WorldWideScience

Sample records for climatically driven fluctuations

  1. Spectral decomposition of regulatory thresholds for climate-driven fluctuations in hydro- and wind power availability

    Science.gov (United States)

    Wörman, A.; Bottacin-Busolin, A.; Zmijewski, N.; Riml, J.

    2017-08-01

    Climate-driven fluctuations in the runoff and potential energy of surface water are generally large in comparison to the capacity of hydropower regulation, particularly when hydropower is used to balance the electricity production from covarying renewable energy sources such as wind power. To define the bounds of reservoir storage capacity, we introduce a dedicated reservoir volume that aggregates the storage capacity of several reservoirs to handle runoff from specific watersheds. We show how the storage bounds can be related to a spectrum of the climate-driven modes of variability in water availability and to the covariation between water and wind availability. A regional case study of the entire hydropower system in Sweden indicates that the longest regulation period possible to consider spans from a few days of individual subwatersheds up to several years, with an average limit of a couple of months. Watershed damping of the runoff substantially increases the longest considered regulation period and capacity. The high covariance found between the potential energy of the surface water and wind energy significantly reduces the longest considered regulation period when hydropower is used to balance the fluctuating wind power.

  2. Surface area changes of Himalayan ponds as a proxy of hydrological climate-driven fluctuations

    Science.gov (United States)

    Salerno, Franco; Thakuri, Sudeep; Guyennon, Nicolas; Viviano, Gaetano; Tartari, Gianni

    2016-04-01

    The meteorological measurements at high-elevations of the Himalayan range are scarce due to the harsh conditions of these environments which limit the suitable maintenance of weather stations. As a consequence, the meager knowledge on how the climate is changed in the last decades at Himalayan high-elevations sets a serious limit upon the interpretation of relationships between causes and recent observed effects on the cryosphere. Although the glaciers masses reduction in Himalaya is currently sufficiently well described, how changes in climate drivers (precipitation and temperature) have influenced the melting and shrinkage processes are less clear. Consequently, the uncertainty related to the recent past amplifies when future forecasts are done, both for climate and impacts. In this context, a substantial body of research has already demonstrated the high sensitivity of lakes and ponds to climate. Some climate-related signals are highly visible and easily measurable in lakes. For example, climate-driven fluctuations in lake surface area have been observed in many remote sites. On interior Tibetan Plateau the lake growth since the late 1990s is mainly attributed to increased regional precipitation and weakened evaporation. Differently, other authors attribute at the observed increases of lake surfaces at the enhanced glacier melting. In our opinion these divergences found in literature are due to the type of glacial lakes considered in the study and in particular their relationship with glaciers. In general, in Himalaya three types of glacial lakes can be distinguished: (i) lakes that are not directly connected with glaciers, but that may have a glacier located in their basin (unconnected glacial lakes); (ii) supraglacial lakes, which develop on the surface of the glacier downstream; or (iii) proglacial lakes, which are moraine-dammed lakes that are in contact with the glacier front. Some of these lakes store large quantities of water and are susceptible to GLOFs

  3. Sensitivity of seafloor bathymetry to climate-driven fluctuations in mid-ocean ridge magma supply.

    Science.gov (United States)

    Olive, J-A; Behn, M D; Ito, G; Buck, W R; Escartín, J; Howell, S

    2015-10-16

    Recent studies have proposed that the bathymetric fabric of the seafloor formed at mid-ocean ridges records rapid (23,000 to 100,000 years) fluctuations in ridge magma supply caused by sealevel changes that modulate melt production in the underlying mantle. Using quantitative models of faulting and magma emplacement, we demonstrate that, in fact, seafloor-shaping processes act as a low-pass filter on variations in magma supply, strongly damping fluctuations shorter than about 100,000 years. We show that the systematic decrease in dominant seafloor wavelengths with increasing spreading rate is best explained by a model of fault growth and abandonment under a steady magma input. This provides a robust framework for deciphering the footprint of mantle melting in the fabric of abyssal hills, the most common topographic feature on Earth. Copyright © 2015, American Association for the Advancement of Science.

  4. Recent, climate-driven river incision rate fluctuations in the Mercantour crystalline massif, southern French Alps

    Science.gov (United States)

    Petit, C.; Goren, L.; Rolland, Y.; Bourlès, D.; Braucher, R.; Saillard, M.; Cassol, D.

    2017-06-01

    We present a new geomorphological analysis of the Tinée River tributaries in the southern French Alps based on numerical inverse and forward modelling of their longitudinal profiles. We model their relative uplift history with respect to the main channel, hence the incision rate history of this channel. Inverse models show that all tributaries have consistent incision rate histories with alternating high and low values. A comparison with global temperature curves shows that these variations correlate with quaternary climate changes. We suggest that during warm periods, a wave of regressive erosion propagates in the Tinée River, while its tributaries deeply incise their substratum to catch up with the falling base-level. We also show that the post 140 ka history of this landscape evolution is dominated by fluvial incision. We then perform forward models of river incision and simulate the incision of the Tinée River system over a time span of 600 ka. This model allows us to extract time and space incision rate variations of the Tinée River. With a background of a few mm.yr-1, incision rate can increase up to more than 1 cm yr-1 during short periods of time due to climatic oscillations. This result is compatible with published cosmogenic nuclide based dating, which evidenced incision rates from 0.2 to 24 mm yr-1. The part of the channel located between 12 and 20 km downstream from the source has undergone several periods of rapid incision rates, which could explain the steep hillslopes and the triggering of a landslide ∼10 ka ago.

  5. Investigation of the climate-driven periodicity of shallow groundwater level fluctuations in a Central-Eastern European agricultural region

    Science.gov (United States)

    Garamhegyi, Tamás; Kovács, József; Pongrácz, Rita; Tanos, Péter; Hatvani, István Gábor

    2018-05-01

    The distribution and amount of groundwater, a crucial source of Earth's drinking and irrigation water, is changing due to climate-change effects. Therefore, it is important to understand groundwater behavior in extreme scenarios, e.g. drought. Shallow groundwater (SGW) level fluctuation under natural conditions displays periodic behavior, i.e. seasonal variation. Thus, the study aims to investigate (1) the periodic behavior of the SGW level time series of an agriculturally important and drought-sensitive region in Central-Eastern Europe - the Carpathian Basin, in the north-eastern part of the Great Hungarian Plain, and (2) its relationship to the European atmospheric pressure action centers. Data from 216 SGW wells were studied using wavelet spectrum analysis and wavelet coherence analyses for 1961-2010. Locally, a clear relationship exists between the absence of annual periodic behavior in the SGW level and the periodicity of droughts, as indicated by the self-calibrating Palmer Drought Severity Index and the Aridity Index. During the non-periodic intervals, significant drops in groundwater levels (average 0.5 m) were recorded in 89% of the wells. This result links the meteorological variables to the periodic behavior of SGW, and consequently, drought. On a regional scale, Mediterranean cyclones from the Gulf of Genoa (northwest Italy) were found to be a driving factor in the 8-yr periodic behavior of the SGW wells. The research documents an important link between SGW levels and local/regional climate variables or indices, thereby facilitating the necessary adaptation strategies on national and/or regional scales, as these must take into account the predictions of drought-related climatic conditions.

