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  • Springer  (1,709,192)
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  • 1
    Publication Date: 2019-03-28
    Description: Beside its global effects, climate change is manifested in many regionally pronounced features mainly resulting from changes in the oceanic and atmospheric circulation. Here we investigate the influence of the North Atlantic SST on shaping the winter-time response to global warming. Our results are based on a long-term climate projection with the Max Planck Institute Earth System Model (MPI-ESM) to investigate the influence of North Atlantic sea surface temperature pattern changes on shaping the atmospheric climate change signal. In sensitivity experiments with the model’s atmospheric component we decompose the response into components controlled by the local SST structure and components controlled by global/remote changes. MPI-ESM simulates a global warming response in SST similar to other climate models: there is a warming minimum—or ”warming hole”—in the subpolar North Atlantic, and the sharp SST gradients associated with the Gulf Stream and the North Atlantic Current shift northward by a few a degrees. Over the warming hole, global warming causes a relatively weak increase in rainfall. Beyond this, our experiments show more localized effects, likely resulting from future SST gradient changes in the North Atlantic. This includes a significant precipitation decrease to the south of the Gulf Stream despite increased underlying SSTs. Since this region is characterised by a strong band of precipitation in the current climate, this is contrary to the usual case that wet regions become wetter and dry regions become drier in a warmer climate. A moisture budget analysis identifies a complex interplay of various processes in the region of modified SST gradients: reduced surface winds cause a decrease in evaporation; and thermodynamic, modified atmospheric eddy transports, and coastal processes cause a change in the moisture convergence. The changes in the the North Atlantic storm track are mainly controlled by the non-regional changes in the forcing. The impact of the local SST pattern changes on regions outside the North Atlantic is small in our setup.
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  • 2
    Publication Date: 2019-03-20
    Description: A long-standing difficulty of climate models is to capture the annual cycle (AC) of eastern equatorial Pacific (EEP) sea surface temperature (SST). In this study, we first examine the EEP SST AC in a set of integrations of the coupled Kiel Climate Model, in which only atmosphere model resolution differs. When employing coarse horizontal and vertical atmospheric resolution, significant biases in the EEP SST AC are observed. These are reflected in an erroneous timing of the cold tongue’s onset and termination as well as in an underestimation of the boreal spring warming amplitude. A large portion of these biases are linked to a wrong simulation of zonal surface winds, which can be traced back to precipitation biases on both sides of the equator and an erroneous low-level atmospheric circulation over land. Part of the SST biases also is related to shortwave radiation biases related to cloud cover biases. Both wind and cloud cover biases are inherent to the atmospheric component, as shown by companion uncoupled atmosphere model integrations forced by observed SSTs. Enhancing atmosphere model resolution, horizontal and vertical, markedly reduces zonal wind and cloud cover biases in coupled as well as uncoupled mode and generally improves simulation of the EEP SST AC. Enhanced atmospheric resolution reduces convection biases and improves simulation of surface winds over land. Analysis of a subset of models from the Coupled Model Intercomparison Project phase 5 (CMIP5) reveals that in these models, very similar mechanisms are at work in driving EEP SST AC biases.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 3
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    In:  Climate Dynamics, 52 (5-6). pp. 3223-3239.
    Publication Date: 2019-03-20
    Description: The Earth will exhibit continued global surface warming in response to a sustained increase of atmospheric carbon dioxide (CO2) levels. Massive meltwater input from the Antarctic ice sheet into the Southern Ocean could be one consequence of this warming. Here we investigate the impacts which this meltwater input may have on Earth’s surface climate and ocean circulation in a warming world. To this end a set of ensemble experiments has been conducted with a global climate model forced by increasing atmospheric CO2-concentration and an idealized Antarctic meltwater input to the Southern Ocean with varying amplitude and spatial pattern. As long as the atmospheric CO2-concentration stays moderate, i.e. below approximately twice the preindustrial concentration, and if a strong meltwater forcing of either 0.05 or 0.1 Sv is applied, enhanced Antarctic sea–ice cover and surface air temperature cooling over most parts of the Southern Ocean is observed. When the atmospheric CO2-concentration becomes larger than twice the preindustrial concentration, the meltwater only plays a minor role. The Antarctic meltwater drives significant slowing of the Southern Ocean meridional overturning circulation (MOC). Again, the meltwater influence only is detectable as long as the CO2-forcing is moderate. Much larger MOC changes develop in response to highly elevated atmospheric CO2-levels independent of whether or not a meltwater forcing is applied. The response of the Antarctic circumpolar current (ACC) is nonlinear. Substantial and persistent ACC slowing is simulated when solely the meltwater forcing of 0.1 Sv is applied, which is due to the halt of Weddell Sea deep convection and subsequent collapse of the Southern Ocean MOC. When the increasing atmospheric CO2-concentration additionally drives the model the ACC partly recovers in the long run. The partial recovery is due to strengthening westerly wind stress over the Southern Ocean, which intensifies the Ekman Cell. This study suggests that Southern Hemisphere climate projections for the twenty-first century could benefit from incorporating interactive Antarctic ice sheet.
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  • 4
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    In:  In: Oceanographic and Biological Aspects of the Red Sea. , ed. by Rasul, N. M. A. and Stewart, I. C. F. Springer, Cham, Switzerland, pp. 401-418. ISBN 978-3-319-99416-1
    Publication Date: 2018-12-14
    Description: Coral reefs in the Red Sea belong to the most diverse and productive reef ecosystems worldwide, although they are exposed to strong seasonal variability, high temperature, and high salinity. These factors are considered stressful for coral reef biota and challenge reef growth in other oceans, but coral reefs in the Red Sea thrive despite these challenges. In the central Red Sea high temperatures, high salinities, and low dissolved oxygen on the one hand reflect conditions that are predicted for ‘future oceans’ under global warming. On the other hand, alkalinity and other carbonate chemistry parameters are considered favourable for coral growth. In coral reefs of the central Red Sea, temperature and salinity follow a seasonal cycle, while chlorophyll and inorganic nutrients mostly vary spatially, and dissolved oxygen and pH fluctuate on the scale of hours to days. Within these strong environmental gradients micro- and macroscopic reef communities are dynamic and demonstrate plasticity and acclimatisation potential. Epilithic biofilm communities of bacteria and algae, crucial for the recruitment of reef-builders, undergo seasonal community shifts that are mainly driven by changes in temperature, salinity, and dissolved oxygen. These variables are predicted to change with the progression of global environmental change and suggest an immediate effect of climate change on the microbial community composition of biofilms. Corals are so-called holobionts and associate with a variety of microbial organisms that fulfill important functions in coral health and productivity. For instance, coral-associated bacterial communities are more specific and less diverse than those of marine biofilms, and in many coral species in the central Red Sea they are dominated by bacteria from the genus Endozoicomonas. Generally, coral microbiomes align with ecological differences between reef sites. They are similar at sites where these corals are abundant and successful. Coral microbiomes reveal a measurable footprint of anthropogenic influence at polluted sites. Coral-associated communities of endosymbiotic dinoflagellates in central Red Sea corals are dominated by Symbiodinium from clade C. Some corals harbour the same specific symbiont with a high physiological plasticity throughout their distribution range, while others maintain a more flexible association with varying symbionts of high physiological specificity over depths, seasons, or reef locations. The coral-Symbiodinium endosymbiosis drives calcification of the coral skeleton, which is a key process that provides maintenance and formation of the reef framework. Calcification rates and reef growth are not higher than in other coral reef regions, despite the beneficial carbonate chemistry in the central Red Sea. This may be related to the comparatively high temperatures, as indicated by reduced summer calcification and long-term slowing of growth rates that correlate with ocean warming trends. Indeed, thermal limits of abundant coral species in the central Red Sea may have been exceeded, as evidenced by repeated mass bleaching events during previous years. Recent comprehensive baseline data from central Red Sea reefs allow for insight into coral reef functioning and for quantification of the impacts of environmental change in the region.
    Type: Book chapter , NonPeerReviewed
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  • 5
    Publication Date: 2019-02-22
    Description: Dosidicus gigas (the Humboldt squid) is a widely distributed and ecologically important predator in the eastern Pacific Ocean, but its mating behaviour is poorly understood. Individuals of this species have undergone a drastic change in size at maturity in the last years. We investigated mating activity of Humboldt squid in the Gulf of California in 2013, 2014, and 2015 by quantifying spermatangia deposited in the tissue of the buccal area. In 2015, we encountered the smallest mean mantle length of mature specimens recorded to date in the Gulf of California. In all years, numerous males were encountered that had been mated by other males. Spermatangia in males were deposited on the tissue in similar numbers and in the same location as normally occurs in females (the buccal area), suggesting that male-to-male mating behaviour is similar to male-to-female. This behaviour is referred to as same-sex sexual behaviour and has been described for various taxa, including other cephalopods. Overall similarity in mating frequency between males and females and in body size of mated individuals (in 2015) suggests non-discriminative and brief encounters with body size being a cue for mating. This mating strategy may be beneficial for males, as Humboldt squid live in groups where competition for mates is likely high. The energetic costs of male-to-male mating events may be counterbalanced by the fitness profits of indiscriminate mating behaviour.
    Type: Article , PeerReviewed
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  • 6
    Publication Date: 2019-04-01
    Description: As coastal areas become increasingly vulnerable to climate change, the study of nearshore sediment textures along the littoral cell of the Medjerda delta in the Gulf of Tunis, southern Mediterranean coast can provide valuable information (i) on the origin (continental or marine) of the sediment, (ii) its transport direction, and (iii) constitutes an important tool in the assessment of coastal sensitivity. A total of 120 sediments samples underwent grain size analysis and statistic parameters have been calculated. These allowed the identification of five different Sedimentary Types (ST). Accordingly, using grain size indexes (i.e. Mz, SKI and Ku), Sediment Trend Analysis (STA) modeling tools were applied to define the seasonal sediment transport pathways throughout the nearshore of the Medjerda sedimentary cell. Results show that grain size distribution (GSD) and STA model pathways are determined by cross-shore geomorphology, location of the sediment-cell, seasonal incident wave and local terrestrial supply. The appearance in an atypical seabed location of the finer (Mo = 0.1 mm) and the coarser STs (Mo = 0.8 mm) can be indicative of human influence since the coarser particles are usually retained by dam structures. Moreover, the bimodality and the increased distribution of mud are also related to the seasonal incident wave winnowing of the historic deltaic plain submerged by the relative rise in sea level. The evolution of the sediment pattern towards a greater proportion of very fine grains indicates a deficit of sediment supply, particularly of the coarser grains, and demonstrates the coastal vulnerability of the Gulf of Tunis due to anthropic effects.
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  • 7
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    In:  Marine Biodiversity, 49 (2). pp. 1043-1046.
    Publication Date: 2019-04-26
    Description: An interactive (multi-access) global identification key (OncIdent) has been developed for the pelagic marine microcopepod family Oncaeidae and made accessible online. Details of the general approach and development of the key are given in Bottger-Schnack and Schnack (J Nat Hist 49:2727-2741, 2015). After beta-testing, new additions include illustrations for all species and feature attributes considered, plus a textual summary of each species' feature states in the key. Additional taxonomic notes are given where required, highlighting morphological or molecular genetic peculiarities or problems, with links to large data bases leading directly to more comprehensive information about each species. The present paper briefly reviews the taxonomic background for key construction, summarizes the opportunities and limitations of the current online version OncIdent2.0, and provides guidance for its practical use.
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  • 8
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    In:  In: Remote Sensing of the Asian Seas. , ed. by Barale, V. and Gade, M. Springer, Cham, pp. 123-138. ISBN 978-3-319-94065-6
    Publication Date: 2019-04-08
    Description: The Laptev and Eastern Siberian shelves are the world’s broadest shallow shelf systems. Large Siberian rivers and coastal erosion of up to meters per summer deliver large volumes of terrestrial matter into the Arctic shelf seas. In this chapter we investigate the applicability of Ocean Colour Remote Sensing during the ice-free summer season in the Siberian Laptev Sea region. We show that the early summer river peak discharge may be traced using remote sensing in years characterized by early sea-ice retreat. In the summer time after the peak discharge, the spreading of the main Lena River plume east and north-east of the Lena River Delta into the shelf system becomes hardly traceable using optical remote sensing methods. Measurements of suspended particulate matter (SPM) and coloured dissolved organic matter (cDOM) are of the same magnitude in the coastal waters of Buor Khaya Bay as in the Lena River. Match-up analyses of in situ chlorophyll-a (Chl-a) show that standard Medium Resolution Imaging Spectrometer (MERIS) and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite-derived Chl-a is not a valid remote sensing product for the coastal waters and the inner shelf region of the Laptev Sea. All MERIS and MODIS-derived Chl-a products are overestimated by at least a factor of ten, probably due to absorption by the extraordinarily high amount of non-algal particles and cDOM in these coastal and inner-shelf waters. Instead, Ocean Colour remote sensing provides information on wide-spread resuspension over shallows and lateral advection visible in satellite-derived turbidity. Satellite Sea Surface Temperature (SST) data clearly show hydrodynamics and delineate the outflow of the Lena River for hundreds of kilometres out into the shelf seas.
