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  • 1.
    Charalampidis, Charalampos
    et al.
    Bavarian Acad Sci & Humanities, Munich, Germany..
    Fischer, Andrea
    Austrian Acad Sci, Inst Interdisciplinary Mt Res, Innsbruck, Austria..
    Kuhn, Michael
    Univ Innsbruck, Inst Atmospher & Cryospher Sci, Innsbruck, Austria..
    Lambrecht, Astrid
    Bavarian Acad Sci & Humanities, Munich, Germany..
    Mayer, Christoph
    Bavarian Acad Sci & Humanities, Munich, Germany..
    Thomaidis, Konstantinos
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Weber, Markus
    Tech Univ Munich, Chair Photogrammetry & Remote Sensing, Munich, Germany..
    Mass-Budget Anomalies and Geometry Signals of Three Austrian Glaciers2018In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 6, article id UNSP 218Article in journal (Refereed)
    Abstract [en]

    Glacier mass-budget monitoring documents climate fluctuations, provides context for observed glacier-geometry changes, and can provide information on the glaciers' states. We examine the mass-budget series and available geometries of three well-documented glaciers located in the same catchment area less than 10 km from one another in the Austrian Otztal Alps. The altitudinal profiles of the 1981-2010 average specific mass budgets of each glacier serve as climatic reference. We apply these reference mass-budget profiles on all available glacier geometries, thereby retrieving for each glacier reference-climate mass budgets that reveal in a discrete way each glacier's geometric adjustment over time and its impact on mass loss; interpolation of the reference-climate mass budgets over the 1981-2010 period provides the glaciers' geometry signals. The geometric mass-budget anomalies derived with respect to these geometry signals indicate decreasing mass budgets over the 1981-2010 period by 0.020 m water equivalent (w.e.) a(-2), or 31% additional mass loss compared to the centered anomalies derived with respect to the 1981-2010 averages of the conventional mass-budget series. Reference-climate mass budgets with respect to 1981-2010 of older geometries highlight Hintereisferner's adapting geometry by almost continuous retreat since 1850. Further retreat is inevitable as Hintereisferner is the furthest from a steady state amongst the three glaciers. The relatively small Kesselwandferner has been also mostly retreating, while briefly advancing in response to short-term climatic trends. In a stable 1981-2010 climate, Kesselwandferner would relatively quickly reach a steady state. Vernagtferner's geometry since 1979 favors mass loss by thinning, primarily due to extended surge-related mass losses since 1845; this inability to retreat has led to - and will further - Vernagtferner's disintegration.

  • 2.
    Githumbi, Esther N.
    et al.
    Environment Department, York Institute for Tropical Ecosystems, University of York, York, United Kingdom.
    Kariuki, Rebecca
    Environment Department, York Institute for Tropical Ecosystems, University of York, York, United Kingdom.
    Shoemaker, Anna
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Department of Archaeology and Ancient History.
    Courtney Mustaphi, Colin
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Department of Archaeology and Ancient History. Environment Department, York Institute for Tropical Ecosystems, University of York, York, United Kingdom.
    Chuhila, Maxmillian
    Department of History, University of Dar es Salaam, Dar es Salaam, Tanzania.
    Richer, Suzi
    Environment Department, York Institute for Tropical Ecosystems, University of York, York, United Kingdom.; Department of Archaeology, University of York, York, United Kingdom.
    Lane, Paul
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Department of Archaeology and Ancient History. School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, Johannesburg, South Africa.
    Marchant, Rob
    Environment Department, York Institute for Tropical Ecosystems, University of York, York, United Kingdom.
    Pollen, People and Place: Multidisciplinary Perspectives on Ecosystem Change at Amboseli, Kenya2018In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 5, p. 1-26, article id 113Article in journal (Refereed)
    Abstract [en]

