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Sample records for high arctic electronic

  1. Coarse mode aerosols in the High Arctic

    Science.gov (United States)

    Baibakov, K.; O'Neill, N. T.; Chaubey, J. P.; Saha, A.; Duck, T. J.; Eloranta, E. W.

    2014-12-01

    Fine mode (submicron) aerosols in the Arctic have received a fair amount of scientific attention in terms of smoke intrusions during the polar summer and Arctic haze pollution during the polar winter. Relatively little is known about coarse mode (supermicron) aerosols, notably dust, volcanic ash and sea salt. Asian dust is a regular springtime event whose optical and radiative forcing effects have been fairly well documented at the lower latitudes over North America but rarely reported for the Arctic. Volcanic ash, whose socio-economic importance has grown dramatically since the fear of its effects on aircraft engines resulted in the virtual shutdown of European civil aviation in the spring of 2010 has rarely been reported in the Arctic in spite of the likely probability that ash from Iceland and the Aleutian Islands makes its way into the Arctic and possibly the high Arctic. Little is known about Arctic sea salt aerosols and we are not aware of any literature on the optical measurement of these aerosols. In this work we present preliminary results of the combined sunphotometry-lidar analysis at two High Arctic stations in North America: PEARL (80°N, 86°W) for 2007-2011 and Barrow (71°N,156°W) for 2011-2014. The multi-years datasets were analyzed to single out potential coarse mode incursions and study their optical characteristics. In particular, CIMEL sunphotometers provided coarse mode optical depths as well as information on particle size and refractive index. Lidar measurements from High Spectral Resolution lidars (AHSRL at PEARL and NSHSRL at Barrow) yielded vertically resolved aerosol profiles and gave an indication of particle shape and size from the depolarization ratio and color ratio profiles. Additionally, we employed supplementary analyses of HYSPLIT backtrajectories, OMI aerosol index, and NAAPS (Navy Aerosol Analysis and Prediction System) outputs to study the spatial context of given events.

  2. High-Arctic butterflies become smaller with rising temperatures

    DEFF Research Database (Denmark)

    Bowden, Joseph James; Eskildsen, Anne; Hansen, Rikke Reisner

    2015-01-01

    size but long growing seasons could also increase body size as was recently shown in an Arctic spider species. Here, we present the longest known time series on body size variation in two High-Arctic butterfly species: Boloria chariclea and Colias hecla. We measured wing length of nearly 4500...... individuals collected annually between 1996 and 2013 from Zackenberg, Greenland and found that wing length significantly decreased at a similar rate in both species in response to warmer summers. Body size is strongly related to dispersal capacity and fecundity and our results suggest that these Arctic...

  3. Methane emissions from a high arctic valley: findings and challenges

    DEFF Research Database (Denmark)

    Mastepanov, Mikhail; Sigsgaard, Charlotte; Ström, Lena

    2008-01-01

    Wet tundra ecosystems are well-known to be a significant source of atmospheric methane. With the predicted stronger effect of global climate change on arctic terrestrial ecosystems compared to lower-latitudes, there is a special obligation to study the natural diversity and the range of possible...... feedback effects on global climate that could arise from Arctic tundra ecosystems. One of the prime candidates for such a feedback mechanism is a potential change in the emissions of methane. Long-term datasets on methane emissions from high arctic sites are almost non-existing but badly needed...... for analyses of controls on interannual and seasonal variations in emissions. To help fill this gap we initiated a measurement program in a productive high arctic fen in the Zackenberg valley, NE Greenland. Methane flux measurements have been carried out at the same location since 1997. Compared...

  4. Fine-scale population genetic structure of arctic foxes (Vulpes lagopus) in the High Arctic.

    Science.gov (United States)

    Lai, Sandra; Quiles, Adrien; Lambourdière, Josie; Berteaux, Dominique; Lalis, Aude

    2017-12-01

    The arctic fox (Vulpes lagopus) is a circumpolar species inhabiting all accessible Arctic tundra habitats. The species forms a panmictic population over areas connected by sea ice, but recently, kin clustering and population differentiation were detected even in regions where sea ice was present. The purpose of this study was to examine the genetic structure of a population in the High Arctic using a robust panel of highly polymorphic microsatellites. We analyzed the genotypes of 210 individuals from Bylot Island, Nunavut, Canada, using 15 microsatellite loci. No pattern of isolation-by-distance was detected, but a spatial principal component analysis (sPCA) revealed the presence of genetic subdivisions. Overall, the sPCA revealed two spatially distinct genetic clusters corresponding to the northern and southern parts of the study area, plus another subdivision within each of these two clusters. The north-south genetic differentiation partly matched the distribution of a snow goose colony, which could reflect a preference for settling into familiar ecological environments. Secondary clusters may result from higher-order social structures (neighbourhoods) that use landscape features to delimit their borders. The cryptic genetic subdivisions found in our population may highlight ecological processes deserving further investigations in arctic foxes at larger, regional spatial scales.

  5. (Arbo)viruses in high European Arctic

    OpenAIRE

    ELSTEROVÁ, Jana

    2016-01-01

    Since an ongoing climate change covers strongly the polar areas. Higher temperatures and related climate parameters bring the emergence of new parasites and their pathogens to higher latitudes. This may influence zoonotic diseases including arthropod-transmitted diseases. The tick species Ixodes uriae, parasitizing seabirds in the Arctic, may transmit many pathogens including various arboviruses, Borrelia spirochetes and Babesia apicomplexans. In the study we diagnosed 89 individuals of seabi...

  6. High Arctic Nitrous Oxide Emissions Found on Large Spatial Scales

    Science.gov (United States)

    Wilkerson, J. P.; Sayres, D. S.; Dobosy, R.; Anderson, J. G.

    2017-12-01

    As the planet warms, greenhouse gas emissions from thawing permafrost can potentially increase the net radiative forcing in our climate structure. However, knowledge about Arctic N2O emissions is particularly sparse. Increasing evidence suggests emissions from permafrost thaw may be a significant natural source of N2O. This evidence, though, is either based on lab experiments or in situ chamber studies, which have extremely limited spatial coverage. Consequently, it has not been confirmed to what extent these high emissions are representative of broader arctic regions. Using an airborne eddy covariance flux technique, we measured N2O fluxes over large regions of Alaska in August 2013. From these measurements, we directly show that large areas of this Arctic region have high N2O emissions.

  7. High-Arctic Plant-Herbivore Interactions under Climate Influence

    DEFF Research Database (Denmark)

    Berg, Thomas B.; Schmidt, Niels M.; Høye, Toke Thomas

    production upon which the herbivores depend, and snow may be the most important climatic factor affecting the different trophic levels and the interactions between them. Hence, the spatio-temporal distribution of snow, as well as thawing events during winter, may have considerable effects on the herbivores...... by both the timing of onset and the duration of winter snow-cover. Musk oxen significantly reduced the productivity of arctic willow, while high densities of collared lemmings during winter reduced the production of mountain averts flowers in the following summer. Under a deep snow-layer scenario, climate...... and the previous year's density of musk oxen had a negative effect on the present year's production of arctic willow. Previous year's primary production of arctic willow, in turn, significantly affected the present year's density of musk oxen positively. Climatic factors that affect primary production of plants...

  8. Arctic Solutions The Frozen (Thawing) Relations of the High North

    Energy Technology Data Exchange (ETDEWEB)

    Summers, Ch.

    2010-07-01

    It's cold, inhospitable and deadly. The image of the Arctic in years past is one of bewilderment, ignorance and awe. How the image of the Arctic has changed in recent years can be directly linked to our recognition that the Arctic has a great deal to offer in meeting the basic needs of future generations. Although we are still in awe of the Arctic's cruel beauty, new technologies are making it easier to explore the once unmanageable environment. The Arctic has moved into the mainstream with a host of suitors jockeying for position in the race to possess the Arctic and all that it contains. To highlight this increased interest, Russia's 'National Security Until 2020' initiative, has upgraded the High North to one of Russia's main priorities and identifies the Arctic as liable to produce military conflict in the future linked to competition for the Arctic's abundant raw materials.1 Even Canada, a peaceful and respectful country, has stepped outside the box of traditional Canadian rhetoric by giving Canada's Northern Strategy a tag line: 'Our North, our heritage, our future'. The Arctic is increasingly viewed as central to meeting the challenges of an ever changing world where climate change and economic benefit drive international agreements and policies. However Canada and Russia are not the only actors here. The other Arctic Five states: Denmark, Norway, and the United States of America all lay claims to some area or activity within the Arctic region. The Arctic is a unique part of this world, one that has been left largely untouched by human hands, and one that is on the brink of being changed forever. To fully understand Arctic issues, resource figures must be taken into account. Every nation involved in the Arctic debate has considered and based its policies on its set of numbers and resource estimates. A U.S. Geological Survey (USGS) in 2009 put Arctic resource figures in the range of thirty percent of the

  9. Arctic Solutions The Frozen (Thawing) Relations of the High North

    International Nuclear Information System (INIS)

    Summers, Ch.

    2010-01-01

    It's cold, inhospitable and deadly. The image of the Arctic in years past is one of bewilderment, ignorance and awe. How the image of the Arctic has changed in recent years can be directly linked to our recognition that the Arctic has a great deal to offer in meeting the basic needs of future generations. Although we are still in awe of the Arctic's cruel beauty, new technologies are making it easier to explore the once unmanageable environment. The Arctic has moved into the mainstream with a host of suitors jockeying for position in the race to possess the Arctic and all that it contains. To highlight this increased interest, Russia's 'National Security Until 2020' initiative, has upgraded the High North to one of Russia's main priorities and identifies the Arctic as liable to produce military conflict in the future linked to competition for the Arctic's abundant raw materials.1 Even Canada, a peaceful and respectful country, has stepped outside the box of traditional Canadian rhetoric by giving Canada's Northern Strategy a tag line: 'Our North, our heritage, our future'. The Arctic is increasingly viewed as central to meeting the challenges of an ever changing world where climate change and economic benefit drive international agreements and policies. However Canada and Russia are not the only actors here. The other Arctic Five states: Denmark, Norway, and the United States of America all lay claims to some area or activity within the Arctic region. The Arctic is a unique part of this world, one that has been left largely untouched by human hands, and one that is on the brink of being changed forever. To fully understand Arctic issues, resource figures must be taken into account. Every nation involved in the Arctic debate has considered and based its policies on its set of numbers and resource estimates. A U.S. Geological Survey (USGS) in 2009 put Arctic resource figures in the range of thirty percent of the remaining world reserves of natural gas and ten percent

  10. Is climate change affecting wolf populations in the high Arctic?

    Science.gov (United States)

    Mech, L.D.

    2004-01-01

    Gobal climate change may affect wolves in Canada's High Arctic (80?? N) acting through three trophic levels (vegetation, herbivores, and wolves). A wolf pack dependent on muskoxen and arctic hares in the Eureka area of Ellesmere Island denned and produced pups most years from at least 1986 through 1997. However, when summer snow covered vegetation in 1997 and 2000 for the first time since records were kept, halving the herbivore nutrition-replenishment period, muskox and hare numbers dropped drastically, and the area stopped supporting denning wolves through 2003. The unusual weather triggering these events was consistent with global-climate-change phenomena. ?? 2004 Kluwer Academic Publishers.

  11. Revisiting factors controlling methane emissions from high-Arctic tundra

    DEFF Research Database (Denmark)

    Mastepanov, M.; Sigsgaard, Charlotte; Tagesson, Håkan Torbern

    2013-01-01

    The northern latitudes are experiencing disproportionate warming relative to the mid-latitudes, and there is growing concern about feedbacks between this warming and methane production and release from high-latitude soils. Studies of methane emissions carried out in the Arctic, particularly those...

  12. Evidence of high-elevation amplification versus Arctic amplification.

    Science.gov (United States)

    Wang, Qixiang; Fan, Xiaohui; Wang, Mengben

    2016-01-12

    Elevation-dependent warming in high-elevation regions and Arctic amplification are of tremendous interest to many scientists who are engaged in studies in climate change. Here, using annual mean temperatures from 2781 global stations for the 1961-2010 period, we find that the warming for the world's high-elevation stations (>500 m above sea level) is clearly stronger than their low-elevation counterparts; and the high-elevation amplification consists of not only an altitudinal amplification but also a latitudinal amplification. The warming for the high-elevation stations is linearly proportional to the temperature lapse rates along altitudinal and latitudinal gradients, as a result of the functional shape of Stefan-Boltzmann law in both vertical and latitudinal directions. In contrast, neither altitudinal amplification nor latitudinal amplification is found within the Arctic region despite its greater warming than lower latitudes. Further analysis shows that the Arctic amplification is an integrated part of the latitudinal amplification trend for the low-elevation stations (≤500 m above sea level) across the entire low- to high-latitude Northern Hemisphere, also a result of the mathematical shape of Stefan-Boltzmann law but only in latitudinal direction.

  13. Source identification of individual soot agglomerates in Arctic air by transmission electron microscopy

    Science.gov (United States)

    Weinbruch, S.; Benker, N.; Kandler, K.; Schütze, K.; Kling, K.; Berlinger, B.; Thomassen, Y.; Drotikova, T.; Kallenborn, R.

    2018-01-01

    Individual soot agglomerates collected at four different locations on the Arctic archipelago Svalbard (Norway) were characterised by transmission electron microscopy and energy-dispersive X-ray microanalysis. For source identification of the ambient soot agglomerates, samples from different local sources (coal burning power plants in Longyearbyen and Barentsburg, diesel and oil burning for power generation in Sveagruva and Ny Ålesund, cruise ship) as well as from other sources which may contribute to Arctic soot concentrations (biomass burning, aircraft emissions, diesel engines) were investigated. Diameter and graphene sheet separation distance of soot primary particles were found to be highly variable within each source and are not suited for source identification. In contrast, concentrations of the minor elements Si, P, K, Ca and Fe showed significant differences which can be used for source attribution. The presence/absence of externally mixed particle groups (fly ashes, tar balls, mercury particles) gives additional hints about the soot sources. Biomass/wood burning, ship emissions and coal burning in Barentsburg can be excluded as major source for ambient soot at Svalbard. The coal power plant in Longyearbyen is most likely a major source of soot in the settlement of Longyearbyen but does not contribute significantly to soot collected at the Global Atmosphere Watch station Zeppelin Mountain near Ny Ålesund. The most probable soot sources at Svalbard are aircraft emissions and diesel exhaust as well as long range transport of coal burning emissions.

  14. Cryostratigraphy and sedimentology of high-Arctic fjord-valleys

    OpenAIRE

    Gilbert, Graham Lewis

    2018-01-01

    Fjord-valleys, as sediment-filled palaeofjords, are characteristic of formerly glaciated mountainous coastal areas. High-Arctic fjord-valleys commonly host permafrost, but are poorly accessible and hence have drawn relatively little research. The research presented in this thesis combines the methods of cryostratigraphy, clastic sedimentology, sequence stratigraphy, geomorphology and geochronology to investigate the sedimentary infilling, permafrost formation and late Quaternary landscape dev...

  15. A new high resolution tidal model in the arctic ocean

    DEFF Research Database (Denmark)

    Cancet, M.; Andersen, Ole Baltazar; Lyard, F.

    The Arctic Ocean is a challenging region for tidal modeling, because of its complex and not well-documented bathymetry, together combined with the intermittent presence of sea ice and the fact that the in situ tidal observations are rather scarce at such high latitudes. As a consequence, the accu......The Arctic Ocean is a challenging region for tidal modeling, because of its complex and not well-documented bathymetry, together combined with the intermittent presence of sea ice and the fact that the in situ tidal observations are rather scarce at such high latitudes. As a consequence......, the accuracy of the global tidal models decreases by several centimeters in the Polar Regions. In particular, it has a large impact on the quality of the satellite altimeter sea surface heights in these regions (ERS1/2, Envisat, CryoSat-2, SARAL/AltiKa and the future Sentinel-3 mission). Better knowledge......-growing maritime and industrial activities in this region. NOVELTIS and DTU Space have developed a regional, high-resolution tidal atlas in the Arctic Ocean, in the framework of the CryoSat Plus for Ocean (CP4O) ESA project. In particular, this atlas benefits from the assimilation of the most complete satellite...

  16. Benthic primary production and mineralization in a High Arctic Fjord

    DEFF Research Database (Denmark)

    Attard, Karl M.; Hancke, Kasper; Sejr, Mikael K.

    2016-01-01

    Coastal and shelf systems likely exert major influence on Arctic Ocean functioning, yet key ecosystem processes remain poorly quantified. We employed the aquatic eddy covariance (AEC) oxygen (O2) flux method to estimate benthic primary production and mineralization in a High Arctic Greenland fjord....... Seabed gross primary production (GPP) within the 40 m deep photic zone was highest at 10 m (29 mmol O2 m−2 d−1) and decreased to 5 mmol O2 m−2 d−1 at 40 m, while nighttime community respiration (CR) ranged from 11 to 25 mmol O2m−2 d−1. CR decreased to ~2.5 mmol O2m−2 d−1 at 80 m and remained constant...... with further depth. Fauna activity accounted for ~50% of the CR at depths ≤60 m but was primary production...

  17. Comparative responses of phenology and reproductive development to simulated environmental change in sub-arctic and high arctic plants

    Energy Technology Data Exchange (ETDEWEB)

    Wookey, P A; Welker, J M; Callaghan, T V [Inst. of Terrestrial Ecology, Merlewood Research Station, Grange-over-Sands, Cumbria (United Kingdom); Parsons, A N; Potter, J A; Lee, J A; Press, M C [Dept. of Environmental Biology, Univ. of Manchester, Manchester (United Kingdom)

    1993-01-01

    The effects of temperature, precipitation and nutrient perturbations, and their interactions, are being assessed on two contrasting arctic ecosystems to simulate impacts of climate change. One, a high arctic polar semi-desert community, is characterized by a sparse, low and aggregated vegetation cover where plant proliferation is by seedlings, whereas the other, a sub-arctic dwarf shrub health, is characterized by a complete, vegetation cover of erect, clonal dwarf shrubs which spread vegetatively. The developmental processes of seed production were shown to be highly sensitive, even within one growing season to specific environmental perturbations which differed between sites. At the polar semi-desert site, there was a striking effect of the temperature enhancement treatments on phenology and seed-setting of Dryas octopetala ssp. octopetala, with almost no seed-setting occurring in plots experiencing ambient temperatures. By contrast, there were no significant effects of temperature enhancement alone on fruit production of Empetrum hermaphroditum at the sub-Arctic dwarf shrub heath site, although fruit production was significantly influenced by the application of nutrients and/or water. The response of dominant high arctic dwarf shrub to increased temperature suggests that any climate warming may stimulate seed-set. This could be particularly important in the high Arctic where colonization can proceed in areas dominated by bare ground and where genetic recombination may be needed to generate tolerance to predicted changes of great magnitude. In the sub-Arctic, however the closed vegetation is dominated by clonally-proliferating species. Plant fitness will increase here in response to any increased vegetative growth resulting from higher nutrient availability in warmer organic soils. (ua) (59 refs.)

  18. Single-particle characterization of the High Arctic summertime aerosol

    Science.gov (United States)

    Sierau, B.; Chang, R. Y.-W.; Leck, C.; Paatero, J.; Lohmann, U.

    2014-01-01

    Single-particle mass spectrometric measurements were carried out in the High Arctic north of 80° during summer 2008. The campaign took place onboard the icebreaker Oden and was part of the Arctic Summer Cloud Ocean Study (ASCOS). The instrument deployed was an Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) that provides information on the chemical composition of individual particles and their mixing state in real-time. Aerosols were sampled in the marine boundary layer at stations in the open ocean, in the marginal ice zone, and in the pack ice region. The largest fraction of particles detected for subsequent analysis in the size range of the ATOFMS between approximately 200 nm to 3000 nm in diameter showed mass spectrometric patterns indicating an internal mixing state and a biomass burning and/or biofuel source. The majority of these particles were connected to an air mass layer of elevated particle concentration mixed into the surface mixed layer from the upper part of the marine boundary layer. The second largest fraction was represented by sea salt particles. The chemical analysis of the over-ice sea salt aerosol revealed tracer compounds that reflect chemical aging of the particles during their long-range advection from the marginal ice zone, or open waters south thereof prior to detection at the ship. From our findings we conclude that long-range transport of particles is one source of aerosols in the High Arctic. To assess the importance of long-range particle sources for aerosol-cloud interactions over the inner Arctic in comparison to local and regional biogenic primary aerosol sources, the chemical composition of the detected particles was analyzed for indicators of marine biological origin. Only a~minor fraction showed chemical signatures of potentially ocean-derived primary particles of that kind. However, a chemical bias in the ATOFMS's detection capabilities observed during ASCOS might suggest a presence of a particle type of unknown composition

  19. High brightness electron accelerator

    International Nuclear Information System (INIS)

    Sheffield, R.L.; Carlsten, B.E.; Young, L.M.

    1994-01-01

    A compact high brightness linear accelerator is provided for use, e.g., in a free electron laser. The accelerator has a first plurality of accelerating cavities having end walls with four coupling slots for accelerating electrons to high velocities in the absence of quadrupole fields. A second plurality of cavities receives the high velocity electrons for further acceleration, where each of the second cavities has end walls with two coupling slots for acceleration in the absence of dipole fields. The accelerator also includes a first cavity with an extended length to provide for phase matching the electron beam along the accelerating cavities. A solenoid is provided about the photocathode that emits the electrons, where the solenoid is configured to provide a substantially uniform magnetic field over the photocathode surface to minimize emittance of the electrons as the electrons enter the first cavity. 5 figs

  20. Paleoclimate records at high latitude in Arctic during the Paleogene

    Science.gov (United States)

    Salpin, Marie; Schnyder, Johann; Baudin, François; Suan, Guillaume; Labrousse, Loïc; Popescu, Speranta; Suc, Jean-Pierre

    2015-04-01

    Paleoclimate records at high latitude in Arctic during the Paleogene SALPIN Marie1,2, SCHNYDER Johann1,2, BAUDIN François1,2, SUAN Guillaume3, LABROUSSE Loïc1,2, POPESCU Speranta4, SUC Jean-Pierre1,4 1: Sorbonne Universités, UPMC Univ Paris 06, UMR 7193, Institut des Sciences de la Terre Paris (iSTeP), F 75005, Paris, France 2: CNRS, UMR 7193, Institut des Sciences de la Terre Paris (iSTeP), F 75005 Paris, France 3: UCB Lyon 1, UMR 5276, LGLTPE, 69622 Villeurbanne Cedex, France 4: GEOBIOSTRATDATA.CONSULTING, 385 Route du Mas Rillier 69140 Rillieux la Pape, France The Paleogene is a period of important variations of the Earth climate system either in warming or cooling. The climatic optima of the Paleogene have been recognized both in continental and marine environment. This study focus on high latitudes of the northern hemisphere, in the Arctic Basin. The basin has had an influence on the Cenozoic global climate change according to its polar position. Is there a specific behaviour of the Arctic Basin with respect to global climatic stimuli? Are there possible mechanisms of coupling/decoupling of its dynamics with respect to the global ocean? To answer these questions a unique collection of sedimentary series of Paleogene age interval has been assembled from the Laurentian margin in Northern Yukon (Canada) and from the Siberian margin (New Siberian Islands). Selected continental successions of Paleocene-Eocene age were used to study the response of the Arctic system to known global events, e.g. the climatic optima of the Paleogene (the so-called PETM, ETM2 or the Azolla events). Two sections of Paleocene-Eocene age were sampled near the Mackenzie delta, the so-called Coal Mine (CoMi) and Caribou Hills (CaH) sections. The aim of the study is to precise the climatic fluctuations and to characterise the source rock potential of the basin, eventually linked to the warming events. This study is based on data of multi-proxy analyses: mineralogy on bulk and clay

  1. High bicarbonate assimilation in the dark by Arctic bacteria.

    Science.gov (United States)

    Alonso-Sáez, Laura; Galand, Pierre E; Casamayor, Emilio O; Pedrós-Alió, Carlos; Bertilsson, Stefan

    2010-12-01

    Although both autotrophic and heterotrophic microorganisms incorporate CO₂ in the dark through different metabolic pathways, this process has usually been disregarded in oxic marine environments. We studied the significance and mediators of dark bicarbonate assimilation in dilution cultures inoculated with winter Arctic seawater. At stationary phase, bicarbonate incorporation rates were high (0.5-2.5 μg C L⁻¹ d⁻¹) and correlated with rates of bacterial heterotrophic production, suggesting that most of the incorporation was due to heterotrophs. Accordingly, very few typically chemoautotrophic bacteria were detected by 16S rRNA gene cloning. The genetic analysis of the biotin carboxylase gene accC putatively involved in archaeal CO₂ fixation did not yield any archaeal sequence, but amplified a variety of bacterial carboxylases involved in fatty acids biosynthesis, anaplerotic pathways and leucine catabolism. Gammaproteobacteria dominated the seawater cultures (40-70% of cell counts), followed by Betaproteobacteria and Flavobacteria as shown by catalyzed reporter deposition fluorescence in situ hybridization (CARDFISH). Both Beta- and Gammaproteobacteria were active in leucine and bicarbonate uptake, while Flavobacteria did not take up bicarbonate, as measured by microautoradiography combined with CARDFISH. Within Gammaproteobacteria, Pseudoalteromonas-Colwellia and Oleispira were very active in bicarbonate uptake (ca. 30 and 70% of active cells, respectively), while the group Arctic96B-16 did not take up bicarbonate. Our results suggest that, potentially, the incorporation of CO₂ can be relevant for the metabolism of specific Arctic heterotrophic phylotypes, promoting the maintenance of their cell activity and/or longer survival under resource depleted conditions.

  2. Microbial communities in a High Arctic polar desert landscape

    Directory of Open Access Journals (Sweden)

    Clare M McCann

    2016-03-01

    Full Text Available The High Arctic is dominated by polar desert habitats whose microbial communities are poorly understood. In this study, we used next generation sequencing to describe the α- and β-diversity of polar desert soils from the Kongsfjorden region of Svalbard. Ten phyla consistently dominated the soils and accounted for 95 % of all sequences, with Proteobacteria, Actinobacteria and Chloroflexi being the dominant lineages. In contrast to previous investigations of Arctic soils, Acidobacterial relative abundances were low as were the Archaea throughout the Kongsfjorden polar desert landscape. Lower Acidobacterial abundances were attributed to the circumneutral soil pH in this region which has resulted from the weathering of the underlying carbonate geology. In addition, we correlated previously measured geochemical variables to determine potential controls on the communities. Soil phosphorus, pH, nitrogen and calcium significantly correlated with β-diversity indicating a landscape scale lithological control of soil nutrients which in turn influenced community composition. In addition, soil phosphorus and pH significantly correlated with α- diversity, specifically the Shannon diversity and Chao 1 richness indices.

  3. Evolution of high-Arctic glacial landforms during deglaciation

    Science.gov (United States)

    Midgley, N. G.; Tonkin, T. N.; Graham, D. J.; Cook, S. J.

    2018-06-01

    Glacial landsystems in the high-Arctic have been reported to undergo geomorphological transformation during deglaciation. This research evaluates moraine evolution over a decadal timescale at Midtre Lovénbreen, Svalbard. This work is of interest because glacial landforms developed in Svalbard have been used as an analogue for landforms developed during Pleistocene mid-latitude glaciation. Ground penetrating radar was used to investigate the subsurface characteristics of moraines. To determine surface change, a LiDAR topographic data set (obtained 2003) and a UAV-derived (obtained 2014) digital surface model processed using structure-from-motion (SfM) are also compared. Evaluation of these data sets together enables subsurface character and landform response to climatic amelioration to be linked. Ground penetrating radar evidence shows that the moraine substrate at Midtre Lovénbreen includes ice-rich (radar velocities of 0.17 m ns-1) and debris-rich (radar velocities of 0.1-0.13 m ns-1) zones. The ice-rich zones are demonstrated to exhibit relatively high rates of surface change (mean thresholded rate of -4.39 m over the 11-year observation period). However, the debris-rich zones show a relatively low rate of surface change (mean thresholded rate of -0.98 m over the 11-year observation period), and the morphology of the debris-rich landforms appear stable over the observation period. A complex response of proglacial landforms to climatic warming is shown to occur within and between glacier forelands as indicated by spatially variable surface lowering rates. Landform response is controlled by the ice-debris balance of the moraine substrate, along with the topographic context (such as the influence of meltwater). Site-specific characteristics such as surface debris thickness and glaciofluvial drainage are, therefore, argued to be a highly important control on surface evolution in ice-cored terrain, resulting in a diverse response of high-Arctic glacial landsystems

  4. High-power electronics

    CERN Document Server

    Kapitsa, Petr Leonidovich

    1966-01-01

    High-Power Electronics, Volume 2 presents the electronic processes in devices of the magnetron type and electromagnetic oscillations in different systems. This book explores the problems of electronic energetics.Organized into 11 chapters, this volume begins with an overview of the motion of electrons in a flat model of the magnetron, taking into account the in-phase wave and the reverse wave. This text then examines the processes of transmission of electromagnetic waves of various polarization and the wave reflection from grids made of periodically distributed infinite metal conductors. Other

  5. Metabolic rate and thermal conductance of lemmings from high-arctic Canada and Siberia

    NARCIS (Netherlands)

    Klaassen, M.R.J.; Agrell, J.; Lindström, A.

    2002-01-01

    The arctic climate places high demands on the energy metabolism of its inhabitants. We measured resting (RMR) and basal metabolic rates (BMR), body temperatures, and dry and wet thermal conductances in summer morphs of the lemmings Dicrostonyx groenlandicus and Lemmus trimucronatus in arctic Canada,

  6. Seasonal narwhal habitat associations in the high Arctic

    DEFF Research Database (Denmark)

    Laidre, K.L.; Heide-Jørgensen, M.P.; Logdson, M.L.

    2004-01-01

    Movements and behavior of top marine predators are often closely linked with productive oceanic fronts or regional prey aggregations. Consequently, it is of interest to quantify habitat needs and preferences, which can facilitate predictions of conditions favoring persistence and success....... Multivariate habitat models of movements and dive behavior of narwhals (Monodon monoceros, Linnaeus) in the eastern Canadian high Arctic and West Greenland were developed using data collected from satellite telemetry studies on three separate sub-populations. Twenty-six narwhals were captured between 1993...... and 2000 and fitted with satellite-linked time-depth recorders. Geographic positions of whales at 24-h time steps were linked to dive behavior variables compressed on a daily scale, including numbers of dives to different target depths or durations, time near the surface, daily dive rate, and travel speed...

  7. From the Canadian High Arctic to Mars by Analogue

    Science.gov (United States)

    Soare, R. J.; Pollard, W. H.

    2002-12-01

    Planetary scientists are limited in their understanding of physical bodies in the solar system by the lack of primary data or knowledge. Analogue science is science practised in absentia, precisely in those instances when a non-terrestrial physical environment lies beyond one's direct, empirical grasp. Recognising that some environments on Earth may mirror present or past conditions on Mars, planetary scientists have invoked terrestrial analogues with increasing regularity over the last thirty years as fonts of putative understanding. Notwithstanding its ubiquity in planetary science, analogical reasoning has stood, by and large, unconstrained by rules or guidelines of usage. In order to redress this imbalance we propose to take two steps: 1. introduce primary data on newly discovered pingos at Axel Heiberg Island in the Canadian High Arctic, and 2. coalesce these and related data on Martian glacial, peri-glacial and fluvio-glacial landforms as a model with which to evaluate the meaningfulness of analogical reasoning in planetary science.

  8. Uptake of radionuclides by vegetation at a High Arctic location

    International Nuclear Information System (INIS)

    Dowdall, M.; Gwynn, J.P.; Moran, C.; O'Dea, J.; Davids, C.; Lind, B.

    2005-01-01

    Radionuclide levels in vegetation from a High Arctic location were studied and compared to in situ soil concentrations. Levels of the anthropogenic radionuclide 137 Cs and the natural radionuclides 40 K, 238 U, 226 Ra and 232 Th are discussed and transfer factor (TF) values and aggregated transfer (Tag) values are calculated for vascular plants. Levels of 137 Cs in vegetation generally followed the order mosses > lichen > vascular plants. The uptake of 137 Cs in vascular plants showed an inverse relationship with the uptake of 40 K, with 137 Cs TF and Tag values generally higher than 40 K TF and Tag values. 40 K activity concentrations in all vegetation showed little correlation to associated soil concentrations, while the uptake of 238 U, 226 Ra and 232 Th by vascular and non-vascular plants was generally low. - Uptake of the anthropogenic radionuclide 137 Cs is highest for moss species

  9. Aerosol Size and Chemical Composition in the Canadian High Arctic

    Science.gov (United States)

    Chang, R. Y. W.; Hayes, P. L.; Leaitch, W. R.; Croft, B.; O'Neill, N. T.; Fogal, P.; Drummond, J. R.; Sloan, J. J.

    2015-12-01

    Arctic aerosol have a strong annual cycle, with winter months dominated by long range transport from lower latitudes resulting in high mass loadings. Conversely, local emissions are more prominent in the summer months because of the decreased influence of transported aerosol, allowing us to regularly observe both transported and local aerosol. This study will present observations of aerosol chemical composition and particle number size distribution collected at the Polar Environment Artic Research Laboratory and the Alert Global Atmospheric Watch Observatory at Eureka (80N, 86W) and Alert (82N, 62W), Nunavut, respectively. Summer time observations of the number size distribution reveal a persistent mode of particles centered between 30-50 nm, with occasional bursts of smaller particles. The non-refractory aerosol chemical composition, measured by the Canadian Network for the Detection of Atmospheric Change quadrupole aerosol mass spectrometer, is primarily organic, with contributions from both aged and fresher organic aerosol. Factor analysis will be conducted to better understand these sources. The site at Eureka is more susceptible to long range transport since it is at the top of a mountain ridge (610 m above sea level) and will be compared to the site at Alert on an elevated plain (200 m above sea level). This will allow us to determine the relative contributions from processes and sources at the sites at different elevations. Comparisons with aerosol optical depth and GEOS-Chem model output will also be presented to put these surface measurements into context with the overlying and regional atmosphere. Results from this study contribute to our knowledge of aerosol in the high Arctic.

  10. Impact of future Arctic shipping on high-latitude black carbon deposition (Invited)

    Science.gov (United States)

    Corbett, J. J.; Browse, J.; Carslaw, K. S.; Schmidt, A.

    2013-12-01

    The retreat of Arctic sea-ice has led to renewed calls to exploit Arctic shipping routes. The diversion of ship traffic through the Arctic will shorten shipping routes and possibly reduce global shipping emissions. However, deposition of black carbon (BC) aerosol emitted by additional Arctic ships could cause a reduction in the albedo of snow and ice, accelerating snow-melt and sea-ice loss. We use recently compiled Arctic shipping emission inventories for 2004 and 2050 together with a global aerosol microphysics model GLOMAP coupled to the chemical transport model TOMCAT to quantify the contribution of future Arctic shipping to high-latitude BC deposition. Emission rates of SOx (SO2 and SO4) and particulate matter (PM) were estimated for 2050 under both business-as-usual and high-growth scenarios. BC particles are assumed to be water-insoluble at emission but can become active in cloud drop formation through soluble material accumulation. After BC particles become cloud-active they are more efficiently wet scavenged, which accounts for 80% of modeled BC deposition. Current-day Arctic shipping contributes 0.3% to the BC mass deposited north of 60N (250 Gg). About 50% of modelled BC deposition is on open ocean, suggesting that current Arctic ship traffic may not significantly contribute to BC deposition on central Arctic sea ice. However, 6 - 8% of deposited BC on the west coast of Greenland originates from local ship traffic. Moreover, in-Arctic shipping contributes some 32% to high-latitude ship-sourced deposition despite accounting for less than 1.0% of global shipping emissions. This suggests that control of in-Arctic shipping BC emissions could yield greater decrease in high-latitude BC deposition than a similar control strategy applied only to the extra-Arctic shipping industry. Arctic shipping in 2050 will contribute less than 1% to the total BC deposition north of 60N due to the much greater relative contribution of BC transported from non-shipping sources

  11. High mountain origin, phylogenetics, evolution, and niche conservatism of arctic lineages in the hemiparasitic genus Pedicularis (Orobanchaceae).

    Science.gov (United States)

    Tkach, Natalia; Ree, Richard H; Kuss, Patrick; Röser, Martin; Hoffmann, Matthias H

    2014-07-01

    The origin of the arctic flora covering the northernmost treeless areas is still poorly understood. Arctic plants may have evolved in situ or immigrated from the adjacent ecosystems. Frequently arctic species have disjunctive distributions between the Arctic and high mountain systems of the temperate zone. This pattern may result from long distance dispersal or from glacial plant migrations and extinctions of intermediate populations. The hemiparasitic genus Pedicularis is represented in the Arctic by c. 28 taxa and ranks among the six most species-rich vascular plant genera of this region. In this study, we test the hypothesis that these lineages evolved from predecessors occurring in northern temperate mountain ranges, many of which are current centers of diversity for the genus. We generated a nuclear ribosomal and chloroplast DNA phylogeny including almost all of the arctic taxa and nearly half of the genus as a whole. The arctic taxa of Pedicularis evolved 12-14 times independently and are mostly nested in lineages that otherwise occur in the high mountains of Eurasia and North America. It appears that only three arctic lineages arose from the present-day center of diversity of the genus, in the Hengduan Mountains and Himalayas. Two lineages are probably of lowland origin. Arctic taxa of Pedicularis show considerable niche conservatism with respect to soil moisture and grow predominantly in moist to wet soils. The studied characteristics of ecology, morphology, and chromosome numbers of arctic Pedicularis show a heterogeneous pattern of evolution. The directions of morphological changes among the arctic lineages show opposing trends. Arctic taxa are chiefly diploid, the few tetraploid chromosome numbers of the genus were recorded only for arctic taxa. Five arctic Pedicularis are annuals or biennials, life forms otherwise rare in the Arctic. Other genera of the Orobanchaceae consist also of an elevated number of short-lived species, thus hemiparasitism may

  12. Size resolved airborne particulate polysaccharides in summer high Arctic

    Science.gov (United States)

    Leck, C.; Gao, Q.; Mashayekhy Rad, F.; Nilsson, U.

    2013-04-01

    Size-resolved aerosol samples for subsequent determination of polysaccharides (monosaccharides in combined form) were collected in air over the central Arctic Ocean during the biologically most active period between the late summer melt season and into the transition to autumn freeze-up. The analysis was carried out using liquid chromatography coupled with highly selective and sensitive tandem mass spectrometry. Polysaccharides were detected in all sizes ranging from 0.035 to 10 μm in diameter with distinct features of heteropolysaccharides, enriched in xylose, glucose + mannose as well as a substantial fraction of deoxysugars. Polysaccharides containing deoxysugars showed a bimodal structure with about 60% of their mass found in the Aitken mode over the pack ice area. Pentose (xylose) and hexose (glucose + mannose) showed a weaker bimodal character and were largely found in the coarse mode in addition to a minor fraction apportioned in the sub-micrometer size range. The concentration of total hydrolysable neutral sugars (THNS) in the samples collected varied over 3 orders of magnitude (1 to 692 pmol m-3) in the super-micrometer size fraction and to a lesser extent in sub-micrometer particles (4 to 88 pmol m-3). Lowest THNS concentrations were observed in air masses that had spent more than 5 days over the pack ice. Within the pack ice area, about 53% (by mass) of the total mass of polysaccharides were found in sub-micrometer particles. The relative abundance of sub-micrometer polysaccharides was closely related to the length of time that the air mass spent over pack ice, with highest fraction (> 90%) observed for > 7 days of advection. The ambient aerosol particles collected onboard ship showed similar monosaccharide composition, compared to particles generated experimentally in situ at the open lead site. This supports the existence of a primary source of particulate polysaccharides from open leads by bubble bursting at the air-sea interface. We speculate that

  13. Energy Design Guidelines for High Performance Schools: Arctic and Subarctic Climates

    Energy Technology Data Exchange (ETDEWEB)

    2004-11-01

    The Energy Design Guidelines for High Performance Schools--Arctic and Subarctic Climates provides school boards, administrators, and design staff with guidance to help them make informed decisions about energy and environmental issues important to school systems and communities. These design guidelines outline high performance principles for the new or retrofit design of your K-12 school in arctic and subarctic climates. By incorporating energy improvements into their construction or renovation plans, schools can significantly reduce energy consumption and costs.

  14. High Arctic summer warming tracked by increased Cassiope tetragona growth in the world's northernmost polar desert.

    Science.gov (United States)

    Weijers, Stef; Buchwal, Agata; Blok, Daan; Löffler, Jörg; Elberling, Bo

    2017-11-01

    Rapid climate warming has resulted in shrub expansion, mainly of erect deciduous shrubs in the Low Arctic, but the more extreme, sparsely vegetated, cold and dry High Arctic is generally considered to remain resistant to such shrub expansion in the next decades. Dwarf shrub dendrochronology may reveal climatological causes of past changes in growth, but is hindered at many High Arctic sites by short and fragmented instrumental climate records. Moreover, only few High Arctic shrub chronologies cover the recent decade of substantial warming. This study investigated the climatic causes of growth variability of the evergreen dwarf shrub Cassiope tetragona between 1927 and 2012 in the northernmost polar desert at 83°N in North Greenland. We analysed climate-growth relationships over the period with available instrumental data (1950-2012) between a 102-year-long C. tetragona shoot length chronology and instrumental climate records from the three nearest meteorological stations, gridded climate data, and North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) indices. July extreme maximum temperatures (JulT emx ), as measured at Alert, Canada, June NAO, and previous October AO, together explained 41% of the observed variance in annual C. tetragona growth and likely represent in situ summer temperatures. JulT emx explained 27% and was reconstructed back to 1927. The reconstruction showed relatively high growing season temperatures in the early to mid-twentieth century, as well as warming in recent decades. The rapid growth increase in C. tetragona shrubs in response to recent High Arctic summer warming shows that recent and future warming might promote an expansion of this evergreen dwarf shrub, mainly through densification of existing shrub patches, at High Arctic sites with sufficient winter snow cover and ample water supply during summer from melting snow and ice as well as thawing permafrost, contrasting earlier notions of limited shrub growth sensitivity to

  15. A high arctic experience of uniting research and monitoring

    Science.gov (United States)

    Schmidt, Niels Martin; Christensen, Torben R.; Roslin, Tomas

    2017-07-01

    Monitoring is science keeping our thumb on the pulse of the environment to detect any changes of concern for societies. Basic science is the question-driven search for fundamental processes and mechanisms. Given the firm root of monitoring in human interests and needs, basic sciences have often been regarded as scientifically "purer"—particularly within university-based research communities. We argue that the dichotomy between "research" and "monitoring" is an artificial one, and that this artificial split clouds the definition of scientific goals and leads to suboptimal use of resources. We claim that the synergy between the two scientific approaches is well distilled by science conducted under extreme logistic constraints, when scientists are forced to take full advantage of both the data and the infrastructure available. In evidence of this view, we present our experiences from two decades of uniting research and monitoring at the remote research facility Zackenberg in High Arctic Greenland. For this site, we show how the combination of insights from monitoring with the mechanistic understanding obtained from basic research has yielded the most complete understanding of the system—to the benefit of all, and as an example to follow. We therefore urge scientists from across the continuum from monitoring to research to come together, to disregard old division lines, and to work together to expose a comprehensive picture of ecosystem change and its consequences.

  16. Cytological and ultrastructural preservation in Eocene Metasequoia leaves from the Canadian high Arctic

    Energy Technology Data Exchange (ETDEWEB)

    Schoenhut, K.; Vann, D.R.; LePage, B.A. [University of Pennsylvania, Philadelphia, PA (United States). Dept. of Earth & Environmental Science

    2004-06-01

    The ultrastructural examination by transmission electron microscopy of 45-million-year-old mummified leaves of Metasequoia extracted from the Upper Coal member of the Buchanan Lake Formation in Napartulik on Axel Heiberg Island revealed the preservation of intact chloroplasts and chloroplast components. Abundant tanniferous cell inclusions may indicate that the 3-mo period of constant daylight during the Arctic summer induced high concentrations of tannins in the leaf tissues, which may have arrested microbial degradation of the litter. Quantified differences in the extent of chloroplast preservation through a vertical section of the lignite suggest that short-term shifts in the depositional environment took place, perhaps influencing the exposure of the leaf tissues to conditions that would either promote or inhibit decomposition.

  17. Late winter biogeochemical conditions under sea ice in the Canadian High Arctic

    Directory of Open Access Journals (Sweden)

    Helen S. Findlay

    2015-12-01

    Full Text Available With the Arctic summer sea-ice extent in decline, questions are arising as to how changes in sea-ice dynamics might affect biogeochemical cycling and phenomena such as carbon dioxide (CO2 uptake and ocean acidification. Recent field research in these areas has concentrated on biogeochemical and CO2 measurements during spring, summer or autumn, but there are few data for the winter or winter–spring transition, particularly in the High Arctic. Here, we present carbon and nutrient data within and under sea ice measured during the Catlin Arctic Survey, over 40 days in March and April 2010, off Ellef Ringnes Island (78° 43.11′ N, 104° 47.44′ W in the Canadian High Arctic. Results show relatively low surface water (1–10 m nitrate (<1.3 µM and total inorganic carbon concentrations (mean±SD=2015±5.83 µmol kg−1, total alkalinity (mean±SD=2134±11.09 µmol kg−1 and under-ice pCO2sw (mean±SD=286±17 µatm. These surprisingly low wintertime carbon and nutrient conditions suggest that the outer Canadian Arctic Archipelago region is nitrate-limited on account of sluggish mixing among the multi-year ice regions of the High Arctic, which could temper the potential of widespread under-ice and open-water phytoplankton blooms later in the season.

  18. High resolution modelling of the decreasing Arctic sea ice

    DEFF Research Database (Denmark)

    Madsen, K. S.; Rasmussen, T. A. S.; Blüthgen, Jonas

    2012-01-01

    The Arctic sea ice cover has been rapidly decreasing and thinning over the last decade, with minimum ice extent in 2007 and almost as low extent in 2011. This study investigates two aspects of the decreasing ice cover; first the large scale thinning and changing dynamics of the polar sea ice, and...

  19. High field electron linacs

    International Nuclear Information System (INIS)

    Le Duff, J.

    1985-12-01

    High field electron linacs are considered as potential candidates to provide very high energies beyond LEP. Since almost twenty years not much improvement has been made on linac technologies as they have been mostly kept at low and medium energies to be used as injectors for storage rings. Today, both their efficiency and their performances are being reconsidered, and for instance the pulse compression sheme developed at SLAC and introduced to upgrade the energy of that linac is a first step towards a new generation of linear accelerators. However this is not enough in terms of power consumption and more development is needed to improve both the efficiency of accelerating structures and the performances of RF power sources

  20. The palaeobiology of high latitude birds from the early Eocene greenhouse of Ellesmere Island, Arctic Canada.

    Science.gov (United States)

    Stidham, Thomas A; Eberle, Jaelyn J

    2016-02-12

    Fossils attributable to the extinct waterfowl clade Presbyornithidae and the large flightless Gastornithidae from the early Eocene (~52-53 Ma) of Ellesmere Island, in northernmost Canada are the oldest Cenozoic avian fossils from the Arctic. Except for its slightly larger size, the Arctic presbyornithid humerus is not distinguishable from fossils of Presbyornis pervetus from the western United States, and the Gastornis phalanx is within the known size range of mid-latitude individuals. The occurrence of Presbyornis above the Arctic Circle in the Eocene could be the result of annual migration like that of its living duck and geese relatives, or it may have been a year-round resident similar to some Eocene mammals on Ellesmere and some extant species of sea ducks. Gastornis, along with some of the mammalian and reptilian members of the Eocene Arctic fauna, likely over-wintered in the Arctic. Despite the milder (above freezing) Eocene climate on Ellesmere Island, prolonged periods of darkness occurred during the winter. Presence of these extinct birds at both mid and high latitudes on the northern continents provides evidence that future increases in climatic warming (closer to Eocene levels) could lead to the establishment of new migratory or resident populations within the Arctic Circle.

  1. High-Arctic Plant-Herbivore Interactions under Climate Influence

    DEFF Research Database (Denmark)

    Berg, Thomas B.; Schmidt, Niels M.; Høye, Toke Thomas

    This chapter focuses on a 10-year data series from Zackenberg on the trophic interactions between two characteristic arctic plant species, arctic willow Salix arctica and mountain avens Dryas octopetala, and three herbivore species covering the very scale of size present at Zackenberg, namely......, the moth Sympistis zetterstedtii, the collared lemming Dicrostonyx groenlandicus and the musk ox Ovibos moschatus. Data from Zackenberg show that timing of snowmelt, the length of the growing season and summer temperature are the basic variables that determine the phenology of flowering and primary...... production upon which the herbivores depend, and snow may be the most important climatic factor affecting the different trophic levels and the interactions between them. Hence, the spatio-temporal distribution of snow, as well as thawing events during winter, may have considerable effects on the herbivores...

  2. Revisiting factors controlling methane emissions from high-Arctic tundra

    DEFF Research Database (Denmark)

    Mastepanov, M.; Sigsgaard, C.; Tagesson, T.

    2013-01-01

    controlling methane emission, i.e. temperature and water table position. Late in the growing season CH4 emissions were found to be very similar between the study years (except the extremely dry 2010) despite large differences in climatic factors (temperature and water table). Late-season bursts of CH4...... short-term control factors (temperature and water table). Our findings suggest the importance of multiyear studies with a continued focus on shoulder seasons in Arctic ecosystems....

  3. Three recent ice entrapments of Arctic cetaceans in West Greenland and the eastern Canadian High Arctic

    Directory of Open Access Journals (Sweden)

    MP Heide-Jørgensen

    2002-07-01

    Full Text Available Three ice entrapments of Monodontids have been reported in the western North Atlantic since 1993. Hunters in Disko Bay, West Greenland, discovered one in March 1994 that included about 150 narwhals (Monodon monoceros. The entrapment occurred during a sudden cold period which caused ice to form rapidly. The trapped whales were subject to hunting, but about 50 of the killed whales could not be retrieved in the ice. The whales were trapped in a small opening in the ice and because of that they would probably have succumbed even if not discovered by hunters. Two entrapments involving white whales or belugas (Delphinapterus leucas occurred in the eastern Canadian Arctic in May 1999; one in Lancaster Sound discovered by polar bear (Ursus maritimus researchers and one in Jones Sound discovered by hunters. The first included one bowhead whale (Balaena mysticetus and about 40 belugas that were being preyed upon by polar bears. The second involved at least 170 belugas, of which about 100 were killed by polar bears and 17 were taken by hunters. The entrapments in Disko Bay and Jones Sound both occurred in areas where entrapments have previously been reported, whereas the one in Lancaster Sound was in a new area.

  4. Exploring the mobility of cryoconite on High-Arctic glaciers

    Science.gov (United States)

    Irvine-Fynn, T. D.; Hodson, A. J.; Bridge, J. W.; Langford, H.; Anesio, A.; Ohlanders, N.; Newton, S.

    2010-12-01

    There has been a growing awareness of the significance of biologically active dust (cryoconite) on the energy balance of, and nutrient cycling at glacier surfaces. Moreover, researchers have estimated the mass of biological material released from glacier ice to downstream environments and ecosystems, including the melt-out of cells from emergent ice in the ablation area. However, the processes, rates and mechanisms of cryoconite mobility and transport have not been fully explored. For many smaller valley glaciers in the High-Arctic, the climate dictates only a thin (~ 1m) layer of ice at the glacier surface is at the melting point during the summer months. This surface ice is commonly characterized by an increased porosity in response to incident energy and hydraulic conditions, and has been termed the “weathering crust”. The presence of cryoconite, with its higher radiation absorption, exacerbates the weathering crust development. Thus, crucially, the transport of cryoconite is not confined to simply a ‘smooth’ ice surface, but rather also includes mobility in the near-surface ice matrix. Here, we present initial results from investigations of cryoconite transport at Midtre Lovénbreen and Longyearbreen, two north-facing valley glaciers in Svalbard (Norway). Using time-lapse imagery, we explore the transport rates of cryoconite on a glacier surface and consider the associations between mobility and meteorological conditions. Results suggest some disparity between micro-, local- and plot-scale observations of cryoconite transport: the differences imply controlling influences of cryoconite volume, ice surface topography and ice structure. While to examine the relative volumes of cryoconite exported from the glacier surface by supraglacial streams we employ flow cytometry, using SYBR-Green-II staining to identify the biological component of the suspended load. Preliminary comparisons between shallow (1m) ice cores and in-stream concentrations suggest

  5. Alkenone-based reconstructions reveal four-phase Holocene temperature evolution for High Arctic Svalbard

    Science.gov (United States)

    van der Bilt, Willem G. M.; D'Andrea, William J.; Bakke, Jostein; Balascio, Nicholas L.; Werner, Johannes P.; Gjerde, Marthe; Bradley, Raymond S.

    2018-03-01

    Situated at the crossroads of major oceanic and atmospheric circulation patterns, the Arctic is a key component of Earth's climate system. Compounded by sea-ice feedbacks, even modest shifts in the region's heat budget drive large climate responses. This is highlighted by the observed amplified response of the Arctic to global warming. Assessing the imprint and signature of underlying forcing mechanisms require paleoclimate records, allowing us to expand our knowledge beyond the short instrumental period and contextualize ongoing warming. However, such datasets are scarce and sparse in the Arctic, limiting our ability to address these issues. Here, we present two quantitative Holocene-length paleotemperature records from the High Arctic Svalbard archipelago, situated in the climatically sensitive Arctic North Atlantic. Temperature estimates are based on U37K unsaturation ratios from sediment cores of two lakes. Our data reveal a dynamic Holocene temperature evolution, with reconstructed summer lake water temperatures spanning a range of ∼6-8 °C, and characterized by four phases. The Early Holocene was marked by an early onset (∼10.5 ka cal. BP) of insolation-driven Hypsithermal conditions, likely compounded by strengthening oceanic heat transport. This warm interval was interrupted by cooling between ∼10.5-8.3 ka cal. BP that we attribute to cooling effects from the melting Northern Hemisphere ice sheets. Temperatures declined throughout the Middle Holocene, following a gradual trend that was accentuated by two cooling steps between ∼7.8-7 ka cal. BP and around ∼4.4-4.3 ka cal. BP. These transitions coincide with a strengthening influence of Arctic water and sea-ice in the adjacent Fram Strait. During the Late Holocene (past 4 ka), temperature change decoupled from the still-declining insolation, and fluctuated around comparatively cold mean conditions. By showing that Holocene Svalbard temperatures were governed by an alternation of forcings, this study

  6. Proton-pumping rhodopsins are abundantly expressed by microbial eukaryotes in a high-Arctic fjord.

    Science.gov (United States)

    Vader, Anna; Laughinghouse, Haywood D; Griffiths, Colin; Jakobsen, Kjetill S; Gabrielsen, Tove M

    2018-02-01

    Proton-pumping rhodopsins provide an alternative pathway to photosynthesis by which solar energy can enter the marine food web. Rhodopsin genes are widely found in marine bacteria, also in the Arctic, and were recently reported from several eukaryotic lineages. So far, little is known about rhodopsin expression in Arctic eukaryotes. In this study, we used metatranscriptomics and 18S rDNA tag sequencing to examine the mid-summer function and composition of marine protists (size 0.45-10 µm) in the high-Arctic Billefjorden (Spitsbergen), especially focussing on the expression of microbial proton-pumping rhodopsins. Rhodopsin transcripts were highly abundant, at a level similar to that of genes involved in photosynthesis. Phylogenetic analyses placed the environmental rhodopsins within disparate eukaryotic lineages, including dinoflagellates, stramenopiles, haptophytes and cryptophytes. Sequence comparison indicated the presence of several functional types, including xanthorhodopsins and a eukaryotic clade of proteorhodopsin. Transcripts belonging to the proteorhodopsin clade were also abundant in published metatranscriptomes from other oceanic regions, suggesting a global distribution. The diversity and abundance of rhodopsins show that these light-driven proton pumps play an important role in Arctic microbial eukaryotes. Understanding this role is imperative to predicting the future of the Arctic marine ecosystem faced by a changing light climate due to diminishing sea-ice. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

  7. Molecular analyses reveal high species diversity of trematodes in a sub-Arctic lake

    Science.gov (United States)

    Soldánová, Miroslava; Georgieva, Simona; Roháčováa, Jana; Knudsen, Rune; Kuhn, Jesper A.; Henriksen, Eirik H.; Siwertsson, Anna; Shaw, Jenny C.; Kuris, Armand M.; Amundsen, Per-Arne; Scholz, Tomáš; Lafferty, Kevin D.; Kostadinova, Aneta

    2017-01-01

    To identify trematode diversity and life-cycles in the sub-Arctic Lake Takvatn, Norway, we characterised 120 trematode isolates from mollusc first intermediate hosts, metacercariae from second intermediate host fishes and invertebrates, and adults from fish and invertebrate definitive hosts, using molecular techniques. Phylogenies based on nuclear and/or mtDNA revealed high species richness (24 species or species-level genetic lineages), and uncovered trematode diversity (16 putative new species) from five families typical in lake ecosystems (Allocreadiidae, Diplostomidae, Plagiorchiidae, Schistosomatidae and Strigeidae). Sampling potential invertebrate hosts allowed matching of sequence data for different stages, thus achieving molecular elucidation of trematode life-cycles and exploration of host-parasite interactions. Phylogenetic analyses also helped identify three major mollusc intermediate hosts (Radix balthica, Pisidium casertanum and Sphaerium sp.) in the lake. Our findings increase the known trematode diversity at the sub-Arctic Lake Takvatn, showing that digenean diversity is high in this otherwise depauperate sub-Arctic freshwater ecosystem, and indicating that sub-Arctic and Arctic ecosystems may be characterised by unique trematode assemblages.

  8. Biomarkers of Canadian High Arctic Litoral Sediments for Assessment of Organic Matter Sources and Degradation

    Science.gov (United States)

    Pautler, B. G.; Austin, J.; Otto, A.; Stewart, K.; Lamoureux, S. F.; Simpson, M. J.

    2009-05-01

    Carbon stocks in the High Arctic are particularly sensitive to global climate change, and investigation of variations in organic matter (OM) composition is beneficial for the understanding of the alteration of organic carbon under anticipated future elevated temperatures. Molecular-level characterization of solvent extractable compounds and CuO oxidation products of litoral sedimentary OM at the Cape Bounty Arctic Watershed Observatory in the Canadian Arctic Archipelago was conducted to determine the OM sources and decomposition patterns. The solvent extracts contained a series of aliphatic lipids, steroids and one triterpenoid primarily of higher plant origin and new biomarkers, iso- and anteiso-alkanes originating from cerastium arcticum (Arctic mouse-ear chickweed, a native angiosperm) were discovered. Carbon preference index (CPI) values for the n-alkanes, n-alkanols and n-alkanoic acids suggests that the OM biomarkers result from fresh material input in early stage of degradation. The CuO oxidation products were comprised of benzyls, lignin phenols and short-chain diacids and hydroxyacids. High abundance of terrestrial OM biomarkers observed at sites close to the river inlet suggests fluvial inputs as an important pathway to deliver OM into the lake. The lignin phenol vegetation index (LPVI) also suggests that the OM origin is mostly from non-woody angiosperms. A relatively high degree of lignin alteration in the litoral sediments is evident from the abundant ratio of acids and aldehydes of the vanillyl and syringyl monomers. This suggests that the lignin contents have been diagenetically altered as the result of a long residence time in this ecosystem. The molecular-level characterization of litoral sedimentary OM in Canadian High Arctic region provides insight into current OM composition,potential responses to future disturbances and the biogeochemical cycling of carbon in the Arctic.

  9. High-brightness electron injectors

    International Nuclear Information System (INIS)

    Sheffield, R.L.

    1987-01-01

    Free-electron laser (FEL) oscillators and synchrotron light sources require pulse trains of high peak brightness and, in some applications, high-average power. Recent developments in the technology of photoemissive and thermionic electron sources in rf cavities for electron-linac injector applications offer promising advances over conventional electron injectors. Reduced emittance growth in high peak-current electron injectors may be achieved by using high field strengths and by linearizing the radial component of the cavity electric field at the expense of lower shunt impedance

  10. High interannual variability of sea ice thickness in the Arctic region.

    Science.gov (United States)

    Laxon, Seymour; Peacock, Neil; Smith, Doug

    2003-10-30

    Possible future changes in Arctic sea ice cover and thickness, and consequent changes in the ice-albedo feedback, represent one of the largest uncertainties in the prediction of future temperature rise. Knowledge of the natural variability of sea ice thickness is therefore critical for its representation in global climate models. Numerical simulations suggest that Arctic ice thickness varies primarily on decadal timescales owing to changes in wind and ocean stresses on the ice, but observations have been unable to provide a synoptic view of sea ice thickness, which is required to validate the model results. Here we use an eight-year time-series of Arctic ice thickness, derived from satellite altimeter measurements of ice freeboard, to determine the mean thickness field and its variability from 65 degrees N to 81.5 degrees N. Our data reveal a high-frequency interannual variability in mean Arctic ice thickness that is dominated by changes in the amount of summer melt, rather than by changes in circulation. Our results suggest that a continued increase in melt season length would lead to further thinning of Arctic sea ice.

  11. A Possible Link Between Winter Arctic Sea Ice Decline and a Collapse of the Beaufort High?

    Science.gov (United States)

    Petty, Alek A.

    2018-03-01

    A new study by Moore et al. (2018, https://doi.org/10.1002/2017GL076446) highlights a collapse of the anticyclonic "Beaufort High" atmospheric circulation over the western Arctic Ocean in the winter of 2017 and an associated reversal of the sea ice drift through the southern Beaufort Sea (eastward instead of the predominantly westward circulation). The authors linked this to the loss of sea ice in the Barents Sea, anomalous warming over the region, and the intrusion of low-pressure cyclones along the eastern Arctic. In this commentary we discuss the significance of this observation, the challenges associated with understanding these possible linkages, and some of the alternative hypotheses surrounding the impacts of winter Arctic sea ice loss.

  12. Arctide2017, a high-resolution regional tidal model in the Arctic Ocean

    DEFF Research Database (Denmark)

    Cancet, M.; Andersen, O. B.; Lyard, F.

    2018-01-01

    The Arctic Ocean is a challenging region for tidal modelling. The accuracy of the global tidal models decreases by several centimeters in the Polar Regions, which has a large impact on the quality of the satellite altimeter sea surface heights and the altimetry-derived products. NOVELTIS, DTU Space...... and LEGOS have developed Arctide2017, a regional, high-resolution tidal atlas in the Arctic Ocean, in the framework of an extension of the CryoSat Plus for Ocean (CP4O) ESA STSE (Support to Science Element) project. In particular, this atlas benefits from the assimilation of the most complete satellite...... assimilation and validation. This paper presents the implementation methodology and the performance of this new regional tidal model in the Arctic Ocean, compared to the existing global and regional tidal models....

  13. Diving behavior of the Atlantic walrus in high Arctic Greenland and Canada

    DEFF Research Database (Denmark)

    Garde, Eva; Jung-Madsen, Signe; Ditlevsen, Susanne

    2018-01-01

    Investigations of diving behavior of the Atlantic walrus (Odobenus rosmarus rosmarus) in the high Arctic Greenland and Canada are important for understanding behavioral adaptations and area utilization of this Arctic benthic feeder. Furthermore, such information along with estimations of annual......% CI: 1.0–2.6). Based on dive rates, time at depth, haul-out and percentage of feeding dives Alexandra Fjord and Princess Mary Bay in NE Canada and Carey Island in NW Greenland were identified as the most important areas for walrus feeding during summer. Walrus predation on the standing bivalve biomass...

  14. Characterizing Arctic Sea Ice Topography Using High-Resolution IceBridge Data

    Science.gov (United States)

    Petty, Alek; Tsamados, Michel; Kurtz, Nathan; Farrell, Sinead; Newman, Thomas; Harbeck, Jeremy; Feltham, Daniel; Richter-Menge, Jackie

    2016-01-01

    We present an analysis of Arctic sea ice topography using high resolution, three-dimensional, surface elevation data from the Airborne Topographic Mapper, flown as part of NASA's Operation IceBridge mission. Surface features in the sea ice cover are detected using a newly developed surface feature picking algorithm. We derive information regarding the height, volume and geometry of surface features from 2009-2014 within the Beaufort/Chukchi and Central Arctic regions. The results are delineated by ice type to estimate the topographic variability across first-year and multi-year ice regimes.

  15. The Empirical Canadian High Arctic Ionospheric Model (E-CHAIM): Bottomside Parameterization

    Science.gov (United States)

    Themens, D. R.; Jayachandran, P. T.

    2017-12-01

    It is well known that the International Reference Ionosphere (IRI) suffers reduced accuracy in its representation of monthly median ionospheric electron density at high latitudes. These inaccuracies are believed to stem, at least in part, from a historical lack of data from these regions. Now, roughly thirty and forty years after the development of the original URSI and CCIR foF2 maps, respectively, there exists a much larger dataset of high latitude observations of ionospheric electron density. These new measurements come in the form of new ionosonde deployments, such as those of the Canadian High Arctic Ionospheric Network, the CHAMP, GRACE, and COSMIC radio occultation missions, and the construction of the Poker Flat, Resolute, and EISCAT Incoherent Scatter Radar systems. These new datasets afford an opportunity to revise the IRI's representation of the high latitude ionosphere. Using a spherical cap harmonic expansion to represent horizontal and diurnal variability and a Fourier expansion in day of year to represent seasonal variations, we have developed a new model of the bottomside ionosphere's electron density for the high latitude ionosphere, above 50N geomagnetic latitude. For the peak heights of the E and F1 layers (hmE and hmF1, respectively), current standards use a constant value for hmE and either use a single-parameter model for hmF1 (IRI) or scale hmF1 with the F peak (NeQuick). For E-CHAIM, we have diverged from this convention to account for the greater variability seen in these characteristics at high latitudes, opting to use a full spherical harmonic model description for each of these characteristics. For the description of the bottomside vertical electron density profile, we present a single-layer model with altitude-varying scale height. The scale height function is taken as the sum three scale height layer functions anchored to the F2 peak, hmF1, and hmE. This parameterization successfully reproduces the structure of the various bottomside

  16. Soil microbial biomass, activity and community composition along altitudinal gradients in the High Arctic (Billefjorden, Svalbard)

    Czech Academy of Sciences Publication Activity Database

    Kotas, P.; Šantrůčková, H.; Elster, Josef; Kaštovská, E.

    2018-01-01

    Roč. 15, č. 6 (2018), s. 1879-1894 ISSN 1726-4170 R&D Projects: GA MŠk(CZ) LM2015075 Grant - others:GA MŠk LM2010009 Institutional support: RVO:67985939 Keywords : ecosystem * High Arctic * soil microbial biomass Subject RIV: EH - Ecology, Behaviour OBOR OECD: Ecology Impact factor: 3.851, year: 2016

  17. Does warming affect growth rate and biomass production of shrubs in the High Arctic?

    DEFF Research Database (Denmark)

    Campioli, Matteo; Schmidt, Niels Martin; Albert, Kristian Rost

    2013-01-01

    Few studies have assessed directly the impact of warming on plant growth and biomass production in the High Arctic. Here, we aimed to investigate the impact of 7 years of warming (open greenhouses) on the aboveground relative growth rate (RGR) of Cassiope tetragona and Salix arctica in North-East...

  18. High Arctic plant phenology is determined by snowmelt patterns but duration of phenological periods is fixed

    DEFF Research Database (Denmark)

    Semenchuk, Philipp R.; Gillespie, Mark A K; Rumpf, Sabine B.

    2016-01-01

    The duration of specific periods within a plant's life cycle are critical for plant growth and performance. In the High Arctic, the start of many of these phenological periods is determined by snowmelt date, which may change in a changing climate. It has been suggested that the end of these periods...

  19. Controls on microalgal community structures in cryoconite holes upon high-Arctic glaciers, Svalbard

    Czech Academy of Sciences Publication Activity Database

    Vonnahme, T.R.; Devetter, Miloslav; Žárský, J.D.; Šabacká, M.; Elster, Josef

    2016-01-01

    Roč. 13, č. 3 (2016), s. 659-674 ISSN 1726-4170 Institutional support: RVO:60077344 ; RVO:67985939 Keywords : microalgal communities * cryoconite holes * high-Arctic glaciers * Svalbard Subject RIV: EH - Ecology, Behaviour Impact factor: 3.851, year: 2016

  20. The reliance on distant resources for egg formation in high Arctic breeding barnacle geese Branta leucopsis

    NARCIS (Netherlands)

    Hahn, S.M.; Loonen, M.J.J.E.; Klaassen, M.R.J.

    2011-01-01

    Breeding in the high Arctic is time constrained and animals should therefore start with their annual reproduction as early as possible. To allow for such early reproduction in migratory birds, females arrive at the breeding grounds either with body stores or they try to rapidly develop their eggs

  1. The reliance on distant resources for egg formation in high Arctic breeding barnacle geese Branta leucopsis

    NARCIS (Netherlands)

    Hahn, Steffen; Loonen, Maarten J. J. E.; Klaassen, Marcel

    Breeding in the high Arctic is time constrained and animals should therefore start with their annual reproduction as early as possible. To allow for such early reproduction in migratory birds, females arrive at the breeding grounds either with body stores or they try to rapidly develop their eggs

  2. Petroleum contamination movement into permafrost in the high Arctic

    International Nuclear Information System (INIS)

    Biggar, K.W.

    1997-01-01

    The extent of petroleum hydrocarbon contamination that has penetrated the active layer into the permafrost at sites where spills have occurred in Canada's Arctic was discussed. There was evidence to suggest that hydrocarbon contamination may enter the permafrost layer through gravity drainage and cap suction through fissures in the frozen soil, and perhaps by diffusion through the unfrozen water of fine-grained soils. Core samples were taken in frozen silty clay to be sectioned and analyzed for total petroleum hydrocarbons, using ultrasonic solvent extraction and gas chromatography and mass spectrometry analysis. It was concluded that it is possible for petroleum contamination in permafrost to migrate by gravity drainage down soil fissures and then diffuse into surrounding soil. 2 figs

  3. Characteristics of summer-time energy exchange in a high Arctic tundra heath 2000–2010

    Directory of Open Access Journals (Sweden)

    Magnus Lund

    2014-07-01

    Full Text Available Global warming will bring about changes in surface energy balance of Arctic ecosystems, which will have implications for ecosystem structure and functioning, as well as for climate system feedback mechanisms. In this study, we present a unique, long-term (2000–2010 record of summer-time energy balance components (net radiation, R n; sensible heat flux, H; latent heat flux, LE; and soil heat flux, G from a high Arctic tundra heath in Zackenberg, Northeast Greenland. This area has been subjected to strong summer-time warming with increasing active layer depths (ALD during the last decades. We observe high energy partitioning into H, low partitioning into LE and high Bowen ratio (β=H/LE compared with other Arctic sites, associated with local climatic conditions dominated by onshore winds, slender vegetation with low transpiration activity and relatively dry soils. Surface saturation vapour pressure deficit (D s was found to be an important variable controlling within-year surface energy partitioning. Throughout the study period, we observe increasing H/R n and LE/R n and decreasing G/R n and β, related to increasing ALD and decreasing soil wetness. Thus, changes in summer-time surface energy balance partitioning in Arctic ecosystems may be of importance for the climate system.

