Category: Earth Observation

Magnesiowustite crystals lose the ability of infrared transmission when squashed. Image credit: JHU/NASA. Click to enlarge
Researchers from the Carnegie Institution’s Geophysical Laboratory have discovered that certain minerals stop conducting infrared light as they near the Earth’s core. Even though they transmit infrared light perfectly well on the surface, they actually absorb it when crushed by the intense pressures near the Earth’s core. This discovery will help scientists better understand the flow of heat in the Earth’s interior, as well as helping to develop new models of planetary formation and evolution.

Minerals crunched by intense pressure near the Earth’s core lose much of their ability to conduct infrared light, according to a new study from the Carnegie Institution’s Geophysical Laboratory. Since infrared light contributes to the flow of heat, the result challenges some long-held notions about heat transfer in the lower mantle, the layer of molten rock that surrounds the Earth’s solid core. The work could aid the study of mantle plumes-large columns of hot upwelling magma believed to produce features such as the Hawaiian Islands and Iceland.

Crystals of magnesiowustite, a common mineral within the deep Earth, can transmit infrared light at normal atmospheric pressures. But when squashed to over half a million times the pressure at sea level, these crystals instead absorb infrared light, which hinders the flow of heat. The research will appear in the May 26, 2006 issue of the journal Science.

Carnegie staff members Alexander Goncharov and Viktor Struzhkin, with postdoctoral fellow Steven Jacobsen, pressed crystals of magnesiowustite using a diamond anvil cell-a chamber bound by two superhard diamonds capable of generating incredible pressure. They then shone intense light through the crystals and measured the wavelengths of light that made it through. To their surprise, the compressed crystals absorbed much of the light in the infrared range, suggesting that magnesiowustite is a poor conductor of heat at high pressures.

“The flow of heat in Earth’s deep interior plays an important role in the dynamics, structure, and evolution of the planet,” Goncharov said. There are three primary mechanisms by which heat is likely to circulate in the deep Earth: conduction, the transfer of heat from one material or area to another; radiation, the flow of energy via infrared light; and convection, the movement of hot material. “The relative amount of heat flow from these three mechanisms is currently under intense debate,” Goncharov added.

Magnesiowustite is the second most common mineral in the lower mantle. Since it does not transmit heat well at high pressures, the mineral could actually form insulating patches around much of the Earth’s core. If that is the case, radiation might not contribute to overall heat flow in these areas, and conduction and convection might play a bigger role in venting heat from the core.

“It’s still too early to tell exactly how this discovery will affect deep-Earth geophysics,” Goncharov said. “But so much of what we assume about the deep Earth relies on our models of heat transfer, and this study calls a lot of that into question.”

Original Source: Carnegie Institution

Global map of forest fires. Image credit: ESA. Click to enlarge
ESA satellites have been keeping track of global forest fires for more than 10 years, and now this data is available online through ESA’s ATSR World Fire Atlas. More than 50 million hectares (123 million acres) of forests burn every year, and these fires make a signficant contribution to global pollution. By monitoring these fires, researchers can improve computer models to predict which regions are at greatest risk based on weather patterns.

For a decade now, ESA satellites have been continuously surveying fires burning across the Earth’s surface. Worldwide fire maps based on this data are now available to users online in near-real time through ESA’s ATSR World Fire Atlas.

The ATSR World Fire Atlas (WFA) – the first multi-year global fire atlas ever developed – provides data approximately six hours after acquisition and represents an important scientific resource because fire is a major agent of environmental change.

“The atlas is an excellent resource that provides a glimpse of the world that was not previously possible, and which is certain to allow ecologists to address both new and old questions regarding the role of fire in structuring the natural world,” Matt Fitzpatrick of the University of Tennessee’s Department of Ecology & Evolutionary Biology said.

More than 50 million hectares of forest are burnt annually, and these fires have a significant impact on global atmospheric pollution, with biomass burning contributing to the global budgets of greenhouse gases, like carbon dioxide. In the past decade researchers have realised the importance of monitoring this cycle. In fact, WFA data are currently being accessed mostly for atmospheric studies.

Quantifying fire is important for the ongoing study of climate change. The 1998 El Niño, for example, helped encourage fires across Borneo which emitted up to 2.5 billion tonnes of carbon into the atmosphere, equivalent to Europe’s entire carbon emissions that year.

There are over 200 registered users accessing the WFA. The data are being used in Europe, Asia, North America, South America, Africa and Australia for research in atmospheric chemistry, land use change, global change ecology, fire prevention and management and meteorology.

Harvard University, University of Toronto, National Centre for Atmosphere and NASA, among others, have used the data in research publications. To date, there are more than 100 scientific publications based on WFA data.