    This study presents a multidisciplinary perspective for understanding environmental change and emerging socio-ecological interactions across the Amboseli region of southwestern Kenya. We focus on late Holocene (<5,000 cal yr. BP) changes and continuities reconstructed from sedimentary, archeological, historical records and socio-ecological models. We utilize multi-disciplinary approaches to understand environmental-ecosystem-social interactions over the longue durée and use this to simulate different land use scenarios supporting conservation and sustainable livelihoods using a socio-ecological model. Today the semi-arid Amboseli landscape supports a large livestock and wildlife population, sustained by a wide variety of plants and extensive rangelands regulated by seasonal rainfall and human activity. Our data provide insight into how large-scale and long-term interactions of climate, people, livestock, wildlife and external connections have shaped the ecosystems across the Amboseli landscape. Environmental conditions were dry between ~5,000 and 2,000 cal yr. BP, followed by two wet periods at ~2,100–1,500 and 1,400–800 cal yr. BP with short dry periods; the most recent centuries were characterized by variable climate with alternative dry and wet phases with high spatial heterogeneity. Most evident in paleo and historical records is the changing woody to grass cover ratio, driven by changes in climate and fire regimes entwined with fluctuating elephant, cattle and wild ungulate populations moderated by human activity, including elephant ivory trade intensification. Archeological perspectives on the occupation of different groups (hunter-gatherers, pastoralists, and farmers) in Amboseli region and the relationships between them are discussed. An overview of the known history of humans and elephants, expanding networks of trade, and the arrival and integration of metallurgy, livestock and domesticated crops in the wider region is provided. In recent decades, increased runoff and flooding have resulted in the expansion of wetlands and a reduction of woody vegetation, compounding problems created by increased enclosure and privatization of these landscapes. However, most of the wetlands outside of the protected area are drying up because of the intensified water extraction by the communities surrounding the National Park and on the adjacent mountains areas, who have increased in numbers, become sedentary and diversified land use around the wetlands.

  • 3.
    Guldstrand, Frank
    et al.
    Univ Oslo, Dept Geosci, NJORD Ctr, PGP, Oslo, Norway.
    Galland, Olivier
    Univ Oslo, Dept Geosci, NJORD Ctr, PGP, Oslo, Norway.
    Hallot, Erwan
    Univ Rennes, CNRS, UMR 6118, Geosci Rennes, Rennes, France.
    Burchardt, Steffi
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Experimental Constraints on Forecasting the Location of Volcanic Eruptions from Pre-eruptive Surface Deformation2018In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 6, article id UNSP 7Article in journal (Refereed)
    Abstract [en]

    Volcanic eruptions pose a threat to lives and property when volcano flanks and surroundings are densely populated. The local impact of an eruption depends firstly on its location, whether it occurs near a volcano summit, or down on the flanks. Then forecasting, with a defined accuracy, the location of a potential, imminent eruption would significantly improve the assessment and mitigation of volcanic hazards. Currently, the conventional volcano monitoring methods based on the analysis of surface deformation assesses whether a volcano may erupt but are not implemented to locate imminent eruptions in real time. Here we show how surface deformation induced by ascending eruptive feeders can be used to forecast the eruption location through a simple geometrical analysis. Our analysis builds on the results of 33 scaled laboratory experiments simulating the emplacement of viscous magma intrusions in a brittle, cohesive Coulomb crust under lithostatic stress conditions. The intrusion-induced surface deformation was systematically monitored at high spatial and temporal resolution. In all the experiments, surface deformation preceding the eruptions resulted in systematic uplift, regardless of the intrusion shape. The analysis of the surface deformation patterns leads to the definition of a vector between the center of the uplifted area and the point of maximum uplift, which systematically acted as a precursor to the eruption's location. The temporal evolution of this vector indicated the direction in which the subsequent eruption would occur and ultimately the location itself, irrespective of the feeder shapes. Our findings represent a new approach on how surface deformation on active volcanoes that are not in active rifts could be analysed and used prior to an eruption with a real potential to improve hazard mitigation.