    Type: Book chapter , NonPeerReviewed
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  • 9
    Publication Date: 2019-04-10
    Description: Our knowledge on distribution, habitats and behavior of Southern Ocean fishes living at water depths beyond scuba-diving limits is still sparse, as it is difficult to obtain quantitative data on these aspects of their biology. Here, we report the results of an analysis of seabed images to investigate species composition, behavior, spatial distribution and preferred habitats of demersal fish assemblages in the southern Weddell Sea. Our study was based on a total of 2736 high-resolution images, covering a total seabed area of 11,317 m2, which were taken at 13 stations at water depths between 200 and 750 m. Fish were found in 380 images. A total of 379 notothenioid specimens were recorded, representing four families (Nototheniidae, Artedidraconidae, Bathydraconidae, Channichthyidae), 17 genera and 25 species. Nototheniidae was the most speciose fam- ily, including benthic species (Trematomus spp.) and the pelagic species Pleuragramma antarctica, which was occasionally recorded in dense shoals. Bathydraconids ranked second with six species, followed by artedidraconids and channichthyids, both with five species. Most abundant species were Trematomus scotti and T. lepidorhinus among nototheniids, and Dol- loidraco longedorsalis and Pagetopsis maculatus among artedidraconids and channichthyids, respectively. Both T. lepi- dorhinus and P. maculatus preferred seabed habitats characterized by biogenous debris and rich epibenthic fauna, whereas T. scotti and D. longedorsalis were frequently seen resting on fine sediments and scattered gravel. Several fish species were recorded to make use of the three-dimensional structure formed by epibenthic foundation species, like sponges, for perching or hiding inside. Nesting behavior was observed, frequently in association with dropstones, in species from various families, including Channichthyidae (Chaenodraco wilsoni and Pagetopsis macropterus) and Bathydraconidae (Cygnodraco mawsoni).
    Repository Name: EPIC Alfred Wegener Institut
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  • 10
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    In:  In: Oceanographic and Biological Aspects of the Red Sea. , ed. by Rasul, N. M. A. and Stewart, I. C. F. Springer Oceanography Series . Springer, Cham, pp. 185-194.
    Publication Date: 2018-12-11
    Description: The deep-sea brines of the Red Sea are unusual extreme environments and form characteristically steep gradients across the brine-seawater interfaces. Due to their unusual nature and unique combination of physical-chemical conditions these interfaces provide an interesting source of new findings in the fields of geochemistry, geology, microbiology, biotechnology, virology, and general biology. The current chapter summarizes recent and new results in the study of geochemistry and life at the interfaces of brine-filled deeps of the Red Sea.
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  • 11
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    In:  International Journal of Earth Sciences, 108 . pp. 587-620.
    Publication Date: 2019-04-03
    Description: The nature of the warm climates of the Cretaceous has been enigmatic since the first numerical climate models were run in the late 1970s. Quantitative simulations of the paleoclimate have consistently failed to agree with information from plant and animal fossils and climate sensitive sediments. The ‘cold continental interior paradox’ (first described by DeConto et al. in Barrera E, Johnson C (eds) Evolution of the Cretaceous Ocean/climate system, vol 332. Geological Society of America Special Paper, Boulder, pp 391–406, 1999), has been an enigma, with extensive continental interiors, especially in northeast Asia, modeled as below freezing in spite of plant and other evidence to the contrary. We reconsider the paleoelevations of specific areas, particularly along the northeastern Siberian continental margin, where paleofloras indeed indicate higher temperatures than suggested by current climate models. Evidence for significant masses of ice on land during even the otherwise warmest times of the Cretaceous is solved by reinterpretation of the δ18O record of fossil plankton. The signal interpreted as an increase in ice volume on land is the same as the signal for an increase in the volume of groundwater reservoirs on land. The problem of a warm Arctic, where fossil floras indicate that they never experienced freezing conditions in winter, could not be solved by numerical simulations using higher CO2 equivalent greenhouse gas concentrations. We propose a solution by assuming that paleoelevations were less than today and that there were much more extensive wetlands (lakes, meandering rivers, swamps, bogs) on the continents than previously assumed. Using ~ 8 × CO2 equivalent greenhouse gas concentrations and assuming 50–75% water surfaces providing water vapor as a supplementary greenhouse gas on the continents reduces the meridional temperature gradients. Under these conditions the equatorial to polar region temperature gradients produce conditions compatible with fossil and sedimentological evidence.
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  • 12
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    In:  In: Pattern Recognition - GCPR 2018. , ed. by Brox, T., Bruhn, A. and Fritz, M. Lecture Notes in Computer Science, 11269 . Springer, Cham, Switzerland, pp. 391-404. ISBN 978-3-030-12939-2
    Publication Date: 2019-04-10
    Description: The size of current plankton image datasets renders manual classification virtually infeasible. The training of models for machine classification is complicated by the fact that a large number of classes consist of only a few examples. We employ the recently introduced weight imprinting technique in order to use the available training data to train accurate classifiers in absence of enough examples for some classes. The model architecture used in this work succeeds in the identification of plankton using machine learning with its unique challenges, i.e. a limited number of training examples and a severely skewed class size distribution. Weight imprinting enables a neural network to recognize small classes immediately without re-training. This permits the mining of examples for novel classes.
    Type: Book chapter , PeerReviewed
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  • 13
    Publication Date: 2019-04-30
    Description: A broad variety of materials of biological origin have been successfully used in recent decades for the removal of pollutants from waters. These biosorbents include natural polymers that play a key role for adsorption. It is therefore critical to understand the physicochemical properties of the chemical groups of these biopolymers. The acid–base properties of biomass are affected by pH, ionic strength and medium composition. Nevertheless, these parameters are not always considered during biosorption studies. According to the literature, less than 3% of biosorption reports include studies on proton binding. Moreover, in 60% of these papers, there is key experimental information missing such as the calibration of the electrodes employed for potentiometric titrations. We consider therefore that there is an important need for reviewing the role of proton binding in biosorption studies. This review outlines the major advances on data interpretation and modelling of proton binding on biosorbents. In addition, we discuss issues concerning the acid–base properties of biosorbents.
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  • 14
  • 15
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    In:  A Mathematical Modeling Approach from Nonlinear Dynamics to Complex Systems
    Publication Date: 2018-03-05
    Type: inbook
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  • 16
  • 17
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    In:  In: Geological Setting, Palaeoenvironment and Archaeology of the Red Sea. , ed. by Rasul, N. M. A. and Stewart, I. C. F. Springer, Cham, Switzerland, pp. 221-232.
    Publication Date: 2019-04-16
    Description: Hydrothermal circulation at mid-ocean ridges and assimilation of hydrothermally altered crust or hydrothermal fluids by rising magma can be traced by measuring chlorine (Cl) excess in erupted lavas. The Red Sea Rift provides a unique opportunity to study assimilation of hydrothermally altered crust at an ultra-slow spreading ridge (maximum 1.6 cm yr−1 full spreading rate) by Cl, due to its saline seawater (40–42‰, cf. 35‰ in open ocean water), the presence of (hot) brine pools (up to 270‰ salinity and 68 °C) and the thick evaporite sequences that flank the young rift. Absolute chlorine concentrations (up to 1300 ppm) and Cl concentrations relative to minor or trace elements of similar mantle incompatibility (e.g., K, Nb) are much higher in Red Sea basalts than in basalts from average slow spreading ridges. Mantle Cl/Nb concentrations can be used to calculate the Cl-excess, above the magmatic Cl, that is present in the samples. Homogeneous within-sample Cl concentrations, high Cl/H2O, the decoupling of Cl-excess from other trace elements and its independence of the presence of highly saline seafloor brines at the site of eruption indicate that Cl is not enriched at the seafloor. Instead we find basaltic Cl-excess to be spatially closely correlated with evidence of hydrothermal activity, suggesting that deeper assimilation of hydrothermal Cl is the dominant Cl-enrichment process. A proximity of samples to both evaporite outcrops and bathymetric signs of volcanism on the seafloor enhance Cl-excess in basalts. The basaltic Cl-excess can be used as a tracer together with new bathymetric maps as well as indications of hydrothermal venting (hot brine pools, metalliferous Hydrothermal circulation at mid-ocean ridges and assimilation of hydrothermally altered crust or hydrothermal fluids by rising magma can be traced by measuring chlorine (Cl) excess in erupted lavas. The Red Sea Rift provides a unique opportunity to study assimilation of hydrothermally altered crust at an ultra-slow spreading ridge (maximum 1.6 cm yr−1 full spreading rate) by Cl, due to its saline seawater (40–42‰, cf. 35‰ in open ocean water), the presence of (hot) brine pools (up to 270‰ salinity and 68 °C) and the thick evaporite sequences that flank the young rift. Absolute chlorine concentrations (up to 1300 ppm) and Cl concentrations relative to minor or trace elements of similar mantle incompatibility (e.g., K, Nb) are much higher in Red Sea basalts than in basalts from average slow spreading ridges. Mantle Cl/Nb concentrations can be used to calculate the Cl-excess, above the magmatic Cl, that is present in the samples. Homogeneous within-sample Cl concentrations, high Cl/H2O, the decoupling of Cl-excess from other trace elements and its independence of the presence of highly saline seafloor brines at the site of eruption indicate that Cl is not enriched at the seafloor. Instead we find basaltic Cl-excess to be spatially closely correlated with evidence of hydrothermal activity, suggesting that deeper assimilation of hydrothermal Cl is the dominant Cl-enrichment process. A proximity of samples to both evaporite outcrops and bathymetric signs of volcanism on the seafloor enhance Cl-excess in basalts. The basaltic Cl-excess can be used as a tracer together with new bathymetric maps as well as indications of hydrothermal venting (hot brine pools, metalliferous sediments) to predict where hydrothermal venting or now inactive hydrothermal vent fields can be expected. Sites of particular interest for future hydrothermal research are the Mabahiss Deep, the Thetis-HadarbaHatiba Deeps and Shagara-Aswad-Erba Deeps (especially their large axial domes), and Poseidon Deep. Older hydrothermal vent fields may be present at the Nereus and Suakin Deeps. These sites significantly increase the potential of hydrothermal vent field prospection in the Red Sea.
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  • 18
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    In:  In: Geological Setting, Palaeoenvironment and Archaeology of the Red Sea. , ed. by Rasul, N. M. A. and Stewart, I. C. F. Springer, Cham, Switzerland, pp. 37-52. ISBN 978-3-319-99407-9
    Publication Date: 2019-04-16
    Description: Continental rifting and ocean basin formation can be observed at the present day in the Red Sea, which is used as the modern analogue for the formation of mid-ocean ridges. Competing theories for how spreading begins—either by quasi-instantaneous formation of a whole spreading segment or by initiation of spreading at multiple discrete “nodes” separated by thinned continental lithosphere—have been put forward based, until recently, on the observations that many seafloor features and geophysical anomalies (gravity, magnetics) along the axis of the Red Sea appeared anomalous compared to ancient and modern examples of ocean basins in other parts of the world. The latest research shows, however, that most of the differences between the Red Sea Rift (RSR) and other (ultra)slow-spreading mid-ocean ridges can be related to its relatively young age and the presence and movement of giant submarine salt flows that blanket large portions of the rift valley. In addition, the geophysical data that was previously used to support the presence of continental crust between the axial basins with outcropping oceanic crust (formerly named “spreading nodes”) can be equally well explained by processes related to the sedimentary blanketing and hydrothermal alteration. The observed spreading nodes are not separated from one another by tectonic boundaries but rather represent “windows” onto a continuous spreading axis which is locally inundated and masked by massive slumping of sediments or evaporites from the rift flanks. Volcanic and tectonic morphologies are comparable to those observed along slow and ultra-slow spreading ridges elsewhere and regional systematics of volcanic occurrences are related to variations in volcanic activity and mantle heat flow. Melt-salt interaction due to salt flows, that locally cover the active spreading segments, and the absence of large detachment faults as a result of the nearby Afar plume are unique features of the RSR. The differences and anomalies seen in the Red Sea still may be applicable to all young oceanic rifts, associated with plumes and/or evaporites, which makes the Red Sea a unique but highly relevant type example for the initiation of slow rifting and seafloor spreading and one of the most interesting targets for future ocean research.