In addition to maps, the time, date, longitude and latitude of the hot spots are provided. The database covers 1995 to present, but complete yearly coverage begins from 1997.

The WFA data are based on results from the Along Track Scanning Radiometer (ATSR) on ESA’s ERS-2 satellite, launched in 1995, and the Advanced Along Track Scanning Radiometer (AATSR) on ESA’s Envisat satellite, launched in 2002.

These twin radiometer sensors work like thermometers in the sky, measuring thermal infrared radiation to take the temperature of Earth’s land surfaces. Fires are detected best during local night, when the surrounding land is cooler.

Temperatures exceeding 312º K (38.85 ºC) are classed as burning fires by ATSR/AATSR, which are capable of detecting fires as small as gas flares from industrial sites because of their high temperature.

The WFA is an internal and Data User Programme (DUP) project.

Original Source: ESA News Release

Artist illustration of the GOCE mission. Image credit: ESA. Click to enlarge
The European Space Agency has decided on the shortlist of spacecraft that could launch in less than a decade and contribute to the scientific exploration of our planet. The missions include Biomass, which will measure the Earth’s forests; TRAQ, which will monitor air quality; PREMIER, to watch how gasses change in the atmosphere; FLEX, to observe global photosynthesis; A-SCOPE, to track the global carbon cycle; and CoReH20, which will measure the ice/water/snow cycle. ESA requested proposals more than a year ago, and received 24 from different research groups.

ESA has announced the shortlist of new Earth Explorer mission proposals within its Living Planet Programme. This is part of the selection procedure that will eventually lead to the launch of the fourth Earth Explorer Core mission during the first half of the next decade.

The six missions cover a range of environmental issues with the aim of furthering our understanding of the Earth system and changing climate:

* BIOMASS – to take global measurements of forest biomass.

* TRAQ (TRopospheric composition and Air Quality) – to monitor air quality and long-range transport of air pollutants.

* PREMIER (PRocess Exploration through Measurements of Infrared and millimetre-wave Emitted Radiation) – to understand processes that link trace gases, radiation, chemistry and climate in the atmosphere.

* FLEX (FLuorescence EXplorer) – to observe global photosynthesis through the measurement of fluorescence.

* A-SCOPE (Advanced Space Carbon and Climate Observation of Planet Earth) – to improve our understanding of the global carbon cycle and regional carbon dioxide fluxes.

* CoReH2O (Cold Regions Hydrology High-resolution Observatory – to make detailed observations of key snow, ice and water cycle characteristics.

The selection of these six mission proposals follows the release of the Call for Earth Explorer Core mission ideas in March 2005. ESA received 24 responses, which covered a broad range of Earth science disciplines, and in particular responded well to the priorities set by the Agency’s Earth Science Advisory Committee (ESAC). These priorities focused on the global carbon and water cycles, atmospheric chemistry and climate, as well as the human element as a cross cutting issue.

The proposals were peer reviewed by scientific teams, and also appraised technically and programmatically. Based on these reviews, the ESAC evaluated the proposals and recommended the list of six mission ideas in order of priority. Following these recommendations, ESA’s Programme Board for Earth Observation on 18-19 May approved the proposal of the Director of Earth Observation Programmes to initiate assessment studies for these six mission candidates.

Earth Explorer Core missions are ESA-led research missions and the budget limit for the current set is 300 M€. The first Earth Explorer Core Missions were selected in 1999: the Earth Gravity field and Ocean Circulation (GOCE) mission and the Atmospheric Dynamics Mission (ADM-Aeolus) to be launched in 2007 and 2008 respectively. The third Core mission, Earth Clouds Aerosols and Radiation Explorer (EarthCARE), was selected in 2004 and will be launched in 2012.

In addition to the Earth Explorer Core missions, three Earth Explorer Opportunity missions are currently under implementation: SMOS for soil moisture and ocean salinity, CryoSat-2 for the study of ice sheets and sea ice, and Swarm, which is a constellation of small satellites to study the dynamics of the Earth’s magnetic field and its interactions with the Earth system, due for launch in 2007, 2009 and 2010, respectively.

The six mission candidates recently selected will significantly extend the scientific disciplines covered by ESA’s Living Planet Programme. When the assessment studies have been completed, a subset of the six candidates will be selected for feasibility study, and the mission finally selected for implementation will be launched during the first half of the next decade.

BIOMASS – the mission aims at global measurements of forest biomass. The measurement is accomplished by a space borne P-band synthetic aperture polarimetric radar. The technique is mainly based on the measurement of the cross-polar backscattering coefficient, from which forest biomass is directly retrieved. Use of multi-polarization measurements and of interferometry is also proposed to enhance the estimates. In line with the ESAC recommendations, the analysis for this mission will include comparative studies to measure terrestrial biomass using P- or L-band and consideration of alternative implementations using L-band.