  4. Svalbard as a study model of future High Arctic coastal environments in a warming world

    Directory of Open Access Journals (Sweden)

    Jacek Piskozub

    2017-10-01

    Full Text Available Svalbard archipelago, a high latitude area in a region undergoing rapid climate change, is relatively easily accessible for field research. This makes the fjords of Spitsbergen, its largest island, some of the best studied Arctic coastal areas. This paper aims at answering the question of how climatically diverse the fjords are, and how representative they are for the expected future Arctic diminishing range of seasonal sea-ice. This study uses a meteorological reanalysis, sea surface temperature climatology, and the results of a recent one-year meteorological campaign in Spitsbergen to determine the seasonal differences between different Spitsbergen fjords, as well as the sea water temperature and ice ranges around Svalbard in recent years. The results show that Spitsbergen fjords have diverse seasonal patterns of air temperature due to differences in the SST of the adjacent ocean, and different cloudiness. The sea water temperatures and ice concentrations around Svalbard in recent years are similar to what is expected most of the Arctic coastal areas in the second half of this century. This makes Spitsbergen a unique field study model of the conditions expected in future warmer High Arctic.

  5. Ten-year trends of atmospheric mercury in the high Arctic compared to Canadian sub-Arctic and mid-latitude sites

    Directory of Open Access Journals (Sweden)

    A. S. Cole

    2013-02-01

    Full Text Available Global emissions of mercury continue to change at the same time as the Arctic is experiencing ongoing climatic changes. Continuous monitoring of atmospheric mercury provides important information about long-term trends in the balance between transport, chemistry, and deposition of this pollutant in the Arctic atmosphere. Ten-year records of total gaseous mercury (TGM from 2000 to 2009 were analyzed from two high Arctic sites at Alert (Nunavut, Canada and Zeppelin Station (Svalbard, Norway; one sub-Arctic site at Kuujjuarapik (Nunavik, Québec, Canada; and three temperate Canadian sites at St. Anicet (Québec, Kejimkujik (Nova Scotia and Egbert (Ontario. Five of the six sites examined showed a decreasing trend over this time period. Overall trend estimates at high latitude sites were: −0.9% yr−1 (95% confidence limits: −1.4, 0 at Alert and no trend (−0.5, +0.7 at Zeppelin Station. Faster decreases were observed at the remainder of the sites: −2.1% yr−1 (−3.1, −1.1 at Kuujjuarapik, −1.9% yr−1 (−2.1, −1.8 at St. Anicet, −1.6% yr−1 (−2.4, −1.0 at Kejimkujik and −2.2% yr−1 (−2.8, −1.7 at Egbert. Trends at the sub-Arctic and mid-latitude sites agree with reported decreases in background TGM concentration since 1996 at Mace Head, Ireland, and Cape Point, South Africa, but conflict with estimates showing an increase in global anthropogenic emissions over a similar period. Trends in TGM at the two high Arctic sites were not only less negative (or neutral overall but much more variable by season. Possible reasons for differences in seasonal and overall trends at the Arctic sites compared to those at lower latitudes are discussed, as well as implications for the Arctic mercury cycle. The first calculations of multi-year trends in reactive gaseous mercury (RGM and total particulate mercury (TPM at Alert were also performed, indicating increases from 2002 to 2009

  6. Decal electronics for printed high performance cmos electronic systems

    KAUST Repository

    Hussain, Muhammad Mustafa; Sevilla, Galo Torres; Cordero, Marlon Diaz; Kutbee, Arwa T.

    2017-01-01

    High performance complementary metal oxide semiconductor (CMOS) electronics are critical for any full-fledged electronic system. However, state-of-the-art CMOS electronics are rigid and bulky making them unusable for flexible electronic applications

  7. Thermophilic anaerobes in arctic marine sediments induced to mineralize complex organic matter at high temperature

    DEFF Research Database (Denmark)

    Hubert, Casey; Arnosti, Carol; Brüchert, Volker

    2010-01-01

    Marine sediments harbour diverse populations of dormant thermophilic bacterial spores that become active in sediment incubation experiments at much higher than in situ temperature. This response was investigated in the presence of natural complex organic matter in sediments of two Arctic fjords......, as well as with the addition of freeze-dried Spirulina or individual high-molecular-weight polysaccharides. During 50°C incubation experiments, Arctic thermophiles catalysed extensive mineralization of the organic matter via extracellular enzymatic hydrolysis, fermentation and sulfate reduction. This high...... reactivity determined the extent of the thermophilic response. Fjord sediments with higher in situ SRR also supported higher SRR at 50°C. Amendment with Spirulina significantly increased volatile fatty acids production and SRR relative to unamended sediment in 50°C incubations. Spirulina amendment also...

  8. Ambient UV-B radiation reduces PSII performance and net photosynthesis in high Arctic Salix arctica

    DEFF Research Database (Denmark)

    Albert, Kristian Rost; Mikkelsen, Teis Nørgaard; Ro-Poulsen, Helge

    2011-01-01

    Ambient ultraviolet-B (UV-B) radiation potentially impacts the photosynthetic performance of high Arctic plants. We conducted an UV-B exclusion experiment in a dwarf shrub heath in NE Greenland (74°N), with open control, filter control, UV-B filtering and UV-AB filtering, all in combination......, nitrogen and UV-B absorbing compounds. Compared to a 60% reduced UV-B irradiance, the ambient solar UV-B reduced net photosynthesis in Salix arctica leaves fixed in the 45° position which exposed leaves to maximum natural irradiance. Also a reduced Calvin Cycle capacity was found, i.e. the maximum rate...... across position in the vegetation. These findings add to the evidence that the ambient solar UV-B currently is a significant stress factor for plants in high Arctic Greenland....

  9. The effect of misleading surface temperature estimations on the sensible heat fluxes at a high Arctic site – the Arctic Turbulence Experiment 2006 on Svalbard (ARCTEX-2006

    Directory of Open Access Journals (Sweden)

    J. Lüers

    2010-01-01

    Full Text Available The observed rapid climate warming in the Arctic requires improvements in permafrost and carbon cycle monitoring, accomplished by setting up long-term observation sites with high-quality in-situ measurements of turbulent heat, water and carbon fluxes as well as soil physical parameters in Arctic landscapes. But accurate quantification and well adapted parameterizations of turbulent fluxes in polar environments presents fundamental problems in soil-snow-ice-vegetation-atmosphere interaction studies. One of these problems is the accurate estimation of the surface or aerodynamic temperature T(0 required to force most of the bulk aerodynamic formulae currently used. Results from the Arctic-Turbulence-Experiment (ARCTEX-2006 performed on Svalbard during the winter/spring transition 2006 helped to better understand the physical exchange and transport processes of energy. The existence of an atypical temperature profile close to the surface in the Arctic spring at Svalbard could be proven to be one of the major issues hindering estimation of the appropriate surface temperature. Thus, it is essential to adjust the set-up of measurement systems carefully when applying flux-gradient methods that are commonly used to force atmosphere-ocean/land-ice models. The results of a comparison of different sensible heat-flux parameterizations with direct measurements indicate that the use of a hydrodynamic three-layer temperature-profile model achieves the best fit and reproduces the temporal variability of the surface temperature better than other approaches.

  10. Biogenic volatile organic compound emissions along a high arctic soil moisture gradient.

    Science.gov (United States)

    Svendsen, Sarah Hagel; Lindwall, Frida; Michelsen, Anders; Rinnan, Riikka

    2016-12-15

    Emissions of biogenic volatile organic compounds (BVOCs) from terrestrial ecosystems are important for the atmospheric chemistry and the formation of secondary organic aerosols, and may therefore influence the climate. Global warming is predicted to change patterns in precipitation and plant species compositions, especially in arctic regions where the temperature increase will be most pronounced. These changes are potentially highly important for the BVOC emissions but studies investigating the effects are lacking. The aim of this study was to investigate the quality and quantity of BVOC emissions from a high arctic soil moisture gradient extending from dry tundra to a wet fen. Ecosystem BVOC emissions were sampled five times in the July-August period using a push-pull enclosure technique, and BVOCs trapped in absorbent cartridges were analyzed using gas chromatography-mass spectrometry. Plant species compositions were estimated using the point intercept method. In order to take into account important underlying ecosystem processes, gross ecosystem production, ecosystem respiration and net ecosystem production were measured in connection with chamber-based BVOC measurements. Highest emissions of BVOCs were found from vegetation communities dominated by Salix arctica and Cassiope tetragona, which had emission profiles dominated by isoprene and monoterpenes, respectively. These results show that emissions of BVOCs are highly dependent on the plant cover supported by the varying soil moisture, suggesting that high arctic BVOC emissions may affect the climate differently if soil water content and plant cover change. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Ambient UV-B radiation decreases photosynthesis in high arctic Vaccinium uliginosum.

    OpenAIRE

    Albert, Kristian; Ro-Poulsen, Helge; N. Mikkelsen, Teis

    2008-01-01

    UV-B-exclusion experiment was established in high arctic Zackenberg, Northeast Greenland, to investigate the possible effects of ambient UV-B on plant performance. During almost a whole growing season, canopy gas exchange and Chl fluorescence were measured on Vaccinium uliginosum (bog blueberry). Leaf area, biomass, carbon, nitrogen and UV-B-absorbing compounds were determined from a late season harvest. Compared with the reduced UV-B treatment, the plants in ambient UV-B were found to have a...

  12. The Need and Opportunity for an Integrated Research, Development and Testing Center in the Alaskan High Arctic

    Science.gov (United States)

    Hardesty, J. O.; Ivey, M.; Helsel, F.; Dexheimer, D.; Lucero, D. A.; Cahill, C. F.; Roesler, E. L.

    2017-12-01

    This presentation will make the case for development of a permanent integrated High Arctic research and testing center at Oliktok Point, Alaska; taking advantage of existing assets and infrastructure, controlled airspace, an active UAS program and local partnerships. Arctic research stations provide critical monitoring and research on climate change for conditions and trends in the Arctic. The US Chair of the Arctic Council increased awareness of gaps in our understanding of Artic systems, scarce monitoring, lack of infrastructure and readiness for emergency response. Less sea ice brings competition for commercial shipping and resource extraction. Search and rescue, pollution mitigation and safe navigation need real-time, wide-area monitoring to respond to events. Multi-national responses for international traffic will drive a greater security presence to protect citizens and sovereign interests. To address research and technology gaps, there is a national need for a US High Arctic Center (USHARC) with an approach to partner stakeholders from science, safety and security to develop comprehensive solutions. The Station should offer year-round use, logistic support and access to varied ecological settings; phased adaptation to changing needs; and support testing of technologies such as multiple autonomous platforms, renewable energies and microgrids, and sensors in Arctic settings. We propose an Arctic Center at Oliktok Point, Alaska. Combined with the Toolik Field Station and Barrow Environmental Observatory, they form a US network of Arctic Stations. An Oliktok Point Station can provide complementary and unique assets that include: access via land, sea and air; coastal and terrestrial ecologies; controlled airspaces across land and ocean; medical and logistic support; atmospheric observations from an adjacent ARM facility; connections to Barrow and Toolik; fiber-optic communications; University of Alaska Fairbanks UAS Test Facility partnership; and an airstrip and

  13. 50 Myr of pulsed mafic magmatism in the High Arctic Large Igneous Province

    Science.gov (United States)

    Pearson, D. G.; Dockman, D. M.; Heaman, L. M.; Gibson, S. A.; Sarkar, C.

    2017-12-01

    Extensive and voluminous Cretaceous mafic magmatism in the Sverdrup Basin of Arctic Canada forms the circum-Arctic High Arctic Large Igneous Province (HALIP). The small number of published high-precision ages for this LIP indicate its eruption over a considerable timespan raising concerns over whether the HALIP can be strictly defined as a single LIP and questioning the role of a single or multiple plumes in its genesis. Here we present an integrated geochemical and geochronological study to better constrain the timing and cause of mafic magma genesis in the Canadian HALIP. Six new U-Pb and four 40Ar/39Ar ages of mafic lavas and intrusive sheets range from 121 Ma to 78 Ma. The U-Pb ages are the first analyzed from the mafic intrusions of Axel Heiberg and Ellesmere Islands. The new geochronology, combined with other published high-precision ages, reveal a > 50 Myr duration of mafic magmatism in the HALIP defined by three main pulses. Tholeiites dominate the initial 25 Myr of magmatism, transitioning to coeval emplacement of alkali and tholeiitic basalts. Whole-rock Sr-Nd isotope ratios indicate that both magma types are derived from a similar source dominated by convecting mantle. Rare-earth-element inversion models reveal that the alkalic and tholeiitic magmas were generated beneath a bimodal lithospheric `lid' thickness of 65 ± 5 and 45 ± 4 km, respectively. We suggest that the early 128 - 122 Ma tholeiitic event is primarily plume-generated and correlates across the circum-Arctic with the other HALIP tholeiites. Younger HALIP magmatism, with coeval alkalic and tholeiitic magmas erupting over 25 Myr, may be explained by alternating modes of edge-driven mantle convection as the primary control on magma genesis. A distal plume may have intensified magma production by edge-driven convection.

  14. High energy polarized electron beams

    International Nuclear Information System (INIS)

    Rossmanith, R.

    1987-01-01

    In nearly all high energy electron storage rings the effect of beam polarization by synchrotron radiation has been measured. The buildup time for polarization in storage rings is of the order of 10 6 to 10 7 revolutions; the spins must remain aligned over this time in order to avoid depolarization. Even extremely small spin deviations per revolution can add up and cause depolarization. The injection and the acceleration of polarized electrons in linacs is much easier. Although some improvements are still necessary, reliable polarized electron sources with sufficiently high intensity and polarization are available. With the linac-type machines SLC at Stanford and CEBAF in Virginia, experiments with polarized electrons will be possible

  15. Continuous daylight in the high-Arctic summer supports high plankton respiration rates compared to those supported in the dark

    KAUST Repository

    Mesa, Elena

    2017-04-21

    Plankton respiration rate is a major component of global CO2 production and is forecasted to increase rapidly in the Arctic with warming. Yet, existing assessments in the Arctic evaluated plankton respiration in the dark. Evidence that plankton respiration may be stimulated in the light is particularly relevant for the high Arctic where plankton communities experience continuous daylight in spring and summer. Here we demonstrate that plankton community respiration evaluated under the continuous daylight conditions present in situ, tends to be higher than that evaluated in the dark. The ratio between community respiration measured in the light (Rlight) and in the dark (Rdark) increased as the 2/3 power of Rlight so that the Rlight:Rdark ratio increased from an average value of 1.37 at the median Rlight measured here (3.62 µmol O2 L-1 d-1) to an average value of 17.56 at the highest Rlight measured here (15.8 µmol O2 L-1 d-1). The role of respiratory processes as a source of CO2 in the Arctic has, therefore, been underestimated and is far more important than previously believed, particularly in the late spring, with 24 h photoperiods, when community respiration rates are highest.

  16. Low Density of Top Predators (Seabirds and Marine Mammals in the High Arctic Pack Ice

    Directory of Open Access Journals (Sweden)

    Claude R. Joiris

    2016-01-01

    Full Text Available The at-sea distribution of top predators, seabirds and marine mammals, was determined in the high Arctic pack ice on board the icebreaker RV Polarstern in July to September 2014. In total, 1,620 transect counts were realised, lasting 30 min each. The five most numerous seabird species represented 74% of the total of 15,150 individuals registered: kittiwake Rissa tridactyla, fulmar Fulmarus glacialis, puffin Fratercula arctica, Ross’s gull Rhodostethia rosea, and little auk Alle alle. Eight cetacean species were tallied for a total of 330 individuals, mainly white-beaked dolphin Lagenorhynchus albirostris and fin whale Balaenoptera physalus. Five pinniped species were represented by a total of 55 individuals and the polar bear Ursus maritimus was represented by 12 individuals. Four main geographical zones were identified: from Tromsø to the outer marginal ice zone (OMIZ, the Arctic pack ice (close pack ice, CPI, the end of Lomonosov Ridge off Siberia, and the route off Siberia and northern Norway. Important differences were detected between zones, both in species composition and in individual abundance. Low numbers of species and high proportion of individuals for some of them can be considered to reflect very low biodiversity. Numbers encountered in zones 2 to 4 were very low in comparison with other European Arctic seas. The observed differences showed strong patterns.

  17. Changes in Arctic vegetation amplify high-latitude warming through the greenhouse effect.

    Science.gov (United States)

    Swann, Abigail L; Fung, Inez Y; Levis, Samuel; Bonan, Gordon B; Doney, Scott C

    2010-01-26

    Arctic climate is projected to change dramatically in the next 100 years and increases in temperature will likely lead to changes in the distribution and makeup of the Arctic biosphere. A largely deciduous ecosystem has been suggested as a possible landscape for future Arctic vegetation and is seen in paleo-records of warm times in the past. Here we use a global climate model with an interactive terrestrial biosphere to investigate the effects of adding deciduous trees on bare ground at high northern latitudes. We find that the top-of-atmosphere radiative imbalance from enhanced transpiration (associated with the expanded forest cover) is up to 1.5 times larger than the forcing due to albedo change from the forest. Furthermore, the greenhouse warming by additional water vapor melts sea-ice and triggers a positive feedback through changes in ocean albedo and evaporation. Land surface albedo change is considered to be the dominant mechanism by which trees directly modify climate at high-latitudes, but our findings suggest an additional mechanism through transpiration of water vapor and feedbacks from the ocean and sea-ice.

  18. On the gate of Arctic footsteps: Doors open to foreign high schools

    Science.gov (United States)

    Manno, C.; Pecchiar, I.

    2012-12-01

    With the increased attention on the changing Arctic Region effective science education, outreach and communication need to be higher priorities within the scientific communities. In order to encourage the dissemination of polar research at educational levels foreign high school students and teachers were visiting Tromso University for a week. The project highlights the role of the universities as link between research and outreach. The first aim of this project was to increase awareness of foreign schools on major topics concerning the Arctic issues (from the economic/social to the environmental/climatic point of view). Forty three Italian high school students were involved in the laboratory activities running at the UiT and participated in seminars. Topics of focus were Ocean Acidification, Global Warming and the combined effects with other anthropogenic stressors. During their stay, students interviewed several scientists in order to allow them to edit a "visiting report" and to elaborate all the material collected. Back in Italy they performed an itinerant exhibition (presentation of a short movie, posters, and pictures) in various Italian schools in order to pass on their Arctic education experience. The project highlights the role of University as communicator of "climate related issues" in the international frame of the "new generation" of students.

  19. Local variability in growth and reproduction of Salix arctica in the High Arctic

    Directory of Open Access Journals (Sweden)

    Noémie Boulanger-Lapointe

    2016-06-01

    Full Text Available Arctic terrestrial ecosystems are heterogeneous because of the strong influences of microtopography, soil moisture and snow accumulation on vegetation distribution. The interaction between local biotic and abiotic factors and global climate patterns will influence species responses to climate change. Salix arctica (Arctic willow is a structuring species, ubiquitous and widespread, and as such is one of the most important shrub species in the High Arctic. In this study, we measured S. arctica reproductive effort, early establishment, survival and growth in the Zackenberg valley, north-east Greenland. We sampled four plant communities that varied with respect to snow conditions, soil moisture, nutrient content and plant composition. We found large variability in reproductive effort and success with total catkin density ranging from 0.6 to 66 catkins/m2 and seedling density from <1 to 101 seedlings/m2. There were also major differences in crown area increment (4–23 cm2/year and stem radial growth (40–74 µm/year. The snowbed community, which experienced a recent reduction in snow cover, supported young populations with high reproductive effort, establishment and growth. Soil nutrient content and herbivore activity apparently did not strongly constrain plant reproduction and growth, but competition by Cassiope tetragona and low soil moisture may inhibit performance. Our results show that local environmental factors, such as snow accumulation, have a significant impact on tundra plant response to climate change and will affect the understanding of regional vegetation response to climate change.

  20. Characterizing aerosol transport into the Canadian High Arctic using aerosol mass spectrometry and Lagrangian modelling

    Science.gov (United States)

    Kuhn, T.; Damoah, R.; Bacak, A.; Sloan, J. J.

    2010-05-01

    We report the analysis of measurements made using an aerosol mass spectrometer (AMS; Aerodyne Research Inc.) that was installed in the Polar Environment Atmospheric Research Laboratory (PEARL) in summer 2006. PEARL is located in the Canadian high Arctic at 610 m above sea level on Ellesmere Island (80° N 86° W). PEARL is unique for its remote location in the Arctic and because most of the time it is situated within the free troposphere. It is therefore well suited as a receptor site to study the long range tropospheric transport of pollutants into the Arctic. Some information about the successful year-round operation of an AMS at a high Arctic site such as PEARL will be reported here, together with design considerations for reliable sampling under harsh low-temperature conditions. Computational fluid dynamics calculations were made to ensure that sample integrity was maintained while sampling air at temperatures that average -40 °C in the winter and can be as low as -55 °C. Selected AMS measurements of aerosol mass concentration, size, and chemical composition recorded during the months of August, September and October 2006 will be reported. During this period, sulfate was at most times the predominant aerosol component with on average 0.115 μg m-3 (detection limit 0.003 μg m-3). The second most abundant component was undifferentiated organic aerosol, with on average 0.11 μg m-3 detection limit (0.04 μg m-3). The nitrate component, which averaged 0.007 μg m-3, was above its detection limit (0.002 μg m-3), whereas the ammonium ion had an apparent average concentration of 0.02 μg m-3, which was approximately equal to its detection limit. A few episodes having increased mass concentrations and lasting from several hours to several days are apparent in the data. These were investigated further using a statistical analysis to determine their common characteristics. High correlations among some of the components arriving during the short term episodes provide

  1. COLLABORATIVE RESEARCH: TOWARDS ADVANCED UNDERSTANDING AND PREDICTIVE CAPABILITY OF CLIMATE CHANGE IN THE ARCTIC USING A HIGH-RESOLUTION REGIONAL ARCTIC CLIMATE SYSTEM MODEL

    Energy Technology Data Exchange (ETDEWEB)

    Gutowski, William J.

    2013-02-07

    The motivation for this project was to advance the science of climate change and prediction in the Arctic region. Its primary goals were to (i) develop a state-of-the-art Regional Arctic Climate system Model (RACM) including high-resolution atmosphere, land, ocean, sea ice and land hydrology components and (ii) to perform extended numerical experiments using high performance computers to minimize uncertainties and fundamentally improve current predictions of climate change in the northern polar regions. These goals were realized first through evaluation studies of climate system components via one-way coupling experiments. Simulations were then used to examine the effects of advancements in climate component systems on their representation of main physics, time-mean fields and to understand variability signals at scales over many years. As such this research directly addressed some of the major science objectives of the BER Climate Change Research Division (CCRD) regarding the advancement of long-term climate prediction.

  2. Diffraction of high energy electrons

    International Nuclear Information System (INIS)

    Bourret, A.

    1981-10-01

    The diffraction of electrons by a crystal is examined to study its structure. As the electron-substance interaction is strong, it must be treated in a dynamic manner. Using the N waves theory and physical optics the base equations giving the wave at the outlet are deduced for a perfect crystal and their equivalence is shown. The more complex case of an imperfect crystal is then envisaged in these two approaches. In both cases, only the diffraction of high energy electrons ( > 50 KeV) are considered since in the diffraction of slow electrons back scattering cannot be ignored. Taking into account an increasingly greater number of beams, through fast calculations computer techniques, enables images to be simulated in very varied conditions. The general use of the Fast Fourier Transform has given a clear cut practical advantage to the multi-layer method [fr

  3. Single-particle characterization of the high-Arctic summertime aerosol

    Directory of Open Access Journals (Sweden)

    B. Sierau

    2014-07-01

    Full Text Available Single-particle mass-spectrometric measurements were carried out in the high Arctic north of 80° during summer 2008. The campaign took place onboard the icebreaker Oden and was part of the Arctic Summer Cloud Ocean Study (ASCOS. The instrument deployed was an aerosol time-of-flight mass spectrometer (ATOFMS that provides information on the chemical composition of individual particles and their mixing state in real time. Aerosols were sampled in the marine boundary layer at stations in the open ocean, in the marginal ice zone, and in the pack ice region. The largest fraction of particles detected for subsequent analysis in the size range of the ATOFMS between approximately 200 and 3000 nm in diameter showed mass-spectrometric patterns, indicating an internal mixing state and a biomass burning and/or biofuel source. The majority of these particles were connected to an air mass layer of elevated particle concentration mixed into the surface mixed layer from the upper part of the marine boundary layer. The second largest fraction was represented by sea salt particles. The chemical analysis of the over-ice sea salt aerosol revealed tracer compounds that reflect chemical aging of the particles during their long-range advection from the marginal ice zone, or open waters south thereof prior to detection at the ship. From our findings we conclude that long-range transport of particles is one source of aerosols in the high Arctic. To assess the importance of long-range particle sources for aerosol–cloud interactions over the inner Arctic in comparison to local and regional biogenic primary aerosol sources, the chemical composition of the detected particles was analyzed for indicators of marine biological origin. Only a minor fraction showed chemical signatures of potentially ocean-derived primary particles of that kind. However, a chemical bias in the ATOFMS's detection capabilities observed during ASCOS might suggest the presence of a particle type of

  4. Single-particle characterization of the high-Arctic summertime aerosol

    Science.gov (United States)

    Sierau, B.; Chang, R. Y.-W.; Leck, C.; Paatero, J.; Lohmann, U.

    2014-07-01

    Single-particle mass-spectrometric measurements were carried out in the high Arctic north of 80° during summer 2008. The campaign took place onboard the icebreaker Oden and was part of the Arctic Summer Cloud Ocean Study (ASCOS). The instrument deployed was an aerosol time-of-flight mass spectrometer (ATOFMS) that provides information on the chemical composition of individual particles and their mixing state in real time. Aerosols were sampled in the marine boundary layer at stations in the open ocean, in the marginal ice zone, and in the pack ice region. The largest fraction of particles detected for subsequent analysis in the size range of the ATOFMS between approximately 200 and 3000 nm in diameter showed mass-spectrometric patterns, indicating an internal mixing state and a biomass burning and/or biofuel source. The majority of these particles were connected to an air mass layer of elevated particle concentration mixed into the surface mixed layer from the upper part of the marine boundary layer. The second largest fraction was represented by sea salt particles. The chemical analysis of the over-ice sea salt aerosol revealed tracer compounds that reflect chemical aging of the particles during their long-range advection from the marginal ice zone, or open waters south thereof prior to detection at the ship. From our findings we conclude that long-range transport of particles is one source of aerosols in the high Arctic. To assess the importance of long-range particle sources for aerosol-cloud interactions over the inner Arctic in comparison to local and regional biogenic primary aerosol sources, the chemical composition of the detected particles was analyzed for indicators of marine biological origin. Only a minor fraction showed chemical signatures of potentially ocean-derived primary particles of that kind. However, a chemical bias in the ATOFMS's detection capabilities observed during ASCOS might suggest the presence of a particle type of unknown composition

  5. Factors affecting biotic mercury concentrations and biomagnification through lake food webs in the Canadian high Arctic

    Energy Technology Data Exchange (ETDEWEB)

    Lescord, Gretchen L., E-mail: glescord@gmail.com [University of New Brunswick/Canadian Rivers Institute, 100 Tucker Park Rd, Saint John, NB E2L 4A6 (Canada); Kidd, Karen A. [University of New Brunswick/Canadian Rivers Institute, 100 Tucker Park Rd, Saint John, NB E2L 4A6 (Canada); Kirk, Jane L. [Environment Canada, Aquatic Contaminants Research Division, 867 Lakeshore Rd, Burlington, ON L7S 1A1 (Canada); O' Driscoll, Nelson J. [Acadia University, 15 University Ave, Wolfville, NS B4P 2R6 (Canada); Wang, Xiaowa; Muir, Derek C.G. [Environment Canada, Aquatic Contaminants Research Division, 867 Lakeshore Rd, Burlington, ON L7S 1A1 (Canada)

    2015-03-15

    In temperate regions of Canada, mercury (Hg) concentrations in biota and the magnitude of Hg biomagnification through food webs vary between neighboring lakes and are related to water chemistry variables and physical lake features. However, few studies have examined factors affecting the variable Hg concentrations in landlocked Arctic char (Salvelinus alpinus) or the biomagnification of Hg through their food webs. We estimated the food web structure of six high Arctic lakes near Resolute Bay, Nunavut, Canada, using stable carbon (δ{sup 13}C) and nitrogen (δ{sup 15}N) isotopes and measured Hg (total Hg (THg) in char, the only fish species, and methylmercury (MeHg) in chironomids and zooplankton) concentrations in biota collected in 2010 and 2011. Across lakes, δ{sup 13}C showed that benthic carbon (chironomids) was the dominant food source for char. Regression models of log Hg versus δ{sup 15}N (of char and benthic invertebrates) showed positive and significant slopes, indicting Hg biomagnification in all lakes, and higher slopes in some lakes than others. However, no principal components (PC) generated using all water chemistry data and physical characteristics of the lakes predicted the different slopes. The PC dominated by aqueous ions was a negative predictor of MeHg concentrations in chironomids, suggesting that water chemistry affects Hg bioavailability and MeHg concentrations in these lower-trophic-level organisms. Furthermore, regression intercepts were predicted by the PCs dominated by catchment area, aqueous ions, and MeHg. Weaker relationships were also found between THg in small char or MeHg in pelagic invertebrates and the PCs dominated by catchment area, and aqueous nitrate and MeHg. Results from these high Arctic lakes suggest that Hg biomagnification differs between systems and that their physical and chemical characteristics affect Hg concentrations in lower-trophic-level biota. - Highlights: • Mercury (Hg) in Arctic char and invertebrates

  6. Carbon dioxide exchange in the High Arctic - examples from terrestrial ecosystems

    DEFF Research Database (Denmark)

    Grøndahl, L.

    of the growing season, which in combination with high temperatures increased uptake rates. The dry heath ecosystem in general gained carbon during the summer season in the order of magnitude -1.4 gCm-2 up to 32 gCm-2. This result is filling out a gap of knowledge on the response of high Arctic ecosystems...... the measurements conducted in the valley to a regional level. Including information on temporal and spatial variability in air temperature and radiation, together with NDVI and a vegetation map a regional estimate of the CO2 exchange during the summer was provided, elaborating the NDVI based estimate on net carbon...

  7. The Need and Opportunity for an Integrated Research, Development and Testing Station in the Alaskan High Arctic

    Science.gov (United States)

    Hardesty, J. O.; Ivey, M.; Helsel, F.; Dexheimer, D.; Cahill, C. F.; Bendure, A.; Lucero, D. A.; Roesler, E. L.

    2016-12-01

    This presentation will make the case for development of a permanent integrated research and testing station at Oliktok Point, Alaska; taking advantage of existing assets and infrastructure, controlled airspace, an active UAS program and local partnerships. Arctic research stations provide critical monitoring and research on climate change for conditions and trends in the Arctic. The US Chair of the Arctic Council has increased awareness of gaps in our understanding of Artic systems, scarce monitoring, lack of infrastructure and readiness for emergency response. Less sea ice brings competition for commercial shipping and resource extraction. Search and rescue, pollution mitigation and safe navigation need real-time, wide-area monitoring to respond to events. Multi-national responses for international traffic will drive a greater security presence to protect citizens and sovereign interests. To address research and technology gaps, there is a national need for a High Arctic Station with an approach that partners stakeholders from science, safety and security to develop comprehensive solutions. The Station should offer year-round use, logistic support and access to varied ecological settings; phased adaptation to changing needs; and support testing of technologies such as multiple autonomous platforms, renewable energies and microgrids, and sensors in Arctic settings. We propose an Arctic Station at Oliktok Point, Alaska. Combined with the Toolik Field Station and Barrow Environmental Observatory, they form a US network of Arctic Stations. An Oliktok Point Station can provide complementary and unique assets that include: ocean access, and coastal and terrestrial systems; road access; controlled airspaces on land and ocean; nearby air facilities, medical and logistic support; atmospheric observations from an adjacent ARM facility; connections to Barrow and Toolik; fiber-optic communications; University of Alaska Fairbanks UAS Test Facility partnership; and an airstrip

  8. Deep-ocean predation by a high Arctic cetacean

    DEFF Research Database (Denmark)

    Laidre, K.L.; Heide-Jørgensen, M.P.; Jørgensen, Ole A

    2004-01-01

    were correlated with predicted whale predation levels based on diving behavior. The difference in Greenland halibut biomass between an area with high predation and a comparable area without whales, approximately 19000 tonnes, corresponded well with the predicted biomass removed by the narwhal sub...

  9. Population dynamics in the high Arctic: Climate variations in time and space

    DEFF Research Database (Denmark)

    Hendrichsen, Ditte Katrine

    Climatic factors profoundly influence the population dynamics, species interactions and demography of Arctic species. Analyses of the spatio-temporal dynamics within and across species are therefore necessary to understand and predict the responses of Arctic ecosystems to climatic variability...

  10. High current plasma electron emitter

    International Nuclear Information System (INIS)

    Fiksel, G.; Almagri, A.F.; Craig, D.

    1995-07-01

    A high current plasma electron emitter based on a miniature plasma source has been developed. The emitting plasma is created by a pulsed high current gas discharge. The electron emission current is 1 kA at 300 V at the pulse duration of 10 ms. The prototype injector described in this paper will be used for a 20 kA electrostatic current injection experiment in the Madison Symmetric Torus (MST) reversed-field pinch. The source will be replicated in order to attain this total current requirement. The source has a simple design and has proven very reliable in operation. A high emission current, small size (3.7 cm in diameter), and low impurity generation make the source suitable for a variety of fusion and technological applications

  11. Arctic Sovereignty Disputes: International Relations Theory in the High North

    Science.gov (United States)

    2011-12-01

    Russians continue to retain their long-range strategic bombing fleets, consisting of the TU-160 Supersonic ( Blackjack ), an all-weather aircraft with...icebreakers, and the only operational heavy icebreaker, it is already beyond service life expectations and recently suffered a major engine failure...DISPUTES: INTERNATIONAL RELATIONS THEORY IN THE HIGH NORTH by Darrin D. Davis December 2011 Thesis Co-Advisors: Anne L. Clunan

  12. Suspended sediment in a high-Arctic river

    DEFF Research Database (Denmark)

    Ladegaard-Pedersen, Pernille; Sigsgaard, Charlotte; Kroon, Aart

    2017-01-01

    -2012) of daily measurements from the high-Artic Zackenberg River in Northeast Greenland to estimate annual suspended sediment fluxes based on four commonly used methods: M1) is the discharge weighted mean and uses direct measurements, while M2-M4) are one uncorrected and two bias corrected rating curves......-1 and 61,000±16,000ty-1. Extreme events with high discharges had a mean duration of 1day. The average suspended sediment flux during extreme events was 17,000±5000ty-1, which constitutes a year-to-year variation of 20-37% of the total annual flux. The most accurate sampling strategy was bi...... extrapolating a continuous concentration trace from measured values. All methods are tested on complete and reduced datasets. The average annual runoff in the period 2005-2012 was 190±25mio·m3 y-1. The different estimation methods gave a range of average annual suspended sediment fluxes between 43,000±10,000ty...

  13. High Power Electron Accelerator Prototype

    CERN Document Server

    Tkachenko, Vadim; Cheskidov, Vladimir; Korobeynikov, G I; Kuznetsov, Gennady I; Lukin, A N; Makarov, Ivan; Ostreiko, Gennady; Panfilov, Alexander; Sidorov, Alexey; Tarnetsky, Vladimir V; Tiunov, Michael A

    2005-01-01

    In recent time the new powerful industrial electron accelerators appear on market. It caused the increased interest to radiation technologies using high energy X-rays due to their high penetration ability. However, because of low efficiency of X-ray conversion for electrons with energy below 5 MeV, the intensity of X-rays required for some industrial applications can be achieved only when the beam power exceeds 300 kW. The report describes a project of industrial electron accelerator ILU-12 for electron energy up to 5 MeV and beam power up to 300 kW specially designed for use in industrial applications. On the first stage of work we plan to use the existing generator designed for ILU-8 accelerator. It is realized on the GI-50A triode and provides the pulse power up to 1.5-2 MW and up to 20-30 kW of average power. In the report the basic concepts and a condition of the project for today are reflected.

  14. Net Ecosystem Exchange of CO2 with Rapidly Changing High Arctic Landscapes

    Science.gov (United States)

    Emmerton, C. A.

    2015-12-01

    High Arctic landscapes are expansive and changing rapidly. However our understanding of their functional responses and potential to mitigate or enhance anthropogenic climate change is limited by few measurements. We collected eddy covariance measurements to quantify the net ecosystem exchange (NEE) of CO2 with polar semidesert and meadow wetland landscapes at the highest-latitude location measured to date (82°N). We coupled these rare data with ground and satellite vegetation production measurements (Normalized Difference Vegetation Index; NDVI) to evaluate the effectiveness of upscaling local to regional NEE. During the growing season, the dry polar semidesert landscape was a near zero sink of atmospheric CO2 (NEE: -0.3±13.5 g C m-2). A nearby meadow wetland accumulated over two magnitudes more carbon (NEE: -79.3±20.0 g C m-2) than the polar semidesert landscape, and was similar to meadow wetland NEE at much more southern latitudes. Polar semidesert NEE was most influenced by moisture, with wetter surface soils resulting in greater soil respiration and CO2 emissions. At the meadow wetland, soil heating enhanced plant growth, which in turn increased CO2 uptake. Our upscaling assessment found that polar semidesert NDVI measured on site was low (mean: 0.120-0.157) and similar to satellite measurements (mean: 0.155-0.163). However, weak plant growth resulted in poor satellite NDVI-NEE relationships and created challenges for remotely-detecting changes in the cycling of carbon on the polar semidesert landscape. The meadow wetland appeared more suitable to assess plant production and NEE via remote-sensing, however high Arctic wetland extent is constrained by topography to small areas that may be difficult to resolve with large satellite pixels. We predict that until summer precipitation and humidity increases substantially, climate-related changes of dry high Arctic landscapes may be restricted by poor soil moisture retention, and therefore have some inertia against

  15. Deeper snow alters soil nutrient availability and leaf nutrient status in high Arctic tundra

    DEFF Research Database (Denmark)

    Semenchuk, Philipp R.; Elberling, Bo; Amtorp, Cecilie

    2015-01-01

    season. Changing nutrient availability may be reflected in plant N and chlorophyll content and lead to increased photosynthetic capacity, plant growth, and ultimately carbon (C) assimilation by plants. In this study, we increased snow depth and thereby cold-season soil temperatures in high Arctic...... Svalbard in two vegetation types spanning three moisture regimes. We measured growing-season availability of ammonium (NH4 (+)), nitrate (NO3 (-)), total dissolved organic carbon (DOC) and nitrogen (TON) in soil; C, N, delta N-15 and chlorophyll content in Salix polaris leaves; and leaf sizes of Salix...

  16. Ambient UV-B radiation reduces PSII performance and net photosynthesis in high Arctic Salix arctica

    DEFF Research Database (Denmark)

    Albert, Kristian Rost; Mikkelsen, Teis Nørgaard; Ro-Poulsen, H.

    2011-01-01

    , nitrogen and UV-B absorbing compounds. Compared to a 60% reduced UV-B irradiance, the ambient solar UV-B reduced net photosynthesis in Salix arctica leaves fixed in the 45° position which exposed leaves to maximum natural irradiance. Also a reduced Calvin Cycle capacity was found, i.e. the maximum rate...... across position in the vegetation. These findings add to the evidence that the ambient solar UV-B currently is a significant stress factor for plants in high Arctic Greenland....

  17. Soil fauna communities and microbial respiration in high Arctic tundra soils at Zackenberg, Northeast Greenland

    DEFF Research Database (Denmark)

    Sørensen, Louise I.; Holmstrup, Martin; Maraldo, Kristine

    2006-01-01

    The soil fauna communities were described for three dominant vegetation types in a high arctic site at Zackenberg, Northeast Greenland. Soil samples were extracted to quantify the densities of mites, collembolans, enchytraeids, diptera larvae, nematodes and protozoa. Rates of microbial respiration...... densities (naked amoeba and heterotrophic flagellates) were equal. Respiration rate of unamended soil was similar in soil from the three plots. However, a higher respiration rate increase in carbon + nutrient amended soil and the higher densities of soil fauna (with the exception of mites and protozoa...

  18. Dependence of Arctic climate on the latitudinal position of stationary waves and to high-latitudes surface warming

    Science.gov (United States)

    Shin, Yechul; Kang, Sarah M.; Watanabe, Masahiro

    2017-12-01

    Previous studies suggest large uncertainties in the stationary wave response under global warming. Here, we investigate how the Arctic climate responds to changes in the latitudinal position of stationary waves, and to high-latitudes surface warming that mimics the effect of Arctic sea ice loss under global warming. To generate stationary waves in an atmospheric model coupled to slab ocean, a series of experiments is performed where the thermal forcing with a zonal wavenumber-2 (with zero zonal-mean) is prescribed at the surface at different latitude bands in the Northern Hemisphere. When the stationary waves are generated in the subtropics, the cooling response dominates over the warming response in the lower troposphere due to cloud radiative effects. Then, the low-level baroclinicity is reduced in the subtropics, which gives rise to a poleward shift of the eddy driven jet, thereby inducing substantial cooling in the northern high latitudes. As the stationary waves are progressively generated at higher latitudes, the zonal-mean climate state gradually becomes more similar to the integration with no stationary waves. These differences in the mean climate affect the Arctic climate response to high-latitudes surface warming. Additional surface heating over the Arctic is imposed to the reference climates in which the stationary waves are located at different latitude bands. When the stationary waves are positioned at lower latitudes, the eddy driven jet is located at higher latitude, closer to the prescribed Arctic heating. As baroclinicity is more effectively perturbed, the jet shifts more equatorward that accompanies a larger reduction in the poleward eddy transport of heat and momentum. A stronger eddy-induced descending motion creates greater warming over the Arctic. Our study calls for a more accurate simulation of the present-day stationary wave pattern to enhance the predictability of the Arctic warming response in a changing climate.

  19. High current polarized electron source

    Science.gov (United States)

    Suleiman, R.; Adderley, P.; Grames, J.; Hansknecht, J.; Poelker, M.; Stutzman, M.

    2018-05-01

    Jefferson Lab operates two DC high voltage GaAs photoguns with compact inverted insulators. One photogun provides the polarized electron beam at the Continuous Electron Beam Accelerator Facility (CEBAF) up to 200 µA. The other gun is used for high average current photocathode lifetime studies at a dedicated test facility up to 4 mA of polarized beam and 10 mA of un-polarized beam. GaAs-based photoguns used at accelerators with extensive user programs must exhibit long photocathode operating lifetime. Achieving this goal represents a significant challenge for proposed facilities that must operate in excess of tens of mA of polarized average current. This contribution describes techniques to maintain good vacuum while delivering high beam currents, and techniques that minimize damage due to ion bombardment, the dominant mechanism that reduces photocathode yield. Advantages of higher DC voltage include reduced space-charge emittance growth and the potential for better photocathode lifetime. Highlights of R&D to improve the performance of polarized electron sources and prolong the lifetime of strained-superlattice GaAs are presented.

  20. Soil microbial biomass, activity and community composition along altitudinal gradients in the High Arctic (Billefjorden, Svalbard

    Directory of Open Access Journals (Sweden)

    P. Kotas

    2018-03-01

    Full Text Available The unique and fragile High Arctic ecosystems are vulnerable to global climate warming. The elucidation of factors driving microbial distribution and activity in arctic soils is essential for a comprehensive understanding of ecosystem functioning and its response to environmental change. The goals of this study were to investigate microbial biomass and activity, microbial community structure (MCS, and their environmental controls in soils along three elevational transects in the coastal mountains of Billefjorden, central Svalbard. Soils from four different altitudes (25, 275, 525 and 765 m above sea level were analyzed for a suite of characteristics including temperature regimes, organic matter content, base cation availability, moisture, pH, potential respiration, and microbial biomass and community structure using phospholipid fatty acids (PLFAs. We observed significant spatial heterogeneity of edaphic properties among transects, resulting in transect-specific effects of altitude on most soil parameters. We did not observe any clear elevation pattern in microbial biomass, and microbial activity revealed contrasting elevational patterns between transects. We found relatively large horizontal variability in MCS (i.e., between sites of corresponding elevation in different transects, mainly due to differences in the composition of bacterial PLFAs, but also a systematic altitudinal shift in MCS related to different habitat preferences of fungi and bacteria, which resulted in high fungi-to-bacteria ratios at the most elevated sites. The biological soil crusts on these most elevated, unvegetated sites can host microbial assemblages of a size and activity comparable to those of the arctic tundra ecosystem. The key environmental factors determining horizontal and vertical changes in soil microbial properties were soil pH, organic carbon content, soil moisture and Mg2+ availability.

  1. Soil microbial biomass, activity and community composition along altitudinal gradients in the High Arctic (Billefjorden, Svalbard)

    Science.gov (United States)

    Kotas, Petr; Šantrůčková, Hana; Elster, Josef; Kaštovská, Eva

    2018-03-01

    The unique and fragile High Arctic ecosystems are vulnerable to global climate warming. The elucidation of factors driving microbial distribution and activity in arctic soils is essential for a comprehensive understanding of ecosystem functioning and its response to environmental change. The goals of this study were to investigate microbial biomass and activity, microbial community structure (MCS), and their environmental controls in soils along three elevational transects in the coastal mountains of Billefjorden, central Svalbard. Soils from four different altitudes (25, 275, 525 and 765 m above sea level) were analyzed for a suite of characteristics including temperature regimes, organic matter content, base cation availability, moisture, pH, potential respiration, and microbial biomass and community structure using phospholipid fatty acids (PLFAs). We observed significant spatial heterogeneity of edaphic properties among transects, resulting in transect-specific effects of altitude on most soil parameters. We did not observe any clear elevation pattern in microbial biomass, and microbial activity revealed contrasting elevational patterns between transects. We found relatively large horizontal variability in MCS (i.e., between sites of corresponding elevation in different transects), mainly due to differences in the composition of bacterial PLFAs, but also a systematic altitudinal shift in MCS related to different habitat preferences of fungi and bacteria, which resulted in high fungi-to-bacteria ratios at the most elevated sites. The biological soil crusts on these most elevated, unvegetated sites can host microbial assemblages of a size and activity comparable to those of the arctic tundra ecosystem. The key environmental factors determining horizontal and vertical changes in soil microbial properties were soil pH, organic carbon content, soil moisture and Mg2+ availability.

  2. Warmer and wetter winters: characteristics and implications of an extreme weather event in the High Arctic

    International Nuclear Information System (INIS)

    Hansen, Brage B; Isaksen, Ketil; Benestad, Rasmus E; Kohler, Jack; Pedersen, Åshild Ø; Loe, Leif E; Coulson, Stephen J; Larsen, Jan Otto; Varpe, Øystein

    2014-01-01

    One predicted consequence of global warming is an increased frequency of extreme weather events, such as heat waves, droughts, or heavy rainfalls. In parts of the Arctic, extreme warm spells and heavy rain-on-snow (ROS) events in winter are already more frequent. How these weather events impact snow-pack and permafrost characteristics is rarely documented empirically, and the implications for wildlife and society are hence far from understood. Here we characterize and document the effects of an extreme warm spell and ROS event that occurred in High Arctic Svalbard in January–February 2012, during the polar night. In this normally cold semi-desert environment, we recorded above-zero temperatures (up to 7 °C) across the entire archipelago and record-breaking precipitation, with up to 98 mm rainfall in one day (return period of >500 years prior to this event) and 272 mm over the two-week long warm spell. These precipitation amounts are equivalent to 25 and 70% respectively of the mean annual total precipitation. The extreme event caused significant increase in permafrost temperatures down to at least 5 m depth, induced slush avalanches with resultant damage to infrastructure, and left a significant ground-ice cover (∼5–20 cm thick basal ice). The ground-ice not only affected inhabitants by closing roads and airports as well as reducing mobility and thereby tourism income, but it also led to high starvation-induced mortality in all monitored populations of the wild reindeer by blocking access to the winter food source. Based on empirical-statistical downscaling of global climate models run under the moderate RCP4.5 emission scenario, we predict strong future warming with average mid-winter temperatures even approaching 0 °C, suggesting increased frequency of ROS. This will have far-reaching implications for Arctic ecosystems and societies through the changes in snow-pack and permafrost properties. (letter)

  3. Warmer and wetter winters: characteristics and implications of an extreme weather event in the High Arctic

    Science.gov (United States)

    Hansen, Brage B.; Isaksen, Ketil; Benestad, Rasmus E.; Kohler, Jack; Pedersen, Åshild Ø.; Loe, Leif E.; Coulson, Stephen J.; Larsen, Jan Otto; Varpe, Øystein

    2014-11-01

    One predicted consequence of global warming is an increased frequency of extreme weather events, such as heat waves, droughts, or heavy rainfalls. In parts of the Arctic, extreme warm spells and heavy rain-on-snow (ROS) events in winter are already more frequent. How these weather events impact snow-pack and permafrost characteristics is rarely documented empirically, and the implications for wildlife and society are hence far from understood. Here we characterize and document the effects of an extreme warm spell and ROS event that occurred in High Arctic Svalbard in January-February 2012, during the polar night. In this normally cold semi-desert environment, we recorded above-zero temperatures (up to 7 °C) across the entire archipelago and record-breaking precipitation, with up to 98 mm rainfall in one day (return period of >500 years prior to this event) and 272 mm over the two-week long warm spell. These precipitation amounts are equivalent to 25 and 70% respectively of the mean annual total precipitation. The extreme event caused significant increase in permafrost temperatures down to at least 5 m depth, induced slush avalanches with resultant damage to infrastructure, and left a significant ground-ice cover (˜5-20 cm thick basal ice). The ground-ice not only affected inhabitants by closing roads and airports as well as reducing mobility and thereby tourism income, but it also led to high starvation-induced mortality in all monitored populations of the wild reindeer by blocking access to the winter food source. Based on empirical-statistical downscaling of global climate models run under the moderate RCP4.5 emission scenario, we predict strong future warming with average mid-winter temperatures even approaching 0 °C, suggesting increased frequency of ROS. This will have far-reaching implications for Arctic ecosystems and societies through the changes in snow-pack and permafrost properties.

  4. Diversification of Nitrogen Sources in Various Tundra Vegetation Types in the High Arctic.

    Directory of Open Access Journals (Sweden)

    Grzegorz Skrzypek

    Full Text Available Low nitrogen availability in the high Arctic represents a major constraint for plant growth, which limits the tundra capacity for carbon retention and determines tundra vegetation types. The limited terrestrial nitrogen (N pool in the tundra is augmented significantly by nesting seabirds, such as the planktivorous Little Auk (Alle alle. Therefore, N delivered by these birds may significantly influence the N cycling in the tundra locally and the carbon budget more globally. Moreover, should these birds experience substantial negative environmental pressure associated with climate change, this will adversely influence the tundra N-budget. Hence, assessment of bird-originated N-input to the tundra is important for understanding biological cycles in polar regions. This study analyzed the stable nitrogen composition of the three main N-sources in the High Arctic and in numerous plants that access different N-pools in ten tundra vegetation types in an experimental catchment in Hornsund (Svalbard. The percentage of the total tundra N-pool provided by birds, ranged from 0-21% in Patterned-ground tundra to 100% in Ornithocoprophilous tundra. The total N-pool utilized by tundra plants in the studied catchment was built in 36% by birds, 38% by atmospheric deposition, and 26% by atmospheric N2-fixation. The stable nitrogen isotope mixing mass balance, in contrast to direct methods that measure actual deposition, indicates the ratio between the actual N-loads acquired by plants from different N-sources. Our results enhance our understanding of the importance of different N-sources in the Arctic tundra and the used methodological approach can be applied elsewhere.

  5. Methanogen community composition and rates of methane consumption in Canadian High Arctic permafrost soils.

    Science.gov (United States)

    Allan, J; Ronholm, J; Mykytczuk, N C S; Greer, C W; Onstott, T C; Whyte, L G

    2014-04-01

    Increasing permafrost thaw, driven by climate change, has the potential to result in organic carbon stores being mineralized into carbon dioxide (CO2) and methane (CH4) through microbial activity. This study examines the effect of increasing temperature on community structure and metabolic activity of methanogens from the Canadian High Arctic, in an attempt to predict how warming will affect microbially controlled CH4 soil flux. In situ CO2 and CH4 flux, measured in 2010 and 2011 from ice-wedge polygons, indicate that these soil formations are a net source of CO2 emissions, but a CH4 sink. Permafrost and active layer soil samples were collected at the same sites and incubated under anaerobic conditions at warmer temperatures, with and without substrate amendment. Gas flux was measured regularly and indicated an increase in CH4 flux after extended incubation. Pyrosequencing was used to examine the effects of an extended thaw cycle on methanogen diversity and the results indicate that in situ methanogen diversity, based on the relative abundance of the 16S ribosomal ribonucleic acid (rRNA) gene associated with known methanogens, is higher in the permafrost than in the active layer. Methanogen diversity was also shown to increase in both the active layer and permafrost soil after an extended thaw. This study provides evidence that although High Arctic ice-wedge polygons are currently a sink for CH4, higher arctic temperatures and anaerobic conditions, a possible result of climate change, could result in this soil becoming a source for CH4 gas flux. © 2013 Society for Applied Microbiology and John Wiley & Sons Ltd.

  6. Summertime observations of elevated levels of ultrafine particles in the high Arctic marine boundary layer

    Science.gov (United States)

    Burkart, Julia; Willis, Megan D.; Bozem, Heiko; Thomas, Jennie L.; Law, Kathy; Hoor, Peter; Aliabadi, Amir A.; Köllner, Franziska; Schneider, Johannes; Herber, Andreas; Abbatt, Jonathan P. D.; Leaitch, W. Richard

    2017-05-01

    Motivated by increasing levels of open ocean in the Arctic summer and the lack of prior altitude-resolved studies, extensive aerosol measurements were made during 11 flights of the NETCARE July 2014 airborne campaign from Resolute Bay, Nunavut. Flights included vertical profiles (60 to 3000 m above ground level) over open ocean, fast ice, and boundary layer clouds and fogs. A general conclusion, from observations of particle numbers between 5 and 20 nm in diameter (N5 - 20), is that ultrafine particle formation occurs readily in the Canadian high Arctic marine boundary layer, especially just above ocean and clouds, reaching values of a few thousand particles cm-3. By contrast, ultrafine particle concentrations are much lower in the free troposphere. Elevated levels of larger particles (for example, from 20 to 40 nm in size, N20 - 40) are sometimes associated with high N5 - 20, especially over low clouds, suggestive of aerosol growth. The number densities of particles greater than 40 nm in diameter (N > 40) are relatively depleted at the lowest altitudes, indicative of depositional processes that will lower the condensation sink and promote new particle formation. The number of cloud condensation nuclei (CCN; measured at 0.6 % supersaturation) are positively correlated with the numbers of small particles (down to roughly 30 nm), indicating that some fraction of these newly formed particles are capable of being involved in cloud activation. Given that the summertime marine Arctic is a biologically active region, it is important to better establish the links between emissions from the ocean and the formation and growth of ultrafine particles within this rapidly changing environment.

  7. Nitrogen accumulation and partitioning in a High Arctic tundra ecosystem from extreme atmospheric N deposition events

    Energy Technology Data Exchange (ETDEWEB)

    Choudhary, Sonal, E-mail: S.Choudhary@sheffield.ac.uk [Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Management School, University of Sheffield, Conduit Road, Sheffield S10 1FL (United Kingdom); Blaud, Aimeric [Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Osborn, A. Mark [Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); School of Applied Sciences, RMIT University, PO Box 71, Bundoora, VIC 3083 (Australia); Press, Malcolm C. [School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Manchester Metropolitan University, Manchester, M15 6BH (United Kingdom); Phoenix, Gareth K. [Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom)

    2016-06-01

    Arctic ecosystems are threatened by pollution from recently detected extreme atmospheric nitrogen (N) deposition events in which up to 90% of the annual N deposition can occur in just a few days. We undertook the first assessment of the fate of N from extreme deposition in High Arctic tundra and are presenting the results from the whole ecosystem {sup 15}N labelling experiment. In 2010, we simulated N depositions at rates of 0, 0.04, 0.4 and 1.2 g N m{sup −2} yr{sup −1}, applied as {sup 15}NH{sub 4}{sup 15}NO{sub 3} in Svalbard (79{sup °}N), during the summer. Separate applications of {sup 15}NO{sub 3}{sup −} and {sup 15}NH{sub 4}{sup +} were also made to determine the importance of N form in their retention. More than 95% of the total {sup 15}N applied was recovered after one growing season (~ 90% after two), demonstrating a considerable capacity of Arctic tundra to retain N from these deposition events. Important sinks for the deposited N, regardless of its application rate or form, were non-vascular plants > vascular plants > organic soil > litter > mineral soil, suggesting that non-vascular plants could be the primary component of this ecosystem to undergo measurable changes due to N enrichment from extreme deposition events. Substantial retention of N by soil microbial biomass (70% and 39% of {sup 15}N in organic and mineral horizon, respectively) during the initial partitioning demonstrated their capacity to act as effective buffers for N leaching. Between the two N forms, vascular plants (Salix polaris) in particular showed difference in their N recovery, incorporating four times greater {sup 15}NO{sub 3}{sup −} than {sup 15}NH{sub 4}{sup +}, suggesting deposition rich in nitrate will impact them more. Overall, these findings show that despite the deposition rates being extreme in statistical terms, biologically they do not exceed the capacity of tundra to sequester pollutant N during the growing season. Therefore, current and future extreme events

  8. Nitrogen accumulation and partitioning in a High Arctic tundra ecosystem from extreme atmospheric N deposition events

    International Nuclear Information System (INIS)

    Choudhary, Sonal; Blaud, Aimeric; Osborn, A. Mark; Press, Malcolm C.; Phoenix, Gareth K.

    2016-01-01

    Arctic ecosystems are threatened by pollution from recently detected extreme atmospheric nitrogen (N) deposition events in which up to 90% of the annual N deposition can occur in just a few days. We undertook the first assessment of the fate of N from extreme deposition in High Arctic tundra and are presenting the results from the whole ecosystem "1"5N labelling experiment. In 2010, we simulated N depositions at rates of 0, 0.04, 0.4 and 1.2 g N m"−"2 yr"−"1, applied as "1"5NH_4"1"5NO_3 in Svalbard (79"°N), during the summer. Separate applications of "1"5NO_3"− and "1"5NH_4"+ were also made to determine the importance of N form in their retention. More than 95% of the total "1"5N applied was recovered after one growing season (~ 90% after two), demonstrating a considerable capacity of Arctic tundra to retain N from these deposition events. Important sinks for the deposited N, regardless of its application rate or form, were non-vascular plants > vascular plants > organic soil > litter > mineral soil, suggesting that non-vascular plants could be the primary component of this ecosystem to undergo measurable changes due to N enrichment from extreme deposition events. Substantial retention of N by soil microbial biomass (70% and 39% of "1"5N in organic and mineral horizon, respectively) during the initial partitioning demonstrated their capacity to act as effective buffers for N leaching. Between the two N forms, vascular plants (Salix polaris) in particular showed difference in their N recovery, incorporating four times greater "1"5NO_3"− than "1"5NH_4"+, suggesting deposition rich in nitrate will impact them more. Overall, these findings show that despite the deposition rates being extreme in statistical terms, biologically they do not exceed the capacity of tundra to sequester pollutant N during the growing season. Therefore, current and future extreme events may represent a major source of eutrophication. - Highlights: • High Arctic tundra demonstrated a

  9. High Intensity Polarized Electron Sources

    International Nuclear Information System (INIS)

    Poelker, Benard; Adderley, Philip; Brittian, Joshua; Clark, J.; Grames, Joseph; Hansknecht, John; McCarter, James; Stutzman, Marcy; Suleiman, Riad; Surles-law, Kenneth

    2008-01-01

    During the 1990s, at numerous facilities world wide, extensive RandD devoted to constructing reliable GaAs photoguns helped ensure successful accelerator-based nuclear and high-energy physics programs using spin polarized electron beams. Today, polarized electron source technology is considered mature, with most GaAs photoguns meeting accelerator and experiment beam specifications in a relatively trouble-free manner. Proposals for new collider facilities however, require electron beams with parameters beyond today's state-of-the-art and serve to renew interest in conducting polarized electron source RandD. And at CEBAF/Jefferson Lab, there is an immediate pressing need to prepare for new experiments that require considerably more beam current than before. One experiment in particular?Q-weak, a parity violation experiment that will look for physics beyond the Standard Model?requires 180 uA average current at polarization >80% for a duration of one year, with run-averaged helicity correlate

  10. The variability and controls of rock strength along rocky coasts of central Spitsbergen, High Arctic

    Science.gov (United States)

    Strzelecki, Mateusz Czesław

    2017-09-01

    This paper presents the results of the Schmidt Hammer Rock Tests (SHRTs) across a range of rocky coastal landforms. Northern Billefjorden (central Spitsbergen), represents typical High Arctic microtidal fjord environment. Sheltered location and prolonged sea-ice conditions limit wave action. Coastal cliffs, shore platforms and skerries are developed in various rock types including limestone, sandstone, anhydrite/gypsum, dolomite and metamorphic outcrops. SHRT demonstrated a broad variety of relationships between rock strength and distance from shoreline, presence of sediment cover, distribution of snow patches and icefoot, and accumulations of seaweed and driftwood. In general, rock cliff surfaces were the most resistant in their lower and middle zones, that are thermally insulated by thick winter snowdrifts. More exposed cliff tops were fractured and weathered. The differences in rock strength observed along the shore platforms were highly dependent on thickness of sediment cover and shoreline configuration promoting stronger rock surfaces in areas exposed to the longest wave fetch and washed from gravel deposits. Rock strength of skerry islands is influenced by tidal action controlling the duration of tide inundation and movement of sea-ice scratching boulder surfaces. The results presented in this paper emphasize the richness of rock coast geomorphology and processes operating in High Arctic settings.

  11. High renesting rates in arctic-breeding Dunlin (Calidris alpina): A clutch-removal experiment

    Science.gov (United States)

    Gates, H. River; Lanctot, Richard B.; Powell, Abby N.

    2013-01-01

    The propensity to replace a clutch is a complex component of avian reproduction and poorly understood. We experimentally removed clutches from an Arctic-breeding shorebird, the Dunlin (Calidris alpina arcticola), during early and late stages of incubation to investigate replacement clutch rates, renesting interval, and mate and site fidelity between nesting attempts. In contrast to other Arctic studies, we documented renesting by radiotracking individuals to find replacement clutches. We also examined clutch size and mean egg volume to document changes in individual females’ investment in initial and replacement clutches. Finally, we examined the influence of adult body mass, clutch volume, dates of clutch initiation and nest loss, and year on the propensity to renest. We found high (82–95%) and moderate (35–50%) rates of renesting for early and late incubation treatments. Renesting intervals averaged 4.7–6.8 days and were not different for clutches removed early or late in incubation. Most pairs remained together for renesting attempts. Larger females were more likely to replace a clutch; female body mass was the most important parameter predicting propensity to renest. Clutches lost later in the season were less likely to be replaced. We present evidence that renesting is more common in Arctic-breeding shorebirds than was previously thought, and suggest that renesting is constrained by energetic and temporal factors as well as mate availability. Obtaining rates of renesting in species breeding at different latitudes will help determine when this behavior is likely to occur; such information is necessary for demographic models that include individual and population-level fecundity estimates.

  12. Ukpik: testbed for a miniaturized robotic astronomical observatory on a high Arctic mountain

    Science.gov (United States)

    Steinbring, Eric; Leckie, Brian; Hardy, Tim; Caputa, Kris; Fletcher, Murray

    2012-09-01

    Mountains along the northwestern coast of Ellesmere Island, Canada, possess the highest peaks nearest the Pole. This geography, combined with an atmospheric thermal inversion restricted to below ~1000 m during much of the long arctic night, provides excellent opportunities for uninterrupted cloud-free astronomy - provided the challenges of these incredibly remote locations can be overcome. We present a miniaturized robotic observatory for deployment on a High Arctic mountaintop. This system tested the operability of precise optical instruments during winter, and the logistics of installation and maintenance during summer. It is called Ukpik after the Inuktitut name for the snowy owl, and was deployed at two sites accessible only by helicopter, each north of 82 degrees latitude; one on rock at 1100 m elevation and another on a glacier at 1600 m. The instrument suite included at first an all-sky-viewing camera, with the later addition of a small telescope to monitor Polaris, both protected by a retractable weather-proof enclosure. Expanding this to include a narrow-field drift-scanning camera for studying extra-solar planet transits was also investigated, but not implemented. An unique restriction was that all had to be run on batteries recharged primarily by a wind turbine. Supplementary power came from a methanol fuel-cell electrical generator. Communications were via the Iridium satellite network. The system design, and lessons learned from three years of operation are discussed, along with prospects for time-domain astronomy from isolated, high-elevation polar mountaintops.

  13. Decal electronics for printed high performance cmos electronic systems

    KAUST Repository

    Hussain, Muhammad Mustafa

    2017-11-23

    High performance complementary metal oxide semiconductor (CMOS) electronics are critical for any full-fledged electronic system. However, state-of-the-art CMOS electronics are rigid and bulky making them unusable for flexible electronic applications. While there exist bulk material reduction methods to flex them, such thinned CMOS electronics are fragile and vulnerable to handling for high throughput manufacturing. Here, we show a fusion of a CMOS technology compatible fabrication process for flexible CMOS electronics, with inkjet and conductive cellulose based interconnects, followed by additive manufacturing (i.e. 3D printing based packaging) and finally roll-to-roll printing of packaged decal electronics (thin film transistors based circuit components and sensors) focusing on printed high performance flexible electronic systems. This work provides the most pragmatic route for packaged flexible electronic systems for wide ranging applications.

  14. Continuous daylight in the high-Arctic summer supports high plankton respiration rates compared to those supported in the dark

    KAUST Repository

    Mesa, Elena; Delgado-Huertas, Antonio; Carrillo-de-Albornoz, Paloma; Garcí a-Corral, Lara S.; Sanz-Martí n, Marina; Wassmann, Paul; Reigstad, Marit; Sejr, Mikael; Dalsgaard, Tage; Duarte, Carlos M.

    2017-01-01

    Plankton respiration rate is a major component of global CO2 production and is forecasted to increase rapidly in the Arctic with warming. Yet, existing assessments in the Arctic evaluated plankton respiration in the dark. Evidence that plankton

  15. Ultrafine particles in inhabited areas in the Arctic - From very low to high concentrations

    DEFF Research Database (Denmark)

    Pétursdóttir, Una; Kirkelund, Gunvor Marie; Press-Kristensen, Kåre

    2017-01-01

    The Arctic is considered a pristine environment, where pollution mainly originates from global sources. The present study examines particle number concentrations (PNCs) and the main sources of airborne ultrafine particles (UFPs, d < 100 nm) in the town Sisimiut and two nearby settlements, Sarfann......The Arctic is considered a pristine environment, where pollution mainly originates from global sources. The present study examines particle number concentrations (PNCs) and the main sources of airborne ultrafine particles (UFPs, d ..., Sarfannguit and Itilleq, in West Greenland. Measurements were carried out during three weeks in April and May 2016. Air temperatures during the measurements ranged from −4.4 to +8.7 °C. A portable condensation particle counter (P-Trak) was used for the measurements. Results showed that the lowest...... in Sisimiut, while subsequent measurements at the same location showed much lower PNCs. The presence of heavy machinery elevated PNCs highly during two measurement events, giving PNCs up to 270,993 cm−3 but dropping to 1180 cm−3 10 min later, after the vehicle had passed by. A measurement event in Sisimiut...

  16. Temporally delineated sources of major chemical species in high Arctic snow

    Directory of Open Access Journals (Sweden)

    K. M. Macdonald

    2018-03-01

    Full Text Available Long-range transport of aerosol from lower latitudes to the high Arctic may be a significant contributor to climate forcing in the Arctic. To identify the sources of key contaminants entering the Canadian High Arctic an intensive campaign of snow sampling was completed at Alert, Nunavut, from September 2014 to June 2015. Fresh snow samples collected every few days were analyzed for black carbon, major ions, and metals, and this rich data set provided an opportunity for a temporally refined source apportionment of snow composition via positive matrix factorization (PMF in conjunction with FLEXPART (FLEXible PARTicle dispersion model potential emission sensitivity analysis. Seven source factors were identified: sea salt, crustal metals, black carbon, carboxylic acids, nitrate, non-crustal metals, and sulfate. The sea salt and crustal factors showed good agreement with expected composition and primarily northern sources. High loadings of V and Se onto Factor 2, crustal metals, was consistent with expected elemental ratios, implying these metals were not primarily anthropogenic in origin. Factor 3, black carbon, was an acidic factor dominated by black carbon but with some sulfate contribution over the winter-haze season. The lack of K+ associated with this factor, a Eurasian source, and limited known forest fire events coincident with this factor's peak suggested a predominantly anthropogenic combustion source. Factor 4, carboxylic acids, was dominated by formate and acetate with a moderate correlation to available sunlight and an oceanic and North American source. A robust identification of this factor was not possible; however, atmospheric photochemical reactions, ocean microlayer reaction, and biomass burning were explored as potential contributors. Factor 5, nitrate, was an acidic factor dominated by NO3−, with a likely Eurasian source and mid-winter peak. The isolation of NO3− on a separate factor may reflect its complex atmospheric

  17. Elevation-based upscaling of organic carbon stocks in High-Arctic permafrost terrain

    DEFF Research Database (Denmark)

    Weiss, Niels; Faucherre, Samuel; Lampiris, Nikos

    2017-01-01

    Accurate quantity and distribution estimates of permafrost soil organic carbon (SOC) stocks are needed to project potential feedbacks to climate, following warming. Still, upscaling from local field observations to regional estimates to circumarctic assessments remains a challenge. Here we explore...... elevation-based upscaling techniques for High-Arctic permafrost SOC stocks. We combine two detailed, high-resolution SOC inventories on Spitsbergen (Svalbard) with regional validation data. We find a clear relationship between elevation and SOC content, and use this observed exponential correlation, as well...... as discrete elevation classes, as upscaling models for Spitsbergen. We estimate the total amount of permafrost SOC currently present in soils on Spitsbergen to be 105.36 Tg (0.11 Pg), with a mean SOC content of 2.84 ± 0.74 kg C m−2 (mean ± 95% confidence interval). Excluding glaciers and permanent snowfields...

  18. Soil fauna communities and microbial respiration in high Arctic tundra soils at Zackenberg, Northeast Greenland

    DEFF Research Database (Denmark)

    Sørensen, Louise I.; Holmstrup, Martin; Maraldo, Kristine

    2006-01-01

    The soil fauna communities were described for three dominant vegetation types in a high arctic site at Zackenberg, Northeast Greenland. Soil samples were extracted to quantify the densities of mites, collembolans, enchytraeids, diptera larvae, nematodes and protozoa. Rates of microbial respiration...... densities (naked amoeba and heterotrophic flagellates) were equal. Respiration rate of unamended soil was similar in soil from the three plots. However, a higher respiration rate increase in carbon + nutrient amended soil and the higher densities of soil fauna (with the exception of mites and protozoa...... were also assessed. Collembolans were found in highest densities in dry heath soil, about 130,000 individuals m-2, more than twice as high as in mesic heath soils. Enchytraeids, diptera larvae and nematodes were also more abundant in the dry heath soil than in mesic heath soils, whereas protozoan...

  19. Occurrence of weak, sub-micron, tropospheric aerosol events at high Arctic latitudes

    Science.gov (United States)

    O'Neill, N. T.; Pancrati, O.; Baibakov, K.; Eloranta, E.; Batchelor, R. L.; Freemantle, J.; McArthur, L. J. B.; Strong, K.; Lindenmaier, R.

    2008-07-01

    Numerous fine mode (sub-micron) aerosol optical events were observed during the summer of 2007 at the High Arctic atmospheric observatory (PEARL) located at Eureka, Nunavut, Canada. Half of these events could be traced to forest fires in southern and eastern Russia and the Northwest Territories of Canada. The most notable findings were that (a) a combination of ground-based measurements (passive sunphotometry, high spectral resolution lidar) could be employed to determine that weak (near sub-visual) fine mode events had occurred, and (b) this data combined with remote sensing imagery products (MODIS, OMI-AI, FLAMBE fire sources), Fourier transform spectroscopy and back trajectories could be employed to identify the smoke events.