  • 4.
    Gutiérrez Loza, Lucia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Wallin, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Sahlée, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Nilsson, Erik O.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Bange, Hermann
    Koch, Annette
    Rutgersson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Measurement of air-sea methane fluxes in the Baltic Sea using the eddy covariance method2019In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 7, article id 93Article in journal (Refereed)
    Abstract [en]

    Methane (CH4) is the second-most important greenhouse gas in the atmosphere having a significant effect on global climate. The ocean-particularly the coastal regions-have been recognized to be a net source of CH4, however, the constraints on temporal and spatial resolution of CH4 measurements have been the limiting factor to estimate the total oceanic contributions. In this study, the viability of micrometeorological methods for the analysis of CH4 fluxes in the marine environment was evaluated. We present 1 year of semi-continuous eddy covariance measurements of CH4 atmospheric dry mole fractions and air-sea CH4 flux densities at the Ostergarnsholm station at the east coast of the Gotland Island in the central Baltic Sea. The mean annual CH4 flux density was positive, indicating that the region off Gotland is a net source of CH4 to the atmosphere with monthly mean flux densities ranging between -0.1 and 36 nmol m(-2)s(-1). Both the air-water concentration gradient and the wind speed were found to be crucial parameters controlling the flux. The results were in good agreement with other measurements in the Baltic Sea reported in the MEMENTO database. Our results suggest that the eddy covariance technique is a useful tool for studying CH4 fluxes and improving the understanding of air-sea gas exchange processes with high-temporal resolution. Potentially, the high resolution of micrometeorological data can increase the understanding of the temporal variability and forcing processes of CH4 flux.

  • 5.
    Hock, Regine
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Huss, Matthias
    ETH Zurich.
    A new model for global glacier change and sea-level rise2015In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 3, p. 1-22, article id 54Article in journal (Refereed)
    Abstract [en]

    The anticipated retreat of glaciers around the globe will pose far-reaching challenges to the management of fresh water resources and significantly contribute to sea-level rise within the coming decades. Here, we present a new model for calculating the twenty-first century mass changes of all glaciers on Earth outside the ice sheets. The Global Glacier Evolution Model (GloGEM) includes mass loss due to frontal ablation at marine-terminating glacier fronts and accounts for glacier advance/retreat and surface elevation changes. Simulations are driven with monthly near-surface air temperature and precipitation from 14 Global Circulation Models forced by RCP2.6, RCP4.5, and RCP8.5 emission scenarios. Depending on the scenario, the model yields a global glacier volume loss of 25–48% between 2010 and 2100. For calculating glacier contribution to sea-level rise, we account for ice located below sea-level presently displacing ocean water. This effect reduces the glacier contribution by 11–14%, so that our model predicts a sea-level equivalent (multi-model mean ±1 standard deviation) of 79±24 mm (RCP2.6), 108±28 mm (RCP4.5), and 157±31 mm (RCP8.5). Mass losses by frontal ablation account for 10% of total ablation globally, and up to ∼30% regionally. Regional equilibrium line altitudes are projected to rise by ∼100–800 m until 2100, but the effect on ice wastage depends on initial glacier hypsometries.

  • 6.
    Hock, Regine
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Hutchings, Jennifer K.
    Oregon State Univ, Coll Earth Ocean & Atmospher Sci, Corvallis, OR 97331 USA..
    Lehning, Michael
    Inst Snow & Avalanche Res, Davos, Switzerland..
    Grand Challenges in Cryospheric Sciences: Toward Better Predictability of Glaciers, Snow and Sea Ice2017In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 5, article id 64Article in journal (Refereed)
  • 7.
    Kayler, Zachary E.
    et al.
    Univ Idaho, Dept Soil & Water Syst, Moscow, ID 83843 USA.
    Premke, Katrin
    Lebniz Inst Freshwater Ecol & Inland Fisheries, Dept Chem Analyt & Biogeochem, Berlin, Germany.
    Gessler, Arthur
    Swiss Fed Inst Forest Snow & Landscape Res WSL, Birmensdorf, Switzerland.
    Gessner, Mark
    TU Berlin, Dept Ecol, Berlin Inst Technol, Berlin, Germany;Leibniz Inst Freshwater Ecol & Inland Fisheries, Dept Expt Limnol, Stechlin, Germany.
    Gribler, Christian
    Univ Vienna, Ctr Funct Ecol, Dept Limnol & Biooceanog, Vienna, Austria.
    Hilt, Sabine
    Leibniz Inst Freshwater Ecol & Inland Fisheries, Dept Ecosyst Res, Berlin, Germany.
    Klemedtsson, Leif
    Gothenburg Univ, Dept Earth Sci, Gothenburg, Sweden.
    Kuzyakov, Yakov
    Georg August Univ Gottingen, Dept Soil Sci Temperate Ecosyst, Gottingen, Germany.
    Reichstein, Markus
    Max Planck Inst Biogeochem, Dept Biogeochem Integrat, Jena, Germany.
    Siemens, Jan
    Justus Liebig Univ Giessen, Inst Soil Sci & Soil Conservat, IFZ Res Ctr Biosyst Land Use & Nutr, Giessen, Germany.
    Totsche, Kai-Uwe
    riedrich Schiller Univ Jena, Inst Geosci, Jena, Germany.
    Tranvik, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Wagner, Annekatrin
    Tech Univ Dresden, Inst Hydrobiol, Dresden, Germany.
    Weitere, Markus
    UFZ Helmholtz Ctr Environm Res, Dept River Ecol, Magdeburg, Germany.
    Grossart, Hans-Peter
    Leibniz Inst Freshwater Ecol & Inland Fisheries, Dept Expt Limnol, Stechlin, Germany;Univ Potsdam, Inst Biochem & Biol, Potsdam, Germany.
    Integrating aquatic and terrestrial perspectives to improve insights into organic matter cycling at the landscape scale2019In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 7, article id 127Article in journal (Refereed)
    Abstract [en]