TRAQ – the mission focuses on monitoring air quality and long-range transport of air pollutants. A new synergistic sensor concept allows for process studies, particularly with respect to aerosol-cloud interactions. The main issues are the rate of air quality change on regional and global scales, the strength and distribution of sources and sinks of tropospheric trace gases and aerosols influencing air quality, and the role of tropospheric composition in global change. The instrumentation consists of imaging spectrometers in the range from ultraviolet to short-wave infrared.

PREMIER – Many of the most important processes for prediction of climate change occur in the upper troposphere and lower stratosphere (UTLS). The objective is to understand the many processes that link trace gases, radiation, chemistry and climate in the atmosphere – concentrating on the processes in the UTLS region. By linking with MetOp/ National Polar-orbiting Operational Environmental Satellite System (NPOESS) data, the mission also aims to provide useful insights into processes occurring in the lower troposphere. The instrumentation consists of an infrared and a microwave radiometer.

FLEX – The main aim of the mission is global remote sensing of photosynthesis through the measurement of fluorescence. Photosynthesis by land vegetation is an important component of the global carbon cycle, and is closely linked to the hydrological cycle through transpiration. Currently there are no direct measurements available from satellites of this parameter. The main specification is for instruments to measure high spectral resolution reflectance and temperature, and to provide a multi-angular capability.

A-SCOPE – The mission aims to observe total column carbon dioxide with a nadir-looking pulsed carbon dioxide DIfferential Absorption Lidar (DIAL) for a better understanding of the global carbon cycle and regional carbon dioxide fluxes, as well as for the validation of greenhouse gas emission inventories. It will provide a spatially resolved global carbon budget combined with diagnostic model analysis through global and frequent observation of carbon dioxide. Spin-off products like aerosols, clouds and surface reflectivity are important parameters of the radiation balance of the Earth. A contribution to Numerical Weather Prediction is foreseen in connection with accurate temperature profiles. Investigations on plant stress and vitality will be supported by a fluorescence imaging spectrometer.

CoReH2O – The mission focuses on spatially detailed observations of key snow, ice, and water cycle characteristics necessary for understanding land surface, atmosphere and ocean processes and interactions by using two synthetic aperture radars at 9.6 and 17.2 GHz. It aims at closing the gaps in detailed information on snow glaciers, and surface water, with the objectives of improving modelling and prediction of water balance and streamflow for snow covered and glacierised basins, understanding and modelling the water and energy cycles in high latitudes, assessing and forecasting water supply from snow cover and glaciers, including the relation to climate change variability

Original Source: ESA News Release

Gamma ray burst host galaxies. Image credit: NASA/ESA/STScI. Click to enlarge
If a gamma ray burst happened near the Earth, it would make for a very bad day: our ozone layer would be stripped away, worldwide climate would change dramatically, and life would struggle to survive. Fortunately, it looks like they don’t happen in galaxies like our Milky Way. Researchers have found that bursts tend to occur in small irregular galaxies that lack heavier chemical elements.

A gamma-ray burst (GRB) occurring in our own galaxy could decimate life on Earth, destroying the ozone layer, triggering climate change and drastically altering life’s evolution. However, the good news is that results published online in the journal Nature show that the likelihood of a natural disaster due to a GRB is much lower than previously thought.

Long-duration GRBs are powerful flashes of high-energy radiation that arise from some of the biggest explosions of extremely massive stars. Astronomers have analysed a total of 42 long duration GRBs ??bf? those lasting more than two seconds ??bf? in several Hubble Space Telescope (HST) surveys.

They have found that the galaxies from which they originate are typically small, faint and misshapen (irregular) galaxies, while only one was spotted from a large spiral galaxy similar to the Milky Way. In contrast, supernovae (also the result of collapsing massive stars) were found to lie in spiral galaxies roughly half of the time.

These results, published in the May 10 online edition of the journal Nature, indicate that GRBs form only in very specific environments, which are different from those found in the Milky Way.

Andrew Fruchter, at the Space Telescope Science Institute, the lead author of the paper said, “Their occurrence in small irregulars implies that only stars that lack heavy chemical elements (elements heavier than hydrogen and helium) tend to produce long-duration GRBs.”

This means that long bursts happened more often in the past when galaxies did not have a large supply of heavy elements. Galaxies build up a stockpile of heavier chemical elements through the ongoing evolution of successive generations of stars. Early generation stars formed before heavier elements were abundant in the universe.

