. It gave a projected sea-level-rise contribution from these glaciers of 2cm to 5cm by the year 2200, which is lower than estimates based solely on the extrapolation of current trends.

Lead author Dr Faezeh Nick, of the Université Libre de Bruxelles, says

“I am excited by the way we have managed to create a detailed picture of the workings of the glaciers. It turns out that if the fjord a glacier sits in is wide or narrow it really affects the way the glacier reacts. The important role of the terrain below the ice shows we need to get a much clearer picture of the rest of Greenland’s glaciers before we have the whole story.”

The scientists chose the four glaciers, Petermann, Kangerdlugssuaq, Helheim and Jakobshavn Isbræ, as together these drain around 20 per cent of the Greenland ice sheet. The model, which was developed within the EU funded ice2sea programme, predicts that, together these glaciers will lose on average, 30Gt of ice per year to 47Gt per year over the 21st century. A Gigaton (Gt) is the equivalent of 1 cubic kilometre (km3) of water. For comparison Lake Geneva contains about 90Gt of water.

Professor David Vaughan, who works at the British Antarctic Survey in Cambridge and is head of the ice2sea programme says,

“We know that the breaking off of icebergs from glaciers is influenced by climate, but this is the first time we’ve been able make projections of how the most important glaciers in Greenland will be affected by future climate change. The ice2sea research led by Dr Nick shows how a truly international program can make it possible for scientists to work together across different institutions to make significant steps forward.”

Geologists study mystery of ‘eternal flames’

A gas-fired flame shines through a waterfall at Chestnut Ridge Park in Erie County, N.Y. -  Indiana University
A gas-fired flame shines through a waterfall at Chestnut Ridge Park in Erie County, N.Y. – Indiana University

“Eternal flames” fueled by hydrocarbon gas could shine a light on the presence of natural gas in underground rock layers and conditions that let it seep to the surface, according to research by geologists at the Department of Geological Sciences and the Indiana Geological Survey at Indiana University Bloomington.

A little-known but spectacular flame in Erie County, N.Y., is the focus of an article in the journal Marine and Petroleum Geology, co-authored by Agnieszka Drobniak, research scientist with the Indiana Geological Survey, and Arndt Schimmelmann, senior scientist in the Department of Geological Sciences in the College of Arts and Sciences.

The article results from a U.S. Department of Energy research grant to Schimmelmann and Maria Mastalerz, senior scientist with the Indiana Geological Survey and graduate faculty member at the Department of Geological Sciences. The project seeks to identify natural gas seeps in Indiana and nearby states and assess their contributions to atmospheric concentrations of greenhouse gases.

The researchers said much remains to be learned about the passage of gas from underground rock layers to the Earth’s surface — occasionally in “macro seeps” strong and abundant enough to produce a continuous flame like the one in western New York.

“The story is developing,” Schimmelmann said.

Giuseppe Etiope of the National Institute of Geophysics and Volcanology in Italy is lead author of the Marine and Petroleum Geology article, “Natural seepage of shale gas and the origin of ‘eternal flames’ in the Northern Appalachian Basin, USA.” Etiope, who has studied eternal flames around the world, said the New York flame, behind a waterfall in Chestnut Ridge Park, is the most beautiful he has seen.

Not only that, but it may feature the highest concentrations of ethane and propane of any known natural gas seep. Approximately 35 percent of the gas is ethane and propane, as opposed to methane, the dominant constituent in natural gas. Ethane and propane can be valuable byproducts in the processing of natural gas.

By analyzing the gases and comparing them with gas well records from the region, the researchers concluded the gas fueling the Chestnut Ridge Park flame originates from Rhinestreet Shale, an Upper Devonian formation about 400 meters deep. It reaches the surface through passages associated with faulting caused by tectonic activity.

At the New York site, the researchers identified numerous “micro seeps” of gas, apparently from the same source that fuels the eternal flame. This suggests that such seeps, if they are numerous and widespread, could make a significant contribution to atmospheric concentrations of greenhouse gases and other pollutants.

The researchers also studied a larger eternal flame at Cook Forest State Park in northwestern Pennsylvania. They determined that flame, in a continuously burning fire pit, is not a natural seep but a leak from an abandoned gas well. The source is thought to be a conventional gas reservoir, not shale.

Mastalerz said naturally occurring methane sources are believed to account for about 30 percent of the total methane emissions in the Earth’s atmosphere. Natural gas seeps are thought to be the second most significant source of naturally occurring methane emissions, after wetlands.

But finding seeps is like searching for a needle in a haystack. Last year, the researchers surveyed a region of Kentucky that is geologically similar to western New York — and where “burning springs” figure in local history and folklore — but turned up no evidence of escaping natural gas.

Schimmelmann said researchers have found elevated levels of carbon dioxide in caves, possibly resulting from methane that is converted by microorganisms to carbon dioxide gas as it seeps slowly toward the surface. Carbon dioxide is also a greenhouse gas, but it is 20 times less effective at trapping heat than methane.

The findings suggest natural gas seeps occur in areas that have experienced tectonic activity, and it may be easier to find them in caves, which capture and concentrate gas when it reaches the surface. A next step in the research, planned for this summer, is to continue the search in areas of Pennsylvania, West Virginia and Virginia where gas-bearing shale underlies cave systems.