  20. Development of high current electron beam generator

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Byeong Cheol; Lee, Jong Min; Kim, Sun Kook [and others

    1997-05-01

    A high-current electron beam generator has been developed. The energy and the average current of the electron beam are 2 MeV and 50 mA, respectively. The electron beam generator is composed of an electron gun, RF acceleration cavities, a 260-kW RF generator, electron beam optics components, and control system, etc. The electron beam generator will be used for the development of a millimeter-wave free-electron laser and a high average power infrared free-electron laser. The machine will also be used as a user facility in nuclear industry, environment industry, semiconductor industry, chemical industry, etc. (author). 15 tabs., 85 figs.

  1. Development of high current electron beam generator

    International Nuclear Information System (INIS)

    Lee, Byeong Cheol; Lee, Jong Min; Kim, Sun Kook

    1997-05-01

    A high-current electron beam generator has been developed. The energy and the average current of the electron beam are 2 MeV and 50 mA, respectively. The electron beam generator is composed of an electron gun, RF acceleration cavities, a 260-kW RF generator, electron beam optics components, and control system, etc. The electron beam generator will be used for the development of a millimeter-wave free-electron laser and a high average power infrared free-electron laser. The machine will also be used as a user facility in nuclear industry, environment industry, semiconductor industry, chemical industry, etc. (author). 15 tabs., 85 figs

  2. Documenting PyroCb Development on High-Intensity Boreal Fires: Implications for the Arctic Atmosphere

    Science.gov (United States)

    Stocks, B. J.; Fromm, M. D.; Servranckx, R.; Lindsey, D.

    2007-12-01

    The recent confirmation that smoke from high-intensity boreal forest fires can reach the Upper Troposphere/Lower Stratosphere (UTLS) through pyroconvection and be transported long distances has raised concern over the wider-scale environmental impact of boreal fire smoke. This concern is further elevated as climate change projections indicate a significant increase in the frequency and severity of boreal forest fires over the next century. Smoke in the UTLS is frequently transported to the Arctic and may have important implications for the radiative energy budget in the polar region. Soot deposition from fires may lead to enhanced melting of sea ice and glaciers, and the chemical impact of fire emissions at high altitudes is largely unknown. This knowledge gap will be addressed during the International Polar Year (IPY), as boreal fire emissions will be tracked and documented in detail through aerial, satellite and ground-based measurements, as a key component of the POLARCAT (Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols, and Transport) and ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) projects to be conducted in 2008. A large fire in the Canadian Northwest Territories burned throughout the month of June 2007, in a remote region where forest fires are not actively suppressed, eventually reaching 90,000 hectares in size. This fire was monitored for blowup one week in advance; it erupted into pyroconvection on June 25, 2007. We present an analysis of this event combining satellite data with ground-based measurements to document the development and impact of this classic pyroCb event. Under extreme fire danger conditions, the fire burned close to 20,000 hectares on that day. Fire behavior was consistent with predictions using the Canadian Fire Behavior Prediction System, with the fire spreading at 2.7 km/hr, consuming 33,000 kg of fuel hourly, generating an

  3. Carbon Bioavailability in a High Arctic Fjord Influenced by Glacial Meltwater, NE Greenland

    Directory of Open Access Journals (Sweden)

    Maria L. Paulsen

    2017-06-01

    Full Text Available The land-to-ocean flux of organic carbon is increasing in glacierized regions in response to increasing temperatures in the Arctic (Hood et al., 2015. In order to understand the response of the coastal ecosystem metabolism to the organic carbon input it is essential to determine the bioavailability of the different carbon sources in the system. We quantified the bacterial turnover of organic carbon in a high Arctic fjord system (Young Sound, NE Greenland during the ice-free period (July-October 2014 and assessed the quality and quantity of the 3 major organic carbon sources; (1 local phytoplankton production (2 runoff from land-terminating glaciers and a lowland river and (3 inflow from the ocean shelf. We found that despite relatively low concentrations of DOC in the rivers, the bioavailability of the river–DOC was significantly higher than in the fjord, and characterized by high cell-specific bacterial production and low C:N ratios. In contrast, the DOC source entering via inflow of coastal shelf waters had high DOC concentrations with high C:N and low specific bacterial production. The phytoplankton production in the fjord could not sustain the bacterial carbon demand, but was still the major source of organic carbon for bacterial growth. We assessed the bacterial community composition and found that communities were specific for the different water types i.e., the bacterial community of the coastal inflow water could be traced mainly in the subsurface water, while the glacial river community strongly dominated the surface water in the fjord.

  4. Annual CO2 budget and seasonal CO2 exchange signals at a high Arctic permafrost site on Spitsbergen, Svalbard archipelago

    DEFF Research Database (Denmark)

    Luërs, J.; Westermann, Signe; Piel, K.

    2014-01-01

    -lasting snow cover, and several months of darkness. This study presents a complete annual cycle of the CO2 net ecosystem exchange (NEE) dynamics for a high Arctic tundra area at the west coast of Svalbard based on eddy covariance flux measurements. The annual cumulative CO2 budget is close to 0 g C m-2 yr-1...

  5. Pyrosequencing analysis of the protist communities in a High Arctic meromictic lake: DNA preservation and change

    Directory of Open Access Journals (Sweden)

    Sophie eCharvet

    2012-12-01

    Full Text Available High Arctic meromictic lakes are extreme environments characterized by cold temperatures, low nutrient inputs from their polar desert catchments and prolonged periods of low irradiance and darkness. These lakes are permanently stratified with an oxygenated freshwater layer (mixolimnion overlying a saline, anoxic water column (monimolimnion. The physical and chemical properties of the deepest known lake of this type in the circumpolar Arctic, Lake A, on the far northern coast of Ellesmere Island, Canada, have been studied over the last 15 years, but little is known about the lake’s biological communities. We applied high-throughput sequencing of the V4 region of the 18S ribosomal RNA gene to investigate the protist communities down the water column at three sampling times: under the ice at the end of winter in 2008, during an unusual period of warming and ice-out the same year, and again under the ice in mid-summer 2009. Sequences of many protist taxa occurred throughout the water column at all sampling times, including in the deep anoxic layer where growth is highly unlikely. Furthermore, there were sequences for taxonomic groups including diatoms and marine taxa, which have never been observed in Lake A by microscopic analysis. However the sequences of other taxa such as ciliates, chrysophytes, Cercozoa and Telonema varied with depth, between years and during the transition to ice-free conditions. These results imply that there are seasonally active taxa in the surface waters of the lake that are sensitive to depth and change with time. DNA from these taxa is superimposed upon background DNA from multiple internal and external sources that is preserved in the deep, cold, largely anoxic water column.

  6. On the physical controls of the carbon dioxide balance at a high arctic site in Svalbard

    International Nuclear Information System (INIS)

    Lloyd, C.R.

    2001-01-01

    Current predictions of the effects of climate change indicate that the Arctic may experience a larger than average increase in temperature with consequent changes to the length of the snow-free active summer period, winter snow depth and amount and frequency of summer precipitation being highly probable. This paper reports on measurements of carbon dioxide flux at a high arctic site at Ny-Aalesund (78 o 56' N, 11 o 55' E), Svalbard and the physical climate variables that largely control this flux. lt is shown that during three important precipitation-free periods of the active summer period, namely post snow melt, high summer, and early autumn, the net balance between CO 2 flux from the soil (due to respiration of roots and soil organisms) and CO 2 assimilation by the vegetation is controlled largely by soil temperature and solar radiation. A simple combined photosynthetic assimilation-soil respiration model is shown to be capable of simulating the net CO 2 flux during mid-summer, but is less proficient in the post snow melt period and in early autumn when the simple models' inability to simulate the effects of emergent growth and ponding during the former and senescence, freezing temperatures and dew during the latter indicates the need for a more complex descriptive model. The net CO 2 flux during the measurement periods progresses from a net CO 2 source of 0.3 gC m -2 d -1 during late snow melt to a mid summer net CO 2 sink of -0.39 gC m -2 d -1 , returning to a net CO 2 source of 0.1 gC m -2 d -1 in the early autumn. Simple extrapolation of the data indicates that, during the active summer season in 1995, this site was a net sink of CO 2 of approximately -9 gC m -2 . (author)

  7. A Decade of High-Resolution Arctic Sea Ice Measurements from Airborne Altimetry

    Science.gov (United States)

    Duncan, K.; Farrell, S. L.; Connor, L. N.; Jackson, C.; Richter-Menge, J.

    2017-12-01

    Satellite altimeters carried on board ERS-1,-2, EnviSat, ICESat, CryoSat-2, AltiKa and Sentinel-3 have transformed our ability to map the thickness and volume of the polar sea ice cover, on seasonal and decadal time-scales. The era of polar satellite altimetry has coincided with a rapid decline of the Arctic ice cover, which has thinned, and transitioned from a predominantly multi-year to first-year ice cover. In conjunction with basin-scale satellite altimeter observations, airborne surveys of the Arctic Ocean at the end of winter are now routine. These surveys have been targeted to monitor regions of rapid change, and are designed to obtain the full snow and ice thickness distribution, across a range of ice types. Sensors routinely deployed as part of NASA's Operation IceBridge (OIB) campaigns include the Airborne Topographic Mapper (ATM) laser altimeter, the frequency-modulated continuous-wave snow radar, and the Digital Mapping System (DMS). Airborne measurements yield high-resolution data products and thus present a unique opportunity to assess the quality and characteristics of the satellite observations. We present a suite of sea ice data products that describe the snow depth and thickness of the Arctic ice cover during the last decade. Fields were derived from OIB measurements collected between 2009-2017, and from reprocessed data collected during ad-hoc sea ice campaigns prior to OIB. Our bespoke algorithms are designed to accommodate the heterogeneous sea ice surface topography, that varies at short spatial scales. We assess regional and inter-annual variability in the sea ice thickness distribution. Results are compared to satellite-derived ice thickness fields to highlight the sensitivities of satellite footprints to the tails of the thickness distribution. We also show changes in the dynamic forcing shaping the ice pack over the last eight years through an analysis of pressure-ridge sail-height distributions and surface roughness conditions

  8. Survival of rapidly fluctuating natural low winter temperatures by High Arctic soil invertebrates

    DEFF Research Database (Denmark)

    Convey, Peter; Abbandonato, Holly; Bergan, Frode

    2015-01-01

    The extreme polar environment creates challenges for its resident invertebrate communities and the stress tolerance of some of these animals has been examined over many years. However, although it is well appreciated that standard air temperature records often fail to describe accurately conditions...... microhabitats. To assess survival of natural High Arctic soil invertebrate communities contained in soil and vegetation cores to natural winter temperature variations, the overwintering temperatures they experienced were manipulated by deploying cores in locations with varying snow accumulation: No Snow...... and did not decrease below -12. °C. Those under deep snow were even more stable and did not decline below -2. °C. Despite these striking differences in winter thermal regimes, there were no clear differences in survival of the invertebrate fauna between treatments, including oribatid, prostigmatid...

  9. Thick-billed murres from the High Arctic have the luxury of being lazy!

    DEFF Research Database (Denmark)

    Linnebjerg, Jannie; Tremblay, Yann; Mosbech, Anders

    cold waters where energy consumption is low. This causes potential problems for homoeothermic predators, which require constant access to nutritious prey to survive or large body lipid reserves. Diving birds are particularly vulnerable to periods of low prey availability and many species therefore......Aquatic environments in the temperate, boreal and arctic climate zones are highly seasonal in terms of biological productivity. Many poikilothermic aquatic organisms survive the winter, when food availability is low, by reducing their activity levels and/or performing vertical migrations to deep...... resolve this by migrating to warmer waters, where locating food is energetically less challenging. Migration by flight, however, is extremely energetically costly for birds with wings specialized for underwater swimming. Little is known of how they manage to obtain sufficient energy during migration...

  10. Reconstruction of a high-resolution late holocene arctic paleoclimate record from Colville River delta sediments.

    Energy Technology Data Exchange (ETDEWEB)

    Schreiner, Kathryn Melissa; Lowry, Thomas Stephen

    2013-10-01

    This work was partially supported by the Sandia National Laboratories, Laboratory Directed Research and Development (LDRD) fellowship program in conjunction with Texas A&M University (TAMU). The research described herein is the work of Kathryn M. Schreiner (Katie) and her advisor, Thomas S. Bianchi and represents a concise description of Katies dissertation that was submitted to the TAMU Office of Graduate Studies in May 2013 in partial fulfillment of her doctorate of philosophy degree. High Arctic permafrost soils contain a massive amount of organic carbon, accounting for twice as much carbon as what is currently stored as carbon dioxide in the atmosphere. However, with current warming trends this sink is in danger of thawing and potentially releasing large amounts of carbon as both carbon dioxide and methane into the atmosphere. It is difficult to make predictions about the future of this sink without knowing how it has reacted to past temperature and climate changes. This project investigated long term, fine scale particulate organic carbon (POC) delivery by the high-Arctic Colville River into Simpsons Lagoon in the near-shore Beaufort Sea. Modern POC was determined to be a mixture of three sources (riverine soils, coastal erosion, and marine). Downcore POC measurements were performed in a core close to the Colville River output and a core close to intense coastal erosion. Inputs of the three major sources were found to vary throughout the last two millennia, and in the Colville River core covary significantly with Alaskan temperature reconstructions.

  11. Clay mineralogy, strontium and neodymium isotope ratios in the sediments of two High Arctic catchments (Svalbard)

    Science.gov (United States)

    Hindshaw, Ruth S.; Tosca, Nicholas J.; Piotrowski, Alexander M.; Tipper, Edward T.

    2018-03-01

    The identification of sediment sources to the ocean is a prerequisite to using marine sediment cores to extract information on past climate and ocean circulation. Sr and Nd isotopes are classical tools with which to trace source provenance. Despite considerable interest in the Arctic Ocean, the circum-Arctic source regions are poorly characterised in terms of their Sr and Nd isotopic compositions. In this study we present Sr and Nd isotope data from the Paleogene Central Basin sediments of Svalbard, including the first published data of stream suspended sediments from Svalbard. The stream suspended sediments exhibit considerable isotopic variation (ɛNd = -20.6 to -13.4; 87Sr / 86Sr = 0.73421 to 0.74704) which can be related to the depositional history of the sedimentary formations from which they are derived. In combination with analysis of the clay mineralogy of catchment rocks and sediments, we suggest that the Central Basin sedimentary rocks were derived from two sources. One source is Proterozoic sediments derived from Greenlandic basement rocks which are rich in illite and have high 87Sr / 86Sr and low ɛNd values. The second source is Carboniferous to Jurassic sediments derived from Siberian basalts which are rich in smectite and have low 87Sr / 86Sr and high ɛNd values. Due to a change in depositional conditions throughout the Paleogene (from deep sea to continental) the relative proportions of these two sources vary in the Central Basin formations. The modern stream suspended sediment isotopic composition is then controlled by modern processes, in particular glaciation, which determines the present-day exposure of the formations and therefore the relative contribution of each formation to the stream suspended sediment load. This study demonstrates that the Nd isotopic composition of stream suspended sediments exhibits seasonal variation, which likely mirrors longer-term hydrological changes, with implications for source provenance studies based on fixed

  12. Resource utilisation by deep-sea megabenthos in the Canadian High Arctic (Baffin Bay and Parry Channel)

    Science.gov (United States)

    Bourgeois, Solveig; Witte, Ursula; Harrison, Ailish M.; Makela, Anni; Kazanidis, Georgios; Archambault, Philippe

    2016-04-01

    Ongoing climate change in the Arctic is causing drastic alteration of the Arctic marine ecosystem functioning, such as shifts in patterns of primary production, and modifying the present tight pelagic-benthic coupling. Subsequently benthic communities, which rely upon organic matter produced in the top layers of the Ocean, will also be affected by these changes. The benthic megafaunal communities play a significant role in ecological processes and ecosystem functioning (i.e. organic matter recycling, bioturbation, food source for the higher trophic levels…). Yet, information is scarce regarding the main food sources for dominant benthic organisms, and therefore the impact of the ongoing changes is difficult to assess. The goal of this study is to investigate the preferential feeding of different carbon sources by megabenthic organisms in the Canadian High Arctic and to identify environmental drivers which explain the observed trends. In summer 2013, benthic megafauna was collected at 9 stations spread along latitudinal (58 to 81°N) and longitudinal (62 to 114°W) transects in the Baffin Bay and Parry Channel, respectively. Carbon and nitrogen bulk stable isotope analyses (δ13C and δ15N) were performed on several species divided into groups according to their feeding type. This study highlights distinct trends in δ13C values of benthic organisms suggesting the importance of both phytoplankton and ice algae as carbon sources for megafauna in the Canadian High Arctic. The importance of physical and biological parameters as drivers of food web structure will be furthermore discussed.

  13. High-energy electron diffraction and microscopy

    CERN Document Server

    Peng, L M; Whelan, M J

    2011-01-01

    This book provides a comprehensive introduction to high energy electron diffraction and elastic and inelastic scattering of high energy electrons, with particular emphasis on applications to modern electron microscopy. Starting from a survey of fundamental phenomena, the authors introduce the most important concepts underlying modern understanding of high energy electron diffraction. Dynamical diffraction in transmission (THEED) and reflection (RHEED) geometries is treated using ageneral matrix theory, where computer programs and worked examples are provided to illustrate the concepts and to f

  14. High-resolution electron microscopy

    CERN Document Server

    Spence, John C H

    2013-01-01

    This new fourth edition of the standard text on atomic-resolution transmission electron microscopy (TEM) retains previous material on the fundamentals of electron optics and aberration correction, linear imaging theory (including wave aberrations to fifth order) with partial coherence, and multiple-scattering theory. Also preserved are updated earlier sections on practical methods, with detailed step-by-step accounts of the procedures needed to obtain the highest quality images of atoms and molecules using a modern TEM or STEM electron microscope. Applications sections have been updated - these include the semiconductor industry, superconductor research, solid state chemistry and nanoscience, and metallurgy, mineralogy, condensed matter physics, materials science and material on cryo-electron microscopy for structural biology. New or expanded sections have been added on electron holography, aberration correction, field-emission guns, imaging filters, super-resolution methods, Ptychography, Ronchigrams, tomogr...

  15. Using High Spatio-Temporal Optical Remote Sensing to Monitor Dissolved Organic Carbon in the Arctic River Yenisei

    Directory of Open Access Journals (Sweden)

    Pierre-Alexis Herrault

    2016-09-01

    Full Text Available In Arctic regions, a major concern is the release of carbon from melting permafrost that could greatly exceed current human carbon emissions. Arctic rivers drain these organic-rich watersheds (Ob, Lena, Yenisei, Mackenzie, Yukon but field measurements at the outlets of these great Arctic rivers are constrained by limited accessibility of sampling sites. In particular, the highest dissolved organic carbon (DOC fluxes are observed throughout the ice breakup period that occurs over a short two to three-week period in late May or early June during the snowmelt-generated peak flow. The colored fraction of dissolved organic carbon (DOC which absorbs UV and visible light is designed as chromophoric dissolved organic matter (CDOM. It is highly correlated to DOC in large arctic rivers and streams, allowing for remote sensing to monitor DOC concentrations from satellite imagery. High temporal and spatial resolutions remote sensing tools are highly relevant for the study of DOC fluxes in a large Arctic river. The high temporal resolution allows for correctly assessing this highly dynamic process, especially the spring freshet event (a few weeks in May. The high spatial resolution allows for assessing the spatial variability within the stream and quantifying DOC transfer during the ice break period when the access to the river is almost impossible. In this study, we develop a CDOM retrieval algorithm at a high spatial and a high temporal resolution in the Yenisei River. We used extensive DOC and DOM spectral absorbance datasets from 2014 and 2015. Twelve SPOT5 (Take5 and Landsat 8 (OLI images from 2014 and 2015 were examined for this investigation. Relationships between CDOM and spectral variables were explored using linear models (LM. Results demonstrated the capacity of a CDOM algorithm retrieval to monitor DOC fluxes in the Yenisei River during a whole open water season with a special focus on the peak flow period. Overall, future Sentinel2/Landsat8

  16. A case study of high Arctic anthropogenic disturbance to polar desert permafrost and ecosystems

    Science.gov (United States)

    Becker, M. S.; Pollard, W. H.

    2013-12-01

    One of the indirect impacts of climate change on Arctic ecosystems is the expected increase of industrial development in high latitudes. The scale of terrestrial impacts cannot be known ahead of time, particularly due to a lack of long-term impact studies in this region. With one of the slowest community recovery rates of any ecosystem, the high Artic biome will be under a considerable threat that is exacerbated by a high susceptibility to change in the permafrost thermal balance. One such area that provides a suitable location for study is an old airstrip near Eureka, Ellesmere Island, Nunavut (80.0175°N, 85.7340°W). While primarily used as an ice-runway for winter transport, the airstrip endured a yearly summer removal of vegetation that continued from 1947 until its abandonment in 1951. Since then, significant vegetative and geomorphic differences between disturbed and undisturbed areas have been noted in the literature throughout the decades (Bruggemann, 1953; Beschel, 1963; Couture and Pollard, 2007), but no system wide assessment of both the ecosystem and near-surface permafrost has been conducted. Key to our study is that the greatest apparent geomorphic and vegetative changes have occurred and persisted in areas where underlying ice-wedges have been disturbed. This suggests that the colonizing communities rapidly filled new available thermokarst niches and have produced an alternative ice-wedge stable state than the surrounding polar desert. We hypothesize that disturbed areas will currently have greater depths of thaw (deeper active layers) and degraded ice-wedges, with decreased vegetation diversity but higher abundance due to a changed hydrological balance. To test this a comprehensive set of near-surface active layer and ecosystem measurements were conducted. Permafrost dynamics were characterized using probing and high-frequency Ground Penetrating Radar (500 MHz) to map the near-surface details of ice-wedges and active layer. Vegetation was measured

  17. Arctic circulation regimes.

    Science.gov (United States)

    Proshutinsky, Andrey; Dukhovskoy, Dmitry; Timmermans, Mary-Louise; Krishfield, Richard; Bamber, Jonathan L

    2015-10-13

    Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability. © 2015 The Authors.

  18. Arctic Haze Analysis

    Science.gov (United States)

    Mei, Linlu; Xue, Yong

    2013-04-01

    The Arctic atmosphere is perturbed by nature/anthropogenic aerosol sources known as the Arctic haze, was firstly observed in 1956 by J. Murray Mitchell in Alaska (Mitchell, 1956). Pacyna and Shaw (1992) summarized that Arctic haze is a mixture of anthropogenic and natural pollutants from a variety of sources in different geographical areas at altitudes from 2 to 4 or 5 km while the source for layers of polluted air at altitudes below 2.5 km mainly comes from episodic transportation of anthropogenic sources situated closer to the Arctic. Arctic haze of low troposphere was found to be of a very strong seasonal variation characterized by a summer minimum and a winter maximum in Alaskan (Barrie, 1986; Shaw, 1995) and other Arctic region (Xie and Hopke, 1999). An anthropogenic factor dominated by together with metallic species like Pb, Zn, V, As, Sb, In, etc. and nature source such as sea salt factor consisting mainly of Cl, Na, and K (Xie and Hopke, 1999), dust containing Fe, Al and so on (Rahn et al.,1977). Black carbon and soot can also be included during summer time because of the mix of smoke from wildfires. The Arctic air mass is a unique meteorological feature of the troposphere characterized by sub-zero temperatures, little precipitation, stable stratification that prevents strong vertical mixing and low levels of solar radiations (Barrie, 1986), causing less pollutants was scavenged, the major revival pathway for particulates from the atmosphere in Arctic (Shaw, 1981, 1995; Heintzenberg and Larssen, 1983). Due to the special meteorological condition mentioned above, we can conclude that Eurasian is the main contributor of the Arctic pollutants and the strong transport into the Arctic from Eurasia during winter caused by the high pressure of the climatologically persistent Siberian high pressure region (Barrie, 1986). The paper intends to address the atmospheric characteristics of Arctic haze by comparing the clear day and haze day using different dataset

  19. Salix polaris growth responses to active layer detachment and solifluction processes in High Arctic.

    Science.gov (United States)

    Siekacz, Liliana

    2015-04-01

    The work is dedicated to demonstrate the potential of Salix polaris grow properties in the dendrogemorphologic image, analyzing periglacially induced slope processes in the high Arctic.. Observed anatomical and morphological plants responses to solifluction and active layer detachment processes are presented qualitatively and quantitatively as a summary of presented features frequency. The results are discussed against the background of the other research results in this field. The investigations was performed in Ebba valley, in the vicinity of Petunia Bay, northernmost part of Billefjorden in central Spitsbergen (Svalbard). Environmental conditions are characterized by annual precipitation sum lower than 200 mm (Hagen et al.,1993) and average summer temperature of about 5°C, with maximum daily temperatures rarely exceeding 10°C (Rachlewicz, 2009). Collected shrub material was prepared according to the methods presented by Schweingruber and Poschlod (2005). Thin (approx. 15-20μm) sections of the whole cross-section were prepared with a sledge microtome, stained with Safranine and Astra blue and finally permanently fixed on microslides with Canada balsam and dried. Snapshots were taken partially for each cross-section with digital camera (ColorView III, Olympus) connected to a microscope (Olympus BX41) and merged into one, high resolution image. After all, ring widths were measured in 3-4 radii in every single cross-section using ImageJ software. Analyzed plants revealed extremely harsh environmental conditions of their growth. Buchwał et al. (2013) provided quantitative data concerning missing rings and partially missing rings in shrubs growing on Ebba valley floor. Mean ring width at the level of 79μm represents one of the smallest values of yearly growth ever noted. The share of missing rings and partially missing rings was 11,2% and 13,6% respectively. Plants growing on Ebba valley slope indicate almost twice smaller values of ring width (41μm), and higher

  20. Arctic Newcomers

    DEFF Research Database (Denmark)

    Tonami, Aki

    2013-01-01

    Interest in the Arctic region and its economic potential in Japan, South Korea and Singapore was slow to develop but is now rapidly growing. All three countries have in recent years accelerated their engagement with Arctic states, laying the institutional frameworks needed to better understand...... and influence policies relating to the Arctic. But each country’s approach is quite different, writes Aki Tonami....

  1. Quantifying snow and vegetation interactions in the high arctic based on ground penetrating radar (GPR)

    DEFF Research Database (Denmark)

    Gacitúa, G.; Bay, C.; Tamstorf, M.

    2013-01-01

    Arctic in Northeast Greenland. We used ground penetrating radar (GPR) for snow thickness measurements across the Zackenberg valley. Measurements were integrated to the physical conditions that support the vegetation distribution. Descriptive statistics and correlations of the distribution of each...

  2. Glacier inputs influence organic matter composition and prokaryotic distribution in a high Arctic fjord (Kongsfjorden, Svalbard)

    KAUST Repository

    Bourgeois, Solveig; Kerhervé , Philippe; Calleja, Maria Ll; Many, Gaë l; Morata, Nathalie

    2016-01-01

    With climate change, the strong seasonality and tight pelagic-benthic coupling in the Arctic is expected to change in the next few decades. It is currently unclear how the benthos will be affected by changes of environmental conditions

  3. Advanced Ecosystem Mapping Techniques for Large Arctic Study Domains Using Calibrated High-Resolution Imagery

    Science.gov (United States)

    Macander, M. J.; Frost, G. V., Jr.

    2015-12-01

    Regional-scale mapping of vegetation and other ecosystem properties has traditionally relied on medium-resolution remote sensing such as Landsat (30 m) and MODIS (250 m). Yet, the burgeoning availability of high-resolution (environments has not been previously evaluated. Image segmentation, or object-based image analysis, automatically partitions high-resolution imagery into homogeneous image regions that can then be analyzed based on spectral, textural, and contextual information. We applied eCognition software to delineate waterbodies and vegetation classes, in combination with other techniques. Texture metrics were evaluated to determine the feasibility of using high-resolution imagery to algorithmically characterize periglacial surface forms (e.g., ice-wedge polygons), which are an important physical characteristic of permafrost-dominated regions but which cannot be distinguished by medium-resolution remote sensing. These advanced mapping techniques provide products which can provide essential information supporting a broad range of ecosystem science and land-use planning applications in northern Alaska and elsewhere in the circumpolar Arctic.

  4. The Eindhoven High-Brightness Electron Programme

    NARCIS (Netherlands)

    Brussaard, G.J.H.; Wiel, van der M.J.

    2004-01-01

    The Eindhoven High-Brightness programme is aimed at producing ultra-short intense electron bunches from compact accelerators. The RF electron gun is capable of producing 100 fs electron bunches at 7.5 MeV and 10 pC bunch charge. The DC/RF hybrid gun under development will produce bunches <75 fs at

  5. High electron mobility InN

    International Nuclear Information System (INIS)

    Jones, R. E.; Li, S. X.; Haller, E. E.; van Genuchten, H. C. M.; Yu, K. M.; Ager, J. W. III; Liliental-Weber, Z.; Walukiewicz, W.; Lu, H.; Schaff, W. J.

    2007-01-01

    Irradiation of InN films with 2 MeV He + ions followed by thermal annealing below 500 deg. C creates films with high electron concentrations and mobilities, as well as strong photoluminescence. Calculations show that electron mobility in irradiated samples is limited by triply charged donor defects. Subsequent thermal annealing removes a fraction of the defects, decreasing the electron concentration. There is a large increase in electron mobility upon annealing; the mobilities approach those of the as-grown films, which have 10 to 100 times smaller electron concentrations. Spatial ordering of the triply charged defects is suggested to cause the unusual increase in electron mobility

  6. Size-resolved atmospheric particulate polysaccharides in the high summer Arctic

    Science.gov (United States)

    Leck, C.; Gao, Q.; Mashayekhy Rad, F.; Nilsson, U.

    2013-12-01

    Size-resolved aerosol samples for subsequent quantitative determination of polymer sugars (polysaccharides) after hydrolysis to their subunit monomers (monosaccharides) were collected in surface air over the central Arctic Ocean during the biologically most active summer period. The analysis was carried out by novel use of liquid chromatography coupled with highly selective and sensitive tandem mass spectrometry. Polysaccharides were detected in particle sizes ranging from 0.035 to 10 μm in diameter with distinct features of heteropolysaccharides, enriched in xylose, glucose + mannose as well as a substantial fraction of deoxysugars. Polysaccharides, containing deoxysugar monomers, showed a bimodal size structure with about 70% of their mass found in the Aitken mode over the pack ice area. Pentose (xylose) and hexose (glucose + mannose) had a weaker bimodal character and were largely found with super-micrometer sizes and in addition with a minor sub-micrometer fraction. The concentration of total hydrolysable neutral sugars (THNS) in the samples collected varied over two orders of magnitude (1 to 160 pmol m-3) in the super-micrometer size fraction and to a somewhat lesser extent in sub-micrometer particles (4 to 140 pmol m-3). Lowest THNS concentrations were observed in air masses that had spent more than five days over the pack ice. Within the pack ice area, about 53% of the mass of hydrolyzed polysaccharides was detected in sub-micrometer particles. The relative abundance of sub-micrometer hydrolyzed polysaccharides could be related to the length of time that the air mass spent over pack ice, with the highest fraction (> 90%) observed for > 7 days of advection. The aerosol samples collected onboard ship showed similar monosaccharide composition, compared to particles generated experimentally in situ at the expedition's open lead site. This supports the existence of a primary particle source of polysaccharide containing polymer gels from open leads by bubble

  7. High bacterial diversity of biological soil crusts in water tracks over permafrost in the high arctic polar desert.

    Science.gov (United States)

    Steven, Blaire; Lionard, Marie; Kuske, Cheryl R; Vincent, Warwick F

    2013-01-01

    In this study we report the bacterial diversity of biological soil crusts (biocrusts) inhabiting polar desert soils at the northern land limit of the Arctic polar region (83° 05 N). Employing pyrosequencing of bacterial 16S rRNA genes this study demonstrated that these biocrusts harbor diverse bacterial communities, often as diverse as temperate latitude communities. The effect of wetting pulses on the composition of communities was also determined by collecting samples from soils outside and inside of permafrost water tracks, hill slope flow paths that drain permafrost-affected soils. The intermittent flow regime in the water tracks was correlated with altered relative abundance of phylum level taxonomic bins in the bacterial communities, but the alterations varied between individual sampling sites. Bacteria related to the Cyanobacteria and Acidobacteria demonstrated shifts in relative abundance based on their location either inside or outside of the water tracks. Among cyanobacterial sequences, the proportion of sequences belonging to the family Oscillatoriales consistently increased in relative abundance in the samples from inside the water tracks compared to those outside. Acidobacteria showed responses to wetting pulses in the water tracks, increasing in abundance at one site and decreasing at the other two sites. Subdivision 4 acidobacterial sequences tended to follow the trends in the total Acidobacteria relative abundance, suggesting these organisms were largely responsible for the changes observed in the Acidobacteria. Taken together, these data suggest that the bacterial communities of these high latitude polar biocrusts are diverse but do not show a consensus response to intermittent flow in water tracks over high Arctic permafrost.

  8. Diel Variation of Biogenic Volatile Organic Compound Emissions- A field Study in the Sub, Low and High Arctic on the Effect of Temperature and Light

    Science.gov (United States)

    Lindwall, Frida; Faubert, Patrick; Rinnan, Riikka

    2015-01-01

    Many hours of sunlight in the midnight sun period suggest that significant amounts of biogenic volatile organic compounds (BVOCs) may be released from arctic ecosystems during night-time. However, the emissions from these ecosystems are rarely studied and limited to point measurements during daytime. We measured BVOC emissions during 24-hour periods in the field using a push-pull chamber technique and collection of volatiles in adsorbent cartridges followed by analysis with gas chromatography- mass spectrometry. Five different arctic vegetation communities were examined: high arctic heaths dominated by Salix arctica and Cassiope tetragona, low arctic heaths dominated by Salix glauca and Betula nana and a subarctic peatland dominated by the moss Warnstorfia exannulata and the sedge Eriophorum russeolum. We also addressed how climate warming affects the 24-hour emission and how the daytime emissions respond to sudden darkness. The emissions from the high arctic sites were lowest and had a strong diel variation with almost no emissions during night-time. The low arctic sites as well as the subarctic site had a more stable release of BVOCs during the 24-hour period with night-time emissions in the same range as those during the day. These results warn against overlooking the night period when considering arctic emissions. During the day, the quantity of BVOCs and the number of different compounds emitted was higher under ambient light than in darkness. The monoterpenes α-fenchene, α -phellandrene, 3-carene and α-terpinene as well as isoprene were absent in dark measurements during the day. Warming by open top chambers increased the emission rates both in the high and low arctic sites, forewarning higher emissions in a future warmer climate in the Arctic. PMID:25897519

  9. Diel Variation of Biogenic Volatile Organic Compound Emissions--A field Study in the Sub, Low and High Arctic on the Effect of Temperature and Light.

    Science.gov (United States)

    Lindwall, Frida; Faubert, Patrick; Rinnan, Riikka

    2015-01-01

    Many hours of sunlight in the midnight sun period suggest that significant amounts of biogenic volatile organic compounds (BVOCs) may be released from arctic ecosystems during night-time. However, the emissions from these ecosystems are rarely studied and limited to point measurements during daytime. We measured BVOC emissions during 24-hour periods in the field using a push-pull chamber technique and collection of volatiles in adsorbent cartridges followed by analysis with gas chromatography-mass spectrometry. Five different arctic vegetation communities were examined: high arctic heaths dominated by Salix arctica and Cassiope tetragona, low arctic heaths dominated by Salix glauca and Betula nana and a subarctic peatland dominated by the moss Warnstorfia exannulata and the sedge Eriophorum russeolum. We also addressed how climate warming affects the 24-hour emission and how the daytime emissions respond to sudden darkness. The emissions from the high arctic sites were lowest and had a strong diel variation with almost no emissions during night-time. The low arctic sites as well as the subarctic site had a more stable release of BVOCs during the 24-hour period with night-time emissions in the same range as those during the day. These results warn against overlooking the night period when considering arctic emissions. During the day, the quantity of BVOCs and the number of different compounds emitted was higher under ambient light than in darkness. The monoterpenes α-fenchene, α-phellandrene, 3-carene and α-terpinene as well as isoprene were absent in dark measurements during the day. Warming by open top chambers increased the emission rates both in the high and low arctic sites, forewarning higher emissions in a future warmer climate in the Arctic.

  10. Glacier mass balance in high-arctic areas with anomalous gravity

    Science.gov (United States)

    Sharov, A.; Rieser, D.; Nikolskiy, D.

    2012-04-01

    All known glaciological models describing the evolution of Arctic land- and sea-ice masses in changing climate treat the Earth's gravity as horizontally constant, but it isn't. In the High Arctic, the strength of the gravitational field varies considerably across even short distances under the influence of a density gradient, and the magnitude of free air gravity anomalies attains 100 mGal and more. On long-term base, instantaneous deviations of gravity can have a noticeable effect on the regime and mass budget of glaciological objects. At best, the gravity-induced component of ice mass variations can be determined on topographically smooth, open and steady surfaces, like those of arctic planes, regular ice caps and landfast sea ice. The present research is devoted to studying gravity-driven impacts on glacier mass balance in the outer periphery of four Eurasian shelf seas with a very cold, dry climate and rather episodic character of winter precipitation. As main study objects we had chosen a dozen Russia's northernmost insular ice caps, tens to hundreds of square kilometres in extent, situated in a close vicinity of strong gravity anomalies and surrounded with extensive fields of fast and/or drift ice for most of the year. The supposition about gravitational forcing on glacioclimatic settings in the study region is based on the results of quantitative comparison and joint interpretation of existing glacier change maps and available data on the Arctic gravity field and solid precipitation. The overall mapping of medium-term (from decadal to half-centennial) changes in glacier volumes and quantification of mass balance characteristics in the study region was performed by comparing reference elevation models of study glaciers derived from Russian topographic maps 1:200,000 (CI = 20 or 40 m) representing the glacier state as in the 1950s-1980s with modern elevation data obtained from satellite radar interferometry and lidar altimetry. Free-air gravity anomalies were

  11. Human-induced Arctic moistening.

    Science.gov (United States)

    Min, Seung-Ki; Zhang, Xuebin; Zwiers, Francis

    2008-04-25

    The Arctic and northern subpolar regions are critical for climate change. Ice-albedo feedback amplifies warming in the Arctic, and fluctuations of regional fresh water inflow to the Arctic Ocean modulate the deep ocean circulation and thus exert a strong global influence. By comparing observations to simulations from 22 coupled climate models, we find influence from anthropogenic greenhouse gases and sulfate aerosols in the space-time pattern of precipitation change over high-latitude land areas north of 55 degrees N during the second half of the 20th century. The human-induced Arctic moistening is consistent with observed increases in Arctic river discharge and freshening of Arctic water masses. This result provides new evidence that human activity has contributed to Arctic hydrological change.

  12. Transitions in high-Arctic vegetation growth patterns and ecosystem productivity tracked with automated cameras from 2000 to 2013

    DEFF Research Database (Denmark)

    Westergaard-Nielsen, Andreas; Lund, Magnus; Pedersen, Stine Højlund

    2017-01-01

    Climate-induced changes in vegetation phenology at northern latitudes are still poorly understood. Continued monitoring and research are therefore needed to improve the understanding of abiotic drivers. Here we used 14 years of time lapse imagery and climate data from high-Arctic Northeast...... days, resulting in an unchanged growing season length. Vegetation greenness, derived from the imagery, was correlated to primary productivity, showing that the imagery holds valuable information on vegetation productivity....

  13. Applying High Resolution Imagery to Understand the Role of Dynamics in the Diminishing Arctic Sea Ice Cover

    Science.gov (United States)

    2015-09-30

    describe contemporary ice pack thickness, MODIS , AVHRR, RadarSat-2 (satellite imagery) that describe ice pack deformation features on large scales, as well...high-resolution visible-band images of the Arctic ice pack that are available at the GFL, USGS. The statistics related to the available images are...University of Maryland team as a Faculty Research Assistant, working under the guidance of Co-PI Farrell. Ms. Faber is responsible for analysis of MODIS

  14. Hydroclimate variability of High Arctic Svalbard during the Holocene inferred from hydrogen isotopes of leaf waxes

    Science.gov (United States)

    Balascio, Nicholas L.; D'Andrea, William J.; Gjerde, Marthe; Bakke, Jostein

    2018-03-01

    The response of the Arctic hydrologic cycle to global warming includes changes in precipitation patterns and moisture availability associated with variable sea ice extent and modes of atmospheric circulation. Reconstructions of past hydroclimate changes help constrain the natural range of these systems, identify the manners in which they respond to different forcing mechanisms, and reveal their connections to other components of the climate system, all of which lead to a better understanding of present and future changes. Here we examine hydroclimate changes during the Holocene in the High Arctic archipelago of Svalbard by reconstructing the isotopic composition of precipitation. We measured the hydrogen isotopic composition (δD values) of leaf wax compounds (n-alkanes; C25-C31) in a sediment core from Lake Hakluytvatnet on the island of Amsterdamøya, northwest Spitsbergen. We interpret δD values of mid-chain (C25) and long-chain (C29, C31) length n-alkanes to represent changes in the isotopic composition of lake water and precipitation over the last 12.9 ka. After deglaciation of the catchment, water supply became restricted and the lake experienced significant evaporative isotopic enrichment indicating warmer conditions from 12.8 to 7.5 ka. The isotope values suggest an increase in the delivery of moisture from warmer sub-polar air masses between 12.8 and 9.5 ka, followed by generally warm, but unstable conditions between 9.5 and 7.5 ka, possibly indicating a response to meltwater forcing. Sedimentary evidence indicates a hiatus in deposition c. 7.5-5.0 ka, likely as a result of desiccation of the lake. At c. 5.0 ka lacustrine sedimentation resumed and over the last 5 ka there was a progressive increase in the influence of polar air masses and colder conditions, which culminated in an abrupt shift to colder conditions at c. 1.8 ka. This late Holocene cooling ended c. 0.18 ka, when isotopic data indicate warmer conditions and greater influence of moisture

  15. Significant impacts of nutrient enrichment on High Arctic vegetation and soils despite two decades of recovery

    Science.gov (United States)

    Street, L. E.; Burns, N. R.; Woodin, S. J.

    2012-04-01

    of nutrient enrichment on High Arctic ecosystems are not readily reversible, and that short-term addition of N can result in long-term carbon losses. We show that mosses perform an important role in retaining deposited N aboveground. Our results also highlight the importance of P in mediating carbon cycle responses to increased N availability.

  16. Application of Low-Cost UASs and Digital Photogrammetry for High-Resolution Snow Depth Mapping in the Arctic

    DEFF Research Database (Denmark)

    Cimoli, Emiliano; Marcer, Marco; Vandecrux, Baptiste Robert Marcel

    2017-01-01

    The repeat acquisition of high-resolution snow depth measurements has important research and civil applications in the Arctic. Currently the surveying methods for capturing the high spatial and temporal variability of the snowpack are expensive, in particular for small areal extents. An alternati...... areal extents. While further validation is needed, with the inclusion of extra validation points, the study showcases the potential of this cost-effective methodology for high-resolution monitoring of snow dynamics in the Arctic and beyond....... methodology based on Unmanned Aerial Systems (UASs) and digital photogrammetry was tested over varying surveying conditions in the Arctic employing two diverse and low-cost UAS-camera combinations (500 and 1700 USD, respectively). Six areas, two in Svalbard and four in Greenland, were mapped covering from......-estimated and measured snow depth, checked with conventional snow probing, ranged from 0.015 to 0.16 m. The impact of image pre-processing was explored, improving point cloud density and accuracy for different image qualities and snow/light conditions. Our UAS photogrammetry results are expected to be scalable to larger...

  17. Application of Low-Cost UASs and Digital Photogrammetry for High-Resolution Snow Depth Mapping in the Arctic

    Directory of Open Access Journals (Sweden)

    Emiliano Cimoli

    2017-11-01

    Full Text Available The repeat acquisition of high-resolution snow depth measurements has important research and civil applications in the Arctic. Currently the surveying methods for capturing the high spatial and temporal variability of the snowpack are expensive, in particular for small areal extents. An alternative methodology based on Unmanned Aerial Systems (UASs and digital photogrammetry was tested over varying surveying conditions in the Arctic employing two diverse and low-cost UAS-camera combinations (500 and 1700 USD, respectively. Six areas, two in Svalbard and four in Greenland, were mapped covering from 1386 to 38,410 m2. The sites presented diverse snow surface types, underlying topography and light conditions in order to test the method under potentially limiting conditions. The resulting snow depth maps achieved spatial resolutions between 0.06 and 0.09 m. The average difference between UAS-estimated and measured snow depth, checked with conventional snow probing, ranged from 0.015 to 0.16 m. The impact of image pre-processing was explored, improving point cloud density and accuracy for different image qualities and snow/light conditions. Our UAS photogrammetry results are expected to be scalable to larger areal extents. While further validation is needed, with the inclusion of extra validation points, the study showcases the potential of this cost-effective methodology for high-resolution monitoring of snow dynamics in the Arctic and beyond.

  18. Soil microbial succession along a chronosequence on a High Arctic glacier foreland, Ny-Ålesund, Svalbard: 10 years' change

    Science.gov (United States)

    Yoshitake, Shinpei; Uchida, Masaki; Iimura, Yasuo; Ohtsuka, Toshiyuki; Nakatsubo, Takayuki

    2018-06-01

    Rapid glacial retreat in the High Arctic causes the expansion of new habitats, but the successional trajectories of soil microbial communities are not fully understood. We examined microbial succession along a chronosequence twice with a 10-year interval in a High Arctic glacier foreland. Soil samples were collected from five study sites with different ages and phospholipid fatty acids analysis was conducted to investigate the microbial biomass and community structure. Microbial biomass did not differ significantly between the two sampling times but tended to increase with the chronosequence and showed a significant correlation with soil carbon (C) and nitrogen (N) content. Microbial community structure clearly differed along the chronosequence and was correlated with C and N content. The largest shift in community structure over 10 years was observed in the newly exposed sites after deglaciation. The accumulation of soil organic matter was regarded as an important determinant both of microbial biomass and community structure over the successional period. In contrast, the initial microbial community on the newly exposed soil changed rapidly even in the High Arctic, suggesting that some key soil processes such as C and N cycling can also shift within the relatively short period after rapid glacial retreat.

  19. High Arctic Holocene temperature record from the Agassiz ice cap and Greenland ice sheet evolution.

    Science.gov (United States)

    Lecavalier, Benoit S; Fisher, David A; Milne, Glenn A; Vinther, Bo M; Tarasov, Lev; Huybrechts, Philippe; Lacelle, Denis; Main, Brittany; Zheng, James; Bourgeois, Jocelyne; Dyke, Arthur S

    2017-06-06

    We present a revised and extended high Arctic air temperature reconstruction from a single proxy that spans the past ∼12,000 y (up to 2009 CE). Our reconstruction from the Agassiz ice cap (Ellesmere Island, Canada) indicates an earlier and warmer Holocene thermal maximum with early Holocene temperatures that are 4-5 °C warmer compared with a previous reconstruction, and regularly exceed contemporary values for a period of ∼3,000 y. Our results show that air temperatures in this region are now at their warmest in the past 6,800-7,800 y, and that the recent rate of temperature change is unprecedented over the entire Holocene. The warmer early Holocene inferred from the Agassiz ice core leads to an estimated ∼1 km of ice thinning in northwest Greenland during the early Holocene using the Camp Century ice core. Ice modeling results show that this large thinning is consistent with our air temperature reconstruction. The modeling results also demonstrate the broader significance of the enhanced warming, with a retreat of the northern ice margin behind its present position in the mid Holocene and a ∼25% increase in total Greenland ice sheet mass loss (∼1.4 m sea-level equivalent) during the last deglaciation, both of which have implications for interpreting geodetic measurements of land uplift and gravity changes in northern Greenland.

  20. ASTER-Derived High-Resolution Ice Surface Temperature for the Arctic Coast

    Directory of Open Access Journals (Sweden)

    Young-Sun Son

    2018-04-01

    Full Text Available Ice surface temperature (IST controls the rate of sea ice growth and the heat exchange between the atmosphere and ocean. In this study, high-resolution IST using the Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER thermal infrared region (TIR images was retrieved to observe the thermal change of coastal sea ice. The regression coefficients of the multi-channel equation using ASTER brightness temperatures ( B T and MODIS ISTs were derived. MODIS IST products (MOD29 were used as an in situ temperature substitute. The ASTER IST using five channels from band 10 ( B T 10 to band 14 ( B T 14 showed an RMSE of 0.746 K for the validation images on the Alaskan coast. The uncertainty of the two-channel ( B T 13 and B T 14 ASTER IST was 0.497 K, which was better than that of the five-channel. We thus concluded that the two-channel equation using ASTER B T 13 and B T 14 was an optimal model for the surface temperature retrieval of coastal sea ice. The two-channel ASTER IST showed similar accuracy at higher latitudes than in Alaska. Therefore, ASTER-derived IST with 90 m spatial resolution can be used to observe small-scale thermal variations on the sea ice surface along the Arctic coast.

  1. Ambient UV-B radiation decreases photosynthesis in high arctic Vaccinium uliginosum

    Energy Technology Data Exchange (ETDEWEB)

    Albert, K.R.; Ro-Poulsen, H. (Univ. of Copenhagen, Dept. of Terrestrial Ecology, Copenhagen (DK)); Mikkelsen, T.N. (Technical Univ. of Denmark, Risoe National Laboratory for Sustainable Energy, Biosystems Dept., Roskilde (DK))

    2008-06-15

    An UV-B-exclusion experiment was established in high arctic Zackenberg, Northeast Greenland, to investigate the possible effects of ambient UV-B on plant performance. During almost a whole growing season, canopy gas exchange and Chl fluorescence were measured on Vaccinium uliginosum (bog blueberry). Leaf area, biomass, carbon, nitrogen and UV-B-absorbing compounds were determined from a late season harvest. Compared with the reduced UV-B treatment, the plants in ambient UV-B were found to have a higher content of UV-B-absorbing compounds, and canopy net photosynthesis was as an average 23% lower during the season. By means of the JIP-test, it was found that the potential of processing light energy through the photosynthetic machinery was slightly reduced in ambient UV-B. This indicates that not only the UV-B effects on PSII may be responsible for some of the observed reduction of photosynthesis but also the effects on other parts of the photosynthetic machinery, e.g. the Calvin cycle, might be important. The 60% reduction of the UV-B irradiance used in this study implies a higher relative change in the UV-B load than many of the supplemental experiments do, but the substantial effect on photosynthesis clearly indicates that V. uliginosum is negatively affected by the current level of UV-B. (au)

  2. Ambient UV-B radiation decreases photosynthesis in high arctic Vaccinium uliginosum.

    Science.gov (United States)

    Albert, Kristian R; Mikkelsen, Teis N; Ro-Poulsen, Helge

    2008-06-01

    An UV-B-exclusion experiment was established in high arctic Zackenberg, Northeast Greenland, to investigate the possible effects of ambient UV-B on plant performance. During almost a whole growing season, canopy gas exchange and Chl fluorescence were measured on Vaccinium uliginosum (bog blueberry). Leaf area, biomass, carbon, nitrogen and UV-B-absorbing compounds were determined from a late season harvest. Compared with the reduced UV-B treatment, the plants in ambient UV-B were found to have a higher content of UV-B-absorbing compounds, and canopy net photosynthesis was as an average 23% lower during the season. By means of the JIP-test, it was found that the potential of processing light energy through the photosynthetic machinery was slightly reduced in ambient UV-B. This indicates that not only the UV-B effects on PSII may be responsible for some of the observed reduction of photosynthesis but also the effects on other parts of the photosynthetic machinery, e.g. the Calvin cycle, might be important. The 60% reduction of the UV-B irradiance used in this study implies a higher relative change in the UV-B load than many of the supplemental experiments do, but the substantial effect on photosynthesis clearly indicates that V. uliginosum is negatively affected by the current level of UV-B.

  3. The stage of soil development modulates rhizosphere effect along a High Arctic desert chronosequence.

    Science.gov (United States)

    Mapelli, Francesca; Marasco, Ramona; Fusi, Marco; Scaglia, Barbara; Tsiamis, George; Rolli, Eleonora; Fodelianakis, Stilianos; Bourtzis, Kostas; Ventura, Stefano; Tambone, Fulvia; Adani, Fabrizio; Borin, Sara; Daffonchio, Daniele

    2018-05-01

    In mature soils, plant species and soil type determine the selection of root microbiota. Which of these two factors drives rhizosphere selection in barren substrates of developing desert soils has, however, not yet been established. Chronosequences of glacier forelands provide ideal natural environments to identify primary rhizosphere selection factors along the changing edaphic conditions of a developing soil. Here, we analyze changes in bacterial diversity in bulk soils and rhizospheres of a pioneer plant across a High Arctic glacier chronosequence. We show that the developmental stage of soil strongly modulates rhizosphere community assembly, even though plant-induced selection buffers the effect of changing edaphic factors. Bulk and rhizosphere soils host distinct bacterial communities that differentially vary along the chronosequence. Cation exchange capacity, exchangeable potassium, and metabolite concentration in the soil account for the rhizosphere bacterial diversity. Although the soil fraction (bulk soil and rhizosphere) explains up to 17.2% of the variation in bacterial microbiota, the soil developmental stage explains up to 47.7% of this variation. In addition, the operational taxonomic unit (OTU) co-occurrence network of the rhizosphere, whose complexity increases along the chronosequence, is loosely structured in barren compared with mature soils, corroborating our hypothesis that soil development tunes the rhizosphere effect.

  4. The stage of soil development modulates rhizosphere effect along a High Arctic desert chronosequence

    KAUST Repository

    Mapelli, Francesca

    2018-01-09

    In mature soils, plant species and soil type determine the selection of root microbiota. Which of these two factors drives rhizosphere selection in barren substrates of developing desert soils has, however, not yet been established. Chronosequences of glacier forelands provide ideal natural environments to identify primary rhizosphere selection factors along the changing edaphic conditions of a developing soil. Here, we analyze changes in bacterial diversity in bulk soils and rhizospheres of a pioneer plant across a High Arctic glacier chronosequence. We show that the developmental stage of soil strongly modulates rhizosphere community assembly, even though plant-induced selection buffers the effect of changing edaphic factors. Bulk and rhizosphere soils host distinct bacterial communities that differentially vary along the chronosequence. Cation exchange capacity, exchangeable potassium, and metabolite concentration in the soil account for the rhizosphere bacterial diversity. Although the soil fraction (bulk soil and rhizosphere) explains up to 17.2% of the variation in bacterial microbiota, the soil developmental stage explains up to 47.7% of this variation. In addition, the operational taxonomic unit (OTU) co-occurrence network of the rhizosphere, whose complexity increases along the chronosequence, is loosely structured in barren compared with mature soils, corroborating our hypothesis that soil development tunes the rhizosphere effect.

  5. Winter time burst of CO2 from the High Arctic soils of Svalbard

    DEFF Research Database (Denmark)

    Friborg, Thomas; Hansen, Birger; Elberling, Bo

    of relatively few measurements which appear to give small and constant emission rates. Further, most studies of the processes behind winter time emission of CO2 conclude that the flux during this time of year can be linked to the respiratory release of CO2 from soil micro organisms, which is temperature...... the winter at a high arctic location in Svalbard (78°N). Measurements were conducted in the field during the winter season of 2004-2005 and show reliable and continuous measurements of CO2 fluxes down to a level of 0.01 ìmol m-2 s-1 and good correspondence with other types of soil chambers. Our results...... indicate that a substantial part of the annual CO2 emission from the ecosystem occur during the freeze in period, where more CO2 is emitted from the soil over a few weeks than the accumulated flux for the rest of the winter. During the coldest part of the...

  6. The stage of soil development modulates rhizosphere effect along a High Arctic desert chronosequence

    KAUST Repository

    Mapelli, Francesca; Marasco, Ramona; Fusi, Marco; Scaglia, Barbara; Tsiamis, George; Rolli, Eleonora; Fodelianakis, Stylianos; Bourtzis, Kostas; Ventura, Stefano; Tambone, Fulvia; Adani, Fabrizio; Borin, Sara; Daffonchio, Daniele

    2018-01-01

    In mature soils, plant species and soil type determine the selection of root microbiota. Which of these two factors drives rhizosphere selection in barren substrates of developing desert soils has, however, not yet been established. Chronosequences of glacier forelands provide ideal natural environments to identify primary rhizosphere selection factors along the changing edaphic conditions of a developing soil. Here, we analyze changes in bacterial diversity in bulk soils and rhizospheres of a pioneer plant across a High Arctic glacier chronosequence. We show that the developmental stage of soil strongly modulates rhizosphere community assembly, even though plant-induced selection buffers the effect of changing edaphic factors. Bulk and rhizosphere soils host distinct bacterial communities that differentially vary along the chronosequence. Cation exchange capacity, exchangeable potassium, and metabolite concentration in the soil account for the rhizosphere bacterial diversity. Although the soil fraction (bulk soil and rhizosphere) explains up to 17.2% of the variation in bacterial microbiota, the soil developmental stage explains up to 47.7% of this variation. In addition, the operational taxonomic unit (OTU) co-occurrence network of the rhizosphere, whose complexity increases along the chronosequence, is loosely structured in barren compared with mature soils, corroborating our hypothesis that soil development tunes the rhizosphere effect.

  7. High perveance electron gun for the electron cooling system

    International Nuclear Information System (INIS)

    Korotaev, Yu.; Meshkov, I.; Petrov, A.; Sidorin, A.; Smirnov, A.; Syresin, E.; Titkova, I.

    2000-01-01

    The cooling time in the electron cooling system is inversely proportional to the beam current. To obtain high current of the electron beam the control electrode of the gun is provided with a positive potential and an electrostatic trap for secondary electrons appears inside the electron gun. This leads to a decrease in the gun perveance. To avoid this problem, the adiabatic high perveance electron gun with the clearing control electrode is designed in JINR (J. Bosser, Y. Korotaev, I. Meshkov, E. Syresin et al., Nucl. Instr. and Meth. A 391 (1996) 103. Yu. Korotaev, I. Meshkov, A. Sidorin, A. Smirnov, E. Syresin, The generation of electron beams with perveance of 3-6 μA/V 3/2 , Proceedings of SCHEF'99). The clearing control electrode has a transverse electric field, which clears secondary electrons. Computer simulations of the potential map were made with RELAX3D computer code (C.J. Kost, F.W. Jones, RELAX3D User's Guide and References Manual)

  8. High perveance electron gun for the electron cooling system

    CERN Document Server

    Korotaev, Yu V; Petrov, A; Sidorin, A; Smirnov, A; Syresin, E M; Titkova, I

    2000-01-01

    The cooling time in the electron cooling system is inversely proportional to the beam current. To obtain high current of the electron beam the control electrode of the gun is provided with a positive potential and an electrostatic trap for secondary electrons appears inside the electron gun. This leads to a decrease in the gun perveance. To avoid this problem, the adiabatic high perveance electron gun with the clearing control electrode is designed in JINR (J. Bosser, Y. Korotaev, I. Meshkov, E. Syresin et al., Nucl. Instr. and Meth. A 391 (1996) 103. Yu. Korotaev, I. Meshkov, A. Sidorin, A. Smirnov, E. Syresin, The generation of electron beams with perveance of 3-6 mu A/V sup 3 sup / sup 2 , Proceedings of SCHEF'99). The clearing control electrode has a transverse electric field, which clears secondary electrons. Computer simulations of the potential map were made with RELAX3D computer code (C.J. Kost, F.W. Jones, RELAX3D User's Guide and References Manual).

  9. Plant community composition and species richness in the High Arctic tundra: from the present to the future

    DEFF Research Database (Denmark)

    Nabe-Nielsen, Jacob; Normand, Signe; Hui, Francis K.C.

    2017-01-01

    of these conditions is limited due to the scarcity of studies, especially in the High Arctic. 2. We investigated variations in vascular plant community composition and species richness based on 288 plots distributed on three sites along a coast-inland gradient in Northeast Greenland using a stratified random design......1. Arctic plant communities are altered by climate changes. The magnitude of these alterations depends on whether species distributions are determined by macroclimatic conditions, by factors related to local topography, or by biotic interactions. Our current understanding of the relative importance....... We used an information theoretic approach to determine whether variations in species richness were best explained by macroclimate, by factors related to local topography (including soil water) or by plant-plant interactions. Latent variable models were used to explain patterns in plant community...

  10. Drivers of inter-annual variation and long-term change in High-Arctic spider species abundances

    DEFF Research Database (Denmark)

    Bowden, Joseph J.; Hansen, Oskar L. P.; Olsen, Kent

    2018-01-01

    Understanding how species abundances vary in space and time is a central theme in ecology, yet there are few long-term field studies of terrestrial invertebrate abundances and the determinants of their dynamics. This is particularly relevant in the context of rapid climate change occurring...... in the Arctic. Arthropods can serve as strong indicators of ecosystem change due to their sensitivity to increasing temperatures and other environmental variables. We used spider samples collected by pitfall trapping from three different habitats (fen, mesic and arid heath) in High-Arctic Greenland to assess...... interpretation of long-term trends. We used model selection to determine which climatic variables and/or previous years’ abundance best explained annual variation in species abundances over this period. We identified and used 28 566 adult spiders that comprised eight species. Most notably, the abundances of some...

  11. Diversity and characterization of mercury-resistant bacteria in snow, freshwater and sea-ice brine from the High Arctic

    DEFF Research Database (Denmark)

    Møller, Annette; Barkay, Tamar; Abu Al-Soud, Waleed

    2011-01-01

    It is well-established that atmospheric deposition transports mercury from lower latitudes to the Arctic. The role of bacteria in the dynamics of the deposited mercury, however, is unknown. We characterized mercury-resistant bacteria from High Arctic snow, freshwater and sea-ice brine. Bacterial...... densities were 9.4 × 10(5), 5 × 10(5) and 0.9-3.1 × 10(3) cells mL(-1) in freshwater, brine and snow, respectively. Highest cultivability was observed in snow (11.9%), followed by freshwater (0.3%) and brine (0.03%). In snow, the mercury-resistant bacteria accounted for up to 31% of the culturable bacteria, but...

  12. Atmospheric mercury accumulation between 5900 and 800 calibrated years BP in the high arctic of Canada recorded by Peat Hummocks

    DEFF Research Database (Denmark)

    Givelet, N.; Roos-Barraclough, F.; Goodsite, Michael Evan

    2004-01-01

    In this paper, we present the first comprehensive long-term record of preanthropogenic rates of atmospheric mercury accumulation in dated peat deposits for the High Arctic of Canada. Geochemical studies of two peat hummocks from Bathurst Island, Nunavut reveal substantial inputs from soil dust...... (titanium), marine aerosols (bromine), and mineral-water interactions (uranium). Mercury, however, was supplied to these peat mounds exclusively by atmospheric deposition. Mercury concentration measurements and age dating of the peat profiles indicate rather constant natural "background" mercury flux of ca....... 1 microgram per square meter per year from 5900 to 800 calibrated years BP. These values are well within the range of the mercury fluxes reported from other Arctic locations, but also by peat cores from southern Canada that provide a record of atmospheric Hg accumulation extending back 8000 years...

  13. Seasonal and multi-year surface displacements measured by DInSAR in a High Arctic permafrost environment

    Science.gov (United States)

    Rudy, Ashley C. A.; Lamoureux, Scott F.; Treitz, Paul; Short, Naomi; Brisco, Brian

    2018-02-01

    Arctic landscapes undergo seasonal and long-term changes as the active layer thaws and freezes, which can result in localized or irregular subsidence leading to the formation of thermokarst terrain. Differential Interferometric Synthetic Aperture Radar (DInSAR) is a technique capable of measuring ground surface displacements resulting from thawing permafrost at centimetre precision and is quickly gaining acceptance as a means of measuring ground displacement in permafrost regions. Using RADARSAT-2 stacked DInSAR data from 2013 and 2015 we determined the magnitude and patterns of land surface change in a continuous permafrost environment. At our study site situated in the Canadian High Arctic, DInSAR seasonal ground displacement patterns were consistent with field observations of permafrost degradation. As expected, many DInSAR values are close to the detection threshold (i.e., 1 cm) and therefore do not indicate significant change; however, DInSAR seasonal ground displacement patterns aligned well with climatological and soil conditions and offer geomorphological insight into subsurface processes in permafrost environments. While our dataset is limited to two years of data representing a three-year time period, the displacements derived from DInSAR provide insight into permafrost change in a High Arctic environment and demonstrate that DInSAR is an applicable tool for understanding environmental change in remote permafrost regions.

  14. High temperature electronic gain device

    International Nuclear Information System (INIS)

    McCormick, J.B.; Depp, S.W.; Hamilton, D.J.; Kerwin, W.J.

    1979-01-01

    An integrated thermionic device suitable for use in high temperature, high radiation environments is described. Cathode and control electrodes are deposited on a first substrate facing an anode on a second substrate. The substrates are sealed to a refractory wall and evacuated to form an integrated triode vacuum tube

  15. Long photoperiods sustain high pH in Arctic kelp forests

    DEFF Research Database (Denmark)

    Krause-Jensen, Dorte; Marbà, Núria; Sanz-Martin, M.

    2016-01-01

    Concern on the impacts of ocean acidification on calcifiers, such as bivalves, sea urchins, and foraminifers, has led to efforts to understand the controls on pH in their habitats, which include kelp forests and seagrass meadows. The metabolism of these habitats can lead to diel fluctuation in pH...... with increases during the day and declines at night, suggesting no net effect on pH at time scales longer than daily. We examined the capacity of subarctic and Arctic kelps to up-regulate pH in situ and experimentally tested the role of photoperiod in determining the capacity of Arctic macrophytes to up......-regulate pH. Field observations at photoperiods of 15 and 24 hours in Greenland com- bined with experimental manipulations of photoperiod show that photoperiods longer than 21 hours, characteristic of Arctic summers, are conducive to sustained up-regulation of pH by kelp photosynthesis. We report a gradual...

  16. Intercomparison of atmospheric water vapour measurements at a Canadian High Arctic site

    Science.gov (United States)

    Weaver, Dan; Strong, Kimberly; Schneider, Matthias; Rowe, Penny M.; Sioris, Chris; Walker, Kaley A.; Mariani, Zen; Uttal, Taneil; McElroy, C. Thomas; Vömel, Holger; Spassiani, Alessio; Drummond, James R.

    2017-08-01

    Water vapour is a critical component of the Earth system. Techniques to acquire and improve measurements of atmospheric water vapour and its isotopes are under active development. This work presents a detailed intercomparison of water vapour total column measurements taken between 2006 and 2014 at a Canadian High Arctic research site (Eureka, Nunavut). Instruments include radiosondes, sun photometers, a microwave radiometer, and emission and solar absorption Fourier transform infrared (FTIR) spectrometers. Close agreement is observed between all combination of datasets, with mean differences ≤ 1.0 kg m-2 and correlation coefficients ≥ 0.98. The one exception in the observed high correlation is the comparison between the microwave radiometer and a radiosonde product, which had a correlation coefficient of 0.92.A variety of biases affecting Eureka instruments are revealed and discussed. A subset of Eureka radiosonde measurements was processed by the Global Climate Observing System (GCOS) Reference Upper Air Network (GRUAN) for this study. Comparisons reveal a small dry bias in the standard radiosonde measurement water vapour total columns of approximately 4 %. A recently produced solar absorption FTIR spectrometer dataset resulting from the MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water) retrieval technique is shown to offer accurate measurements of water vapour total columns (e.g. average agreement within -5.2 % of GRUAN and -6.5 % of a co-located emission FTIR spectrometer). However, comparisons show a small wet bias of approximately 6 % at the high-latitude Eureka site. In addition, a new dataset derived from Atmospheric Emitted Radiance Interferometer (AERI) measurements is shown to provide accurate water vapour measurements (e.g. average agreement was within 4 % of GRUAN), which usefully enables measurements to be taken during day and night (especially valuable during polar night).

  17. Low clouds suppress Arctic air formation and amplify high-latitude continental winter warming.

    Science.gov (United States)

    Cronin, Timothy W; Tziperman, Eli

    2015-09-15

    High-latitude continents have warmed much more rapidly in recent decades than the rest of the globe, especially in winter, and the maintenance of warm, frost-free conditions in continental interiors in winter has been a long-standing problem of past equable climates. We use an idealized single-column atmospheric model across a range of conditions to study the polar night process of air mass transformation from high-latitude maritime air, with a prescribed initial temperature profile, to much colder high-latitude continental air. We find that a low-cloud feedback--consisting of a robust increase in the duration of optically thick liquid clouds with warming of the initial state--slows radiative cooling of the surface and amplifies continental warming. This low-cloud feedback increases the continental surface air temperature by roughly two degrees for each degree increase of the initial maritime surface air temperature, effectively suppressing Arctic air formation. The time it takes for the surface air temperature to drop below freezing increases nonlinearly to ∼ 10 d for initial maritime surface air temperatures of 20 °C. These results, supplemented by an analysis of Coupled Model Intercomparison Project phase 5 climate model runs that shows large increases in cloud water path and surface cloud longwave forcing in warmer climates, suggest that the "lapse rate feedback" in simulations of anthropogenic climate change may be related to the influence of low clouds on the stratification of the lower troposphere. The results also indicate that optically thick stratus cloud decks could help to maintain frost-free winter continental interiors in equable climates.

  18. Long photoperiods sustain high pH in Arctic kelp forests.

    Science.gov (United States)

    Krause-Jensen, Dorte; Marbà, Núria; Sanz-Martin, Marina; Hendriks, Iris E; Thyrring, Jakob; Carstensen, Jacob; Sejr, Mikael Kristian; Duarte, Carlos M

    2016-12-01

    Concern on the impacts of ocean acidification on calcifiers, such as bivalves, sea urchins, and foraminifers, has led to efforts to understand the controls on pH in their habitats, which include kelp forests and seagrass meadows. The metabolism of these habitats can lead to diel fluctuation in pH with increases during the day and declines at night, suggesting no net effect on pH at time scales longer than daily. We examined the capacity of subarctic and Arctic kelps to up-regulate pH in situ and experimentally tested the role of photoperiod in determining the capacity of Arctic macrophytes to up-regulate pH. Field observations at photoperiods of 15 and 24 hours in Greenland combined with experimental manipulations of photoperiod show that photoperiods longer than 21 hours, characteristic of Arctic summers, are conducive to sustained up-regulation of pH by kelp photosynthesis. We report a gradual increase in pH of 0.15 units and a parallel decline in pCO 2 of 100 parts per million over a 10-day period in an Arctic kelp forest over midsummer, with ample scope for continued pH increase during the months of continuous daylight. Experimental increase in CO 2 concentration further stimulated the capacity of macrophytes to deplete CO 2 and increase pH. We conclude that long photoperiods in Arctic summers support sustained up-regulation of pH in kelp forests, with potential benefits for calcifiers, and propose that this mechanism may increase with the projected expansion of Arctic vegetation in response to warming and loss of sea ice.

  19. Diversity and characterization of mercury-resistant bacteria in snow, freshwater and sea-ice brine from the High Arctic.