The authors also found that the locations of GRBs differed from the locations of supernovae (which are a much more common variety of exploding star). GRBs were far more concentrated on the brightest regions of their host galaxies, where the most massive stars reside. Supernovae, on the other hand, occur throughout their host galaxies.

“The discovery that long-duration GRBs lie in the brightest regions of their host galaxies suggests that they come from the most massive stars ??bf? perhaps 20 or more times as massive as our Sun,” said Andrew Levan of the University of Hertfordshire, a co-author of the study.

However, massive stars abundant in heavy elements are unlikely to trigger GRBs because they may lose too much material through stellar “winds” off their surfaces before they collapse and explode. When this happens, the stars don’t have enough mass left to produce a black hole, a necessary condition to trigger GRBs. The energy from the collapse escapes along a narrow jet, like a stream of water from a hose. The formation of directed jets, that concentrate energy along a narrow beam, would explain why GRBs are so powerful.

If a star loses too much mass, it may only leave behind a neutron star that cannot trigger a GRB. On the other hand, if the star loses too little mass, the jet cannot burn its way through the star. This means that extremely high-mass stars that puff away too much material may not be candidates for long bursts. Likewise, neither are the stars that give up too little material.

“It’s a Goldilocks scenario,” said Fruchter. “Only supernovae whose progenitor stars have lost some, but not too much mass, appear to be candidates for the formation of GRBs??bf?.

“People have, in the past, suggested that it might be possible to use GRBs to follow the locations of star formation. This obviously doesn’t work in the universe as we see it now, but, when the universe was young, GRBs may well have been more common, and we may yet be able to use them to see the very first stars to form after the Big Bang,” added Levan.

Original Source: RAS News Release

Double Star TC-2 spacecraft. Image credit: ESA. Click to enlarge
Like many comets when they get close to the Sun, the Earth has a tail. But instead of a shower of icy particles, it’s the Earth’s magnetic field that gets pushed into a long trail directed away from the Sun. Five spacecraft from ESA – the 4 Cluster spacecraft and DoubleStar – recently observed how this magnetotail can experience strange turbulence through its interaction with the Sun’s solar wind and coronal mass ejections. How and why this phenomenon happens is still a mystery.

Five spacecraft from two ESA missions unexpectedly found themselves engulfed by waves of electrical and magnetic energy as they travelled through Earth’s night-time shadow on 5 August 2004.

The data collected by the spacecraft are giving scientists an important clue to the effects of ‘space weather’ on Earth’s magnetic field.

Shortly after 15:34 CEST, something set the tail of Earth’s natural cloak of magnetism oscillating. “It was like the waves created by a boat travelling across a lake,” says Dr Tielong Zhang of the Austrian Academy of Sciences, Graz.

Only in this case, the identity of the ‘boat’ is unknown. It might be the fast flow of particles often observed in the central part of the magnetotail. Whatever it was produced waves that travelled from the centre of the tail to its outer edges.

The five spacecraft caught in this event were the four units of ESA’s Cluster mission and the first unit of the joint CNSA/ESA mission Double Star. The Cluster quartet fly in formation, passing through Earth’s magnetotail at distances of between 16 and 19 times Earth’s radius.

One of the two spacecraft of Double Star, the TC-1 spacecraft, orbits at between 10 and 13 Earth radii. All five spacecraft are designed to collect data on the magnetic bubble surrounding our planet, called the ‘magnetosphere’.

Earth’s magnetic field is generated deep inside the planet and rises into space where it constantly interacts with the solar wind, a perpetual stream of electrically charged particles released by the Sun.

The stream pulls Earth’s magnetic field into a tail that stretches behind the planet for tens of thousands of kilometres. Gusts and storms in the solar wind are known as ‘space weather’ and can make Earth’s magnetic field quake.

On 5 August 2004, Cluster and Double Star satellites found themselves in the right place at the right time. The readings showed that the oscillations took place simultaneously across an area over 30 000 km in length. This is the first time that the true extent of the oscillations has been revealed.

Previous Cluster measurements, before the launch of Double Star, could only reveal the movement across a restricted location surrounded by the four satellites.

Understanding the way Earth’s magnetic field interacts with the solar wind is the space-age equivalent of a meteorologist investigating the way a mountain range disturbs airflow, creating weather systems.

In the case of space weather, storms consist of fluctuating magnetic and electrical fields that can damage satellites and pose health risks to astronauts. If we are to fully exploit the potential of space, we have to understand the effects of space weather and be able to predict them. That’s where missions like Cluster and Double Star come in.

“By studying the August oscillations, we may be able to develop a unifying theory for all the various motions of the magnetotail,” says Zhang, who is heading the investigation into what happened that day.