    Across a landscape, aquatic-terrestrial interfaces within and between ecosystems are hotspots of organic matter (OM) mineralization. These interfaces are characterized by sharp spatio-temporal changes in environmental conditions, which affect OM properties and thus control OM mineralization and other transformation processes. Consequently, the extent of OM movement at and across aquatic-terrestrial interfaces is crucial in determining OM turnover and carbon (C) cycling at the landscape scale. Here, we propose expanding current concepts in aquatic and terrestrial ecosystem sciences to comprehensively evaluate OM turnover at the landscape scale. We focus on three main concepts toward explaining OM turnover at the landscape scale: the landscape spatio-temporal context, OM turnover described by priming and ecological stoichiometry, and anthropogenic effects as a disruptor of natural OM transfer magnitudes and pathways. A conceptual framework is introduced that allows for discussing the disparities in spatial and temporal scales of OM transfer, changes in environmental conditions, ecosystem connectivity, and microbial–substrate interactions. The potential relevance of priming effects in both terrestrial and aquatic systems is addressed. For terrestrial systems, we hypothesize that the interplay between the influx of OM and its corresponding elemental composition and the elemental demand of the microbial communities – stoichiometric question – may alleviate spatial and metabolic thresholds. In comparison, substrate level OM dynamics may be substantially different in aquatic systems due to matrix effects that accentuate the role of abiotic conditions, substrate quality, and microbial community dynamics. We highlight the disproportionate impact anthropogenic activities can have on OM cycling across the landscape including reversing natural OM flows through the landscape, disrupting ecosystem connectivity, and nutrient additions that cascade across the landscape. This knowledge is crucial for a better understanding of OM cycling in a landscape context, in particular since terrestrial and aquatic compartments may respond differently to the ongoing changes in climate, land use, and other anthropogenic interferences.

  • 8.
    Kienholz, Christian
    et al.
    Univ Alaska Fairbanks, Inst Geophys, Fairbanks, AK 99775 USA.;Univ Alaska Southeast, Nat Sci Res Lab, Juneau, AK 99801 USA..
    Hock, Regine
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Truffer, Martin
    Univ Alaska Fairbanks, Inst Geophys, Fairbanks, AK 99775 USA..
    Bieniek, Peter
    Univ Alaska Fairbanks, Inst Geophys, Fairbanks, AK 99775 USA.;Univ Alaska Fairbanks, Int Arctic Res Ctr, Fairbanks, AK USA..
    Lader, Richard
    Univ Alaska Fairbanks, Inst Geophys, Fairbanks, AK 99775 USA.;Univ Alaska Fairbanks, Int Arctic Res Ctr, Fairbanks, AK USA..
    Mass Balance Evolution of Black Rapids Glacier, Alaska, 1980-2100, and Its Implications for Surge Recurrence2017In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 5, article id 56Article in journal (Refereed)
    Abstract [en]