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  • 19
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    In:  Springer Oceanography Book series . Springer, Cham, Switzerland, 550 pp. ISBN 978-3-319-99417-8
    Publication Date: 2018-12-14
    Description: This book includes invited contributions presenting the latest research on the oceanography and environment of the Red Sea. In addition to covering topics relevant to research in the region and providing insights into marine science for non-experts, it is also of interest to those involved in the management of coastal zones and encourages further research on the Red Sea
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  • 20
    Publication Date: 2019-02-11
    Description: The present study details the effects of basin-scale hydrographic characteristics of the Red Sea on the macroecology of Chaetognatha, a major plankton component in the pelagic realm. The hydrographic attributes and circulation of the Red Sea as a result of its limited connection with the northern Indian Ocean make it a unique ecohydrographic region in the world ocean. Here, we aimed to identify the prime determinants governing the community structure and vertical distribution of the Cheatognatha in this ecologically significant world ocean basin. The intrusion of Gulf of Aden Water influenced the Chaetognatha community composition in the south, whereas the overturning circulation altered their vertical distribution in the north. The existence of hypoxic waters (〈 100 µmol kg−1) at mid-depth also influenced their vertical distribution. The detailed evaluation of the responses of the different life stages of Chaetognatha revealed an increased susceptibility of adult individuals to hypoxic waters compared to immature stages. Higher oxygen demands of the adults for the egg and sperm production might have prevented them from inhabiting the oxygen-deficient mid-depth zones. The carbon and nitrogen content of the Copepoda and Chaetognatha communities and the quantification of the predation impact of Chaetognatha on Copepoda based on the feeding rate helped in corroborating the significant trophic link between these two prey–predator taxa. The observed influences of physical and chemical attributes on the distribution of Chaetognatha can be used as a model example for the role of the hydrography on the zooplankton community of the Red Sea.
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  • 21
    Publication Date: 2019-03-20
    Description: Climate model components involve both high-dimensional input and output fields. It is desirable to efficiently generate spatio-temporal outputs of these models for applications in integrated assessment modelling or to assess the statistical relationship between such sets of inputs and outputs, for example, uncertainty analysis. However, the need for efficiency often compromises the fidelity of output through the use of low complexity models. Here, we develop a technique which combines statistical emulation with a dimensionality reduction technique to emulate a wide range of outputs from an atmospheric general circulation model, PLASIM, as functions of the boundary forcing prescribed by the ocean component of a lower complexity climate model, GENIE-1. Although accurate and detailed spatial information on atmospheric variables such as precipitation and wind speed is well beyond the capability of GENIE-1’s energy-moisture balance model of the atmosphere, this study demonstrates that the output of this model is useful in predicting PLASIM’s spatio-temporal fields through multi-level emulation. Meaningful information from the fast model, GENIE-1 was extracted by utilising the correlation between variables of the same type in the two models and between variables of different types in PLASIM. We present here the construction and validation of several PLASIM variable emulators and discuss their potential use in developing a hybrid model with statistical components.
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  • 22
    Publication Date: 2019-03-04
    Description: Climate engineering (CE) deployment would alter prevailing relationships between Earth system variables, making indicators and metrics used so far in the climate change assessment context less appropriate to assess CE measures. Achieving a comprehensive CE assessment requires a systematic and transparent reevaluation of the indicator selection process from Earth system variables. Here, we provide a first step towards such a systematic assessment of changes in correlations between Earth system variables following simulated deployment of different CE methods. We therefore analyze changes in the correlation structure of a broad set of Earth system variables for two conventional climate change scenarios without CE and with three idealized CE model experiments: (i) solar radiation management, (ii) large-scale afforestation, and (iii) ocean alkalinity enhancement. First, we investigate how the three CE scenarios alter prevailing correlations between Earth system variables when compared to an intermediate-high and a business-as-usual future climate change scenario. Second, we contrast the indicators identified for the non-CE climate change scenarios and the indicators identified when all five scenarios are considered. Finally, we use the identified indicator sets for an evaluation of the five climate change scenarios. We find that the additional indicators provide valuable information for the assessment of the CE measures, and their application hence allows for a more comprehensive and a comparative assessment of the mitigation and CE deployment scenarios.
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  • 23
    Publication Date: 2019-03-04
    Description: Many marine gastropods show species-specific behavioral responses to different predators, but less is known about the mechanisms influencing differences or similarities in specific responses. Herein, we examined whether two limpet species, Scurria viridula (Lamarck, 1819) and Fissurella latimarginata (Sowerby, 1835), show species- and size-specific similarities or differences in their reaction to predatory seastars and crabs. Both S. viridula and F. latimarginata reacted to their main seastar predators with escape responses. In contrast, both limpets did not flee from common crab predators, but, instead, fastened to the rock. All tested size classes of both limpet species reacted in a similar way, escaping from seastars, but clamping onto the rock in response to crabs. Limpets could reach velocities sufficient to outrun their specific seastar predators, but they were not fast enough to escape crabs. Experiments with limpets of different shell conditions (with and without shell damage) indicated that F. latimarginata with a damaged shell showed “accommodation movements” (slow movements away from stimulus) in response to predatory crabs. In contrast, intact F. latimarginata and all S. viridula (intact and damaged) clamped the shell down to the substratum. The response details suggest that the keyhole limpet F. latimarginata is more sensitive to predators (faster reaction time, longer escape distances, and higher proportion of reacting individuals) than S. viridula, possibly because the morphology of F. latimarginata (the relationship of its shell size and structure to its total body size) makes this species more vulnerable to predation. Our study suggests that chemically mediated effects of seastar and crab predators result in contrasting behavioral responses of both limpet species, independent of their habitat and morphology. Despite the different characteristics of the limpet species and the identity of predators, the limpets react in comparable ways to similar predator types.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 24
    Publication Date: 2019-05-16
    Description: Climate engineering (CE) deployment would alter prevailing relationships between Earth system variables, making indicators and metrics used so far in the climate change assessment context less appropriate to assess CE measures. Achieving a comprehensive CE assessment requires a systematic and transparent reevaluation of the indicator selection process from Earth system variables. Here, we provide a first step towards such a systematic assessment of changes in correlations between Earth system variables following simulated deployment of different CE methods. We therefore analyze changes in the correlation structure of a broad set of Earth system variables for two conventional climate change scenarios without CE and with three idealized CE model experiments: (i) solar radiation management, (ii) large-scale afforestation, and (iii) ocean alkalinity enhancement. First, we investigate how the three CE scenarios alter prevailing correlations between Earth system variables when compared to an intermediate-high and a business-as-usual future climate change scenario. Second, we contrast the indicators identified for the non-CE climate change scenarios and the indicators identified when all five scenarios are considered. Finally, we use the identified indicator sets for an evaluation of the five climate change scenarios. We find that the additional indicators provide valuable information for the assessment of the CE measures, and their application hence allows for a more comprehensive and a comparative assessment of the mitigation and CE deployment scenarios.
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  • 25
    Publication Date: 2019-04-23
    Description: Author Posting. © The Author(s), 2019. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in , Zakroff, C., Mooney, T.A. & Berumen, M.L. Dose-dependence and small-scale variability in responses to ocean acidification during squid, Doryteuthis pealeii, development. Marine Biology, (2019), 166: 62. doi:10.1007/s00227-019-3510-8.
    Description: Coastal squids lay their eggs on the benthos, leaving them to develop in a dynamic system that is undergoing rapid acidification due to human influence. Prior studies have broadly investigated the impacts of ocean acidification on embryonic squid, but have not addressed the thresholds at which these responses occur or their potential variability. We raised squid, Doryteuthis pealeii (captured in Vineyard Sound, Massachusetts, USA: 41° 23.370N 70° 46.418´W), eggs in three trials across the breeding season (May - September, 2013) in a total of six chronic pCO2 exposures (400, 550, 850, 1300, 1900, and 2200 ppm). Hatchlings were counted and subsampled for mantle length, yolk volume, hatching time, hatching success, and statolith morphology. New methods for analysis of statolith shape, rugosity, and surface degradation were developed and are presented (with code). Responses to acidification (e.g., reduced mantle lengths, delayed hatching, and smaller, more degraded statoliths) were evident at ~ 1300 ppm CO2. However, patterns of physiological response and energy management, based on comparisons of yolk consumption and growth, varied among trials. Interactions between pCO2 and hatching day indicated a potential influence of exposure time on responses, while interactions with culture vessel highlighted the substantive natural variability within a clutch of eggs. While this study is consistent with, and expands upon, previous findings of sensitivity of the early life stages to acidification, it also highlights the plasticity and potential for resilience in this population of squid.
    Description: This material was based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. 1122374 to CZ. This project was funded by National Science Foundation Grant No. 1220034 to TAM.
    Description: 2020-04-19
    Keywords: cephalopod ; embryo ; hypercapnia ; paralarvae ; statolith ; stress
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 26
    Publication Date: 2019-06-06
    Description: Differences in habitat and diet between species are often associated with morphological differences. Habitat and trophic adaptation have therefore been proposed as important drivers of speciation and adaptive radiation. Importantly, habitat and diet shifts likely impose changes in exposure to different parasites and infection risk. As strong selective agents influencing survival and mate choice, parasites might play an important role in host diversification. We explore this possibility for the adaptive radiation of Lake Tanganyika (LT) cichlids. We first compare metazoan macroparasites infection levels between cichlid tribes. We then describe the cichlids’ genetic diversity at the major histocompatibility complex (MHC), which plays a key role in vertebrate immunity. Finally, we evaluate to what extent trophic ecology and morphology explain variation in infection levels and MHC, accounting for phylogenetic relationships. We show that different cichlid tribes in LT feature partially non-overlapping parasite communities and partially non-overlapping MHC diversity. While morphology explained 15% of the variation in mean parasite abundance, trophic ecology accounted for 16% and 22% of the MHC variation at the nucleotide and at the amino acid level, respectively. Parasitism and immunogenetic adaptation may thus add additional dimensions to the LT cichlid radiation.
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  • 27
    Publication Date: 2019-05-28
    Description: The spatial pattern of the first mode of interannual variability associated with the East Asian summer monsoon (EASM), obtained from a multivariate Empirical Orthogonal Functions (MV-EOF) analysis, corresponds to the Pacific–Japan (PJ) pattern and is referred to as the PJ-mode. The present study investigates the interannual variation of the PJ-mode from the perspective of the intraseasonal timescale. In particular, the impact of the Madden–Julian oscillation (MJO) on the interannual variation of the PJ-mode is investigated. The results show that the MJO has a significant influence on the interannual variation of the PJ-mode mainly in the lower troposphere (850 hPa) and that the former accounts for approximately 11% of the amplitude of the latter. The major part of the contribution comes from a change in frequency of the different phases of the MJO, especially that of MJO phase 6. This suggests that intraseasonal variation of the convection anomalies over the tropical eastern Indian and western Pacific Oceans plays an important role in the interannual variation of the PJ-mode. In addition, MJO phase 7 also contributes to the interannual variability of the PJ-mode, in this case induced by both the change in frequency and the change in circulation anomalies associated with MJO phase 7.
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  • 28
    Publication Date: 2019-05-28
    Description: Solar signals in the atmosphere and the ocean, especially in tropopause temperatures and lower stratospheric water vapour are investigated using recent observational and reanalyses data sets for the period from 1958 through 2013. Previous observational and modeling studies demonstrated solar influences in the lower stratosphere resembling a positive Northern Annular Mode due to the top-down mechanism involving enhanced solar UV radiation in the stratosphere during solar maxima and dynamical amplification mechanisms in the atmosphere. We found that these stratospheric changes might propagate down to the troposphere and become zonally asymmetric with characteristic pressure and wind pattern over the North Atlantic and North Pacific. Such changes in tropospheric circulation are related to anomalous positive SST anomalies in the central Pacific which resemble an El Niño Modoki event. We show for the first time with ocean reanalysis data that these SST anomalies are amplified by a positive feedback through oceanic subsurface currents and heat transport in the equatorial Pacific. Anomalous warm SSTs in the equatorial central Pacific change the zonal SST gradient and lead to anomalous westerly winds and currents in the western Pacific and easterly winds and currents in the eastern Pacific. This indicates a convergence and less upwelling and therefore enhances the positive SST anomalies in the equatorial central Pacific. Such a positive feedback results in a peak of El Niño Modoki events about 2 years after the solar maximum. These solar-induced signals in the ocean in turn modify the circulation and convection in the troposphere, resulting in lagged solar signals of anomalous high tropopause heights and negative anomalies in tropopause temperatures as well as in lower stratospheric water vapour over the equatorial Pacific which are in agreement with a time evolving solar-induced El Niño Modoki-like SST pattern. We demonstrate a solar modulation of intrinsic decadal climate variability over the Pacific which is amplified by positive feedbacks between the ocean and the atmosphere.