Original Source: ESA Portal

Dust storms are being mapped for the ESA-led Epidemio project. Image credit: ESA Click to enlarge
All those eyes in the sky are coming in handy for purposes scientists never imagined. Now researchers from ESA are using Envisat data to track places on Earth where disease epidemics could get started. The team was able to link the outbreak of diseases in Africa with dryness and drought. So far they’ve been able to track regions which are dry, which contribute to the spread of meningitis. Aid workers can then target these regions to give vaccinations and provide early warnings.

The amount of data acquired by satellites is increasing at an exponential rate, and researchers are learning about the value of this data in fighting epidemic outbreaks as a result of the ESA’s Epidemio project.

“I was negative about the role satellites could play in addressing epidemics, but now I am positive,” Penelope Vernatsou of the Swiss Tropical Institute in Switzerland said.

The ESA-funded Epidemio project was developed in January 2004 to illustrate the benefits of remote-sensing data for studying, monitoring and predicting epidemic outbreaks.

By using data which focuses on a region’s landscape ? rainfall, vegetation, water bodies, elevation, dust mapping and temperature ? researchers are able to pinpoint climatic conditions which are favourable for harbouring various epidemic hosts, indicating where people are at greatest risk.

As the project draws to completion, epidemiologists and data users gathered in Frascati, Italy, at the ‘Earth Observation in Epidemiology Workshop’, on 8-10 March 2006, to report on how Earth observation (EO) has benefited the field of epidemiology.

Ghislain Moussavou of the Gabon-based International Centre for Medical Research (CIRMF) began studying Ebola haemorrhagic fever, which can cause runaway internal and external bleeding in humans and apes, in Congo and Gabon in the hope of spotting particular environmental characteristics associated with infected sites.

Combining ESA Envisat satellite data, under the Epidemio project, on water bodies, forest cover and digital elevation models (DEMs) with field results, Moussavou and his team were able to link the epidemic with dryness and drought.

Moussavou said determining these factors will allow officials to tell the villagers in the area that current conditions for transmission are high, and that they need to take extra precautions. “Because there are no medicines to prevent or cure Ebola, predictions and prevention are necessary.”

Dry conditions are also favourable for the spread of meningitis, an inflammation of the brain and spinal cord lining. Epidemics nearly always start in the early part of the dry season when it is hot and dusty. For this reason, ESA has been providing dust maps for high-risk areas to aid in implementing early warning systems.

Christelle Barbey of Silogic, in France, is currently involved in an Epidemio project to provide wind blown dust maps for Africa. Although her final results are still coming in, she was able to detect 100 percent of known dust events, using MeteoSat data, and determine that dust maps do correspond to a user need to contribute to meningitis prevention.

The Epidemio project – funded by the Data User Element of the ESA Earth Observation Envelope Programme – concludes its two-year mission in April 2006, but the groundwork it has laid will aid users in the continuance of their research and allow new projects to be undertaken.

Giuseppe Ottavianelli and Aude de Clercq of the HISTAR Solutions in the Netherlands are currently working on a project, backed by ESA business incubator financing, to confirm the onset of malaria epidemics in Africa, as predicted by remote sensing data.

They have designed a prototype of a sensor located in a box that detects mosquitoes as they fly overhead. The data collected by the sensor is then processed by a program inside the box, which will be placed in hat hutches in high-risk African villages, and indicates the species and numbers of the mosquitoes detected.

Malaria is transferred by the female mosquito of the species Anopheles, so if the sensor detects her presence in high numbers, public officials will be alerted so that preventive measures can be put into place.

Original Source: ESA Portal

Earth factors may be the most probable scenario for past mass extinctions. Image credit: NASA Click to enlarge
Most scientists agree that a large meteor probably wiped out the dinosaurs 65 million years ago, but two geologists from the University of Leicester think that some homegrown cataclysms might have done the trick for previous extinctions. There just isn’t enough evidence that an impact caused the mass extinction that happened 250 million years ago. But one of the largest flood basalt eruptions did occur at that time, and released enough greenhouse gasses to dramatically change the Earth’s climate – killing the dinosaurs off in the process.

Earth history has been punctuated by several mass extinctions rapidly wiping out nearly all life forms on our planet. What causes these catastrophic events? Are they really due to meteorite impacts? Current research suggests that the cause may come from within our own planet – the eruption of vast amounts of lava that brings a cocktail of gases from deep inside the Earth and vents them into the atmosphere.

University of Leicester geologists, Professor Andy Saunders and Dr Marc Reichow, are taking a fresh look at what may actually have wiped out the dinosaurs 65 million years ago and caused other similarly cataclysmic events, aware they may end up exploding a few popular myths.