    Surge-type Black Rapids Glacier, Alaska, has undergone strong retreat since it last surged in 1936-1937. To assess its evolution during the late Twentieth and Twenty-first centuries and determine potential implications for surge likelihood, we run a simplified glacier model over the periods 1980-2015 (hindcasting) and 2015-2100 (forecasting). The model is forced by daily temperature and precipitation fields, with downscaled reanalysis data used for the hindcasting. A constant climate scenario and an RCP 8.5 scenario based on the GFDL-CM3 climate model are employed for the forecasting. Debris evolution is accounted for by a debris layer time series derived from satellite imagery (hindcasting) and a parametrized debris evolution model (forecasting). A retreat model accounts for the evolution of the glacier geometry. Model calibration, validation and parametrization rely on an extensive set of in situ and remotely sensed observations. To explore uncertainties in our projections, we run the glacier model in a Monte Carlo fashion, varying key model parameters and input data within plausible ranges. Our results for the hindcasting period indicate a negative mass balance trend, caused by atmospheric warming in the summer, precipitation decrease in the winter and surface elevation lowering (climate-elevation feedback), which exceed the moderating effects from increasing debris cover and glacier retreat. Without the 2002 rockslide deposits on Black Rapids' lower reaches, the mass balances would be more negative, by similar to 20% between the 2003 and 2015 mass-balance years. Despite its retreat, Black Rapids Glacier is substantially out of balance with the current climate. By 2100, similar to 8% of Black Rapids' 1980 area are projected to vanish under the constant climate scenario and similar to 73% under the RCP 8.5 scenario. For both scenarios, the remaining glacier portions are out of balance, suggesting continued retreat after 2100. Due to mass starvation, a surge in the Twenty-first century is unlikely. The projected retreat will affect the glacier's runoff and change the landscape in the Black Rapids area markedly.

  • 9.
    Marchenko, Sergey
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Department of Geophysics, The University Centre in Svalbard, Longyearbyen, Norway.
    Van Pelt, Ward
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Carlsson, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Pohjola, Veijo
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Pettersson, Rickard
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Machguth, Horst
    Reijmer, Carleen
    Parameterizing deep water percolation improves subsurface temperature simulations by a multilayer firn model2017In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 5, no 16Article in journal (Refereed)
    Abstract [en]

    Deep preferential percolation of melt water in snow and firn brings water lower along the vertical profile than a laterally homogeneous wetting front. This widely recognized process is an important source of uncertainty in simulations of subsurface temperature, density, and water content in seasonal snow and in firn packs on glaciers and ice sheets. However, observation and quantification of preferential flow is challenging and therefore it is not accounted for by most of the contemporary snow/firn models. Here we use temperature measurements in the accumulation zone of Lomonosovfonna, Svalbard, done in April 2012-2015 using multiple thermistor strings to describe the process of water percolation in snow and firn. Effects of water flow through the snow and firn profile are further explored using a coupled surface energy balance - firn model forced by the output of the regional climate model WRF. In situ air temperature, radiation, and surface height change measurements are used to constrain the surface energy and mass fluxes. To account for the effects of preferential water flow in snow and firn we test a set of depth-dependent functions allocating a certain fraction of the melt water available at the surface to each snow/firn layer. Experiments are performed for a range of characteristic percolation depths and results indicate a reduction in root mean square difference between the modeled and measured temperature by up to a factor of two compared to the results from the default water infiltration scheme. This illustrates the significance of accounting for preferential water percolation to simulate subsurface conditions. The suggested approach to parameterization of the preferential water flow requires low additional computational cost and can be implemented in layered snow/ firn models applied both at local and regional scales, for distributed domains with multiple mesh points.

  • 10.
    Mattsson, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Burchardt, Steffi
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Center for Natural Hazards and Disaster Science, Uppsala University, Uppsala, Sweden.
    Almqvist, Bjarne S. G.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Ronchin, Erika
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Center for Natural Hazards and Disaster Science, Uppsala University, Uppsala, Sweden.
    Syn-Emplacement Fracturing in the Sandfell Laccolith, Eastern Iceland: Implications for Rhyolite Intrusion Growth and Volcanic Hazards2018In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 6, article id 5Article in journal (Refereed)
    Abstract [en]

