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  • richardmitnick 12:23 pm on May 23, 2017 Permalink | Reply
    Tags: AGU, Cosmic Muons Reveal the Land Hidden Under Ice, , ,   

    From Eos: “Cosmic Muons Reveal the Land Hidden Under Ice” 

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    Eos

    5.23.17
    Jenny Lunn
    jlunn@agu.org

    Scientists accurately map the shape of the bedrock beneath a glacier using a new technique.

    1
    Aletsch glacier seen from Jungfraujoch. A tunnel runs through the bedrock below this glacier; researchers placed sensors within this tunnel to help map the shape of the bedrock under the ice. Credit: Alessandro Lechmann

    The land surface under a glacier is sculpted and shaped by the ice passing over it. Data about the shape of the bedrock yield information crucial to understanding erosional processes underneath a glacier. However, the inaccessibility of sites where glacial erosion currently occurs presents big challenges for advancing this understanding.

    A range of techniques has been used to map the bedrock beneath glaciers, including drilling, seismic surveys, multibeam bathymetry, gravity measurements, and radio-echo soundings. The accuracy of results has been limited, so Nishiyama et al [Geophysical Research Letters]. tested a different technique: emulsion film muon radiography.

    2
    A muon detector in the Jungfrau railway tunnel awaiting arrival of the cosmic ray muons. Credit: Nishiyama et al.

    Muons are formed when cosmic rays collide with atoms in Earth’s upper atmosphere. They descend toward Earth, with about 10,000 muons reaching each square meter of Earth’s surface every minute. One of their significant properties is that they can pass through matter, even dense and solid objects on Earth.

    Particle detectors can be used to measure the quantity of muons and their trajectories, which can reveal information about the materials that they have passed through.

    Because cosmic muons travel only downward, detectors need to be located below the objects to be surveyed. This technique has been used by geophysicists to scan the interior architecture of volcanoes, seismic faults, and caves and to detect carbon leaks, but it has posed a challenge for surveying the bedrock beneath glaciers.

    The team of researchers found a solution in the central Swiss Alps: the Jungfrau railway tunnel, which runs through the bedrock beneath the Aletsch glacier. They set up three particle detectors in the tunnel that are oriented upward with a view of the bedrock beneath the base of the largest glacier of Europe.

    3
    Three-dimensional reconstructed bedrock shape (blue) under the uppermost part of the Aletsch glacier. The shape of the interface was determined from the cosmic ray muon measurement performed at three muon detectors (D1, D2, and D3) along the railway tunnel (gray line). Bedrock that pokes through ice is in gray tones. Jungfraufirn is a small glacier that feeds the Aletsch glacier. Blue dots on the gray line represent points where scientists sampled rocks within the tunnel. The image is Figure 5b in Nishiyama et al.; dashed lines outline a cross section of this 3-D map that can be found in Figure 5c. Credit: Nishiyama et al.; base map from SWISSIMAGE, reproduced by permission of swisstopo (BA17061)

    Different types of particle detectors are available for muon radiography, but the team selected emulsion films, a special type of photographic film that can be used in remote and harsh environments because it does not require any electric power or computers for operation.

    Because of the density contrast between ice and rock, the patterns of muons captured on the film over a 47-day period could be used to accurately map the shape of the bedrock below the glacier.

    Using this technique, the researchers were able to map the bedrock-ice interface beneath the glacier over a 4000-square-meter area. They were also able to infer the glacier’s response to global warming. In particular, the team predicts a larger frequency of rock avalanches as the ice shrinks, exacerbated by reconstructed bedrock geometry beneath the glacier. This increase is of particular concern because buildings are situated on top of the bedrock. These include tourist facilities, a research station, and communications infrastructure, as well as the railway tunnel itself, which cuts through the bedrock.

    The use of cosmic muon radiography is spreading in various fields, including geophysics and civil engineering. This first application of the technique in glacial geology complements data collected by other methods and has the potential to be applied in other glacial locations underlain by a tunnel. (Geophysical Research Letters, https://doi.org/10.1002/2017GL073599, 2017)

    See the full article here .

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  • richardmitnick 1:59 pm on March 17, 2017 Permalink | Reply
    Tags: AGU, , , , Mapping the Topographic Fingerprints of Humanity Across Earth   

    From Eos: “Mapping the Topographic Fingerprints of Humanity Across Earth” 

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    AGU
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    Eos

    16 March 2017
    Paolo Tarolli
    Giulia Sofia
    Erle Ellis

    1
    Fig. 1. Three-dimensional view of Bingham Canyon Mine, Utah, a human-made topographic signature, based on a free, open-access high-resolution data set. Credit: Data from Utah AGRC

    Since geologic time began, Earth’s surface has been evolving through natural processes of tectonic uplift, volcanism, erosion, and the movement of sediment. Now a new force of global change is altering Earth’s surface and morphology in unprecedented ways: humanity.

    Human activities are leaving their fingerprints across Earth (Figure 1), driven by increasing populations, technological capacities, and societal demands [e.g., Ellis, 2015; Brown et al., 2017; Waters et al., 2016]. We have altered flood patterns, created barriers to runoff and erosion, funneled sedimentation into specific areas, flattened mountains, piled hills, dredged land from the sea, and even triggered seismic activity [Tarolli and Sofia, 2016]. These and other changes can pose broad threats to the sustainability of human societies and environments.

    If increasingly globalized societies are to make better land management decisions, the geosciences must globally evaluate how humans are reshaping Earth’s surface. A comprehensive mapping of human topographic signatures on a planet-wide scale is required if we are to understand, model, and forecast the geological hazards of the future.

    Understanding and addressing the causes and consequences of anthropogenic landform modifications are a worldwide challenge. But this challenge also poses an opportunity to better manage environmental resources and protect environmental values [DeFries et al., 2012].

    The Challenge of Three Dimensions

    “If life happens in three dimensions, why doesn’t science?” This question, posed more than a decade ago in Nature [Butler, 2006], resonates when assessing human reshaping of Earth’s landscapes.

    Landforms are shaped in three dimensions by natural processes and societal demands [e.g., Sidle and Ziegler, 2012; Guthrie, 2015]; societies in turn are shaped by the landscapes they alter. Understanding and modeling these interacting forces across Earth are no small challenge.

    For example, observing and modeling the direct effects of some of the most widespread forms of human topographic modification, such as soil tillage and terracing [Tarolli et al., 2014], are possible only with very fine spatial resolutions (i.e., ≤1 meter). Yet these features are common all over the world. High-resolution three-dimensional topographic data at global scales are needed to observe and appraise them.