  6. Mesoscopic fluctuations in biharmonically driven flux qubits

    Science.gov (United States)

    Ferrón, Alejandro; Domínguez, Daniel; Sánchez, María José

    2017-01-01

    We investigate flux qubits driven by a biharmonic magnetic signal, with a phase lag that acts as an effective time reversal broken parameter. The driving induced transition rate between the ground and the excited state of the flux qubit can be thought of as an effective transmittance, profiting from a direct analogy between interference effects at avoided level crossings and scattering events in disordered electronic systems. For time scales prior to full relaxation, but large compared to the decoherence time, this characteristic rate has been accessed experimentally by Gustavsson et al. [Phys. Rev. Lett. 110, 016603 (2013)], 10.1103/PhysRevLett.110.016603 and its sensitivity with both the phase lag and the dc flux detuning explored. In this way, signatures of universal conductance fluctuationslike effects have been analyzed and compared with predictions from a phenomenological model that only accounts for decoherence, as a classical noise. Here we go beyond the classical noise model and solve the full dynamics of the driven flux qubit in contact with a quantum bath employing the Floquet-Born-Markov master equation. Within this formalism, the computed relaxation and decoherence rates turn out to be strongly dependent on both the phase lag and the dc flux detuning. Consequently, the associated pattern of fluctuations in the characteristic rates display important differences with those obtained within the mentioned phenomenological model. In particular, we demonstrate the weak localizationlike effect in the average values of the relaxation rate. Our predictions can be tested for accessible but longer time scales than the current experimental times.

  7. Climate-driven polar motion

    Science.gov (United States)

    Celaya, Michael A.; Wahr, John M.; Bryan, Frank O.

    1999-06-01

    The output of a coupled climate system model provides a synthetic climate record with temporal and spatial coverage not attainable with observational data, allowing evaluation of climatic excitation of polar motion on timescales of months to decades. Analysis of the geodetically inferred Chandler excitation power shows that it has fluctuated by up to 90% since 1900 and that it has characteristics representative of a stationary Gaussian process. Our model-predicted climate excitation of the Chandler wobble also exhibits variable power comparable to the observed. Ocean currents and bottom pressure shifts acting together can alone drive the 14-month wobble. The same is true of the excitation generated by the combined effects of barometric pressure and winds. The oceanic and atmospheric contributions are this large because of a relatively high degree of constructive interference between seafloor pressure and currents and between atmospheric pressure and winds. In contrast, excitation by the redistribution of water on land appears largely insignificant. Not surprisingly, the full climate effect is even more capable of driving the wobble than the effects of the oceans or atmosphere alone are. Our match to the observed annual excitation is also improved, by about 17%, over previous estimates made with historical climate data. Efforts to explain the 30-year Markowitz wobble meet with less success. Even so, at periods ranging from months to decades, excitation generated by a model of a coupled climate system makes a close approximation to the amplitude of what is geodetically observed.

  8. Fluctuation-Driven Neural Dynamics Reproduce Drosophila Locomotor Patterns.

    Directory of Open Access Journals (Sweden)

    Andrea Maesani

    2015-11-01

    Full Text Available The neural mechanisms determining the timing of even simple actions, such as when to walk or rest, are largely mysterious. One intriguing, but untested, hypothesis posits a role for ongoing activity fluctuations in neurons of central action selection circuits that drive animal behavior from moment to moment. To examine how fluctuating activity can contribute to action timing, we paired high-resolution measurements of freely walking Drosophila melanogaster with data-driven neural network modeling and dynamical systems analysis. We generated fluctuation-driven network models whose outputs-locomotor bouts-matched those measured from sensory-deprived Drosophila. From these models, we identified those that could also reproduce a second, unrelated dataset: the complex time-course of odor-evoked walking for genetically diverse Drosophila strains. Dynamical models that best reproduced both Drosophila basal and odor-evoked locomotor patterns exhibited specific characteristics. First, ongoing fluctuations were required. In a stochastic resonance-like manner, these fluctuations allowed neural activity to escape stable equilibria and to exceed a threshold for locomotion. Second, odor-induced shifts of equilibria in these models caused a depression in locomotor frequency following olfactory stimulation. Our models predict that activity fluctuations in action selection circuits cause behavioral output to more closely match sensory drive and may therefore enhance navigation in complex sensory environments. Together these data reveal how simple neural dynamics, when coupled with activity fluctuations, can give rise to complex patterns of animal behavior.

  9. Orbital Noise in the Earth System and Climate Fluctuations

    Science.gov (United States)

    Liu, Han-Shou; Smith, David E. (Technical Monitor)

    2001-01-01

    Frequency noise in the variations of the Earth's obliquity (tilt) can modulate the insolation signal for climate change. Including this frequency noise effect on the incoming solar radiation, we have applied an energy balance climate model to calculate the climate fluctuations for the past one million years. Model simulation results are in good agreement with the geologically observed paleoclimate data. We conclude that orbital noise in the Earth system may be the major cause of the climate fluctuation cycles.

  10. Profit-driven and demand-driven investment growth and fluctuations in different accumulation regimes

    OpenAIRE

    Giovanni Dosi; Mauro Sodini; Maria Enrica Virgillito

    2013-01-01

    The main task of this work is to develope a model able to encompass, at the same time, Keynesian, demand-driven, and Marxian, profit-driven determinants of fluctuations. Our starting point is the Goodwin's model (1967), rephrased in discrete time and extended by means of a coupled dynamics structure. The model entails the combined interaction of a demand effect, which resembles a rudimentary first approximation to an accelerator, and of a hysteresis effect in wage formation in turn affecting ...

  11. Redistribution of phase fluctuations in a periodically driven cuprate superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Hoeppner, Robert; Zhu, Beilei; Rexin, Tobias [Zentrum fuer Optische Quantentechnologien und Institut fuer Laserphysik, Hamburg (Germany); Mathey, Ludwig [Zentrum fuer Optische Quantentechnologien und Institut fuer Laserphysik, Hamburg (Germany); The Hamburg Centre for Ultrafast Imaging, Hamburg (Germany); Cavalleri, Andrea [Max Planck Institute for the Structure and Dynamics of Matter, Hamburg (Germany); Department of Physics, Oxford University, Clarendon Laboratory, Parks Road, Oxford (United Kingdom)

    2015-07-01

    We study the thermally fluctuating state of a bi-layer cuprate superconductor under the periodic action of a staggered field oscillating at optical frequencies. This analysis distills essential elements of the recently discovered phenomenon of light enhanced coherence in YBCO, which was achieved by periodically driving infrared active apical oxygen distortions. The effect of a staggered periodic perturbation is studied using a Langevin description of driven, coupled Josephson junctions, which represent two neighboring pairs of layers and their two plasmons. We demonstrate that the external driving leads to a suppression of phase fluctuations of the low-energy plasmon, an effect which is amplified via the resonance of the high energy plasmon, with a striking suppression of the low-energy fluctuations, as visible in the power spectrum. We also find that this effect acts onto the in-plane fluctuations, which are reduced on long length scales and we discuss the behavior of vortices in the ab-planes and across the weakly coupled junctions.