    Felsic magma commonly pools within shallow mushroom-shaped magmatic intrusions, so-called laccoliths or cryptodomes, which can cause both explosive eruptions and collapse of the volcanic edifice. Deformation during laccolith emplacement is primarily considered to occur in the host rock. However, shallowly emplaced laccoliths (cryptodomes) show extensive internal deformation. While deformation of magma in volcanic conduits is an important process for regulating eruptive behavior, the effects of magma deformation on intrusion emplacement remain largely unexplored. In this study, we investigate the emplacement of the 0.57 km3 rhyolitic Sandfell laccolith, Iceland, which formed at a depth of 500 m in a single intrusive event. By combining field measurements, 3D modeling, anisotropy of magnetic susceptibility (AMS), microstructural analysis, and FEM modeling we examine deformation in the magma to constrain its influence on intrusion emplacement. Concentric flow bands and S-C fabrics reveal contact-parallel magma flow during the initial stages of laccolith inflation. The magma flow fabric is overprinted by strain-localization bands (SLBs) and more than one third of the volume of the Sandfell laccolith displays concentric intensely fractured layers. A dominantly oblate magmatic fabric in the fractured areas and conjugate geometry of SLBs, and fractures in the fracture layers demonstrate that the magma was deformed by intrusive stresses. This implies that a large volume of magma became viscously stalled and was unable to flow during intrusion. Fine-grained groundmass and vesicle-poor rock adjacent to the fracture layers point to that the interaction between the SLBs and the flow bands at sub-solidus state caused the brittle-failure and triggered decompression degassing and crystallization, which led to rapid viscosity increase in the magma. The extent of syn-emplacement fracturing in the Sandfell laccolith further shows that strain-induced degassing limited the amount of eruptible magma by essentially solidifying the rim of the magma body. Our observations indicate that syn-emplacement changes in rheology, and the associated fracturing of intruding magma not only occur in volcanic conduits, but also play a major role in the emplacement of viscous magma intrusions in the upper kilometer of the crust.

  • 11.
    Mostovaya, Alina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Hawkes, Jeffrey A.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Dittmar, Thorsten
    Carl von Ossietzky Univ Oldenburg, Inst Chem & Biol Marine Environm, Res Grp Marine Geochem MPI Bridging Grp, Oldenburg, Germany.
    Tranvik, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Molecular determinants of dissolved organic matter reactivity in lake water2017In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 5, article id 106Article in journal (Refereed)
    Abstract [en]

    Lakes in the boreal region have been recognized as the biogeochemical hotspots, yet many questions regarding the regulators of organic matter processing in these systems remain open. Molecular composition can be an important determinant of dissolved organic matter (DOM) fate in freshwater systems, but many aspects of this relationship remain unclear due to the complexity of DOM and its interactions in the natural environment. Here, we combine ultrahigh resolution mass spectrometry (FT-ICR-MS) with kinetic modeling of decay of \textgreater1,300 individual DOM molecular formulae identified by mass spectrometry, to evaluate the role of specific molecular characteristics in decomposition of lake water DOM. Our data is derived from a 4 months microbial decomposition experiment, carried out on water from three Swedish lakes, with the set-up including natural lake water, as well as the lake water pretreated with UV light. The relative decay rate of every molecular formula was estimated by fitting a single exponential model to the change in FT-ICR-MS signal intensities over decomposition time.We found a continuous range of exponential decay coefficients (kexp)within different groups of compounds and show that for highly unsaturated and phenolic compounds the distribution of kexp was shifted toward the lowest values. Contrary to this general trend, plant-derived polyphenols and polycondensed aromatics were on average more reactive than compounds with an intermediate aromaticity. The decay rate of aromatic compounds increased with increasing nominal oxidation state of carbon, and molecular mass in some cases showed an inverse relationship with kexp in the UV-manipulated treatment. Further, we observe an increase in formulae-specific kexp as a result of the UV pretreatment. General trends in reactivity identified among major compound groups emphasize the importance of the intrinsic controllers of lake water DOMdecay. However, we additionally indicate that each compound group contained a wide spectrum of reactivities, suggesting that high resolution is needed to further ascertain the complex reasons behind DOM reactivity in lake water.