    The Need for a Unified, Global Topographic Data Set

    High-resolution terrain data such as lidar [Tarolli, 2014], aerial photogrammetry [Eltner et al., 2016], and satellite observations [Famiglietti et al., 2015] are increasingly available to the scientific community. These data sets are also becoming available to land planners and the public, as governments, academic institutions, and others in the remote sensing community seize the opportunity for high-resolution topographic data sharing (Figure 2) [Wulder and Coops, 2014; Verburg et al., 2015]

    2
    Fig. 2. High-resolution geodata reveal the topographic fingerprints of humanity: (a) terraces in the Philippines, (b) agricultural practices in Germany, and (c) roads in Antarctica. The bottom images are lidar images of the same landscapes. Credit: Data from University of the Philippines TCAGP/Freie und Hansestadt Hamburg/Noh and Howat [2015]. Top row: © Google, DigitalGlobe

    Thanks to these geodata, anthropogenic signatures are widely observable across the globe, under vegetation cover (Figure 2a), at very fine spatial scales (e.g., agricultural practices and plowing; Figure 2b) and at large spatial scales (e.g., major open pit mines; Figure 3), and far from contemporary human settlements (Figure 2c). So the potential to assess the global topographic fingerprints of humanity using high-resolution terrain data is a tantalizing prospect.

    However, despite a growing number of local projects at fine scales, a global data set remains nonetheless elusive. This lack of global data is largely the result of technical challenges to sharing very large data sets and issues of data ownership and permissions.

    But once a global database exists, advances in the technical capacity to handle and analyze large data sets could be utilized to map anthropogenic signatures in detail (e.g., using a close-range terrestrial laser scanner) and across larger areas (e.g., using satellite data). Together with geomorphic analyses, the potential is clear for an innovative, transformative, and global-scale assessment of the extent to which humans shape Earth’s landscapes.

    For example, a fine-scale analysis of terrain data can detect specific anthropogenic configurations in the organization of surface features (Figure 3b) [Sofia et al., 2014], revealing modifications that humans make across landscapes (Figure 3c). Such fine-scale geomorphic changes are generally invisible to coarser scales of observation and analysis, making it appear that natural landforms and natural hydrological and sedimentary processes are unaltered. Failure to observe such changes misrepresents the true extent and form of human modifications of terrain, with huge consequences when inaccurate data are used to assess risks from runoff, landslides, and other geologic hazards to society [Tarolli, 2014].

    3
    Fig. 3. This potential detection of anthropogenic topographic signatures has been derived from satellite data. (a) This satellite image shows an open-pit mine in North Korea. (b) That image has been processed in an autocorrelation analysis, a measure of the organization of the topography (slope local length of autocorrelation, SLLAC [Sofia et al., 2014]). The variation in the natural landscape is noisy (e.g., top right corner), whereas anthropogenic structures are more organized and leave a clear topographic signature. (c) The degree of landscape organization can be empirically related to the amount of human-made alterations to the terrain, as demonstrated by Sofia et al. [2014]. Credit: Data from CNES© Distribution Airbus DS

    Topography for Society

    A global map of the topographic signatures of humanity would create an unparalleled opportunity to change both scientific and public perspectives on the human role in reshaping Earth’s land surface. A worldwide inventory of anthropogenic geomorphologies would enable geoscientists to assess the extent to which human societies have reshaped geomorphic processes globally and provide a tool for monitoring these changes over time.

    Such monitoring would facilitate unprecedented insights into the dynamics and sensitivity of landscapes and their responses to human forcings at global scale. In turn, these insights would help cities, resource managers, and the public better understand and mediate their social and environmental actions.

    As we move deeper into the Anthropocene, a comprehensive mapping of human topographic signatures will be increasingly necessary to understand, model, and forecast the geological hazards of the future. These hazards will likely be manifold.

    4
    Fig. 4. (a) This road, in the HJ Andrews Experimental Forest in Oregon’s Cascade Range, was constructed in 1952. A landslide occurred in 1964, and its scar was still visible in 1994, when the image was acquired. The landslide starts from the road and flows toward the top right corner of the image. (b) An index called the relative path impact index (RPII) [Tarolli et al., 2013] is evaluated here using a lidar data set from 2008. The RPII analyzes the potential water surface flow accumulation based on the lidar digital terrain model, and the index is highest where the flows are increased because of the presence of anthropogenic features. High values beyond one standard deviation (σ) highlight potential road-induced erosion. Credit: Data from NSF LTER, USFS Research, OSU; background image © Google, USGS.

    For example, landscapes across the world face altered flooding regimes in densely populated floodplains, erosion rates associated with road networks, altered runoff and erosion due to agricultural practices, and sediment release and seismic activity from mining [Tarolli and Sofia, 2016]. Modifications in land use (e.g., urbanization and changes in agricultural practices) alter water infiltration and runoff production, increasing flooding risks in floodplains. Increases in road density cause land degradation and erosion (Figure 4), especially when roads are poorly planned and constructed without well-designed drainage systems, leading to destabilized hillslopes and landslides. Erosion from agricultural fields can exceed rates of soil production, causing soil degradation and reducing crop yields, water quality, and food production. Mining areas, even years after reclamation, can induce seismicity, landslides, soil erosion, and terrain collapse, damaging environments and surface structures.

    Without accurate data on anthropogenic topography, communities will find it difficult to develop and implement strategies and practices aimed at reducing or mitigating the social and environmental impacts of anthropogenic geomorphic change.

    Earth Science Community’s Perspective Needed

    Technological advances in Earth observation have made possible what might have been inconceivable just a few years ago. A global map and inventory of human topographic signatures in three dimensions at high spatial resolution can now become a reality.

    Collecting and broadening access to high spatial resolution (meter to submeter scale), Earth science–oriented topography data acquired with lidar and other technologies would promote scientific discovery while fostering international interactions and knowledge exchange across the Earth science community. At the same time, enlarging the search for humanity’s topographical fingerprints to the full spectrum of environmental and cultural settings across Earth’s surface will require a more generalized methodology for discovering and assessing these signatures.

    These two parallel needs are where scientific efforts should focus. It is time for the Earth science community to come together and bring the topographic fingerprints of humanity to the eyes and minds of the current and future stewards, shapers, curators, and managers of Earth’s land surface.
    Acknowledgments

    Data sets for Figure 1 are from Utah Automated Geographic Reference Center (AGRC), Geospatial Information Office. Data sets for Figures 2(a)–2(c) are from the University of the Philippines Training Center for Applied Geodesy and Photogrammetry (TCAGP), Noh and Howat [2015], and Freie und Hansestadt Hamburg (from 2014), respectively. Data sets for Figure 3 are from Centre National d’Études Spatiales (CNES©), France, Distribution Airbus DS. Data sets for Figure 4 are from the HJ Andrews Experimental Forest research program, National Science Foundation’s Long-Term Ecological Research Program (NSF LTER, DEB 08-23380), U.S. Forest Service (USFS) Pacific Northwest Research Station, and Oregon State University (OSU).
    References

    Butler, D. (2006), Virtual globes: The web-wide world, Nature, 439, 776–778, https://doi.org/10.1038/439776a.