  12. Tertiary climatic fluctuations and methods of analysis of tertiary floras

    Science.gov (United States)

    Wolfe, J.A.

    1971-01-01

    On theoretical grounds, an analysis of the physiognomy of a Tertiary leaf assemblage is more direct and reliable than a circuitous floristic analysis in assigning thermal regimes to fossil assemblages. Using primarily foliar physiognomy and secondarily floristic composition, it can be shown that: (1) some middle latitude Tertiary assemblages probably lived under meteoroligically tropical climates; (2) a major and rapid climatic deterioration occurred in the Oligocene; and (3) a major climatic fluctuation probably occurred in the Late Eocene. These analyses thus substantiate the conclusions of several other paleobotanists regarding climatic fluctuations. Recent criticisms of these analyses are shown to be invalid and to be based largely on misinterpretations. ?? 1971.

  13. Fluctuating hydrodynamics, current fluctuations, and hyperuniformity in boundary-driven open quantum chains.

    Science.gov (United States)

    Carollo, Federico; Garrahan, Juan P; Lesanovsky, Igor; Pérez-Espigares, Carlos

    2017-11-01

    We consider a class of either fermionic or bosonic noninteracting open quantum chains driven by dissipative interactions at the boundaries and study the interplay of coherent transport and dissipative processes, such as bulk dephasing and diffusion. Starting from the microscopic formulation, we show that the dynamics on large scales can be described in terms of fluctuating hydrodynamics. This is an important simplification as it allows us to apply the methods of macroscopic fluctuation theory to compute the large deviation (LD) statistics of time-integrated currents. In particular, this permits us to show that fermionic open chains display a third-order dynamical phase transition in LD functions. We show that this transition is manifested in a singular change in the structure of trajectories: while typical trajectories are diffusive, rare trajectories associated with atypical currents are ballistic and hyperuniform in their spatial structure. We confirm these results by numerically simulating ensembles of rare trajectories via the cloning method, and by exact numerical diagonalization of the microscopic quantum generator.

  14. Radiation Belt Transport Driven by Solar Wind Dynamic Pressure Fluctuations

    Science.gov (United States)

    Kress, B. T.; Hudson, M. K.; Ukhorskiy, A. Y.; Mueller, H.

    2012-12-01

    The creation of the Earth's outer zone radiation belts is attributed to earthward transport and adiabatic acceleration of electrons by drift-resonant interactions with electromagnetic fluctuations in the magnetosphere. Three types of radial transport driven by solar wind dynamic pressure fluctuations that have been identified are: (1) radial diffusion [Falthammer, 1965], (2) significant changes in the phase space density radial profile due to a single or few ULF drift-resonant interactions [Ukhorskiy et al., 2006; Degeling et al., 2008], and (3) shock associated injections of radiation belt electrons occurring in less than a drift period [Li et al., 1993]. A progress report will be given on work to fully characterize different forms of radial transport and their effect on the Earth's radiation belts. The work is being carried out by computing test-particle trajectories in electric and magnetic fields from a simple analytic ULF field model and from global MHD simulations of the magnetosphere. Degeling, A. W., L. G. Ozeke, R. Rankin, I. R. Mann, and K. Kabin (2008), Drift resonant generation of peaked relativistic electron distributions by Pc 5 ULF waves, textit{J. Geophys. Res., 113}, A02208, doi:10.1029/2007JA012411. Fälthammar, C.-G. (1965), Effects of Time-Dependent Electric Fields on Geomagnetically Trapped Radiation, J. Geophys. Res., 70(11), 2503-2516, doi:10.1029/JZ070i011p02503. Li, X., I. Roth, M. Temerin, J. R. Wygant, M. K. Hudson, and J. B. Blake (1993), Simulation of the prompt energization and transport of radiation belt particles during the March 24, 1991 SSC, textit{Geophys. Res. Lett., 20}(22), 2423-2426, doi:10.1029/93GL02701. Ukhorskiy, A. Y., B. J. Anderson, K. Takahashi, and N. A. Tsyganenko (2006), Impact of ULF oscillations in solar wind dynamic pressure on the outer radiation belt electrons, textit{Geophys. Res. Lett., 33}(6), L06111, doi:10.1029/2005GL024380.

  15. Energy fluctuations in a biharmonically driven nonlinear system

    Indian Academy of Sciences (India)

    analyse the nature of work and heat fluctuations and show that the steady state fluctuation .... The above equation is the statement of the first law of thermodynamics and ..... One of the authors (AMJ) thanks DST, India for financial support.

  16. The effect of climate fluctuation on chimpanzee birth sex ratio.

    Directory of Open Access Journals (Sweden)

    Hjalmar S Kühl

    Full Text Available Climate and weather conditions, such as the North Atlantic Oscillation, precipitation and temperature influence the birth sex ratio (BSR of various higher latitude species, including deer, elephant seals or northern human populations. Although, tropical regions show only little variation in temperature, climate and weather conditions can fluctuate with consequences for phenology and food resource availability. Here, we evaluate, whether the BSR of chimpanzees, inhabiting African tropical forests, is affected by climate fluctuations as well. Additionally, we evaluate, if variation in consumption of a key food resource with high nutritional value, Coula edulis nuts, is linked to both climate fluctuations and variation in BSR. We use long-term data from two study groups located in Taï National Park, Côte d'Ivoire to assess the influence of local weather conditions and the global climate driver El Niño Southern Oscillation (ENSO on offspring sex. Côte d'Ivoire has experienced considerable climate variation over the last decades, with increasing temperature and declining precipitation. For both groups we find very similar time windows around the month of conception, in which offspring sex is well predicted by ENSO, with more males following low ENSO values, corresponding to periods of high rainfall. Furthermore, we find that the time spent cracking and feeding on Coula nuts is strongly influenced by climate conditions. Although, some of our analysis suggest that a higher proportion of males is born after periods with higher nut consumption frequency, we cannot conclude decisively at this point that nut consumption may influence shifts in BSR. All results combined suggest that also chimpanzees may experience climate related shifts in offspring sex ratios as response to climate fluctuation.