The idea that meteorite impacts caused mass extinctions has been in vogue over the last 25 years, since Louis Alverez’s research team in Berkeley, California published their work about an extraterrestrial iridium anomaly found in 65-million-year-old layers at the Cretaceous-Tertiary boundary. This anomaly only could be explained by an extraterrestrial source, a large meteorite, hitting the Earth and ultimately wiping the dinosaurs – and many other organisms – off the Earth’s surface.

Professor Saunders commented: “Impacts are suitably apocalyptic. They are the stuff of Hollywood. It seems that every kid’s dinosaur book ends with a bang. But are they the real killers and are they solely responsible for every mass extinction on earth? There is scant evidence of impacts at the time of other major extinctions e.g., at the end of the Permian, 250 million years ago, and at the end of the Triassic, 200 million years ago. The evidence that has been found does not seem large enough to have triggered an extinction at these times.”

Flood basalt eruptions are – he says – an alternative kill mechanism. These do correspond with all main mass extinctions, within error of the techniques used to determine the age of the volcanism. Furthermore, they may have released enough greenhouse gases (SO2 and CO2) to dramatically change the climate. The largest flood basalts on Earth (Siberian Traps and Deccan Traps) coincide with the largest extinctions (end-Permian, and end-Cretaceous). “Pure coincidence?”, ask Saunders and Reichow.

While this is unlikely to be pure chance, the Leicester researchers are interested in precisely what the kill mechanism may be. One possibility is that the gases released by volcanic activity lead to a prolonged volcanic winter induced by sulphur-rich aerosols, followed by a period of CO2-induced warming.

Professor Andy Saunders and Dr. Marc Reichow at Leicester, in collaboration with Anthony Cohen, Steve Self, and Mike Widdowson at the Open University, have recently been awarded a NERC (Natural Environment Research Council) grant to study the Siberian Traps and their environmental impact.

The Siberian Traps are the largest known continental flood basalt province. Erupted about 250 million years ago at high latitude in the northern hemisphere, they are one of many known flood basalts provinces – vast outpourings of lava that covered large areas of the Earth’s surface. A major debate is underway concerning the origin of these provinces -including the Siberian Traps- and their environmental impact.

Using radiometric dating techniques, they hope to constrain the age and, combined with geochemical analysis, the extent, of the Siberian Traps. Measuring how much gas was released during these eruptions 250 million years ago is a considerable challenge. The researchers will study microscopic inclusions trapped in minerals of the Siberian Traps rocks to estimate the original gas contents. Using these data they hope to be able to assess the amount of SO2 and CO2 released into the atmosphere 250 million years ago, and whether or not this caused climatic havoc, wiping out nearly all life on earth. By studying the composition of sedimentary rocks laid down at the time of the mass extinction, they also hope to detect changes to seawater chemistry that resulted from major changes in climate.

From these data Professor Saunders and his team hope to link the volcanism to the extinction event. He explained: “If we can show, for example, that the full extent of the Siberian Traps was erupted at the same time, we can be confident that their environmental effects were powerful. Understanding the actual kill mechanism is the next stage. watch this space.”

Original Source: University of Leicester

A RADARSAT map of Antarctica. Image credit: AMM/SVS/NASA/CSA Click to enlarge
NASA has completed the most comprehensive survey ever made of the Earth’s polar ice caps, and confirmed that they’re disappearing at increasing rates. These rates match computer climate models precisely, giving climate scientists greater confidence in their predictions about global warming. The survey combined data from airborne maps and measurements from two ESA satellites. NASA’s ICESat satellite is taking an even more comprehensive survey of ice levels, which should be available next year.

In the most comprehensive survey ever undertaken of the massive ice sheets covering both Greenland and Antarctica, NASA scientists confirm climate warming is changing how much water remains locked in Earth’s largest storehouse of ice and snow.

Other recent studies have shown increasing losses of ice in parts of these sheets. This new survey is the first to inventory the losses of ice and the addition of new snow on both in a consistent and comprehensive way throughout an entire decade.

The survey shows that there was a net loss of ice from the combined polar ice sheets between 1992 and 2002 and a corresponding rise in sea level. The survey documents for the first time extensive thinning of the West Antarctic ice shelves and an increase in snowfall in the interior of Greenland, as well as thinning at the edges. All are signs of a warming climate predicted by computer models.

The survey, published in the Journal of Glaciology, combines new satellite mapping of the height of the ice sheets from two European Space Agency satellites. It also used previous NASA airborne mapping of the edges of the Greenland ice sheets to determine how fast the thickness is changing.