    Brown, A. G., et al. (2017), The geomorphology of the Anthropocene: Emergence, status and implications, Earth Surf. Processes Landforms, 42, 71–90, https://doi.org/10.1002/esp.3943.

    DeFries, R. S., et al. (2012), Planetary opportunities: A social contract for global change science to contribute to a sustainable future, BioScience, 62, 603–606, https://doi.org/10.1525/bio.2012.62.6.11.

    Ellis, E. C. (2015), Ecology in an anthropogenic biosphere, Ecol. Monogr., 85, 287–331, https://doi.org/10.1890/14-2274.1.

    Eltner, A., et al. (2016), Image-based surface reconstruction in geomorphometry—Merits, limits and developments, Earth Surf. Dyn., 4, 359–389, https://doi.org/10.5194/esurf-4-359-2016.

    Famiglietti, J. S., et al. (2015), Satellites provide the big picture, Science, 349, 684–685, https://doi.org/10.1126/science.aac9238.

    Guthrie, R. (2015), The catastrophic nature of humans, Nat. Geosci. 8, 421–422, https://doi.org/10.1038/ngeo2455.

    Noh, M. J., and I. M. Howat (2015), Automated stereo-photogrammetric DEM generation at high latitudes: Surface Extraction with TIN-based Search-space Minimization (SETSM) validation and demonstration over glaciated regions, GIScience Remote Sens., 52(2), 198–217, https://doi.org/10.1080/15481603.2015.1008621.

    Sidle, R. C., and A. D. Ziegler (2012), The dilemma of mountain roads, Nat. Geosci, 5, 437–438, https://doi.org/10.1038/ngeo1512.

    Sofia, G., F. Marinello, and P. Tarolli (2014), A new landscape metric for the identification of terraced sites: The slope local length of auto-correlation (SLLAC), ISPRS J. Photogramm. Remote Sens., 96, 123–133, https://doi.org/10.1016/j.isprsjprs.2014.06.018.

    Tarolli, P. (2014), High-resolution topography for understanding Earth surface processes: Opportunities and challenges, Geomorphology, 216, 295–312, https://doi.org/10.1016/j.geomorph.2014.03.008.

    Tarolli, P., and G. Sofia (2016), Human topographic signatures and derived geomorphic processes across landscapes, Geomorphology, 255, 140–161, https://doi.org/10.1016/j.geomorph.2015.12.007.

    Tarolli, P., et al. (2013), Recognition of surface flow processes influenced by roads and trails in mountain areas using high-resolution topography, Eur. J. Remote Sens., 46, 176–197.

    Tarolli, P., F. Preti, and N. Romano (2014), Terraced landscapes: From an old best practice to a potential hazard for soil degradation due to land abandonment, Anthropocene, 6, 10–25, https://doi.org/10.1016/j.ancene.2014.03.002.

    Verburg, P. H., et al. (2015), Land system science and sustainable development of the Earth system: A global land project perspective, Anthropocene, 12, 29–41, https://doi.org/10.1016/j.ancene.2015.09.004.

    Waters, C. N., et al. (2016), The Anthropocene is functionally and stratigraphically distinct from the Holocene, Science, 351, aad2622, https://doi.org/10.1126/science.aad2622.

    Wulder, M. A., and N. C. Coops (2014), Satellites: Make Earth observations open access, Nature, 513, 30–31, https://doi.org/10.1038/513030a.

    —Paolo Tarolli (email: paolo.tarolli@unipd.it; @TarolliP) and Giulia Sofia (@jubermensch2), Department of Land, Environment, Agriculture, and Forestry, University of Padova, Legnaro, Italy; and Erle Ellis (@erleellis), Department of Geography and Environmental Systems, University of Maryland, Baltimore County, Baltimore
    Citation: Tarolli, P., G. Sofia, and E. Ellis (2017), Mapping the topographic fingerprints of humanity across Earth, Eos, 98, https://doi.org/10.1029/2017EO069637. Published on 16 March 2017.
    © 2017. The authors. CC BY-NC-ND 3.0

    See the full article here .

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  • richardmitnick 10:46 am on March 8, 2017 Permalink | Reply
    Tags: AGU, , California Fault System Could Produce Magnitude 7.3 Quake, , , Newport-Inglewood/Rose Canyon fault mostly offshore but never more than four miles from the San Diego Orange County and Los Angeles County coast,   

    From Eos: “California Fault System Could Produce Magnitude 7.3 Quake” 

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    Mar 7, 2017

    A new study finds rupture of the offshore Newport-Inglewood/Rose Canyon fault that runs from San Diego to Los Angeles is possible.

    1
    A Scripps research vessel tows a hydrophone array used to collect high-resolution bathymetric to better understand offshore California faults. Credit: Scripps Institution of Oceanography, UC San Diego

    A fault system that runs from San Diego to Los Angeles is capable of producing up to magnitude 7.3 earthquakes if the offshore segments rupture and a 7.4 if the southern onshore segment also ruptures, according to a new study led by Scripps Institution of Oceanography at the University of California San Diego.

    The Newport-Inglewood and Rose Canyon faults had been considered separate systems but the study shows that they are actually one continuous fault system running from San Diego Bay to Seal Beach in Orange County, then on land through the Los Angeles basin.

    “This system is mostly offshore but never more than four miles from the San Diego, Orange County, and Los Angeles County coast,” said study lead author Valerie Sahakian, who performed the work during her doctorate at Scripps and is now a postdoctoral fellow with the U.S. Geological Survey in Menlo Park, California. “Even if you have a high 5- or low 6-magnitude earthquake, it can still have a major impact on those regions which are some of the most densely populated in California.”

    The new study was accepted for publication in the Journal of Geophysical Research: Solid Earth, a journal of the American Geophysical Union.

    In the new study, researchers processed data from previous seismic surveys and supplemented it with high-resolution bathymetric data gathered offshore by Scripps researchers between 2006 and 2009 and seismic surveys conducted aboard former Scripps research vessels New Horizon and Melville in 2013. The disparate data have different resolution scales and depth of penetration providing a “nested survey” of the region. This nested approach allowed the scientists to define the fault architecture at an unprecedented scale and thus to create magnitude estimates with more certainty.

    2
    Locations of NIRC fault zone as observed in seismic profiles. Credit: AGU/Journal of Geophysical Research: Solid Earth

    They identified four segments of the strike-slip fault that are broken up by what geoscientists call stepovers, points where the fault is horizontally offset. Scientists generally consider stepovers wider than three kilometers more likely to inhibit ruptures along entire faults and instead contain them to individual segments—creating smaller earthquakes. Because the stepovers in the Newport-Inglewood/Rose Canyon (NIRC) fault are two kilometers wide or less, the Scripps-led team considers a rupture of all the offshore segments is possible, said Neal Driscoll, a geophysicist at Scripps and co-author of the new study.