  • 12.
    O'Regan, Matt
    et al.
    Stockholm Univ, Dept Geol Sci, Stockholm, Sweden;Stockholm Univ, Bolin Ctr Cilmate Res, Stockholm, Sweden.
    Coxall, Helen K.
    Stockholm Univ, Dept Geol Sci, Stockholm, Sweden;Stockholm Univ, Bolin Ctr Cilmate Res, Stockholm, Sweden.
    Cronin, Thomas M.
    US Geol Survey, Florence Bascom Geosci Ctr, 959 Natl Ctr, Reston, VA 22092 USA.
    Gyllencreutz, Richard
    Stockholm Univ, Dept Geol Sci, Stockholm, Sweden;Stockholm Univ, Bolin Ctr Cilmate Res, Stockholm, Sweden.
    Jakobsson, Martin
    Stockholm Univ, Dept Geol Sci, Stockholm, Sweden;Stockholm Univ, Bolin Ctr Cilmate Res, Stockholm, Sweden.
    Kaboth, Stefanie
    Heidelberg Univ, Inst Earth Sci, Heidelberg, Germany;Natl Taiwan Univ, Dept Geosci, Taipei, Taiwan.
    Lowemark, Ludvig
    Natl Taiwan Univ, Dept Geosci, Taipei, Taiwan.
    Wiers, Steffen
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Natural Resources and Sustainable Development.
    West, Gabriel
    Stockholm Univ, Dept Geol Sci, Stockholm, Sweden;Stockholm Univ, Bolin Ctr Cilmate Res, Stockholm, Sweden.
    Stratigraphic Occurrences of Sub-Polar Planktic Foraminifera in Pleistocene Sediments on the Lomonosov Ridge, Arctic Ocean2019In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 7, article id 71Article in journal (Refereed)
    Abstract [en]

    Turborotalita quinqueloba is a species of planktic foraminifera commonly found in the sub-polar North Atlantic along the pathway of Atlantic waters in the Nordic seas and sometimes even in the Arctic Ocean, although its occurrence there remains poorly understood. Existing data show that T. quinqueloba is scarce in Holocene sediments from the central Arctic but abundance levels increase in sediments from the last interglacial period [Marine isotope stage (MIS) 5, 71-120 ka] in cores off the northern coast of Greenland and the southern Mendeleev Ridge. Turborotalita also occurs in earlier Pleistocene interglacials in these regions, with a unique and widespread occurrence of the less known Turborotalita egelida morphotype, proposed as a biostratigraphic marker for MIS 11 (474-374 ka). Here we present results from six new sediment cores, extending from the central to western Lomonosov Ridge, that show a consistent Pleistocene stratigraphy over 575 km. Preliminary semi-quantitative assessments of planktic foraminifer abundance and assemblage composition in two of these records (LOMROG12-7PC and AO16-5PC) reveal two distinct stratigraphic horizons containing Turborotalita in MIS 5. Earlier occurrences in Pleistocene interglacials are recognized, but contain significantly fewer specimens and do not appear to be stratigraphically coeval in the studied sequences. In all instances, the Turborotalita specimens resemble the typical T. quinqueloba morphotype but are smaller (63-125 mu m), smooth-walled and lack the final thickened calcite layer common to adults of the species. These results extend the geographical range for T. quinqueloba in MIS 5 sediments of the Arctic Ocean and provide compelling evidence for recurrent invasions during Pleistocene interglacials.

  • 13.
    Rhodes, Emma
    et al.
    University of Canterbury, Christchurch, New Zealand.
    Kennedy, Ben M.
    University of Canterbury, Christchurch, New Zealand.
    Lavallée, Yan
    Department of Earth, Ocean and Ecological Sciences, University of Liverpool, Liverpool, United Kingdom.
    Hornby, Adrian
    Department of Earth, Ocean and Ecological Sciences, University of Liverpool, Liverpool, United Kingdom.;Earth and Environmental Sciences, Ludwig-Maximilian University of Munich, Munich, Germany.
    Edwards, Matt
    University of Canterbury, Christchurch, New Zealand.
    Chigna, Gustavo
    Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hydrologia, Guatemala City, Guatemala.
    Textural Insights Into the Evolving Lava Dome Cycles at Santiaguito Lava Dome, Guatemala2018In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 6, article id 30Article in journal (Refereed)
    Abstract [en]