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  • 29
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    In:  Natural Gas Engines: For Transportation and Power Generation | Energy, Environment, and Sustainability
    Publication Date: 2019-06-14
    Description: Lean-burn natural gas engines can be used to reduce exhaust emissions significantly. However, as the mixture is leaned out, the occurrence of extinction and incomplete combustion increases, resulting in poor performance and stability, as well as elevated levels of unburned hydrocarbon (UHC) and nitrogen oxides (NOx) emissions. The partially stratified charge (PSC) method can be used to mitigate these issues, while extending the lean misfire limit (LML) beyond its equivalent, homogeneous level. In this chapter, the PSC ignition and combustion processes are examined following a comprehensive experimental and numerical approach. Experiments are conducted in an idealized PSC configuration, using a constant volume combustion chamber (CVCC), to identify the principle enabling mechanisms of the PSC methodology. Engine tests conducted in a single-cylinder research engine (SCRE) demonstrate the feasibility of various PSC implementations in improving performance and emission characteristics in real-world settings. Complementary numerical analyses for the CVCC are obtained through large eddy simulations (LES), while Reynolds-averaged Navier?Stokes (RANS) simulations are conducted for SCRE with reduced chemical kinetics. The corresponding simulated results provide additional insights in characterizing the effect of fuel stratification on flame kernel maturation and flame propagation, the interplay between chemistry and turbulence at different overall air?fuel ratios, as well as formation of major pollutant species.
    Language: English
    Type: http://purl.org/eprint/type/BookItem
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  • 30
    Publication Date: 2019-06-13
    Description: Diseases increasingly threaten aquaculture of kelps and other seaweeds. At the same time, protection concepts that are based upon application of biocides are usually not applicable, as such compounds would be rapidly diluted in the sea, causing ecological damage. An alternative concept could be the application of immune stimulants to prevent and control diseases in farmed seaweeds. We here present a pilot study that investigated the effects of oligoalginate elicitation on juvenile and adult sporophytes of Saccharina japonica cultivated in China and on adult sporophytes of Saccharina latissima cultivated in Germany. In two consecutive years, treatment with oligoalginate clearly reduced the detachment of S. japonica juveniles from their substrate curtains during the nursery stage in greenhouse ponds. Oligoalginate elicitation also decreased the density of endobionts and the number of bacterial cells on sporophytes of S. latissima that were cultivated on sea-based rafts. However, the treatment increased the susceptibility of kelp adults to settlement of epibionts (barnacles in Germany and filamentous algal epiphytes in China). In addition, oligoalginate elicitation accelerated the aging of S. japonica adults. Based upon these findings, oligoalginate elicitation could be a feasible way to provide “environmentally friendly” protection of kelp juveniles in nurseries. The same treatment causes not only beneficial, but also unwanted effects in adult kelp sporophytes. Therefore, it is not recommended as a treatment after the juvenile stage is completed. Future tests with other elicitors and other cultivated seaweed species may allow for the development of more feasible applications of targeted defense elicitation in seaweed aquaculture.
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  • 31
    Publication Date: 2019-06-14
    Description: Methane gas hydrates have increasingly become a topic of interest because of their potential as a future energy resource. There are significant economical and environmental risks associated with extraction from hydrate reservoirs, so a variety of multiphysics models have been developed to analyze prospective risks and benefits. These models generally have a large number of empirical parameters which are not known a priori. Traditional optimization-based parameter estimation frameworks may be ill-posed or computationally prohibitive. Bayesian inference methods have increasingly been found effective for estimating parameters in complex geophysical systems. These methods often are not viable in cases of computationally expensive models and high-dimensional parameter spaces. Recently, methods have been developed to effectively reduce the dimension of Bayesian inverse problems by identifying low-dimensional structures that are most informed by data. Active subspaces is one of the most generally applicable methods of performing this dimension reduction. In this paper, Bayesian inference of the parameters of a state-of-the-art mathematical model for methane hydrates based on experimental data from a triaxial compression test with gas hydrate-bearing sand is performed in an efficient way by utilizing active subspaces. Active subspaces are used to identify low-dimensional structure in the parameter space which is exploited by generating a cheap regression-based surrogate model and implementing a modified Markov chain Monte Carlo algorithm. Posterior densities having means that match the experimental data are approximated in a computationally efficient way.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 32
    Publication Date: 2019-06-21
    Description: Reproductive systems of rare adult specimens of the deep-sea squid genera Chiroteuthis, Mastigoteuthis, Liocranchia, and Bathoteuthis were collected in 2006 and 2015 in the different research surveys in the Atlantic Ocean between 46 degrees 40'S and 17 degrees 11'N. Whole squids were preserved in 4% buffered formaldehyde solution, subsequently transferred into 70% ethanol and studied in laboratory condition providing initial observations on spawning pattern in these animals. The potential fecundity of Ch. cf. joubini was similar to 45,000-50,000, the maximum egg size was 1.6-1.7 mm, while those of M. agassizii were similar to 8000-16,000 and 1.7-1.9 mm respectively. A maturing female of B. skolops had similar to 4800 eggs of which some similar to 1200 were atretic. The ovary of a spent L. reinhardti contained similar to 116,500 post-ovulatory follicles and no residual egg. Mature females of Chiroteuthis and Mastigoteuthis had spematangia implanted externally in the mantle, whereas Liocranchia had a specialised spermatangia receptacle on the inside of the mantle. Reproductive adaptations of these genera are discussed in relation to spawning habits of other deep-sea squids. Synchronous ovulation was found to be a prevailing type of the gonad development with all eggs being spawned as a single batch, with ot without brooding. In some species, this single batch is not released at once but in several consequent portions exhibiting 'extended synchronous' spawning.
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  • 33
    Publication Date: 2019-06-19
    Description: Common problems in state-of-the-art climate models are a cold sea surface temperature (SST) bias in the equatorial Pacific and the underestimation of the two most important atmospheric feedbacks operating in the El Niño/Southern Oscillation (ENSO): the positive, i.e. amplifying wind-SST feedback and the negative, i.e. damping heat flux-SST feedback. To a large extent, the underestimation of those feedbacks can be explained by the cold equatorial SST bias, which shifts the rising branch of the Pacific Walker Circulation (PWC) too far to the west by up to 30°, resulting in an erroneous convective response during ENSO events. Based on simulations from the Kiel Climate Model (KCM) and the 5th phase of Coupled Model Intercomparison Project (CMIP5), we investigate how well ENSO dynamics are simulated in case of underestimated ENSO atmospheric feedbacks (EAF), with a special focus on ocean–atmosphere coupling over the equatorial Pacific. While models featuring realistic atmospheric feedbacks simulate ENSO dynamics close to observations, models with underestimated EAF exhibit fundamental biases in ENSO dynamics. In models with too weak feedbacks, ENSO is not predominantly wind-driven as observed; instead ENSO is driven significantly by a positive shortwave radiation feedback. Thus, although these models simulate ENSO, which in terms of simple indices is consistent with observations, it originates from very different dynamics. A too weak oceanic forcing on the SST via the positive thermocline, the Ekman and the zonal advection feedback is compensated by weaker atmospheric heat flux damping. The latter is mainly caused by a biased shortwave-SST feedback that erroneously is positive in most climate models. In the most biased models, the shortwave-SST feedback contributes to the SST anomaly growth to a similar degree as the ocean circulation. Our results suggest that a broad continuum of ENSO dynamics can exist in climate models and explain why climate models with less than a half of the observed EAF strength can still depict realistic ENSO amplitude.
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  • 34
    Publication Date: 2019-06-27
    Description: A strong warm event occurred in the southeastern tropical Atlantic Ocean off Angola and Namibia in January and February 2016 with sea surface temperature anomalies reaching 3 °C. In contrast to classical Benguela Niño events, the analysis of various direct observations indicates that the warming was not predominantly forced by an equatorial Kelvin wave exciting a coastally trapped wave but instead resulted from a combination of local processes that are related to (1) a weakening of the alongshore, i.e. mainly southerly, winds and (2) enhanced freshwater input through local precipitation and river discharge. Consistent with the weakened winds, we find a reduction in latent heat loss from the ocean and a poleward surface current anomaly. The surface freshening, which is detected in satellite observations of sea surface salinity, caused a very shallow mixed layer and enhanced upper ocean stratification. This is supported by the analysis of the velocity structure of the Angola Current at 11°S, which shows that at the time of the event subsurface velocities were directed northward while surface velocities were directed southward. The shallow layer of warm and fresh surface water was thus advected poleward by the surface current. In addition, a reduction of the local upwelling and the formation of a barrier layer that inhibits the entrainment of cool subsurface waters into the surface mixed layer might have contributed to the warm surface anomaly. The sudden termination of the warm event was accompanied by a re-intensification of southerly winds in March
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  • 35
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    In:  Climate Dynamics, 53 (1-2). pp. 1111-1124.
    Publication Date: 2019-06-27
    Description: There is a controversy about the origin of the recent decadal Atlantic Meridional Overturning Circulation (AMOC) slowing observed at 26.5°N and concurrent sea surface temperature cooling in the central and eastern mid-latitude North Atlantic. We investigate decadal AMOC slowing events simulated in a multi-millennial preindustrial control integration of the Kiel Climate Model (KCM), providing an estimate of internal AMOC variability. Preindustrial control integrations of 15 models participating in the Coupled Model Intercomparison Project phase 5 also are investigated, as well as historical simulations with them providing estimates of AMOC variability during 1856–2005. It is shown that the recent decadal AMOC decline is still within the range of the models’ internal AMOC variability and thus could be of natural origin. In this case, the decline would represent an extreme realization of internal variability provided the climate models yield realistic levels of AMOC variability. The model results suggest that internal decadal AMOC variability is large, requiring multi-decadal observational records to detect an anthropogenic AMOC signal with high confidence. When analyzing the strongest decadal AMOC slowing events in the KCM, which have amplitudes similar to or larger than the recently observed decadal AMOC decline, the following composite picture emerges: a very strong decadal AMOC decline is preceded by a decadal rise in atmospheric surface pressure over large parts of the mid-latitude North Atlantic. The change in low-level atmospheric circulation drives reduced oceanic heat loss over and diminished upper-ocean salt content in the Labrador Sea. In response, oceanic deep convection and subsequently the AMOC and northward oceanic heat transport weaken, and anomalously cold sea surface temperatures develop in the central and eastern mid-latitude North Atlantic
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  • 36
    Publication Date: 2019-06-27
    Description: Biodiversity is generally believed to be a main determinant of ecosystem functioning. This principle also applies to the microbiome and could consequently contribute to host health. According to ecological theory, communities are shaped by top predators whose direct and indirect interactions with community members cause stability and diversity. Bdellovibrio and like organisms (BALOs) are a neglected group of predatory bacteria that feed on Gram-negative bacteria and can thereby influence microbiome composition. We asked whether BALOs can predict biodiversity levels in microbiomes from distinct host groups and environments. We demonstrate that genetic signatures of BALOs are commonly found within the 16S rRNA reads from diverse host taxa. In many cases, their presence, abundance, and especially richness are positively correlated with overall microbiome diversity. Our findings suggest that BALOs can act as drivers of microbial alpha-diversity and should therefore be considered candidates for the restoration of microbiomes and the prevention of dysbiosis.