    The team used two estimation methods to derive the maximum potential a rupture of the entire fault, including one onshore and offshore portions. Both methods yielded estimates between magnitude 6.7 and magnitude 7.3 to 7.4.

    The fault system most famously hosted a 6.4-magnitude quake in Long Beach, California that killed 115 people in 1933. Researchers have found evidence of earlier earthquakes of indeterminate size on onshore portions of the fault, finding that at the northern end of the fault system, there have been between three and five ruptures in the last 11,000 years. At the southern end, there is evidence of a quake that took place roughly 400 years ago and little significant activity for 5,000 years before that.

    Driscoll has recently collected long sediment cores along the offshore portion of the fault to date previous ruptures along the offshore segments, but the work was not part of this study.

    “Further study is warranted to improve the current understanding of hazard and potential ground shaking posed to urban coastal areas from Tijuana to Los Angeles from the NIRC fault,” the study concludes.

    See the full article here .

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  • richardmitnick 10:18 am on February 20, 2017 Permalink | Reply
    Tags: AGU, , , The Real Surprise Behind the 3rd Hottest January on Record   

    From AGU: “The Real Surprise Behind the 3rd Hottest January on Record” 

    AGU bloc

    American Geophysical Union

    18 February 2017
    Dan Satterfield

    1
    https://data.giss.nasa.gov/gistemp/news/20170215/
    The planet’s temperature oscillates a little, between El Nino events and La Nina events. El Nino’s warm the planet a few tenths of a degree, while La Nina events cool it by about that much. The stronger the event the bigger the effect, so a strong El Nino makes it more likely that we will see a new hottest month on record, while a strong La Nina makes that more unlikely.

    2
    All of this is happening as the Earth steadily warms due to the increasing greenhouse gases, and that makes the past few month’s global temp. report so interesting. We’ve had a La Nina over the past few months and it has just now faded away. In spite of that, January was the third hottest month on record. We are now seeing hotter global temperatures during La Nina events than we did in El Nino events in the past. This January was notably warmer than the January of the super El Nino of 1997-98!

    The graphic below (courtesy of Climate Central) shows the up and down of El Nino/La Nina years and the steady rise of global temps. due to the increasing greenhouse gases. Despite what the head of the EPA may think, there is no scientific doubt about this. The only other explanation is the energy received from the sun or changes in the planet’s reflectivity. Research shows that air pollution, however, is blocking enough of the sun’s energy to slow down some of the greenhouse warming. You may hear skeptics talk about the Earth going through “cycles” and it does. Orbital changes over thousands of years, do indeed change our incoming radiation (that’s where ice ages come from), but we know enough to rule out everything but the greenhouse gases. We know where the warming is coming from.

    It’s not El Nino, and it’s not some unknown cycle.
    It’s us.

    The current radiation balance of the planet is shown below. I’ve posted this before but it’s really worth a hard look.

    3
    From Hansen 2011. Click image for the paper. Also see here.

    See the full article here .

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    The purpose of the American Geophysical Union is to promote discovery in Earth and space science for the benefit of humanity.

    To achieve this mission, AGU identified the following core values and behaviors.

    Core Principles

    As an organization, AGU holds a set of guiding core values:

    The scientific method
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    When we are at our best as an organization, we embody these values in our behavior as follows:

    We advance Earth and space science by catalyzing and supporting the efforts of individual scientists within and outside the membership.
    As a learned society, we serve the public good by fostering quality in the Earth and space science and by publishing the results of research.
    We welcome all in academic, government, industry and other venues who share our interests in understanding the Earth, planets and their space environment, or who seek to apply this knowledge to solving problems facing society.
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    Individual scientists worldwide are equals in all AGU activities.
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  • richardmitnick 2:16 pm on February 18, 2017 Permalink | Reply
    Tags: AGU, , , , , Hall electric field, kinetic Alfvén waves,   

    From AGU Eos: “Plasma Waves Pinpointed at the Site of Magnetic Reconnection” This is Really Cool 

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    17 February 2017
    Mark Zastrow

    NASA/MMS

    nasa-mms-satellites
    An artist’s illustration of the four NASA MMS spacecraft, flying in formation through the fringes of Earth’s magnetic field. Credit: NASA

    Some of the most mysterious physics in all of space occurs tens of thousands of kilometers above the Earth, where the Sun’s magnetic field merges with that of Earth. This region pulses with currents and fields as the two fields tangle and reconnect, especially during solar storms, when reconnection soars and sends currents surging down into Earth’s magnetic field, causing hazardous geomagnetic storms.

    Scientists have labored for decades to understand what happens here, but in October 2015 they got a significant break: For the first time, a fleet of NASA satellites flew directly through a reconnection event. Now a new study by Dai et al. explains these data further and suggests that one electric field important to reconnection is triggered by a certain type of plasma wave. The work advances our understanding of magnetic reconnection, which is critical to forecasting geomagnetic storms.

    NASA’s Magnetospheric Multiscale (MMS) mission consists of four spacecraft launched in March 2015. Flying in a tight pyramid-shaped formation, they soar through the fringes of Earth’s magnetic field hunting for reconnection sites, taking high-resolution measurements as they fly in and out of the swirling currents and fields.

    One of the most prominent fields that appears during reconnection is the Hall electric field, which points across the boundary of Earth’s magnetic bubble. MMS revealed that this field is caused by the pressure of solar wind ions outside of Earth’s magnetic field pushing against it. The Earth’s magnetic field generates the Hall electric field to balance against the intruding ions.

    Magnetosphere of Earth, original bitmap from NASA. SVG rendering by Aaron Kaase
    Magnetosphere of Earth, original bitmap from NASA. SVG rendering by Aaron Kaase

    But what allows these ions to intrude in the first place? And why only positively charged ions and not electrons, too, which would result in no separation of charge and no electric field? As the authors detail, this change in ion pressure is mathematically related to the vibrations in the magnetic field lines themselves. These vibrations, called kinetic Alfvén waves, are akin to those caused by plucking on a string.

    According to the equations that govern plasma particles, both electrons and ions gyrate around the field lines. But protons have roughly 2000 times the mass of electrons, with a corresponding amount of additional inertia. So although electrons in the solar wind remain tightly coiled around the Sun’s magnetic field lines (typically within a few kilometers), positively charged ions perform gyrations as wide as hundreds of kilometers. This allows them to penetrate farther into regions than electrons. This effect also shows up in the equations for kinetic Alfvén waves, suggesting that these waves trigger the Hall electric field in reconnection events.