    Science.gov (United States)

    Møller, Annette K; Barkay, Tamar; Abu Al-Soud, Waleed; Sørensen, Søren J; Skov, Henrik; Kroer, Niels

    2011-03-01

    It is well-established that atmospheric deposition transports mercury from lower latitudes to the Arctic. The role of bacteria in the dynamics of the deposited mercury, however, is unknown. We characterized mercury-resistant bacteria from High Arctic snow, freshwater and sea-ice brine. Bacterial densities were 9.4 × 10(5), 5 × 10(5) and 0.9-3.1 × 10(3) cells mL(-1) in freshwater, brine and snow, respectively. Highest cultivability was observed in snow (11.9%), followed by freshwater (0.3%) and brine (0.03%). In snow, the mercury-resistant bacteria accounted for up to 31% of the culturable bacteria, but levels of most isolates were not temperature dependent. Of the resistant isolates, 25% reduced Hg(II) to Hg(0). No relation between resistance level, ability to reduce Hg(II) and phylogenetic group was observed. An estimation of the potential bacterial reduction of Hg(II) in snow suggested that it was important in the deeper snow layers where light attenuation inhibited photoreduction. Thus, by reducing Hg(II) to Hg(0), mercury-resistant bacteria may limit the supply of substrate for methylation processes and, hence, contribute to lowering the risk that methylmercury is being incorporated into the Arctic food chains. © 2010 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

  20. Trends in historical mercury deposition inferred from lake sediment cores across a climate gradient in the Canadian High Arctic.

    Science.gov (United States)

    Korosi, Jennifer B; Griffiths, Katherine; Smol, John P; Blais, Jules M

    2018-06-02

    Recent climate change may be enhancing mercury fluxes to Arctic lake sediments, confounding the use of sediment cores to reconstruct histories of atmospheric deposition. Assessing the independent effects of climate warming on mercury sequestration is challenging due to temporal overlap between warming temperatures and increased long-range transport of atmospheric mercury following the Industrial Revolution. We address this challenge by examining mercury trends in short cores (the last several hundred years) from eight lakes centered on Cape Herschel (Canadian High Arctic) that span a gradient in microclimates, including two lakes that have not yet been significantly altered by climate warming due to continued ice cover. Previous research on subfossil diatoms and inferred primary production indicated the timing of limnological responses to climate warming, which, due to prevailing ice cover conditions, varied from ∼1850 to ∼1990 for lakes that have undergone changes. We show that climate warming may have enhanced mercury deposition to lake sediments in one lake (Moraine Pond), while another (West Lake) showed a strong signal of post-industrial mercury enrichment without any corresponding limnological changes associated with warming. Our results provide insights into the role of climate warming and organic carbon cycling as drivers of mercury deposition to Arctic lake sediments. Copyright © 2018 Elsevier Ltd. All rights reserved.

  1. High Arctic Forests During the Middle Eocene Supported by ~400 ppm Atmospheric CO2

    Science.gov (United States)

    Maxbauer, D. P.; Royer, D. L.; LePage, B. A.

    2013-12-01

    Fossils from Paleogene High Arctic deposits provide some of the clearest evidence for greenhouse climates and offer the potential to improve our understanding of Earth system dynamics in a largely ice-free world. One of the most well-known and exquisitely-preserved middle Eocene (47.9-37.8 Myrs ago) polar forest sites, Napartulik, crops out on eastern Axel Heiberg Island (80 °N), Nunavut, Canada. An abundance of data from Napartulik suggest mean annual temperatures of up to 30 °C warmer than today and atmospheric water loads 2× above current levels. Despite this wealth of paleontological and paleoclimatological data, there are currently no direct constraints on atmospheric CO2 levels for Napartulik or any other polar forest site. Here we apply a new plant gas-exchange model to Metasequoia (dawn redwood) leaves to reconstruct atmospheric CO2 from six fossil forests at Napartulik. Individual reconstructions vary between 405-489 ppm with a site mean of 437 ppm (337-564 ppm at 95% confidence). These estimates represent the first direct constraints on CO2 for polar fossil forests and suggest that the temperate conditions present at Napartulik during the middle Eocene were maintained under CO2 concentrations ~1.6× above pre-industrial levels. Our results strongly support the case that long-term climate sensitivity to CO2 in the past was sometimes high, even during largely ice-free periods, highlighting the need to better understand the climate forcing and feedback mechanisms responsible for this amplification.

  2. Toward Improved Estimation of the Dynamic Topography and Ocean Circulation in the High Latitude and Arctic Ocean: The Importance of GOCE

    DEFF Research Database (Denmark)

    Johannessen, J. A.; Raj, R. P.; Nilsen, J. E. Ø.

    2014-01-01

    The Arctic plays a fundamental role in the climate system and shows significant sensitivity to anthropogenic climate forcing and the ongoing climate change. Accelerated changes in the Arctic are already observed, including elevated air and ocean temperatures, declines of the summer sea ice extent...... quantify this. Moreover, changes in the temperature and salinity of surface waters in the Arctic Ocean and Nordic Seas may also influence the flow of dense water through the Denmark Strait, which are found to be a precursor for changes in the Atlantic meridional overturning circulation with a lead time...... circulation and transport variability in the high latitude and Arctic Ocean. In this respect, this study combines in situ hydrographical data, surface drifter data and direct current meter measurements, with coupled sea ice–ocean models, radar altimeter data and the latest GOCE-based geoid in order...

  3. Glacier inputs influence organic matter composition and prokaryotic distribution in a high Arctic fjord (Kongsfjorden, Svalbard)

    KAUST Repository

    Bourgeois, Solveig

    2016-08-23

    With climate change, the strong seasonality and tight pelagic-benthic coupling in the Arctic is expected to change in the next few decades. It is currently unclear how the benthos will be affected by changes of environmental conditions such as supplies of organic matter (OM) from the water column. In the last decade, Kongsfjorden (79°N), a high Arctic fjord in Svalbard influenced by several glaciers and Atlantic water inflow, has been a site of great interest owing to its high sensitivity to climate change, evidenced by a reduction in ice cover and an increase in melting freshwater. To investigate how spatial and seasonal changes in vertical fluxes can impact the benthic compartment of Kongsfjorden, we studied the organic matter characteristics (in terms of quantity and quality) and prokaryotic distribution in sediments from 3 stations along a transect extending from the glacier into the outer fjord in 4 different seasons (spring, summer, autumn and winter) in 2012–2013. The biochemical parameters used to describe the sedimentary organic matter were organic carbon (OC), total nitrogen, bulk stable isotope ratios, pigments (chorophyll-a and phaeopigments) and biopolymeric carbon (BPC), which is the sum of the main macromolecules, i.e. lipids, proteins and carbohydrates. Prokaryotic abundance and distribution were estimated by 4′,6-diamidino-2-phenylindole (DAPI) staining. This study identifies a well-marked quantitative gradient of biogenic compounds throughout all seasons and also highlights a discrepancy between the quantity and quality of sedimentary organic matter within the fjord. The sediments near the glacier were organic-poor (< 0.3%OC), however the high primary productivity in the water column displayed during spring was reflected in summer sediments, and exhibited higher freshness of material at the inner station compared to the outer basin (means C-chlorophyll-a/OC ~ 5 and 1.5%, respectively). However, sediments at the glacier front were depleted

  4. High energy electron positron physics

    International Nuclear Information System (INIS)

    Ali, A.; Soding, P.

    1987-01-01

    With the termination of the physics program at PETRA in a year from now, and with the start of TRISTAN and the SLC and later LEP, an era of e/sup +/e/sup -/ physics will come to an end and a new one begins. The field is changing from a field of a few specialists, to becoming one of the mainstream efforts of the high energy community. It seems appropriate at this moment to summarize what has been learned over the past years, in a way more useful to any high energy physicist in particular to newcomers in the e/sup +/e/sup -/ field. This is the purpose of the book. This book should be used as a reference for future workers in the field of e/sup +/e/sup -/ interactions. It includes the most relevant data, parametrizations, theoretical background, and a chapter on detectors. Contents: Foreword; Detectors for High Energy e/sup +/e/sup -/ Physics; Lepton Pair Production and Electroweak Parameters; Hadron Production, Strong and Electroweak Properties; tau Physics; Recent Results on the Charm Sector; Bottom Physics; Lifetime Measurements of tau, Charmed and Beauty Hadrons; Υ Spectroscopy; Hadronic Decays of the Υ; Quark and Gluon Fragmentation in the e/sup +/e/sup -/ Continuum; Jet Production and QCD; Two Photon Physics; Search for New Particles

  5. High energy electron multibeam diffraction and imaging

    International Nuclear Information System (INIS)

    Bourret, Alain.

    1980-04-01

    The different theories of dynamical scattering of electrons are firstly reviewed with special reference to their basis and the validity of the different approximations. Then after a short description of the different experimental set ups, structural analysis and the investigation of the optical potential by means of high energy electrons will be surveyed

  6. Organic carbon transformations in high-Arctic peat soils: key functions and microorganisms.

    Science.gov (United States)

    Tveit, Alexander; Schwacke, Rainer; Svenning, Mette M; Urich, Tim

    2013-02-01

    A substantial part of the Earths' soil organic carbon (SOC) is stored in Arctic permafrost peatlands, which represent large potential sources for increased emissions of the greenhouse gases CH(4) and CO(2) in a warming climate. The microbial communities and their genetic repertoire involved in the breakdown and mineralisation of SOC in these soils are, however, poorly understood. In this study, we applied a combined metagenomic and metatranscriptomic approach on two Arctic peat soils to investigate the identity and the gene pool of the microbiota driving the SOC degradation in the seasonally thawed active layers. A large and diverse set of genes encoding plant polymer-degrading enzymes was found, comparable to microbiotas from temperate and subtropical soils. This indicates that the metabolic potential for SOC degradation in Arctic peat is not different from that of other climatic zones. The majority of these genes were assigned to three bacterial phyla, Actinobacteria, Verrucomicrobia and Bacteroidetes. Anaerobic metabolic pathways and the fraction of methanogenic archaea increased with peat depth, evident for a gradual transition from aerobic to anaerobic lifestyles. A population of CH(4)-oxidising bacteria closely related to Methylobacter tundripaludum was the dominating active group of methanotrophs. Based on the in-depth characterisation of the microbes and their genes, we conclude that these Arctic peat soils will turn into CO(2) sources owing to increased active layer depth and prolonged growing season. However, the extent of future CH(4) emissions will critically depend on the response of the methanotrophic bacteria.

  7. High variability of atmospheric mercury in the summertime boundary layer through the central Arctic Ocean.

    Science.gov (United States)

    Yu, Juan; Xie, Zhouqing; Kang, Hui; Li, Zheng; Sun, Chen; Bian, Lingen; Zhang, Pengfei

    2014-08-15

    The biogeochemical cycles of mercury in the Arctic springtime have been intensively investigated due to mercury being rapidly removed from the atmosphere. However, the behavior of mercury in the Arctic summertime is still poorly understood. Here we report the characteristics of total gaseous mercury (TGM) concentrations through the central Arctic Ocean from July to September, 2012. The TGM concentrations varied considerably (from 0.15 ng/m(3) to 4.58 ng/m(3)), and displayed a normal distribution with an average of 1.23 ± 0.61 ng/m(3). The highest frequency range was 1.0-1.5 ng/m(3), lower than previously reported background values in the Northern Hemisphere. Inhomogeneous distributions were observed over the Arctic Ocean due to the effect of sea ice melt and/or runoff. A lower level of TGM was found in July than in September, potentially because ocean emission was outweighed by chemical loss.

  8. Elevated levels of ingested plastic in a high Arctic seabird, the northern fulmar (Fulmarus glacialis)

    NARCIS (Netherlands)

    Trevail, A.M.; Gabrielsen, G.W.; Kuhn, S.; Franeker, van J.A.

    2015-01-01

    Plastic pollution is of worldwide concern; however, increases in international commercial activity in the Arctic are occurring without the knowledge of the existing threat posed to the local marine environment by plastic litter. Here, we quantify plastic ingestion by northern fulmars, Fulmarus

  9. High basal metabolic rates in shorebirds while in the Arctic: a circumpolar view

    NARCIS (Netherlands)

    Lindström, A.; Klaassen, M.R.J.

    2003-01-01

    The basal metabolic rate (BMR) of Old World long-distance-migrant shorebirds has been found to vary along their migration route. On average, BMR is highest in the Arctic at the start of fall migration, intermediate at temperate latitudes, and lowest on the tropical wintering grounds. As a test of

  10. Carbon bioavailability in a high Arctic fjord influenced by glacial meltwater, NE Greenland

    DEFF Research Database (Denmark)

    Paulsen, Maria Lund; Nielsen, Sophia Elisabeth Bardram; Müller, Jens-Oliver

    2017-01-01

    The land-to-ocean flux of organic carbon is increasing in glacierized regions in response to increasing temperatures in the Arctic (Hood et al., 2015). In order to understand the response of the coastal ecosystem metabolism to the organic carbon input it is essential to determine the bioavailabil...

  11. Plant functional type affects nitrogen use efficiency in high-Arctic tundra

    Czech Academy of Sciences Publication Activity Database

    Oulehle, F.; Rowe, E. C.; Myška, Oldřich; Chuman, T.; Evans, C.D.

    2016-01-01

    Roč. 94, mar (2016), s. 19-28 ISSN 0038-0717 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0073 Institutional support: RVO:67179843 Keywords : Arctic * Nitrogen * Isotope * Mineralization * Nitrification * Tundra Subject RIV: EH - Ecology, Behaviour Impact factor: 4.857, year: 2016

  12. Surface morphology of fans in the high-Arctic periglacial environment of Svalbard : Controls and processes

    NARCIS (Netherlands)

    De Haas, Tjalling|info:eu-repo/dai/nl/374023190; Kleinhans, Maarten G.|info:eu-repo/dai/nl/217675123; Carbonneau, Patrice E.; Rubensdotter, Lena; Hauber, Ernst

    2015-01-01

    Fan-shaped landforms occur in all climatic regions on Earth. They have been extensively studied in many of these regions, but there are few studies on fans in periglacial, Arctic and Antarctic regions. Fans in such regions are exposed to many site-specific environmental conditions in addition to

  13. Pacific centre of the Arctic Oscillation: product of high local variability rather than teleconnectivity

    Czech Academy of Sciences Publication Activity Database

    Huth, Radan

    58A, č. 5 (2006), s. 601-604 ISSN 0280-6495 R&D Projects: GA ČR GA205/05/2282 Institutional research plan: CEZ:AV0Z30420517 Keywords : Arctic Oscillation * Pacific centre * principal component analysis Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 2.245, year: 2006

  14. High-efficient electron linacs

    International Nuclear Information System (INIS)

    Glavatskikh, K.V.; Zverev, B.V.; Kalyuzhnyj, V.E.; Morozov, V.L.; Nikolaev, S.V.; Plotnikov, S.N.; Sobenin, N.P.; Vovna, V.A.; Gryzlov, A.V.

    1993-01-01

    Comparison analysis of ELA on running and still waves designed for 10 MeV energy and with high efficiency is carried out. It is shown, that from the point of view of dimensions ELA with a still wave or that of a combined type is more preferable. From the point of view of impedance characteristics in any variant with application of magnetron as HF-generator it is necessary to implement special requirements to the accelerating structure if no ferrite isolation is provided in HF-channel. 3 refs., 4 figs., 1 tab

  15. Origin of middle rare earth element enrichments in acid waters of a Canadian high Arctic lake.

    Science.gov (United States)

    Johannesson, Kevin H.; Zhou, Xiaoping

    1999-01-01

    -Middle rare earth element (MREE) enriched rock-normalized rare earth element (REE) patterns of a dilute acidic lake (Colour Lake) in the Canadian High Arctic, were investigated by quantifying whole-rock REE concentrations of rock samples collected from the catchment basin, as well as determining the acid leachable REE fraction of these rocks. An aliquot of each rock sample was leached with 1 N HNO 3 to examine the readily leachable REE fraction of each rock, and an additional aliquot was leached with a 0.04 M NH 2OH · HCl in 25% (v/v) CH 3COOH solution, designed specifically to reduce Fe-Mn oxides/oxyhydroxides. Rare earth elements associated with the leachates that reacted with clastic sedimentary rock samples containing petrographically identifiable Fe-Mn oxide/oxyhydroxide cements and/or minerals/amorphous phases, exhibited whole-rock-normalized REE patterns similar to the lake waters, whereas whole-rock-normalized leachates from mafic igneous rocks and other clastic sedimentary rocks from the catchment basin differed substantially from the lake waters. The whole-rock, leachates, and lake water REE data support acid leaching or dissolution of MREE enriched Fe-Mn oxides/oxyhydroxides contained and identified within some of the catchment basin sedimentary rocks as the likely source of the unique lake water REE patterns. Solution complexation modelling of the REEs in the inflow streams and lake waters indicate that free metal ions (e.g., Ln 3+, where Ln = any REE) and sulfate complexes (LnSO 4+) are the dominant forms of dissolved REEs. Consequently, solution complexation reactions involving the REEs during weathering, transport to the lake, or within the lake, cannot be invoked to explain the MREE enrichments observed in the lake waters.

  16. The development of membrane based high purity oily water separators for use in Arctic waters

    Energy Technology Data Exchange (ETDEWEB)

    Peng, H.; Tremblay, A.Y. [Ottawa Univ., ON (Canada). Dept. of Chemical Engineering, Industrial Membrane Centre; Veinot, D.E. [Defence Research and Development Canada, Halifax, NS (Canada)

    2005-07-01

    With increased exploration and industrial activity in the Canadian Arctic, interest in the Northwest Passage as a shipping route has also increased. The oily wastewater produced by ships must be treated prior to discharge, particularly in the sensitive Arctic environment where biodegradation of organics is very slow due to cold climatic conditions and low sunlight. As such, safe techniques are needed for the treatment of oily wastewater released from ships. However, bilge water is difficult to treat because it contains seawater, particulates, used oils and detergents. Membrane based oily water separators (OWS) are considered to be a key technology for the treatment of bilge water onboard ships. The issues that must be taken into account in the ship-born use of membrane based OWS include the proper treatment of the oily brine before discharge; the substantial reduction in volume that is required; the complexity of the technology; labour associated with the operation of the system due to filter changes and cleaning; and, system automation to simplify its operation. In this study, a membrane-based process for treating bilge water was developed to meet stringent discharge regulations for discharge in Arctic waters. Currently, this discharge limit is set at 0 ppm. A pilot scale membrane cascade system was designed and evaluated. Multilumen ceramic membranes were used in the first stage and Sepa{sup R} test cells were used in the second stage. Optimal membrane pore size was determined. The study investigated the separation of oil and grease using different molecular weight cut-off (MWCO) membranes. The study revealed that through proper membrane design, it is possible to remove oil and grease from bilge water to a level permitting its discharge to Arctic waters. However, it was recommended that low level aromatic diesel fuels be used in ships operating in Arctic waters since the presence of soluble aromatics in diesel fuel increases the technical difficulty of reaching

  17. High colored dissolved organic matter (CDOM) absorption in surface waters of the central-eastern Arctic Ocean: Implications for biogeochemistry and ocean color algorithms.

    Science.gov (United States)

    Gonçalves-Araujo, Rafael; Rabe, Benjamin; Peeken, Ilka; Bracher, Astrid

    2018-01-01

    As consequences of global warming sea-ice shrinking, permafrost thawing and changes in fresh water and terrestrial material export have already been reported in the Arctic environment. These processes impact light penetration and primary production. To reach a better understanding of the current status and to provide accurate forecasts Arctic biogeochemical and physical parameters need to be extensively monitored. In this sense, bio-optical properties are useful to be measured due to the applicability of optical instrumentation to autonomous platforms, including satellites. This study characterizes the non-water absorbers and their coupling to hydrographic conditions in the poorly sampled surface waters of the central and eastern Arctic Ocean. Over the entire sampled area colored dissolved organic matter (CDOM) dominates the light absorption in surface waters. The distribution of CDOM, phytoplankton and non-algal particles absorption reproduces the hydrographic variability in this region of the Arctic Ocean which suggests a subdivision into five major bio-optical provinces: Laptev Sea Shelf, Laptev Sea, Central Arctic/Transpolar Drift, Beaufort Gyre and Eurasian/Nansen Basin. Evaluating ocean color algorithms commonly applied in the Arctic Ocean shows that global and regionally tuned empirical algorithms provide poor chlorophyll-a (Chl-a) estimates. The semi-analytical algorithms Generalized Inherent Optical Property model (GIOP) and Garver-Siegel-Maritorena (GSM), on the other hand, provide robust estimates of Chl-a and absorption of colored matter. Applying GSM with modifications proposed for the western Arctic Ocean produced reliable information on the absorption by colored matter, and specifically by CDOM. These findings highlight that only semi-analytical ocean color algorithms are able to identify with low uncertainty the distribution of the different optical water constituents in these high CDOM absorbing waters. In addition, a clustering of the Arctic Ocean

  18. Arctic Security

    DEFF Research Database (Denmark)

    Wang, Nils

    2013-01-01

    The inclusion of China, India, Japan, Singapore and Italy as permanent observers in the Arctic Council has increased the international status of this forum significantly. This chapter aims to explain the background for the increased international interest in the Arctic region through an analysis...

  19. Biogeochemical Indicators in High- and Low-Arctic Marine and Terrestrial Avian Community Changes: Comparative Isotopic (13C, 15N, and 34S) Studies in Alaska and Greenland

    Science.gov (United States)

    Causey, D.; Bargmann, N. A.; Burnham, K. K.; Burnham, J. L.; Padula, V. M.; Johnson, J. A.; Welker, J. M.

    2011-12-01

    Understanding the complex dynamics of environmental change in northern latitudes is of paramount importance today, given documented rapid shifts in sea ice, plant phenology, temperatures, deglaciation, and habitat fidelity. This knowledge is particularly critical for Arctic avian communities, which are integral components by which biological teleconnections are maintained between the mid and northern latitudes. Furthermore, Arctic birds are fundamental to Native subsistence lifestyles and a focus for conservation activities. Avian communities of marine and terrestrial Arctic environments represent a broad spectrum of trophic levels, from herbivores (eg., geese Chen spp.), planktivores (eg., auklets Aethia spp.), and insectivores (eg., passerines: Wheatears Oenanthe spp., Longspurs Calcarius spp.), to predators of marine invertebrates (eg., eiders Somateria spp.), nearshore and offshore fish (eg., cormorants Phalacrocorax spp, puffins Fratercula spp.), even other bird species (eg., gulls Larus spp., falcons Peregrinus spp.). This diversity of trophic interconnections is an integral factor in the dynamics of Arctic ecosystem ecology, and they are key indicators for the strength and trajectories of change. We are especially interested in their feeding ecology, using stable isotope-diet relations to examine historical diets and to predict future feeding ecology by this range of species. Since 2009, we have been studying the foodweb ecology using stable isotopes (δ13C, δ15N, δ34S) of contemporaneous coastal and marine bird communities in High Arctic (Northwest Greenland) and Low Arctic (western Aleutian Islands, AK). We are quantifying the isotopic values of blood, organ tissues, and feathers, and have carried out comparisons between native and lipid-extracted samples. Although geographically distant, these communities comprise similar taxonomic and ecological congeners, including several species common to both (eg., Common Eider, Black-legged Kittiwake, Northern

  20. Brominated flame retardants in aquatic organisms from the North Sea in comparison with biota from the high Arctic marine environment.

    Science.gov (United States)

    Sørmo, Eugen G; Jenssen, Bjørn M; Lie, Elisabeth; Skaare, Janneche U

    2009-10-01

    The extent of trophic transfer of brominated flame retardants (BFRs), including hexabromocyclododecane (HBCD) and seven polybrominated diphenyl ethers (PBDEs), were examined in pelagic and benthic aquatic animals (invertebrates and fish) in a near-shore estuary environment of the southeastern North Sea (Norway; 59 degrees N). Whole-body burdens of HBCD and several of the most abundant PBDEs biomagnified with increasing trophic position in the food web. Biomagnification of HBCD was particularly strong, resulting in whole-body burdens of this compound comparable to those of total PBDEs in the higher-trophic-level species. Body burdens of PBDEs were higher in pelagic than in benthic aquatic organisms. This was particularly evident for the lesser-brominated and volatile PBDE congeners. Atmospheric gas-water-phytoplankton exchange of these volatile compounds over the water surface may account for this observation. The PBDE burdens in pelagic zooplankton from the North Sea were more than 60-fold greater than those in corresponding pelagic zooplankton from the colder high Arctic latitudes (>78 degrees N) of Norway (Svalbard). This great difference may relate to reduced chemical gas-water exchange over open waters at the colder Arctic latitudes. However, previously measured whole-body burdens of BFRs in other aquatic marine organisms from the high Arctic were comparable or even exceeded those in the North Sea samples of the present study. These include sympagic (sea ice-associated) invertebrates and fish accumulating high burdens of particle-associated BFRs. The present study provides new insight regarding the distribution of BFRs in ecologically different compartments of marine ecosystems, essential information for understanding the food-web transfer and geographical dispersal of these compounds.

  1. Levoglucosan indicates high levels of biomass burning aerosols over oceans from the Arctic to Antarctic.

    Science.gov (United States)

    Hu, Qi-Hou; Xie, Zhou-Qing; Wang, Xin-Ming; Kang, Hui; Zhang, Pengfei

    2013-11-01

    Biomass burning is known to affect air quality, global carbon cycle, and climate. However, the extent to which biomass burning gases/aerosols are present on a global scale, especially in the marine atmosphere, is poorly understood. Here we report the molecular tracer levoglucosan concentrations in marine air from the Arctic Ocean through the North and South Pacific Ocean to Antarctica during burning season. Levoglucosan was found to be present in all regions at ng/m(3) levels with the highest atmospheric loadings present in the mid-latitudes (30°-60° N and S), intermediate loadings in the Arctic, and lowest loadings in the Antarctic and equatorial latitudes. As a whole, levoglucosan concentrations in the Southern Hemisphere were comparable to those in the Northern Hemisphere. Biomass burning has a significant impact on atmospheric Hg and water-soluble organic carbon (WSOC) from pole-to-pole, with more contribution to WSOC in the Northern Hemisphere than in the Southern Hemisphere.

  2. Cold season soil respiration in response to grazing and warming in the High Arctic Svalbard

    DEFF Research Database (Denmark)

    Strebel, Ditte; Elberling, Bo; Morgner, Elke

    2010-01-01

    of Arctic Goose Habitat: Impacts of Land Use, Conservation and Elevated Temperatures). New measurements of soil CO2 effluxes, temperatures and water contents were regularly made from July to November 2007. SOC stocks were quantified, and the reactivity and composition measured by basal soil respiration (BSR...... be concluded that two years after a goose grazing experiment, SOC cycling was less than the natural variation within contrasting vegetation types....

  3. Molecular analyses reveal high species diversity of trematodes in a sub-Arctic lake

    Czech Academy of Sciences Publication Activity Database

    Soldánová, Miroslava; Georgieva, Simona; Roháčová, Jana; Knudsen, R.; Kuhn, J. A.; Henriksen, E. H.; Siwertsson, A.; Shaw, J. C.; Kuris, A. M.; Amundsen, P.-A.; Scholz, Tomáš; Lafferty, K. D.; Kostadinova, Aneta

    2017-01-01

    Roč. 47, č. 6 (2017), s. 327-345 ISSN 0020-7519 R&D Projects: GA ČR GA15-14198S; GA ČR GAP505/10/1562 Institutional support: RVO:60077344 Keywords : Trematode diversity * intermediate hosts * phylogeny * mitochondrial DNA * nuclear DNA * Lake Takvatn * Norway * Sub-Arctic Subject RIV: EG - Zoology OBOR OECD: Zoology Impact factor: 3.730, year: 2016

  4. Deep Trek High Temperature Electronics Project

    Energy Technology Data Exchange (ETDEWEB)

    Bruce Ohme

    2007-07-31

    This report summarizes technical progress achieved during the cooperative research agreement between Honeywell and U.S. Department of Energy to develop high-temperature electronics. Objects of this development included Silicon-on-Insulator (SOI) wafer process development for high temperature, supporting design tools and libraries, and high temperature integrated circuit component development including FPGA, EEPROM, high-resolution A-to-D converter, and a precision amplifier.

  5. Compact high-current, subnanosecond electron accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Shpak, V G; Shunajlov, S A; Ulmaskulov, M R; Yalandin, M I [Russian Academy of Sciences, Ekaterinburg (Russian Federation). Inst. of Electrophysics; Pegel, I V [Russian Academy of Sciences, Tomsk (Russian Federation). High-Current Electronics Inst.; Tarakanov, V P [Russian Academy of Sciences, Moscow (Russian Federation). High-Temperature Inst.

    1997-12-31

    A compact subnanosecond, high-current electron accelerator producing an annular electron beam of duration up to 300 - 400 ps, energy about 250 keV, and current up to 1 kA has been developed to study transient processes in pulsed power microwave devices. The measuring and recording techniques used to experimentally investigate the dynamics of the beam current pulse and the transformation of the electron energy during the transportation of the beam in a longitudinal magnetic field are described. The experimental data obtained are compared with the predictions of a numerical simulation. (author). 6 figs., 5 refs.

  6. Atmospheric concentrations of halogenated flame retardants at two remote locations: The Canadian High Arctic and the Tibetan Plateau

    International Nuclear Information System (INIS)

    Xiao Hang; Shen Li; Su, Yushan; Barresi, Enzo; DeJong, Maryl; Hung, Hayley; Lei, Ying-Duan; Wania, Frank; Reiner, Eric J.; Sverko, Ed; Kang, Shi-Chang

    2012-01-01

    Atmospheric concentrations of halogenated flame retardants (FRs) were monitored for approximately one year at two remote stations, namely Nam Co on the Tibetan Plateau and Alert in the Canadian High Arctic. BDE-47 and 99 were the dominant polybrominated diphenyl ether (PBDE) congeners at both sites. Atmospheric PBDE concentrations in Nam Co were generally lower than those at Alert. While significant seasonal variations were observed for PBDEs at Alert, the FR concentrations at Nam Co showed no significant seasonality, even though air masses originated from distinctly different regions during different seasons. This suggests that FRs in Tibet do not have regional sources, but are reflective of truly global background contamination. Three new FRs, namely 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), 2-ethyl-1-hexyl-2,3,4,5-tetrabromobenzoate (EHTeBB) and bis(2-ethyl-1-hexyl)tetrabromophthalate (TBPH) were detected at relatively high concentrations at both sites. This is the first report of these FRs in the remote global atmosphere and suggests significant potential for long-range atmospheric transport. - Highlights: ► First year-round measurements of FRs in the atmosphere of the Tibetan Plateau. ► PBDEs in Tibet are reflective of truly global background levels. ► Orographic precipitation limits the transport of particle-bound chemicals. ► First study of BTBPE, EHTeBB and TBPH in the Arctic and Tibetan air. ► These new FRs may have significant long-range atmospheric transport potential. - Several brominated flame retardants (BTBPE, EHTeBB, TBPH) were present in the atmosphere of the Arctic and the Tibetan Plateau at levels similar to those of the PBDEs.

  7. Annual CO2 budget and seasonal CO2 exchange signals at a High Arctic permafrost site on Spitsbergen, Svalbard archipelago

    Science.gov (United States)

    Lüers, J.; Westermann, S.; Piel, K.; Boike, J.

    2014-01-01

    The annual variability of CO2 exchange in most ecosystems is primarily driven by the activities of plants and soil microorganisms. However, little is known about the carbon balance and its controlling factors outside the growing season in arctic regions dominated by soil freeze/thaw-processes, long-lasting snow cover, and several months of darkness. This study presents a complete annual cycle of the CO2 net ecosystem exchange (NEE) dynamics for a High Arctic tundra area on the west coast of Svalbard based on eddy-covariance flux measurements. The annual cumulative CO2 budget is close to zero grams carbon per square meter per year, but shows a very strong seasonal variability. Four major CO2 exchange seasons have been identified. (1) During summer (ground snow-free), the CO2 exchange occurs mainly as a result of biological activity, with a predominance of strong CO2 assimilation by the ecosystem. (2) The autumn (ground snow-free or partly snow-covered) is dominated by CO2 respiration as a result of biological activity. (3) In winter and spring (ground snow-covered), low but persistent CO2 release occur, overlain by considerable CO2 exchange events in both directions associated with changes of air masses and air and atmospheric CO2 pressure. (4) The snow melt season (pattern of snow-free and snow-covered areas), where both, meteorological and biological forcing, resulting in a visible carbon uptake by the high arctic ecosystem. Data related to this article are archived under: http://doi.pangaea.de/10.1594/PANGAEA.809507.

  8. Carbon and hydrogen isotope fractionation under continuous light: implications for paleoenvironmental interpretations of the High Arctic during Paleogene warming.

    Science.gov (United States)

    Yang, Hong; Pagani, Mark; Briggs, Derek E G; Equiza, M A; Jagels, Richard; Leng, Qin; Lepage, Ben A

    2009-06-01

    The effect of low intensity continuous light, e.g., in the High Arctic summer, on plant carbon and hydrogen isotope fractionations is unknown. We conducted greenhouse experiments to test the impact of light quantity and duration on both carbon and hydrogen isotope compositions of three deciduous conifers whose fossil counterparts were components of Paleogene Arctic floras: Metasequoia glyptostroboides, Taxodium distichum, and Larix laricina. We found that plant leaf bulk carbon isotopic values of the examined species were 1.75-4.63 per thousand more negative under continuous light (CL) than under diurnal light (DL). Hydrogen isotope values of leaf n-alkanes under continuous light conditions revealed a D-enriched hydrogen isotope composition of up to 40 per thousand higher than in diurnal light conditions. The isotope offsets between the two light regimes is explained by a higher ratio of intercellular to atmospheric CO(2) concentration (C (i)/C (a)) and more water loss for plants under continuous light conditions during a 24-h transpiration cycle. Apparent hydrogen isotope fractionations between source water and individual lipids (epsilon(lipid-water)) range from -62 per thousand (Metasequoia C(27) and C(29)) to -87 per thousand (Larix C(29)) in leaves under continuous light. We applied these hydrogen fractionation factors to hydrogen isotope compositions of in situ n-alkanes from well-preserved Paleogene deciduous conifer fossils from the Arctic region to estimate the deltaD value in ancient precipitation. Precipitation in the summer growing season yielded a deltaD of -186 per thousand for late Paleocene, -157 per thousand for early middle Eocene, and -182 per thousand for late middle Eocene. We propose that high-latitude summer precipitation in this region was supplemented by moisture derived from regionally recycled transpiration of the polar forests that grew during the Paleogene warming.

  9. Responses of CO2 Fluxes to Arctic Browning Events in a Range of High Latitude, Shrub-Dominated Ecosystems

    Science.gov (United States)

    Phoenix, G. K.; Treharne, R.; Emberson, L.; Tømmervik, H. A.; Bjerke, J. W.

    2017-12-01

    Climatic and biotic extreme events can result in considerable damage to arctic vegetation, often at landscape and larger scale. These acute events therefore contribute to the browning observed in some arctic regions. It is of considerable concern, therefore, that such extreme events are increasing in frequency as part of climate change. However, despite the increasing importance of browning events, and the considerable impact they can have on ecosystems, to date there is little understanding of their impacts on ecosystem carbon fluxes. To address this, the impacts of a number of different, commonly occurring, extreme events and their subsequent browning (vegetation damage) on key ecosystem CO2 fluxes were assessed during the growing season at a range of event damaged sites of shrub dominated vegetation. Sites were located from the boreal to High Arctic (64˚N-79˚N) and had been previously been damaged by events of frost-drought, extreme winter warming, ground icing and caterpillar (Epirrita autumnata) outbreaks. Plot-level CO2 fluxes of Ecosystem Exchange (NEE), Gross Primary Productivity (GPP) and Ecosystem Respiration (Reco) were assessed using vegetation chambers. At a sub-set of sites, NDVI (greenness) in flux plots was also assessed by hand-held proximal sensor, allowing the relationship between NDVI of damage plots to CO2 flux to be calculated. Despite the contrasting sites and drivers, damage had consistent, major impacts on all fluxes. All sites showed reductions in GPP and NEE with increasing damage, despite efflux from Reco also declining with damage. When scaled to site-level, reductions of up to 81% of NEE, 51% of GPP and 37% of Reco were observed. In the plot-level NDVI-flux relationship, NDVI was shown to explain up to 91% of variation in GPP, and therefore supports the use of NDVI for estimating changes in ecosystem CO2 flux at larger scales in regions where browning has been driven by extreme events. This work is the first attempt to quantify the

  10. High-field electron-photon interactions

    International Nuclear Information System (INIS)

    Hartemann, F V.

    1999-01-01

    Recent advances in novel technologies (including chirped-pulse amplification, femtosecond laser systems operating in the TW-PW range, high-gradient rf photoinjectors, and synchronized relativistic electron bunches with subpicosecond durations and THz bandwidths) allow experimentalists to study the interaction of relativistic electrons with ultrahigh-intensity photon fields. Ponderomotive scattering can accelerate these electrons with extremely high gradients in a three-dimensional vacuum laser focus. The nonlinear Doppler shift induced by relativistic radiation pressure in Compton backscattering is shown to yield complex nonlinear spectra which can be modified by using temporal laser pulse shaping techniques. Colliding laser pulses, where ponderomotive acceleration and Compton backscattering are combined, could also yield extremely short wavelength photons. Finally, one expects strong radiative corrections when the Doppler-upshifted laser wavelength approaches the Compton scale. These are discussed within the context of high-field classical electrodynamics, a new discipline borne out of the aforementioned innovations

  11. Acetate, lactate, propionate, and isobutyrate as electron donors for iron and sulfate reduction in Arctic marine sediments, Svalbard

    DEFF Research Database (Denmark)

    Finke, Niko; Vandieken, Verona; Jørgensen, Bo Barker

    2007-01-01

    The contribution of volatile fatty acids (VFA) as e--donors for anaerobic terminal oxidation of organic carbon through iron and sulfate reduction was studied in Arctic fjord sediment. Dissolved inorganic carbon, Fe2+, VFA concentrations, and sulfate reduction were monitored in slurries from...... by alternative e--donors. The accumulation of VFA in the selenate-inhibited 0-2 cm slurry did not enhance iron reduction, indicating that iron reducers were not limited by VFA availability....

  12. Mining in the European Arctic

    NARCIS (Netherlands)

    van Dam, Kim; Scheepstra, Annette; Gille, Johan; Stępień, Adam; Koivurova, Timo

    The European Arctic is currently experiencing an upsurge in mining activities, but future developments will be highly sensitive to mineral price fluctuations. The EU is a major consumer and importer of Arctic raw materials. As the EU is concerned about the security of supply, it encourages domestic

  13. Fungal colonization and decomposition of leaves and stems of Salix arctica on deglaciated moraines in high-Arctic Canada

    Science.gov (United States)

    Osono, Takashi; Matsuoka, Shunsuke; Hirose, Dai; Uchida, Masaki; Kanda, Hiroshi

    2014-06-01

    Fungal colonization, succession, and decomposition of leaves and stems of Salix arctica were studied to estimate the roles of fungi in the decomposition processes in the high Arctic. The samples were collected from five moraines with different periods of development since deglaciation to investigate the effects of ecosystem development on the decomposition processes during the primary succession. The total hyphal lengths and the length of darkly pigmented hyphae increased during decomposition of leaves and stems and were not varied with the moraines. Four fungal morphotaxa were frequently isolated from both leaves and stems. The frequencies of occurrence of two morphotaxa varied with the decay class of leaves and/or stems. The hyphal lengths and the frequencies of occurrence of fungal morphotaxa were positively or negatively correlated with the contents of organic chemical components and nutrients in leaves and stems, suggesting the roles of fungi in chemical changes in the field. Pure culture decomposition tests demonstrated that the fungal morphotaxa were cellulose decomposers. Our results suggest that fungi took part in the chemical changes in decomposing leaves and stems even under the harsh environment of the high Arctic.

  14. High-energy, high-fat lifestyle challenges an Arctic apex predator, the polar bear.

    Science.gov (United States)

    Pagano, A M; Durner, G M; Rode, K D; Atwood, T C; Atkinson, S N; Peacock, E; Costa, D P; Owen, M A; Williams, T M

    2018-02-02

    Regional declines in polar bear ( Ursus maritimus ) populations have been attributed to changing sea ice conditions, but with limited information on the causative mechanisms. By simultaneously measuring field metabolic rates, daily activity patterns, body condition, and foraging success of polar bears moving on the spring sea ice, we found that high metabolic rates (1.6 times greater than previously assumed) coupled with low intake of fat-rich marine mammal prey resulted in an energy deficit for more than half of the bears examined. Activity and movement on the sea ice strongly influenced metabolic demands. Consequently, increases in mobility resulting from ongoing and forecasted declines in and fragmentation of sea ice are likely to increase energy demands and may be an important factor explaining observed declines in body condition and survival. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  15. Contemporary Arctic Sea Level

    Science.gov (United States)

    Cazenave, A. A.

    2017-12-01

    During recent decades, the Arctic region has warmed at a rate about twice the rest of the globe. Sea ice melting is increasing and the Greenland ice sheet is losing mass at an accelerated rate. Arctic warming, decrease in the sea ice cover and fresh water input to the Arctic ocean may eventually impact the Arctic sea level. In this presentation, we review our current knowledge of contemporary Arctic sea level changes. Until the beginning of the 1990s, Arctic sea level variations were essentially deduced from tide gauges located along the Russian and Norwegian coastlines. Since then, high inclination satellite altimetry missions have allowed measuring sea level over a large portion of the Arctic Ocean (up to 80 degree north). Measuring sea level in the Arctic by satellite altimetry is challenging because the presence of sea ice cover limits the full capacity of this technique. However adapted processing of raw altimetric measurements significantly increases the number of valid data, hence the data coverage, from which regional sea level variations can be extracted. Over the altimetry era, positive trend patterns are observed over the Beaufort Gyre and along the east coast of Greenland, while negative trends are reported along the Siberian shelf. On average over the Arctic region covered by satellite altimetry, the rate of sea level rise since 1992 is slightly less than the global mea sea level rate (of about 3 mm per year). On the other hand, the interannual variability is quite significant. Space gravimetry data from the GRACE mission and ocean reanalyses provide information on the mass and steric contributions to sea level, hence on the sea level budget. Budget studies show that regional sea level trends over the Beaufort Gyre and along the eastern coast of Greenland, are essentially due to salinity changes. However, in terms of regional average, the net steric component contributes little to the observed sea level trend. The sea level budget in the Arctic

  16. Estimation of the annual primary production of the lichen Cetrariella delisei in a glacier foreland in the High Arctic, Ny-Ålesund, Svalbard

    OpenAIRE

    Uchida, Masaki; Nakatsubo, Takayuki; Kanda, Hiroshi; Koizumi, Hiroshi

    2006-01-01

    The fruticose lichen Cetrariella delisei is among the dominant lichen species in the deglaciated High Arctic areas of Svalbard. As part of a study of carbon cycling in the High Arctic, we aimed to estimate the primary production of lichen in a deglaciated area in Ny-Ålesund, Svalbard (79° N), by examining the effects of abiotic factors on the net photosynthesis (Pn) and dark respiration (R) rates of C. delisei. Experiments were conducted in the snow-free season of 2000 using an open-fl ow gas...

  17. Ice nucleating particles in the high Arctic at the beginning of the melt season

    Science.gov (United States)

    Hartmann, M.; Gong, X.; Van Pinxteren, M.; Welti, A.; Zeppenfeld, S.; Herrmann, H.; Stratmann, F.

    2017-12-01

    Ice nucleating particles (INPs) initiate the ice crystal formation in persistent Arctic mixed-phase clouds and are important for the formation of precipitation, which affects the radiative properties of the Arctic pack ice as well as the radiative properties of clouds. Sources of Arctic INP have been suggested to be local emissions from the marine boundary and long-range transport. To what extent local marine sources contribute to the INP population or if the majority of INPs originate from long-range transport is not yet known. Ship-based INP measurements in the PASCAL framework are reported. The field campaign took place from May 24 to July 20 2017 around and north of Svalbard (up to 84°N, between 0° and 35°E) onboard the RV Polarstern. INP concentrations were determined applying in-situ measurements (DMT Spectrometer for Ice Nuclei, SPIN) and offline filter techniques (filter sampling on both quartz fiber and polycarbonate filters with subsequent analysis of filter pieces and water suspension from particles collected on filters by means of immersion freezing experiments on cold stage setups). Additionally the compartments sea-surface micro layer (SML), bulk sea water, snow, sea ice and fog water were sampled and their ice nucleation potential quantified, also utilizing cold stages. The measurements yield comprehensive picture of the spatial and temporal distribution of INPs around Svalbard for the different compartments. The dependence of the INP concentration on meteorological conditions (e.g. wind speed) and the geographical situation (sea ice cover, distance to the ice edge) are investigated. Potential sources of INP are identified by the comparison of INP concentrations in the compartments and by back trajectory analysis.

  18. High Energy Electron Detectors on Sphinx

    Science.gov (United States)

    Thompson, J. R.; Porte, A.; Zucchini, F.; Calamy, H.; Auriel, G.; Coleman, P. L.; Bayol, F.; Lalle, B.; Krishnan, M.; Wilson, K.

    2008-11-01

    Z-pinch plasma radiation sources are used to dose test objects with K-shell (˜1-4keV) x-rays. The implosion physics can produce high energy electrons (> 50keV), which could distort interpretation of the soft x-ray effects. We describe the design and implementation of a diagnostic suite to characterize the electron environment of Al wire and Ar gas puff z-pinches on Sphinx. The design used ITS calculations to model detector response to both soft x-rays and electrons and help set upper bounds to the spurious electron flux. Strategies to discriminate between the known soft x-ray emission and the suspected electron flux will be discussed. H.Calamy et al, ``Use of microsecond current prepulse for dramatic improvements of wire array Z-pinch implosion,'' Phys Plasmas 15, 012701 (2008) J.A.Halbleib et al, ``ITS: the integrated TIGER series of electron/photon transport codes-Version 3.0,'' IEEE Trans on Nuclear Sci, 39, 1025 (1992)

  19. Collaborative Research: Towards Advanced Understanding and Predictive Capability of Climate Change in the Arctic Using a High-Resolution Regional Arctic Climate Model

    Energy Technology Data Exchange (ETDEWEB)

    Cassano, John [Principal Investigator

    2013-06-30

    The primary research task completed for this project was the development of the Regional Arctic Climate Model (RACM). This involved coupling existing atmosphere, ocean, sea ice, and land models using the National Center for Atmospheric Research (NCAR) Community Climate System Model (CCSM) coupler (CPL7). RACM is based on the Weather Research and Forecasting (WRF) atmospheric model, the Parallel Ocean Program (POP) ocean model, the CICE sea ice model, and the Variable Infiltration Capacity (VIC) land model. A secondary research task for this project was testing and evaluation of WRF for climate-scale simulations on the large pan-Arctic model domain used in RACM. This involved identification of a preferred set of model physical parameterizations for use in our coupled RACM simulations and documenting any atmospheric biases present in RACM.

  20. High Performance Electronics on Flexible Silicon

    KAUST Repository

    Sevilla, Galo T.

    2016-09-01

    Over the last few years, flexible electronic systems have gained increased attention from researchers around the world because of their potential to create new applications such as flexible displays, flexible energy harvesters, artificial skin, and health monitoring systems that cannot be integrated with conventional wafer based complementary metal oxide semiconductor processes. Most of the current efforts to create flexible high performance devices are based on the use of organic semiconductors. However, inherent material\\'s limitations make them unsuitable for big data processing and high speed communications. The objective of my doctoral dissertation is to develop integration processes that allow the transformation of rigid high performance electronics into flexible ones while maintaining their performance and cost. In this work, two different techniques to transform inorganic complementary metal-oxide-semiconductor electronics into flexible ones have been developed using industry compatible processes. Furthermore, these techniques were used to realize flexible discrete devices and circuits which include metal-oxide-semiconductor field-effect-transistors, the first demonstration of flexible Fin-field-effect-transistors, and metal-oxide-semiconductors-based circuits. Finally, this thesis presents a new technique to package, integrate, and interconnect flexible high performance electronics using low cost additive manufacturing techniques such as 3D printing and inkjet printing. This thesis contains in depth studies on electrical, mechanical, and thermal properties of the fabricated devices.

  1. High energy electron irradiation of flowable materials

    International Nuclear Information System (INIS)

    Offermann, B.P.

    1975-01-01

    In order to efficiently irradiate a flowable material with high energy electrons, a hollow body is disposed in a container for the material and the material is caused to flow in the form of a thin layer across a surface of the body from or to the interior of the container while the material flowing across the body surface is irradiated. (U.S.)

  2. KEK/NAGOYA/SLAC: Highly polarized electrons

    International Nuclear Information System (INIS)

    Anon.

    1994-01-01

    In the push by the Japanese KEK Laboratory, in collaboration with university groups and overseas laboratories, to develop new techniques for the future Japan electronpositron collider (JLC), a recent achievement is a significant increase in the efficient yield of highly polarized electrons

  3. Decal Electronics: Printable Packaged with 3D Printing High-Performance Flexible CMOS Electronic Systems

    KAUST Repository

    Sevilla, Galo T.

    2016-10-14

    High-performance complementary metal oxide semiconductor electronics are flexed, packaged using 3D printing as decal electronics, and then printed in roll-to-roll fashion for highly manufacturable printed flexible high-performance electronic systems.

  4. Decal Electronics: Printable Packaged with 3D Printing High-Performance Flexible CMOS Electronic Systems

    KAUST Repository

    Sevilla, Galo T.; Cordero, Marlon D.; Nassar, Joanna M.; Hanna, Amir; Kutbee, Arwa T.; Carreno, Armando Arpys Arevalo; Hussain, Muhammad Mustafa

    2016-01-01

    High-performance complementary metal oxide semiconductor electronics are flexed, packaged using 3D printing as decal electronics, and then printed in roll-to-roll fashion for highly manufacturable printed flexible high-performance electronic systems.

  5. High Resolution CH4 Emissions and Dissolved CH4 Measurements Elucidate Surface Gas Exchange Processes in Toolik Lake, Arctic Alaska

    Science.gov (United States)

    Del Sontro, T.; Sollberger, S.; Kling, G. W.; Shaver, G. R.; Eugster, W.

    2013-12-01

    Approximately 14% of the Alaskan North Slope is covered in lakes of various sizes and depths. Diffusive carbon emissions (CH4 and CO2) from these lakes offset the tundra sink by ~20 %, but the offset would substantially increase if ebullitive CH4 emissions were also considered. Ultimately, arctic lake CH4 emissions are not insignificant in the global CH4 budget and their contribution is bound to increase due to impacts from climate change. Here we present high resolution CH4 emission data as measured via eddy covariance and a Los Gatos gas analyzer during the ice free period from Toolik Lake, a deep (20 m) Arctic lake located on the Alaskan North Slope, over the last few summers. Emissions are relatively low (Gatos gas analyzer. Thus, having both the flux and the CH4 gradient across the air-water interface measured directly, we can calculate k and investigate the processes influencing CH4 gas exchange in this lake. Preliminary results indicate that there are two regimes in wind speed that impact k - one at low wind speeds up to ~5 m s-1 and another at higher wind speeds (max ~10 m s-1). The differential wind speeds during night and day may compound the effect of convective mixing and cause the diurnal variation in observed fluxes.

  6. The alien terrestrial invertebrate fauna of the High Arctic archipelago of Svalbard: potential implications for the native flora and fauna

    Directory of Open Access Journals (Sweden)

    Stephen J. Coulson

    2015-09-01

    Full Text Available Experience from the Antarctic indicates that the establishment of alien species may have significant negative effects on native flora and fauna in polar regions and is considered to be amongst the greatest threats to biodiversity. But, there have been few similar studies from the Arctic. Although the terrestrial invertebrate inventory of the Svalbard Archipelago is amongst the most complete for any region of the Arctic, no consideration has yet been made of alien terrestrial invertebrate species, their invasiveness tendencies, threat to the native biology or their route of entry. Such baseline information is critical for appropriate management strategies. Fifteen alien invertebrate species have established in the Svalbard environment, many of which have been introduced via imported soils. Biosecurity legislation now prohibits such activities. None of the recorded established aliens yet show invasive tendencies but some may have locally negative effects. Ten species are considered to be vagrants and a further seven are classified as observations. Vagrants and the observations are not believed to be able to establish in the current tundra environment. The high connectivity of Svalbard has facilitated natural dispersal processes and may explain why few alien species are recorded compared to isolated islands in the maritime Antarctic. The vagrant species observed are conspicuous Lepidoptera, implying that less evident vagrant species are also arriving regularly. Projected climate change may enable vagrant species to establish, with results that are difficult to foresee.

  7. Trophic dynamics in marine nearshore systems of the Alaskan high arctic

    International Nuclear Information System (INIS)

    Dunton, K.H.

    1985-01-01

    This dissertation describes two ecological studies in the arctic Alaskan nearshore zone: the productivity and growth strategies of arctic kelp and the use of natural carbon isotope abundances to examine food web structure and energy flow in the marine ecosystem. Linear growth of the kelp, Laminaria solidungula is greatest in winter and early spring when nutrients are available for new tissue growth. Since over 90% of this growth occurs in complete darkness beneath a turbid ice canopy, the plant draws on stored food reserves and is in a carbon deficit during the ice covered period. Annual productivity of L. solidungula under these conditions is about 6 g C m -2 compared to about 10 g c m -2 if light penetrates the ice canopy. Carbon isotope abundances were used to assess food web structure and energy flow in the Boulder Patch, an isolated kelp bed community, and in the Alaskan Beaufort Sea fauna. Isotopic analyses of the resident fauna of the Boulder Patch revealed that kelp carbon contributes significantly to the diet of many benthic animals, including suspension feeders. Across the shelf of the Alaskan Beaufort Sea, a distinct gradient in the isotopic composition of marine zooplankton and benthic fauna was related to the intrusion of the Bering Sea water and upwelling in the eastern Beaufort Sea near Barter Island. The 13 C depletion in fauna of the eastern Beaufort Sea is presumed due to the cycling of 13 C depleted inorganic carbon into the euphotic zone

  8. Comparison of publically available Moho depth and crustal thickness grids with newly derived grids by 3D gravity inversion for the High Arctic region.

    Science.gov (United States)

    Lebedeva-Ivanova, Nina; Gaina, Carmen; Minakov, Alexander; Kashubin, Sergey

    2016-04-01

    We derived Moho depth and crustal thickness for the High Arctic region by 3D forward and inverse gravity modelling method in the spectral domain (Minakov et al. 2012) using lithosphere thermal gravity anomaly correction (Alvey et al., 2008); a vertical density variation for the sedimentary layer and lateral crustal variation density. Recently updated grids of bathymetry (Jakobsson et al., 2012), gravity anomaly (Gaina et al, 2011) and dynamic topography (Spasojevic & Gurnis, 2012) were used as input data for the algorithm. TeMAr sedimentary thickness grid (Petrov et al., 2013) was modified according to the most recently published seismic data, and was re-gridded and utilized as input data. Other input parameters for the algorithm were calibrated using seismic crustal scale profiles. The results are numerically compared with publically available grids of the Moho depth and crustal thickness for the High Arctic region (CRUST 1 and GEMMA global grids; the deep Arctic Ocean grids by Glebovsky et al., 2013) and seismic crustal scale profiles. The global grids provide coarser resolution of 0.5-1.0 geographic degrees and not focused on the High Arctic region. Our grids better capture all main features of the region and show smaller error in relation to the seismic crustal profiles compare to CRUST 1 and GEMMA grids. Results of 3D gravity modelling by Glebovsky et al. (2013) with separated geostructures approach show also good fit with seismic profiles; however these grids cover the deep part of the Arctic Ocean only. Alvey A, Gaina C, Kusznir NJ, Torsvik TH (2008). Integrated crustal thickness mapping and plate recon-structions for the high Arctic. Earth Planet Sci Lett 274:310-321. Gaina C, Werner SC, Saltus R, Maus S (2011). Circum-Arctic mapping project: new magnetic and gravity anomaly maps of the Arctic. Geol Soc Lond Mem 35, 39-48. Glebovsky V.Yu., Astafurova E.G., Chernykh A.A., Korneva M.A., Kaminsky V.D., Poselov V.A. (2013). Thickness of the Earth's crust in the

  9. Correlation of wind and solar power in high-latitude arctic areas in Northern Norway and Svalbard

    Directory of Open Access Journals (Sweden)

    Solbakken Kine

    2016-01-01

    Full Text Available This paper assesses the possibilities for combining wind and solar power in a household-scale hybrid renewable energy system in arctic high-latitude areas in the North of Norway. By combining two complementary renewable energy sources, the efficiency and reliability of the power output can be improved compared to a system utilizing wind or solar power independently. This paper assesses the correlation between wind and solar power on different timescales in four different locations in Northern Norway and Svalbard. For all locations complementary characteristics of wind and solar power are found, however, the strength of the correlation is highly variable for each location and for the different timescales. The best correlation for all places is found on a monthly timescale. HOMER is used to run simulations on hybrid renewable energy systems (HRES for each location. For three of the four locations the HRES produces more power than what is consumed in the household.

  10. Migratory birds are the source of highly toxic organic pollutants for indigenous people in the Russian Arctic

    Science.gov (United States)

    Pesiakova, A. A.; Gusakova, E. V.; Trofimova, A. N.; Sorokina, T. Yu

    2018-01-01

    Polychlorinated biphenyls are highly toxic organic contaminants. Due to their chemical properties they had wide application in industry and agriculture in the 20th century. In 2001 the production of PCBs has been prohibited almost worldwide. Environmental contamination has been found in soils, water, and air where there were PCB production sites. They have been detected in fish, birds and animals of migratory species, retaining transboarding transfer. Several migratory species of birds (Taiga bean goose, greater white-fronted goose, lesser white fronted goose and barnacle goose) are a diet for indigenous people. PCBs accumulating in the human body affect all systems and organs. This article reviews the contribution of migratory bird species in transboarding transfer of highly toxic contaminants in the Nenets Autonomous Area, Kolguev island (Russian Arctic).

  11. FRAM-2012: Norwegians return to the High Arctic with a Hovercraft for Marine Geophysical Research

    Science.gov (United States)

    Hall, J. K.; Kristoffersen, Y.; Brekke, H.; Hope, G.

    2012-12-01

    After four years of testing methods, craft reliability, and innovative equipment, the R/H SABVABAA has embarked on its first FRAM-201x expedition to the highest Arctic. Named after the Inupiaq word for 'flows swiftly over it', the 12m by 6m hovercraft has been home-based in Longyearbyen, Svalbard since June 2008. In this, its fifth summer of work on the ice pack north of 81N, the craft is supported by the Norwegian Petroleum Directorate (NPD) via the Nansen Environmental and Remote Sensing Center (NERSC) in Bergen, and the Norwegian Scientific Academy for Polar Research. FRAM-2012 represents renewed Norwegian interest in returning to the highest Arctic some 116 years after the 1893-96 drift of Fridtjof Nansen's ship FRAM, the first serious scientific investigation of the Arctic. When replenished by air or icebreaker, the hovercraft Sabvabaa offers a hospitable scientific platform with crew of two, capable of marine geophysical, geological and oceanographic observations over long periods with relative mobility on the ice pack. FRAM-2012 is the first step towards this goal, accompanying the Swedish icebreaker ODEN to the Lomonosov Ridge, north of Greenland, as part of the LOMROG III expedition. The science plan called for an initial drive from the ice edge to Gakkel Ridge at 85N where micro-earthquakes would be monitored, and then to continue north to a geological sampling area on the Lomonosov Ridge at about 88N, 65W. The micro-earthquake monitoring is part of Gaute Hope's MSc thesis and entails five hydrophones in a WiFi-connected hydrophone array deployed over the Gakkel Rift Valley, drifting with the ice at up to 0.4 knots. On August 3 the hovercraft was refueled from icebreaker ODEN at 84-21'N and both vessels proceeded north. The progress of the hovercraft was hampered by insufficient visibility for safe driving and time consuming maneuvering in and around larger fields of rubble ice impassable by the hovercraft, but of little concern to the icebreaker. It

  12. Considerations for high-brightness electron sources

    International Nuclear Information System (INIS)

    Jameson, R.A.

    1990-01-01

    Particle accelerators are now used in many areas of physics research and in industrial and medical applications. New uses are being studied to address major societal needs in energy production, materials research, generation of intense beams of radiation at optical and suboptical wavelengths, treatment of various kinds of waste, and so on. Many of these modern applications require a high intensity beam at the desired energy, along with a very good beam quality in terms of the beam confinement, aiming, or focusing. Considerations for ion and electron accelerators are often different, but there are also many commonalties, and in fact, techniques derived for one should perhaps more often be considered for the other as well. We discuss some aspects of high-brightness electron sources here from that point of view. 6 refs

  13. The Arctic

    International Nuclear Information System (INIS)

    Petersen, H.; Meltofte, H.; Rysgaard, S.; Rasch, M.; Jonasson, S.; Christensen, T.R.; Friborg, T.; Soegaard, H.; Pedersen, S.A.

    2001-01-01

    Global climate change in the Arctic is a growing concern. Research has already documented pronounced changes, and models predict that increases in temperature from anthropogenic influences could be considerably higher than the global average. The impacts of climate change on Arctic ecosystems are complex and difficult to predict because of the many interactions within ecosystem, and between many concurrently changing environmental variables. Despite the global consequences of change in the Arctic climate the monitoring of basic abiotic as well as biotic parameters are not adequate to assess the impact of global climate change. The uneven geographical location of present monitoring stations in the Arctic limits the ability to understand the climate system. The impact of previous variations and potential future changes to ecosystems is not well understood and need to be addressed. At this point, there is no consensus of scientific opinion on how much of the current changes that are due to anthropogenic influences or to natural variation. Regardless of the cause, there is a need to investigate and assess current observations and their effects to the Arctic. In this chapter examples from both terrestrial and marine ecosystems from ongoing monitoring and research projects are given. (LN)

  14. Electronics, information, Communication and high technology

    International Nuclear Information System (INIS)

    1999-11-01

    The contents of this book are summary of investigation, investigation system, purpose of investigation, characteristic of this investigation, important studying and development filed, compare of the level of research and development, policy, characteristic of the respondent, a future illustration in 2025 cause of hindrance of realization, propel method of research and development, the prediction of the realization period the result of investigation in electronics, information communication and high technology.

  15. Arctic species resilience

    DEFF Research Database (Denmark)

    Mortensen, Lars O.; Forchhammer, Mads C.; Jeppesen, Erik

    The peak of biological activities in Arctic ecosystems is characterized by a relative short and intense period between the start of snowmelt until the onset of frost. Recent climate changes have induced larger seasonal variation in both timing of snowmelt as well as changes mean temperatures......, an extensive monitoring program has been conducted in the North Eastern Greenland National Park, the Zackenberg Basic. The objective of the program is to provide long time series of data on the natural innate oscillations and plasticity of a High Arctic ecosystem. With offset in the data provided through...

  16. Physics of high intensity nanosecond electron source

    International Nuclear Information System (INIS)

    Herrera-Gomez, A.; Spicer, W.E.

    1993-08-01

    A new high-intensity, short-time electron source is now being used at the Stanford Linear Accelerator Center (SLAC). Using a GaAs negative affinity semiconductor in the construction of the cathode, it is possible to fulfill operation requirements such as peak currents of tens of amperes, peak widths of the order of nanoseconds, hundreds of hours of operation stability, and electron spin polarization. The cathode is illuminated with high intensity laser pulses, and photoemitted electrons constitute the yield. Because of the high currents, some nonlinear effects are present. Very noticeable is the so-called Charge Limit (CL) effect, which consists of a limit on the total charge in each pulse-that is, the total bunch charge stops increasing as the light pulse total energy increases. In this paper, we explain the mechanism of the CL and how it is caused by the photovoltaic effect. Our treatment is based on the Three-Step model of photoemission. We relate the CL to the characteristics of the surface and bulk of the semiconductor, such as doping, band bending, surface vacuum level, and density of surface states. We also discuss possible ways to prevent the Char's Level effect

  17. Imposex occurrence in marine whelks at a military facility in the high Arctic

    Energy Technology Data Exchange (ETDEWEB)

    Strand, Jakob [Department of Marine Ecology, National Environmental Research Institute, Frederiksborgvej 399, P.O. Box 358, 4000 Roskilde (Denmark)]. E-mail: jak@dmu.dk; Glahder, Christian M. [Department of Arctic Environment, National Environmental Research Institute, Frederiksborgvej 399, 4000 Roskilde (Denmark); Asmund, Gert [Department of Arctic Environment, National Environmental Research Institute, Frederiksborgvej 399, 4000 Roskilde (Denmark)

    2006-07-15

    Imposex was found in the Arctic whelk Buccinum finmarkianum at several marine stations off Thule Air Base, an US military facility in Northwest Greenland. This indicates a widespread contamination with the antifouling agents, tributyltin (TBT) or triphenyltin (TPhT) in the area, but such contamination was not supported by the organotin analyses in sediments, whelks and clams, which in general was below the analytical detection limit. Organotin concentrations above the detection limit were found only at one station close to a quay, where the highest frequency of imposex also occurred. This suggests that imposex in B. finmarkianum is a biomarker of TBT more sensitive than the detection limits, which the analytical chemistry could achieve in this study. - Imposex as a biomarker was more sensitive for TBT than analytical chemical methods.

  18. Imposex occurrence in marine whelks at a military facility in the high Arctic

    International Nuclear Information System (INIS)

    Strand, Jakob; Glahder, Christian M.; Asmund, Gert

    2006-01-01

    Imposex was found in the Arctic whelk Buccinum finmarkianum at several marine stations off Thule Air Base, an US military facility in Northwest Greenland. This indicates a widespread contamination with the antifouling agents, tributyltin (TBT) or triphenyltin (TPhT) in the area, but such contamination was not supported by the organotin analyses in sediments, whelks and clams, which in general was below the analytical detection limit. Organotin concentrations above the detection limit were found only at one station close to a quay, where the highest frequency of imposex also occurred. This suggests that imposex in B. finmarkianum is a biomarker of TBT more sensitive than the detection limits, which the analytical chemistry could achieve in this study. - Imposex as a biomarker was more sensitive for TBT than analytical chemical methods

  19. Modelling temperature-dependent heat production over decades in High Arctic coal waste rock piles

    DEFF Research Database (Denmark)

    Hollesen, Jørgen; Elberling, Bo; Jansson, P.E.

    2011-01-01

    Subsurface heat production from oxidation of pyrite is an important process that may increase subsurface temperatures within coal waste rock piles and increase the release of acid mine drainage, AMD. Waste rock piles in the Arctic are especially vulnerable to changes in subsurface temperatures...... such as heat production from coal oxidation may be equally important....... as the release of AMD normally is limited by permafrost. Here we show that temperatures within a 20 year old heat-producing waste rock pile in Svalbard (78°N) can be modelled by the one-dimensional heat and water flow model (CoupModel) with a new temperature-dependent heat-production module that includes both...

  20. Arctic smoke – record high air pollution levels in the European Arctic due to agricultural fires in Eastern Europe in spring 2006

    Directory of Open Access Journals (Sweden)

    A. Stohl

    2007-01-01

    Full Text Available In spring 2006, the European Arctic was abnormally warm, setting new historical temperature records. During this warm period, smoke from agricultural fires in Eastern Europe intruded into the European Arctic and caused the most severe air pollution episodes ever recorded there. This paper confirms that biomass burning (BB was indeed the source of the observed air pollution, studies the transport of the smoke into the Arctic, and presents an overview of the observations taken during the episode. Fire detections from the MODIS instruments aboard the Aqua and Terra satellites were used to estimate the BB emissions. The FLEXPART particle dispersion model was used to show that the smoke was transported to Spitsbergen and Iceland, which was confirmed by MODIS retrievals of the aerosol optical depth (AOD and AIRS retrievals of carbon monoxide (CO total columns. Concentrations of halocarbons, carbon dioxide and CO, as well as levoglucosan and potassium, measured at Zeppelin mountain near Ny Ålesund, were used to further corroborate the BB source of the smoke at Spitsbergen. The ozone (O3 and CO concentrations were the highest ever observed at the Zeppelin station, and gaseous elemental mercury was also elevated. A new O3 record was also set at a station on Iceland. The smoke was strongly absorbing – black carbon concentrations were the highest ever recorded at Zeppelin – and strongly perturbed the radiation transmission in the atmosphere: aerosol optical depths were the highest ever measured at Ny Ålesund. We furthermore discuss the aerosol chemical composition, obtained from filter samples, as well as the aerosol size distribution during the smoke event. Photographs show that the snow at a glacier on Spitsbergen became discolored during the episode and, thus, the snow albedo was reduced. Samples of this polluted snow contained strongly elevated levels of potassium, sulphate, nitrate and ammonium ions, thus relating the discoloration to the

  1. Metagenomic analysis of the bioremediation of diesel-contaminated Canadian high arctic soils.

    Science.gov (United States)

    Yergeau, Etienne; Sanschagrin, Sylvie; Beaumier, Danielle; Greer, Charles W

    2012-01-01

    As human activity in the Arctic increases, so does the risk of hydrocarbon pollution events. On site bioremediation of contaminated soil is the only feasible clean up solution in these remote areas, but degradation rates vary widely between bioremediation treatments. Most previous studies have focused on the feasibility of on site clean-up and very little attention has been given to the microbial and functional communities involved and their ecology. Here, we ask the question: which microorganisms and functional genes are abundant and active during hydrocarbon degradation at cold temperature? To answer this question, we sequenced the soil metagenome of an ongoing bioremediation project in Alert, Canada through a time course. We also used reverse-transcriptase real-time PCR (RT-qPCR) to quantify the expression of several hydrocarbon-degrading genes. Pseudomonas species appeared as the most abundant organisms in Alert soils right after contamination with diesel and excavation (t = 0) and one month after the start of the bioremediation treatment (t = 1m), when degradation rates were at their highest, but decreased after one year (t = 1y), when residual soil hydrocarbons were almost depleted. This trend was also reflected in hydrocarbon degrading genes, which were mainly affiliated with Gammaproteobacteria at t = 0 and t = 1m and with Alphaproteobacteria and Actinobacteria at t = 1y. RT-qPCR assays confirmed that Pseudomonas and Rhodococcus species actively expressed hydrocarbon degradation genes in Arctic biopile soils. Taken together, these results indicated that biopile treatment leads to major shifts in soil microbial communities, favoring aerobic bacteria that can degrade hydrocarbons.

  2. Metagenomic analysis of the bioremediation of diesel-contaminated Canadian high arctic soils.

    Directory of Open Access Journals (Sweden)

    Etienne Yergeau

    Full Text Available As human activity in the Arctic increases, so does the risk of hydrocarbon pollution events. On site bioremediation of contaminated soil is the only feasible clean up solution in these remote areas, but degradation rates vary widely between bioremediation treatments. Most previous studies have focused on the feasibility of on site clean-up and very little attention has been given to the microbial and functional communities involved and their ecology. Here, we ask the question: which microorganisms and functional genes are abundant and active during hydrocarbon degradation at cold temperature? To answer this question, we sequenced the soil metagenome of an ongoing bioremediation project in Alert, Canada through a time course. We also used reverse-transcriptase real-time PCR (RT-qPCR to quantify the expression of several hydrocarbon-degrading genes. Pseudomonas species appeared as the most abundant organisms in Alert soils right after contamination with diesel and excavation (t = 0 and one month after the start of the bioremediation treatment (t = 1m, when degradation rates were at their highest, but decreased after one year (t = 1y, when residual soil hydrocarbons were almost depleted. This trend was also reflected in hydrocarbon degrading genes, which were mainly affiliated with Gammaproteobacteria at t = 0 and t = 1m and with Alphaproteobacteria and Actinobacteria at t = 1y. RT-qPCR assays confirmed that Pseudomonas and Rhodococcus species actively expressed hydrocarbon degradation genes in Arctic biopile soils. Taken together, these results indicated that biopile treatment leads to major shifts in soil microbial communities, favoring aerobic bacteria that can degrade hydrocarbons.