In Greenland, the survey saw large ice losses along the southeastern coast and a large increase in ice thickness at higher elevations in the interior due to relatively high rates of snowfall. This study suggests there was a slight gain in the total mass of frozen water in the ice sheet over the decade studied, contrary to previous assessments.

This situation may have changed in just the past few years, according to lead author Jay Zwally of NASA’s Goddard Space Flight Center, Greenbelt, Md. Last month NASA scientists at the Jet Propulsion Laboratory, Pasadena, Calif., reported a speed up of ice flow into the sea from several Greenland glaciers. That study included observations through 2005; Zwally’s survey concluded with 2002 data.

When the scientists added up the overall gains and losses of ice from the Greenland and Antarctic ice sheets, there was a net loss of ice to the sea. The amount of water added to the oceans (20 billion tons) is equivalent to the total amount of freshwater used in homes, businesses and farming in New York, New Jersey and Virginia each year.

“The study indicates that the contribution of the ice sheets to recent sea-level rise during the decade studied was much smaller than expected, just two percent of the recent increase of nearly three millimeters a year,” says Zwally. “Continuing research using NASA satellites and other data will narrow the uncertainties in this important issue.”

NASA is continuing to monitor the polar ice sheets with the Ice, Cloud and land Elevation Satellite (ICESat), launched in January 2003. ICESat uses a laser beam to measure the elevation of ice sheets with unprecedented accuracy three times a year. The first comprehensive ice sheet survey conducted by ICESat is expected early next year, said Zwally, who is the mission’s project scientist.

Original Source: NASA News Release

Antarctica. Image credit: Ben Holt, Sr. Click to enlarge
Researchers have completed the first comprehensive survey of Antarctic ice mass; not surprisingly, ice loss is on the rise – mostly from the West Antarctic ice shelf. From 2002 to 2005, the continent lost enough ice to raise global sea levels by about 1.2 mm (0.05 inches). The measurements were made by the GRACE satellite, which detects slight changes in the Earth’s gravity field over time. This is the most accurate estimate of Antarctic ice loss ever made.

The first-ever gravity survey of the entire Antarctic ice sheet, conducted using data from the NASA/German Aerospace Center Gravity Recovery and Climate Experiment (Grace), concludes the ice sheet’s mass has decreased significantly from 2002 to 2005.

Isabella Velicogna and John Wahr, both from the University of Colorado, Boulder, conducted the study. They demonstrated for the first time that Antarctica’s ice sheet lost a significant amount of mass since 2002. The estimated mass loss was enough to raise global sea level about 1.2 millimeters (0.05 inches) during the survey period, or about 13 percent of the overall observed sea level rise for the same period. The researchers found Antarctica’s ice sheet decreased by 152 (plus or minus 80) cubic kilometers of ice annually between April 2002 and August 2005.

That is about how much water the United States consumes in three months (a cubic kilometer is one trillion liters; approximately 264 billion gallons of water). This represents a change of about 0.4 millimeters (.016 inches) per year to global sea level rise. Most of the mass loss came from the West Antarctic ice sheet.

“Antarctica is Earth’s largest reservoir of fresh water,” Velicogna said. “The Grace mission is unique in its ability to measure mass changes directly for entire ice sheets and can determine how Earth’s mass distribution changes over time. Because ice sheets are a large source of uncertainties in projections of sea level change, this represents a very important step toward more accurate prediction, and has important societal and economic impacts. As more Grace data become available, it will become feasible to search for longer-term changes in the rate of Antarctic mass loss,” she said.

Measuring variations in Antarctica’s ice sheet mass is difficult because of its size and complexity. Grace is able to overcome these issues, surveying the entire ice sheet, and tracking the balance between mass changes in the interior and coastal areas.

Previous estimates have used various techniques, each with limitations and uncertainties and an inherent inability to monitor the entire ice sheet mass as a whole. Even studies that synthesized results from several techniques, such as the assessment by the Intergovernmental Panel on Climate Change, suffered from a lack of data in critical regions.

“Combining Grace data with data from other instruments such as NASA’s Ice, Cloud and Land Elevation Satellite; radar; and altimeters that are more effective for studying individual glaciers is expected to substantially improve our understanding of the processes controlling ice sheet mass variations,” Velicogna said.

The Antarctic mass loss findings were enabled by the ability of the identical twin Grace satellites to track minute changes in Earth’s gravity field resulting from regional changes in planet mass distribution. Mass movement of ice, air, water and solid earth reflect weather patterns, climate change and even earthquakes. To track these changes, Grace measures micron-scale variations in the 220-kilometer (137-mile) separation between the two satellites, which fly in formation.