    The authors note that kinetic Alfvén wave physics can also explain several other phenomena observed at magnetic reconnection sites, including currents that flow along the magnetic field as well as the formation of additional smaller magnetic fields that run perpendicular to those of the Earth and Sun. In addition, the strength of the Hall electric field relative to these perpendicular magnetic fields happens to be very close to the speed of kinetic Alfvén waves as they propagate along magnetic field lines, strengthening the case that they play an important role in magnetic reconnection. (Geophysical Research Letters, https://doi.org/10.1002/2016GL071044, 2017)

    See the full article here .

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  • richardmitnick 1:43 pm on January 4, 2017 Permalink | Reply
    Tags: AGU, , , , ,   

    From AGU via EOS: “Pinpointing the Trigger Behind Yellowstone’s Last Supereruption” 

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    AGU

    1.4.17
    Aylin Woodward
    aylin.y.woodward.gr@dartmouth.edu

    Geologists suggest that mixing of magma melt pockets could have caused the explosion a little more than 600,000 years ago.

    1
    View of the Grand Canyon of Yellowstone National Park. The canyon walls consist of rhyolitic tuff and lava. Crystals in such tuff may hold clues to magma conditions just prior to Yellowstone’s eruptions. Credit: Steven R. Brantley/USGS

    Yellowstone National Park is renowned for more than just its hot springs and Old Faithful. The area is famous in the volcanology community for being the site of three explosive supereruptions, the last of which was 631,000 years ago.

    2
    Map of the known ashfall boundaries for major eruptions from Yellowstone, with ashfall from the Long Valley Caldera and Mount St. Helens for comparison. Credit: USGS

    During that eruption, approximately 1000 cubic kilometers of rock, dust, and volcanic ash blasted into the sky. Debris rained across the continental United States, spanning a rough triangle that stretches from today’s Canadian border down to California and over to Louisiana. In places, ash reached more than a meter thick.

    “If something like this happened today, it would be catastrophic,” said Hannah Shamloo, a geologist at Arizona State University’s School of Earth and Space Exploration in Tempe. “We want to understand what triggers these eruptions, so we can set up warning systems. That’s the big-picture goal.”

    Now, Shamloo and her coauthor think they’ve found a clue. By examining trace elements in crystals that they found in the volcanic leftovers of Yellowstone’s last supereruption, they might be able to pinpoint what triggered it.

    Outer Rims

    Just outside Yellowstone National Park is a thick multicolored, multilayered rock formation called the Lava Creek Tuff. Tuffs are igneous rocks formed by the volcanic debris left behind by an explosive eruption.

    Minerals in these tuffs can tell scientists about conditions inside the volcano before it erupted, and identifying these preeruptive conditions may help inform current hazard assessments.

    3
    Arizona State University’s Christy Till points at an ash layer within the Lava Creek Tuff at the study site near Flagg Ranch, Wyo., just south of the Yellowstone boundary. Samples from this site are giving scientists information on what might have triggered Yellowstone’s most recent supereruption. Credit: Hannah Shamloo

    Shamloo and her Ph.D. adviser at Arizona State University, geologist Christy Till, examined two crystals of feldspar that they found embedded in the tuff. These crystals, called phenocrysts, form as magma cools slowly beneath the volcano.

    These phenocrysts, measuring between 1 and 2 millimeters in diameter, were too large to have formed when hot material was flung up during the eruption.

    Instead, as Shamloo explained, they grew gradually over time in Yellowstone’s magma chamber, each crystal beginning with a core that slowly and steadily enlarged outward, layer upon layer. As surrounding magma conditions—temperature, pressure, and water content— changed, trace elements surrounding the growing phenocrysts also changed and became incorporated into subsequent layers.

    In this way, the differences in chemical composition between the phenocryst core and successive layers serve as a map of changing conditions deep within the volcano over time. What’s more, the phenocrysts’ outermost rims represent the magma that surrounded the crystal right before Yellowstone erupted.

    Thus, by analyzing the outer rims, Shamloo and Till could gather both temperature and trace element information just prior to the massive explosion.

    Bubble, Bubble, Toil and Trouble

    5
    Feldspar phenocrysts from the Lava Creek Tuff. The outermost layers, which contain tiny bits of glass, are to the left. The phenocryst may be a fraction of a larger crystal that grew within the magma chamber or may have adhered to a different crystal on the right, explaining why layers are roughly vertical rather than concentric. Red represents the path of an electron microprobe, which cut through layers to collect chemical compositions. Credit: Hannah Shamloo

    Temperature information locked in a phenocryst’s outer rims can be extracted using a technique called feldspar thermometry. The technique relies on the fact that certain minerals vary their compositions in known ways as temperatures change. Thus, scientists can work backward from the exact compositions of minerals present in these outer rims to estimate the surrounding temperature when the crystal rim formed.

    The duo found signatures in the rims that point to an increase in temperature and uptick in the element barium in the magma just before the eruption. They presented their research on 13 December at the American Geophysical Union’s Fall Meeting in San Francisco, Calif.

    To verify their layer by layer analysis of temperature and chemical composition, Shamloo and Till used MELTS, a software program that models how the crystal composition changed as a function of temperature, pressure, and water content in the magma chamber. They assumed that the magma had the same bulk composition as the Lava Creek Tuff. Their results and the model agreed well but pointed to a low water content for the magma chamber involved in the recent supereruption. In contrast, an older eruption from Yellowstone that produced the Bishop Tuff had 5% water by weight, 5 times more than the one that produced the Lava Creek Tuff.

    The low water content is surprising, Shamloo explained, because water and steam create pressures that can trigger eruptions. But Shamloo said that the phenocrysts’ story of hotter temperatures and more barium in the magma chamber just prior to the eruption suggests a possible culprit behind the explosion: the mixing of neighboring pockets of semimelted magma, called an injection event. “There are multiple ways to trigger an eruption, but as of now, we’re seeing evidence for a magma injection,” she said.

    Magma, molten or semimolten rock that exists in layers of the Earth’s crust, can also reach the Earth’s surface. Because it is less dense than surrounding rocks, magma can move upward through cracks in the Earth’s crust, but when its motion is stymied, it pools into magma chambers. These chambers expand thanks to magma injections, when hotter material from deeper volcanic reservoirs feeds into shallower ones. This injection of hotter material just before the eruption may explain the temperature increase recorded in the phenocrysts.

    But the presence of barium in the phenocrysts is a smoking gun, said Shamloo. “Barium doesn’t like to be in the crystal. It likes to hang out in the melt, so this tells us the barium must’ve been introduced from a different source.” The duo thinks this source is a deeper reservoir inside the volcano.