  17. Critical current fluctuation in a microwave-driven Josephson junction

    International Nuclear Information System (INIS)

    Dong Ning; Sun Guozhu; Wang Yiwen; Cao Junyu; Yu Yang; Chen Jian; Kang Lin; Xu Weiwei; Han Siyuan; Wu Peiheng

    2007-01-01

    Josephson junction devices are good candidates for quantum computation. A large energy splitting was observed in the spectroscopy of a superconducting Josephson junction. The presence of the critical current fluctuation near the energy splitting indicated coupling between the junction and a two-level system. Furthermore, we find that this fluctuation is microwave dependent. It only appears at certain microwave frequency. This relation suggested that the decoherence of qubits is influenced by the necessary computing operations

  18. Holocene climatic fluctuations and periodic changes in the Asian southwest monsoon region

    Science.gov (United States)

    Zhang, Wenxiang; Niu, Jie; Ming, Qingzhong; Shi, Zhengtao; Lei, Guoliang; Huang, Linpei; Long, Xian'e.; Chang, Fengqin

    2018-05-01

    Climatic changes in the Asian southwest monsoon (ASWM) during the Holocene have become a topic of recent studies. It is important to understand the patterns and causes of Holocene climatic changes and their relationship with global changes. Based on the climate proxies and wavelet analysis of Lugu Lake in the ASWM region, the climatic fluctuations and periodic changes in the ASWM region during the Holocene have been reconstructed with a high-precision chronology. The results indicate the intensification of ASWM began to increase with Northern Hemisphere low-latitude solar insolation (LSI) and solar activity during the early Holocene, and gradually decreased during the late Holocene, exhibiting an apparent synchrony with numerous records of ASWM region. Meanwhile, an apparent 1000-a quasi-periodic signal is present in the environment proxies, and it demonstrates that the environmental change in the ASWM region has been driven mainly by LSI and solar activity.

  19. The greenhouse effect and natural fluctuations of the climate

    International Nuclear Information System (INIS)

    Schoenwiese, C.D.

    1993-01-01

    There is a straight line connecting the first estimate in 1896 of worldwide climate changes due to the increasing use of fossil sources of energy with the Climate Convention of the United Nations at the 1992 Environmental Summit. Extensive model calculations exist of the 'greenhouse effect', in which the lower atmosphere is heated by manmade emissions of trace gases affecting the climate. However, the anticipated changes are not restricted to the temperature of the air; they affect the climate as a whole worldwide. As a consequence, the German Federal Government, in addition to its ban on CFCs, plans to reduce manmade carbon dioxide emissions by 25 or 30% by 2005. Natural fluctuations of the climate compete with the greenhouse effect: Volcanic and solar effects, but also random variations within the complicated interactions in the climatic system (atmosphere - oceans - ice regions - biosphere - land surface). Mathematical and statistical analyses of the superposition of such climatic mechanisms, which are based on data from observations, result in a risk analysis at a high level of probability. (orig.) [de

  20. Negative velocity fluctuations and non-equilibrium fluctuation relation for a driven high critical current vortex state.

    Science.gov (United States)

    Bag, Biplab; Shaw, Gorky; Banerjee, S S; Majumdar, Sayantan; Sood, A K; Grover, A K

    2017-07-17

    Under the influence of a constant drive the moving vortex state in 2H-NbS 2 superconductor exhibits a negative differential resistance (NDR) transition from a steady flow to an immobile state. This state possesses a high depinning current threshold ([Formula: see text]) with unconventional depinning characteristics. At currents well above [Formula: see text], the moving vortex state exhibits a multimodal velocity distribution which is characteristic of vortex flow instabilities in the NDR regime. However at lower currents which are just above [Formula: see text], the velocity distribution is non-Gaussian with a tail extending to significant negative velocity values. These unusual negative velocity events correspond to vortices drifting opposite to the driving force direction. We show that this distribution obeys the Gallavotti-Cohen Non-Equilibrium Fluctuation Relation (GC-NEFR). Just above [Formula: see text], we also find a high vortex density fluctuating driven state not obeying the conventional GC-NEFR. The GC-NEFR analysis provides a measure of an effective energy scale (E eff ) associated with the driven vortex state. The E eff corresponds to the average energy dissipated by the fluctuating vortex state above [Formula: see text]. We propose the high E eff value corresponds to the onset of high energy dynamic instabilities in this driven vortex state just above [Formula: see text].

  1. Climate-driven changes in water level

    DEFF Research Database (Denmark)

    Hansen, Rikke Bjerring; Olsen, Jesper; Jeppesen, Erik

    2013-01-01

    level rose. Moreover, Nymphaeaceae trichosclereids were abundant during the period of algal enrichment. Cladoceran taxa associated with floating leaved plants or benthic habitats responded in a complex way to changes in water level, but the cladoceran assemblages generally reflected deep lake conditions...... hydrology driven by precipitation. The isotopic, sedimentary and plant macrofossil records suggested that the lake level started to decrease around 8400 cal. yr BP, the decrease accelerating during 8350-8260 before an abrupt increase during 8260-8210. This pattern shows that the climate anomaly started...... rates of cladoceran subfossils and algal pigments, possibly due to increased turbidity and reduced nutrient input during this drier period. Pigment analysis also showed added importance of diatoms and cryptophytes during this climate anomaly, while cyanobacteria became more important when the water...

  2. To what extent can global warming events influence scaling properties of climatic fluctuations in glacial periods?

    Science.gov (United States)

    Alberti, Tommaso; Lepreti, Fabio; Vecchio, Antonio; Carbone, Vincenzo

    2017-04-01

    The Earth's climate is an extremely unstable complex system consisting of nonlinear and still rather unknown interactions among atmosphere, land surface, ice and oceans. The system is mainly driven by solar irradiance, even if internal components as volcanic eruptions and human activities affect the atmospheric composition thus acting as a driver for climate changes. Since the extreme climate variability is the result of a set of phenomena operating from daily to multi-millennial timescales, with different correlation times, a study of the scaling properties of the system can evidence non-trivial persistent structures, internal or external physical processes. Recently, the scaling properties of the paleoclimate changes have been analyzed by distinguish between interglacial and glacial climates [Shao and Ditlevsen, 2016]. The results show that the last glacial record (20-120 kyr BP) presents some elements of multifractality, while the last interglacial period (0-10 kyr BP), say the Holocene period, seems to be characterized by a mono-fractal structure. This is associated to the absence of Dansgaard-Oeschger (DO) events in the interglacial climate that could be the cause for the absence of multifractality. This hypothesis is supported by the analysis of the period between 18 and 27 kyr BP, i.e. during the Last Glacial Period, in which a single DO event have been registred. Through the Empirical Mode Decomposition (EMD) we were able to detect a timescale separation within the Last Glacial Period (20-120 kyr BP) in two main components: a high-frequency component, related to the occurrence of DO events, and a low-frequency one, associated to the cooling/warming phase switch [Alberti et al., 2014]. Here, we investigate the scaling properties of the climate fluctuations within the Last Glacial Period, where abrupt climate changes, characterized by fast increase of temperature usually called Dansgaard-Oeschger (DO) events, have been particularly pronounced. By using the

  3. Understanding Climate Change and Manifestation of its Driven ...

    African Journals Online (AJOL)

    This article examines the nature and manifestation of climate change driven impacts on the agrarian districts of Kongwa and Bahi in the semi arid areas of Dodoma region in Tanzania. A Survey of 398 households in the study area was undertaken to elicit information on the nature and manifestation of climate change driven ...