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  • 37
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    Publication Date: 2019
    Print ISSN: 1567-9764
    Electronic ISSN: 1573-1553
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Political Science , Economics
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  • 38
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉Recurring themes in the literature on European environmental policy-making is the leader–laggard spectrum and regulatory competition. European environmental policy is driven towards expansion because certain states take up leadership roles and manage to have their preferred regulatory solution adopted by the relevant European policy-making institution. During the policy process, leaders face ‘laggards’, states that do not favour ambitious regulation and drag their feet. The leader–laggard spectrum is volatile. States play different roles depending on the issue of interest, and over time their roles shift as well. This article investigates the role of relatively small-scale national events on the position of states on the spectrum. The regulatory competition involved in the leader–laggard spectrum may create an amplification effect of national problems: Through the efforts of the state afflicted by it, they acquire a European dimension they might otherwise not have had. They can cause member states to exhibit an extraordinary interest in a certain policy field and certain type of regulation for a brief period of time, shaping it considerably. After that, specific national problem has been solved or has blown over though they withdraw, leaving a gap for new contenders to fill. Yesterday’s champions may be the laggards of tomorrow and vice versa. New champions bring their specific regulatory styles, their favourite solutions and their policy-making philosophy to bear on EU environmental regulation, exacerbating the already patchy character of this policy field.〈/p〉
    Print ISSN: 1567-9764
    Electronic ISSN: 1573-1553
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Political Science , Economics
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  • 39
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉Numerous recent studies project that ‘climate engineering’ technologies might need to play a major role in the future. Such technologies may carry major risks for developing countries that are often especially vulnerable to, and lack adaptive capacity to deal with, the impacts of such new technologies. In this situation, one would expect that developing countries—especially the least developed countries that are most vulnerable—should play a central role in the emerging discourse on climate engineering. And yet, as this article shows in detail, the discussion about whether and how to engage with these technologies is shaped by experts from just a small set of countries in the Global North. Knowledge production around climate engineering remains heavily dominated by the major research institutions in North America and Europe. Drawing on information from 70 climate engineering events between 2009 and 2017 along with extensive document analysis, the article maps a lack of involvement of developing countries and highlights the degree to which their concerns remain insufficiently represented in politically significant scientific assessment reports. The article concludes by sketching options that developing countries may have to influence the agenda on climate engineering, reflecting on earlier attempts to increase control over novel technologies and influence global agenda setting.〈/p〉
    Print ISSN: 1567-9764
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Political Science , Economics
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  • 40
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉A trinity composed of legally binding regulations, an independent financial mechanism, and a compliance mechanism characterizes the institutional design of the Minamata Convention on Mercury. Meanwhile, few existing environmental treaties feature an independent financial mechanism as well as a compliance mechanism. Why did the Minamata Convention acquire two mechanisms? There are two rival hypotheses on uncertainty about institutional consequences and international agreements. The rational design school posits that countries can predict institutional consequences by acquiring all pieces of relevant information and views the trinity as a rational design to enhance developing countries’ regulatory capabilities under strict compliance. In contrast, the institutional diffusion school assumes that countries have limited information-processing abilities and use cognitive heuristics in designing institutions and argues that countries designed the trinity by learning from existing cases. In this paper, I compare the negotiations process of the Minamata Convention with that of the Stockholm Convention on Persistent Organic Pollutants (POPs). To test the hypotheses, I examine how countries resolved informational uncertainty in both negotiations by utilizing negotiations records and personal interviews with key officials as data. The analytical results support the institutional diffusion hypothesis by indicating that the trinity within the Minamata Convention is a product of countries’ heuristic and incremental learning from existing treaties.〈/p〉
    Print ISSN: 1567-9764
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    Topics: Energy, Environment Protection, Nuclear Power Engineering , Political Science , Economics
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  • 41
    Publication Date: 2019
    Description: The State Forest Inventory (SFI) in the Russian Federation is a relatively new project that is little known in the English-language scientific literature. Following the stipulations of the Forest Act of 2006, ...
    Electronic ISSN: 2197-5620
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 42
    Publication Date: 2019
    Description: We investigated how the precision and costs of forest resource estimates for sample plots of different type and size depend on the spatial structure of forests and jointly studied the effects of tree density a...
    Electronic ISSN: 2197-5620
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 43
    Publication Date: 2019
    Description: The effect of forest fire on soil is complex and relatively less understood than its above ground effect. Understanding the effect of fire on forest soils can allow improving management of valuable forest ecos...
    Electronic ISSN: 2197-5620
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 44
    Publication Date: 2019
    Description: European forests are considered a crucial resource for supplying biomass to a growing bio-economy in Europe. This study aimed to assess the potential availability of forest biomass from European forests and it...
    Electronic ISSN: 2197-5620
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 45
    Publication Date: 2019
    Description: Ecologists are interested in assessing the spatial and temporal variation in ecological surveys repeated over time. This paper compares the 1985 and 2015 surveys of the Barro Colorado Forest Dynamics plot (BCI...
    Electronic ISSN: 2197-5620
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 46
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    Springer
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉Understanding the drivers of aerobic methane (CH〈sub〉4〈/sub〉) oxidation (MOX) is paramount in assessing the current and potential future CH〈sub〉4〈/sub〉 emissions from freshwater aquatic systems. Regulation of MOX kinetics is a complex function of CH〈sub〉4〈/sub〉 and oxygen (O〈sub〉2〈/sub〉) concentrations. While MOX activity is usually proportional to the concentration of CH〈sub〉4〈/sub〉 itself, the effects of O〈sub〉2〈/sub〉 have been more conflicting, with maximum MOX rates often restricted to low O〈sub〉2〈/sub〉 concentrations. Despite the complexity involved, MOX kinetics are often modelled as monotonic positive functions of both CH〈sub〉4〈/sub〉 and O〈sub〉2〈/sub〉 concentrations. We conducted a series of incubation experiments using natural and unamended water samples obtained from multiple depths in northern temperate lakes that vary widely and independently in their CH〈sub〉4〈/sub〉 and O〈sub〉2〈/sub〉 concentrations. Our results showed the expected positive effect of CH〈sub〉4〈/sub〉 concentration and temperature but also demonstrated the strong inhibitory effects of O〈sub〉2〈/sub〉 at high concentration. We then developed a general model describing the kinetics of MOX, simultaneously integrating the effects of CH〈sub〉4〈/sub〉 concentration, temperature as well as the non-linear effect O〈sub〉2〈/sub〉 on MOX activity. The model revealed an overall temperature dependency (activation energy = 0.49 ± 0.06 eV) much lower than reported for methanogenesis and an optimal O〈sub〉2〈/sub〉 level around 15 μmol O〈sub〉2〈/sub〉 L〈sup〉−1〈/sup〉 where maximum MOX activity occurs, regardless of CH〈sub〉4〈/sub〉 concentration and temperature. We further show that ignoring the inhibitory effect of O〈sub〉2〈/sub〉 can lead to significant bias in calculating the expected MOX rates in different portions of the water column.〈/p〉
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  • 47
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉Submerged rice cultivation is characterized by redox fluctuations and results in the formation of paddy soils, often accompanied by soil organic carbon (SOC) accumulation. The impact of redox fluctuations and the underlying soil type on the fate of organic carbon (OC) in paddy soils are unknown. Hence, we mimicked paddy soil development in the laboratory by exposing two soil types with contrasting mineral assemblages (Alisol and Andosol) to eight anoxic–oxic cycles over 1 year. Soils regularly received 〈sup〉13〈/sup〉C-labeled rice straw. As control we used a second set of samples without straw addition as well as samples under static oxic conditions with and without straw. Headspaces were analyzed for carbon dioxide and methane as well as their δ〈sup〉13〈/sup〉C signatures, whereas soil solutions were analyzed for redox potential, pH, dissolved iron, and dissolved organic carbon (DOC and DO〈sup〉13〈/sup〉C). At the end of the experiment, when eight redox cycles were completed, mineral-associated organic matter (MOM) was isolated by density fractionation and characterized for δ〈sup〉13〈/sup〉C, non-cellulosic carbohydrates, and lignin-derived phenols. Moreover, changes in the soil’s microbial community structure were measured. For both soil types, headspace data confirmed less respiration in straw-amended soils with redox fluctuation than in those under static oxic conditions. The δ〈sup〉13〈/sup〉C data revealed that, irrespective of soil type, straw carbon allocation into MOM was larger in soils with redox fluctuation than in those with static oxic conditions. A net increase in MOM after the one-year incubation, however, was only observed in the respective Andosol, probably due to abundant reactive minerals capable of OC uptake. In the Alisol, straw OC most likely exchanged initial MOM. A potential for lignin accumulation in the MOM of soils incubated with straw and redox fluctuation was observed for both soil types. Lignin and carbohydrates suggest a plant origin of MOM formed under redox fluctuation. The initially similar bacterial community composition of the Alisol and Andosol changed differently under redox fluctuation. The stronger change in the Alisol indicates less protective microbial habitats. In summary, the overall turnover of straw OC in soils under redox fluctuation seems to be independent of soil type, while net accumulation of SOC as well as the evolution of the bacterial community structure may in part depend on soil type, suggesting an impact of the soil’s mineral composition.〈/p〉
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  • 48
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉Seasonal hypoxia on the Louisiana continental shelf (LCS) has grown to over 22,000 km〈sup〉2〈/sup〉 with limited information available on how low oxygen effects the benthos. Benthic macrofaunal colonization and sediment biogeochemical parameters were characterized at twelve stations in waters 10–50 m deep along four transects spanning 320 km across the LCS hypoxic zone in the early fall of 2010 when bottom waters typically return to oxic conditions. Chemical data and sediment profile imaging (SPI) support three primary mechanistic pathways of organic matter degradation on the LCS: (i) metal oxide cycling in depositional muds, (ii) infauna-driven bioturbation delivering oxygen below the sediment–water interface, and (iii) sulfate reduction in sediments where iron oxide availability is limited. The transect nearest the Mississippi River delta had the highest concentrations of porewater and solid phase Mn and Fe with SPI images of recently deposited reddish, mixed muddy sediments suggestive of metal cycling. The deepest stations had high oxidized iron concentrations and rust colored sediments with faunal colonization that suggests sediments are oxidized via bioturbation. Many nearshore and central LCS stations had more black sediments, more disturbed clay layers, lower amounts of oxidized iron, and higher sulfate reduction rates than the deepest stations. Sediment mixing coefficients, 〈em〉D〈/em〉〈sub〉〈em〉B〈/em〉〈/sub〉, determined from chlorophyll-〈em〉a〈/em〉 concentration profiles varied between 33 and 183 cm〈sup〉−2〈/sup〉 year〈sup〉−1〈/sup〉. 〈em〉D〈/em〉〈sub〉〈em〉B〈/em〉〈/sub〉 values were highest at the deepest stations where sediments were colonized. 〈em〉D〈/em〉〈sub〉〈em〉B〈/em〉〈/sub〉 were not determined at two nearshore stations where chlorophyll-〈em〉a〈/em〉 concentrations were highly variable in surficial sediments, and on the eastern shelf where sedimentation is high. This study provides a regional view of benthic faunal colonization and sediment biogeochemistry on the LCS, describes regions with potentially different pathways of organic matter degradation, and demonstrates the importance of both bioturbation and physical mixing in processing the large amounts of organic matter in river-dominated continental shelf systems.〈/p〉
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  • 49