    The structures and textures preserved in lava domes reflect underlying magmatic and eruptive processes, and may provide evidence of how eruptions initiate and evolve. This study explores the remarkable cycles in lava extrusion style produced between 1922 and 2012 at the Santiaguito lava dome complex, Guatemala. By combining an examination of eruptive lava morphologies and textures with a review of historical records, we aim to constrain the processes responsible for the range of erupted lava type and morphologies. The Santiaguito lava dome complex is divided into four domes (El Caliente, La Mitad, El Monje, El Brujo), containing a range of proximal structures (e.g., spines) from which a series of structurally contrasting lava flows originate. Vesicular lava flows (with a'a like, yet non-brecciated flow top) have the highest porosity with interconnected spheroidal pores and may transition into blocky lava flows. Blocky lava flows are high volume and texturally variable with dense zones of small tubular aligned pore networks and more porous zones of spheroidal shaped pores. Spines are dense and low volume and contain small skeletal shaped pores, and subvertical zones of sigmoidal pores. We attribute the observed differences in pore shapes to reflect shallow inflation, deflation, flattening, or shearing of the pore fraction. Effusion rate and duration of the eruption define the amount of time available for heating or cooling, degassing and outgassing prior to and during extrusion, driving changes in pore textures and lava type. Our new textural data when reviewed with all the other published data allow a cyclic model to be developed. The cyclic eruption models are influenced by viscosity changes resulting from (1) initial magmatic composition and temperature, and (2) effusion rate which in turn affects degassing, outgassing and cooling time in the conduit. Each lava type presents a unique set of hazards and understanding the morphologies and dome progression is useful in hazard forecasting.

  • 14.
    Roth, Aurora
    et al.
    Univ Alaska, Geophys Inst, Fairbanks, AK 99701 USA.
    Hock, Regine
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Univ Alaska, Geophys Inst, Fairbanks, AK 99701 USA.
    Schuler, Thomas V.
    Univ Oslo, Dept Geosci, Oslo, Norway;Univ Ctr Svalbard UNIS, Dept Arctic Geophys, Longyearbyen, Norway.
    Bieniek, Peter A.
    Univ Alaska, Int Arctic Res Ctr, Fairbanks, AK 99701 USA.
    Pelto, Mauri
    Nichols Coll, Dept Environm Sci, Dudley, MA USA.
    Aschwanden, Andy
    Univ Alaska, Geophys Inst, Fairbanks, AK 99701 USA.
    Modeling Winter Precipitation Over the Juneau Icefield, Alaska, Using a Linear Model of Orographic Precipitation2018In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 6, article id 20Article in journal (Refereed)
    Abstract [en]

    Assessing and modeling precipitation in mountainous areas remains a major challenge in glacier mass balance modeling. Observations are typically scarce and reanalysis data and similar climate products are too coarse to accurately capture orographic effects. Here we use the linear theory of orographic precipitation model (LT model) to downscale winter precipitation from the Weather Research and Forecasting Model (WRF) over the Juneau Icefield, one of the largest ice masses in North America (>4,000 km(2)), for the period 1979-2013. The LT model is physically-based yet computationally efficient, combining airflow dynamics and simple cloudmicrophysics. The resulting 1 kmresolution precipitation fields show substantially reduced precipitation on the northeastern portion of the icefield compared to the southwestern side, a pattern that is not well captured in the coarse resolution (20 km) WRF data. Net snow accumulation derived from the LT model precipitation agrees well with point observations across the icefield. To investigate the robustness of the LT model results, we perform a series of sensitivity experiments varying hydrometeor fall speeds, the horizontal resolution of the underlying grid, and the source of the meteorological forcing data. The resulting normalized spatial precipitation pattern is similar for all sensitivity experiments, but local precipitation amounts vary strongly, with greatest sensitivity to variations in snow fall speed. Results indicate that the LT model has great potential to provide improved spatial patterns of winter precipitation for glaciermass balance modeling purposes in complex terrain, but ground observations are necessary to constrain model parameters to match total amounts.

  • 15.
    van Pelt, Ward J. J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Pohjola, Veijo
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Reijmer, Carleen
    The changing impact of snow conditions and refreezing on the mass balance of an idealized Svalbard glacier2016In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 4, no 102Article in journal (Refereed)
1 - 15 of 15
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