Grace is managed for NASA by the Jet Propulsion Laboratory, Pasadena, Calif. The University of Texas Center for Space Research has overall mission responsibility. GeoForschungsZentrum Potsdam (GFZ), Potsdam, Germany, is responsible for German mission elements. Science data processing, distribution, archiving and product verification are managed jointly by JPL, the University of Texas and GFZ. The results will appear in this week’s issue of Science.

For information about NASA and agency programs on the Web, visit:
http://www.nasa.gov/home

For more information about Grace on the Web, visit:
http://www.csr.utexas.edu/grace ; and http://www.gfz-potsdam.de/grace

For University of Colorado information call Jim Scott at: (303) 492-3114.

JPL is managed for NASA by the California Institute of Technology in Pasadena.

Original Source: NASA News Release

Helheim Glacier, located in southeast Greenland. Image credit: NASA/JPL Click to enlarge
The loss of ice from Greenland doubled between 1996 and 2005, as its glaciers flowed faster into the ocean in response to a generally warmer climate, according to a NASA/University of Kansas study.

The study will be published tomorrow in the journal Science. It concludes the changes to Greenland’s glaciers in the past decade are widespread, large and sustained over time. They are progressively affecting the entire ice sheet and increasing its contribution to global sea level rise.

Researchers Eric Rignot of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., and Pannir Kanagaratnam of the University of Kansas Center for Remote Sensing of Ice Sheets, Lawrence, used data from Canadian and European satellites. They conducted a nearly comprehensive survey of Greenland glacial ice discharge rates at different times during the past 10 years.

“The Greenland ice sheet’s contribution to sea level is an issue of considerable societal and scientific importance,” Rignot said. “These findings call into question predictions of the future of Greenland in a warmer climate from computer models that do not include variations in glacier flow as a component of change. Actual changes will likely be much larger than predicted by these models.”

The evolution of Greenland’s ice sheet is being driven by several factors. These include accumulation of snow in its interior, which adds mass and lowers sea level; melting of ice along its edges, which decreases mass and raises sea level; and the flow of ice into the sea from outlet glaciers along its edges, which also decreases mass and raises sea level. This study focuses on the least well known component of change, which is glacial ice flow. Its results are combined with estimates of changes in snow accumulation and ice melt from an independent study to determine the total change in mass of the Greenland ice sheet.

Rignot said this study offers a comprehensive assessment of the role of enhanced glacier flow, whereas prior studies of this nature had significant coverage gaps. Estimates of mass loss from areas without coverage relied upon models that assumed no change in ice flow rates over time. The researchers theorized if glacier acceleration is an important factor in the evolution of the Greenland ice sheet, its contribution to sea level rise was being underestimated.

To test this theory, the scientists measured ice velocity with interferometric synthetic-aperture radar data collected by the European Space Agency’s Earth Remote Sensing Satellites 1 and 2 in 1996; the Canadian Space Agency’s Radarsat-1 in 2000 and 2005; and the European Space Agency’s Envisat Advanced Synthetic Aperture Radar in 2005. They combined the ice velocity data with ice sheet thickness data from airborne measurements made between 1997 and 2005, covering almost Greenland’s entire coast, to calculate the volumes of ice transported to the ocean by glaciers and how these volumes changed over time. The glaciers surveyed by those satellite and airborne instrument data drain a sector encompassing nearly 1.2 million square kilometers (463,000 square miles), or 75 percent of the Greenland ice sheet total area.

From 1996 to 2000, widespread glacial acceleration was found at latitudes below 66 degrees north. This acceleration extended to 70 degrees north by 2005. The researchers estimated the ice mass loss resulting from enhanced glacier flow increased from 63 cubic kilometers in 1996 to 162 cubic kilometers in 2005. Combined with the increase in ice melt and in snow accumulation over that same time period, they determined the total ice loss from the ice sheet increased from 96 cubic kilometers in 1996 to 220 cubic kilometers in 2005. To put this into perspective, a cubic kilometer is one trillion liters (approximately 264 billion gallons of water), about a quarter more than Los Angeles uses in one year.

Glacier acceleration has been the dominant mode of mass loss of the ice sheet in the last decade. From 1996 to 2000, the largest acceleration and mass loss came from southeast Greenland. From 2000 to 2005, the trend extended to include central east and west Greenland.

“In the future, as warming around Greenland progresses further north, we expect additional losses from northwest Greenland glaciers, which will then increase Greenland’s contribution to sea level rise,” Rignot said.

For information about NASA and agency programs on the Web, visit:
http://www.nasa.gov/home.

For University of Kansas Center for Remote Sensing of Ice Sheets information, visit:
http://www.cresis.ku.edu/flashindex.htm.

JPL is managed for NASA by the California Institute of Technology in Pasadena.

Original Source: NASA News Release