    Eric Christiansen, a volcanologist from Brigham Young University in Provo, Utah, who was not involved with the study, was skeptical of Shamloo’s use of the MELTS software and thinks this type of modeling isn’t as reliable as “real experiments with real rocks.” However, he asserted, “her work is sound, and her analysis is solid. She’s got interesting trace element data with the barium, a late addition to the chamber, which suggests it accompanies what triggered the eruption.”

    Geologic Crystal Ball

    “The public is always afraid of the ‘next big one,’” Shamloo said. “And I like to ask, ‘Can we really forecast that?’” Shamloo and Till hope that they can.

    Knowing the eruption trigger is just the first step, according to Shamloo. The next step is understanding what order of time—days, months, even years—these changes can take before an eruption like the one that produced the Lava Creek Tuff.

    Such information could help Shamloo, Till, and others to correctly read signs of volcanic unrest at Yellowstone and to create a model for predicting future supereruptions.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Eos is the leading source for trustworthy news and perspectives about the Earth and space sciences and their impact. Its namesake is Eos, the Greek goddess of the dawn, who represents the light shed on understanding our planet and its environment in space by the Earth and space sciences.

     
  • richardmitnick 1:35 pm on August 24, 2016 Permalink | Reply
    Tags: AGU, , , Kleine Gaisl: a large rockfall in the Italian Dolomites   

    From AGU: “Kleine Gaisl: a large rockfall in the Italian Dolomites” 

    AGU bloc

    American Geophysical Union

    23 August 2016
    Posted by dr-dave

    Kleine Gaisl rockfall

    Kleine Gaisl (Piccola Croda Rossa), is a large (2859 m) mountain in the Braies Valley in the South Tyrol in the northern Italian Dolomites. At the end of last week a large rockfall occurred in a series of stages over two days between 18th and 20th August. There is a good report on Planet Mountain, although they have the volume wrong by three orders of magnitude. From other sources the estimated volume is 600,000 to 700,000 cubic metres.

    Mountain guide Roman Valentini captured a part of the rockfall in a video that has been uploaded to Youtube. But note that this is not the main collapse event, as Planet Mountain notes:

    “The footage below was filmed by Roman Valentini, a mountain guide working for Alta Badia Guides, who was in the area on Thursday, August 18 at around 12:30. Although this is only the first, smaller part of the landslide, Valentini told planetmountain.com “It was ‘spectacular’ … I’ve never seen anything quite like it. It looked like a river in spate, with rocks half the size of houses tumbling down.”

    Although the main rockfall event occurred later (the seismic data will be interesting here in order to understand the sequence of events), there is a significant collapse event at about three minutes into the video:

    The rockfall had been anticipated as a large tension crack had been observed prior to the collapse event. Stol.it has a nice article, in German, though Google Translate does a good job, that includes an interview with the Deputy Mayor, Erwin Steiner, which also includes this good image of the source area of the rockfall:

    2
    The rockfall scar on Kleine Gaisl, image by Erwin Steiner

    Whilst another article on the same site has another view of the source zone that also captures some of the rockfall deposit::

    4
    Image of the Kleine Gaisl rockfall zone, including a part of the deposit. Image by Tourismusbüro Prags

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The purpose of the American Geophysical Union is to promote discovery in Earth and space science for the benefit of humanity.

    To achieve this mission, AGU identified the following core values and behaviors.

    Core Principles

    As an organization, AGU holds a set of guiding core values:

    The scientific method
    The generation and dissemination of scientific knowledge
    Open exchange of ideas and information
    Diversity of backgrounds, scientific ideas and approaches
    Benefit of science for a sustainable future
    International and interdisciplinary cooperation
    Equality and inclusiveness
    An active role in educating and nurturing the next generation of scientists
    An engaged membership
    Unselfish cooperation in research
    Excellence and integrity in everything we do

    When we are at our best as an organization, we embody these values in our behavior as follows:

    We advance Earth and space science by catalyzing and supporting the efforts of individual scientists within and outside the membership.
    As a learned society, we serve the public good by fostering quality in the Earth and space science and by publishing the results of research.
    We welcome all in academic, government, industry and other venues who share our interests in understanding the Earth, planets and their space environment, or who seek to apply this knowledge to solving problems facing society.
    Our scientific mission transcends national boundaries.
    Individual scientists worldwide are equals in all AGU activities.
    Cooperative activities with partner societies of all sizes worldwide enhance the resources of all, increase the visibility of Earth and space science, and serve individual scientists, students, and the public.
    We are our members.
    Dedicated volunteers represent an essential ingredient of every program.
    AGU staff work flexibly and responsively in partnership with volunteers to achieve our goals and objectives.

     
  • richardmitnick 11:32 am on June 30, 2016 Permalink | Reply
    Tags: AGU, , , Rare earth metals and their origins   

    From AGU: “New study questions source of rare Earth metals that provide clues to life’s origins” 

    AGU bloc

    American Geophysical Union

    15 June 2016 [This just showed up in social media.]
    Lauren Lipuma

    1
    Artist’s depiction of a collision between two planetary bodies. Such an impact between Earth and a Mars-sized object called Theia likely formed the Moon. New research revives the debate about whether this impact is be the source of rare Earth metals. Credit: NASA/JPL-Caltech.

    A new study is reviving a decades-old debate about how Earth’s rarest elements came to exist on our planet – theories that have implications for the origin of life.

    Most scientists agree the precious metals – gold and the six platinum group elements – were added to Earth’s surface sometime after it formed 4.5 billion years ago. In the late 1980s, scientists debated how this happened. Some thought these elements were added to the Earth’s mantle and crust by countless asteroid impacts during the Late Heavy Bombardment 4 billion years ago, while others believed they came from the collision of Earth and Theia, a planetary body the size of Mars, which spawned our moon 20 million to 100 million years after the solar system’s formation.

    After several years of debate, in the early 1990s most researchers decided the evidence pointed toward the Late Heavy Bombardment theory, and the Theia theory fell out of favor.

    Now, a new study argues the collision of Earth and Theia could still be the source of the precious metals, reviving the abandoned theory. Norman Sleep, a geophysicist at Stanford University, performed new calculations to show Theia’s core contained enough material to account for the platinum group elements in Earth’s mantle and showed how oxygen in the planet’s mantle could have helped to keep them there.

    Figuring out these elements’ source and when the impacts took place could help scientists pinpoint when and how life originated on Earth, Sleep said. Whether there was one giant impact or several smaller ones could tell scientists when Earth was first habitable and whether asteroid impacts drove life to the point of extinction, he said.

    “The paper is not intended to be last word on the subject, but rather show that both alternatives still appear to be viable, and that more geochemical work needs to be done,” said Sleep, author of the new paper published today in Geochemistry, Geophysics, Geosystems, a journal of the American Geophysical Union.

    The new study could renew the debate about which theory is correct, said Rebecca Fischer, a geophysicist at the Smithsonian National Museum of Natural History who was not involved in the study.