  4. Holocene and latest Pleistocene climate and glacier fluctuations in Iceland

    Science.gov (United States)

    Geirsdóttir, Áslaug; Miller, Gifford H.; Axford, Yarrow; Ólafsdóttir, Sædís

    2009-10-01

    Multiproxy climate records from Iceland document complex changes in terrestrial climate and glacier fluctuations through the Holocene, revealing some coherent patterns of change as well as significant spatial variability. Most studies on the Last Glacial Maximum and subsequent deglaciation reveal a dynamic Iceland Ice Sheet (IIS) that responded abruptly to changes in ocean currents and sea level. The IIS broke up catastrophically around 15 ka as the Polar Front migrated northward and sea level rose. Indications of regional advance or halt of the glaciers are seen in late Alleröd/early Younger Dryas time and again in PreBoreal time. Due to the apparent rise of relative sea level in Iceland during this time, most sites contain evidence for fluctuating, tidewater glacier termini occupying paleo fjords and bays. The time between the end of the Younger Dryas and the Preboreal was characterized by repeated jökulhlaups that eroded glacial deposits. By 10.3 ka, the main ice sheet was in rapid retreat across the highlands of Iceland. The Holocene thermal maximum (HTM) was reached after 8 ka with land temperatures estimated to be 3 °C higher than the 1961-1990 reference, and net precipitation similar to modern. Such temperatures imply largely ice-free conditions across Iceland in the early to mid-Holocene. Several marine and lacustrine sediment climate proxies record substantial summer temperature depression between 8.5 and 8 ka, but no moraines have been detected from that time. Termination of the HTM and onset of Neoglacial cooling took place sometime after 6 ka with increased glacier activity between 4.5 and 4.0 ka, intensifying between 3.0 and 2.5 ka. Although a distinct warming during the Medieval Warm Period is not dramatically apparent in Icelandic records, the interval from ca AD 0 to 1200 is commonly characterized by relative stability with slow rates of change. The literature most commonly describes Little Ice Age moraines (ca AD 1250-1900) as representing the

  5. Kac limit and thermodynamic characterization of stochastic dynamics driven by Poisson-Kac fluctuations

    Science.gov (United States)

    Giona, Massimiliano; Brasiello, Antonio; Crescitelli, Silvestro

    2017-07-01

    We analyze the thermodynamic properties of stochastic differential equations driven by smooth Poisson-Kac fluctuations, and their convergence, in the Kac limit, towards Wiener-driven Langevin equations. Using a Markovian embedding of the stochastic work variable, it is proved that the Kac-limit convergence implies a Stratonovich formulation of the limit Langevin equations, in accordance with the Wong-Zakai theorem. Exact moment analysis applied to the case of a purely frictional system shows the occurrence of different regimes and crossover phenomena in the parameter space.

  6. Lognormal firing rate distribution reveals prominent fluctuation-driven regime in spinal motor networks

    DEFF Research Database (Denmark)

    Petersen, Peter C.; Berg, Rune W.

    2016-01-01

    fraction that operates within either a ‘mean-driven’ or a ‘fluctuation–driven’ regime. Fluctuation-driven neurons have a ‘supralinear’ input-output curve, which enhances sensitivity, whereas the mean-driven regime reduces sensitivity. We find a rich diversity of firing rates across the neuronal population...... as reflected in a lognormal distribution and demonstrate that half of the neurons spend at least 50 %% of the time in the ‘fluctuation–driven’ regime regardless of behavior. Because of the disparity in input–output properties for these two regimes, this fraction may reflect a fine trade–off between stability...

  7. Edge transport and mode structure of a QCM-like fluctuation driven by the Shoelace antenna

    Science.gov (United States)

    Golfinopoulos, T.; LaBombard, B.; Brunner, D.; Terry, J. L.; Baek, S. G.; Ennever, P.; Edlund, E.; Han, W.; Burke, W. M.; Wolfe, S. M.; Irby, J. H.; Hughes, J. W.; Fitzgerald, E. W.; Granetz, R. S.; Greenwald, M. J.; Leccacorvi, R.; Marmar, E. S.; Pierson, S. Z.; Porkolab, M.; Vieira, R. F.; Wukitch, S. J.; The Alcator C-Mod Team

    2018-05-01

    The Shoelace antenna was built to drive edge fluctuations in the Alcator C-Mod tokamak, matching the wavenumber (k\\perp≈1.5 cm‑1) and frequency (30≲ f ≲ 200 kHz) of the quasi-coherent mode (QCM), which is responsible for regulating transport across the plasma boundary in the steady-state, ELM-free Enhanced D α (EDA) H-mode. Initial experiments in 2012 demonstrated that the antenna drove a resonant response in the edge plasma in steady-state EDA and transient, non-ELMy H-modes, but transport measurements were unavailable. In 2016, the Shoelace antenna was relocated to enable direct measurements of driven transport by a reciprocating Mirror Langmuir Probe, while also making available gas puff imaging and reflectometer data to provide additional radial localization of the driven fluctuation. This new data suggests a  ∼4 mm-wide mode layer centered on or just outside the separatrix. Fluctuations coherent with the antenna produced a radial electron flux with {Γ_e}/{n_e}∼4 m s‑1 in EDA H-mode, smaller than but comparable to the QCM level. But in transient ELM-free H-mode, {Γ_e}/{n_e} was an order of magnitude smaller, and driven fluctuations reduced by a factor of ≳ 3. The driven mode is quantitatively similar to the intrinsic QCM across measured spectral quantities, except that it is more coherent and weaker. This work informs the prospect of achieving control of edge transport by direct coupling to edge modes, as well as the use of such active coupling for diagnostic purposes.

  8. Fluctuation-driven mechanotransduction regulates mitochondrial-network structure and function

    Science.gov (United States)

    Bartolák-Suki, Erzsébet; Imsirovic, Jasmin; Parameswaran, Harikrishnan; Wellman, Tyler J.; Martinez, Nuria; Allen, Philip G.; Frey, Urs; Suki, Béla

    2015-10-01

    Cells can be exposed to irregular mechanical fluctuations, such as those arising from changes in blood pressure. Here, we report that ATP production, assessed through changes in mitochondrial membrane potential, is downregulated in vascular smooth muscle cells in culture exposed to monotonous stretch cycles when compared with cells exposed to a variable cyclic stretch that incorporates physiological levels of cycle-by-cycle variability in stretch amplitude. Variable stretch enhances ATP production by increasing the expression of ATP synthase’s catalytic domain, cytochrome c oxidase and its tyrosine phosphorylation, mitofusins and PGC-1α. Such a fluctuation-driven mechanotransduction mechanism is mediated by motor proteins and by the enhancement of microtubule-, actin- and mitochondrial-network complexity. We also show that, in aorta rings isolated from rats, monotonous stretch downregulates--whereas variable stretch maintains--physiological vessel-wall contractility through mitochondrial ATP production. Our results have implications for ATP-dependent and mechanosensitive intracellular processes.

  9. Fluctuation-Driven Transport in Biological Nanopores. A 3D Poisson–Nernst–Planck Study

    Directory of Open Access Journals (Sweden)

    Marcel Aguilella-Arzo

    2017-03-01

    Full Text Available Living systems display a variety of situations in which non-equilibrium fluctuations couple to certain protein functions yielding astonishing results. Here we study the bacterial channel OmpF under conditions similar to those met in vivo, where acidic resistance mechanisms are known to yield oscillations in the electric potential across the cell membrane. We use a three-dimensional structure-based theoretical approach to assess the possibility of obtaining fluctuation-driven transport. Our calculations show that remarkably high voltages would be necessary to observe the actual transport of ions against their concentration gradient. The reasons behind this are the mild selectivity of this bacterial pore and the relatively low efficiencies of the oscillating signals characteristic of membrane cells (random telegraph noise and thermal noise.