  3. Isolation and characterization of coliforms from glacial ice and water in Canada's High Arctic.

    Science.gov (United States)

    Dancer, S J; Shears, P; Platt, D J

    1997-05-01

    Ellesmere Island is the northern most member of the Canadian Arctic Archipelago with over one-third of the land mass covered by ice. A joint services expedition to the island's Blue Mountains offered a unique opportunity for microbiological studies of resident bacteria in an environment uninhabited by man. Over 100 samples of water and ice were collected from stream, lake and glacier and the filtrate cultured under canvas. Bacterial growth was harvested onto swabs for transport back to the UK and 50 coliforms chosen at random for identification and antibiotic susceptibility testing. Most of the glacial strains were capsulated, pigmented and some over 2000 years old. Genera such as Serratia, Enterobacter, Klebsiella and Yersinia were found; speciation was inconclusive and some organisms remain unidentified. Ampicillin resistance was evident in 80% of water isolates as opposed to 30% of the glacial organisms, but the isolates were generally exquisitely susceptible to antibiotics. The facility for ampicillin resistance did not appear to be transferable. Plasmid DNA was found in 33% of the glacial organisms and over 50% of the water isolates. Similar profiles were identified within and apparently between species and required plasmid restriction analysis to help establish identity. Plasmid-free Serratia spp. were subjected to genomic fingerprinting. Indistinguishable patterns were found within sets of isolates both widely spaced by distance and collection date and it was postulated that coliforms able to survive an Arctic environment had spread extensively throughout the expedition area. In conclusion, this study contributes towards knowledge of naturally occurring antibiotic resistance, confirms the presence of plasmids and genotypic data provided evidence that potentially ancient organisms from glaciers can be cultured from water samples significantly distant.

  4. Spatial and temporal patterns of sea ice variations in Vilkitsky strait, Russian High Arctic

    Science.gov (United States)

    Ci, T.; Cheng, X.; Hui, F.

    2013-12-01

    The Arctic Ocean has been greatly affected by climate change. Future predications show an even more drastic reduction of the ice cap which will open new areas for the exploration of natural resources and maritime transportation.Shipping through the Arctic Ocean via the Northern Sea Route (NSR) could save about 40% of the sailing distance from Asia (Yokohama) to Europe (Rotterdam) compared to the traditional route via the Suez Canal. Vilkitsky strait is the narrowest and northest portion of the Northern Sea Route with heaviest traffic between the Taimyr Peninsular and the Severnaya Zemlya archipelago. The preliminary results of sea ice variations are presented by using moderate-resolution imaging spectro radiometer(MODIS) data with 250-m resolution in the Vilkitsky strait during 2009-2012. Temporally, the first rupture on sea ice in Vilkitsky strait usually comes up in April and sea ice completely break into pieces in early June. The strait would be ice-free between August and late September. The frequency of ice floes grows while temperature falls down in October. There are always one or two months suitable for transport. Spatially, Sea ice on Laptev sea side breaks earlier than that of Kara sea side while sea ice in central of strait breaks earlier than in shoreside. The phenomena are directly related with the direction of sea wind and ocean current. In summmary, study on Spatial and temporal patterns in this area is significant for the NSR. An additional research issue to be tackled is to seeking the trends of ice-free duration in the context of global warming. Envisat ASAR data will also be used in this study.

  5. Metagenomic Analysis of the Bioremediation of Diesel-Contaminated Canadian High Arctic Soils

    Science.gov (United States)

    Yergeau, Etienne; Sanschagrin, Sylvie; Beaumier, Danielle; Greer, Charles W.

    2012-01-01

    As human activity in the Arctic increases, so does the risk of hydrocarbon pollution events. On site bioremediation of contaminated soil is the only feasible clean up solution in these remote areas, but degradation rates vary widely between bioremediation treatments. Most previous studies have focused on the feasibility of on site clean-up and very little attention has been given to the microbial and functional communities involved and their ecology. Here, we ask the question: which microorganisms and functional genes are abundant and active during hydrocarbon degradation at cold temperature? To answer this question, we sequenced the soil metagenome of an ongoing bioremediation project in Alert, Canada through a time course. We also used reverse-transcriptase real-time PCR (RT-qPCR) to quantify the expression of several hydrocarbon-degrading genes. Pseudomonas species appeared as the most abundant organisms in Alert soils right after contamination with diesel and excavation (t = 0) and one month after the start of the bioremediation treatment (t = 1m), when degradation rates were at their highest, but decreased after one year (t = 1y), when residual soil hydrocarbons were almost depleted. This trend was also reflected in hydrocarbon degrading genes, which were mainly affiliated with Gammaproteobacteria at t = 0 and t = 1m and with Alphaproteobacteria and Actinobacteria at t = 1y. RT-qPCR assays confirmed that Pseudomonas and Rhodococcus species actively expressed hydrocarbon degradation genes in Arctic biopile soils. Taken together, these results indicated that biopile treatment leads to major shifts in soil microbial communities, favoring aerobic bacteria that can degrade hydrocarbons. PMID:22253877

  6. The Arctic zone: possibilities and risks of development

    Science.gov (United States)

    Sentsov, A.; Bolsunovskaya, Y.; Melnikovich, E.

    2016-09-01

    The authors analyze the Arctic region innovative possibilities from the perspective of political ideology and strategy. The Arctic region with its natural resources and high economic potential attracts many companies and it has become an important area of transnational development. At present, the Arctic region development is of great importance in terms of natural resource management and political system development. However, the most important development issue in the Arctic is a great risk of different countries’ competing interests in economic, political, and legal context. These are challenges for international partnership creating in the Arctic zone, Russian future model developing for the Arctic, and recognition of the Arctic as an important resource for the Russians. The Russian economic, military, and political expansion in the Arctic region has the potential to strengthen the national positions. The authors present interesting options for minimizing and eliminating political risks during the Arctic territories development and define an effective future planning model for the Russian Arctic.

  7. Highly integrated electronics for the star TPC

    Energy Technology Data Exchange (ETDEWEB)

    Arthur, A.A.; Bieser, F.; Hearn, W.; Kleinfelder, S.; Merrick, T.; Millaud, J.; Noggle, T.; Rai, G.; Ritter, H.G.; Wieman, H. [Lawrence Berkeley Laboratory, CA (United States)

    1991-12-31

    The concept for the STAR TPC front-end electronics is presented and the progress toward the development of a fully integrated solution is described. It is the goal of the R+D program to develop the complete electronics chain for the STAR central TPC detector at RHIC. It is obvious that solutions chosen e.g. for ALEPH are not adequate for the 150000 channels that need to be instrumented for readout. It will be necessary to perform all the signal processing, digitization and multiplexing directly on the detector in order to reduce per channel cost and the amount of cabling necessary to read out the information. We follow the approach chosen by the EOS TPC project, where the readout electronics on the detector consists of an integrated preamplifier, a hybrid shaping amplifier, an integrated switched capacitor array and a highly multiplexed ADC. The STAR electronics will be further integrated so that approximately 16 channels of the preamplifier, the shaper, the analog store and the ADC will be contained in two integrated circuits located directly on the pad plane.

  8. Water circulation within a high-Arctic glaciated valley (Petunia Bay, Central Spitsbergen): Recharge of a glacial river

    Science.gov (United States)

    Marciniak, Marek; Dragon, Krzysztof; Chudziak, Łukasz

    2014-05-01

    This article presents an investigation of the runoff of a glacial river located in the high Arctic region of Spitsbergen. The Ebba River runoff was measured during three melting seasons of 2007, 2008 and 2009. The most important component of the river recharge is the flow of melting water from glaciers (76-82% of total river runoff). However, the other components (surface water and groundwater) also made a significant contribution to the river recharge. The contribution of groundwater flow in total river runoff was estimated by measurements performed in four groups of piezometers located in different parts of the valley. The hydrogeological parameters that characterize shallow aquifer (thickness of the active layer, hydraulic conductivity, groundwater level fluctuations) were recognized by direct field measurements. The groundwater recharging river was the most variable recharge component, and ranged from 1% of the total runoff at the beginning of the melting season to even 27% at the end of summer.

  9. Strong linkage between active microbial communities and microbial carbon usage in a deglaciated terrain of the High Arctic

    Science.gov (United States)

    Kim, M.; Gyeong, H. R.; Lee, Y. K.

    2017-12-01

    Soil microorganisms play pivotal roles in ecosystem development and carbon cycling in newly exposed glacier forelands. However, little is known about carbon utilization pattern by metabolically active microbes over the course of ecosystem succession in these nutrient-poor environments. We investigated RNA-based microbial community dynamics and its relation to microbial carbon usage along the chronosequence of a High Arctic glacier foreland. Among microbial taxa surveyed (bacteria, archaea and fungi), bacteria are among the most metabolically active taxa with a dominance of Cyanobacteria and Actinobacteria. There was a strong association between microbial carbon usage and active Actinobacterial communities, suggesting that member of Actinobacteria are actively involved in organic carbon degradation in glacier forelands. Both bacterial community and microbial carbon usage are converged towards later stage of succession, indicating that the composition of soil organic carbon plays important roles in structuring bacterial decomposer communities during ecosystem development.

  10. Arctic bioremediation

    International Nuclear Information System (INIS)

    Lidell, B.V.; Smallbeck, D.R.; Ramert, P.C.

    1991-01-01

    Cleanup of oil and diesel spills on gravel pads in the Arctic has typically been accomplished by utilizing a water flushing technique to remove the gross contamination or excavating the spill area and placing the material into a lined pit, or a combination of both. Enhancing the biological degradation of hydrocarbon (bioremediation) by adding nutrients to the spill area has been demonstrated to be an effective cleanup tool in more temperate locations. However, this technique has never been considered for restoration in the Arctic because the process of microbial degradation of hydrocarbon in this area is very slow. The short growing season and apparent lack of nutrients in the gravel pads were thought to be detrimental to using bioremediation to cleanup Arctic oil spills. This paper discusses the potential to utilize bioremediation as an effective method to clean up hydrocarbon spills in the northern latitudes

  11. Distribution and air-sea exchange of current-use pesticides (CUPs) from East Asia to the high Arctic Ocean.

    Science.gov (United States)

    Zhong, Guangcai; Xie, Zhiyong; Cai, Minghong; Möller, Axel; Sturm, Renate; Tang, Jianhui; Zhang, Gan; He, Jianfeng; Ebinghaus, Ralf

    2012-01-03

    Surface seawater and marine boundary layer air samples were collected on the ice-breaker R/V Xuelong (Snow Dragon) from the East China Sea to the high Arctic (33.23-84.5° N) in July to September 2010 and have been analyzed for six current-use pesticides (CUPs): trifluralin, endosulfan, chlorothalonil, chlorpyrifos, dacthal, and dicofol. In all oceanic air samples, the six CUPs were detected, showing highest level (>100 pg/m(3)) in the Sea of Japan. Gaseous CUPs basically decreased from East Asia (between 36.6 and 45.1° N) toward Bering and Chukchi Seas. The dissolved CUPs in ocean water ranged widely from air. Trifluralin in seawater was relatively high in the Sea of Japan (35.2° N) and evenly distributed between 36.9 and 72.5° N, but it remained below the detection limit at the highest northern latitudes in Chukchi Sea. In contrast with other CUPs, concentrations of chlorothalonil and dacthal were more abundant in Chukchi Sea and in East Asia. The air-sea gas exchange of CUPs was generally dominated by net deposition. Latitudinal trends of fugacity ratios of α-endosulfan, chlorothalonil, and dacthal showed stronger deposition of these compounds in East Asia than in Chukchi Sea, while trifluralin showed stronger deposition in Chukchi Sea (-455 ± 245 pg/m(2)/day) than in the North Pacific (-241 ± 158 pg/m(2)/day). Air-sea gas exchange of chlorpyrifos varied from net volatilizaiton in East Asia (<40° N) to equilibrium or net deposition in the North Pacific and the Arctic.

  12. Application of Terrestrial Ecosystem Monitoring under the CAFF Circumpolar Biodiversity Monitoring Program: Designing and Implementing Terrestrial Monitoring to Establish the Canadian High Arctic Research Station as a Flagship Arctic Environmental Monitoring Site

    Science.gov (United States)

    McLennan, D.; Kehler, D.

    2016-12-01

    The Canadian High Arctic Research Station (CHARS) is scheduled for completion in July 2017 and is the northern science component of Polar Knowledge Canada (POLAR). A mandated goal for POLAR is to establish the adjacent Experimental and Reference Area (ERA) as an Arctic Flagship monitoring site that will track change in Arctic terrestrial, freshwater and marine ecosystems. Situated in the community of Cambridge Bay, CHARS provides the opportunity to draw on the Indigenous Knowledge of local residents to help design and conduct the monitoring, and to operate 12 months a year. Monitoring at CHARS will be linked to networks nationally and internationally, and is being designed so that change in key indicators can be understood in terms of drivers and processes, modeled and scaled up regionally, and used to predict important changes in critical indicators. As a partner in the Circumpolar Biodiversity Monitoring Program (CBMP), the monitoring design for terrestrial ecosystems follows approaches outlined by the CBMP Terrestrial Expert Monitoring Group, who have listed key monitoring questions and identified a list of important Focal Ecosystem Components (FECs). To link drivers to FECs we are proposing a multi-scaled approach: 1) an Intensive Monitoring Area to establish replicated monitoring plots that track change in snow depth and condition, active layer depth, soil temperature, soil moisture, and soil solution chemistry that are spatially and temporally linked to changes in microbiological activity, CO2/CH4 net ecosystem flux, vegetation relative frequency, species composition, growth and foliar nutrient concentration, arthropod abundance, lemming abundance and health, and shorebird/songbird abundance and productivity. 2) These intensive observations are supported by watershed scale measures that will monitor, during the growing season, lemming winter nest abundance, songbird, shorebird and waterfowl staging and nesting, and other observations; in the winter we will

  13. Arctic bioremediation

    International Nuclear Information System (INIS)

    Liddell, B.V.; Smallbeck, D.R.; Ramert, P.C.

    1991-01-01

    Cleanup of oil and diesel spills on gravel pads in the Arctic has typically been accomplished by utilizing a water flushing technique to remove the gross contamination or excavating the spill area and placing the material into a lined pit, or a combination of both. This paper discusses the potential to utilize bioremediation as an effective method to clean up hydrocarbon spills in the northern latitudes. Discussed are the results of a laboratory bioremediation study which simulated microbial degradation of hydrocarbon under arctic conditions

  14. Cytological and ultrastructural preservation in Eocene Metasequoia leaves from the Canadian High Arctic.

    Science.gov (United States)

    Schoenhut, Karimah; Vann, David R; Lepage, Ben A

    2004-06-01

    The ultrastructural examination by transmission electron microscopy of 45-million-year-old mummified leaves of Metasequoia extracted from the Upper Coal member of the Buchanan Lake Formation in Napartulik on Axel Heiberg Island revealed the preservation of intact chloroplasts and chloroplast components. Abundant tanniferous cell inclusions may indicate that the 3-mo period of constant daylight during the Artic summer induced high concentrations of tannins in the leaf tissues, which may have arrested microbial degradation of the litter. Quantified differences in the extent of chloroplast preservation through a vertical section of the lignite suggest that short-term shifts in the depositional environment took place, perhaps influencing the exposure of the leaf tissues to conditions that would either promote or inhibit decomposition.

  15. Extremely high frequency RF effects on electronics.

    Energy Technology Data Exchange (ETDEWEB)

    Loubriel, Guillermo Manuel; Vigliano, David; Coleman, Phillip Dale; Williams, Jeffery Thomas; Wouters, Gregg A.; Bacon, Larry Donald; Mar, Alan

    2012-01-01

    The objective of this work was to understand the fundamental physics of extremely high frequency RF effects on electronics. To accomplish this objective, we produced models, conducted simulations, and performed measurements to identify the mechanisms of effects as frequency increases into the millimeter-wave regime. Our purpose was to answer the questions, 'What are the tradeoffs between coupling, transmission losses, and device responses as frequency increases?', and, 'How high in frequency do effects on electronic systems continue to occur?' Using full wave electromagnetics codes and a transmission-line/circuit code, we investigated how extremely high-frequency RF propagates on wires and printed circuit board traces. We investigated both field-to-wire coupling and direct illumination of printed circuit boards to determine the significant mechanisms for inducing currents at device terminals. We measured coupling to wires and attenuation along wires for comparison to the simulations, looking at plane-wave coupling as it launches modes onto single and multiconductor structures. We simulated the response of discrete and integrated circuit semiconductor devices to those high-frequency currents and voltages, using SGFramework, the open-source General-purpose Semiconductor Simulator (gss), and Sandia's Charon semiconductor device physics codes. This report documents our findings.

  16. Diversity and distribution of lichen-associated fungi in the Ny-Ålesund Region (Svalbard, High Arctic) as revealed by 454 pyrosequencing

    Science.gov (United States)

    Zhang, Tao; Wei, Xin-Li; Zhang, Yu-Qin; Liu, Hong-Yu; Yu, Li-Yan

    2015-01-01

    This study assessed the diversity and distribution of fungal communities associated with seven lichen species in the Ny-Ålesund Region (Svalbard, High Arctic) using Roche 454 pyrosequencing with fungal-specific primers targeting the internal transcribed spacer (ITS) region of the ribosomal rRNA gene. Lichen-associated fungal communities showed high diversity, with a total of 42,259 reads belonging to 370 operational taxonomic units (OTUs) being found. Of these OTUs, 294 belonged to Ascomycota, 54 to Basidiomycota, 2 to Zygomycota, and 20 to unknown fungi. Leotiomycetes, Dothideomycetes, and Eurotiomycetes were the major classes, whereas the dominant orders were Helotiales, Capnodiales, and Chaetothyriales. Interestingly, most fungal OTUs were closely related to fungi from various habitats (e.g., soil, rock, plant tissues) in the Arctic, Antarctic and alpine regions, which suggests that living in association with lichen thalli may be a transient stage of life cycle for these fungi and that long-distance dispersal may be important to the fungi in the Arctic. In addition, host-related factors shaped the lichen-associated fungal communities in this region. Taken together, these results suggest that lichens thalli act as reservoirs of diverse fungi from various niches, which may improve our understanding of fungal evolution and ecology in the Arctic. PMID:26463847

  17. Diversity and distribution of lichen-associated fungi in the Ny-Ålesund Region (Svalbard, High Arctic) as revealed by 454 pyrosequencing.

    Science.gov (United States)

    Zhang, Tao; Wei, Xin-Li; Zhang, Yu-Qin; Liu, Hong-Yu; Yu, Li-Yan

    2015-10-14

    This study assessed the diversity and distribution of fungal communities associated with seven lichen species in the Ny-Ålesund Region (Svalbard, High Arctic) using Roche 454 pyrosequencing with fungal-specific primers targeting the internal transcribed spacer (ITS) region of the ribosomal rRNA gene. Lichen-associated fungal communities showed high diversity, with a total of 42,259 reads belonging to 370 operational taxonomic units (OTUs) being found. Of these OTUs, 294 belonged to Ascomycota, 54 to Basidiomycota, 2 to Zygomycota, and 20 to unknown fungi. Leotiomycetes, Dothideomycetes, and Eurotiomycetes were the major classes, whereas the dominant orders were Helotiales, Capnodiales, and Chaetothyriales. Interestingly, most fungal OTUs were closely related to fungi from various habitats (e.g., soil, rock, plant tissues) in the Arctic, Antarctic and alpine regions, which suggests that living in association with lichen thalli may be a transient stage of life cycle for these fungi and that long-distance dispersal may be important to the fungi in the Arctic. In addition, host-related factors shaped the lichen-associated fungal communities in this region. Taken together, these results suggest that lichens thalli act as reservoirs of diverse fungi from various niches, which may improve our understanding of fungal evolution and ecology in the Arctic.

  18. High-intensity-laser-electron scattering

    International Nuclear Information System (INIS)

    Meyerhofer, D.D.

    1997-01-01

    In the field of an intense laser, photon-electron scattering becomes nonlinear when the oscillatory energy of the electron approaches its rest mass. The electron wave function is dressed by the field with a concomitant increase in the effective electron mass. When the photon energy in the electron rest frame is comparable to the electron rest mass, multiphoton Compton scattering occurs. When the photon energy is significantly lower than the electron rest mass, the electron acquires momentum from the photon field and emits harmonics. This paper reviews nonlinear photon-electron scattering processes and results from two recent experiments where they have been observed

  19. Evidence of recent changes in the ice regime of lakes in the Canadian High Arctic from spaceborne satellite observations

    Science.gov (United States)

    Surdu, Cristina M.; Duguay, Claude R.; Fernández Prieto, Diego

    2016-05-01

    Arctic lakes, through their ice cover phenology, are a key indicator of climatic changes that the high-latitude environment is experiencing. In the case of lakes in the Canadian Arctic Archipelago (CAA), many of which are ice covered more than 10 months per year, warmer temperatures could result in ice regime shifts. Within the dominant polar-desert environment, small local warmer areas have been identified. These relatively small regions - polar oases - with longer growing seasons and greater biological productivity and diversity are secluded from the surrounding barren polar desert. The ice regimes of 11 lakes located in both polar-desert and polar-oasis environments, with surface areas between 4 and 542 km2, many of unknown bathymetry, were documented. In order to investigate the response of ice cover of lakes in the CAA to climate conditions during recent years, a 15-year time series (1997-2011) of RADARSAT-1/2 ScanSAR Wide Swath, ASAR Wide Swath, and Landsat acquisitions were analyzed. Results show that melt onset occurred earlier for all observed lakes. With the exception of Lower Murray Lake, all lakes experienced earlier summer ice minimum and water-clear-of-ice (WCI) dates, with greater changes being observed for polar-oasis lakes (9-24 days earlier WCI dates for lakes located in polar oases and 2-20 days earlier WCI dates for polar-desert lakes). Additionally, results suggest that some lakes may be transitioning from a perennial/multiyear to a seasonal ice regime, with only a few lakes maintaining a multiyear ice cover on occasional years. Aside Lake Hazen and Murray Lakes, which preserved their ice cover during the summer of 2009, no residual ice was observed on any of the other lakes from 2007 to 2011.

  20. Sex- and habitat-specific responses of a high arctic willow, Salix arctica, to experimental climate change

    Energy Technology Data Exchange (ETDEWEB)

    Jones, M.H.; Macdonald, S.E. [Univ. of Alberta, Dept. of Renewable Resources, Edmonton, AB (Canada); Henry, G.H.R. [Univ. of British Columbia, Dept. of Geography, Vancouver, BC (Canada)

    1999-10-01

    Dioecious plant species and those occupying diverse habitats may present special analytical problems to researchers examining effects of climate change. Here we report the results from two complementary studies designed to determine the importance of sex and habitat on gas exchange and growth of male and female individuals of a dioecious, circumpolar willow, Salix arctica, in the Canadian High Arctic. In field studies, male and female willows from dry and wet habitats were subjected to passively enhanced summer temperature ({approx} to 1.3 deg C) using small open-top chambers over three years. Peak season gas exchange varied significantly by willow sex and habitat. Overall net assimilation was higher in the dry habitat than in the wet, and higher in females than in males. In the dry habitat, net assimilation of females was enhanced by experimental warming, but decreased in males. In the wet habitat, net assimilation of females was substantially depressed by experimental warming, while males showed an inconsistent response. Development and growth of male and female catkins were enhanced by elevated temperature more than leaf fascicles, but leaf fascicle development and growth varied more between the two habitats, particularly in males. In a controlled environment study, male and female willows from these same wet and dry habitats were grown in a 2x2 factorial experiment including 1 x or 2 x ambient [CO{sub 2}] and 5 or 12 deg. C. The sexes responded very differently to the experimental treatments, but we found no effect of original habitat. Net assimilation in males was affected by the interaction of temperature and CO{sub 2}, but in females by CO{sub 2} only. Our results demonstrate (a) significant intraspecific and intersexual differences in arctic willow physiology and growth, (b) that these differences are affected by environmental conditions expected to accompany global climate change, and (c) that sex- and habitat-specific responses should be explicitly

  1. A high-resolution Holocene speleothem record from NE Romania: the nexus of Arctic and North Atlantic atmospheric circulations

    Science.gov (United States)

    Constantin, S.; Pourmand, A.; Moldovan, O.; Sharifi, A.; Mehterian, S.; Swart, P. K.

    2017-12-01

    The Romanian Carpathians act as a geomorphological barrier between different atmospheric circulation systems over Central and Eastern Europe; the NW of Romania lies under the remote influence of the North Atlantic oscillation, while the NE is influenced by the Arctic climate. In NW Romania, previous stable isotope studies of speleothems have not yielded a clear account of abrupt climate oscillations during the Holocene. Here we present results from a stalagmite collected from the Tauşoare Cave, located in NE Carpathians. The chronology of stalagmite T141 is based on 15 high-precision Th/U dates ranging between 32 and 1.1 ka with a continuous growth between 13.3 and 1.1 ka. The portion of the record within the Holocene was analyzed for δ18O and δ13C at a resolution ranging between 15 to 200 years/sample. The resulting δ18O record captures the Younger Dryas (YD) event centered at 12.9 ka, with δ18O values about 4 ‰ more depleted than those corresponding to the Holocene Climatic Optimum. The 8.2 ka event appears to be also captured in the record, although less prominent. The T141 isotope record is significantly different when compared to coeval records measured in speleothems from NW Carpathians, which do not exhibit marked changes during the YD or 8.2 ka events. This is likely due to the contrasting effect of temperature and atmospheric transport on δ18O signal in NW Romania. Within a distance of 200 km to the east, on the eastern flank of the Carpathian range, the δ18O signal of the Arctic circulation appears to be more prominent and clearly exhibits a positive relationship with temperature changes.

  2. Electronics for very high rate tracking detectors

    International Nuclear Information System (INIS)

    Williams, H.H.; Dressnandt, N.; Ekenberg, T.; Gerds, E.J.; Newcomer, F.M.; Tedja, S.; Van Berg, R.; Van der Speigel, J.

    1995-01-01

    Results are presented on a system of electronics designed for very high rate tracking detectors at the SSC and LHC. The primary goal was a system for signal detection, time measurement, and readout for the straw tracker for SDC. An integrated circuit incorporating eight channels of amplifier-shaper-discriminator (including detector tail cancellation), and two different integrated circuits for time measurement are described. The performance of tracking measurements up to counting rates of 8 MHz per wire is reported, as well as preliminary results from a baseline restoration circuit. (orig.)

  3. Current knowledge of the Tardigrada of Svalbard with the first records of water bears from Nordaustlandet (High Arctic

    Directory of Open Access Journals (Sweden)

    Krzysztof Zawierucha

    2013-11-01

    Full Text Available The first investigations of the tardigrades of Svalbard took place in the early 20th century and 30 papers on the subject have been published to date. In this article, we summarize available information on the distribution of tardigrades in this Arctic archipelago with remarks on the dubious species and records. Additionally, we examined 28 new moss, lichen and soil samples collected from the islands of Nordaustlandet, Edgeøya and Prins Karls Forland. These samples yielded 324 specimens, 15 exuvia and 132 free-laid eggs belonging to 16 limnoterrestrial species (Heterotardigrada and Eutardigrada. These include five first records of water bears from Nordaustlandet, eight new records for Edgeøya and four for Prince Karls Forland. The most dense population of tardigrades was found in a sample with 253 specimens/10 g of dry material and the least dense population in a sample with three specimens/10 g of dry material. The most frequently recorded species in samples collected in this study were Testechiniscus spitsbergensis Scourfield, 1897, Macrobiotus harmsworthi harmsworthi Murray, 1907, and M. islandicus islandicus Richters, 1904. This article also provides the first ever scanning electron microscope photomicrographs of Tenuibiotus voronkovi Tumanov, 2007.

  4. Technical report of electronics shop characteristics of high speed electronics component, (1)

    International Nuclear Information System (INIS)

    Watanabe, Shin-ichi; Shiino, Kazuo.

    1975-01-01

    We must develop electronics circuits for high speed signals. The electronics components of the circuits make use of the special components. This report treats a pulse response of the electronics components (i.e. coaxial cable, connector, resistor, capacitor, diode, transistor) for high speed electronics. The results of this report was already applied constructions of high speed electronics circuits and experimental equipments of the High Energy Physics Division. (auth.)

  5. Shielding for high energy, high intensity electron accelerator installation

    International Nuclear Information System (INIS)

    Warawas, C.; Chongkum, S.

    1997-03-01

    The utilization of electron accelerators (eBA) is gradually increased in Thailand. For instance, a 30-40 MeV eBA are used for tumor and cancer therapy in the hospitals, and a high current eBA in for gemstone colonization. In the near future, an application of eBA in industries will be grown up in a few directions, e.g., flue gases treatment from the coal fire-power plants, plastic processing, rubber vulcanization and food preservation. It is the major roles of Office of Atomic Energy for Peace (OAEP) to promote the peaceful uses of nuclear energy and to regulate the public safety and protection of the environment. By taking into account of radiation safety aspect, high energy electrons are not only harmful to human bodies, but the radioactive nuclides can be occurred. This report presents a literature review by following the National Committee on Radiation Protection and Measurements (NCRP) report No.31. This reviews for parametric calculation and shielding design of the high energy (up to 100 MeV), high intensity electron accelerator installation

  6. Electron Linacs for High Energy Physics

    International Nuclear Information System (INIS)

    Wilson, Perry B.

    2011-01-01

    The purpose of this article is to introduce some of the basic physical principles underlying the operation of electron linear accelerators (electron linacs). Electron linacs have applications ranging from linacs with an energy of a few MeV, such that the electrons are approximately relativistic, to future electron-positron linear colliders having a collision energy in the several-TeV energy range. For the most part, only the main accelerating linac is treated in this article.

  7. Comparison of elastic-viscous-plastic and viscous-plastic dynamics models using a high resolution Arctic sea ice model

    Energy Technology Data Exchange (ETDEWEB)

    Hunke, E.C. [Los Alamos National Lab., NM (United States); Zhang, Y. [Naval Postgraduate School, Monterey, CA (United States)

    1997-12-31

    A nonlinear viscous-plastic (VP) rheology proposed by Hibler (1979) has been demonstrated to be the most suitable of the rheologies commonly used for modeling sea ice dynamics. However, the presence of a huge range of effective viscosities hinders numerical implementations of this model, particularly on high resolution grids or when the ice model is coupled to an ocean or atmosphere model. Hunke and Dukowicz (1997) have modified the VP model by including elastic waves as a numerical regularization in the case of zero strain rate. This modification (EVP) allows an efficient, fully explicit discretization that adapts well to parallel architectures. The authors present a comparison of EVP and VP dynamics model results from two 5-year simulations of Arctic sea ice, obtained with a high resolution sea ice model. The purpose of the comparison is to determine how differently the two dynamics models behave, and to decide whether the elastic-viscous-plastic model is preferable for high resolution climate simulations, considering its high efficiency in parallel computation. Results from the first year of this experiment (1990) are discussed in detail in Hunke and Zhang (1997).

  8. Arctic Islands LNG

    Energy Technology Data Exchange (ETDEWEB)

    Hindle, W.

    1977-01-01

    Trans-Canada Pipe Lines Ltd. made a feasibility study of transporting LNG from the High Arctic Islands to a St. Lawrence River Terminal by means of a specially designed and built 125,000 cu m or 165,000 cu m icebreaking LNG tanker. Studies were made of the climatology and of ice conditions, using available statistical data as well as direct surveys in 1974, 1975, and 1976. For on-schedule and unimpeded (unescorted) passage of the LNG carriers at all times of the year, special navigation and communications systems can be made available. Available icebreaking experience, charting for the proposed tanker routes, and tide tables for the Canadian Arctic were surveyed. Preliminary design of a proposed Arctic LNG icebreaker tanker, including containment system, reliquefaction of boiloff, speed, power, number of trips for 345 day/yr operation, and liquefaction and regasification facilities are discussed. The use of a minimum of three Arctic Class 10 ships would enable delivery of volumes of natural gas averaging 11.3 million cu m/day over a period of a year to Canadian markets. The concept appears to be technically feasible with existing basic technology.

  9. Record-low primary productivity and high plant damage in the Nordic Arctic Region in 2012 caused by multiple weather events and pest outbreaks

    International Nuclear Information System (INIS)

    Bjerke, Jarle W; Jepsen, Jane U; Lovibond, Sarah; Tømmervik, Hans; Rune Karlsen, Stein; Arild Høgda, Kjell; Malnes, Eirik; Vikhamar-Schuler, Dagrun

    2014-01-01

    The release of cold temperature constraints on photosynthesis has led to increased productivity (greening) in significant parts (32–39%) of the Arctic, but much of the Arctic shows stable (57–64%) or reduced productivity (browning, <4%). Summer drought and wildfires are the best-documented drivers causing browning of continental areas, but factors dampening the greening effect of more maritime regions have remained elusive. Here we show how multiple anomalous weather events severely affected the terrestrial productivity during one water year (October 2011–September 2012) in a maritime region north of the Arctic Circle, the Nordic Arctic Region, and contributed to the lowest mean vegetation greenness (normalized difference vegetation index) recorded this century. Procedures for field data sampling were designed during or shortly after the events in order to assess both the variability in effects and the maximum effects of the stressors. Outbreaks of insect and fungal pests also contributed to low greenness. Vegetation greenness in 2012 was 6.8% lower than the 2000–11 average and 58% lower in the worst affected areas that were under multiple stressors. These results indicate the importance of events (some being mostly neglected in climate change effect studies and monitoring) for primary productivity in a high-latitude maritime region, and highlight the importance of monitoring plant damage in the field and including frequencies of stress events in models of carbon economy and ecosystem change in the Arctic. Fourteen weather events and anomalies and 32 hypothesized impacts on plant productivity are summarized as an aid for directing future research. (letter)

  10. The Arctic Circle

    Science.gov (United States)

    McDonald, Siobhan

    2016-04-01

    My name is Siobhan McDonald. I am a visual artist living and working in Dublin. My studio is based in The School of Science at University College Dublin where I was Artist in Residence 2013-2015. A fascination with time and the changeable nature of landmass has led to ongoing conversations with scientists and research institutions across the interweaving disciplines of botany, biology and geology. I am developing a body of work following a recent research trip to the North Pole where I studied the disappearing landscape of the Arctic. Prompted by my experience of the Arctic shelf receding, this new work addresses issues of the instability of the earth's materiality. The work is grounded in an investigation of material processes, exploring the dynamic forces that transform matter and energy. This project combines art and science in a fascinating exploration of one of the Earth's last relatively untouched wilderness areas - the High Arctic to bring audiences on journeys to both real and artistically re-imagined Arctic spaces. CRYSTALLINE'S pivotal process is collaboration: with The European Space Agency; curator Helen Carey; palaeontologist Prof. Jenny McElwain, UCD; and with composer Irene Buckley. CRYSTALLINE explores our desire to make corporeal contact with geological phenomena in Polar Regions. From January 2016, in my collaboration with Jenny McElwain, I will focus on the study of plants and atmospheres from the Arctic regions as far back as 400 million years ago, to explore the essential 'nature' that, invisible to the eye, acts as imaginary portholes into other times. This work will be informed by my arctic tracings of sounds and images recorded in the glaciers of this disappearing frozen landscape. In doing so, the urgencies around the tipping of natural balances in this fragile region will be revealed. The final work will emerge from my forthcoming residency at the ESA in spring 2016. Here I will conduct a series of workshops in ESA Madrid to work with

  11. The alien terrestrial invertebrate fauna of the High Arctic archipelago of Svalbard: potential implications for the native flora and fauna

    OpenAIRE

    Stephen J. Coulson

    2015-01-01

    Experience from the Antarctic indicates that the establishment of alien species may have significant negative effects on native flora and fauna in polar regions and is considered to be amongst the greatest threats to biodiversity. But, there have been few similar studies from the Arctic. Although the terrestrial invertebrate inventory of the Svalbard Archipelago is amongst the most complete for any region of the Arctic, no consideration has yet been made of alien terrestrial invertebrate spec...

  12. STANFORD: Highly polarized SLC electron beams

    International Nuclear Information System (INIS)

    Anon.

    1993-01-01

    Full text: Using specialized photocathodes made with 'strained' gallium arsenide, physicists at the Stanford Linear Accelerator Center (SLAC) have generated electron beams with polarizations in excess of 60 percent a year ahead of schedule. Together with recent luminosity increases, this breakthrough will have a major impact on the physics output of the Stanford Linear Collider (SLC). Beam polarization was almost tripled using photocathodes in which a gallium arsenide layer was grown epitaxially over a substrate of gallium arsenide phosphide. The mismatch between these two layers deforms the crystal structure and removes a degeneracy in the valence band structure, permitting selective optical pumping of one unique spin state. Whereas conventional gallium arsenide photocathodes are limited to 50 percent polarization because of this degeneracy (and realistic cathodes fall substantially below this theoretical limit), such strained crystal lattices have the potential to yield polarizations close to 100 percent. Polarization enhancement with strained lattices was first demonstrated in 1991 by a SLAC/Wisconsin/ Berkeley group (May 1991, page 6) with a 71 percent polarization in a laboratory experiment. More recently this group has achieved polarization in excess of 90 percent, reported last November at the Nagoya Spin Symposium. (In a complementary development, a Japanese KEK/ Nagoya/KEK obtains polarized beams using a 'superlattice' - May 1991, page 4.) The 1993 SLC run, the strained gallium arsenide photocathode technique's debut in an operating particle accelerator, has proved to be a resounding, unqualified success - as have physics experiments on the Z particles produced by the highly polarized beam. A conservative approach was called for, due to concerns about possible charge saturation effects. A relatively thick (0.3 micron) gallium arsenide layer was used for the photocathode in the SLC polarized electron source. With a titanium

  13. Radioactive contamination in the Arctic - Present situation and future challenges

    International Nuclear Information System (INIS)

    Strand, P.

    2002-01-01

    There is currently a focus on radioactivity and the Arctic region. The reason for this is the high number of nuclear sources in parts of the Arctic and the vulnerability of Arctic systems to radioactive contamination. The Arctic environment is also perceived as a wilderness and the need for the protection of this wilderness against contamination is great. In 1991, the International Arctic Environmental Protection Strategy (IAEPS) was launched and the Arctic Monitoring and Assessment Programme (AMAP) established. AMAP is undertaking an assessment of the radioactive contamination of the Arctic and its radiological consequences. This paper summarises some of current knowledge about sources of radioactive contamination, vulnerability, exposure of man, and potential sources for radioactive contamination within Arctic and some views on the future needs for work concerning radioactivity in Arctic. (author)

  14. Sanitation methods using high energy electron beams

    International Nuclear Information System (INIS)

    Levaillant, C.; Gallien, C.L.

    1979-01-01

    Short recycling of waste water and the use of liquid or dehydrated sludge as natural manure for agriculture or animal supplement feed is of great economical and ecological interest. It implies strong biological and chemical disinfection. Ionizing radiations produced by radioactive elements or linear accelerators can be used as a complement of conventional methods in the treatment of liquid and solid waste. An experiment conducted with high-energy electron-beam linear accelerators is presented. Degradation of undesirable metabolites in water occurs for a dose of 50 kRad. Undesirable seeds present in sludge are destroyed with a 200 kRad dose. A 300 kRad dose is sufficient for parasitic and bacterial disinfection (DL 90). Destruction of polio virus (DL 90) is obtained for 400 kRad. Higher doses (1000 to 2000 kRad) produce mineralization of toxic organic mercury, reduce some chemical toxic pollutants present in sludge and improve flocculation. (author)

  15. Very-High-Brightness Picosecond Electron Source

    International Nuclear Information System (INIS)

    Bluem, H.

    2003-01-01

    Bright, RF photocathode electron guns are the source of choice for most high-performance research accelerator applications. Some of these applications are pushing the performance boundaries of the present state-of-the-art guns. Advanced Energy Systems is developing a novel photocathode RF gun that shows excellent promise for extending gun performance. Initial gun simulations with only a short booster accelerator easily break the benchmark emittance of one micron for 1 nC of bunch charge. The pulse length in these simulations is less than 2 ps. It is expected that with more detailed optimization studies, the performance can be further improved. The performance details of the gun will be presented. In addition, we will discuss the present design concept along with the status of the project

  16. Improved methods for high resolution electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, J.R.

    1987-04-01

    Existing methods of making support films for high resolution transmission electron microscopy are investigated and novel methods are developed. Existing methods of fabricating fenestrated, metal reinforced specimen supports (microgrids) are evaluated for their potential to reduce beam induced movement of monolamellar crystals of C/sub 44/H/sub 90/ paraffin supported on thin carbon films. Improved methods of producing hydrophobic carbon films by vacuum evaporation, and improved methods of depositing well ordered monolamellar paraffin crystals on carbon films are developed. A novel technique for vacuum evaporation of metals is described which is used to reinforce microgrids. A technique is also developed to bond thin carbon films to microgrids with a polymer bonding agent. Unique biochemical methods are described to accomplish site specific covalent modification of membrane proteins. Protocols are given which covalently convert the carboxy terminus of papain cleaved bacteriorhodopsin to a free thiol. 53 refs., 19 figs., 1 tab.

  17. Low temperature S(0) biomineralization at a supraglacial spring system in the Canadian High Arctic.

    Science.gov (United States)

    Gleeson, D F; Williamson, C; Grasby, S E; Pappalardo, R T; Spear, J R; Templeton, A S

    2011-07-01

    Elemental sulfur (S(0) ) is deposited each summer onto surface ice at Borup Fiord pass on Ellesmere Island, Canada, when high concentrations of aqueous H(2) S are discharged from a supraglacial spring system. 16S rRNA gene clone libraries generated from sulfur deposits were dominated by β-Proteobacteria, particularly Ralstonia sp. Sulfur-cycling micro-organisms such as Thiomicrospira sp., and ε-Proteobacteria such as Sulfuricurvales and Sulfurovumales spp. were also abundant. Concurrent cultivation experiments isolated psychrophilic, sulfide-oxidizing consortia, which produce S(0) in opposing gradients of Na(2) S and oxygen. 16S rRNA gene analyses of sulfur precipitated in gradient tubes show stable sulfur-biomineralizing consortia dominated by Marinobacter sp. in association with Shewanella, Loktanella, Rubrobacter, Flavobacterium, and Sphingomonas spp. Organisms closely related to cultivars appear in environmental 16S rRNA clone libraries; none currently known to oxidize sulfide. Once consortia were simplified to Marinobacter and Flavobacteria spp. through dilution-to-extinction and agar removal, sulfur biomineralization continued. Shewanella, Loktanella, Sphingomonas, and Devosia spp. were also isolated on heterotrophic media, but none produced S(0) alone when reintroduced to Na(2) S gradient tubes. Tubes inoculated with a Marinobacter and Shewanella spp. co-culture did show sulfur biomineralization, suggesting that Marinobacter may be the key sulfide oxidizer in laboratory experiments. Light, florescence and scanning electron microscopy of mineral aggregates produced in Marinobacter experiments revealed abundant cells, with filaments and sheaths variably mineralized with extracellular submicron sulfur grains; similar biomineralization was not observed in abiotic controls. Detailed characterization of mineral products associated with low temperature microbial sulfur-cycling may provide biosignatures relevant to future exploration of Europa and Mars. © 2011

  18. Genomics of Arctic cod

    Science.gov (United States)

    Wilson, Robert E.; Sage, George K.; Sonsthagen, Sarah A.; Gravley, Megan C.; Menning, Damian; Talbot, Sandra L.

    2017-01-01

    The Arctic cod (Boreogadus saida) is an abundant marine fish that plays a vital role in the marine food web. To better understand the population genetic structure and the role of natural selection acting on the maternally-inherited mitochondrial genome (mitogenome), a molecule often associated with adaptations to temperature, we analyzed genetic data collected from 11 biparentally-inherited nuclear microsatellite DNA loci and nucleotide sequence data from from the mitochondrial DNA (mtDNA) cytochrome b (cytb) gene and, for a subset of individuals, the entire mitogenome. In addition, due to potential of species misidentification with morphologically similar Polar cod (Arctogadus glacialis), we used ddRAD-Seq data to determine the level of divergence between species and identify species-specific markers. Based on the findings presented here, Arctic cod across the Pacific Arctic (Bering, Chukchi, and Beaufort Seas) comprise a single panmictic population with high genetic diversity compared to other gadids. High genetic diversity was indicated across all 13 protein-coding genes in the mitogenome. In addition, we found moderate levels of genetic diversity in the nuclear microsatellite loci, with highest diversity found in the Chukchi Sea. Our analyses of markers from both marker classes (nuclear microsatellite fragment data and mtDNA cytb sequence data) failed to uncover a signal of microgeographic genetic structure within Arctic cod across the three regions, within the Alaskan Beaufort Sea, or between near-shore or offshore habitats. Further, data from a subset of mitogenomes revealed no genetic differentiation between Bering, Chukchi, and Beaufort seas populations for Arctic cod, Saffron cod (Eleginus gracilis), or Walleye pollock (Gadus chalcogrammus). However, we uncovered significant differences in the distribution of microsatellite alleles between the southern Chukchi and central and eastern Beaufort Sea samples of Arctic cod. Finally, using ddRAD-Seq data, we

  19. High frequency free-electron laser results

    International Nuclear Information System (INIS)

    Boyer, K.; Brau, C.A.; Newman, B.E.; Stein, W.E.; Warren, R.W.; Winston, J.G.; Young, L.M.

    1983-01-01

    By looking at the free-electron laser as a particle accelerator working backwards, Morton realized that the techniques used to accelerate particles could be used to improve the performance of free-electron lasers. In particular, he predicted the capture of electrons in ''stable-phase'' regions, or ''buckets'' in the electron phase space, and proposed that by decelerating the buckets, the trapped electrons could be decelerated to extract significant amounts of their energy as optical radiation. In fact, since electrons not trapped in the stable regions are forever excluded from them--at least in the adiabatic approximation--displacement techniques could also be used to accelerate or decelerate electrons in a free-electron laser. This paper explains the principle behind ''phase-displacement'' acceleration and details an experiment carried out with a 20-MeV electron beam to test these predictions. Results obtained with a tapered-wiggler free-electron laser demonstrate the concepts proposed by Morton for enhanced efficiency. They show deceleration of electrons by as much as 7% and extraction of more than 3% of the total electron-beam energy as laser energy when the laser is operated as an amplifier. The experiment is presently being reconfigured to examine its performance as a laser oscillator

  20. Effects of increase glacier discharge on phytoplankton bloom dynamics and pelagic geochemistry in a high Arctic fjord

    KAUST Repository

    Calleja, Maria Ll.

    2017-07-26

    Arctic fjords experience extremely pronounced seasonal variability and spatial heterogeneity associated with changes in ice cover, glacial retreat and the intrusion of continental shelf’s adjacent water masses. Global warming intensifies natural environmental variability on these important systems, yet the regional and global effects of these processes are still poorly understood. In the present study, we examine seasonal and spatial variability in Kongsfjorden, on the western coast of Spitsbergen, Svalbard. We report hydrological, biological, and biogeochemical data collected during spring, summer, and fall 2012. Our results show a strong phytoplankton bloom with the highest chlorophyll a (Chla) levels ever reported in this area, peaking 15.5 µg/L during late May and completely dominated by large diatoms at the inner fjord, that may sustain both pelagic and benthic production under weakly stratified conditions at the glacier front. A progressively stronger stratification of the water column during summer and fall was shaped by the intrusion of warm Atlantic water (T > 3°C and Sal > 34.65) into the fjord at around 100 m depth, and by turbid freshwater plumes (T < 1°C and Sal < 34.65) at the surface due to glacier meltwater input. Biopolymeric carbon fractions and isotopic signatures of the particulate organic material (POM) revealed very fresh and labile material produced during the spring bloom (13C enriched, with values up to -22.7‰ at the highest Chl a peak, and high in carbohydrates and proteins content -up to 167 and 148 µg/L, respectively-), and a clear and strong continental signature of the POM present during late summer and fall (13C depleted, with values averaging -26.5 ‰, and high in lipid content –up to 92 µg/L-) when freshwater melting is accentuated. Our data evidence the importance of combining both physical (i.e. water mass dominance) and geochemical (i.e. characteristics of material released by glacier runoff) data in order to

  1. Effects of increase glacier discharge on phytoplankton bloom dynamics and pelagic geochemistry in a high Arctic fjord

    KAUST Repository

    Calleja, Maria Ll.; Kerhervé , P.; Bourgeois, S.; Kędra, M.; Leynaert, A.; Devred, E.; Babin, M.; Morata, N.

    2017-01-01

    Arctic fjords experience extremely pronounced seasonal variability and spatial heterogeneity associated with changes in ice cover, glacial retreat and the intrusion of continental shelf’s adjacent water masses. Global warming intensifies natural environmental variability on these important systems, yet the regional and global effects of these processes are still poorly understood. In the present study, we examine seasonal and spatial variability in Kongsfjorden, on the western coast of Spitsbergen, Svalbard. We report hydrological, biological, and biogeochemical data collected during spring, summer, and fall 2012. Our results show a strong phytoplankton bloom with the highest chlorophyll a (Chla) levels ever reported in this area, peaking 15.5 µg/L during late May and completely dominated by large diatoms at the inner fjord, that may sustain both pelagic and benthic production under weakly stratified conditions at the glacier front. A progressively stronger stratification of the water column during summer and fall was shaped by the intrusion of warm Atlantic water (T > 3°C and Sal > 34.65) into the fjord at around 100 m depth, and by turbid freshwater plumes (T < 1°C and Sal < 34.65) at the surface due to glacier meltwater input. Biopolymeric carbon fractions and isotopic signatures of the particulate organic material (POM) revealed very fresh and labile material produced during the spring bloom (13C enriched, with values up to -22.7‰ at the highest Chl a peak, and high in carbohydrates and proteins content -up to 167 and 148 µg/L, respectively-), and a clear and strong continental signature of the POM present during late summer and fall (13C depleted, with values averaging -26.5 ‰, and high in lipid content –up to 92 µg/L-) when freshwater melting is accentuated. Our data evidence the importance of combining both physical (i.e. water mass dominance) and geochemical (i.e. characteristics of material released by glacier runoff) data in order to

  2. Effects of increase glacier discharge on phytoplankton bloom dynamics and pelagic geochemistry in a high Arctic fjord

    Science.gov (United States)

    Calleja, Maria Ll.; Kerhervé, P.; Bourgeois, S.; Kędra, M.; Leynaert, A.; Devred, E.; Babin, M.; Morata, N.

    2017-12-01

    Arctic fjords experience extremely pronounced seasonal variability and spatial heterogeneity associated with changes in ice cover, glacial retreat and the intrusion of continental shelf's adjacent water masses. Global warming intensifies natural environmental variability on these important systems, yet the regional and global effects of these processes are still poorly understood. In the present study, we examine seasonal and spatial variability in Kongsfjorden, on the western coast of Spitsbergen, Svalbard. We report hydrological, biological, and biogeochemical data collected during spring, summer, and fall 2012. Our results show a strong phytoplankton bloom with the highest chlorophyll a (Chla) levels ever reported in this area, peaking 15.5 μg/L during late May and completely dominated by large diatoms at the inner fjord, that may sustain both pelagic and benthic production under weakly stratified conditions at the glacier front. A progressively stronger stratification of the water column during summer and fall was shaped by the intrusion of warm Atlantic water (T > 3 °C and Sal > 34.65) into the fjord at around 100 m depth, and by turbid freshwater plumes (T carbon fractions and isotopic signatures of the particulate organic material (POM) revealed very fresh and labile material produced during the spring bloom (13C enriched, with values up to -22.7‰ at the highest Chl a peak, and high in carbohydrates and proteins content - up to 167 and 148 μg/L, respectively-), and a clear and strong continental signature of the POM present during late summer and fall (13C depleted, with values averaging -26.5‰, and high in lipid content - up to 92 μg/L-) when freshwater melting is accentuated. Our data evidence the importance of combining both physical (i.e. water mass dominance) and geochemical (i.e. characteristics of material released by glacier runoff) data in order to understand the timing, intensity and characteristics of the phytoplankton bloom in

  3. Cool tadpoles from Arctic environments waste fewer nutrients - high gross growth efficiencies lead to low consumer-mediated nutrient recycling in the North.

    Science.gov (United States)

    Liess, Antonia; Guo, Junwen; Lind, Martin I; Rowe, Owen

    2015-11-01

    Endothermic organisms can adapt to short growing seasons, low temperatures and nutrient limitation by developing high growth rates and high gross growth efficiencies (GGEs). Animals with high GGEs are better at assimilating limiting nutrients and thus should recycle (or lose) fewer nutrients. Longer guts in relation to body mass may facilitate higher GGE under resource limitation. Within the context of ecological stoichiometry theory, this study combines ecology with evolution by relating latitudinal life-history adaptations in GGE, mediated by gut length, to its ecosystem consequences, such as consumer-mediated nutrient recycling. In common garden experiments, we raised Rana temporaria tadpoles from two regions (Arctic/Boreal) under two temperature regimes (18/23 °C) crossed with two food quality treatments (high/low-nitrogen content). We measured tadpole GGEs, total nutrient loss (excretion + egestion) rates and gut length during ontogeny. In order to maintain their elemental balance, tadpoles fed low-nitrogen (N) food had lower N excretion rates and higher total phosphorous (P) loss rates than tadpoles fed high-quality food. In accordance with expectations, Arctic tadpoles had higher GGEs and lower N loss rates than their low-latitude conspecifics, especially when fed low-N food, but only in ambient temperature treatments. Arctic tadpoles also had relatively longer guts than Boreal tadpoles during early development. That temperature and food quality interacted with tadpole region of origin in affecting tadpole GGEs, nutrient loss rates and relative gut length, suggests evolved adaptation to temperature and resource differences. With future climate change, mean annual temperatures will increase. Additionally, species and genotypes will migrate north. This will change the functioning of Boreal and Arctic ecosystems by affecting consumer-mediated nutrient recycling and thus affect nutrient dynamics in general. Our study shows that evolved latitudinal adaption can

  4. Deployment of a Fully-Automated Green Fluorescent Protein Imaging System in a High Arctic Autonomous Greenhouse

    Directory of Open Access Journals (Sweden)

    Alain Berinstain

    2013-03-01

    Full Text Available Higher plants are an integral part of strategies for sustained human presence in space. Space-based greenhouses have the potential to provide closed-loop recycling of oxygen, water and food. Plant monitoring systems with the capacity to remotely observe the condition of crops in real-time within these systems would permit operators to take immediate action to ensure optimum system yield and reliability. One such plant health monitoring technique involves the use of reporter genes driving fluorescent proteins as biological sensors of plant stress. In 2006 an initial prototype green fluorescent protein imager system was deployed at the Arthur Clarke Mars Greenhouse located in the Canadian High Arctic. This prototype demonstrated the advantageous of this biosensor technology and underscored the challenges in collecting and managing telemetric data from exigent environments. We present here the design and deployment of a second prototype imaging system deployed within and connected to the infrastructure of the Arthur Clarke Mars Greenhouse. This is the first imager to run autonomously for one year in the un-crewed greenhouse with command and control conducted through the greenhouse satellite control system. Images were saved locally in high resolution and sent telemetrically in low resolution. Imager hardware is described, including the custom designed LED growth light and fluorescent excitation light boards, filters, data acquisition and control system, and basic sensing and environmental control. Several critical lessons learned related to the hardware of small plant growth payloads are also elaborated.

  5. Deployment of a Fully-Automated Green Fluorescent Protein Imaging System in a High Arctic Autonomous Greenhouse

    Science.gov (United States)

    Abboud, Talal; Bamsey, Matthew; Paul, Anna-Lisa; Graham, Thomas; Braham, Stephen; Noumeir, Rita; Berinstain, Alain; Ferl, Robert

    2013-01-01

    Higher plants are an integral part of strategies for sustained human presence in space. Space-based greenhouses have the potential to provide closed-loop recycling of oxygen, water and food. Plant monitoring systems with the capacity to remotely observe the condition of crops in real-time within these systems would permit operators to take immediate action to ensure optimum system yield and reliability. One such plant health monitoring technique involves the use of reporter genes driving fluorescent proteins as biological sensors of plant stress. In 2006 an initial prototype green fluorescent protein imager system was deployed at the Arthur Clarke Mars Greenhouse located in the Canadian High Arctic. This prototype demonstrated the advantageous of this biosensor technology and underscored the challenges in collecting and managing telemetric data from exigent environments. We present here the design and deployment of a second prototype imaging system deployed within and connected to the infrastructure of the Arthur Clarke Mars Greenhouse. This is the first imager to run autonomously for one year in the un-crewed greenhouse with command and control conducted through the greenhouse satellite control system. Images were saved locally in high resolution and sent telemetrically in low resolution. Imager hardware is described, including the custom designed LED growth light and fluorescent excitation light boards, filters, data acquisition and control system, and basic sensing and environmental control. Several critical lessons learned related to the hardware of small plant growth payloads are also elaborated. PMID:23486220

  6. Magmatism and Eurekan deformation in the High Arctic Large Igneous Province: 40Ar–39Ar age of Kap Washington Group volcanics, North Greenland

    DEFF Research Database (Denmark)

    Tegner, Christian; Storey, Michael; Holm, Paul Martin

    2011-01-01

    The High Arctic Large Igneous Province is unusual on two counts: first, magmatism was prolonged and has been suggested to include an initial tholeiitic phase (130–80 Ma) and a second alkaline phase (85–60 Ma); second, it was subsequently deformed during the Eurekan Orogeny. New 40Ar–39Ar dating...... of alkaline volcanics from Kap Kane, part of the Kap Washington Group volcanics at the northern tip of Greenland, provides an emplacement age of 71.2±0.5 Ma obtained from amphibole in lapilli tuffs, and a thermal resetting age of 49–47 Ma obtained in feldspar and whole-rocks from trachyte flows. Patch...... in the Labrador Sea and the Baffin Bay, and to eastwards displacement of Greenland relative to North America. The alkaline suite, therefore, may be unrelated to the main tholeiitic phase of the High Arctic Large Igneous Province. The subsequent initiation of continental rifting and ensuing seafloor spreading...

  7. Tsunami in the Arctic

    Science.gov (United States)

    Kulikov, Evgueni; Medvedev, Igor; Ivaschenko, Alexey

    2017-04-01

    rate of 10-3 per year. Additional tsunami threat might arise from rare earthquake occurrences within the continental slope of deep-sea basin of the Arctic Ocean and near the coast of the continent, where high probability of triggering submarine landslides exists that can generate even more dangerous tsunamis than those of seismotectonic origin. The most reliable information about the manifestation of the tsunami in the Arctic is associated with submarine landslide Storegga located on the continental slope of the Norwegian Sea and collapsed 8,200 years ago. Traces of sediment left behind by the tsunami waves on the coast, show that the maximum vertical tsunami runup could reach 20 meters. Factors causing the potential tsunami thread of landslides in Russian Arctic are sedimentation processes that can be associated with the formation of the alluvial fans of the great Siberian rivers Ob, Yenisei and Lena.

  8. Freshwater Export from the Arctic Ocean and its Downstream Effect on Labrador Sea Deep Convection in a High-Resolution Numerical Model

    Science.gov (United States)

    2010-12-01

    Arctic has been observed in the northern Canadian Arctic Archipelago ( Bourke and McLaren 1992). There, thick multiyear ice of Arctic origin encounters...Affairs, 87(2), 63-77. 172 Bourke , R. H., and A. S. McLaren, 1992: Contour mapping of Arctic Basin ice draft and roughness parameters. J. Geophys

  9. High-resolution numerical simulation of summer wind field comparing WRF boundary-layer parametrizations over complex Arctic topography: case study from central Spitsbergen

    Czech Academy of Sciences Publication Activity Database

    Láska, K.; Chládová, Zuzana; Hošek, Jiří

    2017-01-01

    Roč. 26, č. 4 (2017), s. 391-408 ISSN 0941-2948 Institutional support: RVO:68378289 Keywords : surface wind field * model evaluation * topographic effect * circulation pattern * Svalbard Subject RIV: DG - Athmosphere Sciences, Meteorology OBOR OECD: Meteorology and atmospheric sciences Impact factor: 1.989, year: 2016 http://www.schweizerbart.de/papers/metz/detail/prepub/87659/High_resolution_numerical_simulation_of_summer_wind_field_comparing_WRF_boundary_layer_parametrizations_over_complex_Arctic_topography_case_study_from_central_Spitsbergen

  10. Zeolites - a high resolution electron microscopy study

    International Nuclear Information System (INIS)

    Alfredsson, V.

    1994-10-01

    High resolution transmission electron microscopy (HRTEM) has been used to investigate a number of zeolites (EMT, FAU, LTL, MFI and MOR) and a member of the mesoporous M41S family. The electron optical artefact, manifested as a dark spot in the projected centre of the large zeolite channels, caused by insufficient transfer of certain reflections in the objective lens has been explained. The artefact severely hinders observation of materials confined in the zeolite channels and cavities. It is shown how to circumvent the artefact problem and how to image confined materials in spite of disturbance caused by the artefact. Image processing by means of a Wiener filter has been applied for removal of the artefact. The detailed surface structure of FAU has been investigated. Comparison of experimental micrographs with images simulated using different surface models indicates that the surface can be terminated in different ways depending on synthesis methods. The dealuminated form of FAU (USY) is covered by an amorphous region. Platinum incorporated in FAU has a preponderance to aggregate in the (111) twin planes, probably due to a local difference in cage structure with more spacious cages. It is shown that platinum is intra-zeolitic as opposed to being located on the external surface of the zeolite crystal. This could be deduced from tomography of ultra-thin sections among observations. HRTEM studies of the mesoporous MCM-41 show that the pores have a hexagonal shape and also supports the mechanistic model proposed which involves a cooperative formation of a mesophase including the silicate species as well as the surfactant. 66 refs, 24 figs

  11. Differences in mercury bioaccumulation between polar bears (Ursus maritimus) from the Canadian high- and sub-Arctic.

    Science.gov (United States)

    St Louis, Vincent L; Derocher, Andrew E; Stirling, Ian; Graydon, Jennifer A; Lee, Caroline; Jocksch, Erin; Richardson, Evan; Ghorpade, Sarah; Kwan, Alvin K; Kirk, Jane L; Lehnherr, Igor; Swanson, Heidi K

    2011-07-15

    Polar bears (Ursus maritimus) are being impacted by climate change and increased exposure to pollutants throughout their northern circumpolar range. In this study, we quantified concentrations of total mercury (THg) in the hair of polar bears from Canadian high- (southern Beaufort Sea, SBS) and sub- (western Hudson Bay, WHB) Arctic populations. Concentrations of THg in polar bears from the SBS population (14.8 ± 6.6 μg g(-1)) were significantly higher than in polar bears from WHB (4.1 ± 1.0 μg g(-1)). On the basis of δ(15)N signatures in hair, in conjunction with published δ(15)N signatures in particulate organic matter and sediments, we estimated that the pelagic and benthic food webs in the SBS are ∼ 4.7 and ∼ 4.0 trophic levels long, whereas in WHB they are only ∼ 3.6 and ∼ 3.3 trophic levels long. Furthermore, the more depleted δ(13)C ratios in hair from SBS polar bears relative to those from WHB suggests that SBS polar bears feed on food webs that are relatively more pelagic (and longer), whereas polar bears from WHB feed on those that are relatively more benthic (and shorter). Food web length and structure accounted for ∼ 67% of the variation we found in THg concentrations among all polar bears across both populations. The regional difference in polar bear hair THg concentrations was also likely due to regional differences in water-column concentrations of methyl Hg (the toxic form of Hg that biomagnifies through food webs) available for bioaccumulation at the base of the food webs. For example, concentrations of methylated Hg at mid-depths in the marine water column of the northern Canadian Arctic Archipelago were 79.8 ± 37.3 pg L(-1), whereas, in HB, they averaged only 38.3 ± 16.6 pg L(-1). We conclude that a longer food web and higher pelagic concentrations of methylated Hg available to initiate bioaccumulation in the BS resulted in higher concentrations of THg in polar bears from the SBS region compared to those inhabiting the western

  12. Theoretical description of high-lying two-electrons states

    International Nuclear Information System (INIS)

    Greene, C.H.; Cavagnero, M.; Sadeghpour, H.R.

    1993-01-01

    Within the past two years, experiments on high-lying doubly-excited states in He and H- have shown spectra at energies near excited hydrogenic thresholds having principal quantum numbers in the range N=5--9. While they display some nontrivial complexities, the spectra are tremendously simpler than might be anticipated on the basis of independent electron models, in that only a small fraction of the total number of anticipated resonances are observed experimentally. Moreover, for principal quantum number N that are not too high, specifically N - , the resonance positions are described accurately by adiabatic calculations using hyperspherical coordinates and can be parametrized by a remarkably simple two-electron Rydberg formula. The observed propensity for excitation of only a small subset of the possible resonance states has been codified by several groups into approximate selection rules based on alternative (but apparently equivalent) classification schemes. Comparatively few attempts have been made at quantitative tests of the validity of these rules. The present review describes recent efforts to quantify their accuracy and limitations using R-matrix and quantum defect techniques, and Smith's delay-time matrix. Prospensity rules for exciting different degrees of freedom are found to differ greatly in their degree of validity

  13. Electron-electron interactions in graphene field-induced quantum dots in a high magnetic field

    DEFF Research Database (Denmark)

    Orlof, A.; Shylau, Artsem; Zozoulenko, I. V.

    2015-01-01

    We study the effect of electron-electron interaction in graphene quantum dots defined by an external electrostatic potential and a high magnetic field. To account for the electron-electron interaction, we use the Thomas-Fermi approximation and find that electron screening causes the formation...... of compressible strips in the potential profile and the electron density. We numerically solve the Dirac equations describing the electron dynamics in quantum dots, and we demonstrate that compressible strips lead to the appearance of plateaus in the electron energies as a function of the magnetic field. Finally...

  14. ELEC-2005: Electronics in High Energy Physics

    CERN Multimedia

    Monique Duval

    2004-01-01

    ELEC-2005 is a new course series on modern electronics, given by CERN physicists and engineers in the format of the successful ELEC-2002 course series, and within the framework of the 2005 Technical Training Programme. This comprehensive course series is designed for people who are not electronics specialists, for example physicists, engineers and technicians working at or visiting the laboratory, who use or will use electronics in their present or future activities, in particular in the context of the LHC accelerator and experiments. ELEC-2005 will composed of four Terms throughout the year: Winter Term: Introduction to electronics in HEP (January-February, 6 lectures) Spring Term: Integrated circuits and VLSI technology for physics (March, 6 lectures) Summer Term: System electronics for physics: Issues (May, 7 lectures) Winter Term: Electronics applications in HEP experiments (November-December, 10 lectures) Lectures within each Term will take place on Tuesdays and Thursdays, from 10:00 to 12:30. The...

  15. Early Triassic development of a foreland basin in the Canadian high Arctic: Implications for a Pangean Rim of Fire

    Science.gov (United States)

    Hadlari, Thomas; Dewing, Keith; Matthews, William A.; Alonso-Torres, Daniel; Midwinter, Derrick

    2018-06-01

    Following the amalgamation of Laurasia and Gondwana to form Pangea, some Triassic tectonic models show an encircling arc system called the "Pangean Rim of Fire". Here we show that the stratigraphy and Early Triassic detrital zircon provenance of the Sverdrup Basin in the Canadian Arctic is most consistent with deposition in a retro-arc foreland basin. Late Permian and Early Triassic volcanism was accompanied by relatively high rates of subsidence leading to a starved basin with volcanic input from a magmatic arc to the northwest. The mostly starved basin persisted through the Middle and Late Triassic with nearly continuous input of volcanic ash recorded as bentonites on the northwestern edge of the basin. In the latest Triassic it is interpreted that decreasing subsidence and a significant influx of sand-grade sediment when the arc was exhumed led to filling of the basin at the end of an orogenic cycle. Combined with other hints of Early Triassic arc activity along the western margin of Laurentia we propose that the Pangean Rim of Fire configuration spanned the entire Triassic. This proposed configuration represents the ring of external subduction zones that some models suggest are necessary for the breakup of supercontinents such as Pangea.

  16. Recent ice cap snowmelt in Russian High Arctic and anti-correlation with late summer sea ice extent

    International Nuclear Information System (INIS)

    Zhao, Meng; Ramage, Joan; Semmens, Kathryn; Obleitner, Friedrich

    2014-01-01

    Glacier surface melt dynamics throughout Novaya Zemlya (NovZ) and Severnaya Zemlya (SevZ) serve as a good indicator of ice mass ablation and regional climate change in the Russian High Arctic. Here we report trends of surface melt onset date (MOD) and total melt days (TMD) by combining multiple resolution-enhanced active and passive microwave satellite datasets and analyze the TMD correlations with local temperature and regional sea ice extent. The glacier surface snowpack on SevZ melted significantly earlier (−7.3 days/decade) from 1992 to 2012 and significantly longer (7.7 days/decade) from 1995 to 2011. NovZ experienced large interannual variability in MOD, but its annual mean TMD increased. The snowpack melt on NovZ is more sensitive to temperature fluctuations than SevZ in recent decades. After ruling out the regional temperature influence using partial correlation analysis, the TMD on both archipelagoes is statistically anti-correlated with regional late summer sea ice extent, linking land ice snowmelt dynamics to regional sea ice extent variations. (letter)

  17. Taxonomic and functional patterns of macrobenthic communities on a high-Arctic shelf: A case study from the Laptev Sea

    Science.gov (United States)

    Kokarev, V. N.; Vedenin, A. A.; Basin, A. B.; Azovsky, A. I.

    2017-11-01

    The studies of functional structure of high-Arctic Ecosystems are scarce. We used data on benthic macrofauna from 500-km latitudinal transect in the eastern Laptev Sea, from the Lena delta to the continental shelf break, to describe spatial patterns in species composition, taxonomic and functional structure in relation to environmental factors. Both taxonomy-based approach and Biological Trait analysis yielded similar results and showed general depth-related gradient in benthic diversity and composition. This congruence between taxonomical and functional dimensions of community organization suggests that the same environmental factors (primarily riverine input and regime of sedimentation) have similar effect on both community structure and functioning. BTA also revealed a distinct functional structure of stations situated at the Eastern Lena valley, with dominance of motile, burrowing sub-surface deposit-feeders and absence of sedentary tube-dwelling forms. The overall spatial distribution of benthic assemblages corresponds well to that described there in preceding decades, evidencing the long-term stability of bottom ecosystem. Strong linear relationship between species and traits diversity, however, indicates low functional redundancy, which potentially makes the ecosystem susceptible to a species loss or structural shifts.

  18. Turbulent fluxes of momentum and heat over land in the High-Arctic summer: the influence of observation techniques

    Directory of Open Access Journals (Sweden)

    Anna Sjöblom

    2014-06-01

    Full Text Available Different observation techniques for atmospheric turbulent fluxes of momentum and sensible heat were tested in a High-Arctic valley in Svalbard during two consecutive summers (June–August in 2010 and 2011. The gradient method (GM and the bulk method (BM have been compared to the more direct eddy covariance method (ECM in order to evaluate if relatively robust and cheap instrumentation with low power consumption can be used as a means to increase the number of observations, especially at remote locations where instruments need to be left unattended for extended periods. Such campaigns increase knowledge about the snow-free surface exchange processes, an area which is relatively little investigated compared to snow-covered ground. The GM agreed closely to the ECM, especially for momentum flux where the two methods agree within 5%. For sensible heat flux, the GM produces, on average, approximately 40% lower values for unstable stratification and 67% lower for stable stratification. However, this corresponds to only 20 and 12 W m−2, respectively. The BM, however, shows a greater scatter and larger differences for both parameters. In addition to testing these methods, radiation properties were measured and the surface albedo was found to increase through the summer, from approximately 0.1 to 0.2. The surface energy budget shows that the sensible heat flux is usually directed upwards for the whole summer, while the latent heat flux is upwards in June, but becomes downward in July and August.

  19. A summary of high-temperature electronics research and development

    International Nuclear Information System (INIS)

    Thome, F.V.; King, D.B.