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉Precipitation events are increasing in intensity in the Midwestern US due to climate change. This is resulting in flooding of poorly-drained upland soils, which can feed back on climate change by altering greenhouse gas (GHG) emissions, including nitrous oxide (N〈sub〉2〈/sub〉O) and carbon dioxide (CO〈sub〉2〈/sub〉). The objective of this study was to determine if soil drainage history affects the response of soil GHG emissions to rain events. To do this, we measured N〈sub〉2〈/sub〉O and CO〈sub〉2〈/sub〉 fluxes from poorly-drained (PD) and well-drained (WD) soils in an agricultural field in Urbana, Illinois before and after large rain events. We also performed a lab experiment to separate effects of soil drainage history from contemporary effects of ponding. Finally, we utilized stable isotope techniques to measure gross N〈sub〉2〈/sub〉O dynamics and to determine the contributions of nitrifiers and denitrifiers to net N〈sub〉2〈/sub〉O fluxes. We found that ponding of WD soils led to pulses of net N〈sub〉2〈/sub〉O efflux caused by stimulation of gross N〈sub〉2〈/sub〉O production by denitrifiers. In contrast, PD soils had high net N〈sub〉2〈/sub〉O effluxes only between large rain events, and gross N〈sub〉2〈/sub〉O production was inhibited following ponding. Soil CO〈sub〉2〈/sub〉 efflux was greater from PD soils under lab conditions, but autotrophic respiration obscured this trend in the field. Soil GHG emissions were a result of different contemporary ponding status as well as historical soil drainage, suggesting that historical soil redox regimes regulate soil GHG dynamics in response to precipitation. These soil drainage legacy effects are likely important in predicting soil GHG feedback effects on climate change.〈/p〉
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  • 50
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉Recent global warming models project a significant change in winter climate over the next few decades. The decrease in snowpack in the winter will decrease the heat insulation function of the snowpack, resulting in increased soil freeze–thaw cycles. Here, we examined the impact of winter freeze–thaw cycles on year-round dissolved nitrogen (N) and carbon (C) dynamics and their relationship with dissolved organic matter and microbial biomass in soil by conducting an in situ experimental reduction in snowpack. We investigated dissolved inorganic N (NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉 and NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉), dissolved organic N (DON), dissolved organic carbon (DOC), inorganic N leaching, soil microbial biomass, and microbial activities (mineralization and nitrification) in the surface soil of a northern hardwood forest located in Japan. Experimental snowpack reduction significantly increased the number of soil freeze–thaw cycles and soil frost depth. The NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉 content of the surface soil was significantly increased by the amplified soil freeze–thaw cycles due to decreased snowpack, while the soil NO〈sub〉3〈/sub〉〈sup〉–〈/sup〉 content was unchanged or decreased slightly. The gravimetric soil moisture, DON and DOC contents in soil and soil microbial biomass significantly increased by the snowpack removal in winter. Our results suggest that the amplified freeze–thaw cycles in soil increase the availability of DON and DOC for soil microbes due to an increase in soil freezing. The increases in both DON and DOC in winter contributed to the enhanced growth of soil microbes, resulting in the increased availability of NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉 in winter from net mineralization following an increase in soil freeze–thaw cycles. Our study clearly indicated that snow reduction significantly increased the availability of dissolved nitrogen and carbon during winter, caused by increased soil water content due to freeze–thaw cycles in winter.〈/p〉
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  • 51
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉“〈em〉Candidatus〈/em〉 Methylomirabilis oxyfera” (〈em〉M. oxyfera〈/em〉) bacteria has attracted much attention recently since it plays an important role in performing methane oxidation. Most studies on 〈em〉M. oxyfera〈/em〉-like bacteria have been carried out in freshwater ecosystems, however it remains unclear about its distribution along the salinity gradient of estuarine and coastal environments. In this study, we used molecular analyses to reveal the community, diversity and abundance of 〈em〉M. oxyfera〈/em〉-like bacteria in the Yangtze estuarine and coastal sediments. Clone library analyses confirmed the wide distributions of 〈em〉M. oxyfera〈/em〉-like bacterial 16S rRNA and 〈em〉pmoA〈/em〉 genes in the study area. The 〈em〉M. oxyfera〈/em〉-like bacterial 16S rRNA gene sequences were grouped into eleven separate OTUs, which were assigned to groups A and B of 〈em〉M. oxyfera〈/em〉-〈em〉like〈/em〉 bacteria. Most sequences (89.4–97.6% of total sequences) of 〈em〉M. oxyfera〈/em〉-like bacterial 16S rRNA gene were affiliated with group B, while only few clone sequences (2.4–10.6% of total sequences) were affiliated with group A. The retrieved 〈em〉M. oxyfera〈/em〉-like bacterial 〈em〉pmoA〈/em〉 gene sequences were grouped into five distinct clusters. Bray–Curtis dissimilarity of 〈em〉M. oxyfera〈/em〉-like bacterial 16S rRNA and 〈em〉pmoA〈/em〉 genes differed greatly among the low, middle and high salinity sites. 〈em〉M. oxyfera〈/em〉-like bacterial 16S rRNA and 〈em〉pmoA〈/em〉 abundances were mainly recovered from the oligohaline sites rather than from the saline sites. In addition, the large differences in 16S rRNA and 〈em〉pmoA〈/em〉 gene sequences between estuarine and land freshwater environments suggested that salinity could be able to affect the community distribution of 〈em〉M. oxyfera〈/em〉-like bacteria. Also, sediment nitrate/ammonium played an important role in affecting the 〈em〉M. oxyfera〈/em〉-like bacteria. Overall, these results indicate that salinity has a great influence on 〈em〉M. oxyfera〈/em〉-like bacteria community in estuarine environments.〈/p〉
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  • 52
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉River ecosystem dynamics are strongly regulated by the surrounding watershed. The availability and sources of energy and nutrient resources that drive these systems are controlled by topography, climate, geology, and position in the watershed. Here we examined particulate and dissolved organic matter (POM and DOM, respectively) and nutrient concentrations across an entire watershed during multiple flow regimes in an unregulated, low gradient river with extensive floodplain forests. The objectives of the study were to: (1) determine the influence of watershed position and floodplain connectivity on POM, DOM, and nutrient concentrations; (2) examine the influence of flow variability on POM, DOM, and nutrient concentrations; and (3) develop an empirical rating curve to predict POM, DOM, and nutrient transport and flux. We sampled POM, DOM, and nutrient concentrations (ammonia, nitrate, nitrite and soluble reactive phosphorus) at ten sites across the Sipsey River watershed that varied in their degree of connectivity to the floodplain over a two-year period. Both watershed position and flow regime influenced POM, DOM, and nutrient concentrations. In particular, a large floodplain swamp in the middle of the watershed, the Sipsey Swamp, strongly controlled the relative availability of particulate and dissolved materials in the water. In the headwaters, there was a greater proportion of particulate material in suspension relative to dissolved carbon. While in the downstream reaches, both within and downstream of the Sipsey Swamp, DOC accompanied by greater molecular mass and more aromatic DOM was in greater quantity than particulate materials at high flows. Nutrient concentrations in the stream water tended to decline through the floodplain swamp across all flow conditions and tended to be lower in high flows. We demonstrate that floodplains can disrupt the upstream–downstream continuum by supplying a large quantity of allochthonous organic matter. Using long-term data we estimated the total annual flux of DOC and nitrate to range between 1221–6500 and 24–35 tonnes per year, respectively, between 2007 and 2017 with the highest flux rates occurring during high flow periods. Our study shows the complex dynamics of a natural floodplain river system and generally supports the flood pulse concept by highlighting the importance of wetland complexes and floodplain connectivity on material and nutrient transport. Description of organic matter and nutrient dynamics in natural low gradient rivers is critical to understanding production of organisms, food webs and ecosystem processes in the face of climate and land use changes.〈/p〉
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  • 53
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉Water treatment wetlands are increasingly being used to reduce pollutant loads including nitrogen (N) in urban runoff. Processes such as denitrification (DNF) and anaerobic ammonium oxidation (anammox), which remove N, and dissimilatory nitrate reduction to ammonium (DNRA), which recycles N, play an important role in controlling NOx (NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉 + NO〈sub〉2〈/sub〉〈sup〉−〈/sup〉) removal versus recycling in wetlands. The relative importance of DNF, anammox and DNRA was investigated in four constructed stormwater urban wetlands in Melbourne, Australia. Rates of DNF and DNRA were variable and did not differ significantly among wetlands. However, rates of DNF and DNRA were significantly different (p 〈 0.05) in different seasons. The relationship between NOx reduction processes and measured concentrations of water column NOx, chlorophyll a (chl-〈em〉a〈/em〉), sediment organic carbon (OC), porewater ferrous iron (Fe〈sup〉2+〈/sup〉) and sulfide (S〈sup〉2−〈/sup〉) and water column temperature were examined using multiple regression analysis (MRA). Anammox was an insignificant pathway (〈 0.05% of total nitrate reduction). During winter when average water column temperatures were 12 °C, DNRA was consistently higher than DNF averaging 67 ± 23% of total NOx reduction. The MRA revealed that DNF was positively associated with NOx concentration whereas DNRA was negatively associated with temperature, and porewater Fe〈sup〉2+〈/sup〉, and positively associated with chl-〈em〉a〈/em〉. The ratio between DNF and DNF:(DNF + DNRA) showed a positive correlation with both temperature and NOx concentration in the MRA. At higher temperatures and higher NOx concentrations, DNF increased over DNRA. Overall, this study suggests that at low NOx concentrations, N is recycled internally in these urban stormwater wetlands, but the portion of N removed by DNF increases as NOx concentrations increase.〈/p〉
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  • 54
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉Acidic forest soils with two dominant understories, bilberry (〈em〉Vaccinium myrtillus〈/em〉 L.) or alpine lady fern (〈em〉Athyrium distentifolium〈/em〉 Tausch ex Opiz), have been investigated to evaluate the influence of the understory on sorption properties and aluminium behaviour. We investigated acidity, cation exchange properties, organic matter content (SOM) and quality as well as Al bonding to organic matter in humus horizons of soils taken from two different locations. SOM was the major contributor to total cation exchange capacity (CEC〈sub〉t〈/sub〉) and effective cation exchange capacity (CEC〈sub〉e〈/sub〉), and a strong relationship was found between SOM and both CEC〈sub〉t〈/sub〉 and CEC〈sub〉e〈/sub〉, independently of the understory and location. SOM differed in quality, having more fulvic acids in soils under bilberry than in soils under alpine lady fern. For that reason, SOM in soils under bilberry complexed more Al in the exchangeable form in the soluble fulvic acid fraction such that they could be easily washed out, while in soils under alpine lady fern aluminium was mainly bound more stably. We also found that the chemical character of Al depended on the understory type. In soils under bilberry the relation between base saturation and pH could be successfully modelled by a modified Henderson–Hasselbalch equation when Al was considered as a base cation, which is typical for forest podzols. However, in soils under alpine lady fern, this model was efficient only when Al was treated as an acid cation. We concluded that alpine lady fern as the main understory species reduces solubility and potential toxicity of aluminium, thus significantly affecting soil biogeochemistry.〈/p〉
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  • 55
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉Uranium contamination of groundwater remains a pressing problem at many former uranium mining and milling operations, such as the Rifle, Integrated Field Research Challenge (IFRC) site. Biostimulation of the subsurface with an organic carbon source such as acetate, followed by the microbially-induced reductive precipitation of uranium has been proposed as an effective remediation strategy. While uranium bioreduction has been studied in several field experiments, the transformation and fate of injected carbon remains poorly understood. This study evaluated the impact of added organic carbon on the long-term biogeochemical attenuation of uranium in the subsurface of a former mill tailings site. Fluorescence and ultraviolet–visible absorbance analyses were used together with dissolved organic carbon (DOC) measurements to track organic carbon dynamics during and post-biostimulation of the 2011 Rifle IFRC experiment. An electron mass balance was performed on well CD01 to account for any unidentified carbon sinks. Measured DOC values increased to 1.76 mM-C during biostimulation, and to 3.18 mM-C post-biostimulation over background DOC values of 0.3–0.4 mM-C. Elevated DOC levels persisted for 90 days after acetate injections ceased. The electron mass balance revealed that assumed electron acceptors would not account for the total amount of acetate consumed. Excitation–emission matrices showed an increase in signals associated with soluble microbial products, during biostimulation, which disappeared post-biostimulation despite an increase in total DOC. Specific ultraviolet absorbance analyses, indicated that DOC present post-biostimulation is less aromatic in nature, compared to background DOC. Our results suggest that microbes convert injected acetate into a form of solid phase organic matter that may be available to sustain iron reduction post-stimulation.〈/p〉