  10. Effect of thermal fluctuations in spin-torque driven magnetization dynamics

    International Nuclear Information System (INIS)

    Bonin, R.; Bertotti, G.; Serpico, C.; Mayergoyz, I.D.; D'Aquino, M.

    2007-01-01

    Nanomagnets with uniaxial symmetry driven by an external field and spin-polarized currents are considered. Anisotropy, applied field, and spin polarization are all aligned along the symmetry axis. Thermal fluctuations are described by adding a Gaussian white noise stochastic term to the Landau-Lifshitz-Gilbert equation for the deterministic dynamics. The corresponding Fokker-Planck equation is derived. It is shown that deterministic dynamics, thermal relaxation, and transition rate between stable states are governed by an effective potential including the effect of current injection

  11. Effect of thermal fluctuations in spin-torque driven magnetization dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Bonin, R. [INRiM, I-10135 Turin (Italy)]. E-mail: bonin@inrim.it; Bertotti, G. [INRiM, I-10135 Turin (Italy); Serpico, C. [Dipartimento di Ingegneria Elettrica, Universita di Napoli ' Federico II' I-80125 Naples (Italy); Mayergoyz, I.D. [Department of Electrical and Computer Engineering, University of Maryland, College Park, MD 20742 (United States); D' Aquino, M. [Dipartimento per le Tecnologie, Universita di Napoli ' Parthenope' , I-80133 Naples (Italy)

    2007-09-15

    Nanomagnets with uniaxial symmetry driven by an external field and spin-polarized currents are considered. Anisotropy, applied field, and spin polarization are all aligned along the symmetry axis. Thermal fluctuations are described by adding a Gaussian white noise stochastic term to the Landau-Lifshitz-Gilbert equation for the deterministic dynamics. The corresponding Fokker-Planck equation is derived. It is shown that deterministic dynamics, thermal relaxation, and transition rate between stable states are governed by an effective potential including the effect of current injection.

  12. Late Holocene vegetation changes in relation with climate fluctuations and human activities in Languedoc (Southern France)

    OpenAIRE

    J. Azuara; N. Combourieu-Nebout; V. Lebreton; F. Mazier; S. D. Müller; L. Dezileau

    2015-01-01

    Holocene climate fluctuations and human activities since the Neolithic have shaped present-day Mediterranean environments. Separating anthropogenic effects from climatic impacts to reconstruct Mediterranean paleoenvironments over the last millennia remains a challenging issue. High resolution pollen analyses were undertaken on two cores from the Palavasian lagoon system (Hérault, southern France). These records allow reconstruction of vegetation dynamics ove...

  13. Holocene climatic fluctuations from Lower Brahmaputra flood plain ...

    Indian Academy of Sciences (India)

    BP which is well-matched with the peak period of the Holocene climatic optimum. However, during ... Warm Period and Little Ice Age (LIA) in this ... The maximum temperature is 30.4 ..... V 2007 Climatic changes during the last 1800 yrs from.

  14. How well do growing season dynamics of photosynthetic capacity correlate with leaf biochemistry and climate fluctuations?

    Science.gov (United States)

    Way, Danielle A; Stinziano, Joseph R; Berghoff, Henry; Oren, Ram

    2017-07-01

    Accurate values of photosynthetic capacity are needed in Earth System Models to predict gross primary productivity. Seasonal changes in photosynthetic capacity in these models are primarily driven by temperature, but recent work has suggested that photoperiod may be a better predictor of seasonal photosynthetic capacity. Using field-grown kudzu (Pueraria lobata (Willd.) Ohwi), a nitrogen-fixing vine species, we took weekly measurements of photosynthetic capacity, leaf nitrogen, and pigment and photosynthetic protein concentrations and correlated these with temperature, irradiance and photoperiod over the growing season. Photosynthetic capacity was more strongly correlated with photoperiod than with temperature or daily irradiance, while the growing season pattern in photosynthetic capacity was uncoupled from changes in leaf nitrogen, chlorophyll and Rubisco. Daily estimates of the maximum carboxylation rate of Rubisco (Vcmax) based on either photoperiod or temperature were correlated in a non-linear manner, but Vcmax estimates from both approaches that also accounted for diurnal temperature fluctuations were similar, indicating that differences between these models depend on the relevant time step. We advocate for considering photoperiod, and not just temperature, when estimating photosynthetic capacity across the year, particularly as climate change alters temperatures but not photoperiod. We also caution that the use of leaf biochemical traits as proxies for estimating photosynthetic capacity may be unreliable when the underlying relationships between proxy leaf traits and photosynthetic capacity are established outside of a seasonal framework. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  15. ARE THE VARIATIONS IN QUASAR OPTICAL FLUX DRIVEN BY THERMAL FLUCTUATIONS?

    International Nuclear Information System (INIS)

    Kelly, Brandon C.; Siemiginowska, Aneta; Bechtold, Jill

    2009-01-01

    We analyze a sample of optical light curves for 100 quasars, 70 of which have black hole mass estimates. Our sample is the largest and broadest used yet for modeling quasar variability. The sources in our sample have z 42 ∼ λ (5100 A) ∼ 46 , and 10 6 ∼ BH /M sun ∼ 10 . We model the light curves as a continuous time stochastic process, providing a natural means of estimating the characteristic timescale and amplitude of quasar variations. We employ a Bayesian approach to estimate the characteristic timescale and amplitude of flux variations; our approach is not affected by biases introduced from discrete sampling effects. We find that the characteristic timescales strongly correlate with black hole mass and luminosity, and are consistent with disk orbital or thermal timescales. In addition, the amplitude of short-timescale variations is significantly anticorrelated with black hole mass and luminosity. We interpret the optical flux fluctuations as resulting from thermal fluctuations that are driven by an underlying stochastic process, such as a turbulent magnetic field. In addition, the intranight variations in optical flux implied by our empirical model are ∼<0.02 mag, consistent with current microvariability observations of radio-quiet quasars. Our stochastic model is therefore able to unify both long- and short-timescale optical variations in radio-quiet quasars as resulting from the same underlying process, while radio-loud quasars have an additional variability component that operates on timescales ∼<1 day.

  16. The physicist's companion to current fluctuations: one-dimensional bulk-driven lattice gases

    Science.gov (United States)

    Lazarescu, Alexandre

    2015-12-01

    One of the main features of statistical systems out of equilibrium is the currents they exhibit in their stationary state: microscopic currents of probability between configurations, which translate into macroscopic currents of mass, charge, etc. Understanding the general behaviour of these currents is an important step towards building a universal framework for non-equilibrium steady states akin to the Gibbs-Boltzmann distribution for equilibrium systems. In this review, we consider one-dimensional bulk-driven particle gases, and in particular the asymmetric simple exclusion process (ASEP) with open boundaries, which is one of the most popular models of one-dimensional transport. We focus, in particular, on the current of particles flowing through the system in its steady state, and on its fluctuations. We show how one can obtain the complete statistics of that current, through its large deviation function, by combining results from various methods: exact calculation of the cumulants of the current, using the integrability of the model; direct diagonalization of a biased process in the limits of very high or low current; hydrodynamic description of the model in the continuous limit using the macroscopic fluctuation theory. We give a pedagogical account of these techniques, starting with a quick introduction to the necessary mathematical tools, as well as a short overview of the existing works relating to the ASEP. We conclude by drawing the complete dynamical phase diagram of the current. We also remark on a few possible generalizations of these results.