    1991-01-01

    Current and future needs in automative, aircraft, space, military, and well logging industries require operation of electronics at higher temperatures than today's accepted limit of 395 K. Without the availability of high-temperature electronics, many systems must operate under derated conditions or must accept severe mass penalties required by coolant systems to maintain electronic temperatures below critical levels. This paper presents ongoing research and development in the electronics community to bring high-temperature electronics to commercial realization. Much of this work was recently reviewed at the First International High-Temperature Electronics Conference held 16--20 June 1991 in Albuquerque, New Mexico. 4 refs., 1 tab

  20. Deepened winter snow increases stem growth and alters stem δ13C and δ15N in evergreen dwarf shrub Cassiope tetragona in high-arctic Svalbard tundra

    DEFF Research Database (Denmark)

    Blok, Daan; Weijers, Stef; Welker, Jeffrey M

    2015-01-01

    Deeper winter snow is hypothesized to favor shrub growth and may partly explain the shrub expansion observed in many parts of the arctic during the last decades, potentially triggering biophysical feedbacks including regional warming and permafrost thawing. We experimentally tested the effects...... of winter snow depth on shrub growth and ecophysiology by measuring stem length and stem hydrogen ( δ2H), carbon ( δ13C), nitrogen ( δ15N) and oxygen ( δ18O) isotopic composition of the circumarctic evergreen dwarf shrub Cassiope tetragona growing in high-arctic Svalbard, Norway. Measurements were carried...... closely matched, snow depth did not change stem δ 2 H or δ 18 O, suggesting that water source usage by C. tetragona was unaltered. Instead, the deep insulating snowpack may have protected C. tetragona shrubs against frost damage, potentially compensating the detrimental effects of a shortened growing...

  1. Electronic phase separation and high temperature superconductors

    International Nuclear Information System (INIS)

    Kivelson, S.A.

    1994-01-01

    The authors review the extensive evidence from model calculations that neutral holes in an antiferromagnet separate into hole-rich and hole-poor phases. All known solvable limits of models of holes in a Heisenberg antiferromagnet exhibit this behavior. The authors show that when the phase separation is frustrated by the introduction of long-range Coulomb interactions, the typical consequence is either a modulated (charge density wave) state or a superconducting phase. The authors then review some of the strong experimental evidence supporting an electronically-driven phase separation of the holes in the cuprate superconductors and the related Ni oxides. Finally, the authors argue that frustrated phase separation in these materials can account for many of the anomalous normal state properties of the high temperature superconductors and provide the mechanism of superconductivity. In particular, it is shown that the T-linear resistivity of the normal state is a paraconductivity associated with a novel composite pairing, although the ordered superconducting state is more conventional

  2. Electronic properties of high Tc superconductors

    International Nuclear Information System (INIS)

    Rojo, A.G.

    1989-01-01

    Using analytical and numerical methods, the electronic properties of the copper-oxygen plane in the normal phase of high Tc superconductors are described. Using the slave-boson technique in the saddle point, a theory of the metal insulator transition which generalizes the notions of a Mott insulator to the case of more than a single band for those planes is presented. A phase-diagram is obtained in the parameter space and effective masses, optical gaps and metallization are calculated as a function of the number of carriers. Based on the experimental evidence, the theory permits classification of superconducting compounds as charge transfer insulators in the stoichiometric case. The insulator state is characterized by a non-zero optical gap and a divergent effective mass which corresponds to the breakage of a Fermi-liquid scheme. The results obtained are applicable to metal-transition-oxides whose behaviour has been traditionally controversial and it is concluded that it is necessary to broaden the meaning of a Mott insulator to the case of more than a single band to better understand them. Based on the ideas of group renormalization in a real space, a lattice approximation is presented, which allows: a) To complement the treatment of slave-bosons in phase diagrams and optical gaps; b) Identification of an attraction mechanism between carriers originating from purely repulsive interactions. Numerical calculations in small clusters show the existence of a pairing mechanism showing a superconducting instability from a charge transfer insulator. (Author) [es

  3. Arctic Shipping

    DEFF Research Database (Denmark)

    Hansen, Carsten Ørts; Grønsedt, Peter; Lindstrøm Graversen, Christian

    This report forms part of the ambitious CBS Maritime research initiative entitled “Competitive Challenges and Strategic Development Potential in Global Maritime Industries” which was launched with the generous support of the Danish Maritime Fund. The competitiveness initiative targets specific ma......, the latter aiming at developing key concepts and building up a basic industry knowledge base for further development of CBS Maritime research and teaching. This report attempts to map the opportunities and challenges for the maritime industry in an increasingly accessible Arctic Ocean...

  4. Electron clouds in high energy hadron accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Petrov, Fedor

    2013-08-29

    The formation of electron clouds in accelerators operating with positrons and positively charge ions is a well-known problem. Depending on the parameters of the beam the electron cloud manifests itself differently. In this thesis the electron cloud phenomenon is studied for the CERN Super Proton Synchrotron (SPS) and Large Hadron Collider (LHC) conditions, and for the heavy-ion synchrotron SIS-100 as a part of the FAIR complex in Darmstadt, Germany. Under the FAIR conditions the extensive use of slow extraction will be made. After the acceleration the beam will be debunched and continuously extracted to the experimental area. During this process, residual gas electrons can accumulate in the electric field of the beam. If this accumulation is not prevented, then at some point the beam can become unstable. Under the SPS and LHC conditions the beam is always bunched. The accumulation of electron cloud happens due to secondary electron emission. At the time when this thesis was being written the electron cloud was known to limit the maximum intensity of the two machines. During the operation with 25 ns bunch spacing, the electron cloud was causing significant beam quality deterioration. At moderate intensities below the instability threshold the electron cloud was responsible for the bunch energy loss. In the framework of this thesis it was found that the instability thresholds of the coasting beams with similar space charge tune shifts, emittances and energies are identical. First of their kind simulations of the effect of Coulomb collisions on electron cloud density in coasting beams were performed. It was found that for any hadron coasting beam one can choose vacuum conditions that will limit the accumulation of the electron cloud below the instability threshold. We call such conditions the ''good'' vacuum regime. In application to SIS-100 the design pressure 10{sup -12} mbar corresponds to the good vacuum regime. The transition to the bad vacuum

  5. High performance flexible electronics for biomedical devices.

    Science.gov (United States)

    Salvatore, Giovanni A; Munzenrieder, Niko; Zysset, Christoph; Kinkeldei, Thomas; Petti, Luisa; Troster, Gerhard

    2014-01-01

    Plastic electronics is soft, deformable and lightweight and it is suitable for the realization of devices which can form an intimate interface with the body, be implanted or integrated into textile for wearable and biomedical applications. Here, we present flexible electronics based on amorphous oxide semiconductors (a-IGZO) whose performance can achieve MHz frequency even when bent around hair. We developed an assembly technique to integrate complex electronic functionalities into textile while preserving the softness of the garment. All this and further developments can open up new opportunities in health monitoring, biotechnology and telemedicine.

  6. Electronic behavior of highly correlated metals

    International Nuclear Information System (INIS)

    Reich, A.

    1988-10-01

    This thesis addresses the question of the strongly interacting many-body problem: that is, systems where the interparticle correlations are so strong as to defy perturbative approaches. These subtle correlations occur in narrow band materials, such as the lanthanides and actinides, wherein the f-electrons are so localized that a variety of new phenomena, including intermediate-valence and heavy-fermionic behavior, may occur. As well, one has the alloying problem, where local interactions are paramount in determining the overall behavior. The technique employed in dealing with these systems is the Small Cluster method, wherein the full many-body Hamiltonian for a small grouping of atoms, coupled with periodic boundary conditions, is solved exactly. This is tantamount to solving a bulk crystal at the high points of symmetry in the Brillouin Zone. The mathematical overhead is further reduced by employing the full space group and spin symmetries. By its very nature, the Small Cluster method is well able to handle short-range interactions, as well as the combinatorial complexity of the many-body problem, on an equal footing. The nature of long-range order and phase transition behavior cannot be incorporated, but sometimes clues as to their origin can be discerned. The calculations presented include: a two-band Anderson model for an intermediate-valence system, wherein photoemission and fluctuation behavior is examined; a single-band Hubbard model for a ternary alloy system, such as copper-silver-gold; and a Hubbard model for a heavy- fermion system, wherein Fermi surface, transport, magnetic and superconducting properties are discussed. 148 refs., 31 figs., 24 tabs

  7. Application of high power microwave vacuum electron devices

    International Nuclear Information System (INIS)

    Ding Yaogen; Liu Pukun; Zhang Zhaochuan; Wang Yong; Shen Bin

    2011-01-01

    High power microwave vacuum electron devices can work at high frequency, high peak and average power. They have been widely used in military and civil microwave electron systems, such as radar, communication,countermeasure, TV broadcast, particle accelerators, plasma heating devices of fusion, microwave sensing and microwave heating. In scientific research, high power microwave vacuum electron devices are used mainly on high energy particle accelerator and fusion research. The devices include high peak power klystron, CW and long pulse high power klystron, multi-beam klystron,and high power gyrotron. In national economy, high power microwave vacuum electron devices are used mainly on weather and navigation radar, medical and radiation accelerator, TV broadcast and communication system. The devices include high power pulse and CW klystron, extended interaction klystron, traveling wave tube (TWT), magnetron and induced output tube (IOT). The state of art, common technology problems and trends of high power microwave vacuum electron devices are introduced in this paper. (authors)

  8. HIGH-CURRENT ERL-BASED ELECTRON COOLING FOR RHIC

    International Nuclear Information System (INIS)

    BEN-ZVI, I.

    2005-01-01

    The design of an electron cooler must take into account both electron beam dynamics issues as well as the electron cooling physics. Research towards high-energy electron cooling of RHIC is in its 3rd year at Brookhaven National Laboratory. The luminosity upgrade of RHIC calls for electron cooling of various stored ion beams, such as 100 GeV/A gold ions at collision energies. The necessary electron energy of 54 MeV is clearly out of reach for DC accelerator system of any kind. The high energy also necessitates a bunched beam, with a high electron bunch charge, low emittance and small energy spread. The Collider-Accelerator Department adopted the Energy Recovery Linac (ERL) for generating the high-current, high-energy and high-quality electron beam. The RHIC electron cooler ERL will use four Superconducting RF (SRF) 5-cell cavities, designed to operate at ampere-class average currents with high bunch charges. The electron source will be a superconducting, 705.75 MHz laser-photocathode RF gun, followed up by a superconducting Energy Recovery Linac (ERL). An R and D ERL is under construction to demonstrate the ERL at the unprecedented average current of 0.5 amperes. Beam dynamics performance and luminosity enhancement are described for the case of magnetized and non-magnetized electron cooling of RHIC

  9. High gain free electron laser at ETA

    International Nuclear Information System (INIS)

    Orzechowski, T.J.; Prosnitz, D.; Halbach, K.

    1983-01-01

    A single pass, tapered electron wiggler and associated beam transport has been constructed at the Experimental Test Accelerator (ETA) at Lawrence Livermore National Laboratory (LLNL). The system is designed to transport 1 kA of 4.5 MeV electrons with an emittance of 30 millirad-cm. The planar wiggler is provided by a pulsed electromagnet. The interaction region is an oversized rectangular waveguide. Quadrupole fields stabilize the beam in the plane parallel to the wiggler field. The 3 meter long wiggler has a 9.8 cm period. The Free Electron Laser (FEL) will serve as an amplifier for input frequencies of 35 GHz and 140 GHz. The facility is designed to produce better than 500 Megawatts peak power

  10. Contrasting above- and belowground organic matter decomposition and carbon and nitrogen dynamics in response to warming in High Arctic tundra.

    Science.gov (United States)

    Blok, Daan; Faucherre, Samuel; Banyasz, Imre; Rinnan, Riikka; Michelsen, Anders; Elberling, Bo

    2017-12-13

    Tundra regions are projected to warm rapidly during the coming decades. The tundra biome holds the largest terrestrial carbon pool, largely contained in frozen permafrost soils. With warming, these permafrost soils may thaw and become available for microbial decomposition, potentially providing a positive feedback to global warming. Warming may directly stimulate microbial metabolism but may also indirectly stimulate organic matter turnover through increased plant productivity by soil priming from root exudates and accelerated litter turnover rates. Here, we assess the impacts of experimental warming on turnover rates of leaf litter, active layer soil and thawed permafrost sediment in two high-arctic tundra heath sites in NE-Greenland, either dominated by evergreen or deciduous shrubs. We incubated shrub leaf litter on the surface of control and warmed plots for 1 and 2 years. Active layer soil was collected from the plots to assess the effects of 8 years of field warming on soil carbon stocks. Finally, we incubated open cores filled with newly thawed permafrost soil for 2 years in the active layer of the same plots. After field incubation, we measured basal respiration rates of recovered thawed permafrost cores in the lab. Warming significantly reduced litter mass loss by 26% after 1 year incubation, but differences in litter mass loss among treatments disappeared after 2 years incubation. Warming also reduced litter nitrogen mineralization and decreased the litter carbon to nitrogen ratio. Active layer soil carbon stocks were reduced 15% by warming, while soil dissolved nitrogen was reduced by half in warmed plots. Warming had a positive legacy effect on carbon turnover rates in thawed permafrost cores, with 10% higher respiration rates measured in cores from warmed plots. These results demonstrate that warming may have contrasting effects on above- and belowground tundra carbon turnover, possibly governed by microbial resource availability. © 2017 John

  11. High fidelity does not preclude colonization: range expansion of molting Black Brant on the Arctic coast of Alaska

    Science.gov (United States)

    Flint, Paul L.; Meixell, Brandt W.; Mallek, Edward J.

    2014-01-01

    High rates of site fidelity have been assumed to infer static distributions of molting geese in some cases. To test this assumption, we examined movements of individually marked birds to understand the underlying mechanisms of range expansion of molting Black Brant (Branta bernicla nigricans) on the Arctic Coastal Plain (ACP) of Alaska. The Teshekpuk Lake Special Area (TLSA) on the ACP was created to protect the primary molting area of Brant. When established in 1977, the TLSA was thought to include most, if not all, wetlands used by molting Brant on the ACP. From 2010 to 2013, we surveyed areas outside the TLSA and counted an average of 9800 Brant per year, representing 29–37% of all molting Brant counted on the ACP. We captured and banded molting Brant in 2011 and 2012 both within the TLSA and outside the TLSA at the Piasuk River Delta and Cape Simpson to assess movements of birds among areas across years. Estimates of movement rates out of the TLSA exceeded those into the TLSA, demonstrating overall directional dispersal. We found differences in sex and age ratios and proportions of adult females with brood patches, but no differences in mass dynamics for birds captured within and outside the TLSA. Overall fidelity rates to specific lakes (0.81, range = 0.49–0.92) were unchanged from comparable estimates obtained in the early 1990s. We conclude that Brant are dispersing from the TLSA into new molting areas while simultaneously redistributing within the TLSA, likely as a consequence of changes in relative habitat quality. Shifts in distribution resulted from colonization of new areas by young birds as well as low levels of directional dispersal of birds that previously molted in the TLSA. Based on combined counts, the overall number of molting Brant across the ACP has increased substantially.

  12. The Arctic Coastal Erosion Problem

    Energy Technology Data Exchange (ETDEWEB)

    Frederick, Jennifer M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Thomas, Matthew Anthony [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bull, Diana L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Jones, Craig A. [Integral Consulting Inc., San Francisco, CA (United States); Roberts, Jesse D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2016-09-01

    Permafrost-dominated coastlines in the Arctic are rapidly disappearing. Arctic coastal erosion rates in the United States have doubled since the middle of the twentieth century and appear to be accelerating. Positive erosion trends have been observed for highly-variable geomorphic conditions across the entire Arctic, suggesting a major (human-timescale) shift in coastal landscape evolution. Unfortunately, irreversible coastal land loss in this region poses a threat to native, industrial, scientific, and military communities. The Arctic coastline is vast, spanning more than 100,000 km across eight nations, ten percent of which is overseen by the United States. Much of area is inaccessible by all-season roads. People and infrastructure, therefore, are commonly located near the coast. The impact of the Arctic coastal erosion problem is widespread. Homes are being lost. Residents are being dispersed and their villages relocated. Shoreline fuel storage and delivery systems are at greater risk. The U.S. Department of Energy (DOE) and Sandia National Laboratories (SNL) operate research facilities along some of the most rapidly eroding sections of coast in the world. The U.S. Department of Defense (DOD) is struggling to fortify coastal radar sites, operated to ensure national sovereignty in the air, against the erosion problem. Rapid alterations to the Arctic coastline are facilitated by oceanographic and geomorphic perturbations associated with climate change. Sea ice extent is declining, sea level is rising, sea water temperature is increasing, and permafrost state is changing. The polar orientation of the Arctic exacerbates the magnitude and rate of the environmental forcings that facilitate coastal land area loss. The fundamental mechanics of these processes are understood; their non-linear combination poses an extreme hazard. Tools to accurately predict Arctic coastal erosion do not exist. To obtain an accurate predictive model, a coupling of the influences of

  13. Electron ray tracing with high accuracy

    International Nuclear Information System (INIS)

    Saito, K.; Okubo, T.; Takamoto, K.; Uno, Y.; Kondo, M.

    1986-01-01

    An electron ray tracing program is developed to investigate the overall geometrical and chromatic aberrations in electron optical systems. The program also computes aberrations due to manufacturing errors in lenses and deflectors. Computation accuracy is improved by (1) calculating electrostatic and magnetic scalar potentials using the finite element method with third-order isoparametric elements, and (2) solving the modified ray equation which the aberrations satisfy. Computation accuracy of 4 nm is achieved for calculating optical properties of the system with an electrostatic lens

  14. High quality flux control system for electron gun evaporation

    International Nuclear Information System (INIS)

    Appelbloom, A.M.; Hadley, P.; van der Marel, D.; Mooij, J.E.

    1991-01-01

    This paper reports on a high quality flux control system for electron gun evaporation developed and tested for the MBE growth of high temperature superconductors. The system can be applied to any electron gun without altering the electron gun itself. Essential elements of the system are a high bandwidth mass spectrometer, control electronics and a high voltage modulator to sweep the electron beam over the melt at high frequencies. the sweep amplitude of the electron beam is used to control the evaporation flux at high frequencies. The feedback loop of the system has a bandwidth of over 100 Hz, which makes it possible to grow superlattices and layered structures in a fast and precisely controlled manner

  15. Carboniferous-Permian sedimentology and stratigraphy of the Nordfjorden High and Loppa Spur, Arctic Norway

    DEFF Research Database (Denmark)

    Ahlborn, Morten

    Abstract (shortened) Facies analysis of Late Paleozoic warm-water carbonates, were conducted in order to investigate the depositional evolution, cyclicity, internal architecture and sequence stratigraphy of the upper Gipsdalen Group carbonate platform on the Nordfjorden High in central Spitsberge...

  16. High-Affinity Methanotrophy Informed by Genome-Wide Analysis of Upland Soil Cluster Alpha (USCα) from Axel Heiberg Island, Canadian High Arctic

    Science.gov (United States)

    Rusley, C.; Onstott, T. C.; Lau, M.

    2017-12-01

    Methane (CH4) is a potent greenhouse gas whose proper budgeting is vital to climate predictions. Recent studies have identified upland Arctic mineral cryosols as consistent CH4 sinks, drawing CH4 from both the atmosphere and underlying anaerobic soil layers. Global atmospheric CH4 uptake is proposed to be mediated by high-affinity methanotrophs based on the detection of the marker gene pmoA (particulate methane monooxygenase beta subunit). However, a lack of pure cultures and scarcity of genomic information have hindered our understanding of their metabolic capabilities and versatility. Together with the missing genetic linkage between its pmoA and 16S ribosomal RNA (rRNA) gene, the factors that control the distribution and magnitude of high-affinity methanotrophy in the Arctic permafrost-affected region have remained elusive. Using 21 metagenomic datasets of surface soils obtained from long-term core incubation experiments,1 this bioinformatics study aimed to reconstruct the draft genome of the Upland Soil Cluster α-proteobacteria (USCα), the high-affinity methanotroph previously detected in the samples,2 and to determine its phylogeny and metabolic requirements. We obtained a genome bin containing the high-affinity form of the USCα-like pmoA gene. The 3.03 Mbp assembly is 91.6% complete with a unique set of single-copy marker genes. The 16S rRNA gene fragment of USCα belongs to the α-proteobacterial family Beijerinckiaceae. Genome annotation indicates possible formaldehyde oxidation via tetrahydromethanopterin-linked C1 transfer pathways, acetate utilization, carbon fixation via the Calvin-Benson-Bassham cycle, and glycogen production. Notably, the key enzymes for formaldehyde assimilation via the serine and ribulose monophosphate pathways are missing. The presence of genes encoding nitrate reductase and hemoglobin suggests adaptation to low O2 under water-logged conditions. Since USCα has versatile carbon metabolisms, it may not be an obligate methanotroph

  17. STANFORD: Producing highly polarized electrons (2)

    International Nuclear Information System (INIS)

    Anon.

    1991-01-01

    Electron spin polarization above 70% by photoemission from a specially prepared semiconductor has been achieved by T. Maruyama and E. Garwin of the Stanford Linear Accelerator Center (SLAC), R. Prepost and G. Zapalac of Wisconsin, and J. Walker and S. Smith of Berkeley

  18. Scattering of high energy electrons on deuteron

    International Nuclear Information System (INIS)

    Grossetete, B.

    1964-12-01

    The aim of this work is to obtain information on the neutron form factor from the study of the scattering of electrons on deuterium. The first part is dedicated to the theoretical study of the elastic and inelastic scattering. We introduce different form factors: Sachs form factor, the Pauli and Dirac form factors, they appear in the analytic expression of the scattering cross-section. We show how the deuteron form factors can be deduced from neutron's and proton's form factors. In the case of the inelastic scattering we show how the cross section can be broken into components associated to partial waves and we obtain different formulas for the inelastic cross-section based on the Breit formula or the Durand formalism. The second part is dedicated to the experiment setting of electron scattering on deuterium. The elastic scattering experiment has been made on solid or liquid CD 2 targets while inelastic scattering has been studied on a liquid target. We have used an electron beam produced by the Orsay linear accelerator and the scattered electrons have been analysed by a magnetic spectrometer and a Cerenkov detector. The results give a very low value (slightly positive)for the charge form factor of the neutron and a magnetic form factor for the neutron slightly below that of the proton [fr

  19. Electronic ceramics in high-temperature environments

    International Nuclear Information System (INIS)

    Searcy, A.W.; Meschi, D.J.

    1982-01-01

    Simple thermodynamic means are described for understanding and predicting the influence of temperature changes, in various environments, on electronic properties of ceramics. Thermal gradients, thermal cycling, and vacuum annealing are discussed, as well as the variations of ctivities and solubilities with temperature. 7 refs

  20. Improving Arctic Sea Ice Edge Forecasts by Assimilating High Horizontal Resolution Sea Ice Concentration Data into the US Navy’s Ice Forecast Systems

    Science.gov (United States)

    2016-06-13

    1735-2015 © Author(s) 2015. CC Attribution 3.0 License. Improving Arctic sea ice edge forecasts by assimilating high horizontal resolution sea ice...concentration data into the US Navy’s ice forecast systems P. G. Posey1, E. J. Metzger1, A. J. Wallcraft1, D. A. Hebert1, R. A. Allard1, O. M. Smedstad2...error within the US Navy’s operational sea ice forecast systems gained by assimilating high horizontal resolution satellite-derived ice concentration

  1. Electron beam generation in high voltage glow discharges

    International Nuclear Information System (INIS)

    Rocca, J.J.; Szapiro, B.; Murray, C.

    1989-01-01

    The generation of intense CW and pulsed electron beams in glow discharges in reviewed. Glow discharge electron guns operate at a pressure of the order of 1 Torr and often have an advantage in applications that require a broad area electron beam in a gaseous atmosphere, such as laser excitation and some aspects of materials processing. Aspects of electron gun design are covered. Diagnostics of the high voltage glow discharges including the electric field distribution mapped by Doppler free laser spectroscopy, and plasma density and electron temperature measurements of the electron yield of different cathode materials under glow discharge conditions are presented

  2. Highly solvatochromic emission of electron donor-acceptor compounds containing propanedioato boron electron acceptors

    NARCIS (Netherlands)

    Brouwer, A.M.; Bakker, N.A.C.; Wiering, P.G.; Verhoeven, J.W.

    1991-01-01

    Light-induced electron transfer occurs in bifunctional compounds consisting of 1,3-diphenylpropanedioato boron oxalate or fluoride electron acceptors and simple aromatic electron-donor groups, linked by a methylene bridge; fluorescence from the highly polar charge-transfer excited state is

  3. Highly efficient electron gun with a single-atom electron source

    International Nuclear Information System (INIS)

    Ishikawa, Tsuyoshi; Urata, Tomohiro; Cho, Boklae; Rokuta, Eiji; Oshima, Chuhei; Terui, Yoshinori; Saito, Hidekazu; Yonezawa, Akira; Tsong, Tien T.

    2007-01-01

    The authors have demonstrated highly collimated electron-beam emission from a practical electron gun with a single-atom electron source; ∼80% of the total emission current entered the electron optics. This ratio was two or three orders of magnitude higher than those of the conventional electron sources such as a cold field emission gun and a Zr/O/W Schottky gun. At the pressure of less than 1x10 -9 Pa, the authors observed stable emission of 20 nA, which generates the specimen current of 5 pA required for scanning electron microscopes

  4. High-Current Plasma Electron Sources

    International Nuclear Information System (INIS)

    Gushenets, J.Z.; Krokhmal, V.A.; Krasik, Ya. E.; Felsteiner, J.; Gushenets, V.

    2002-01-01

    In this report we present the design, electrical schemes and preliminary results of a test of 4 different electron plasma cathodes operating under Kg h-voltage pulses in a vacuum diode. The first plasma cathode consists of 6 azimuthally symmetrically distributed arc guns and a hollow anode having an output window covered by a metal grid. Plasma formation is initiated by a surface discharge over a ceramic washer placed between a W-made cathode and an intermediate electrode. Further plasma expansion leads to a redistribution of the discharge between the W-cathode and the hollow anode. An accelerating pulse applied between the output anode grid and the collector extracts electrons from this plasma. The operation of another plasma cathode design is based on Penning discharge for preliminary plasma formation. The main glow discharge occurs between an intermediate electrode of the Penning gun and the hollow anode. To keep the background pressure in the accelerating gap at P S 2.5x10 4 Torr either differential pumping or a pulsed gas puff valve were used. The operation of the latter electron plasma source is based on a hollow cathode discharge. To achieve a sharp pressure gradient between the cathode cavity and the accelerating gap a pulsed gas puff valve was used. A specially designed ferroelectric plasma cathode initiated plasma formation inside the hollow cathode. This type of the hollow cathode discharge ignition allowed to achieve a discharge current of 1.2 kA at a background pressure of 2x10 4 Torr. All these cathodes were developed and initially tested inside a planar diode with a background pressure S 2x10 4 Torr under the same conditions: accelerating voltage 180 - 300 kV, pulse duration 200 - 400 ns, electron beam current - 1 - 1.5 kA, and cross-sectional area of the extracted electron beam 113 cm 2

  5. Biogenic volatile organic compound emissions along a high arctic soil moisture gradient

    DEFF Research Database (Denmark)

    Svendsen, Sarah Hagel; Lindwall, Frida; Michelsen, Anders

    2016-01-01

    emissions of BVOCs were found from vegetation communities dominated by Salix arctica and Cassiope tetragona, which had emission profiles dominated by isoprene and monoterpenes, respectively. These results show that emissions of BVOCs are highly dependent on the plant cover supported by the varying soil...

  6. Electron capture by highly stripped ions

    International Nuclear Information System (INIS)

    Greenland, P.T.

    1981-06-01

    This review describes theories of electron capture suitable for the description of rearrangement collisions between atomic hydrogen and completely stripped projectiles with charge greater than unity. The region of impact velocity considered lies between 0.05 and 3 au, which is of technological importance in fusion power devices. The semiclassical, impact parameter formalism is discussed and the use of atomic expansions at medium impact velocity is described. Experimental results for both completely and partially stripped projectiles are reviewed. The use of a molecular basis at low energy, and the role of pseudocrossings peculiar to the two centre Coulomb interaction are described. Finally, purely classical techniques, in which the electron wavefunction is represented by an ensemble of Kepler orbits are considered. The review was completed in February 1981. (author)

  7. ELECTRON CLOUD EFFECTS IN HIGH INTENSITY PROTON ACCELERATORS

    International Nuclear Information System (INIS)

    Wei, J.; Macek, R.J.

    2002-01-01

    One of the primary concerns in the design and operation of high-intensity proton synchrotrons and accumulators is the electron cloud and associated beam loss and instabilities. Electron-cloud effects are observed at high-intensity proton machines like the Los Alamos National Laboratory's PSR and CERN's SPS, and investigated experimentally and theoretically. In the design of next-generation high-intensity proton accelerators like the Spallation Neutron Source ring, emphasis is made in minimizing electron production and in enhancing Landau damping. This paper reviews the present understanding of the electron-cloud effects and presents mitigation measures

  8. ELECTRON CLOUD EFFECTS IN HIGH INTENSITY PROTON ACCELERATORS.

    Energy Technology Data Exchange (ETDEWEB)

    WEI,J.; MACEK,R.J.

    2002-04-14

    One of the primary concerns in the design and operation of high-intensity proton synchrotrons and accumulators is the electron cloud and associated beam loss and instabilities. Electron-cloud effects are observed at high-intensity proton machines like the Los Alamos National Laboratory's PSR and CERN's SPS, and investigated experimentally and theoretically. In the design of next-generation high-intensity proton accelerators like the Spallation Neutron Source ring, emphasis is made in minimizing electron production and in enhancing Landau damping. This paper reviews the present understanding of the electron-cloud effects and presents mitigation measures.

  9. Evaluating the performance of coupled snow-soil models in SURFEXv8 to simulate the permafrost thermal regime at a high Arctic site

    Science.gov (United States)

    Barrere, Mathieu; Domine, Florent; Decharme, Bertrand; Morin, Samuel; Vionnet, Vincent; Lafaysse, Matthieu

    2017-09-01

    Climate change projections still suffer from a limited representation of the permafrost-carbon feedback. Predicting the response of permafrost temperature to climate change requires accurate simulations of Arctic snow and soil properties. This study assesses the capacity of the coupled land surface and snow models ISBA-Crocus and ISBA-ES to simulate snow and soil properties at Bylot Island, a high Arctic site. Field measurements complemented with ERA-Interim reanalyses were used to drive the models and to evaluate simulation outputs. Snow height, density, temperature, thermal conductivity and thermal insulance are examined to determine the critical variables involved in the soil and snow thermal regime. Simulated soil properties are compared to measurements of thermal conductivity, temperature and water content. The simulated snow density profiles are unrealistic, which is most likely caused by the lack of representation in snow models of the upward water vapor fluxes generated by the strong temperature gradients within the snowpack. The resulting vertical profiles of thermal conductivity are inverted compared to observations, with high simulated values at the bottom of the snowpack. Still, ISBA-Crocus manages to successfully simulate the soil temperature in winter. Results are satisfactory in summer, but the temperature of the top soil could be better reproduced by adequately representing surface organic layers, i.e., mosses and litter, and in particular their water retention capacity. Transition periods (soil freezing and thawing) are the least well reproduced because the high basal snow thermal conductivity induces an excessively rapid heat transfer between the soil and the snow in simulations. Hence, global climate models should carefully consider Arctic snow thermal properties, and especially the thermal conductivity of the basal snow layer, to perform accurate predictions of the permafrost evolution under climate change.

  10. The Siberian High and Arctic Sea Ice: Long-term Climate Change and Impacts on Air Pollution during Wintertime in China

    Science.gov (United States)

    Long, X.; Zhao, S.; Feng, T.; Tie, X.; Li, G.

    2017-12-01

    China has undergone severe air pollution during wintertime as national industrialization and urbanization have been increasingly developed in the past three decades. It has been suggested that high emission and adverse weather patterns contribute to wintertime air pollution. Recent studies propose that climate change and Arctic sea ice loss likely lead to extreme haze events in winter. Here we use two reanalysis and observational datasets to present the trends of Siberian High (SH) intensity over Eurasia, and Arctic temperature and sea ice. The results show the Arctic region of Asia is becoming warming accompanied by a rapid decline of sea ice while Eurasia is cooling and SH intensity is gradually enhancing. Wind patterns induced by these changes cause straight westerly prevailing over Eurasia at the year of weak SH while strengthened northerly winds at the year of strong SH. Therefore, we utilize regional dynamical and chemical WRF-Chem model to determine the impact of SH intensity difference on wintertime air pollution in China. As a result, enhancing northerly winds at the year of strong SH rapidly dilute and transport air pollution, causing a decline of 50 - 400 µg m-3 PM2.5 concentrations relative to that at the year of weak SH. We also assess the impact of emission reduction to half the current level on air pollution. The results show that emission reduction by 50% has an equivalent impact as the variability of SH intensity. This suggests that climate change over Eurasia has largely offset the negative impact of emission on air pollution and it is urgently needed to take measures to mitigate air pollution. In view of current high emission scenario in China, it will be a long way to effectively mitigate, or ultimately prevent wintertime air pollution.

  11. High-power fiber lasers for photocathode electron injectors

    Directory of Open Access Journals (Sweden)

    Zhi Zhao

    2014-05-01

    Full Text Available Many new applications for electron accelerators require high-brightness, high-average power beams, and most rely on photocathode-based electron injectors as a source of electrons. To achieve such a photoinjector, one requires both a high-power laser system to produce the high average current beam, and also a system at reduced repetition rate for electron beam diagnostics to verify high beam brightness. Here we report on two fiber laser systems designed to meet these specific needs, at 50 MHz and 1.3 GHz repetition rate, together with pulse pickers, second harmonic generation, spatiotemporal beam shaping, intensity feedback, and laser beam transport. The performance and flexibility of these laser systems have allowed us to demonstrate electron beam with both low emittance and high average current for the Cornell energy recovery linac.

  12. High Resolution Electron Microscopy in Materials Science

    International Nuclear Information System (INIS)

    Amelinckx, S.

    1986-01-01

    This paper illustrates different operating modes of the electron microscope and shows the image formation in an ideal microscope. Diffraction contrast is used in the study of crystal defects, such as dislocations and planar interfaces. Methods are surveyed which give at least a rudimentary image of the lattice and therefore make use of at least two interfering beams. Special attention is given to images which also carry structural information and therefore imply the use of many beams. The underlying theory is discussed as are the theories of Van Dyck, Spence and Cowley. These are illustrated by means of a number of recent case studies

  13. LAT Perspectives in Detection of High Energy Cosmic Ray Electrons

    International Nuclear Information System (INIS)

    Moiseev, Alexander; Ormes, J.F.; Funk, Stefan

    2007-01-01

    The LAT science objectives and capabilities in the detection of high energy electrons in the energy range from 20 GeV to ∼1.5 TeV are presented. LAT simulations are used to establish the event selections. It is found that maintaining the efficiency of electron detection at the level of 30%, the residual hadron contamination does not exceed 2-3% of the electron flux. It is expected to collect ∼ ten million of electrons with the energy above 20 GeV for one year of observation. Precise spectrum reconstruction with collected electron statistics opens the unique opportunity to investigate several important problems such as models of IC radiation, revealing the signatures of nearby sources such as high energy cutoff in the electron spectrum, testing the propagation model, and search for KKDM particles decay through their contribution to the electron spectrum

  14. East Siberian Sea, an Arctic region of very high biogeochemical activity

    Directory of Open Access Journals (Sweden)

    L. G. Anderson

    2011-06-01

    Full Text Available Shelf seas are among the most active biogeochemical marine environments and the East Siberian Sea is a prime example. This sea is supplied by seawater from both the Atlantic and Pacific Oceans and has a substantial input of river runoff. All of these waters contribute chemical constituents, dissolved and particulate, but of different signatures. Sea ice formation during the winter season and melting in the summer has a major impact on physical as well as biogeochemical conditions. The internal circulation and water mass distribution is significantly influenced by the atmospheric pressure field. The western region is dominated by input of river runoff from the Laptev Sea and an extensive input of terrestrial organic matter. The microbial decay of this organic matter produces carbon dioxide (CO2 that oversaturates all waters from the surface to bottom relative to atmospheric level, even when primary production, inferred from low surface water nutrients, has occurred. The eastern surface waters were under-saturated with respect to CO2 illustrating the dominance of marine primary production. The drawdown of dissolved inorganic carbon equals a primary production of ~0.8 ± 2 mol C m−2, which when multiplied by half the area of the East Siberian Sea, ~500 000 km2, results in an annual primary production of 0.4 (± 1 × 1012 mol C or ~4 (± 10 × 1012 gC. Microbial decay occurs through much of the water column, but dominates at the sediment interface where the majority of organic matter ends up, thus more of the decay products are recycled to the bottom water. High nutrient concentrations and fugacity of CO2 and low oxygen and pH were observed in the bottom waters. Another signature of organic matter decomposition, methane (CH4, was observed in very high but variable concentrations. This is due to its seabed sources of glacial origin or modern production from

  15. On some aspects of high voltage electron microscopy

    International Nuclear Information System (INIS)

    Jouffrey, B.; Trinquier, J.

    1987-01-01

    The present paper deals with high voltage electron microscopy (HVEM). It is an overview on this domain due to the pionneer work of G. Dupouy which has permitted to perform a new kind of electron microscopy. Since this time, HVEM has shown its interest in high resolution, irradiations, chemical analysis, in situ experiments

  16. On the electronic structure of high Tc superconductors

    International Nuclear Information System (INIS)

    Fink, J.; Nuecker, N.; Romberg, H.; Alexander, M.; Knupfer, M.; Mante, J.; Claessen, R.; Buslaps, T.; Harm, S.; Manzke, R.; Skibowski, M.

    1992-01-01

    Studies of the electronic structure of high-T c superconductors and related compounds by high-energy spectroscopies are reviewed. In particular, we report on investigations by electron energy-loss, angle-resolved photoemission, and inverse angle-resolved photoemission spectroscopy. Information on the symmetry and the character of states close to the Fermi level has been obtained. 25 refs., 8 figs

  17. In situ response of Nostoc commune s.l. colonies to desiccation in Central Svalbard, Norwegian High Arctic

    Czech Academy of Sciences Publication Activity Database

    Kvíderová, Jana; Elster, Josef; Šimek, Miloslav

    2011-01-01

    Roč. 11, č. 1 (2011), s. 87-97 ISSN 1802-5439 R&D Projects: GA MŠk ME 934; GA MŠk LA341; GA MŠk LC06066; GA AV ČR IAA600660605 Institutional research plan: CEZ:AV0Z60050516; CEZ:AV0Z60660521 Keywords : desiccation * cyanobacteria * Arctic Subject RIV: EF - Botanics Impact factor: 1.327, year: 2011

  18. Electron acceleration via high contrast laser interacting with submicron clusters

    International Nuclear Information System (INIS)

    Zhang Lu; Chen Liming; Wang Weiming; Yan Wenchao; Yuan Dawei; Mao Jingyi; Wang Zhaohua; Liu Cheng; Shen Zhongwei; Li Yutong; Dong Quanli; Lu Xin; Ma Jinglong; Wei Zhiyi; Faenov, Anatoly; Pikuz, Tatiana; Li Dazhang; Sheng Zhengming; Zhang Jie

    2012-01-01

    We experimentally investigated electron acceleration from submicron size argon clusters-gas target irradiated by a 100 fs, 10 TW laser pulses having a high-contrast. Electron beams are observed in the longitudinal and transverse directions to the laser propagation. The measured energy of the longitudinal electron reaches 600 MeV and the charge of the electron beam in the transverse direction is more than 3 nC. A two-dimensional particle-in-cell simulation of the interaction has been performed and it shows an enhancement of electron charge by using the cluster-gas target.

  19. Geology of the Severnaya Zemlya Archipelago and the North Kara Terrane in the Russian high Arctic

    Science.gov (United States)

    Lorenz, Henning; Männik, Peep; Gee, David; Proskurnin, Vasilij

    2008-05-01

    The Severnaya Zemlya Archipelago is located at 80°N near the continental shelf break, between the Kara and Laptev seas. Sedimentary successions of Neoproterozoic and Palaeozoic age dominate the bedrock geology. Together with Northern Tajmyr, Severnaya Zemlya constitutes the main land areas of the North Kara Terrane (NKT), which is inferred here to have been a part of the Timanide margin of Baltica, i.e. an integral part of Baltica at least since the Vendian. Vendian turbidites derived from the Timanide Orogen are inferred to have been deposited on Neoproterozoic greenschist facies, granite-intruded basement. Shallow-water siliclastic deposition in the Early to Mid-Cambrian was followed by highly organic-rich shales in the Late Cambrian and influx of more turbidites. An episode of folding, the Kan’on River deformation, separates these formations from the overlying Tremadocian conglomerates and sandstones. In the Early Ordovician, rift-related magmatic rocks accompanied the deposition of variegated marls, sandstones, carbonates and evaporites. Dark shales and gypsiferous limestones characterise the Mid-Ordovician. Late Ordovician quartz-sandstones mark a hiatus, followed by carbonate rocks that extend up into and through most of the Silurian. The latter give way upwards into Old Red Sandstones, which are inferred to have been deposited in a Caledonian foreland basin. Deformation, reaching the area in the latest Devonian or earliest Carboniferous and referred to as the Severnaya Zemlya episode, is thought to be Caledonian-related. The dominating E-vergent structure was controlled by décollement zones in Ordovician evaporite-bearing strata; detachment folds and thrusts developed in the west and were apparently impeded by a barrier of Ordovician igneous rocks in the east. Below the décollement zones, the Neoproterozoic to Early Ordovician succession was deformed into open to close folds. The exposed strata in the lower structural level have been juxtaposed with

  20. Seasonal variation of atmospheric particle number concentrations, new particle formation and atmospheric oxidation capacity at the high Arctic site Villum Research Station, Station Nord

    Directory of Open Access Journals (Sweden)

    Q. T. Nguyen

    2016-09-01

    Full Text Available This work presents an analysis of the physical properties of sub-micrometer aerosol particles measured at the high Arctic site Villum Research Station, Station Nord (VRS, northeast Greenland, between July 2010 and February 2013. The study focuses on particle number concentrations, particle number size distributions and the occurrence of new particle formation (NPF events and their seasonality in the high Arctic, where observations and characterization of such aerosol particle properties and corresponding events are rare and understanding of related processes is lacking.A clear accumulation mode was observed during the darker months from October until mid-May, which became considerably more pronounced during the prominent Arctic haze months from March to mid-May. In contrast, nucleation- and Aitken-mode particles were predominantly observed during the summer months. Analysis of wind direction and wind speed indicated possible contributions of marine sources from the easterly side of the station to the observed summertime particle number concentrations, while southwesterly to westerly winds dominated during the darker months. NPF events lasting from hours to days were mostly observed from June until August, with fewer events observed during the months with less sunlight, i.e., March, April, September and October. The results tend to indicate that ozone (O3 might be weakly anti-correlated with particle number concentrations of the nucleation-mode range (10–30 nm in almost half of the NPF events, while no positive correlation was observed. Calculations of air mass back trajectories using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT model for the NPF event days suggested that the onset or interruption of events could possibly be explained by changes in air mass origin. A map of event occurrence probability was computed, indicating that southerly air masses from over the Greenland Sea were more likely linked to those

  1. Soil pH is a Key Determinant of Soil Fungal Community Composition in the Ny-Ålesund Region, Svalbard (High Arctic)

    Science.gov (United States)

    Zhang, Tao; Wang, Neng-Fei; Liu, Hong-Yu; Zhang, Yu-Qin; Yu, Li-Yan

    2016-01-01

    This study assessed the fungal community composition and its relationships with properties of surface soils in the Ny-Ålesund Region (Svalbard, High Arctic). A total of thirteen soil samples were collected and soil fungal community was analyzed by 454 pyrosequencing with fungi-specific primers targeting the rDNA internal transcribed spacer (ITS) region. The following eight soil properties were analyzed: pH, organic carbon (C), organic nitrogen (N), ammonium nitrogen (NH4+-N), silicate silicon (SiO42--Si), nitrite nitrogen (NO2--N), phosphate phosphorus (PO43--P), and nitrate nitrogen (NO3--N). A total of 57,952 reads belonging to 541 operational taxonomic units (OTUs) were found. of these OTUs, 343 belonged to Ascomycota, 100 to Basidiomycota, 31 to Chytridiomycota, 22 to Glomeromycota, 11 to Zygomycota, 10 to Rozellomycota, whereas 24 belonged to unknown fungi. The dominant orders were Helotiales, Verrucariales, Agaricales, Lecanorales, Chaetothyriales, Lecideales, and Capnodiales. The common genera (>eight soil samples) were Tetracladium, Mortierella, Fusarium, Cortinarius, and Atla. Distance-based redundancy analysis (db-rda) and analysis of similarities (ANOSIM) revealed that soil pH (p = 0.001) was the most significant factor in determining the soil fungal community composition. Members of Verrucariales were found to predominate in soils of pH 8–9, whereas Sordariales predominated in soils of pH 7–8 and Coniochaetales predominated in soils of pH 6–7. The results suggest the presence and distribution of diverse soil fungal communities in the High Arctic, which can provide reliable data for studying the ecological responses of soil fungal communities to climate changes in the Arctic. PMID:26955371

  2. Soil pH is a key determinant of soil fungal community composition in the Ny-Ålesund Region, Svalbard (High Arctic

    Directory of Open Access Journals (Sweden)

    Tao eZhang

    2016-02-01

    Full Text Available This study assessed the fungal community composition and its relationships with properties of surface soils in the Ny-Ålesund Region (Svalbard, High Arctic. A total of thirteen soil samples were collected and soil fungal community was analyzed by 454 pyrosequencing with fungi-specific primers targeting the rDNA internal transcribed spacer (ITS region. The following eight soil properties were analyzed: pH, organic carbon (C, organic nitrogen (N, ammonium nitrogen (NH4+-N, silicate silicon (SiO42--Si, nitrite nitrogen (NO2--N, phosphate phosphorus (PO43--P and nitrate nitrogen (NO3--N. A total of 57,952 reads belonging to 541 operational taxonomic units (OTUs were found. Of these OTUs, 343 belonged to Ascomycota, 100 to Basidiomycota, 31 to Chytridiomycota, 22 to Glomeromycota, 11 to Zygomycota, 10 to Rozellomycota, whereas 24 belonged to unknown fungi. The dominant orders were Helotiales, Verrucariales, Agaricales, Lecanorales, Chaetothyriales, Lecideales, and Capnodiales. The common genera (>8 soil samples were Tetracladium, Mortierella, Fusarium, Cortinarius, and Atla. Distance-based redundancy analysis (db-rda and analysis of similarities (ANOSIM revealed that soil pH (p=0.001 was the most significant factor in determining the soil fungal community composition. Members of Verrucariales were found to predominate in soils of pH 8-9, whereas Sordariales predominated in soils of pH 7-8 and Coniochaetales predominated in soil samples of pH 6-7. The results suggest the presence and distribution of diverse soil fungal communities in the High Arctic, which can provide reliable data for studying the ecological responses of soil fungal communities to climate changes in the Arctic.

  3. Generation of Low-Energy High-Current Electron Beams in Plasma-Anode Electron Guns

    Science.gov (United States)

    Ozur, G. E.; Proskurovsky, D. I.

    2018-01-01

    This paper is a review of studies on the generation of low-energy high-current electron beams in electron guns with a plasma anode and an explosive-emission cathode. The problems related to the initiation of explosive electron emission under plasma and the formation and transport of high-current electron beams in plasma-filled systems are discussed consecutively. Considerable attention is given to the nonstationary effects that occur in the space charge layers of plasma. Emphasis is also placed on the problem of providing a uniform energy density distribution over the beam cross section, which is of critical importance in using electron beams of this type for surface treatment of materials. Examples of facilities based on low-energy high-current electron beam sources are presented and their applications in materials science and practice are discussed.

  4. Interaction webs in arctic ecosystems

    DEFF Research Database (Denmark)

    Schmidt, Niels M.; Hardwick, Bess; Gilg, Olivier

    2017-01-01

    How species interact modulate their dynamics, their response to environmental change, and ultimately the functioning and stability of entire communities. Work conducted at Zackenberg, Northeast Greenland, has changed our view on how networks of arctic biotic interactions are structured, how...... they vary in time, and how they are changing with current environmental change: firstly, the high arctic interaction webs are much more complex than previously envisaged, and with a structure mainly dictated by its arthropod component. Secondly, the dynamics of species within these webs reflect changes...... that the combination of long-term, ecosystem-based monitoring, and targeted research projects offers the most fruitful basis for understanding and predicting the future of arctic ecosystems....

  5. CAMAC high energy physics electronics hardware

    International Nuclear Information System (INIS)

    Kolpakov, I.F.

    1977-01-01

    CAMAC hardware for high energy physics large spectrometers and control systems is reviewed as is the development of CAMAC modules at the High Energy Laboratory, JINR (Dubna). The total number of crates used at the Laboratory is 179. The number of CAMAC modules of 120 different types exceeds 1700. The principles of organization and the structure of developed CAMAC systems are described. (author)

  6. Electronic DC transformer with high power density

    NARCIS (Netherlands)

    Pavlovský, M.

    2006-01-01

    This thesis is concerned with the possibilities of increasing the power density of high-power dc-dc converters with galvanic isolation. Three cornerstones for reaching high power densities are identified as: size reduction of passive components, reduction of losses particularly in active components

  7. Overlap of electron core states for very high compressions

    International Nuclear Information System (INIS)

    Straub, G.

    1985-01-01

    At normal density and for modest compressions, the electronic structure of a metal can be accurately described by treating the conduction electrons and their interactions with the usual methods of band theory. The core electrons remain essentially the same as for an isolated free atom and do not participate in the bonding forces responsible for creating a condensed phase. As the density increases, the core electrons begin to ''see'' one another as the overlap of the tails of wave functions can no longer be neglected. The electronic structure of the core electrons is responsible for an effective repulsive interaction that eventually becomes free-electron-like at very high compressions. The electronic structure of the interacting core electrons may be treated in a simple manner using the Atomic Surface Method (ASM). The ASM is a first-principles treatment of the electronic structure involving a rigorous integration of the Schroedinger equation within the atomic-sphere approximation. Solid phase wave functions are constructed from isolated atom wave functions and the band width W/sub l/ and the center of gravity of the band C/sub l/ are obtained from simple formulas. The ASM can also utilize analytic forms of the atomic wave functions and thus provide direct functional dependence of various aspects of the electronic structure. Of particular use in understanding the behavior of the core electrons, the ASM provides the analytic density dependence of the band widths and positions. 8 refs., 2 figs., 1 tab

  8. Bacterial community structure in High-Arctic snow and freshwater as revealed by pyrosequencing of 16S rRNA genes and cultivation

    Directory of Open Access Journals (Sweden)

    Annette K. Møller

    2013-04-01

    Full Text Available The bacterial community structures in High-Arctic snow over sea ice and an ice-covered freshwater lake were examined by pyrosequencing of 16S rRNA genes and 16S rRNA gene sequencing of cultivated isolates. Both the pyrosequence and cultivation data indicated that the phylogenetic composition of the microbial assemblages was different within the snow layers and between snow and freshwater. The highest diversity was seen in snow. In the middle and top snow layers, Proteobacteria, Bacteroidetes and Cyanobacteria dominated, although Actinobacteria and Firmicutes were relatively abundant also. High numbers of chloroplasts were also observed. In the deepest snow layer, large percentages of Firmicutes and Fusobacteria were seen. In freshwater, Bacteroidetes, Actinobacteria and Verrucomicrobia were the most abundant phyla while relatively few Proteobacteria and Cyanobacteria were present. Possibly, light intensity controlled the distribution of the Cyanobacteria and algae in the snow while carbon and nitrogen fixed by these autotrophs in turn fed the heterotrophic bacteria. In the lake, a probable lower light input relative to snow resulted in low numbers of Cyanobacteria and chloroplasts and, hence, limited input of organic carbon and nitrogen to the heterotrophic bacteria. Thus, differences in the physicochemical conditions may play an important role in the processes leading to distinctive bacterial community structures in High-Arctic snow and freshwater.

  9. Influence of high energy electrons on ECRH in LHD

    Directory of Open Access Journals (Sweden)

    Ogasawara S.

    2012-09-01

    Full Text Available The central bulk electron temperature of more than 20 keV is achieved in LHD as a result of increasing the injection power and the lowering the electron density near 2 × 1018 m−3. Such collision-less regime is important from the aspect of the neoclassical transport and also the potential structure formation. The presences of appreciable amount of high energy electrons are indicated from hard X-ray PHA, and the discrepancy between the stored energy and kinetic energy estimated from Thomson scattering. ECE spectrum are also sensitive to the presence of high energy electrons and discussed by solving the radiation transfer equation. The ECRH power absorption to the bulk and the high energy electrons are dramatically affected by the acceleration and the confinement of high energy electrons. The heating mechanisms and the acceleration process of high energy electrons are discussed by comparing the experimental results and the ray tracing calculation under assumed various density and mean energy of high energy electrons.

  10. Formation of a high quality electron beam using photo cathode RF electron gun

    International Nuclear Information System (INIS)

    Washio, Masakazu

    2000-01-01

    Formation of a high quality electron beam using photo cathode RF electron gun is expected for formation of a next generation high brilliant X-ray beam and a source for electron and positron collider. And, on a field of material science, as is possible to carry out an experiment under ultra short pulse and extremely high precision in time, it collects large expectation. Recently, formation of high quality beam possible to develop for multi directions and to use by everyone in future has been able to realize. Here were explained on electron beam source, principle and component on RF electron gun, working features on RF gun, features and simulation of RF gun under operation, and some views in near future. (G.K.)

  11. Nanostructures for Very High Frequency Electronics

    National Research Council Canada - National Science Library

    Gelmont, Boris

    2002-01-01

    The study of a new class of mesoscopic high frequency semi-conductor devices based on resonant tunneling in staggered-bandgap heterostructures with III-V semi-conductor ternary alloys such as AlGaSb...

  12. Highly efficient electron vortex beams generated by nanofabricated phase holograms

    Energy Technology Data Exchange (ETDEWEB)

    Grillo, Vincenzo, E-mail: vincenzo.grillo@nano.cnr.it [CNR-Istituto Nanoscienze, Centro S3, Via G Campi 213/a, I-41125 Modena (Italy); CNR-IMEM Parco Area delle Scienze 37/A, I-43124 Parma (Italy); Carlo Gazzadi, Gian [CNR-Istituto Nanoscienze, Centro S3, Via G Campi 213/a, I-41125 Modena (Italy); Karimi, Ebrahim [CNR-Istituto Nanoscienze, Centro S3, Via G Campi 213/a, I-41125 Modena (Italy); Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario K1N 6N5 (Canada); Mafakheri, Erfan [Dipartimento di Fisica Informatica e Matematica, Università di Modena e Reggio Emilia, via G Campi 213/a, I-41125 Modena (Italy); Boyd, Robert W. [Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario K1N 6N5 (Canada); Frabboni, Stefano [CNR-Istituto Nanoscienze, Centro S3, Via G Campi 213/a, I-41125 Modena (Italy); Dipartimento di Fisica Informatica e Matematica, Università di Modena e Reggio Emilia, via G Campi 213/a, I-41125 Modena (Italy)

    2014-01-27

    We propose an improved type of holographic-plate suitable for the shaping of electron beams. The plate is fabricated by a focused ion beam on a silicon nitride membrane and introduces a controllable phase shift to the electron wavefunction. We adopted the optimal blazed-profile design for the phase hologram, which results in the generation of highly efficient (25%) electron vortex beams. This approach paves the route towards applications in nano-scale imaging and materials science.

  13. Ion induced high energy electron emission from copper

    International Nuclear Information System (INIS)

    Ruano, G.; Ferron, J.

    2008-01-01

    We present measurements of secondary electron emission from Cu induced by low energy bombardment (1-5 keV) of noble gas (He + , Ne + and Ar + ) and Li + ions. We identify different potential and kinetic mechanisms and find the presence of high energetic secondary electrons for a couple of ion-target combinations. In order to understand the presence of these fast electrons we need to consider the Fermi shuttle mechanism and the different ion neutralization efficiencies.

  14. Highly efficient electron vortex beams generated by nanofabricated phase holograms

    International Nuclear Information System (INIS)

    Grillo, Vincenzo; Carlo Gazzadi, Gian; Karimi, Ebrahim; Mafakheri, Erfan; Boyd, Robert W.; Frabboni, Stefano

    2014-01-01

    We propose an improved type of holographic-plate suitable for the shaping of electron beams. The plate is fabricated by a focused ion beam on a silicon nitride membrane and introduces a controllable phase shift to the electron wavefunction. We adopted the optimal blazed-profile design for the phase hologram, which results in the generation of highly efficient (25%) electron vortex beams. This approach paves the route towards applications in nano-scale imaging and materials science

  15. First high-temperature electronics products survey 2005.

    Energy Technology Data Exchange (ETDEWEB)

    Normann, Randy Allen

    2006-04-01

    On April 4-5, 2005, a High-Temperature Electronics Products Workshop was held. This workshop engaged a number of governmental and private industry organizations sharing a common interest in the development of commercially available, high-temperature electronics. One of the outcomes of this meeting was an agreement to conduct an industry survey of high-temperature applications. This report covers the basic results of this survey.

  16. Apparatus and method for generating high density pulses of electrons

    International Nuclear Information System (INIS)

    Lee, C.; Oettinger, P.E.

    1981-01-01

    An apparatus and method are described for the production of high density pulses of electrons using a laser energized emitter. Caesium atoms from a low pressure vapour atmosphere are absorbed on and migrate from a metallic target rapidly heated by a laser to a high temperature. Due to this heating time being short compared with the residence time of the caesium atoms adsorbed on the target surface, copious electrons are emitted which form a high current density pulse. (U.K.)

  17. Properties of the electron cloud in a high-energy positron and electron storage ring

    International Nuclear Information System (INIS)

    Harkay, K.C.; Rosenberg, R.A.

    2003-01-01

    Low-energy, background electrons are ubiquitous in high-energy particle accelerators. Under certain conditions, interactions between this electron cloud and the high-energy beam can give rise to numerous effects that can seriously degrade the accelerator performance. These effects range from vacuum degradation to collective beam instabilities and emittance blowup. Although electron-cloud effects were first observed two decades ago in a few proton storage rings, they have in recent years been widely observed and intensely studied in positron and proton rings. Electron-cloud diagnostics developed at the Advanced Photon Source enabled for the first time detailed, direct characterization of the electron-cloud properties in a positron and electron storage ring. From in situ measurements of the electron flux and energy distribution at the vacuum chamber wall, electron-cloud production mechanisms and details of the beam-cloud interaction can be inferred. A significant longitudinal variation of the electron cloud is also observed, due primarily to geometrical details of the vacuum chamber. Such experimental data can be used to provide realistic limits on key input parameters in modeling efforts, leading ultimately to greater confidence in predicting electron-cloud effects in future accelerators.

  18. Mining in the European Arctic

    NARCIS (Netherlands)

    van Dam, Karin; Scheepstra, Adriana; Gille, Johan; Stepien, Adam; Koivurova, Timo; Stepien, Adam; Koivurova, Timo; Kankaanpää, Paula

    The European Arctic has been recently experiencing an upsurge in mining activities. This is reflected in an on-going interest from the industry, regulators and the public. However, current and future prospects are highly sensitive to mineral price fluctuations. The EU is a major consumer and

  19. Arbitrarily shaped high-coherence electron bunches from cold atoms

    Science.gov (United States)

    McCulloch, A. J.; Sheludko, D. V.; Saliba, S. D.; Bell, S. C.; Junker, M.; Nugent, K. A.; Scholten, R. E.

    2011-10-01

    Ultrafast electron diffractive imaging of nanoscale objects such as biological molecules and defects in solid-state devices provides crucial information on structure and dynamic processes: for example, determination of the form and function of membrane proteins, vital for many key goals in modern biological science, including rational drug design. High brightness and high coherence are required to achieve the necessary spatial and temporal resolution, but have been limited by the thermal nature of conventional electron sources and by divergence due to repulsive interactions between the electrons, known as the Coulomb explosion. It has been shown that, if the electrons are shaped into ellipsoidal bunches with uniform density, the Coulomb explosion can be reversed using conventional optics, to deliver the maximum possible brightness at the target. Here we demonstrate arbitrary and real-time control of the shape of cold electron bunches extracted from laser-cooled atoms. The ability to dynamically shape the electron source itself and to observe this shape in the propagated electron bunch provides a remarkable experimental demonstration of the intrinsically high spatial coherence of a cold-atom electron source, and the potential for alleviation of electron-source brightness limitations due to Coulomb explosion.

  20. High-Power Electron Accelerators for Space (and other) Applications

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Dinh Cong [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lewellen, John W. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-05-23

    This is a presentation on high-power electron accelerators for space and other applications. The main points covered are: electron beams for space applications, new designs of RF accelerators, high-power high-electron mobility transistors (HEMT) testing, and Li-ion battery design. In summary, the authors have considered a concept of 1-MeV electron accelerator that can operate up to several seconds. This concept can be extended to higher energy to produce higher beam power. Going to higher beam energy requires adding more cavities and solid-state HEMT RF power devices. The commercial HEMT have been tested for frequency response and RF output power (up to 420 W). Finally, the authors are testing these HEMT into a resonant load and planning for an electron beam test in FY17.

  1. Approaching a Postcolonial Arctic

    DEFF Research Database (Denmark)

    Jensen, Lars

    2016-01-01

    This article explores different postcolonially configured approaches to the Arctic. It begins by considering the Arctic as a region, an entity, and how the customary political science informed approaches are delimited by their focus on understanding the Arctic as a region at the service...... of the contemporary neoliberal order. It moves on to explore how different parts of the Arctic are inscribed in a number of sub-Arctic nation-state binds, focusing mainly on Canada and Denmark. The article argues that the postcolonial can be understood as a prism or a methodology that asks pivotal questions to all...... approaches to the Arctic. Yet the postcolonial itself is characterised by limitations, not least in this context its lack of interest in the Arctic, and its bias towards conventional forms of representation in art. The article points to the need to develop a more integrated critique of colonial and neo...

  2. Development of an electron gun for high power CW electron linac

    International Nuclear Information System (INIS)

    Yamazaki, Yoshio; Nomura, Masahiro

    1994-01-01

    An electron gun launching high average current beam has been designed for the high power CW electron linac at PNC. A peak electron beam current of 400mA with beam energy 200keV is required from the buncher design. However its average current is very high(duty factor 20%), a mesh grid is not able to be used for current control because of heating up or melting of grid. Furthermore, the beam current have to be variable up to 400mA to match with downstream modules, especially the accelerating guides including recirculating system. We employed the electron gun with two aperture grids to control beam current. The dimension of the electrodes, electron trajectory, the size of beam radius, and gun emittance was simulated by EGUN. (author)

  3. Heat sinking of highly integrated photonic and electronic circuits

    NARCIS (Netherlands)

    van Rijn, M.B.J.; Smit, M.K.

    2017-01-01

    Dense integration of photonic and electronic circuits poses high requirements on thermal management. In this paper we present analysis of temperature distributions in PICs in InP membranes on top of a BiCMOS chip, which contain hot spots in both the photonic and the electronic layer (lasers, optical

  4. A high dutycycle low cost multichannel analyser for electron spectroscopy

    International Nuclear Information System (INIS)

    Norell, K.E.; Baltzer, P.

    1983-03-01

    A high dutycycle multichannel analyzer has been designed and used in time-of-flight electron spectroscopy. The memory capacity is 64k counts. The number of channels is 8192 with a time resolution of 100 ns. An oscilloscope is used to display the spectra synchronous with the counting. The unit has been built with standard electronic components. (author)

  5. Electron-optical design parameters for a high-resolution electron monochromator

    International Nuclear Information System (INIS)

    Tanaka, H.; Huebner, R.H.

    1976-01-01

    Detailed design parameters of a new, high-resolution electron monochromator are presented. The design utilizes a hemispherical filter as the energy-dispersing element and combines both cylindrical and aperture electrostatic lenses to accelerate, decelerate, transport, and focus the electron beam from the cathode to the interaction region

  6. High energy electron acceleration with PW-class laser system

    International Nuclear Information System (INIS)

    Nakanii, N.; Kondo, K.; Yabuuchi, T.; Tsuji, K.; Kimura, K.; Fukumochi, S.; Kashihara, M.; Tanimoto, T.; Nakamura, H.; Ishikura, T.; Kodama, R.; Mima, K.; Tanaka, K. A.; Mori, Y.; Miura, E.; Suzuki, S.; Asaka, T.; Yanagida, K.; Hanaki, H.; Kobayashi, T.

    2008-01-01

    We performed electron acceleration experiment with PW-class laser and a plasma tube, which was created by imploding a hollow polystyrene cylinder. In this experiment, electron energies in excess of 600 MeV have been observed. Moreover, the spectra of a comparatively high-density plasma ∼10 19 cm -3 had a bump around 10 MeV. Additionally, we performed the absolute sensitivity calibration of imaging plate for 1 GeV electrons from the injector Linac of Spring-8 in order to evaluate absolute number of GeV-class electrons in the laser acceleration experiment

  7. Evaluation of high-energy brachytherapy source electronic disequilibrium and dose from emitted electrons.

    Science.gov (United States)

    Ballester, Facundo; Granero, Domingo; Pérez-Calatayud, José; Melhus, Christopher S; Rivard, Mark J

    2009-09-01

    The region of electronic disequilibrium near photon-emitting brachytherapy sources of high-energy radionuclides (60Co, 137CS, 192Ir, and 169Yb) and contributions to total dose from emitted electrons were studied using the GEANT4 and PENELOPE Monte Carlo codes. Hypothetical sources with active and capsule materials mimicking those of actual sources but with spherical shape were examined. Dose contributions due to source photons, x rays, and bremsstrahlung; source beta-, Auger electrons, and internal conversion electrons; and water collisional kerma were scored. To determine if conclusions obtained for electronic equilibrium conditions and electron dose contribution to total dose for the representative spherical sources could be applied to actual sources, the 192Ir mHDR-v2 source model (Nucletron B.V., Veenendaal, The Netherlands) was simulated for comparison to spherical source results and to published data. Electronic equilibrium within 1% is reached for 60Co, 137CS, 192Ir, and 169Yb at distances greater than 7, 3.5, 2, and 1 mm from the source center, respectively, in agreement with other published studies. At 1 mm from the source center, the electron contributions to total dose are 1.9% and 9.4% for 60Co and 192Ir, respectively. Electron emissions become important (i.e., > 0.5%) within 3.3 mm of 60Co and 1.7 mm of 192Ir sources, yet are negligible over all distances for 137Cs and 169Yb. Electronic equilibrium conditions along the transversal source axis for the mHDR-v2 source are comparable to those of the spherical sources while electron dose to total dose contribution are quite different. Electronic equilibrium conditions obtained for spherical sources could be generalized to actual sources while electron contribution to total dose depends strongly on source dimensions, material composition, and electron spectra.

  8. Arctic Ocean Regional Climatology (NCEI Accession 0115771)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — To provide an improved oceanographic foundation and reference for multi-disciplinary studies of the Arctic Ocean, NCEI developed a new set of high-resolution...

  9. Engage in the Arctic Now or Risk Being Left Out in the Cold: Establishing a JIATF-High North

    Science.gov (United States)

    2010-05-03

    Qin, M. Manning, Z . Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller, eds., IPCC, 2007: Climate Change 2007: The Physical Science Basis...article, that “China has sent research vessels to the frozen north. A Chinese research ship, Snow Dragon , paid a surprise visit to Tuktoyuktuk in 1999 [a...with the Arctic Council. The ball has already begun rolling as other nations explore the methods that they will use to secure their interests in the

  10. Technical Training: ELEC-2005: Electronics in High Energy Physics

    CERN Multimedia

    Monique Duval

    2005-01-01

    CERN Technical Training 2005: Learning for the LHC! ELEC-2005: Electronics in High Energy Physics - Spring Term ELEC-2005 is a new course series on modern electronics, given by CERN physicists and engineers within the framework of the 2005 Technical Training Programme, in an extended format of the successful ELEC-2002 course series. This comprehensive course series is designed for people who are not electronics specialists, for example physicists, engineers and technicians working at or visiting the laboratory, who use or will use electronics in their present or future activities, in particular in the context of the LHC accelerator and experiments. ELEC-2005 is composed of four Terms: the Winter Term, Introduction to electronics in HEP, already took place; the next three Terms will run throughout the year: Spring Term: Integrated circuits and VLSI technology for physics (March, 6 lectures) - now open for registration Summer Term: System electronics for physics: Issues (May, 7 lectures) Autumn Term: Ele...

  11. Perturbation of an arctic soil microbial community by metal nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Niraj [Department of Biology, Queen' s University, Kingston, Ontario K7L 3N6 (Canada); Shah, Vishal [Department of Biology, Dowling College, Oakdale, NY 11769 (United States); Walker, Virginia K., E-mail: walkervk@queensu.ca [Department of Biology, Queen' s University, Kingston, Ontario K7L 3N6 (Canada); Department of Biology, School of Environmental Studies and Department of Microbiology and Immunology, Queen' s University, Kingston, Ontario K7L 3N6 (Canada)

    2011-06-15

    Highlights: {yields} Silver, copper and silica nanoparticles had an impact on arctic soil {yields} A microbial community toxicity indicator was developed {yields} Community surveys using pyrosequencing confirmed a shift in bacterial biodiversity {yields} Troublingly, silver nanoparticles were highly toxic to a plant beneficial bacterium - Abstract: Technological advances allowing routine nanoparticle (NP) manufacture have enabled their use in electronic equipment, foods, clothing and medical devices. Although some NPs have antibacterial activity, little is known about their environmental impact and there is no information on the influence of NPs on soil in the possibly vulnerable ecosystems of polar regions. The potential toxicity of 0.066% silver, copper or silica NPs on a high latitude (>78{sup o}N) soil was determined using community level physiological profiles (CLPP), fatty acid methyl ester (FAME) assays and DNA analysis, including sequencing and denaturing gradient gel electrophoresis (DGGE). The results of these different investigations were amalgamated in order to develop a community toxicity indicator, which revealed that of the three NPs examined, silver NPs could be classified as highly toxic to these arctic consortia. Subsequent culture-based studies confirmed that one of the community-identified plant-associating bacteria, Bradyrhizobium canariense, appeared to have a marked sensitivity to silver NPs. Thus, NP contamination of arctic soils particularly by silver NPs is a concern and procedures for mitigation and remediation of such pollution should be a priority for investigation.

  12. Perturbation of an arctic soil microbial community by metal nanoparticles

    International Nuclear Information System (INIS)

    Kumar, Niraj; Shah, Vishal; Walker, Virginia K.

    2011-01-01

    Highlights: → Silver, copper and silica nanoparticles had an impact on arctic soil → A microbial community toxicity indicator was developed → Community surveys using pyrosequencing confirmed a shift in bacterial biodiversity → Troublingly, silver nanoparticles were highly toxic to a plant beneficial bacterium - Abstract: Technological advances allowing routine nanoparticle (NP) manufacture have enabled their use in electronic equipment, foods, clothing and medical devices. Although some NPs have antibacterial activity, little is known about their environmental impact and there is no information on the influence of NPs on soil in the possibly vulnerable ecosystems of polar regions. The potential toxicity of 0.066% silver, copper or silica NPs on a high latitude (>78 o N) soil was determined using community level physiological profiles (CLPP), fatty acid methyl ester (FAME) assays and DNA analysis, including sequencing and denaturing gradient gel electrophoresis (DGGE). The results of these different investigations were amalgamated in order to develop a community toxicity indicator, which revealed that of the three NPs examined, silver NPs could be classified as highly toxic to these arctic consortia. Subsequent culture-based studies confirmed that one of the community-identified plant-associating bacteria, Bradyrhizobium canariense, appeared to have a marked sensitivity to silver NPs. Thus, NP contamination of arctic soils particularly by silver NPs is a concern and procedures for mitigation and remediation of such pollution should be a priority for investigation.