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  • 56
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉This study evaluated the interactive effects of combined phosphorus (P) and potassium (K) additions on canopy nitrogen (N) retention (CNR) and subsequent canopy leaching at a long-term N manipulation site on Whim bog in south Scotland. Ambient deposition is 8 kg N ha〈sup〉−1〈/sup〉 year〈sup〉−1〈/sup〉 and an additional 8, 24, and 56 kg N ha〈sup〉−1〈/sup〉 year〈sup〉−1〈/sup〉 of either ammonium (NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉) or nitrate (NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉) with or without P and K has been applied over 11 years. Throughfall N deposition below 〈em〉Calluna vulgaris〈/em〉 and foliar N and P concentrations were assessed. Results showed that 60% for low dose and 53% for high dose of NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉 contrasting with 80% for low dose and 38% for high dose of NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉 onto 〈em〉Calluna〈/em〉 was retained by 〈em〉Calluna〈/em〉 canopy. The CNR was enhanced by P and K addition in which 84% of NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉 and 83% of NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉 for high dose were retained. CNR for NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉 increased the canopy leaching of dissolved organic N (DON) and associated organic anions. NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉 retention increased canopy leaching of magnesium and calcium through ion exchange. Even over 11-years N exposure without P and K, foliage N:P ratio of 〈em〉Calluna〈/em〉 did not increase, suggesting that N exposure did not lead to N saturation of 〈em〉Calluna〈/em〉 at Whim bog. Our study concluded that increases in P and K availability enhance CNR of 〈em〉Calluna〈/em〉 but accelerate the associated canopy leaching of DON and base cations, depending on foliar N status.〈/p〉
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  • 57
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉Higher nitrogen fluxes through estuaries increase the risk of harmful algal blooms, may expand eutrophication and can cause hypoxia within estuaries and the adjacent coastal areas. However, the key factors controlling dissolved inorganic nitrogen (DIN) concentrations and export from hydrologically dynamic and turbid estuarine systems are still poorly understood. A series of cruises with high spatial resolution under different hydrological conditions were conducted in 2015–2016 across the Jiulong River Estuary (JRE) continuum, including the estuarine turbidity maximum (ETM). During baseflow, ETMs were more intense during spring tides than neap tides due to stronger net sediment resuspension. The turbidity maxima were stronger and generally further downstream under flood-affected conditions. Based on the distribution of ammonium on the salinity gradient in the low salinity region of the estuary (〈 2 PSU), we grouped all the cruises into “NH〈sub〉4〈/sub〉 Addition Pattern (AP)” and “NH〈sub〉4〈/sub〉 Removal Pattern (RP)”. During baseflow, AP occurred during neap tides and RP during spring tides. An important source of ammonium to the water column was from resuspended sediments and their pore waters. Based on property-salinity plots, nitrification was likely one of the most important transformation processes in the turbid water column of the JRE, resulting in the net removal of ammonium and the net addition of nitrite. It was more intense during spring tides because there were more suspended particles carrying nitrifying bacteria. There was a major addition of DIN from estuarine processes in addition to the extra nitrogen flushed from the catchment during flood-affected flow, in particular during the first flood of the year, compared with a comparatively minor addition during baseflow. This additional DIN was likely from the breakdown products of particulate organic nitrogen accumulated in sediments which were then resuspended under flood-affected conditions.〈/p〉
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  • 58
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉Aggressive behaviour plays a fundamental role in the distribution of limiting resources. Thereby, it is expected to have consequences for fitness. Here, we explored the relationship between aggression and fitness in a long-term database collected in a wild population of the collared flycatcher (〈em〉Ficedula albicollis〈/em〉). We quantified the aggression of males during nest-site defence by conducting simulated territorial intrusions in the courtship period. We estimated the fitness of males based on their pairing success, breeding output and survival to next year. Earlier arriving and older males had a higher probability to establish pair-bond, and males that started to breed earlier fledged more young. Aggression did not predict pairing and breeding performances. However, the probability of a male to return in the next year was significantly related to aggression in an age-dependent manner. Among subadult males, more aggressive individuals had higher chances to return, while among adult males, less aggressive ones did so. This finding is in harmony with our general observation that subadult collared flycatcher males behave more aggressively than adult males when confronted with a conspecific intruder. Subadult males may be socially inexperienced, so they should be more aggressive to be successful. In contrast, if adult males suffer from higher physiological costs, a lower level of aggression may be more advantageous for them. Our study shows that aggressive behaviour can be a fitness-related trait, and to understand its role in determining fitness, age should be taken into account.〈/p〉
    Print ISSN: 0028-1042
    Electronic ISSN: 1432-1904
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
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  • 59
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉In the last 40 years, large areas of the Mau forest, the largest contiguous tropical montane forest in East Africa, have been cleared for agriculture. To date, there are no empirical data on how this land use change affects carbon dioxide (CO〈sub〉2〈/sub〉) fluxes from soil respiration and soil methane (CH〈sub〉4〈/sub〉) fluxes. This study reports measured annual soil CO〈sub〉2〈/sub〉 and CH〈sub〉4〈/sub〉 fluxes from the native Mau forest and previously forested lands converted to smallholder grazing land, smallholder and commercial tea plantations and eucalyptus plantations. Fluxes were measured weekly from August 2015 to August 2016 using the static chamber method. Grazing lands had the highest (p = 0.028) cumulative respiratory CO〈sub〉2〈/sub〉 fluxes (25.6 ± 2.9 Mg CO〈sub〉2〈/sub〉–C ha〈sup〉−1〈/sup〉 year〈sup〉−1〈/sup〉), whereas lowest fluxes were observed in commercial tea plantations (5.6 ± 0.5 Mg CO〈sub〉2〈/sub〉–C ha〈sup〉−1〈/sup〉 year〈sup〉−1〈/sup〉). Soil respiratory CO〈sub〉2〈/sub〉 fluxes were positively correlated with soil pH, but negatively correlated with soil C:N ratio. Annual soil fluxes were explained by soil pH, bulk density and the interaction between soil pH and C:N ratio. Most soils were sinks for atmospheric CH〈sub〉4〈/sub〉 across all land use types. Methane uptake was highest for native forest sites (− 3.08 ± 0.35 to − 5.84 ± 0.61 kg CH〈sub〉4〈/sub〉–C ha〈sup〉−1〈/sup〉 year〈sup〉−1〈/sup〉) and for eucalyptus plantations (− 3.43 ± 0.19 kg CH〈sub〉4〈/sub〉–C ha〈sup〉−1〈/sup〉 year〈sup〉−1〈/sup〉). Uptake decreased significantly with increasing land use intensity (smallholder tea plantations: − 1.42 ± 0.09 kg CH〈sub〉4〈/sub〉–C ha〈sup〉−1〈/sup〉 year〈sup〉−1〈/sup〉, commercial tea plantations: − 1.44 ± 0.29 kg CH〈sub〉4〈/sub〉–C ha〈sup〉−1〈/sup〉 year〈sup〉−1〈/sup〉). Soils of smallholder grazing lands had the lowest CH〈sub〉4〈/sub〉 uptake rates (− 0.36 ± 0.25 kg CH〈sub〉4〈/sub〉–C ha〈sup〉−1〈/sup〉 year〈sup〉−1〈/sup〉). Annual CH〈sub〉4〈/sub〉 uptake was negatively correlated with mean annual soil water-filled pore space (p 〈 0.01) and bulk density (p = 0.003) and decreased with increasing soil inorganic NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉 concentrations (p = 0.03). Annual soil CH〈sub〉4〈/sub〉 can be explained by mainly soil water content and bulk density and these factors are related to gas diffusion. Our study shows that converting tropical montane forests to managed land use types affects soil CO〈sub〉2〈/sub〉 and CH〈sub〉4〈/sub〉 fluxes. Specifically, the CH〈sub〉4〈/sub〉 sink strength in managed land use types of these montane tropical soils was reduced to less than half of the sink strength in the native forest. Soil respiratory CO〈sub〉2〈/sub〉 fluxes were also altered by land use with grazing lands emitting 3–4 times more CO〈sub〉2〈/sub〉 than the other land use types.〈/p〉
    Print ISSN: 0168-2563
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    Topics: Chemistry and Pharmacology , Geosciences
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  • 60
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    Springer
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉The study addresses 〈em〉in vitro〈/em〉 degradation potential of airborne 〈em〉Aspergillus〈/em〉 and 〈em〉Penicillium〈/em〉/〈em〉Talarmyces〈/em〉 species originating from cultural heritage conservation premises. A series of rapid, cost effective biodegradation assays were performed to assess production of extracellular pigments, acids, and enzymes. Most of the isolates have demonstrated positive growth in at least one of the preformed tests. Strongest overall degradation potential was demonstrated for 〈em〉Penicillium brevicompactum〈/em〉, 〈em〉P. glabrum〈/em〉, and 〈em〉Talaromyces sayulitensis〈/em〉 while 〈em〉Aspergillus domesticus〈/em〉, 〈em〉A. penicillioides〈/em〉, 〈em〉A. pseudoglaucus〈/em〉, and 〈em〉A. ruber〈/em〉 did not exhibit positive reaction in any of the employed assays. Majority of isolates exhibited proteolytic and cellulolytic activity while carbonate dissolution was observed for only five tested fungi. Highest alteration of pH value in liquid media was documented for 〈em〉T. sayulitensis〈/em〉 while 〈em〉A. niger〈/em〉 and 〈em〉P. expansum〈/em〉 exhibited strongest acid production on CREA. Certain isolates, mostly 〈em〉Penicillium〈/em〉 species, displayed production of extracellular pigments. The results imply that many of the tested fungi have significant biodegradation capacity, indicating their potential to inflict structural and esthetic alterations on cultural heritage objects.〈/p〉
    Print ISSN: 0028-1042
    Electronic ISSN: 1432-1904
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
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  • 61
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉Most studies on animal personality evaluate individual mean behaviour to describe individual behavioural strategy, while often neglecting behavioural variability on the within-individual level. However, within-individual behavioural plasticity (variation induced by environment) and within-individual residual variation (regulatory behavioural precision) are recognized as biologically valid components of individual behaviour, but the evolutionary ecology of these components is still less understood. Here, we tested whether behaviour of common pill bugs (〈em〉Armadillidium vulgare〈/em〉) differs on the among- and within-individual level and whether it is affected by various individual specific state-related traits (sex, size and 〈em〉Wolbachia〈/em〉 infection). To this aim, we assayed risk-taking in familiar vs. unfamiliar environments 30 times along 38 days and applied double modelling statistical technique to handle the complex hierarchical structure for both individual-specific trait means and variances. We found that there are significant among-individual differences not only in mean risk-taking behaviour but also in environment- and time-induced behavioural plasticity and residual variation. 〈em〉Wolbachia〈/em〉-infected individuals took less risk than healthy conspecifics; in addition, individuals became more risk-averse with time. Residual variation decreased with time, and individuals expressed higher residual variation in the unfamiliar environment. Further, sensitization was stronger in females and in larger individuals in general. Our results suggest that among-individual variation, behavioural plasticity and residual variation are all (i) biologically relevant components of an individual’s behavioural strategy and (ii) responsive to changes in environment or labile state variables. We propose pill bugs as promising models for personality research due to the relative ease of getting repeated behavioural measurements.〈/p〉
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    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
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  • 62
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉In this paper, we present a family of new mixed finite element methods for linear elasticity for both spatial dimensions 〈span〉 〈span〉\(n=2,3\)〈/span〉 〈/span〉, which yields a conforming and strongly symmetric approximation for stress. Applying 〈span〉 〈span〉\(\mathcal {P}_{k+1}-\mathcal {P}_k\)〈/span〉 〈/span〉 as the local approximation for the stress and displacement, the mixed methods achieve the optimal order of convergence for both the stress and displacement when 〈span〉 〈span〉\(k \ge n\)〈/span〉 〈/span〉. For the lower order case 〈span〉 〈span〉\((n-2\le k〈n)\)〈/span〉 〈/span〉, the stability and convergence still hold on some special grids. The proposed mixed methods are efficiently implemented by hybridization, which imposes the inter-element normal continuity of the stress by a Lagrange multiplier. Then, we develop and analyze multilevel solvers for the Schur complement of the hybridized system in the two dimensional case. Provided that no nearly singular vertex on the grids, the proposed solvers are proved to be uniformly convergent with respect to both the grid size and Poisson’s ratio. Numerical experiments are provided to validate our theoretical results.〈/p〉
    Print ISSN: 0029-599X
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    Topics: Mathematics
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  • 63
    Publication Date: 2019
    Description: The United States healthcare system produces an enormous volume of data with a vast number of financial transactions generated by physicians administering healthcare services. This makes healthcare fraud diffi...