    “[He does] some, for the most part, relatively simple calculations to show that it’s a plausible theory,” Fischer said. “I’m not sure if I’m 100 percent convinced yet, but it’s certainly making me think harder about this.”

    Two theories

    The precious metals are among the rarest on Earth. These metals dissolve in iron and were sucked into Earth’s molten iron core when the planet formed. However, scientists discovered these elements also exist in Earth’s mantle. The platinum group elements exist in the mantle in roughly the same ratios relative to each other as they do in meteorites. This observation led researchers to believe meteors or other foreign objects brought the precious metals to Earth’s surface after the planet formed.

    Two theories emerged in the late 1980s to explain how Earth acquired the precious metals and the rocky debris in which they are found, called the “late veneer.” The Late Heavy Bombardment theory argued the veneer came from asteroid impacts occurring over a few hundred million years. Earth’s mantle has more precious metals than the moon’s, leading proponents of the Late Heavy Bombardment theory to deduce that during this time a small number of large asteroids hit Earth but missed the moon, rather than a large number of smaller asteroids that hit both Earth and the moon.

    The Theia theory argued the late veneer material came from Theia’s iron core, which sucked in its own share of platinum group elements during its formation. The impact of Theia and Earth would have allowed Theia’s core to mix with Earth’s mantle, but the material would not have made it all the way to the Earth’s core.

    In the new study, Sleep analyzed estimates of Theia’s size and iron content to see if these parameters could account for the iron concentrations in the present Earth and moon. He also determined how likely it was that large asteroids could hit Earth while missing the moon during the Late Heavy Bombardment and determined how large such impacts would have to be in order to account for the amounts of precious metals Earth’s mantle has today.

    The study shows the amount of iron in Theia’s core could sufficiently account for the platinum group elements in Earth’s mantle and for the iron in the moon’s core. Sleep also shows there was excess oxygen in Earth’s mantle at the time of Theia’s impact. This oxygen combined with iron from Theia’s core when it collided with Earth. While chemically bound to oxygen, the iron could not dissolve the platinum group elements and pull them into the new Earth’s core, and so they remained in the mantle.

    According to Sleep, his calculations support both theories, but he tends to lean toward believing the core of Theia theory.

    The origin of life

    The origin of Earth’s veneer material has implications for when life first evolved on Earth, according to Sleep and Fischer.

    “If the Earth got its late veneer from several large impactors during the Late Heavy Bombardment, if life had already evolved at that point, these impacts could have killed it off,” Fischer said. Or, alternatively, the impacts could have killed most existing life but left only those organisms adapted to extreme heat environments, such as bacteria that live in hydrothermal vents, she said.

    If asteroid impacts rendered Earth uninhabitable for a long while, it could be more plausible that life first originated on Mars, Sleep said. During the Late Heavy Bombardment, asteroids could have knocked rocks off of Mars and brought them to Earth, he said.

    But if the late veneer came from the moon-forming Theia impact, large asteroid impacts during the Late Heavy Bombardment may have been smaller and less destructive than assumed, according to Sleep. If the moon-forming impact was the only impact large enough to sterilize the planet, Earth could have been habitable much sooner and for longer than previously thought, he said.

    See the full post here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The purpose of the American Geophysical Union is to promote discovery in Earth and space science for the benefit of humanity.

    To achieve this mission, AGU identified the following core values and behaviors.

    Core Principles

    As an organization, AGU holds a set of guiding core values:

    The scientific method
    The generation and dissemination of scientific knowledge
    Open exchange of ideas and information
    Diversity of backgrounds, scientific ideas and approaches
    Benefit of science for a sustainable future
    International and interdisciplinary cooperation
    Equality and inclusiveness
    An active role in educating and nurturing the next generation of scientists
    An engaged membership
    Unselfish cooperation in research
    Excellence and integrity in everything we do

    When we are at our best as an organization, we embody these values in our behavior as follows:

    We advance Earth and space science by catalyzing and supporting the efforts of individual scientists within and outside the membership.
    As a learned society, we serve the public good by fostering quality in the Earth and space science and by publishing the results of research.
    We welcome all in academic, government, industry and other venues who share our interests in understanding the Earth, planets and their space environment, or who seek to apply this knowledge to solving problems facing society.
    Our scientific mission transcends national boundaries.
    Individual scientists worldwide are equals in all AGU activities.
    Cooperative activities with partner societies of all sizes worldwide enhance the resources of all, increase the visibility of Earth and space science, and serve individual scientists, students, and the public.
    We are our members.
    Dedicated volunteers represent an essential ingredient of every program.
    AGU staff work flexibly and responsively in partnership with volunteers to achieve our goals and objectives.

     
  • richardmitnick 11:47 am on June 23, 2016 Permalink | Reply
    Tags: AGU, Dr. Annalisa Bracco, The Thrill of Predictability,   

    From AGU: Women in Science – “The Thrill of Predictability” Dr. Annalisa Bracco 

    AGU bloc

    American Geophysical Union

    23 June 2016
    Mónika Naranjo González

    1
    Dr. Annalisa Bracco. Image credit: SOI/Monika Naranjo Gonzalez

    There are those who argue that predictability is the greatest gift of progress, the biggest merit of civilization. Our ability to explain nature through science makes the world and the universe predictable and understandable. That enables us to have a more informed and productive relationship with our natural environment and its resources.

    This is at the heart of physical oceanographer Dr. Annalisa Bracco’s work. The first project she participated in as a graduate student proved how the planets are formed, a contribution for which she is still widely quoted today. After starting her career on such a high note, what could she follow with? She was born in Italy, surrounded by the Mediterranean Sea, so the decision came naturally for her: she was going to focus on the ocean.

    Annalisa is a modeller, which means she creates mathematical scenarios in order to explain physical processes. She examines nature, interprets the physical reasons behind its operations, translates these into equations and formulas producing likely scenarios and results, and then waits for real-life observations that either support or dismiss what her models suggest.

    Her work today deals with how ocean circulation transports and mixes microbial life and chemicals. With this understanding, she can then study how those physical processes affect our climate, biodiversity and evolution. One equation at a time, she turns the oceans into more predictable landscapes.

    Computational Processing Power

    2
    Even a simple equation explaining mass evolution in oceanic waters seem very complex. Credit: SOI/Monika Naranjo Gonzalez

    Annalisa uses an equation that deals with the evolution of mass in oceanic waters. She explains how the variables (velocity and space in its x and y axis) relate to each other and how the result – if the system is stable – should be equal to zero. If you don’t get zero, you start getting convergence. From there, things get very complicated, very quickly for the untrained listener. There is no reason to feel bad about not understanding, because even supercomputers can not deal with such complex calculations. There is no computer that can run them at a global scale (or even at the microscopic scale either).