  13. Development techniques and electron optical studies of high voltage, high current electron guns

    International Nuclear Information System (INIS)

    Rangarajan, L.M.; Mahadevan, S.; Ramamurthi, S.S.

    1992-01-01

    The progress of the electron gun design, limiting to axially symmetric geometries is discussed here with a view to utilise such guns for electron accelerators. The mechanical design features leading to the physical configuration of the gun with stringent tolerances are outlined. Vacuum processing is done at pressures of 1.3x10 -5 Pa. The gun employs W-filament emitter or a cathode pellet with bombarder service. A water cooled compact faraday cup is used to measure the electron current. Electron gun geometries have been studied using the computer programme. The preveance of the gun is 0.7x10 -7 A/Vsup(1.5) at 80 kV. Developmental techniques of such pulsed electron guns are described. (author). 7 refs., 5 figs

  14. Seasonal formation of ikaite (caco 3 · 6h 2o) in saline spring discharge at Expedition Fiord, Canadian High Arctic: Assessing conditional constraints for natural crystal growth

    Science.gov (United States)

    Omelon, Christopher R.; Pollard, Wayne H.; Marion, Giles M.

    2001-05-01

    - Spring discharge at Expedition Fiord (Pollard et al., 1999) on Axel Heiberg Island in the Canadian High Arctic produces a variety of travertine forms in addition to a diverse collection of mineral precipitates. This paper focuses on clusters of thermally unstable crystals believed to be the mineral ikaite (CaCO 3 · 6H 2O) growing seasonally along two spring outflows at Colour Peak. This form of calcium carbonate mineral occurs along small sections of discharge outflow as white euhedral crystals up to 0.5 cm in length. Difficulty in sampling, storage and transport of the samples for analysis has hampered attempts to confirm the presence of ikaite by X-ray diffraction. However, various field observations and the remarkable instability of these crystals at normal ambient temperatures strengthens our argument. This paper provides a description of these particular CaCO 3 · 6H 2O crystals and their environmental surroundings, and attempts to determine the validity of ikaite precipitation at this site by theoretical geochemical modeling: these results are compared with other reported observations of ikaite to both understand their occurrence and help delineate their geochemical characteristics. It is believed that the restrictive combination of spring water chemistry and long periods of low temperatures characteristic of arctic climates are necessary for ikaite growth at this site. The fact that ikaite is not forming at a second group of saline springs 11 km away allows us to more specifically outline conditions controlling its presence.

  15. Turbulent Mixing and Vertical Heat Transfer in the Surface Mixed Layer of the Arctic Ocean: Implication of a Cross-Pycnocline High-Temperature Anomaly

    Science.gov (United States)

    Kawaguchi, Yusuke; Takeda, Hiroki

    2017-04-01

    This study focuses on the mixing processes in the vicinity of surface mixed layer (SML) of the Arctic Ocean. Turbulence activity and vertical heat transfer are quantitatively characterized in the Northwind Abyssal Plain, based on the RV Mirai Arctic cruise, during the transition from late summer to early winter 2014. During the cruise, noticeable storm events were observed, which came over the ship's location and contributed to the deepening of the SML. According to the ship-based microstructure observation, within the SML, the strong wind events produced enhanced dissipation rates of turbulent kinetic energy in the order of magnitude of ɛ = 10-6-10-4W kg-1. On thermal variance dissipation rate, χ increases toward the base of SML, reaching O(10-7) K2 s-1, resulting in vertical heat flux of O(10) W m-2. During the occasional energetic mixing events, the near-surface warm water was transferred downward and penetrated through the SML base, creating a cross-pycnocline high-temperature anomaly (CPHTA) at approximately 20-30 m depth. Near CPHTA, the vertical heat flux was anomalously magnified to O(10-100) W m-2. Following the fixed-point observation, in the regions of marginal and thick ice zones, the SML heat content was monitored using an autonomous drifting buoy, UpTempO. During most of the ice-covered period, the ocean-to-ice turbulent heat flux was dominant, rather than the diapycnal heat transfer across the SML bottom interface.

  16. Organic High Electron Mobility Transistors Realized by 2D Electron Gas.

    Science.gov (United States)

    Zhang, Panlong; Wang, Haibo; Yan, Donghang

    2017-09-01

    A key breakthrough in inorganic modern electronics is the energy-band engineering that plays important role to improve device performance or develop novel functional devices. A typical application is high electron mobility transistors (HEMTs), which utilizes 2D electron gas (2DEG) as transport channel and exhibits very high electron mobility over traditional field-effect transistors (FETs). Recently, organic electronics have made very rapid progress and the band transport model is demonstrated to be more suitable for explaining carrier behavior in high-mobility crystalline organic materials. Therefore, there emerges a chance for applying energy-band engineering in organic semiconductors to tailor their optoelectronic properties. Here, the idea of energy-band engineering is introduced and a novel device configuration is constructed, i.e., using quantum well structures as active layers in organic FETs, to realize organic 2DEG. Under the control of gate voltage, electron carriers are accumulated and confined at quantized energy levels, and show efficient 2D transport. The electron mobility is up to 10 cm 2 V -1 s -1 , and the operation mechanisms of organic HEMTs are also argued. Our results demonstrate the validity of tailoring optoelectronic properties of organic semiconductors by energy-band engineering, offering a promising way for the step forward of organic electronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Secondary electron spectroscopy and Auger microscopy at high spatial resolution. Application to scanning electron microscopy

    International Nuclear Information System (INIS)

    Le Gressus, Claude; Massignon, Daniel; Sopizet, Rene

    1979-01-01

    Secondary electron spectroscopy (SES), Auger electron spectroscopy (AES) and electron energy loss spectroscopy (ELS) are combined with ultra high vacuum scanning microscopy (SEM) for surface analysis at high spatial resolution. Reliability tests for the optical column for the vacuum and for the spectrometer are discussed. Furthermore the sensitivity threshold in AES which is compatible with a non destructive surface analysis at high spatial resolution is evaluated. This combination of all spectroscopies is used in the study of the beam damage correlated with the well known secondary electron image (SEI) darkening still observed in ultra high vacuum. The darkening is explained as a bulk decontamination of the sample rather than as a surface contamination from the residual vacuum gas [fr

  18. Treatment of basal cell epithelioma with high energy electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Ogawa, Y. (Hyogo-ken Cancer Center, Kobe (Japan)); Kumano, M.; Kumano, K.

    1981-11-01

    Thirty patients with basal cell epithelioma received high energy electron beam therapy. They were irradiated with a dose ranging from 4,800 rad (24 fractions, 35 days) to 12,000 rad (40 fractions, 57 days). Tumors disappeared in all cases. These were no disease-related deaths; in one patient there was recurrence after 2 years. We conclude that radiotherapy with high energy electron beam is very effective in the treatment of basal cell epithelioma.

  19. New initiatives for producing high current electron accelerators

    International Nuclear Information System (INIS)

    Faehl, R.J.; Keinigs, R.K.; Pogue, E.W.

    1996-01-01

    New classes of compact electron accelerators able to deliver multi-kiloamperes of pulsed 10-50 MeV electron beams are being studied. One class is based upon rf linac technology with dielectric-filled cavities. For materials with ε/ε o >>1, the greatly increased energy storage permits high current operation. The second type is a high energy injected betatron. Circulating current limits scale as Β 2 γ 3

  20. Optical Thermal Characterization Enables High-Performance Electronics Applications

    Energy Technology Data Exchange (ETDEWEB)

    2016-02-01

    NREL developed a modeling and experimental strategy to characterize thermal performance of materials. The technique provides critical data on thermal properties with relevance for electronics packaging applications. Thermal contact resistance and bulk thermal conductivity were characterized for new high-performance materials such as thermoplastics, boron-nitride nanosheets, copper nanowires, and atomically bonded layers. The technique is an important tool for developing designs and materials that enable power electronics packaging with small footprint, high power density, and low cost for numerous applications.

  1. Atmospheric transport of pollution to the Arctic

    International Nuclear Information System (INIS)

    Iversen, T.

    1984-01-01

    If the atmospheric processes are assumed to be nearly adiabatic, the conclusion is that the possible source areas of Arctic air pollution detected at ground level have to be situated in areas with almost the same temperature as observed in the Arctic itself. Sources south of the polar front system can only contribute to high-altitude (or upper level) Arctic pollution. The amplitude and phase of long, planetary waves are important since they determine the position of the polar front, and provide conditions for meridional transport of air at certain longitudes

  2. High harmonic terahertz confocal gyrotron with nonuniform electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Wenjie; Guan, Xiaotong; Yan, Yang [THz Research Center, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2016-01-15

    The harmonic confocal gyrotron with nonuniform electron beam is proposed in this paper in order to develop compact and high power terahertz radiation source. A 0.56 THz third harmonic confocal gyrotron with a dual arc section nonuniform electron beam has been designed and investigated. The studies show that confocal cavity has extremely low mode density, and has great advantage to operate at high harmonic. Nonuniform electron beam is an approach to improve output power and interaction efficiency of confocal gyrotron. A dual arc beam magnetron injection gun for designed confocal gyrotron has been developed and presented in this paper.

  3. Survey of potential electronic applications of high temperature superconductors

    International Nuclear Information System (INIS)

    Hammond, R.B.; Bourne, L.C.

    1991-01-01

    In this paper the authors present a survey of the potential electronic applications of high temperature superconductor (HTSC) thin films. During the past four years there has been substantial speculation on this topic. The authors will cover only a small fraction of the potential electronic applications that have been identified. Their treatment is influenced by the developments over the past few years in materials and device development and in market analysis. They present their view of the most promising potential applications. Superconductors have two important properties that make them attractive for electronic applications. These are (a) low surface resistance at high frequencies, and (b) the Josephson effect

  4. High-voltage pulse generator for electron gun power supply

    International Nuclear Information System (INIS)

    Korenev, S.A.; Enchevich, I.B.; Mikhov, M.K.

    1987-01-01

    High-voltage pulse generator with combined capacitive and inductive energy storages for electron gun power supply is described. Hydrogen thyratron set in a short magnetic lense is a current breaker. Times of current interruption in thyratrons are in the range from 100 to 300 ns. With 1 kV charging voltage of capacitive energy storage 25 kV voltage pulse is obtained in the load. The given high-voltage pulse generator was used for supply of an electron gun generating 10-30 keV low-energy electron beam

  5. Late Holocene climate and chemical change at high latitudes: case studies from contaminated sites in subarctic and arctic Canada

    Science.gov (United States)

    Galloway, Jennifer M.; Cooney, Darryl; Crann, Carley; Falck, Hendrik; Howell, Dana; Jamieson, Heather; Macumber, Andrew; Nasser, Nawaf; Palmer, Michael; Patterson, R. Timothy; Parsons, Michael; Roe, Helen M.; Sanei, Hamed; Spence, Christopher; Stavinga, Drew; Swindles, Graeme T.

    2015-04-01

    Climate variability is occurring at unprecedented rates in northern regions of the Earth, yet little is known about the nature of this variability or its influence on chemical cycling in the environment, particularly in areas with a legacy of contamination from past resource development. We use a paleolimnological approach to reconstruct climate and chemical change over centuries and millennia at two sites in the mineral-rich Slave Geologic Province in Northern Canada heavily impacted by gold mining. Such an approach is necessary to define the cumulative effects of climate change on metal loading and can be used to define anthropogenic release of contaminants to support policy and regulation due to a paucity of long-term monitoring data. The Seabridge Gold Inc. Courageous Lake project is a gold exploration project 240 km north of Yellowknife in the central Northwest Territories, Arctic Canada. Mining operations took place within the claim area at the Tundra (1964-1968) and Salmita (1983-1987) mines. Giant Mine is located in the subarctic near the City of Yellowknife and mining at this site represents the longest continuous gold mining operation in Canada (1938 to 2002). Due to the refractory mineralogy of ore, gold was extracted from arsenopyrite by roasting, which resulted in release of substantial quantities of highly toxic arsenic trioxide to the environment. Arsenic (As) is also naturally elevated at these sites due its occurrence in Yellowknife Supergroup greenstone belts and surficial geologic deposits. To attempt to distinguish between geogenic and anthropogenic sources of As and characterize the role of climate change on metalloid mobility we used a freeze coring technology to capture lake sediments from the properties. Sediments were analyzed for sedimentary grain size and bulk geochemistry using ICP-MS to reconstruct climate and chemical change. Micropaleontological analyses are on-going. Interpretations of the physical, chemical, and biological archive

  6. Impact of electron-electron Coulomb interaction on the high harmonic generation process in graphene

    Science.gov (United States)

    Avetissian, H. K.; Mkrtchian, G. F.

    2018-03-01

    Generation of high harmonics in a monolayer graphene initiated by a strong coherent radiation field, taking into account electron-electron Coulomb interaction, is investigated. A microscopic theory describing the nonlinear optical response of graphene is developed. The Coulomb interaction of electrons is treated in the scope of dynamic Hartree-Fock approximation. The closed set of integrodifferential equations for the single-particle density matrix of a graphene quantum structure is solved numerically. The obtained solutions show the significance of many-body Coulomb interaction on the high harmonic generation process in graphene.

  7. Arctic pollution: How much is too much

    Energy Technology Data Exchange (ETDEWEB)

    An overview is presented of the problems of pollution in the Arctic. Pollution from lower latitudes is carried into the Arctic by atmospheric circulation and ocean currents. Contamination of snow, waters and organisms with imported pollutants has appeared in the past few decades and appears to be increasing. Arctic ecosystems show indications of being much more susceptible to biological damage at low levels of pollutants than higher-energy ecosystems in temperate latitudes, and many Arctic organisms become accumulators and concentrators of organic pollutants and toxic metals. Arctic haze is 20 to 40 times as high in winter as in summer and has been found to consist of particles of largely industrial origin, mostly soot, hydrocarbons and sulphates. Dramatic declines in stratospheric ozone have been apparent over Antarctica, and a similar but less intense depletion is appearing over the Arctic. Toxic compounds, particularly organochlorines and some heavy metals, have been found in worrying amounts in snow, water and organisms in Arctic North America, Greenland and Svalbard. Radioactive contamination was widespread during atmospheric testing of nuclear weapons during the 1960s and 1970s, and the comparatively small amount of radiation released by the Chernobyl accident had greatest effect in northern Scandinavia. 4 figs.

  8. High energy gain electron beam acceleration by 100TW laser

    International Nuclear Information System (INIS)

    Kotaki, Hideyuki; Kando, Masaki; Kondo, Shuji; Hosokai, Tomonao; Kanazawa, Shuhei; Yokoyama, Takashi; Matoba, Toru; Nakajima, Kazuhisa

    2001-01-01

    A laser wakefield acceleration experiment using a 100TW laser is planed at JAERI-Kansai. High quality and short pulse electron beams are necessary to accelerate the electron beam by the laser. Electron beam - laser synchronization is also necessary. A microtron with a photocathode rf-gun was prepared as a high quality electron injector. The quantum efficiency (QE) of the photocathode of 2x10 -5 was obtained. A charge of 100pC from the microtron was measured. The emittance and pulse width of the electron beam was 6π mm-mrad and 10ps, respectively. In order to produce a short pulse electron beam, and to synchronize between the electron beam and the laser pulse, an inverse free electron laser (IFEL) is planned. One of problems of LWFA is the short acceleration length. In order to overcome the problem, a Z-pinch plasma waveguide will be prepared as a laser wakefield acceleration tube for 1 GeV acceleration. (author)

  9. Temporal and spatial distribution of high energy electrons at Jupiter

    Science.gov (United States)

    Jun, I.; Garrett, H. B.; Ratliff, J. M.

    2003-04-01

    Measurements of the high energy, omni-directional electron environment by the Galileo spacecraft Energetic Particle Detector (EPD) were used to study the high energy electron environment in the Jovian magnetosphere, especially in the region between 8 to 18 Rj (1 Rj = 1 Jovian radius = 71,400 km). 10-minute averages of the EPD data collected between Jupiter orbit insertion (JOI) in 1995 and the orbit number 33 (I33) in 2002 form an extensive dataset, which has been extremely useful to observe temporal and spatial variability of the Jovian high energy electron environment. The count rates of the EPD electron channels (0.174, 0.304, 0.527, 1.5, 2.0, and 11 MeV) were grouped into 0.5 Rj or 0.5 L bins and analyzed statistically. The results indicate that: (1) a log-normal Gaussian distribution well describes the statistics of the high energy electron environment (for example, electron differential fluxes) in the Jovian magnetosphere, in the region studied here; (2) the high energy electron environments inferred by the Galileo EPD measurements are in a close agreement with the data obtained using the Divine model, which was developed more than 30 years ago from Pioneer 10, 11 and Voyager 1, 2 data; (3) the data are better organized when plotted against magnetic radial parameter L than Rj; (4) the standard deviations of the 0.174, 0.304, 0.527 MeV channel count rates are larger than those of the 1.5, 2.0, 11 MeV count rates in 12 Rj. These observations are very helpful to understand short- and long-term, and local variability of the Jovian high energy electron environment, and are discussed in detail.

  10. Development of a high power free-electron laser

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jong Min; Lee, Byung Chul; Kim, Sun Kook; Jung, Yung Wook; Cho, Sung Oh [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1995-01-01

    A millimeter-wave free electron laser (FEL) driven by a recirculating electrostatic accelerator has been developed. The wavelength of the FEL is tunable in the range of 3 - 12 mm by tuning the energy of the electron beam. The output power is estimated to be 1 kW. The electrostatic accelerator is composed of high-current electron gun, acceleration tube, high-voltage generator, high-voltage terminal, deceleration tube, electron collator, and vacuum pumps. Two types of LaB{sub 6}-based thermionic electron guns (triode gun and diode gun) and their power supplies have been developed. The voltage of the guns is 30 kV and the output current is - 2 A. A beam-focusing planar undulator and a permanent-magnet helical undulator have been developed and 3D trajectories of electron beam in the undulators have been calculated to find optimal input condition of electron beam. 135 figs, 15 pix, 17 tabs, 98 refs. (Author).

  11. Development of a high power free-electron laser

    International Nuclear Information System (INIS)

    Lee, Jong Min; Lee, Byung Chul; Kim, Sun Kook; Jung, Yung Wook; Cho, Sung Oh

    1995-01-01

    A millimeter-wave free electron laser (FEL) driven by a recirculating electrostatic accelerator has been developed. The wavelength of the FEL is tunable in the range of 3 - 12 mm by tuning the energy of the electron beam. The output power is estimated to be 1 kW. The electrostatic accelerator is composed of high-current electron gun, acceleration tube, high-voltage generator, high-voltage terminal, deceleration tube, electron collator, and vacuum pumps. Two types of LaB 6 -based thermionic electron guns (triode gun and diode gun) and their power supplies have been developed. The voltage of the guns is 30 kV and the output current is - 2 A. A beam-focusing planar undulator and a permanent-magnet helical undulator have been developed and 3D trajectories of electron beam in the undulators have been calculated to find optimal input condition of electron beam. 135 figs, 15 pix, 17 tabs, 98 refs. (Author)

  12. Electron transfer and decay processes of highly charged iodine ions

    International Nuclear Information System (INIS)

    Sakaue, Hiroyuki A.; Danjo, Atsunori; Hosaka, Kazumoto

    2005-01-01

    In the present experimental work we have investigated multi-electron transfer processes in I q+ (q=10, 15, 20 and 25) + Ne, Ar, Kr and Xe collisions at 1.5q keV energy. The branching ratios between Auger and radiative decay channels have been measured in decay processes of multiply excited states formed by multi-electron transfer collisions. It has been shown that, in all the multi-electron transfer processes investigated, the Auger decays are far dominant over the radiative decay processes and the branching ratios are clearly characterized by the average principal quantum number of the initial excited states of projectile ions. We could express the branching ratios in high Rydberg states formed in multi-electron transfer processes by using the decay probability of one Auger electron emission. (author)

  13. Laboratory design for high-performance electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    O' Keefe, Michael A.; Turner, John H.; Hetherington, Crispin J.D.; Cullis, A.G.; Carragher, Bridget; Jenkins, Ron; Milgrim, Julie; Milligan,Ronald A.; Potter, Clinton S.; Allard, Lawrence F.; Blom, Douglas A.; Degenhardt, Lynn; Sides, William H.

    2004-04-23

    Proliferation of electron microscopes with field emission guns, imaging filters and hardware spherical aberration correctors (giving higher spatial and energy resolution) has resulted in the need to construct special laboratories. As resolutions improve, transmission electron microscopes (TEMs) and scanning transmission electron microscopes (STEMs) become more sensitive to ambient conditions. State-of-the-art electron microscopes require state-of-the-art environments, and this means careful design and implementation of microscope sites, from the microscope room to the building that surrounds it. Laboratories have been constructed to house high-sensitive instruments with resolutions ranging down to sub-Angstrom levels; we present the various design philosophies used for some of these laboratories and our experiences with them. Four facilities are described: the National Center for Electron Microscopy OAM Laboratory at LBNL; the FEGTEM Facility at the University of Sheffield; the Center for Integrative Molecular Biosciences at TSRI; and the Advanced Microscopy Laboratory at ORNL.

  14. The Arctic Turn

    DEFF Research Database (Denmark)

    Rahbek-Clemmensen, Jon

    2018-01-01

    In October 2006, representatives of the Arctic governments met in Salekhard in northern Siberia for the biennial Arctic Council ministerial meeting to discuss how the council could combat regional climate change, among other issues. While most capitals were represented by their foreign minister......, a few states – Canada, Denmark, and the United States – sent other representatives. There was nothing unusual about the absence of Per Stig Møller, the Danish foreign minister – a Danish foreign minister had only once attended an Arctic Council ministerial meeting (Arctic Council 2016). Møller......’s nonappearance did, however, betray the low status that Arctic affairs had in the halls of government in Copenhagen. Since the end of the Cold War, where Greenland had helped tie Denmark and the US closer together due to its geostrategically important position between North America and the Soviet Union, Arctic...

  15. Collaboration across the Arctic

    DEFF Research Database (Denmark)

    Huppert, Verena Gisela; Chuffart, Romain François R.

    2017-01-01

    The Arctic is witnessing the rise of a new paradigm caused by an increase in pan-Arctic collaborations which co-exist with the region’s traditional linkages with the South. Using an analysis of concrete examples of regional collaborations in the Arctic today in the fields of education, health...... and infrastructure, this paper questions whether pan-Arctic collaborations in the Arctic are more viable than North-South collaborations, and explores the reasons behind and the foreseeable consequences of such collaborations. It shows that the newly emerging East-West paradigm operates at the same time...... as the traditional North-South paradigm, with no signs of the East-West paradigm being more viable in the foreseeable future. However, pan-Arctic collaboration, both due to pragmatic reasons and an increased awareness of similarities, is likely to increase in the future. The increased regionalization process...

  16. Changing Arctic Ocean freshwater pathways.

    Science.gov (United States)

    Morison, James; Kwok, Ron; Peralta-Ferriz, Cecilia; Alkire, Matt; Rigor, Ignatius; Andersen, Roger; Steele, Mike

    2012-01-04

    Freshening in the Canada basin of the Arctic Ocean began in the 1990s and continued to at least the end of 2008. By then, the Arctic Ocean might have gained four times as much fresh water as comprised the Great Salinity Anomaly of the 1970s, raising the spectre of slowing global ocean circulation. Freshening has been attributed to increased sea ice melting and contributions from runoff, but a leading explanation has been a strengthening of the Beaufort High--a characteristic peak in sea level atmospheric pressure--which tends to accelerate an anticyclonic (clockwise) wind pattern causing convergence of fresh surface water. Limited observations have made this explanation difficult to verify, and observations of increasing freshwater content under a weakened Beaufort High suggest that other factors must be affecting freshwater content. Here we use observations to show that during a time of record reductions in ice extent from 2005 to 2008, the dominant freshwater content changes were an increase in the Canada basin balanced by a decrease in the Eurasian basin. Observations are drawn from satellite data (sea surface height and ocean-bottom pressure) and in situ data. The freshwater changes were due to a cyclonic (anticlockwise) shift in the ocean pathway of Eurasian runoff forced by strengthening of the west-to-east Northern Hemisphere atmospheric circulation characterized by an increased Arctic Oscillation index. Our results confirm that runoff is an important influence on the Arctic Ocean and establish that the spatial and temporal manifestations of the runoff pathways are modulated by the Arctic Oscillation, rather than the strength of the wind-driven Beaufort Gyre circulation.

  17. Effects of ambient versus reduced UV-B radiation on high arctic ¤Salix arctica¤ assessed by measurements and calculations of chlorophyll a fluorescence parameters from fluorescence transients

    DEFF Research Database (Denmark)

    Albert, K.R.; Mikkelsen, Teis Nørgaard; Ro-Poulsen, H.

    2005-01-01

    A UV-B exclusion-experiment was conducted in the high arctic Zackenberg, NE Greenland, in which Salix arctica leaves during most of the growing season were fixed perpendicular to the solar zenith angle, thereby receiving maximal solar radiation. Covered with Teflon and Mylar foil, the leaves...

  18. Stratospheric ozone depletion: high arctic tundra plant species from Svalbard are not affected by enhanced UV-B after 7 years of UV-B supplementation in the field.

    NARCIS (Netherlands)

    Rozema, J.; Boelen, P.; Blokker, P.; Callaghan, T.V.; Solheim, B.; Zielke, M.

    2006-01-01

    The response of tundra plants to enhanced UV-B radiation simulating 15 and 30% ozone depletion was studied at two high arctic sites (Isdammen and Adventdalen, 78° N, Svalbard).The set-up of the UV-B supplementation systems is described, consisting of large and small UV lamp arrays, installed in 1996

  19. Electron capture by highly charged ions from surfaces and gases

    Energy Technology Data Exchange (ETDEWEB)

    Allen, F.

    2008-01-11

    In this study highly charged ions produced in Electron Beam Ion Traps are used to investigate electron capture from surfaces and gases. The experiments with gas targets focus on spectroscopic measurements of the K-shell x-rays emitted at the end of radiative cascades following electron capture into Rydberg states of Ar{sup 17+} and Ar{sup 18+} ions as a function of collision energy. The ions are extracted from an Electron Beam Ion Trap at an energy of 2 keVu{sup -1}, charge-selected and then decelerated down to 5 eVu{sup -1} for interaction with an argon gas target. For decreasing collision energies a shift to electron capture into low orbital angular momentum capture states is observed. Comparative measurements of the K-shell x-ray emission following electron capture by Ar{sup 17+} and Ar{sup 18+} ions from background gas in the trap are made and a discrepancy in the results compared with those from the extraction experiments is found. Possible explanations are discussed. For the investigation of electron capture from surfaces, highly charged ions are extracted from an Electron Beam Ion Trap at energies of 2 to 3 keVu{sup -1}, charge-selected and directed onto targets comprising arrays of nanoscale apertures in silicon nitride membranes. The highly charged ions implemented are Ar{sup 16+} and Xe{sup 44+} and the aperture targets are formed by focused ion beam drilling in combination with ion beam assisted thin film deposition, achieving hole diameters of 50 to 300 nm and aspect ratios of 1:5 to 3:2. After transport through the nanoscale apertures the ions pass through an electrostatic charge state analyzer and are detected. The percentage of electron capture from the aperture walls is found to be much lower than model predictions and the results are discussed in terms of a capillary guiding mechanism. (orig.)

  20. Electron capture by highly charged ions from surfaces and gases

    International Nuclear Information System (INIS)

    Allen, F.

    2008-01-01

    In this study highly charged ions produced in Electron Beam Ion Traps are used to investigate electron capture from surfaces and gases. The experiments with gas targets focus on spectroscopic measurements of the K-shell x-rays emitted at the end of radiative cascades following electron capture into Rydberg states of Ar 17+ and Ar 18+ ions as a function of collision energy. The ions are extracted from an Electron Beam Ion Trap at an energy of 2 keVu -1 , charge-selected and then decelerated down to 5 eVu -1 for interaction with an argon gas target. For decreasing collision energies a shift to electron capture into low orbital angular momentum capture states is observed. Comparative measurements of the K-shell x-ray emission following electron capture by Ar 17+ and Ar 18+ ions from background gas in the trap are made and a discrepancy in the results compared with those from the extraction experiments is found. Possible explanations are discussed. For the investigation of electron capture from surfaces, highly charged ions are extracted from an Electron Beam Ion Trap at energies of 2 to 3 keVu -1 , charge-selected and directed onto targets comprising arrays of nanoscale apertures in silicon nitride membranes. The highly charged ions implemented are Ar 16+ and Xe 44+ and the aperture targets are formed by focused ion beam drilling in combination with ion beam assisted thin film deposition, achieving hole diameters of 50 to 300 nm and aspect ratios of 1:5 to 3:2. After transport through the nanoscale apertures the ions pass through an electrostatic charge state analyzer and are detected. The percentage of electron capture from the aperture walls is found to be much lower than model predictions and the results are discussed in terms of a capillary guiding mechanism. (orig.)

  1. Ultra high energy electrons powered by pulsar rotation.

    Science.gov (United States)

    Mahajan, Swadesh; Machabeli, George; Osmanov, Zaza; Chkheidze, Nino

    2013-01-01

    A new mechanism of particle acceleration, driven by the rotational slow down of the Crab pulsar, is explored. The rotation, through the time dependent centrifugal force, can efficiently excite unstable Langmuir waves in the electron-positron (hereafter e(±)) plasma of the star magnetosphere. These waves, then, Landau damp on electrons accelerating them in the process. The net transfer of energy is optimal when the wave growth and the Landau damping times are comparable and are both very short compared to the star rotation time. We show, by detailed calculations, that these are precisely the conditions for the parameters of the Crab pulsar. This highly efficient route for energy transfer allows the electrons in the primary beam to be catapulted to multiple TeV (~ 100 TeV) and even PeV energy domain. It is expected that the proposed mechanism may, unravel the puzzle of the origin of ultra high energy cosmic ray electrons.

  2. Ion induced high energy electron emission from copper

    Energy Technology Data Exchange (ETDEWEB)

    Ruano, G. [Instituto de Desarrollo Tecnologico para la Industria Quimica, Consejo Nacional de Investigaciones Cientificas y Tecnicas and Universidad Nacional del Litoral Gueemes 3450 CC 91, 3000 Santa Fe (Argentina)], E-mail: gdruano@ceride.gov.ar; Ferron, J. [Instituto de Desarrollo Tecnologico para la Industria Quimica, Consejo Nacional de Investigaciones Cientificas y Tecnicas and Universidad Nacional del Litoral Gueemes 3450 CC 91, 3000 Santa Fe (Argentina); Departamento de Ingenieria de Materiales, Facultad de Ingenieria Quimica, Consejo Nacional de Investigaciones Cientificas y Tecnicas and Universidad Nacional del Litoral Gueemes 3450 CC 91, 3000 Santa Fe (Argentina)

    2008-11-15

    We present measurements of secondary electron emission from Cu induced by low energy bombardment (1-5 keV) of noble gas (He{sup +}, Ne{sup +} and Ar{sup +}) and Li{sup +} ions. We identify different potential and kinetic mechanisms and find the presence of high energetic secondary electrons for a couple of ion-target combinations. In order to understand the presence of these fast electrons we need to consider the Fermi shuttle mechanism and the different ion neutralization efficiencies.

  3. Seasonal evolution of the effective thermal conductivity of the snow and the soil in high Arctic herb tundra at Bylot Island, Canada

    Science.gov (United States)

    Domine, Florent; Barrere, Mathieu; Sarrazin, Denis

    2016-11-01

    The values of the snow and soil thermal conductivity, ksnow and ksoil, strongly impact the thermal regime of the ground in the Arctic, but very few data are available to test model predictions for these variables. We have monitored ksnow and ksoil using heated needle probes at Bylot Island in the Canadian High Arctic (73° N, 80° W) between July 2013 and July 2015. Few ksnow data were obtained during the 2013-2014 winter, because little snow was present. During the 2014-2015 winter ksnow monitoring at 2, 12 and 22 cm heights and field observations show that a depth hoar layer with ksnow around 0.02 W m-1 K-1 rapidly formed. At 12 and 22 cm, wind slabs with ksnow around 0.2 to 0.3 W m-1 K-1 formed. The monitoring of ksoil at 10 cm depth shows that in thawed soil ksoil was around 0.7 W m-1 K-1, while in frozen soil it was around 1.9 W m-1 K-1. The transition between both values took place within a few days, with faster thawing than freezing and a hysteresis effect evidenced in the thermal conductivity-liquid water content relationship. The fast transitions suggest that the use of a bimodal distribution of ksoil for modelling may be an interesting option that deserves further testing. Simulations of ksnow using the snow physics model Crocus were performed. Contrary to observations, Crocus predicts high ksnow values at the base of the snowpack (0.12-0.27 W m-1 K-1) and low ones in its upper parts (0.02-0.12 W m-1 K-1). We diagnose that this is because Crocus does not describe the large upward water vapour fluxes caused by the temperature gradient in the snow and soil. These fluxes produce mass transfer between the soil and lower snow layers to the upper snow layers and the atmosphere. Finally, we discuss the importance of the structure and properties of the Arctic snowpack on subnivean life, as species such as lemmings live under the snow most of the year and must travel in the lower snow layer in search of food.

  4. Deepened winter snow increases stem growth and alters stem δ13C and δ15N in evergreen dwarf shrub Cassiope tetragona in high-arctic Svalbard tundra

    International Nuclear Information System (INIS)

    Blok, Daan; Michelsen, Anders; Elberling, Bo; Weijers, Stef; Löffler, Jörg; Welker, Jeffrey M; Cooper, Elisabeth J

    2015-01-01

    Deeper winter snow is hypothesized to favor shrub growth and may partly explain the shrub expansion observed in many parts of the arctic during the last decades, potentially triggering biophysical feedbacks including regional warming and permafrost thawing. We experimentally tested the effects of winter snow depth on shrub growth and ecophysiology by measuring stem length and stem hydrogen (δ 2 H), carbon (δ 13 C), nitrogen (δ 15 N) and oxygen (δ 18 O) isotopic composition of the circumarctic evergreen dwarf shrub Cassiope tetragona growing in high-arctic Svalbard, Norway. Measurements were carried out on C. tetragona individuals sampled from three tundra sites, each representing a distinct moisture regime (dry heath, meadow, moist meadow). Individuals were sampled along gradients of experimentally manipulated winter snow depths in a six-year old snow fence experiment: in ambient (c. 20 cm), medium (c. 100 cm), and deep snow (c. 150 cm) plots. The deep-snow treatment consistently and significantly increased C. tetragona growth during the 2008–2011 manipulation period compared to growth in ambient-snow plots. Stem δ 15 N and stem N concentration values were significantly higher in deep-snow individuals compared to individuals growing in ambient-snow plots during the course of the experiment, suggesting that soil N-availability was increased in deep-snow plots as a result of increased soil winter N mineralization. Although inter-annual growing season-precipitation δ 2 H and stem δ 2 H records closely matched, snow depth did not change stem δ 2 H or δ 18 O, suggesting that water source usage by C. tetragona was unaltered. Instead, the deep insulating snowpack may have protected C. tetragona shrubs against frost damage, potentially compensating the detrimental effects of a shortened growing season and associated phenological delay on growth. Our findings suggest that an increase in winter precipitation in the High Arctic, as predicted by climate models, has

  5. High activity and low temperature optima of extracellular enzymes in Arctic sediments: implications for carbon cycling by heterotrophic microbial communities

    DEFF Research Database (Denmark)

    Arnosti, C.; Jørgensen, BB

    2003-01-01

    The rate of the initial step in microbial remineralization of organic carbon, extracellular enzymatic hydrolysis, was investigated as a function of temperature in permanently cold sediments from 2 fjords on the west coast of Svalbard (Arctic Ocean). We used 4 structurally distinct polysaccharides...... hydrolysis in order to determine the relative temperature responses of the initial and terminal steps in microbial remineralization of carbon. The temperature optimum of sulfate reduction, 21degreesC, was considerably lower than previous reports of sulfate reduction in marine sediments, but is consistent...... with recent studies of psychrophilic sulfate reducers isolated from Svalbard sediments. A calculation of potential carbon flow into the microbial food chain demonstrated that the activity of just one type of polysaccharide-hydrolyzing enzyme could in theory supply 21 to 100% of the carbon consumed via sulfate...

  6. Effects of temperature on growth of four high Arctic soil fungi in a three-phase system

    Energy Technology Data Exchange (ETDEWEB)

    Widden, P [Concordia Univ., Montreal; Parkinson, D

    1978-04-01

    The effect of temperature on the growth of Chrysosporium pannorum, Cylindrocarpon sp., Penicillium janthinellum, and Phoma herbarum, isolated from tundra soils, was studied. The growth in two systems, glucose-mineral agar plates and sand, moistened with glucose-mineral broth, was compared. All isolates showed an exponential increase in mass (measured as protein increase) in sand and a linear rate of extension on agar. Radial increase on agar was shown not to be a good index of growth in sand. Trends in growth rates in the sand cultures indicated that all four fungi can grow at low temperatures. The growth rate for Penicillium janthinellum at 15/sup 0/C was higher than at 20/sup 0/C, and Cylindrocarpon sp. and Phoma herbarum had higher growth rates at 2.5/sup 0/C than at 5/sup 0/C. These data suggest that there may be some adaptation by these fungi to growth in Arctic regions.

  7. High activity and low temperature optima of extracellular enzymes in Arctic sediments: implications for carbon cycling by heterotrophic microbial communities

    DEFF Research Database (Denmark)

    Arnosti, C.; Jørgensen, BB

    2003-01-01

    (chondroitin sulfate, fucoidan, xylan and pullulan) to determine the temperature-activity responses of hydrolysis of a related class of compounds. All 4 enzyme activities showed similarly low temperature optima in the range of 15 to 18degreesC. These temperature optima are considerably lower than most previous......The rate of the initial step in microbial remineralization of organic carbon, extracellular enzymatic hydrolysis, was investigated as a function of temperature in permanently cold sediments from 2 fjords on the west coast of Svalbard (Arctic Ocean). We used 4 structurally distinct polysaccharides...... reports of temperature optima for enzyme activities in marine sediments. At 0degreesC, close to the in situ temperature, these enzyme activities achieved 13 to 38% of their rates at optimum temperatures. In one experiment, sulfate reduction rates were measured in parallel with extracellular enzymatic...

  8. Arctic wind energy

    Energy Technology Data Exchange (ETDEWEB)

    Peltola, E. [Kemijoki Oy (Finland); Holttinen, H.; Marjaniemi, M. [VTT Energy, Espoo (Finland); Tammelin, B. [Finnish Meteorological Institute, Helsinki (Finland)

    1998-12-31

    Arctic wind energy research was aimed at adapting existing wind technologies to suit the arctic climatic conditions in Lapland. Project research work included meteorological measurements, instrument development, development of a blade heating system for wind turbines, load measurements and modelling of ice induced loads on wind turbines, together with the development of operation and maintenance practices in arctic conditions. As a result the basis now exists for technically feasible and economically viable wind energy production in Lapland. New and marketable products, such as blade heating systems for wind turbines and meteorological sensors for arctic conditions, with substantial export potential, have also been developed. (orig.)

  9. Arctic wind energy

    International Nuclear Information System (INIS)

    Peltola, E.; Holttinen, H.; Marjaniemi, M.; Tammelin, B.

    1998-01-01

    Arctic wind energy research was aimed at adapting existing wind technologies to suit the arctic climatic conditions in Lapland. Project research work included meteorological measurements, instrument development, development of a blade heating system for wind turbines, load measurements and modelling of ice induced loads on wind turbines, together with the development of operation and maintenance practices in arctic conditions. As a result the basis now exists for technically feasible and economically viable wind energy production in Lapland. New and marketable products, such as blade heating systems for wind turbines and meteorological sensors for arctic conditions, with substantial export potential, have also been developed. (orig.)

  10. Proposal to detect an emission of unusual super-high energy electrons in electron storage rings

    Directory of Open Access Journals (Sweden)

    Da-peng Qian

    2014-01-01

    Full Text Available According to an extended Lorentz–Einstein mass formula taken into the uncertainty principle, it is predicted that the electron beams passing accelerating electric field should with a small probability generate abnormal super-high energy electrons which are much higher than the beam energy. Author’s preliminary experiment result at electron storage ring has hinted these signs, so suggests to more strictly detect this unusual phenomenon, and thus to test the extended mass formula as well as a more perfect special relativity.

  11. Electron Acceleration by High Power Radio Waves in the Ionosphere

    Science.gov (United States)

    Bernhardt, Paul

    2012-10-01

    At the highest ERP of the High Altitude Auroral Research Program (HAARP) facility in Alaska, high frequency (HF) electromagnetic (EM) waves in the ionosphere produce artificial aurora and electron-ion plasma layers. Using HAARP, electrons are accelerated by high power electrostatic (ES) waves to energies >100 times the thermal temperature of the ambient plasma. These ES waves are driven by decay of the pump EM wave tuned to plasma resonances. The most efficient acceleration process occurs near the harmonics of the electron cyclotron frequency in earth's magnetic field. Mode conversion plays a role in transforming the ES waves into EM signals that are recorded with ground receivers. These diagnostic waves, called stimulated EM emissions (SEE), show unique resonant signatures of the strongest electron acceleration. This SEE also provides clues about the ES waves responsible for electron acceleration. The electron gas is accelerated by high frequency modes including Langmuir (electron plasma), upper hybrid, and electron Bernstein waves. All of these waves have been identified in the scattered EM spectra as downshifted sidebands of the EM pump frequency. Parametric decay is responsible low frequency companion modes such as ion acoustic, lower hybrid, and ion Bernstein waves. The temporal evolution of the scattered EM spectrum indicates development of field aligned irregularities that aid the mode conversion process. The onset of certain spectral features is strongly correlated with glow plasma discharge structures that are both visible with the unaided eye and detectable using radio backscatter techniques at HF and UHF frequencies. The primary goals are to understand natural plasma layers, to study basic plasma physics in a unique ``laboratory with walls,'' and to create artificial plasma structures that can aid radio communications.

  12. Electron-cloud effects in high-luminosity colliders

    Energy Technology Data Exchange (ETDEWEB)

    Zimmermann, F.

    1998-01-01

    Electron-cloud instabilities are expected to be important in most high-luminosity double-ring colliders. In this report, the author describes a few parameter regimes and some critical parameter dependences of this type of instability, and illustrate these with simulation results for the PEP-II and KEK B factories, the LHC, the VLHC, and DAPHNE. In addition, the author studies the possibility and the potential impact of an electron cloud in the interaction region.

  13. Electron spectroscopy on high-temperature superconductors and related compounds

    International Nuclear Information System (INIS)

    Knupfer, M.

    1994-01-01

    In the last two classes of materials have been discovered which distinguish themselves due to a transition into the superconducting state at relatively high temperatures. These are the cuprate superconductors and the alkali metal doped fullerenes. In this work the electronic structure of representatives of these materials, undoped and Ca-doped YBa 2 Cu 4 O 8 and A 3 C 60 (A=K, Rb), has been investigated using electron energy-loss spectroscopy and photoemission spectroscopy. (orig.) [de

  14. High resolution electron microscopy and electron diffraction of YBa2Cu3O(7-x)

    International Nuclear Information System (INIS)

    Krakow, W.; Shaw, T.M.

    1988-01-01

    Experimental high resolution electron micrographs and computer simulation experiments have been used to evaluate the visibility of the atomic constituents of YBa 2 Cu 3 O(7-x). In practice, the detection of oxygen has not been possible in contradiction to that predicted by modelling of perfect crystalline material. Preliminary computer experiments of the electron diffraction patterns when oxygen vacancies are introduced on the Cu-O sheets separating Ba layers show the diffuse streaks characteristic of short range ordering. 7 references

  15. High-Throughput Printing Process for Flexible Electronics

    Science.gov (United States)

    Hyun, Woo Jin

    Printed electronics is an emerging field for manufacturing electronic devices with low cost and minimal material waste for a variety of applications including displays, distributed sensing, smart packaging, and energy management. Moreover, its compatibility with roll-to-roll production formats and flexible substrates is desirable for continuous, high-throughput production of flexible electronics. Despite the promise, however, the roll-to-roll production of printed electronics is quite challenging due to web movement hindering accurate ink registration and high-fidelity printing. In this talk, I will present a promising strategy for roll-to-roll production using a novel printing process that we term SCALE (Self-aligned Capillarity-Assisted Lithography for Electronics). By utilizing capillarity of liquid inks on nano/micro-structured substrates, the SCALE process facilitates high-resolution and self-aligned patterning of electrically functional inks with greatly improved printing tolerance. I will show the fabrication of key building blocks (e.g. transistor, resistor, capacitor) for electronic circuits using the SCALE process on plastics.

  16. Can regional climate engineering save the summer Arctic sea ice?

    Science.gov (United States)

    Tilmes, S.; Jahn, Alexandra; Kay, Jennifer E.; Holland, Marika; Lamarque, Jean-Francois

    2014-02-01

    Rapid declines in summer Arctic sea ice extent are projected under high-forcing future climate scenarios. Regional Arctic climate engineering has been suggested as an emergency strategy to save the sea ice. Model simulations of idealized regional dimming experiments compared to a business-as-usual greenhouse gas emission simulation demonstrate the importance of both local and remote feedback mechanisms to the surface energy budget in high latitudes. With increasing artificial reduction in incoming shortwave radiation, the positive surface albedo feedback from Arctic sea ice loss is reduced. However, changes in Arctic clouds and the strongly increasing northward heat transport both counteract the direct dimming effects. A 4 times stronger local reduction in solar radiation compared to a global experiment is required to preserve summer Arctic sea ice area. Even with regional Arctic dimming, a reduction in the strength of the oceanic meridional overturning circulation and a shut down of Labrador Sea deep convection are possible.

  17. Frontend electronics for high-precision single photo-electron timing using FPGA-TDCs

    Energy Technology Data Exchange (ETDEWEB)

    Cardinali, M., E-mail: cardinal@kph.uni-mainz.de [Institut für Kernphysik, Johannes Gutenberg-University Mainz, Mainz (Germany); Helmholtz Institut Mainz, Mainz (Germany); Dzyhgadlo, R.; Gerhardt, A.; Götzen, K.; Hohler, R.; Kalicy, G.; Kumawat, H.; Lehmann, D.; Lewandowski, B.; Patsyuk, M.; Peters, K.; Schepers, G.; Schmitt, L.; Schwarz, C.; Schwiening, J.; Traxler, M.; Ugur, C.; Zühlsdorf, M. [GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt (Germany); Dodokhov, V.Kh. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Britting, A. [Friedrich Alexander-University of Erlangen-Nuremberg, Erlangen (Germany); and others

    2014-12-01

    The next generation of high-luminosity experiments requires excellent particle identification detectors which calls for Imaging Cherenkov counters with fast electronics to cope with the expected hit rates. A Barrel DIRC will be used in the central region of the Target Spectrometer of the planned PANDA experiment at FAIR. A single photo-electron timing resolution of better than 100 ps is required by the Barrel DIRC to disentangle the complicated patterns created on the image plane. R and D studies have been performed to provide a design based on the TRB3 readout using FPGA-TDCs with a precision better than 20 ps RMS and custom frontend electronics with high-bandwidth pre-amplifiers and fast discriminators. The discriminators also provide time-over-threshold information thus enabling walk corrections to improve the timing resolution. Two types of frontend electronics cards optimised for reading out 64-channel PHOTONIS Planacon MCP-PMTs were tested: one based on the NINO ASIC and the other, called PADIWA, on FPGA discriminators. Promising results were obtained in a full characterisation using a fast laser setup and in a test experiment at MAMI, Mainz, with a small scale DIRC prototype. - Highlights: • Frontend electronics for Cherenkov detectors have been developed. • FPGA-TDCs have been used for high precision timing. • Time over threshold has been utilised for walk correction. • Single photo-electron timing resolution less than 100 ps has been achieved.

  18. The Arctic - A New Region for China's Foreign Policy

    Directory of Open Access Journals (Sweden)

    V S Yagiya

    2015-12-01

    Full Text Available Article is devoted to foreign policy of China in the Arctic. Main attention is paid to strategic view of the China concerning the Arctic, to bilateral and multilateral cooperation on the Arctic issues, also to opinion of Russian experts about discussing of Russian-China economic partnership. It was shown interests of the People's Republic of China in the Arctic: use Arctic transport system from the Pacific Rim to Europe; possibility of access to the Arctic resources; seeks of partners for the realized of Arctic projects and programs. It was pointed six directions of China cooperation in the Arctic: a scientific researches, b natural minerals, oil and gas issues, c tourism, d routes of the Arctic navigation, e use of high technologies in development of regional economy, e cooperation in the cultural and educational spheres. Authors are summarized that at the initial stage of the international cooperation in the Arctic polar scientific researches become as the tool of “he soft power”, and in the long term - the Northern Sea Route of the Russian Federation is included in the Strategy of China Economic belt and the Maritime Silk Route in the XXI century.

  19. Radioactive contamination in Arctic - present situation and future challenges

    International Nuclear Information System (INIS)

    Strand, Per

    2002-01-01

    There is currently a focus on radioactivity and the Arctic region. The reason for this is probably the high number of nuclear sources in parts of the Arctic and the vulnerability of Arctic systems to radioactive contamination. The Arctic environment is also perceived as a wilderness and the need for the protection of this wilderness against contamination is great. In the last decade information has also been released concerning the nuclear situation which has caused concern in many countries. Due to such concerns, the International Arctic Environmental Protection Strategy (IAEPS) was launched in 1991 and the Arctic Monitoring and Assessment Programme (AMAP) was established. AMAP is undertaking an assessment of the radioactive contamination of the Arctic and its radiological consequences. In 1996 IAEPS became part of the Arctic Council. AMAP presented one main report in 1997 and another in 1998. There are also several other national, bilateral and international programmes in existence which deal with this issue. This paper summarises some of current knowledge about sources of radioactive contamination, vulnerability, exposure of man, and potential sources for radioactive contamination within Arctic and some views on the future needs for work concerning radioactivity in Arctic. (au)

  20. The fate of 13C15N labelled glycine in permafrost and surface soil at simulated thaw in mesocosms from high arctic and subarctic ecosystems

    DEFF Research Database (Denmark)

    Ravn, Nynne Marie Rand; Elberling, Bo; Michelsen, Anders

    2017-01-01

    Background and aim: Nutrient distribution and carbon fluxes upon spring thaw are compared in mesocosms from high arctic and subarctic ecosystems dominated by Cassiope tetragona or Salix hastata/Salix arctica, in order to evaluate the possibility of plant and microbial utilization of an organic...... compound in thawing permafrost and surface soil. Methods: Double labeled glycine (13C15N) was added to soil columns with vegetation and to permafrost. During thaw conditions ecosystem respiration 13C was measured and 13C and 15N distribution in the ecosystem pools was quantified one day and one month after...... glycine addition. Results: Near-surface soil microbes were more efficient in the uptake of intact glycine immediately upon thaw than plants. After one month plants had gained more 15N whereas microbes seemed to lose 15N originating from glycine. We observed a time lag in glycine degradation upon...

  1. Towards improved estimation of the dynamic topography and ocean circulation in the high latitude and arctic ocean: The importance of GOCE

    DEFF Research Database (Denmark)

    Johannessen, J. A.; Raj, R. P.; Nilsen, J. E. Ø.

    2013-01-01

    The Arctic plays a fundamental role in the climate system and shows significant sensitivity to anthropogenic climate forcing and the ongoing climate change. Evidently changes in the Arctic and surrounding seas have far reaching influences on regional and global environment and climate variability...

  2. Terrestrial biosphere models underestimate photosynthetic capacity and CO2 assimilation in the Arctic.

    Science.gov (United States)

    Rogers, Alistair; Serbin, Shawn P; Ely, Kim S; Sloan, Victoria L; Wullschleger, Stan D

    2017-12-01

    Terrestrial biosphere models (TBMs) are highly sensitive to model representation of photosynthesis, in particular the parameters maximum carboxylation rate and maximum electron transport rate at 25°C (V c,max.25 and J max.25 , respectively). Many TBMs do not include representation of Arctic plants, and those that do rely on understanding and parameterization from temperate species. We measured photosynthetic CO 2 response curves and leaf nitrogen (N) content in species representing the dominant vascular plant functional types found on the coastal tundra near Barrow, Alaska. The activation energies associated with the temperature response functions of V c,max and J max were 17% lower than commonly used values. When scaled to 25°C, V c,max.25 and J max.25 were two- to five-fold higher than the values used to parameterize current TBMs. This high photosynthetic capacity was attributable to a high leaf N content and the high fraction of N invested in Rubisco. Leaf-level modeling demonstrated that current parameterization of TBMs resulted in a two-fold underestimation of the capacity for leaf-level CO 2 assimilation in Arctic vegetation. This study highlights the poor representation of Arctic photosynthesis in TBMs, and provides the critical data necessary to improve our ability to project the response of the Arctic to global environmental change. No claim to original US Government works. New Phytologist © 2017 New Phytologist Trust.

  3. Investigation of UHPLC/travelling-wave ion mobility/time-of-flight mass spectrometry for fast profiling of fatty acids in the high Arctic sea surface microlayer.

    Science.gov (United States)

    Rad, Farshid Mashayekhy; Leck, Caroline; Ilag, Leopold L; Nilsson, Ulrika

    2018-03-09

    Fatty acids are enriched in the ocean surface microlayer (SML) and have as a consequence been detected worldwide in sea spray aerosols. In searching for a relationship between the properties of the atmospheric aerosol and its ability to form cloud condensation nuclei and to promote cloud droplet formation over remote marine areas, the role of surface active fatty acids sourced from the SML is of interest to be investigated. Here is presented a fast method for profiling of major fatty acids in SML samples collected in the high Arctic (89 °N, 1 °W) in the summer of 2001. UHPLC/travelling-wave ion mobility spectrometry (TWIMS)/time-of-flight (TOF) mass spectrometry (MS) for profiling was evaluated and compared with UHPLC/TOFMS. No sample preparation, except evaporation and centrifugation, was necessary to perform prior to the analysis. TOFMS data on accurate mass, isotopic ratios and fragmentation patterns enabled identification of the fatty acids. The TWIMS dimension added to the selectivity by extensive reduction of the noise level and the entire UHPLC/TWIMS/TOFMS method provided a fast profiling of the acids, ranging from C 8 to C 24 . Hexadecanoic and octadecanoic acids were shown to yield the highest signals among the fatty acids detected in a high Arctic SML sample, followed by the unsaturated octadecenoic and octadecadienoic acids. The predominance of signal from even-numbered carbon chains indicates a mainly biogenic origin of the detected fatty acids. This study presents a fast alternative method for screening and profiling of fatty acids, which has the advantage of not requiring any complicated sample preparation thus limiting the loss of analytes. Almost no manual handling, together with the very small sample volumes needed, is certainly beneficial for the determination of trace amounts and should open up the field of applications to also include atmospheric aerosol and fog. This article is protected by copyright. All rights reserved.

  4. Long-term structural canopy changes sustain net photosynthesis per ground area in high arctic Vaccinium uliginosum exposed to changes in near-ambient UV-B levels.

    Science.gov (United States)

    Boesgaard, Kristine S; Albert, Kristian R; Ro-Poulsen, Helge; Michelsen, Anders; Mikkelsen, Teis N; Schmidt, Niels M

    2012-08-01

    Full recovery of the ozone layer is not expected for several decades and consequently, the incoming level of solar ultraviolet-B (UV-B) will only slowly be reduced. Therefore to investigate the structural and photosynthetic responses to changes in solar UV-B we conducted a 5-year UV-B exclusion study in high arctic Greenland. During the growing season, the gas exchange (H₂O and CO₂) and chlorophyll-a fluorescence were measured in Vaccinium uliginosum. The leaf dry weight, carbon, nitrogen, stable carbon isotope ratio, chlorophyll and carotenoid content were determined from a late season harvest. The net photosynthesis per leaf area was on average 22% higher in 61% reduced UV-B treatment across the season, but per ground area photosynthesis was unchanged. The leaf level increase in photosynthesis was accompanied by increased leaf nitrogen, higher stomatal conductance and F(v)/F(m). There was no change in total leaf biomass, but reduction in total leaf area caused a pronounced reduction of specific leaf area and leaf area index in reduced UV-B. This demonstrates the structural changes to counterbalance the reduced plant carbon uptake seen per leaf area in ambient UV-B as the resulting plant carbon uptake per ground area was not affected. Thus, our understanding of long-term responses to UV-B reduction must take into account both leaf level processes as well as structural changes to understand the apparent robustness of plant carbon uptake per ground area. In this perspective, V. uliginosum seems able to adjust plant carbon uptake to the present amount of solar UV-B radiation in the High Arctic. Copyright © Physiologia Plantarum 2011.

  5. A trajectory analysis of atmospheric transport of black carbon aerosols to Canadian high Arctic in winter and spring (1990–2005

    Directory of Open Access Journals (Sweden)

    L. Huang

    2010-06-01

    Full Text Available Black carbon (BC particles accumulated in the Arctic troposphere and deposited on snow have been calculated to have significant effects on radiative forcing of the Arctic regional climate. Applying cluster analysis technique on 10-day backward trajectories, seven distinct transport pathways (or clusters affecting Alert (82.5° N, 62.5° W, Nunavut in Canada are identified in this work. Transport frequency associated with each pathway is obtained as the fraction of trajectories in that cluster. Based on atmospheric transport frequency and BC surface flux from surrounding regions (i.e. North America, Europe, and former USSR, a linear regression model is constructed to investigate the inter-annual variations of BC observed at Alert in January and April, representative of winter and spring respectively, between 1990 and 2005. Strong correlations are found between BC concentrations predicted with the regression model and measurements at Alert for both seasons (R2 equals 0.77 and 0.81 for winter and spring, respectively. Results imply that atmospheric transport and BC emission are the major contributors to the inter-annual variations in BC concentrations observed at Alert in the cold seasons for the 16-year period. Other factors, such as deposition, could also contribute to the variability in BC concentrations but were not considered in this analysis. Based on the regression model the relative contributions of regional BC emissions affecting Alert are attributed to the Eurasian sector, composed of the European Union and the former USSR, and the North American sector. Considering both seasons, the model suggests that former USSR is the major contributor to the near-surface BC levels at the Canadian high Arctic site with an average contribution of about 67% during the 16-year period, followed by European Union (18% and North America (15%. In winter, the atmospheric transport of BC aerosols from Eurasia is found to be even more

  6. A 20-year record (1998-2017) of permafrost, active layer and meteorological conditions at a high Arctic permafrost research site (Bayelva, Spitsbergen)

    Science.gov (United States)

    Boike, Julia; Juszak, Inge; Lange, Stephan; Chadburn, Sarah; Burke, Eleanor; Overduin, Pier Paul; Roth, Kurt; Ippisch, Olaf; Bornemann, Niko; Stern, Lielle; Gouttevin, Isabelle; Hauber, Ernst; Westermann, Sebastian

    2018-03-01

    Most permafrost is located in the Arctic, where frozen organic carbon makes it an important component of the global climate system. Despite the fact that the Arctic climate changes more rapidly than the rest of the globe, observational data density in the region is low. Permafrost thaw and carbon release to the atmosphere are a positive feedback mechanism that can exacerbate global warming. This positive feedback functions via changing land-atmosphere energy and mass exchanges. There is thus a great need to understand links between the energy balance, which can vary rapidly over hourly to annual timescales, and permafrost, which changes slowly over long time periods. This understanding thus mandates long-term observational data sets. Such a data set is available from the Bayelva site at Ny-Ålesund, Svalbard, where meteorology, energy balance components and subsurface observations have been made for the last 20 years. Additional data include a high-resolution digital elevation model (DEM) that can be used together with the snow physical information for snowpack modeling and a panchromatic image. This paper presents the data set produced so far, explains instrumentation, calibration, processing and data quality control, as well as the sources for various resulting data sets. The resulting data set is unique in the Arctic and serves as a baseline for future studies. The mean permafrost temperature is -2.8 °C, with a zero-amplitude depth at 5.5 m (2009-2017). Since the data provide observations of temporally variable parameters that mitigate energy fluxes between permafrost and atmosphere, such as snow depth and soil moisture content, they are suitable for use in integrating, calibrating and testing permafrost as a component in earth system models.The presented data are available in the Supplement for this paper (time series) and through the PANGAEA and Zenodo data portals: time series (https://doi.org/10.1594/PANGAEA.880120, https://zenodo.org/record/1139714) and

  7. A 20-year record (1998–2017 of permafrost, active layer and meteorological conditions at a high Arctic permafrost research site (Bayelva, Spitsbergen

    Directory of Open Access Journals (Sweden)

    J. Boike

    2018-03-01

    Full Text Available Most permafrost is located in the Arctic, where frozen organic carbon makes it an important component of the global climate system. Despite the fact that the Arctic climate changes more rapidly than the rest of the globe, observational data density in the region is low. Permafrost thaw and carbon release to the atmosphere are a positive feedback mechanism that can exacerbate global warming. This positive feedback functions via changing land–atmosphere energy and mass exchanges. There is thus a great need to understand links between the energy balance, which can vary rapidly over hourly to annual timescales, and permafrost, which changes slowly over long time periods. This understanding thus mandates long-term observational data sets. Such a data set is available from the Bayelva site at Ny-Ålesund, Svalbard, where meteorology, energy balance components and subsurface observations have been made for the last 20 years. Additional data include a high-resolution digital elevation model (DEM that can be used together with the snow physical information for snowpack modeling and a panchromatic image. This paper presents the data set produced so far, explains instrumentation, calibration, processing and data quality control, as well as the sources for various resulting data sets. The resulting data set is unique in the Arctic and serves as a baseline for future studies. The mean permafrost temperature is −2.8 °C, with a zero-amplitude depth at 5.5 m (2009–2017. Since the data provide observations of temporally variable parameters that mitigate energy fluxes between permafrost and atmosphere, such as snow depth and soil moisture content, they are suitable for use in integrating, calibrating and testing permafrost as a component in earth system models.The presented data are available in the Supplement for this paper (time series and through the PANGAEA and Zenodo data portals: time series (https://doi.org/10.1594/PANGAEA.880120, https

  8. Arctic Climate and Atmospheric Planetary Waves

    Science.gov (United States)

    Cavalieri, D. J.; Haekkinen, S.; Zukor, Dorothy J. (Technical Monitor)

    2001-01-01

    Analysis of a fifty-year record (1946-1995) of monthly-averaged sea level pressure data provides a link between the phases of planetary-scale sea level pressure waves and Arctic Ocean and ice variability. Results of this analysis show: (1) a breakdown of the dominant wave 1 pattern in the late 1960's, (2) shifts in the mean phase of waves 1 and 2 since this breakdown, (3) an eastward shift in the phases of both waves 1 and 2 during the years of simulated cyclonic Arctic Ocean circulation relative to their phases during the years of anticyclonic circulation, (4) a strong decadal variability of wave phase associated with simulated Arctic Ocean circulation changes. Finally, the Arctic atmospheric circulation patterns that emerge when waves 1 and 2 are in their extreme eastern and western positions suggest an alternative approach for determining significant forcing patterns of sea ice and high-latitude variability.

  9. Sulfate Aerosol in the Arctic: Source Attribution and Radiative Forcing

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yang [Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland WA USA; Wang, Hailong [Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland WA USA; Smith, Steven J. [Joint Global Change Research Institute, Pacific Northwest National Laboratory, College Park MD USA; Easter, Richard C. [Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland WA USA; Rasch, Philip J. [Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland WA USA

    2018-02-08

    Source attributions of Arctic sulfate and its direct radiative effect for 2010–2014 are quantified in this study using the Community Earth System Model (CESM) equipped with an explicit sulfur source-tagging technique. Regions that have high emissions and/or are near/within the Arctic present relatively large contributions to Arctic sulfate burden, with the largest contribution from sources in East Asia (27%). East Asia and South Asia together have the largest contributions to Arctic sulfate concentrations at 9–12 km, whereas sources within or near the Arctic account largely below 2 km. For remote sources with strong emissions, their contributions to Arctic sulfate burden are primarily driven by meteorology, while contributions of sources within or near the Arctic are dominated by their emission strength. The sulfate direct radiative effect (DRE) is –0.080 W m-2 at the Arctic surface, offsetting the net warming effect from the combination of in-snow heating and DRE cooling from black carbon. East Asia, Arctic local and Russia/Belarus/Ukraine sources contribute –0.017, –0.016 and –0.014 W m-2, respectively, to Arctic sulfate DRE. A 20% reduction in anthropogenic SO2 emissions leads to a net increase of +0.013 W m-2 forcing at the Arctic surface. These results indicate that a joint reduction in BC emissions could prevent possible Arctic warming from future reductions in SO2 emissions. Sulfate DRE efficiency calculations suggest that short transport pathways together with meteorology favoring long sulfate lifetimes make certain sources more efficient in influencing the Arctic sulfate DRE.

  10. Electronics and triggering challenges for the CMS High Granularity Calorimeter

    Science.gov (United States)

    Lobanov, A.

    2018-02-01

    The High Granularity Calorimeter (HGCAL), presently being designed by the CMS collaboration to replace the CMS endcap calorimeters for the High Luminosity phase of LHC, will feature six million channels distributed over 52 longitudinal layers. The requirements for the front-end electronics are extremely challenging, including high dynamic range (0.2 fC-10 pC), low noise (~2000 e- to be able to calibrate on single minimum ionising particles throughout the detector lifetime) and low power consumption (~20 mW/channel), as well as the need to select and transmit trigger information with a high granularity. Exploiting the intrinsic precision-timing capabilities of silicon sensors also requires careful design of the front-end electronics as well as the whole system, particularly clock distribution. The harsh radiation environment and requirement to keep the whole detector as dense as possible will require novel solutions to the on-detector electronics layout. Processing the data from the HGCAL imposes equally large challenges on the off-detector electronics, both for the hardware and incorporated algorithms. We present an overview of the complete electronics architecture, as well as the performance of prototype components and algorithms.

  11. A high power, tunable free electron maser for fusion

    Energy Technology Data Exchange (ETDEWEB)

    Urbanus, W.H.; Bratman, V.L.; Bongers, W.A.; Caplan, M.; Denisov, G.G.; Geer, C.A.J. van der; Manintveld, P.; Militsyn, B.; Oomens, A.A.M.; Poelman, A.J.; Plomp, J.; Pluygers, J.; Savilov, A.V.; Smeets, P.H.M.; Sterk, A.B.; Verhoeven, A.G.A

    2001-01-01

    The Fusion-FEM experiment, a high-power, electrostatic free-electron maser being built at the FOM-Institute for Plasma Physics 'Rijnhuizen', is operated at various frequencies. So far, experiments were done without a depressed collector, and the pulse length was limited to 12 {mu}s. Nevertheless, many aspects of generation of mm-wave power have been explored, such as the dependency on the electron beam energy and beam current, and cavity settings such as the feedback coefficient. An output power of 730 kW at 206 GHz is generated with a 7.2 A, 1.77 MeV electron beam, and 360 kW at 167 GHz is generated with a 7.4 A, 1.61 MeV electron beam. It is shown experimentally and by simulations that, depending on the electron beam energy, the FEM can operate in single-frequency regime. The next step of the FEM experiment is to reach a pulse length of 100 ms. The major part of the beam line, the high voltage systems, and the collector have been completed. The undulator and mm-wave cavity are now at high voltage (2 MV). The new mm-wave transmission line, which transports the mm-wave output power from the high-voltage terminal to ground and outside the pressure tank, has been tested at low power.

  12. High electron beam dosimetry using ZrO2

    International Nuclear Information System (INIS)

    Lueza M, F.; Rivera M, T.; Azorin N, J.; Garcia H, M.

    2009-10-01

    This paper reports the experimental results of studying the thermoluminescent (Tl) properties of ZrO 2 powder embedded in polytetrafluorethylene (PTFE) exposed to high energy electron beam from linear accelerators (Linac). Structural and morphological characteristics were also reported. Irradiations were conducted using high energy electrons beams in the range from 2 to 18 MeV. Pellets of ZrO 2 +PTFE were produced using polycrystalline powder grown by the precipitation method. These pellets presented a Tl glow curve exhibiting an intense glow peak centered at around 235 C. Tl response as a function of high electron absorbed dose was linear in the range from 2 to 30 Gy. Repeatability determined by exposing a set of pellets repeatedly to the same electron absorbed dose was 0.5%. Fading along 30 days was about 50%. Then, results obtained in this study suggest than ZrO 2 +PTFE pellets could be used for high energy electron beam dosimetry provided fading correction is accounted for. (Author)

  13. Evaporation of carbon using electrons of a high density plasma

    International Nuclear Information System (INIS)

    Muhl, S.; Camps, E.; Escobar A, L.; Garcia E, J.L.; Olea, O.

    1999-01-01

    The high density plasmas are used frequently in the preparation of thin films or surface modification, for example to nitridation. In these processes, are used mainly the ions and the neutrals which compose the plasma. However, the electrons present in the plasma are not used, except in the case of chemical reactions induced by collisions, although the electron bombardment usually get hot the work piece. Through the adequate polarization of a conductor material, it is possible to extract electrons from a high density plasma at low pressure, that could be gotten the evaporation of this material. As result of the interaction between the plasma and the electron flux with the vapor produced, this last will be ionized. In this work, it is reported the use of this novelty arrangement to prepare carbon thin films using a high density argon plasma and a high purity graphite bar as material to evaporate. It has been used substrates outside plasma and immersed in the plasma. Also it has been reported the plasma characteristics (temperature and electron density, energy and ions flux), parameters of the deposit process (deposit rate and ion/neutral rate) as well as the properties of the films obtained (IR absorption spectra and UV/Vis, elemental analysis, hardness and refractive index. (Author)

  14. High current precision long pulse electron beam position monitor

    CERN Document Server

    Nelson, S D; Fessenden, T J; Holmes, C

    2000-01-01

    Precision high current long pulse electron beam position monitoring has typically experienced problems with high Q sensors, sensors damped to the point of lack of precision, or sensors that interact substantially with any beam halo thus obscuring the desired signal. As part of the effort to develop a multi-axis electron beam transport system using transverse electromagnetic stripline kicker technology, it is necessary to precisely determine the position and extent of long high energy beams for accurate beam position control (6 - 40 MeV, 1 - 4 kA, 2 μs beam pulse, sub millimeter beam position accuracy.) The kicker positioning system utilizes shot-to-shot adjustments for reduction of relatively slow (< 20 MHz) motion of the beam centroid. The electron beams passing through the diagnostic systems have the potential for large halo effects that tend to corrupt position measurements.

  15. Multinational Experiment 7. Maritime Security Region: The Arctic

    Science.gov (United States)

    2013-07-08

    increasingly affect human communities , natural systems, and infrastructure. Resources and Trade Routes in the Arctic Climate change in the Far...capelin, herring, navaga, and wolffishes. Some areas of the Arctic and sub-Arctic suffer from high levels of illegal fishing and overfishing , and...maneuvering, joint air defense drills, communications and search and rescue operations. The exercise is normally held every second year. 8 In

  16. White Arctic vs. Blue Arctic: Making Choices

    Science.gov (United States)

    Pfirman, S. L.; Newton, R.; Schlosser, P.; Pomerance, R.; Tremblay, B.; Murray, M. S.; Gerrard, M.

    2015-12-01

    As the Arctic warms and shifts from icy white to watery blue and resource-rich, tension is arising between the desire to restore and sustain an ice-covered Arctic and stakeholder communities that hope to benefit from an open Arctic Ocean. If emissions of greenhouse gases to the atmosphere continue on their present trend, most of the summer sea ice cover is projected to be gone by mid-century, i.e., by the time that few if any interventions could be in place to restore it. There are many local as well as global reasons for ice restoration, including for example, preserving the Arctic's reflectivity, sustaining critical habitat, and maintaining cultural traditions. However, due to challenges in implementing interventions, it may take decades before summer sea ice would begin to return. This means that future generations would be faced with bringing sea ice back into regions where they have not experienced it before. While there is likely to be interest in taking action to restore ice for the local, regional, and global services it provides, there is also interest in the economic advancement that open access brings. Dealing with these emerging issues and new combinations of stakeholders needs new approaches - yet environmental change in the Arctic is proceeding quickly and will force the issues sooner rather than later. In this contribution we examine challenges, opportunities, and responsibilities related to exploring options for restoring Arctic sea ice and potential pathways for their implementation. Negotiating responses involves international strategic considerations including security and governance, meaning that along with local communities, state decision-makers, and commercial interests, national governments will have to play central roles. While these issues are currently playing out in the Arctic, similar tensions are also emerging in other regions.