    Electronic ISSN: 2196-1115
    Topics: Computer Science
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  • 64
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    Springer
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉The discontinuous Galerkin (dG) methodology provides a hierarchy of time discretization schemes for evolutionary problems such as elastoplasticity with the Prandtl-Reuß  flow rule. A dG time discretization has been proposed for a variational inequality in the context of rate-independent inelastic material behaviour in Alberty and Carstensen in (CMME 191:4949–4968, 〈span〉2002〈/span〉) with the help of duality in convex analysis to justify certain jump terms. This paper establishes the first a priori error analysis for the dG(1) scheme with discontinuous piecewise linear polynomials in the temporal and lowest-order finite elements for the spatial discretization. Compared to a generalized mid-point rule, the dG(1) formulation distributes the action of the material law in the form of the variational inequality in time and so it introduces an error in the material law. This may result in a suboptimal convergence rate for the dG(1) scheme and this paper shows that the stress error in the 〈span〉 〈span〉\(L^\infty (L^2)\)〈/span〉 〈/span〉 norm is merely 〈span〉 〈span〉\(O(h+k^{3/2})\)〈/span〉 〈/span〉 based on a seemingly sharp error analysis. The numerical investigation for a benchmark problem with known analytic solution provides empirical evidence of a higher convergence rate of the dG(1) scheme compared to dG(0).〈/p〉
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  • 65
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉We consider commutator-free exponential integrators as put forward in Alverman and Fehske (J Comput Phys 230:5930–5956, 〈span〉2011〈/span〉). For parabolic problems, it is important for the well-definedness that such an integrator satisfies a positivity condition such that essentially it only proceeds forward in time. We prove that this requirement implies maximal convergence order of four for real coefficients, which has been conjectured earlier by other authors.〈/p〉
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  • 66
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉Several important problems in partial differential equations can be formulated as integral equations. Often the integral operator defines the solution of an elliptic problem with specified jump conditions at an interface. In principle the integral equation can be solved by replacing the integral operator with a finite difference calculation on a regular grid. A practical method of this type has been developed by the second author. In this paper we prove the validity of a simplified version of this method for the Dirichlet problem in a general domain in 〈span〉 〈span〉\({\mathbb {R}}^2\)〈/span〉 〈/span〉 or 〈span〉 〈span〉\({\mathbb {R}}^3\)〈/span〉 〈/span〉. Given a boundary value, we solve for a discrete version of the density of the double layer potential using a low order interface method. It produces the Shortley–Weller solution for the unknown harmonic function with accuracy 〈span〉 〈span〉\(O(h^2)\)〈/span〉 〈/span〉. We prove the unique solvability for the density, with bounds in norms based on the energy or Dirichlet norm, using techniques which mimic those of exact potentials. The analysis reveals that this crude method maintains much of the mathematical structure of the classical integral equation. Examples are included.〈/p〉
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  • 67
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉Numerical approximation of a stochastic partial integro-differential equation driven by a space-time white noise is studied by truncating a series representation of the noise, with finite element method for spatial discretization and convolution quadrature for time discretization. Sharp-order convergence of the numerical solutions is proved up to a logarithmic factor. Numerical examples are provided to support the theoretical analysis.〈/p〉
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  • 68
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉The objective of this article is to characterize the entropy and 〈span〉 〈span〉\(L_2\)〈/span〉 〈/span〉 stability of several representative discontinuous Galerkin (DG) methods for solving the compressible Euler equations. Towards this end, three DG methods are constructed: one DG method with entropy variables as its unknowns, and two DG methods with conservative variables as their unknowns. These methods are employed in order to discretize the compressible Euler equations in space. Thereafter, the resulting semi-discrete formulations are analyzed, and the entropy and 〈span〉 〈span〉\(L_2\)〈/span〉 〈/span〉 stability characteristics are evaluated. It is shown that the semi-discrete formulation of the DG method with entropy variables is entropy and 〈span〉 〈span〉\(L_2\)〈/span〉 〈/span〉 stable. Furthermore, it is shown that the semi-discrete formulations of the DG methods with conservative variables are only guaranteed to be entropy and 〈span〉 〈span〉\(L_2\)〈/span〉 〈/span〉 stable under the following assumptions: the entropy projection errors vanish, or the terms containing the entropy projection errors are non-positive. Thereafter, the semi-discrete formulation with entropy variables, and one of the semi-discrete formulations with conservative variables, are discretized in time with an ‘algebraically stable’ Runge–Kutta (RK) scheme. The resulting formulations are fully-discrete and can be immediately applied to practical problems. In this article, they are employed to simulate a vortex propagating for long distances. It is shown that temporal stability is maintained by the DG method with entropy variables, but the DG method with conservative variables exhibits instability.〈/p〉
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  • 69
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉This paper introduces an explicit residual-based a posteriori error analysis for the symmetric mixed finite element method in linear elasticity after Arnold–Winther with pointwise symmetric and 〈span〉 〈span〉\(H({\text {div}})\)〈/span〉 〈/span〉-conforming stress approximation. The residual-based a posteriori error estimator of this paper is reliable and efficient and truly explicit in that it solely depends on the symmetric stress and does neither need any additional information of some skew symmetric part of the gradient nor any efficient approximation thereof. Hence, it is straightforward to implement an adaptive mesh-refining algorithm. Numerical experiments verify the proven reliability and efficiency of the new a posteriori error estimator and illustrate the improved convergence rate in comparison to uniform mesh-refining. A higher convergence rate for piecewise affine data is observed in the 〈span〉 〈span〉\(L^2\)〈/span〉 〈/span〉 stress error and reproduced in non-smooth situations by the adaptive mesh-refining strategy.〈/p〉
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  • 70
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉In this article we present and analyse new multilevel adaptations of classical stochastic approximation algorithms for the computation of a zero of a function 〈span〉 〈span〉\(f:D \rightarrow {{\mathbb {R}}}^d\)〈/span〉 〈/span〉 defined on a convex domain 〈span〉 〈span〉\(D\subset {{\mathbb {R}}}^d\)〈/span〉 〈/span〉, which is given as a parameterised family of expectations. The analysis of the error and the computational cost of our method is based on similar assumptions as used in Giles (Oper Res 56(3):607–617, 〈span〉2008〈/span〉) for the computation of a single expectation. Additionally, we essentially only require that 〈em〉f〈/em〉 satisfies a classical contraction property from stochastic approximation theory. Under these assumptions we establish error bounds in 〈em〉p〈/em〉th mean for our multilevel Robbins–Monro and Polyak–Ruppert schemes that decay in the computational time as fast as the classical error bounds for multilevel Monte Carlo approximations of single expectations known from Giles (Oper Res 56(3):607–617, 〈span〉2008〈/span〉). Our approach is universal in the sense that having multilevel implementations for a particular application at hand it is straightforward to implement the corresponding stochastic approximation algorithm.〈/p〉
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  • 71
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    Springer
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉Let 〈span〉 〈span〉\(a(z)=\sum _{i\in {\mathbb {Z}}}a_iz^i\)〈/span〉 〈/span〉 be a complex valued function defined for 〈span〉 〈span〉\(|z|=1\)〈/span〉 〈/span〉, such that 〈span〉 〈span〉\(\sum _{i\in {\mathbb {Z}}}|a_i|〈\infty \)〈/span〉 〈/span〉; define 〈span〉 〈span〉\(T(a)=(t_{i,j})_{i,j\in {\mathbb {Z}}^+}, t_{i,j}=a_{j-i}\)〈/span〉 〈/span〉 for 〈span〉 〈span〉\(i,j\in {\mathbb {Z}}^+\)〈/span〉 〈/span〉, the semi-infinite Toeplitz matrix associated with the symbol 〈em〉a〈/em〉(〈em〉z〈/em〉); let 〈span〉 〈span〉\(E=(e_{i,j})_{i,j\in {\mathbb {Z}}^+}\)〈/span〉 〈/span〉 be a compact operator in 〈span〉 〈span〉\(\ell ^p\)〈/span〉 〈/span〉, with 〈span〉 〈span〉\(1\le p\le \infty .\)〈/span〉 〈/span〉 A semi-infinite matrix of the kind 〈span〉 〈span〉\(A=T(a)+E\)〈/span〉 〈/span〉 is said quasi-Toeplitz (QT). The problem of the computation of 〈span〉 〈span〉\(\exp (A)\)〈/span〉 〈/span〉 or 〈span〉 〈span〉\(\exp (A)v\)〈/span〉 〈/span〉, with 〈em〉A〈/em〉 quasi-Toeplitz and 〈em〉v〈/em〉 a vector, arises in many applications. We prove that the exponential of a QT-matrix 〈em〉A〈/em〉 is QT, that is, 〈span〉 〈span〉\(\exp (A) = T(\exp (a))+F\)〈/span〉 〈/span〉 where 〈em〉F〈/em〉 is a compact operator in 〈span〉 〈span〉\(\ell ^p\)〈/span〉 〈/span〉. This property allows the design of an algorithm for computing 〈span〉 〈span〉\(\exp (A)\)〈/span〉 〈/span〉 and 〈span〉 〈span〉\(\exp (A)v\)〈/span〉 〈/span〉 up to any precision. The case of families of 〈span〉 〈span〉\(n\times n\)〈/span〉 〈/span〉 matrices obtained by truncating infinite QT-matrices to finite size is also considered. Numerical experiments show the effectiveness of this approach.〈/p〉
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  • 72
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉We propose an efficient algorithm for the approximation of fractional integrals by using Runge–Kutta based convolution quadrature. The algorithm is based on a novel integral representation of the convolution weights and a special quadrature for it. The resulting method is easy to implement, allows for high order, relies on rigorous error estimates and its performance in terms of memory and computational cost is among the best to date. Several numerical results illustrate the method and we describe how to apply the new algorithm to solve fractional diffusion equations. For a class of fractional diffusion equations we give the error analysis of the full space-time discretization obtained by coupling the FEM method in space with Runge–Kutta based convolution quadrature in time.〈/p〉
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  • 73
    Publication Date: 2019
    Description: 〈p〉The article Wave Polarization Analyzed by Singular Value Decomposition of the Spectral Matrix in the Presence of Noise, written by Ulrich Taubenschuss and Ondřej Santolík, was originally published electronically on the publisher’s internet portal (currently SpringerLink) on 19 August 2018 without open access.〈/p〉
    Print ISSN: 0169-3298
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    Topics: Geosciences , Physics
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  • 74
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉National greenhouse gas inventories often use variations of the 〈em〉gain〈/em〉–〈em〉loss〈/em〉 approach whereby emissions are estimated as the products of estimates of areas of land-use change characterized as 〈em〉activity data〈/em〉 and estimates of emissions per unit area characterized as 〈em〉emission factors〈/em〉. Although the term 〈em〉emissions〈/em〉 is often intuitively understood to mean release of greenhouse gases from terrestrial sources to the atmosphere, in fact, emission factors can also be negative, meaning removal of the gases from the atmosphere to terrestrial sinks. For remote and inaccessible forests for which ground sampling is difficult if not impossible, emission factors may be based on map-based estimates of biomass or biomass change obtained from regional maps. For the special case of complete deforestation, the emission factor for the aboveground biomass pool is simply mean aboveground, live-tree, biomass per unit area prior to the deforestation. If biomass maps are used for these purposes, estimates must still comply with the first IPCC good practice guideline regarding accuracy relative to the true value and the second guideline regarding uncertainty. Accuracy assessment for a map-based estimate entails comparison of the estimate to a second estimate obtained using independent reference data. Assuming ground sampling is not feasible, a map of greater quality than the regional map may be considered as a source of reference data where greater quality connotes attributes such as finer resolution and/or greater accuracy. For a local, sub-regional study area in Minnesota in the USA, the accuracy of an estimate of mean aboveground, live-tree biomass per unit area (AGB, Mg/ha) obtained from a coarser resolution, regional, MODIS-based biomass map was assessed using reference data sampled from a finer resolution, local, airborne laser scanning (ALS)-based biomass map. The rationale for a local assessment of a regional map is that, although assessment of a regional map would be difficult for the entire extent of the map, it can likely be assessed for multiple local sub-regions in which case expected local regional accuracy for the entire map can perhaps be inferred. For this study, the local assessment was in the form of a test of the hypothesis that the local sub-regional estimate from the regional map did not deviate from the local true value. A hybrid approach to inference was used whereby design-based inferential techniques were used to estimate uncertainty due to sampling from the finer resolution map, and model-based inferential techniques were used to estimate uncertainty resulting from using the finer resolution map unit values which were subject to prediction error as reference data. The test revealed no statistically significant difference between the MODIS-based and ALS-based map estimates, thereby indicating that for the local sub-region, the regional, MODIS-based estimate complied with the first IPCC good practice guideline for accuracy.〈/p〉
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  • 75
    Publication Date: 2019
    Description: 〈h3〉Abstract〈/h3〉 〈p〉Electric currents flowing in the global electric circuit are closed by ionospheric currents. A model for the distribution of the ionospheric potential which drives these currents is constructed. Only the internal electric fields and currents generated by thunderstorms are studied, and without any magnetospheric current sources or generators. The atmospheric conductivity profiles with altitude are empirically determined, and the topography of the Earth’s surface is taken into account. A two-dimensional approximation of the ionospheric conductor is based on high conductivities along the geomagnetic field; the Pedersen and Hall conductivity distributions are calculated using empirical models. The values of the potential in the E- and F-layers of the ionosphere are not varied along a magnetic field line in such a model and the electric field strength is only slightly varied because the segments of neighboring magnetic field lines are not strictly parallel. It is shown that the longitudinal and latitudinal components of the ionospheric electric field of the global electric circuit under typical conditions for July, under high solar activity, at the considered point in time, 19:00 UT, do not exceed 〈span〉 〈span〉\(9\,\upmu {\text{V/m}}\)〈/span〉 〈/span〉, and in the sunlit ionosphere they are less than 〈span〉 〈span〉\(2\,\upmu {\text{V/m}}\)〈/span〉 〈/span〉. The calculated maximum potential difference in the E- and F-layers is 〈span〉 〈span〉\(42\,{\text{V}}\)〈/span〉 〈/span〉; the maximum of the potential occurs above African thunderstorms that are near the terminator at that time. A weak local maximum also exists above the thunderstorm area in Central America. The minimum potential occurs near midnight above the Himalayas. The potential has identical values at ionospheric conjugate points. The voltage increases to 〈span〉 〈span〉\(55\,{\text{V}}\)〈/span〉 〈/span〉 at 23:00 UT and up to 〈span〉 〈span〉\(72\,{\text{V}}\)〈/span〉 〈/span〉 at 06:00 UT, when local midnight comes, respectively, for the African and Central American thunderstorm areas. These voltages are about twice as large at solar minimum. With our more realistic ionospheric model, the electric fields are an order of magnitude smaller than those found in the well-known model of Roble and Hays (J Geophys Res 84(A12):7247–7256, 〈span〉1979〈/span〉). Our simulations quantitatively support the traditional presentation of the ionosphere as an ideal conductor in models of the global electric circuit, so that our model can be used to investigate UT variations of the global electric circuit.〈/p〉
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