    Annalisa has no choice but to break the system into pieces. For instance, she knows that here convergence (when water with different densities merge, such as when fresh and salty water meet) occurs in radii of 1km and with depths of around 100 meters. Some 15 years ago scientists did not think such small scales could have a real impact in the ocean’s composition, but now we know they do. This explains the patchiness we have observed from R/V Falkor while crossing between the ocean’s water to the river’s plume. This also explains why the team has found very different planktonic communities in stations that are not so far apart.

    Our understanding of these physical dynamics is still very limited. Yet, in order to decipher larger planetary workings such as Carbon sequestration by phytoplankton, we need to understand these patches better and extrapolate them into larger scales.

    Riddle Me This

    3
    CTD casts shows sudden changes in salinity and temperature. Credit: SOI

    Several CTD casts show sudden changes in salinity and temperature. Annalisa watches the data come in from the immersed rosette and wonders if she could piece all casts together in an attempt to map the system. As if her daily work was not challenging enough, she now considers how her physics models can intertwine with the work of her fellow scientists on board, who are attempting to characterize the vast microbiological diversity that R/V Falkor is uncovering.

    It will not be easy since the South China Sea combines three unique factors: riverine input, upwelling and heavy rains. This mix is what brought her here; the thrill of this system’s idiosyncrasies, the challenge of breaking through them and of predicting such complex behaviour.

    See the full post here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The purpose of the American Geophysical Union is to promote discovery in Earth and space science for the benefit of humanity.

    To achieve this mission, AGU identified the following core values and behaviors.

    Core Principles

    As an organization, AGU holds a set of guiding core values:

    The scientific method
    The generation and dissemination of scientific knowledge
    Open exchange of ideas and information
    Diversity of backgrounds, scientific ideas and approaches
    Benefit of science for a sustainable future
    International and interdisciplinary cooperation
    Equality and inclusiveness
    An active role in educating and nurturing the next generation of scientists
    An engaged membership
    Unselfish cooperation in research
    Excellence and integrity in everything we do

    When we are at our best as an organization, we embody these values in our behavior as follows:

    We advance Earth and space science by catalyzing and supporting the efforts of individual scientists within and outside the membership.
    As a learned society, we serve the public good by fostering quality in the Earth and space science and by publishing the results of research.
    We welcome all in academic, government, industry and other venues who share our interests in understanding the Earth, planets and their space environment, or who seek to apply this knowledge to solving problems facing society.
    Our scientific mission transcends national boundaries.
    Individual scientists worldwide are equals in all AGU activities.
    Cooperative activities with partner societies of all sizes worldwide enhance the resources of all, increase the visibility of Earth and space science, and serve individual scientists, students, and the public.
    We are our members.
    Dedicated volunteers represent an essential ingredient of every program.
    AGU staff work flexibly and responsively in partnership with volunteers to achieve our goals and objectives.

     
  • richardmitnick 9:53 pm on May 13, 2016 Permalink | Reply
    Tags: AGU, , , ,   

    From AGU: “Earth’s Atmosphere Passes Significant Carbon Milestone” 

    AGU bloc

    American Geophysical Union

    May 12, 2016
    Dan Satterfield

    1
    The illustration was created by interpolating 20 profiles measured on February 5 and 8, 2016. The vertical axis has been increased for better visibility. Eric Morgan, Scripps Institution of Oceanography.

    Earth’s atmosphere is crossing a major threshold, as high levels of carbon dioxide (CO2)—the leading driver of recent climate change—are beginning to extend even to the globe’s most remote region. Scientists flying near Antarctica this winter captured the moment with airborne CO2 sensors during a field project to better understand the Southern Ocean’s role in global climate.

    This illustration shows the atmosphere near Antarctica in January, just as air masses over the Southern Ocean began to exceed 400 parts per million of CO2. The 400 ppm level is regarded as a milestone by climate scientists, as the last time concentrations of the heat-trapping gas reached such a point was millions of years ago, when temperatures and sea levels were far higher.

    The field project, led by the National Center for Atmospheric Research (NCAR) and known as ORCAS, found that there is still air present in the Southern Hemisphere that has less than 400 ppm of CO2—but just barely. In the north, the atmosphere had first crossed that threshold in 2013, as shown by observations taken at Mauna Loa, Hawaii, by the National Oceanic and Atmospheric Administration and Scripps Institution of Oceanography.

    2
    Image from NOAA/Climate Central

    Most fossil fuels are burned in the Northern Hemisphere, and these emissions take about a year to spread across the equator. As CO2 increases globally, the concentrations in the Southern Hemisphere lag slightly those further north.

    “Throughout humanity, we have lived in an era with CO2 levels below 400 ppm,” said Ralph Keeling, director of the CO2 Program at the Scripps Institution of Oceanography and a principal investigator on ORCAS. “With these data, we see that era drawing to a close, as the curtain of higher CO2 spreads into the Southern hemisphere from the north. There is no sharp climate threshold at 400 ppm, but this milestone is symbolically and psychologically important.”

    The air found by ORCAS with less than 400 ppm of CO2 was located in a wedge at lower altitudes. At higher altitudes, the air had already exceeded 400 ppm. This pattern is mostly a consequence of the way the air circulates in the region. At these southerly latitudes, the air arrives from the Northern Hemisphere at higher elevations and then mixes downward.

    Emissions of CO2 have been increasing since the 19th century.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The purpose of the American Geophysical Union is to promote discovery in Earth and space science for the benefit of humanity.

    To achieve this mission, AGU identified the following core values and behaviors.

    Core Principles

    As an organization, AGU holds a set of guiding core values:

    The scientific method
    The generation and dissemination of scientific knowledge
    Open exchange of ideas and information
    Diversity of backgrounds, scientific ideas and approaches
    Benefit of science for a sustainable future
    International and interdisciplinary cooperation
    Equality and inclusiveness
    An active role in educating and nurturing the next generation of scientists
    An engaged membership
    Unselfish cooperation in research
    Excellence and integrity in everything we do

    When we are at our best as an organization, we embody these values in our behavior as follows:

    We advance Earth and space science by catalyzing and supporting the efforts of individual scientists within and outside the membership.
    As a learned society, we serve the public good by fostering quality in the Earth and space science and by publishing the results of research.
    We welcome all in academic, government, industry and other venues who share our interests in understanding the Earth, planets and their space environment, or who seek to apply this knowledge to solving problems facing society.
    Our scientific mission transcends national boundaries.
    Individual scientists worldwide are equals in all AGU activities.
    Cooperative activities with partner societies of all sizes worldwide enhance the resources of all, increase the visibility of Earth and space science, and serve individual scientists, students, and the public.
    We are our members.
    Dedicated volunteers represent an essential ingredient of every program.
    AGU staff work flexibly and responsively in partnership with volunteers to achieve our goals and objectives.

     
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