  17. Preliminary investigations on high energy electron beam tomography

    Energy Technology Data Exchange (ETDEWEB)

    Baertling, Yves; Hoppe, Dietrich; Hampel, Uwe

    2010-12-15

    In computed tomography (CT) cross-sectional images of the attenuation distribution within a slice are created by scanning radiographic projections of an object with a rotating X-ray source detector compound and subsequent reconstruction of the images from these projection data on a computer. CT can be made very fast by employing a scanned electron beam instead of a mechanically moving X-ray source. Now this principle was extended towards high-energy electron beam tomography with an electrostatic accelerator. Therefore a dedicated experimental campaign was planned and carried out at the Budker Institute of Nuclear Physics (BINP), Novosibirsk. There we investigated the capabilities of BINP's accelerators as an electron beam generating and scanning unit of a potential high-energy electron beam tomography device. The setup based on a 1 MeV ELV-6 (BINP) electron accelerator and a single detector. Besides tomographic measurements with different phantoms, further experiments were carried out concerning the focal spot size and repeat accuracy of the electron beam as well as the detector's response time and signal to noise ratio. (orig.)

  18. High-resolution electron microscopy of advanced materials

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, T.E.; Kung, H.H.; Sickafus, K.E.; Gray, G.T. III; Field, R.D.; Smith, J.F. [Los Alamos National Lab., NM (United States). Materials Science and Technology Div.

    1997-11-01

    This final report chronicles a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The High-Resolution Electron Microscopy Facility has doubled in size and tripled in quality since the beginning of the three-year period. The facility now includes a field-emission scanning electron microscope, a 100 kV field-emission scanning transmission electron microscope (FE-STEM), a 300 kV field-emission high-resolution transmission electron microscope (FE-HRTEM), and a 300 kV analytical transmission electron microscope. A new orientation imaging microscope is being installed. X-ray energy dispersive spectrometers for chemical analysis are available on all four microscopes; parallel electron energy loss spectrometers are operational on the FE-STEM and FE-HRTEM. These systems enable evaluation of local atomic bonding, as well as chemical composition in nanometer-scale regions. The FE-HRTEM has a point-to-point resolution of 1.6 {angstrom}, but the resolution can be pushed to its information limit of 1 {angstrom} by computer reconstruction of a focal series of images. HRTEM has been used to image the atomic structure of defects such as dislocations, grain boundaries, and interfaces in a variety of materials from superconductors and ferroelectrics to structural ceramics and intermetallics.

  19. Electron curing for high speed paper, film and foil converting

    International Nuclear Information System (INIS)

    Nablo, S.V.; Tripp, E.P.

    1979-01-01

    The status of self-shielded, compact electron processors for flexible web converting applications is reviewed. The uses of these units for a variety of laminating applications are described, with emphasis on the application techniques appropriate for low weight, (1 to 2 gm/m 2 ) 100% convertible adhesives. Performance data for electron cured adhesives with polyester/polyethylene systems is presented and compared with conventional urethane systems. The unique surface features of electron cured gravure coatings applied and cured at high speed are discussed, with reference to both paper and film substrates. An important advantage of electron curing of buried adhesive layers is the process quality control permitted by this 'all-electric' system. The performance characteristics of curing atmosphere control (inerting) for coatings are reviewed. Industrial experience with these processors has shown that effective inerting of coated flexible webs at speeds to 250 m/minute is both practical and economical. (author)

  20. Disinfection of wastewaters: high-energy electron vs gamma irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Farooq, S [King Fahd Univ. of Petroleum and Minerals, Dhahran (Saudi Arabia). Dept. of Civil Engineering; Kurucz, C N; Waite, T D [Miami Univ., Coral Gables, FL (United States); Cooper, W J [Florida International Univ., Miami, FL (United States). Drinking Water Research Center

    1993-07-01

    A study was undertaken to examine the sensitivity of a wastewater population of coliphage, total coliforms and total flora present in raw sewage and secondary effluent after irradiating with similar doses delivered by a high-energy electron beam and [gamma]-radiation. The electron beam study was conducted on a large scale at the Virginia Key Wastewater Treatment Plant, Miami, Florida. The facility is equipped with a 1.5 MeV, 50 mA electron accelerator, with a wastewater flow rate of 8ls[sup -1]. Concurrent [gamma]-radiation studies were conducted at laboratory scale using a 5000 Ci, [sup 60]Co [gamma]-source. Three logs reduction of all three test organisms were observed at an electron beam dose of 500 krads, while at least four logs reduction were observed at the same dose utilizing the [gamma]'source. (Author).

  1. High power microwave emission and diagnostics of microsecond electron beams

    Energy Technology Data Exchange (ETDEWEB)

    Gilgenbach, R; Hochman, J M; Jayness, R; Rintamaki, J I; Lau, Y Y; Luginsland, J; Lash, J S [Univ. of Michigan, Ann Arbor, MI (United States). Intense Electron Beam Interaction Lab.; Spencer, T A [Air Force Phillips Lab., Kirtland AFB, NM (United States)

    1997-12-31

    Experiments were performed to generate high power, long-pulse microwaves by the gyrotron mechanism in rectangular cross-section interaction cavities. Long-pulse electron beams are generated by MELBA (Michigan Electron Long Beam Accelerator), which operates with parameters: -0.8 MV, 1-10 kA, and 0.5-1 microsecond pulse length. Microwave power levels are in the megawatt range. Polarization control is being studied by adjustment of the solenoidal magnetic field. Initial results show polarization power ratios up to a factor of 15. Electron beam dynamics (V{sub perp}/V{sub par}) are being measured by radiation darkening on glass plates. Computer modeling utilizes the MAGIC Code for electromagnetic waves and a single electron orbit code that includes a distribution of angles. (author). 4 figs., 4 refs.

  2. Innovative electron-beam welding of high-melting metals

    International Nuclear Information System (INIS)

    Behr, W.; Reisgen, U.

    2007-01-01

    Since its establishment as nuclear research plant Juelich in the year 1956, the research centre Juelich (FZJ) is concerned with the material processing of special metals. Among those are, above all, the high-melting refractory metals niobium, molybdenum and tungsten. Electron beam welding has always been considered to be an innovative special welding method; in the FZJ, electron beam welding has, moreover, always been adapted to the increasing demands made by research partners and involved manufacturing and design sectors. From the manual equipment technology right up to highly modern multi-beam technique, the technically feasible for fundamental research has, this way, always been realised. (Abstract Copyright [2007], Wiley Periodicals, Inc.) [de

  3. The LLNL/UCLA high gradient inverse free electron laser

    Energy Technology Data Exchange (ETDEWEB)

    Moody, J. T.; Musumeci, P.; Anderson, G.; Anderson, S.; Betts, S.; Fisher, S.; Gibson, D.; Tremaine, A.; Wu, S. [Department of Physics and Astronomy, UCLA, Los Angeles California, 90095 (United States); Lawrence Livermore National Laboratory (United States)

    2012-12-21

    We describe the Inverse Free Electron Accelerator currently under construction at Lawrence Livermore National Lab. Upon completion of this accelerator, high brightness electrons generated in the photoinjector blowout regime and accelerated to 50 MeV by S-band accelerating sections will interact with > 4 TW peak power Ti:Sapphire laser in a highly tapered 50 cm undulator and experience an acceleration gradient of > 200 MeV/m. We present the final design of the accelerator as well as the results of start-to-end simulations investigating preservation of beam quality and tolerances involved with this accelerator.

  4. Simulation of electron displacement damage in a high voltage electron microscope

    International Nuclear Information System (INIS)

    Ono, Susumu; Kanaya, Koichi

    1979-01-01

    By applying the fundamental theory of the neutron cooling to the conservation law of energy and momentum, the threshold energies of incident electrons for displacing atoms are calculated and illustrated periodically for the atomic number. And the observable damage due to the secondary action of displaced atoms in the practical use of a high voltage electron microscope is described for several materials and accelerating voltages. The trajectories of incident electrons and displaced atoms in several materials are simulated by a Monte-Carlo method, using rigorous formulas of electron scattering events, i.e. elastic and inelastic scattering cross-sections, ionization loss and plasmon excitation. The simulation results are substantially agreement with experiments. (author)

  5. Brent goose colonies near snowy owls: Internest distances in relation to breeding arctic fox densities

    NARCIS (Netherlands)

    Kharitonov, S.P.; Ebbinge, B.S.; De Fouw, J.

    2013-01-01

    It was shown that in the years when the numbers of the Arctic foxes are high, even though the lemming numbers are high as well, Brent geese nest considerably closer to owls' nests than in the years with low Arctic fox numbers. At values of the Arctic fox densities greater than one breeding pair per

  6. High luminosity electron-hadron collider eRHIC

    Energy Technology Data Exchange (ETDEWEB)

    Ptitsyn, V.; Aschenauer, E.; Bai, M.; Beebe-Wang, J.; Belomestnykh, S.; Ben-Zvi, I.; Blaskiewicz, M..; Calaga, R.; Chang, X.; Fedotov, A.; Gassner, D.; Hammons, L.; Hahn, H.; Hammons, L.; He, P.; Hao, Y.; Jackson, W.; Jain, A.; Johnson, E.C.; Kayran, D.; Kewisch, J.; Litvinenko, V.N.; Luo, Y.; Mahler, G.; McIntyre, G.; Meng, W.; Minty, M.; Parker, B.; Pikin, A.; Rao, T.; Roser, T.; Skaritka, J.; Sheehy, B.; Skaritka, J.; Tepikian, S.; Than, Y.; Trbojevic, D.; Tsoupas, N.; Tuozzolo, J.; Wang, G.; Webb, S.; Wu, Q.; Xu, W.; Pozdeyev, E.; Tsentalovich, E.

    2011-03-28

    We present the design of a future high-energy high-luminosity electron-hadron collider at RHIC called eRHIC. We plan on adding 20 (potentially 30) GeV energy recovery linacs to accelerate and to collide polarized and unpolarized electrons with hadrons in RHIC. The center-of-mass energy of eRHIC will range from 30 to 200 GeV. The luminosity exceeding 10{sup 34} cm{sup -2} s{sup -1} can be achieved in eRHIC using the low-beta interaction region with a 10 mrad crab crossing. We report on the progress of important eRHIC R&D such as the high-current polarized electron source, the coherent electron cooling, ERL test facility and the compact magnets for recirculation passes. A natural staging scenario of step-by-step increases of the electron beam energy by building-up of eRHIC's SRF linacs is presented.

  7. A practical algorithm for the retrieval of floe size distribution of Arctic sea ice from high-resolution satellite Synthetic Aperture Radar imagery

    Directory of Open Access Journals (Sweden)

    Byongjun Hwang

    2017-07-01

    Full Text Available In this study, we present an algorithm for summer sea ice conditions that semi-automatically produces the floe size distribution of Arctic sea ice from high-resolution satellite Synthetic Aperture Radar data. Currently, floe size distribution data from satellite images are very rare in the literature, mainly due to the lack of a reliable algorithm to produce such data. Here, we developed the algorithm by combining various image analysis methods, including Kernel Graph Cuts, distance transformation and watershed transformation, and a rule-based boundary revalidation. The developed algorithm has been validated against the ground truth that was extracted manually with the aid of 1-m resolution visible satellite data. Comprehensive validation analysis has shown both perspectives and limitations. The algorithm tends to fail to detect small floes (mostly less than 100 m in mean caliper diameter compared to ground truth, which is mainly due to limitations in water-ice segmentation. Some variability in the power law exponent of floe size distribution is observed due to the effects of control parameters in the process of de-noising, Kernel Graph Cuts segmentation, thresholds for boundary revalidation and image resolution. Nonetheless, the algorithm, for floes larger than 100 m, has shown a reasonable agreement with ground truth under various selections of these control parameters. Considering that the coverage and spatial resolution of satellite Synthetic Aperture Radar data have increased significantly in recent years, the developed algorithm opens a new possibility to produce large volumes of floe size distribution data, which is essential for improving our understanding and prediction of the Arctic sea ice cover

  8. Distribution of PAHs and the PAH-degrading bacteria in the deep-sea sediments of the high-latitude Arctic Ocean

    Science.gov (United States)

    Dong, C.; Bai, X.; Sheng, H.; Jiao, L.; Zhou, H.; Shao, Z.

    2015-04-01

    Polycyclic aromatic hydrocarbons (PAHs) are common organic pollutants that can be transferred long distances and tend to accumulate in marine sediments. However, less is known regarding the distribution of PAHs and their natural bioattenuation in the open sea, especially the Arctic Ocean. In this report, sediment samples were collected at four sites from the Chukchi Plateau to the Makarov Basin in the summer of 2010. PAH compositions and total concentrations were examined with GC-MS. The concentrations of 16 EPA-priority PAHs varied from 2.0 to 41.6 ng g-1 dry weight and decreased with sediment depth and movement from the southern to the northern sites. Among the targeted PAHs, phenanthrene was relatively abundant in all sediments. The 16S rRNA gene of the total environmental DNA was analyzed with Illumina high-throughput sequencing (IHTS) to determine the diversity of bacteria involved in PAH degradation in situ. The potential degraders including Cycloclasticus, Pseudomonas, Halomonas, Pseudoalteromonas, Marinomonas, Bacillus, Dietzia, Colwellia, Acinetobacter, Alcanivorax, Salinisphaera and Shewanella, with Dietzia as the most abundant, occurred in all sediment samples. Meanwhile, enrichment with PAHs was initiated onboard and transferred to the laboratory for further enrichment and to obtain the degrading consortia. Most of the abovementioned bacteria in addition to Hahella, Oleispira, Oceanobacter and Hyphomonas occurred alternately as predominant members in the enrichment cultures from different sediments based on IHTS and PCR-DGGE analysis. To reconfirm their role in PAH degradation, 40 different bacteria were isolated and characterized, among which Cycloclasticus Pseudomonas showed the best degradation capability under low temperatures. Taken together, PAHs and PAH-degrading bacteria were widespread in the deep-sea sediments of the Arctic Ocean. We propose that bacteria of Cycloclasticus, Pseudomonas, Pseudoalteromonas, Halomonas, Marinomonas and Dietzia may

  9. A new NDVI measure that overcomes data sparsity in cloud-covered regions predicts annual variation in ground-based estimates of high arctic plant productivity

    Science.gov (United States)

    Rune Karlsen, Stein; Anderson, Helen B.; van der Wal, René; Bremset Hansen, Brage

    2018-02-01

    Efforts to estimate plant productivity using satellite data can be frustrated by the presence of cloud cover. We developed a new method to overcome this problem, focussing on the high-arctic archipelago of Svalbard where extensive cloud cover during the growing season can prevent plant productivity from being estimated over large areas. We used a field-based time-series (2000-2009) of live aboveground vascular plant biomass data and a recently processed cloud-free MODIS-Normalised Difference Vegetation Index (NDVI) data set (2000-2014) to estimate, on a pixel-by-pixel basis, the onset of plant growth. We then summed NDVI values from onset of spring to the average time of peak NDVI to give an estimate of annual plant productivity. This remotely sensed productivity measure was then compared, at two different spatial scales, with the peak plant biomass field data. At both the local scale, surrounding the field data site, and the larger regional scale, our NDVI measure was found to predict plant biomass (adjusted R 2 = 0.51 and 0.44, respectively). The commonly used ‘maximum NDVI’ plant productivity index showed no relationship with plant biomass, likely due to some years having very few cloud-free images available during the peak plant growing season. Thus, we propose this new summed NDVI from onset of spring to time of peak NDVI as a proxy of large-scale plant productivity for regions such as the Arctic where climatic conditions restrict the availability of cloud-free images.

  10. Estimation of the soil heat flux/net radiation ratio based on spectral vegetation indexes in high-latitude Arctic areas

    International Nuclear Information System (INIS)

    Jacobsen, A.; Hansen, B.U.

    1999-01-01

    The vegetation communities in the Arctic environment are very sensitive to even minor climatic variations and therefore the estimation of surface energy fluxes from high-latitude vegetated areas is an important subject to be pursued. This study was carried out in July-August and used micro meteorological data, spectral reflectance signatures, and vegetation biomass to establish the relation between the soil heat flux/net radiation (G / Rn) ratio and spectral vegetation indices (SVIs). Continuous measurements of soil temperature and soil heat flux were used to calculate the surface ground heat flux by use of conventional methods, and the relation to surface temperature was investigated. Twenty-seven locations were established, and six samples per location, including the measurement of the surface temperature and net radiation to establish the G/Rn ratio and simultaneous spectral reflectance signatures and wet biomass estimates, were registered. To obtain regional reliability, the locations were chosen in order to represent the different Arctic vegetation communities in the study area; ranging from dry tundra vegetation communities (fell fields and dry dwarf scrubs) to moist/wet tundra vegetation communities (snowbeds, grasslands and fens). Spectral vegetation indices, including the simple ratio vegetation index (RVI) and the normalized difference vegetation index (NDVI), were calculated. A comparison of SVIs to biomass proved that RVI gave the best linear expression, and NDVI the best exponential expression. A comparison of SVIs and the surface energy flux ratio G / Rn proved that NDVI gave the best linear expression. SPOT HRV images from July 1989 and 1992 were used to map NDVI and G / Rn at a regional scale. (author)

  11. Arctic carbon cycling

    NARCIS (Netherlands)

    Christensen, Torben R; Rysgaard, SØREN; Bendtsen, JØRGEN; Else, Brent; Glud, Ronnie N; van Huissteden, J.; Parmentier, F.J.W.; Sachs, Torsten; Vonk, J.E.

    2017-01-01

    The marine Arctic is considered a net carbon sink, with large regional differences in uptake rates. More regional modelling and observational studies are required to reduce the uncertainty among current estimates. Robust projections for how the Arctic Ocean carbon sink may evolve in the future are

  12. ROLE OF DIAMOND SECONDARY EMITTERS IN HIGH BRIGHTNESS ELECTRON SOURCES

    International Nuclear Information System (INIS)

    2005-01-01

    In this paper we explore the possibility of using diamond secondary emitter in a high average current electron injector to amplify the current from the photocathode and to isolate the cathode and the injector from each other to increase the life time of the cathode and preserve the performance of the injector. Secondary electron yield of 225 and current density of 0.8 a/cm 2 have been measured in the transmission mode from type 2 a natural diamond. Although the diamond will be heated during normal operation in the injector, calculations indicate that by cryogenically cooling the diamond, the temperature gradient along the diamond can be maintained within the acceptable range. The electron energy and temporal distributions are expected to be narrow from this device resulting in high brightness beams. Plans are underway to measure the SEY in emission mode, fabricate photocathode-diamond capsule and test diamond and capsule in superconducting RF injector

  13. High power electron accelerators for flue gas treatment

    International Nuclear Information System (INIS)

    Zimek, Z.

    2011-01-01

    Flue gas treatment process based on electron beam application for SO 2 and NO x removal was successfully demonstrated in number of laboratories, pilot plants and industrial demonstration facilities. The industrial scale application of an electron beam process for flue gas treatment requires accelerators modules with a beam power 100-500 kW and electron energy range 0.8-1.5 MeV. The most important accelerator parameters for successful flue gas radiation technology implementation are related to accelerator reliability/availability, electrical efficiency and accelerator price. Experience gained in high power accelerators exploitation in flue gas treatment industrial demonstration facility was described and high power accelerator constructions have been reviewed. (author)

  14. High power electron accelerators for flue gas treatment

    Energy Technology Data Exchange (ETDEWEB)

    Zimek, Z. [Institute of Nuclear Chemistry and Technology, Warsaw (Poland)

    2011-07-01

    Flue gas treatment process based on electron beam application for SO{sub 2} and NO{sub x} removal was successfully demonstrated in number of laboratories, pilot plants and industrial demonstration facilities. The industrial scale application of an electron beam process for flue gas treatment requires accelerators modules with a beam power 100-500 kW and electron energy range 0.8-1.5 MeV. The most important accelerator parameters for successful flue gas radiation technology implementation are related to accelerator reliability/availability, electrical efficiency and accelerator price. Experience gained in high power accelerators exploitation in flue gas treatment industrial demonstration facility was described and high power accelerator constructions have been reviewed. (author)

  15. Arctic Sea Level Reconstruction

    DEFF Research Database (Denmark)

    Svendsen, Peter Limkilde

    Reconstruction of historical Arctic sea level is very difficult due to the limited coverage and quality of tide gauge and altimetry data in the area. This thesis addresses many of these issues, and discusses strategies to help achieve a stable and plausible reconstruction of Arctic sea level from...... 1950 to today.The primary record of historical sea level, on the order of several decades to a few centuries, is tide gauges. Tide gauge records from around the world are collected in the Permanent Service for Mean Sea Level (PSMSL) database, and includes data along the Arctic coasts. A reasonable...... amount of data is available along the Norwegian and Russian coasts since 1950, and most published research on Arctic sea level extends cautiously from these areas. Very little tide gauge data is available elsewhere in the Arctic, and records of a length of several decades,as generally recommended for sea...

  16. Research with Arctic peoples

    DEFF Research Database (Denmark)

    Smith, H Sally; Bjerregaard, Peter; Chan, Hing Man

    2006-01-01

    Arctic peoples are spread over eight countries and comprise 3.74 million residents, of whom 9% are indigenous. The Arctic countries include Canada, Finland, Greenland (Denmark), Iceland, Norway, Russia, Sweden and the United States. Although Arctic peoples are very diverse, there are a variety...... of environmental and health issues that are unique to the Arctic regions, and research exploring these issues offers significant opportunities, as well as challenges. On July 28-29, 2004, the National Heart, Lung, and Blood Institute and the Canadian Institutes of Health Research co-sponsored a working group...... entitled "Research with Arctic Peoples: Unique Research Opportunities in Heart, Lung, Blood and Sleep Disorders". The meeting was international in scope with investigators from Greenland, Iceland and Russia, as well as Canada and the United States. Multiple health agencies from Canada and the United States...

  17. Consequences of future increased Arctic runoff on Arctic Ocean stratification, circulation, and sea ice cover

    OpenAIRE

    Nummelin, Aleksi; Ilicak, Mehmet; Li, Camille; Smedsrud, Lars Henrik

    2016-01-01

    The Arctic Ocean has important freshwater sources including river runoff, low evaporation, and exchange with the Pacific Ocean. In the future, we expect even larger freshwater input as the global hydrological cycle accelerates, increasing high-latitude precipitation, and river runoff. Previous modeling studies show some robust responses to high-latitude freshwater perturbations, including a strengthening of Arctic stratification and a weakening of the large-scale ocean circulation...

  18. Migration and breeding biology of arctic terns in Greenland

    DEFF Research Database (Denmark)

    Egevang, Carsten

    (Sandøen) in high-Arctic Northeast Greenland. The level of knowledge of the Arctic tern in Greenland before 2002 was to a large extent poor, with aspects of its biology being completely unknown in the Greenland population. This thesis presents novel findings for the Arctic tern, both on an international...... scale and on a national scale. The study on Arctic tern migration (Manus I) – the longest annual migration ever recorded in any animal – is a study with an international appeal. The study documented how Greenland and Iceland breeding terns conduct the roundtrip migration to the Weddell Sea in Antarctica...

  19. Thermalisation of high energy electrons and positrons in water vapour

    Science.gov (United States)

    Munoz, A.; Blanco, F.; Limao-Vieira, P.; Thorn, P. A.; Brunger, M. J.; Buckman, S. J.; Garcia, G.

    2008-07-01

    In this study we describe a method to simulate single electron tracks of electrons in molecular gases, particularly in water vapour, from relatively high energies, where Born (Inokuti 1971) approximation is supposed to be valid, down to thermal energies paying special attention to the low energy secondary electrons which are abundantly generated along the energy degradation procedure. Experimental electron scattering cross sections (Munoz et al. 2007) and energy loss spectra (Thorn et al. 2007) have been determined, where possible, to be used as input parameters of the simulating program. These experimental data have been complemented with optical potential calculation (Blanco and Garcia 2003) providing a complete set of interaction probability functions for each type of collision which could take place in the considered energy range: elastic, ionization, electronic excitation, vibrational and rotational excitation. From the simulated track structure (Munoz et al. 2005) information about energy deposition and radiation damage at the molecular level can be derived. A similar procedure is proposed to the study of single positron tracks in gases. Due to the lack of experimental data for positron interaction with molecules, especially for those related to energy loss and excitation cross sections, some distribution probability data have been derived from those of electron scattering by introducing positron characteristics as positroniun formation. Preliminary results for argon are presented discussing also the utility of the model to biomedical applications based on positron emitters.

  20. Consideration of Relativistic Dynamics in High-Energy Electron Coolers

    CERN Document Server

    Bruhwiler, David L

    2005-01-01

    A proposed electron cooler for RHIC would use ~55 MeV electrons to cool fully-ionized 100 GeV/nucleon gold ions.* At two locations in the collider ring, the electrons and ions will co-propagate for ~13 m, with velocities close to c and gamma>100. To lowest-order, one can Lorentz transform all physical quantities into the beam frame and calculate the dynamical friction forces assuming a nonrelativisitc, electrostatic plasma. However, we show that nonlinear space charge forces of the bunched electron beam on the ions must be calculated relativistically, because an electrostatic beam-frame calculation is not valid for such short interaction times. The validity of nonrelativistic friction force calculations must also be considered. Further, the transverse thermal velocities of the high-charge (~20 nC) electron bunch are large enough that some electrons have marginally relativistic velocities, even in the beam frame. Hence, we consider relativistic binary collisions – treating the model problem of ...

  1. Density-dependent electron transport and precise modeling of GaN high electron mobility transistors

    Energy Technology Data Exchange (ETDEWEB)

    Bajaj, Sanyam, E-mail: bajaj.10@osu.edu; Shoron, Omor F.; Park, Pil Sung; Krishnamoorthy, Sriram; Akyol, Fatih; Hung, Ting-Hsiang [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Reza, Shahed; Chumbes, Eduardo M. [Raytheon Integrated Defense Systems, Andover, Massachusetts 01810 (United States); Khurgin, Jacob [Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Rajan, Siddharth [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Department of Material Science and Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

    2015-10-12

    We report on the direct measurement of two-dimensional sheet charge density dependence of electron transport in AlGaN/GaN high electron mobility transistors (HEMTs). Pulsed IV measurements established increasing electron velocities with decreasing sheet charge densities, resulting in saturation velocity of 1.9 × 10{sup 7 }cm/s at a low sheet charge density of 7.8 × 10{sup 11 }cm{sup −2}. An optical phonon emission-based electron velocity model for GaN is also presented. It accommodates stimulated longitudinal optical (LO) phonon emission which clamps the electron velocity with strong electron-phonon interaction and long LO phonon lifetime in GaN. A comparison with the measured density-dependent saturation velocity shows that it captures the dependence rather well. Finally, the experimental result is applied in TCAD-based device simulator to predict DC and small signal characteristics of a reported GaN HEMT. Good agreement between the simulated and reported experimental results validated the measurement presented in this report and established accurate modeling of GaN HEMTs.

  2. Density-dependent electron transport and precise modeling of GaN high electron mobility transistors

    International Nuclear Information System (INIS)

    Bajaj, Sanyam; Shoron, Omor F.; Park, Pil Sung; Krishnamoorthy, Sriram; Akyol, Fatih; Hung, Ting-Hsiang; Reza, Shahed; Chumbes, Eduardo M.; Khurgin, Jacob; Rajan, Siddharth

    2015-01-01

    We report on the direct measurement of two-dimensional sheet charge density dependence of electron transport in AlGaN/GaN high electron mobility transistors (HEMTs). Pulsed IV measurements established increasing electron velocities with decreasing sheet charge densities, resulting in saturation velocity of 1.9 × 10 7  cm/s at a low sheet charge density of 7.8 × 10 11  cm −2 . An optical phonon emission-based electron velocity model for GaN is also presented. It accommodates stimulated longitudinal optical (LO) phonon emission which clamps the electron velocity with strong electron-phonon interaction and long LO phonon lifetime in GaN. A comparison with the measured density-dependent saturation velocity shows that it captures the dependence rather well. Finally, the experimental result is applied in TCAD-based device simulator to predict DC and small signal characteristics of a reported GaN HEMT. Good agreement between the simulated and reported experimental results validated the measurement presented in this report and established accurate modeling of GaN HEMTs

  3. Status and Impacts of Arctic Freshwater Export

    Science.gov (United States)

    Haine, T. W. N.

    2017-12-01

    Large freshwater anomalies clearly exist in the Arctic Ocean. For example, liquid freshwater has accumulated in the Beaufort Gyre in the decade of the 2000s compared to 1980-2000, with an extra ≈5000 km3—about 25%—being stored. The sources of freshwater to the Arctic from precipitation and runoff have increased between these periods (most of the evidence comes from models). Despite flux increases from 2001 to 2011, it is uncertain if the marine freshwater source through Bering Strait for the 2000s has changed, as observations in the 1980s and 1990s are incomplete. The marine freshwater fluxes draining the Arctic through Fram and Davis straits are also insignificantly different. In this way, the balance of sources and sinks of freshwater to the Arctic, Canadian Arctic Archipelago (CAA), and Baffin Bay shifted to about 1200±730 km3yr-1 freshening the region, on average, during the 2000s. The observed accumulation of liquid freshwater is consistent with this increased supply and the loss of freshwater from sea ice (Figure, right). Evidence exists that such discharges can impact the Atlantic meridional overturning circulation, and hence Atlantic sector climate. Nevertheless, it appears that the observed AMOC variability since 2004, when high quality measurements began, is not attributable to anthropogenic influence. This work is based on, and updated from, Haine et al. (2015), Carmack et al. (2016), and Haine (2016). Haine, T. W. N. Ocean science: Vagaries of Atlantic overturning. Nature Geoscience, 9, 479-480, 10.1038/ngeo2748, 2016. T. W. N. Haine et al., Arctic Freshwater Export: Status, Mechanisms, and Prospects, Global Planetary Change, 125, 13-35, 10.1016/j.glopacha.2014.11.013, 2015. E. Carmack et al., Fresh water and its role in the Arctic Marine System: sources, disposition, storage, export, and physical and biogeochemical consequences in the Arctic and global oceans. J. G. Res. Biogeosciences, 10.1002/2015JG003140, 2016.

  4. Structure Identification in High-Resolution Transmission Electron Microscopic Images

    DEFF Research Database (Denmark)

    Vestergaard, Jacob Schack; Kling, Jens; Dahl, Anders Bjorholm

    2014-01-01

    A connection between microscopic structure and macroscopic properties is expected for almost all material systems. High-resolution transmission electron microscopy is a technique offering insight into the atomic structure, but the analysis of large image series can be time consuming. The present ...

  5. Ultra-stretchable Interconnects for high-density stretchable electronics

    NARCIS (Netherlands)

    Shafqat, S.; Hoefnagels, J.P.M.; Savov, A.; Joshi, S.; Dekker, R.; Geers, M.G.D.

    2017-01-01

    The exciting field of stretchable electronics (SE) promises numerous novel applications, particularly in-body and medical diagnostics devices. However, future advanced SE miniature devices will require high-density, extremely stretchable interconnects with micron-scale footprints, which calls for

  6. Scaling laws in high energy electron-nuclear processes

    International Nuclear Information System (INIS)

    Chemtob, M.

    1980-11-01

    We survey the parton model description of high momentum transfer electron scattering processes with nuclei. We discuss both nucleon and quark parton models and confront the patterns of scaling laws violations, induced by binding effects, in the former, and perturbative QCD effects, in the latter

  7. High-Temperature Electronics: A Role for Wide Bandgap Semiconductors?

    Science.gov (United States)

    Neudeck, Philip G.; Okojie, Robert S.; Chen, Liang-Yu

    2002-01-01

    It is increasingly recognized that semiconductor based electronics that can function at ambient temperatures higher than 150 C without external cooling could greatly benefit a variety of important applications, especially-in the automotive, aerospace, and energy production industries. The fact that wide bandgap semiconductors are capable of electronic functionality at much higher temperatures than silicon has partially fueled their development, particularly in the case of SiC. It appears unlikely that wide bandgap semiconductor devices will find much use in low-power transistor applications until the ambient temperature exceeds approximately 300 C, as commercially available silicon and silicon-on-insulator technologies are already satisfying requirements for digital and analog very large scale integrated circuits in this temperature range. However, practical operation of silicon power devices at ambient temperatures above 200 C appears problematic, as self-heating at higher power levels results in high internal junction temperatures and leakages. Thus, most electronic subsystems that simultaneously require high-temperature and high-power operation will necessarily be realized using wide bandgap devices, once the technology for realizing these devices become sufficiently developed that they become widely available. Technological challenges impeding the realization of beneficial wide bandgap high ambient temperature electronics, including material growth, contacts, and packaging, are briefly discussed.

  8. Human enamel structure studied by high resolution electron microscopy

    International Nuclear Information System (INIS)

    Wen, S.L.

    1989-01-01

    Human enamel structural features are characterized by high resolution electron microscopy. The human enamel consists of polycrystals with a structure similar to Ca10(PO4)6(OH)2. This article describes the structural features of human enamel crystal at atomic and nanometer level. Besides the structural description, a great number of high resolution images are included. Research into the carious process in human enamel is very important for human beings. This article firstly describes the initiation of caries in enamel crystal at atomic and unit-cell level and secondly describes the further steps of caries with structural and chemical demineralization. The demineralization in fact, is the origin of caries in human enamel. The remineralization of carious areas in human enamel has drawn more and more attention as its potential application is realized. This process has been revealed by high resolution electron microscopy in detail in this article. On the other hand, the radiation effects on the structure of human enamel are also characterized by high resolution electron microscopy. In order to reveal this phenomenon clearly, a great number of electron micrographs have been shown, and a physical mechanism is proposed. 26 references

  9. The highly reintegrative approach of electronic monitoring in the Netherlands

    NARCIS (Netherlands)

    Boone, M.M.; Kooij, van der M.; Rap, S.E.

    2017-01-01

    This contribution describes the way electronic monitoring (EM) is organized and implemented in the Netherlands. It will become clear that the situation in the Netherlands is characterized by, in particular, two features. The application of EM is highly interwoven with the Probation Service and its

  10. Emission and absorption of CO2 during the sea ice formation and melting in the high Arctic

    Directory of Open Access Journals (Sweden)

    A. P. Nedashkovsky

    2012-01-01

    Full Text Available The carbonate system of the Arctic sea ice is considered. The observations were conducted in the Nansen Basin at the drifting station North Pole-35 in 2007–2008. It was found that total alkalinity – salinity ratio (TA/S and total inorganic carbon – salinity ratio (TC/S as well as TA/TC ratio in the ice column and seawater column are similar. The deviations from that pattern were observed in the upper thin layer of the young and first-year ice and in the ice snow cap. The TA/TC ratio (equals to ~2 in the ice snow cap was related with the calcium hydrocarbonate decay and CO₂ removal. It was shown that CO₂ removal was due to its emission into the atmosphere. The CO₂ flux was equal to ~0.02 mol/m² for season. The water formed during melting of the first-year ice was significantly under saturated of CO₂ and hence it may be a sink of 0.05 0.07 mol/m² of the atmospheric CO₂ per season.

  11. Relationship of cyanobacterial and algal assemblages with vegetation in the high Arctic tundra (West Spitsbergen, Svalbard Archipelago

    Directory of Open Access Journals (Sweden)

    Richter Dorota

    2015-09-01

    Full Text Available The paper presents the results of a study of cyanobacteria and green algae assemblages occurring in various tundra types determined on the basis of mosses and vascular plants and habitat conditions. The research was carried out during summer in the years 2009-2013 on the north sea-coast of Hornsund fjord (West Spitsbergen, Svalbard Archipelago. 58 sites were studied in various tundra types differing in composition of vascular plants, mosses and in trophy and humidity. 141 cyanobacteria and green algae were noted in the research area in total. Cyanobacteria and green algae flora is a significant element of many tundra types and sometimes even dominate there. Despite its importance, it has not been hitherto taken into account in the description and classification of tundra. The aim of the present study was to demonstrate the legitimacy of using phycoflora in supplementing the descriptions of hitherto described tundra and distinguishing new tundra types. Numeric hierarchical-accumulative classification (MVSP 3.1 software methods were used to analyze the cyanobacterial and algal assemblages and their co-relations with particular tundra types. The analysis determined dominant and distinctive species in the communities in concordance with ecologically diverse types of tundra. The results show the importance of these organisms in the composition of the vegetation of tundra types and their role in the ecosystems of this part of the Arctic.

  12. Recent dynamics of arctic and sub-arctic vegetation

    International Nuclear Information System (INIS)

    Epstein, Howard E; Myers-Smith, Isla; Walker, Donald A

    2013-01-01

    We present a focus issue of Environmental Research Letters on the ‘Recent dynamics of arctic and sub-arctic vegetation’. The focus issue includes three perspective articles (Verbyla 2011 Environ. Res. Lett. 6 041003, Williams et al 2011 Environ. Res. Lett. 6 041004, Loranty and Goetz 2012 Environ. Res. Lett. 7 011005) and 22 research articles. The focus issue arose as a result of heightened interest in the response of high-latitude vegetation to natural and anthropogenic changes in climate and disturbance regimes, and the consequences that these vegetation changes might have for northern ecosystems. A special session at the December 2010 American Geophysical Union Meeting on the ‘Greening of the Arctic’ spurred the call for papers. Many of the resulting articles stem from intensive research efforts stimulated by International Polar Year projects and the growing acknowledgment of ongoing climate change impacts in northern terrestrial ecosystems. (synthesis and review)

  13. Analysis of electron cyclotron emission spectra of high electron temperature, supershot plasmas in TFTR

    International Nuclear Information System (INIS)

    Taylor, G.; Arunasalam, V.; Efthimion, P.C.; Grek, B.

    1993-01-01

    A primary objective of the TFTR program since 1986 has been the study and optimization of deuterium Supershot plasmas. These plasmas are predominantly heated by 90-110 keV neutral deuterium beams (P NBI /P OH >30), central ion temperatures are ∝30 keV and central electron temperatures from ECE (T ECE ) often exceed 10 keV. Central electron temperature data measured with a TV Thomson scattering (TVTS) system (T TVTS ) during the period 1987-1990 have been compared with data from three different ECE instruments on TFTR. Although T ECE ∝T TVTS for temperatures below 6 keV, there is a systematically increasing disagreement at higher electron temperatures, with T ECE ∝1.2 T TVTS for T TVTS in the range 9-10 keV. Recent theoretical work on the ECE radiation temperature of non-equilibrium plasmas indicates that for a bi-Maxwellian electron velocity distribution with a ratio of tail to bulk electron density η, a bulk temperature T b , and a hot tail temperature T h , the perpendicular ECE radiation temperature is given by T ECE ∝T b {1+η(T h /T b )}, for η ECE would be enhanced over T TVTS by a factor which depends on η and T h . This paper investigates whether the discrepancy between T TVTS and T ECE seen in TFTR Supershots at high electron temperatures is due to the presence of a hot electron tail component. The extraordinary mode ECE spectrum at the second, third and fourth harmonics is measured on the horizontal midplane by an absolutely calibrated ECE Michelson interferometer. This ECE spectrum is compared with the output from a time-independent transport code with relativistic opacity which solves the three-dimensional ECE radiation transport in a toroidally symmetric, two-dimensional geometry and uses measured electron density and temperature profiles from the TVTS system. (orig.)

  14. Development of an electron gun for high power CW electron linac (1). Beam experiment for basic performance of electron gun

    International Nuclear Information System (INIS)

    Yamazaki, Yoshio; Nomura, Masahiro; Komata, Tomoki

    1999-05-01

    Presently, the Beam Group of Oarai Engineering Center in Japan Nuclear Cycle Development Institute (JNC) completed the high power CW electron linac. Then we started full-scale beam experiments after the government permission for a radiation equipment had given last January. Measurements of basic performance for the mesh-grid type electron gun have been done to launch stable beam at 300 mA peak current downstream of the accelerator. These experiments disclosed to increase beam loss in the electron gun in some cases of voltage supplied the mesh-grid in spite of same beam current from gun. Consequently, we could find the best condition for mesh-grid voltage and heater current to supply stable beam at 300 mA peak current for accelerator study. (author)

  15. BANSHEE: High-voltage repetitively pulsed electron-beam driver

    International Nuclear Information System (INIS)

    VanHaaften, F.

    1992-01-01

    BANSHEE (Beam Accelerator for a New Source of High-Energy Electrons) this is a high-voltage modulator is used to produce a high-current relativistic electron beam for high-power microwave tube development. The goal of the BANSHEE research is first to achieve a voltage pulse of 700--750 kV with a 1-μs pulse width driving a load of ∼100 Ω, the pulse repetition frequency (PRF) of a few hertz. The ensuing goal is to increase the pulse amplitude to a level approaching 1 MV. We conducted tests using half the modulator with an output load of 200 Ω, up to a level of ∼650 kV at a PRF of 1 Hz and 525 kV at a PRF of 5 Hz. We then conducted additional testing using the complete system driving a load of ∼100 Ω

  16. High resolution electron attachment to molecules of atmospheric relevance

    International Nuclear Information System (INIS)

    Senn, G.

    2000-10-01

    This Ph.D. thesis is divided into three parts. The first is an introduction into the field of electron attachment. In the second part the experimental apparatus is described, and in the third part the results are presented. In the present thesis molecules were chosen for our investigations that are not only of academic interest but that also play an important role for applications or even the life on this planet. All the molecules studied in this work are of atmospheric relevance. NO, and OClO, are involved in the ozone depletion of the stratosphere. The D-layer of the ionosphere is an upper boundary of the ozone layer, therefore the interaction of the electrons from the D-layer with O 3 might play an important role for the chemistry in that part of the atmosphere. Especially the interaction of slow electrons (that will be present in the D-layer in large numbers) with ozone was emphasized in the present study. The production of O - and O 2 - by dissociative electron attachment to ozone was measured for incident electron energies between 0 and 10eV. A previously unobserved sharp structure was discovered in the formation of O - ions for electrons with zero kinetic energy. This additional cross section peak has important consequences for the role of ozone in the anion formation process in the ionosphere. Since OClO is a night time reservoir for chlorine atoms (Cl) and chlorine monoxide (ClO) both of which play a critical role in the depletion of the stratospheric ozone, we have studied negative ion formation following electron impact (0-10eV) to OClO. Despite its atmospheric relevance the mechanism of dissociative electron attachment (DEA) to NO is still a matter of controversy. DEA was studied at high energy resolution and with a kinetic-energy analysis of the O - fragment in two independent crossed electron-molecular-beam experiments. The DEA cross section exhibits a vertical onset near 7.45eV that corresponds to the energy threshold of the DEA channel O - ( 2 P

  17. Possibility of some radionuclides production using high energy electron Bremsstrahlung

    International Nuclear Information System (INIS)

    Balzhinnyam, N.; Belov, A.G.; Gehrbish, Sh; Maslov, O.D.; Shvetsov, V.N.; Ganbold, G.

    2008-01-01

    The method of some radionuclides production using high energy Bremsstrahlung of electron accelerators and determination of photonuclear reaction yield and specific activities for some radionuclides is described. Photonuclear reaction yield and specific activities for some radionuclides are determined for 117m Sn, 111 In and 195m Pt. Based on the experimental data obtained at low energy (E e- e- = 75 MeV) of the IREN facility (FLNR, JINR) at irradiation of high purity platinum and tin metals

  18. Inclusive quasielastic and deep inelastic electron scattering at high energies

    International Nuclear Information System (INIS)

    Day, D.B.

    1990-01-01

    With high electron energies a kinematic regime can be reached where it will be possible to separate quasielastic and deep inelastic scattering. We present a short description of these processes which dominate the inclusive spectrum. Using the highest momentum transfer data available to guide our estimates, we give the kinematic requirements and the cross sections expected. These results indicate that inclusive scattering at high q has a yet unfilled potential. 18 refs., 13 figs

  19. The Physics and Applications of High Brightness Electron Beams

    Science.gov (United States)

    Palumbo, Luigi; Rosenzweig, J.; Serafini, Luca

    2007-09-01

    Plenary sessions. RF deflector based sub-Ps beam diagnostics: application to FEL and advanced accelerators / D. Alesini. Production of fermtosecond pulses and micron beam spots for high brightness electron beam applications / S.G. Anderson ... [et al.]. Wakefields of sub-picosecond electron bunches / K.L.F. Bane. Diamond secondary emitter / I. Ben-Zvi ... [et al.]. Parametric optimization for an X-ray free electron laser with a laser wiggler / R. Bonifacio, N. Piovella and M.M. Cola. Needle cathodes for high-brightness beams / C.H. Boulware ... [et al.]. Non linear evolution of short pulses in FEL cascaded undulators and the FEL harmonic cascade / L. Giannessi and P. Musumeci. High brightness laser induced multi-meV electron/proton sources / D. Giulietti ... [et al.]. Emittance limitation of a conditioned beam in a strong focusing FEL undulator / Z. Huang, G. Stupakov and S. Reiche. Scaled models: space-charge dominated electron storage rings / R.A. Kishek ... [et al.]. High brightness beam applications: energy recovered linacs / G.A. Krafft. Maximizing brightness in photoinjectors / C. Limborg-Deprey and H. Tomizawa. Ultracold electron sources / O.J. Luiten ... [et al.]. Scaling laws of structure-based optical accelerators / A. Mizrahi, V. Karagodsky and L. Schächter. High brightness beams-applications to free-electron lasers / S. Reiche. Conception of photo-injectors for the CTF3 experiment / R. Roux. Superconducting RF photoinjectors: an overview / J. Sekutowicz. Status and perspectives of photo injector developments for high brightness beams / F. Stephan. Results from the UCLA/FNLP underdense plasma lens experiment / M.C. Thompson ... [et al.]. Medical application of multi-beam compton scattering monochromatic tunable hard X-ray source / M. Uesaka ... [et al.]. Design of a 2 kA, 30 fs RF-photoinjector for waterbag compression / S.B. Van Der Geer, O.J. Luiten and M.J. De Loos. Proposal for a high-brightness pulsed electron source / M. Zolotorev ... [et al

  20. High-pressure electron-resonance studies of electronic, magnetic, and structural phase transitions. Progress report

    International Nuclear Information System (INIS)

    Pifer, J.H.; Croft, M.C.

    1983-01-01

    Research is described in development of a high-pressure electron-resonance probe capable of operating down to 1.5 0 K temperatures. The apparatus has been used to measure the EPR of a sample of DPPH at room temperature and zero pressure. EPR has been used to measure valence field instabilities in alloy systems. Studies have been done on metal-insulator transitions at high pressure, and are briefly described

  1. Survey on neutron production by electron beam from high power CW electron linear accelerator

    International Nuclear Information System (INIS)

    Toyama, S.

    1999-04-01

    In Japan Nuclear Cycle Development Institute, the development of high current CW electron linear accelerator is in progress. It is possible for an accelerator to produce neutrons by means of a spallation and photo nuclear reactions. Application of neutron beam produced by bremsstrahlung is one of ways of the utilization for high current electron accelerator. It is actual that many electron linear accelerators which maximum energy is higher than a few hundreds MeV are used as neutron sources. In this report, an estimate of neutron production is evaluated for high current CW electron linear accelerator. The estimate is carried out by 10 MeV beam which is maximum energy limited from the regulation and rather low for neutron production. Therefore, the estimate is also done by 17 and 35 MeV beam which is possible to be accelerated. Beryllium is considered as a target for lower electron energy in addition to Lead target for higher energy, because Beryllium has low threshold energy for neutron production. The evaluation is carried out in account of the target thickness optimized by the radiation length and neutron cross section reducing the energy loss for both of electron and neutron, so as to get the maximum number of neutrons. The result of the calculations shows neutron numbers 1.9 x 10 10 , 6.1 x 10 13 and 4.8 x 10 13 (n/s), respectively, for 10, 17, and 35 MeV with low duty. The thermal removal from the target is one of critical points. The additional shielding and cooling system is necessary in order to endure radiation. A comparison with other facilities are also carried out. The estimate of neutron numbers suggests the possibility to be applied for neutron radiography and measurement of nuclear data by means of Lead spectrometer, for example. (author)

  2. High speed electronic imaging application in aeroballistic research

    International Nuclear Information System (INIS)

    Brown, R.R.; Parker, J.R.

    1984-01-01

    Physical and temporal restrictions imposed by modern aeroballistics have pushed imaging technology to the point where special photoconductive surfaces and high-speed support electronics are dictated. Specifications for these devices can be formulated by a methodical analysis of critical parameters and how they interact. In terms of system theory, system transfer functions and state equations can be used in optimal coupling of devices to maximize system performance. Application of these methods to electronic imaging at the Eglin Aeroballistics Research Facility is described in this report. 7 references, 14 figures, 1 table

  3. High-Energy Electron Beam Application to Air Pollutants Removal

    International Nuclear Information System (INIS)

    Ighigeanu, D.; Martin, D.; Manaila, E.; Craciun, G.; Calinescu, I.

    2009-01-01

    The advantage of electron beam (EB) process in pollutants removal is connected to its high efficiency to transfer high amount of energy directly into the matter under treatment. Disadvantage which is mostly related to high investment cost of accelerator may be effectively overcome in future as the result of use accelerator new developments. The potential use of medium to high-energy high power EB accelerators for air pollutants removal is demonstrated in [1]. The lower electrical efficiencies of accelerators with higher energies are partially compensated by the lower electron energy losses in the beam windows. In addition, accelerators with higher electron energies can provide higher beam powers with lower beam currents [1]. The total EB energy losses (backscattering, windows and in the intervening air space) are substantially lower with higher EB incident energy. The useful EB energy is under 50% for 0.5 MeV and about 95% above 3 MeV. In view of these arguments we decided to study the application of high energy EB for air pollutants removal. Two electron beam accelerators are available for our studies: electron linear accelerators ALIN-10 and ALID-7, built in the Electron Accelerator Laboratory, INFLPR, Bucharest, Romania. Both accelerators are of traveling-wave type, operating at a wavelength of 10 cm. They utilize tunable S-band magnetrons, EEV M 5125 type, delivering 2 MW of power in 4 μ pulses. The accelerating structure is a disk-loaded tube operating in the 2 mode. The optimum values of the EB peak current IEB and EB energy EEB to produce maximum output power PEB for a fixed pulse duration EB and repetition frequency fEB are as follows: for ALIN-10: EEB = 6.23 MeV; IEB =75 mA; PEB 164 W (fEB = 100 Hz, EB = 3.5 s) and for ALID-7: EEB 5.5 MeV; IEB = 130 mA; PEB = 670 W (fEB = 250 Hz, EB = 3.75 s). This paper presents a special designed installation, named SDI-1, and several representative results obtained by high energy EB application to SO 2 , NOx and VOCs

  4. High quality electron beams from a laser wakefield accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Wiggins, S M; Issac, R C; Welsh, G H; Brunetti, E; Shanks, R P; Anania, M P; Cipiccia, S; Manahan, G G; Aniculaesei, C; Ersfeld, B; Islam, M R; Burgess, R T L; Vieux, G; Jaroszynski, D A [SUPA, Department of Physics, University of Strathclyde, Glasgow (United Kingdom); Gillespie, W A [SUPA, Division of Electronic Engineering and Physics, University of Dundee, Dundee (United Kingdom); MacLeod, A M [School of Computing and Creative Technologies, University of Abertay Dundee, Dundee (United Kingdom); Van der Geer, S B; De Loos, M J, E-mail: m.wiggins@phys.strath.ac.u [Pulsar Physics, Burghstraat 47, 5614 BC Eindhoven (Netherlands)

    2010-12-15

    High quality electron beams have been produced in a laser-plasma accelerator driven by femtosecond laser pulses with a peak power of 26 TW. Electrons are produced with an energy up to 150 MeV from the 2 mm gas jet accelerator and the measured rms relative energy spread is less than 1%. Shot-to-shot stability in the central energy is 3%. Pepper-pot measurements have shown that the normalized transverse emittance is {approx}1{pi} mm mrad while the beam charge is in the range 2-10 pC. The generation of high quality electron beams is understood from simulations accounting for beam loading of the wakefield accelerating structure. Experiments and self-consistent simulations indicate that the beam peak current is several kiloamperes. Efficient transportation of the beam through an undulator is simulated and progress is being made towards the realization of a compact, high peak brilliance free-electron laser operating in the vacuum ultraviolet and soft x-ray wavelength ranges.

  5. A high-energy electron beam ion trap for production of high-charge high-Z ions

    International Nuclear Information System (INIS)

    Knapp, D.A.; Marrs, R.E.; Elliott, S.R.; Magee, E.W.; Zasadzinski, R.

    1993-01-01

    We have developed a new high-energy electron beam ion trap, the first laboratory source of low-energy, few-electron, high-Z ions. We describe the device and report measurements of its performance, including the electron beam diameter, current density and energy, and measurements of the ionization balance for several high-Z elements in the trap. This device opens up a wide range of possible experiments in atomic physics, plasma physics, and nuclear physics. (orig.)

  6. ArcticDEM Validation and Accuracy Assessment

    Science.gov (United States)

    Candela, S. G.; Howat, I.; Noh, M. J.; Porter, C. C.; Morin, P. J.

    2017-12-01

    ArcticDEM comprises a growing inventory Digital Elevation Models (DEMs) covering all land above 60°N. As of August, 2017, ArcticDEM had openly released 2-m resolution, individual DEM covering over 51 million km2, which includes areas of repeat coverage for change detection, as well as over 15 million km2 of 5-m resolution seamless mosaics. By the end of the project, over 80 million km2 of 2-m DEMs will be produced, averaging four repeats of the 20 million km2 Arctic landmass. ArcticDEM is produced from sub-meter resolution, stereoscopic imagery using open source software (SETSM) on the NCSA Blue Waters supercomputer. These DEMs have known biases of several meters due to errors in the sensor models generated from satellite positioning. These systematic errors are removed through three-dimensional registration to high-precision Lidar or other control datasets. ArcticDEM is registered to seasonally-subsetted ICESat elevations due its global coverage and high report accuracy ( 10 cm). The vertical accuracy of ArcticDEM is then obtained from the statistics of the fit to the ICESat point cloud, which averages -0.01 m ± 0.07 m. ICESat, however, has a relatively coarse measurement footprint ( 70 m) which may impact the precision of the registration. Further, the ICESat data predates the ArcticDEM imagery by a decade, so that temporal changes in the surface may also impact the registration. Finally, biases may exist between different the different sensors in the ArcticDEM constellation. Here we assess the accuracy of ArcticDEM and the ICESat registration through comparison to multiple high-resolution airborne lidar datasets that were acquired within one year of the imagery used in ArcticDEM. We find the ICESat dataset is performing as anticipated, introducing no systematic bias during the coregistration process, and reducing vertical errors to within the uncertainty of the airborne Lidars. Preliminary sensor comparisons show no significant difference post coregistration

  7. Research of the Electron Cyclotron Emission with Vortex Property excited by high power high frequency Gyrotron

    Science.gov (United States)

    Goto, Yuki; Kubo, Shin; Tsujimura, Tohru; Takubo, Hidenori

    2017-10-01

    Recently, it has been shown that the radiation from a single electron in cyclotron motion has vortex property. Although the cyclotron emission exists universally in nature, the vortex property has not been featured because this property is normally cancelled out due to the randomness in gyro-phase of electrons and the development of detection of the vortex property has not been well motivated. In this research, we are developing a method to generate the vortex radiation from electrons in cyclotron motion with controlled gyro-phase. Electron that rotates around the uniform static magnetic field is accelerated by right-hand circular polarized (RHCP) radiation resonantly when the cyclotron frequency coincides with the applied RHCP radiation frequency. A large number of electrons can be coherently accelerated in gyro-phase by a RHCP high power radiation so that these electrons can radiate coherent emission with vortex feature. We will show that vortex radiation created by purely rotating electrons for the first time.

  8. Potential ceramics processing applications with high-energy electron beams

    International Nuclear Information System (INIS)

    Struve, K.W.; Turman, B.N.

    1993-01-01

    High-energy, high-current electron beams may offer unique features for processing of ceramics that are not available with any other heat source. These include the capability to instantaneously heat to several centimeters in depth, to preferentially deposit energy in dense, high-z materials, to process at atmospheric pressures in air or other gases, to have large control over heating volume and heating rate, and to have efficient energy conversion. At a recent workshop organized by the authors to explore opportunities for electron beam processing of ceramics, several applications were identified for further development. These were ceramic joining, fabrication of ceramic powders, and surface processing of ceramics. It may be possible to join ceramics by either electron-beam brazing or welding. Brazing with refractory metals might also be feasible. The primary concern for brazing is whether the braze material can wet to the ceramic when rapidly heated by an electron beam. Raw ceramic powders, such as silicon nitride and aluminum nitride, which are difficult to produce by conventional techniques, could possibly be produced by vaporizing metals in a nitrogen atmosphere. Experiments need to be done to verify that the vaporized metal can fully react with the nitrogen. By adjusting beam parameters, high-energy beams can be used to remove surface flaws which are often sites of fracture initiation. They can also be used for surface cleaning. The advantage of electron beams rather than ion beams for this application is that the heat deposition can be graded into the material. The authors will discuss the capabilities of beams from existing machines for these applications and discuss planned experiments

  9. Improved UV-B screening capacity does not prevent negative effects of ambient UV irradiance on PSII performance in High Arctic plants. Results from a six year UV exclusion study

    DEFF Research Database (Denmark)

    Albert, Kristian Rost; Mikkelsen, Teis Nørgaard; Ro-Poulsen, H.

    2010-01-01

    Long-term responses of ambient solar ultraviolet (UV) radiation were investigated on Salix arctica and Vaccinium uliginosum in a High Arctic heath ecosystem in Zackenberg, northeast Greenland. Over a period of six years, UV exclusion was conducted in the growing season by means of filters: 60% UV......, exposing the vegetation to high spring UV-B, and to be present in the future to the degree the ozone layer is not fully recovered....

  10. Signature of electron-phonon interaction in high temperature superconductors

    Directory of Open Access Journals (Sweden)

    Vinod Ashokan

    2011-09-01

    Full Text Available The theory of thermal conductivity of high temperature superconductors (HTS based on electron and phonon line width (life times formulation is developed with Quantum dynamical approach of Green's function. The frequency line width is observed as an extremely sensitive quantity in the transport phenomena of HTS as a collection of large number of scattering processes. The role of resonance scattering and electron-phonon interaction processes is found to be most prominent near critical temperature. The theory successfully explains the spectacular behaviour of high Tc superconductors in the vicinity of transition temperature. A successful agreement between theory and experiment has been obtained by analyzing the thermal conductivity data for the sample La1.8Sr0.2CuO4 in the temperature range 0 − 200K. The theory is equally and successfully applicable to all other high Tc superconductors.

  11. High-brightness electron source driven by laser

    International Nuclear Information System (INIS)

    Zhao Kui; Geng Rongli; Wang Lifang

    1996-01-01

    A DC high-brightness laser driven by photo emissive electron gun is being developed at Beijing University, in order to produce 50∼100 ps electron bunches of high quality. The gun consists of a photocathode preparation chamber and a DC acceleration cavity. Different ways of fabricating photocathode, such as chemical vapor deposition, ion beam implantation and ion beam enhanced deposition, can be adopted. The acceleration gap is designed with the aid of simulation codes EGUN and POISSON. 100 kV DC high voltage is fed to the anode through a careful designed ceramic insulator. The laser system is a mode locked Nd-YAG oscillator proceeded by an amplifier at 10 Hz repetition rate, which can deliver three different wavelength (1064/532/266 nm). The combination of a superconducting cavity with the photocathode preparation chamber is discussed

  12. Research on high performance mirrors for free electron lasers

    International Nuclear Information System (INIS)

    Kitatani, Fumito

    1996-01-01

    For the stable functioning of free electron laser, high performance optical elements are required because of its characteristics. In particular in short wavelength free electron laser, since its gain is low, the optical elements having very high reflectivity are required. Also in free electron laser, since high energy noise light exists, the optical elements must have high optical breaking strength. At present in Power Reactor and Nuclear Fuel Development Corporation, the research for heightening the performance of dielectric multi-layer film elements for short wavelength is carried out. For manufacturing such high performance elements, it is necessary to develop the new materials for vapor deposition, new vapor deposition process, and the techniques of accurate substrate polishing and inspection. As the material that satisfies the requirements, there is diamond-like carbon (DLC) film, of which the properties are explained. As for the manufacture of the DLC films for short wavelength optics, the test equipment for forming the DLC films, the test of forming the DLC films, the change of the film quality due to gas conditions, discharge conditions and substrate materials, and the measurement of the optical breaking strength are reported. (K.I.)

  13. Arctic Climate Systems Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Ivey, Mark D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Robinson, David G. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Boslough, Mark B. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Backus, George A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Peterson, Kara J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); van Bloemen Waanders, Bart G. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Swiler, Laura Painton [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Desilets, Darin Maurice [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Reinert, Rhonda Karen [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-03-01

    This study began with a challenge from program area managers at Sandia National Laboratories to technical staff in the energy, climate, and infrastructure security areas: apply a systems-level perspective to existing science and technology program areas in order to determine technology gaps, identify new technical capabilities at Sandia that could be applied to these areas, and identify opportunities for innovation. The Arctic was selected as one of these areas for systems level analyses, and this report documents the results. In this study, an emphasis was placed on the arctic atmosphere since Sandia has been active in atmospheric research in the Arctic since 1997. This study begins with a discussion of the challenges and benefits of analyzing the Arctic as a system. It goes on to discuss current and future needs of the defense, scientific, energy, and intelligence communities for more comprehensive data products related to the Arctic; assess the current state of atmospheric measurement resources available for the Arctic; and explain how the capabilities at Sandia National Laboratories can be used to address the identified technological, data, and modeling needs of the defense, scientific, energy, and intelligence communities for Arctic support.

  14. Patterning of high mobility electron gases at complex oxide interfaces

    DEFF Research Database (Denmark)

    Trier, Felix; Prawiroatmodjo, G. E. D. K.; von Soosten, Merlin

    2015-01-01

    Oxide interfaces provide an opportunity for electronics. However, patterning of electron gases at complex oxide interfaces is challenging. In particular, patterning of complex oxides while preserving a high electron mobility remains underexplored and inhibits the study of quantum mechanical effects...... of amorphous-LSM (a-LSM) thin films, which acts as a hard mask during subsequent depositions. Strikingly, the patterned modulation-doped interface shows electron mobilities up to ∼8 700 cm2/V s at 2 K, which is among the highest reported values for patterned conducting complex oxide interfaces that usually...... where extended electron mean free paths are paramount. This letter presents an effective patterning strategy of both the amorphous-LaAlO3/SrTiO3 (a-LAO/STO) and modulation-doped amorphous-LaAlO3/La7/8Sr1/8MnO3/SrTiO3 (a-LAO/LSM/STO) oxide interfaces. Our patterning is based on selective wet etching...

  15. High energy electron disinfection of sewage wastewater in flow systems

    Energy Technology Data Exchange (ETDEWEB)

    Miyata, T; Arai, H; Hosono, M; Tokunaga, O; Machi, S [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment; Kondoh, M; Minemura, T; Nakao, A; Seike, Y [Sumitomo Heavy Industries Ltd., Tokyo (Japan)

    1990-01-01

    The disinfection of effluent municipal wastewaters by high-energy electrons in flow systems was studied using an experimental apparatus which has the maximum treatment capacity of 10.8 m{sup 3}/h. An electron accelerator with an accelerating voltage of 2 MV was used. The electron beam current was controlled to deliver the desired doses ranging from 0.05 to 1 kGy. Treatment times were in the range from 0.0022 to 0.051 s. Preliminary experiments with batch system using Petri dish of 100 ml showed that the effectiveness of electron irradiation on inactivation of coliforms was not influenced significantly by factors such as pH, SS, COD, DO and irradiation temperature. The dose required to produce 99.9% kill in the total population presented in wastewater were markedly affected by the thickness of water exposure to electron irradiation; that is, 0.39, 0.4 and 0.44 kGy for the depth of 5, 6 and 7 mm, respectively. The data obtained after a suitable correction for the doses due to the depth dose distribution showed no deviation from an experimental survival curve. Experiments with flow system indicated no measureable effect of the flow rate of wastewaters on the efficiency of disinfection in the range from 0.5 to 3.5 m/s. (author).

  16. Efficient temporal shaping of electron distributions for high-brightness photoemission electron guns

    Directory of Open Access Journals (Sweden)

    Ivan V. Bazarov

    2008-04-01

    Full Text Available To achieve the lowest emittance electron bunches from photoemission electron guns, it is essential to limit the uncorrelated emittance growth due to space charge forces acting on the bunch in the vicinity of the photocathode through appropriate temporal shaping of the optical pulses illuminating the photocathode. We present measurements of the temporal profile of electron bunches from a bulk crystal GaAs photocathode illuminated with 520 nm wavelength pulses from a frequency-doubled Yb-fiber laser. A transverse deflecting rf cavity was used to make these measurements. The measured laser pulse temporal profile and the corresponding electron beam temporal profile have about 30 ps FWHM duration, with rise and fall times of a few ps. GaAs illuminated by 520 nm optical pulses is a prompt emitter within our measurement uncertainty of ∼1  ps rms. Combined with the low thermal emittance of negative electron affinity photocathodes, GaAs is a very suitable photocathode for high-brightness photoinjectors. We also report measurements of the photoemission response time for GaAsP, which show a strong dependence on the quantum efficiency of the photocathode.

  17. Continuous non-marine inputs of per- and polyfluoroalkyl substances to the High Arctic: a multi-decadal temporal record

    Science.gov (United States)

    Pickard, Heidi M.; Criscitiello, Alison S.; Spencer, Christine; Sharp, Martin J.; Muir, Derek C. G.; De Silva, Amila O.; Young, Cora J.

    2018-04-01

    Perfluoroalkyl acids (PFAAs) are persistent, in some cases, bioaccumulative compounds found ubiquitously within the environment. They can be formed from the atmospheric oxidation of volatile precursor compounds and undergo long-range transport (LRT) through the atmosphere and ocean to remote locations. Ice caps preserve a temporal record of PFAA deposition making them useful in studying the atmospheric trends in LRT of PFAAs in polar or mountainous regions, as well as in understanding major pollutant sources and production changes over time. A 15 m ice core representing 38 years of deposition (1977-2015) was collected from the Devon Ice Cap in Nunavut, providing us with the first multi-decadal temporal ice record in PFAA deposition to the Arctic. Ice core samples were concentrated using solid phase extraction and analyzed by liquid and ion chromatography methods. Both perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs) were detected in the samples, with fluxes ranging from air mass transport densities, and comparing temporal trends in deposition with production changes of possible sources, we find that Eurasian sources, particularly from Continental Asia, are large contributors to the global pollutants impacting the Devon Ice Cap. Comparison of PFAAs to their precursors and correlations of PFCA pairs showed that deposition of PFAAs is dominated by atmospheric formation from volatile precursor sources. Major ion analysis confirmed that marine aerosol inputs are unimportant to the long-range transport mechanisms of these compounds. Assessments of deposition, homologue profiles, ion tracers, air mass transport models, and production and regulation trends allow us to characterize the PFAA depositional profile on the Devon Ice Cap and further understand the LRT mechanisms of these persistent pollutants.

  18. Climate change consequences for terrestrial ecosystem processes in NW Greeland: Results from the High Arctic Biocomplexity project

    Science.gov (United States)

    Welker, J. M.; Sullivan, P.; Rogers, M.; Sharp, E. D.; Sletten, R.; Burnham, J. L.; Hallet, B.; Hagedorn, B.; Czimiczk, C.

    2009-12-01

    Greenland is experiencing some of the fastest rates of climate warming across the Arctic including warmer summers and increases in snow fall. The effects of these new states of Greenland are however, uncertain especially for carbon, nitrogen and water biogeochemical processes, soil traits, vegetation growth patterns, mineral nutrition and plant ecophysiological processes. Since 2003 we have conducted a suite of observational and experimental measurements that have been designed to understand the fundamental nature of polar desert, polar semi-desert and fen landscapes in NW Greenland. In addition, we have established a suite of experiments to ascertain ecosystem responses to warming at multiple levels (~2030 and 2050), in conjunction with added summer rain; the consequences of added snow fall (ambient, intermediate and deep) and the effects of increases in nutrient additions (added N, P and N+P), which represent extreme warming conditions. We find that: a) the soil C pools are 6-fold larger than previously measured, b) extremely old C (up to ~30k bp) which has been buried by frost cracking and frost heaving is reaching the modern atmosphere, but in only trace amounts as measured by respired 14CO2, c) warming that simulates 2030, has only a small effect on net C sequestration but warming that simulates 2050 when combined with added summer rain, increases C sequestration by 300%, d) increases in N deposition almost immediately and completely changes the vegetation composition of polar semi-deserts shifting the NDVI values from 0.2 to 0.5 within 2 years. Our findings depict a system that is poised to contribute stronger feedbacks than previously expected as climates in NW Greenland change.

  19. High-resolution reconstruction of Arctic paleoclimate derived from 53 million year old kimberlite-hosted Metasequoia wood

    Science.gov (United States)

    Walker, J. J.; Halfar, J.; Schulze, D.; Gedalof, Z.; Moore, G. W. K.

    2009-04-01

    The recovery of exceptionally well preserved Eocene wood from kimberlite pipes in the Lac de Gras region of the Northwest Territories, Canada, has allowed for the characterization of the local temperature and hydrologic patterns on an annual scale for this arctic ecosystem (present day latitude: 64 deg N). Wood fragments of ancient Metasequoia sp. trees mixed into the crater facies during kimberlite emplacement were recovered from the Ekati and Diavik diamond mines. Wood recovered from the Ekati "Panda" pipe, which has been dated using Rb-Sr age determination at 53.3 +/- 0.6 million years, is unique in that it exhibits extremely low vitrinite reflectance values, comparable to that of modern near-surface peats. The implication is that the wood has undergone minimal thermal or compressional alteration, thus preserving the geochemical signatures originally formed during growth. Ring width measurements representing over 100 years of climate data show congruence between multiple samples, thus enabling the development of a floating master chronology. Patterns contained in this chronology are of particular interest as the early Eocene was characterized by a period of unusual warming that has been compared to modern day climate change. Wood cellulose does not exchange atoms with its surroundings after formation, making it an ideal candidate for stable isotope analysis once it has been separated from associated whole-wood components. A robotic micromilling device was used to collect whole wood samples of latewood from annual tree rings. The α-cellulose in the samples will be isolated and analyzed for δ13C and δ18O, generating a 34-year floating chronology that can be used to reconstruct decadal scale temperature and humidity patterns. Successful application of this technique suggests that a longer Eocene chronology, using additional wood samples recovered from the Panda pipe as well as samples from neighbouring pipes in the Lac de Gras region, can be developed.

  20. High-current electron accelerator for gas-laser pumping

    Energy Technology Data Exchange (ETDEWEB)

    Badaliants, G R; Mamikonian, V A; Nersisian, G Ts; Papanian, V O

    1978-11-26

    A high-current source of pulsed electron beams has been developed for the pumping of UV gas lasers. The parameters of the device are: energy of 0.3-0.7 MeV pulse duration of 30 ns and current density (in a high-pressure laser chamber) of 40-100 A/sq cm. The principal feature of the device is the use of a rectangular cold cathode with incomplete discharge along the surface of the high-permittivity dielectric. Cathodes made of stainless steel, copper, and graphite were investigated.