  17. Patterns and singular features of extreme fluctuational paths of a periodically driven system

    International Nuclear Information System (INIS)

    Chen, Zhen; Liu, Xianbin

    2016-01-01

    Large fluctuations of an overdamped periodically driven oscillating system are investigated theoretically and numerically in the limit of weak noise. Optimal paths fluctuating to certain point are given by statistical analysis using the concept of prehistory probability distribution. The validity of statistical results is verified by solutions of boundary value problem. Optimal paths are found to change topologically when terminating points lie at opposite side of a switching line. Patterns of extreme paths are plotted through a proper parameterization of Lagrangian manifold having complicated structures. Several extreme paths to the same point are obtained by multiple solutions of boundary value solutions. Actions along various extreme paths are calculated and associated analysis is performed in relation to the singular features of the patterns. - Highlights: • Both extreme and optimal paths are obtained by various methods. • Boundary value problems are solved to ensure the validity of statistical results. • Topological structure of Lagrangian manifold is considered. • Singularities of the pattern of extreme paths are studied.

  18. Climatic fluctuation of temperature and air circulation in the Mediterranean

    International Nuclear Information System (INIS)

    Bartzokas, A.; Metaxas, D.A.

    1991-01-01

    The study of the long term fluctuation of sea surface temperature and 1000/500 mb thickness data in the Mediterranean sea during the last 45 years has shown that the global warming does not appear everywhere. Warming is not apparent in the East Mediterranean but only during the last years, the time series of surface pressure and relative geostrophic vorticity were examined for possible explanation: a strengthening of the northerly wind force have occurred. Thus it can be assumed that local atmospheric circulation changes may support or oppose the global warming in some places

  19. Modeling 100,000-year climate fluctuations in pre-Pleistocene time series

    Science.gov (United States)

    Crowley, Thomas J.; Kim, Kwang-Yul; Mengel, John G.; Short, David A.

    1992-01-01

    A number of pre-Pleistocene climate records exhibit significant fluctuations at the 100,000-year (100-ky) eccentricity period, before the time of such fluctuations in global ice volume. The origin of these fluctuations has been obscure. Results reported here from a modeling study suggest that such a response can occur over low-altitude land areas involved in monsoon fluctuations. The twice yearly passage of the sun across the equator and the seasonal timing of perihelion interact to increase both 100-ky and 400-ky power in the modeled temperature field. The magnitude of the temperature response is sufficiently large to leave an imprint on the geologic record, and simulated fluctuations resemble those found in records of Triassic lake levels.

  20. Climate-driven introduction of the Black Death and successive plague reintroductions into Europe.

    Science.gov (United States)

    Schmid, Boris V; Büntgen, Ulf; Easterday, W Ryan; Ginzler, Christian; Walløe, Lars; Bramanti, Barbara; Stenseth, Nils Chr

    2015-03-10

    The Black Death, originating in Asia, arrived in the Mediterranean harbors of Europe in 1347 CE, via the land and sea trade routes of the ancient Silk Road system. This epidemic marked the start of the second plague pandemic, which lasted in Europe until the early 19th century. This pandemic is generally understood as the consequence of a singular introduction of Yersinia pestis, after which the disease established itself in European rodents over four centuries. To locate these putative plague reservoirs, we studied the climate fluctuations that preceded regional plague epidemics, based on a dataset of 7,711 georeferenced historical plague outbreaks and 15 annually resolved tree-ring records from Europe and Asia. We provide evidence for repeated climate-driven reintroductions of the bacterium into European harbors from reservoirs in Asia, with a delay of 15 ± 1 y. Our analysis finds no support for the existence of permanent plague reservoirs in medieval Europe.

  1. Climate-driven introduction of the Black Death and successive plague reintroductions into Europe

    Science.gov (United States)

    Büntgen, Ulf; Easterday, W. Ryan; Ginzler, Christian; Walløe, Lars; Bramanti, Barbara; Stenseth, Nils Chr.

    2015-01-01

    The Black Death, originating in Asia, arrived in the Mediterranean harbors of Europe in 1347 CE, via the land and sea trade routes of the ancient Silk Road system. This epidemic marked the start of the second plague pandemic, which lasted in Europe until the early 19th century. This pandemic is generally understood as the consequence of a singular introduction of Yersinia pestis, after which the disease established itself in European rodents over four centuries. To locate these putative plague reservoirs, we studied the climate fluctuations that preceded regional plague epidemics, based on a dataset of 7,711 georeferenced historical plague outbreaks and 15 annually resolved tree-ring records from Europe and Asia. We provide evidence for repeated climate-driven reintroductions of the bacterium into European harbors from reservoirs in Asia, with a delay of 15 ± 1 y. Our analysis finds no support for the existence of permanent plague reservoirs in medieval Europe. PMID:25713390

  2. A dynamic, climate-driven model of Rift Valley fever

    Directory of Open Access Journals (Sweden)

    Joseph Leedale

    2016-03-01

    Full Text Available Outbreaks of Rift Valley fever (RVF in eastern Africa have previously occurred following specific rainfall dynamics and flooding events that appear to support the emergence of large numbers of mosquito vectors. As such, transmission of the virus is considered to be sensitive to environmental conditions and therefore changes in climate can impact the spatiotemporal dynamics of epizootic vulnerability. Epidemiological information describing the methods and parameters of RVF transmission and its dependence on climatic factors are used to develop a new spatio-temporal mathematical model that simulates these dynamics and can predict the impact of changes in climate. The Liverpool RVF (LRVF model is a new dynamic, process-based model driven by climate data that provides a predictive output of geographical changes in RVF outbreak susceptibility as a result of the climate and local livestock immunity. This description of the multi-disciplinary process of model development is accessible to mathematicians, epidemiological modellers and climate scientists, uniting dynamic mathematical modelling, empirical parameterisation and state-of-the-art climate information.

  3. Late Holocene vegetation changes in relation with climate fluctuations and human activity in Languedoc (southern France)

    OpenAIRE

    Azuara , J; Combourieu-Nebout , N; Lebreton , V; Mazier , F; Müller , S D; Dezileau , L ,

    2015-01-01

    International audience; Holocene climate fluctuations and human activity since the Neolithic have shaped present-day Mediter-ranean environments. Separating anthropogenic effects from climatic impacts to better understand Mediterranean pale-oenvironmental changes over the last millennia remains a challenging issue. High-resolution pollen analyses were un-dertaken on two cores from the Palavasian lagoon system (Hérault, southern France). These records allow reconstruction of vegetation dynamic...

  4. Climatic fluctuations and origin of sediments during Alleroed in Latvia

    International Nuclear Information System (INIS)

    Stelle, V.

    2000-01-01

    The Alleroed sediments are known from more than 30 sites in Latvia, but usually each of them reflects incomplete part of this important interval within the Late-Glacial. The lithological and palinological record of stratigraphically complete sections (Lielauce a.o.) proves that Alleroed is not climatically homogeneous. Relative cooling had been observed in middle part (about 11500-11300 years ago) of this interval. The pollen and spore composition, the radiocarbon dates and the changes in lithology of sediments during Alleroed time are discussed. The entire Alleroed interval may be subdivided into three stratigraphic units: lower (AL-1), middle (AL-2) and upper (AL-3). (author)

  5. Impacts of Seasonal Patterns of Climate on Recurrent Fluctuations in Tourism Demand: Evidence from Aruba

    NARCIS (Netherlands)

    Ridderstaat, J.R.; Oderber, M.; Croes, R.; Nijkamp, P.; Martens, P.

    2014-01-01

    This study estimates the effect of seasonal patterns of pull and push climate elements (rainfall, temperature, wind, and cloud coverage) on recurrent fluctuations in tourism demand from the United States (USA) and Venezuela to Aruba. The seasonal patterns were first isolated from the series using

  6. Neutron fluctuations in accelerator driven and power reactors via backward master equations

    International Nuclear Information System (INIS)

    Zhifeng Kuang

    2000-05-01

    The transport of neutrons in a reactor is a random process, and thus the number of neutrons in a reactor is a random variable. Fluctuations in the number of neutrons in a reactor can be divided into two categories, namely zero noise and power reactor noise. As the name indicates, they dominate (i.e. are observable) at different power levels. The reasons for their occurrences and utilization are also different. In addition, they are described via different mathematical tools, namely master equations and the Langevin equation, respectively. Zero noise carries information about some nuclear properties such as reactor reactivity. Hence methods such as Feynman- and Rossi-alpha methods have been established to determine the subcritical reactivity of a subcritical system. Such methods received a renewed interest recently with the advent of the so-called accelerator driven systems (ADS). Such systems, intended to be used either for energy production or transuranium transmutation, will use a subcritical core with a strong spallation source. A spallation source has statistical properties that are different from those of the traditionally used radioactive sources which were also assumed in the derivation of the Feynman- and Rossi-alpha formulae. Therefore it is necessary to re-derive the Feynman- and Rossi-alpha formulae. Such formulae for ADS have been derived recently but in simpler neutronic models. One subject of this thesis is the extension of such formulae to a more general case in which six groups of delayed neutron precursors are taken into account, and the full joint statistics of the prompt and all delayed groups is included. The involved complexity problems are solved with a combination of effective analytical techniques and symbolic algebra codes. Power reactor noise carries information about parametric perturbation of the system. Langevin technique has been used to extract such information. In such a treatment, zero noise has been neglected. This is a pragmatic

  7. Gravity wave-driven fluctuations in OH nightglow from an extended, dissipative emission region

    International Nuclear Information System (INIS)

    Schubert, G.; Walterscheid, R.L.; Hickey, M.P.

    1991-01-01

    The theory of gravity wave-driven fluctuations in the OH nightglow from an extended source region is generalized to account for effects of eddy kinematic viscosity v and eddy thermal diffusivity κ. In the nondiffusive case, the amplitudes and phases of vertically integrated normalized intensity (δI)/(bar I) and temperature (δT 1 )/(bar T 1 ) perturbations and vertically integrated Krassovsky's ratio (η) as functions of period are influenced by the upper limit of vertical integration of the extended source, especially at long periods when vertical wavelengths γ v are small. The effects, which include oscillations in (δT)/(bar I), (δT 1 )/(bar T 1 ), and (η), particularly at long periods, are due to constructive and destructive interference of nightglow signals from vertically separated levels of the OH emitting region that occur when γ v is comparable to or smaller than the thickness of the main emission region. The sensitivity of these ratios to the upper limit of vertical integration occurs because of the relatively small rate of decay of the intensity of OH emission with height above the peak emission level and the exponential growth with altitude of nondissipative gravity waves. Because eddy diffusion increases γ v , especially at long periods, and reduces wave growth with height compared with the case v = κ = 0, inclusion of eddy diffusion removes the sensitivity of (η) and the other ratios ot the maximum height of vertical integration. It is essential to account for both eddy diffusion and emission from the entire vertically extended emission region to correctly predict (η), (δI)/(bar I), and (δT 1 )/(bar T 1 ) at long gravity wave periods

  8. Climate-driven flushing of pore water in peatlands

    Science.gov (United States)

    Siegel, D. I.; Reeve, A. S.; Glaser, P. H.; Romanowicz, E. A.

    1995-04-01

    NORTHERN peatlands can act as either important sources or sinks for atmospheric carbon1,2. It is therefore important to understand how carbon cycling in these regions will respond to a changing climate. Existing carbon balance models for peatlands assume that fluid flow and advective mass transport are negligible at depth3,4, and that the effects of climate change should be essentially limited to the near-surface. Here we report the response of groundwater flow and porewater chemistry in the Glacial Lake Agassiz peat-lands of northern Minnesota to the regional drought cycle. Comparison of field observations and numerical simulations indicates that climate fluctuations of short duration may temporarily reverse the vertical direction of fluid flow through the peat, although this has little effect on water chemistry5. On the other hand, periods of drought persisting for at least 3-5 years produce striking changes in the chemistry of the pore water. These longer-term changes in hydrology influence the flux of nutrients and dissolved organic matter through the deeper peat, and therefore affect directly the rates of fermentation and methanogenesis, and the export of dissolved carbon compounds from the peatland.

  9. Contribution of climate-driven change in continental water storage to recent sea-level rise

    Science.gov (United States)

    Milly, P. C. D.; Cazenave, A.; Gennero, C.

    2003-01-01

    Using a global model of continental water balance, forced by interannual variations in precipitation and near-surface atmospheric temperature for the period 1981–1998, we estimate the sea-level changes associated with climate-driven changes in storage of water as snowpack, soil water, and ground water; storage in ice sheets and large lakes is not considered. The 1981–1998 trend is estimated to be 0.12 mm/yr, and substantial interannual fluctuations are inferred; for 1993–1998, the trend is 0.25 mm/yr. At the decadal time scale, the terrestrial contribution to eustatic (i.e., induced by mass exchange) sea-level rise is significantly smaller than the estimated steric (i.e., induced by density changes) trend for the same period, but is not negligibly small. In the model the sea-level rise is driven mainly by a downtrend in continental precipitation during the study period, which we believe was generated by natural variability in the climate system. PMID:14576277

  10. Escape routes, weak links, and desynchronization in fluctuation-driven networks

    DEFF Research Database (Denmark)

    Schäfer, Benjamin; Matthiae, Moritz; Zhang, Xiaozhu

    2017-01-01

    Shifting our electricity generation from fossil fuel to renewable energy sources introduces large fluctuations to the power system. Here, we demonstrate how increased fluctuations, reduced damping, and reduced intertia may undermine the dynamical robustness of power grid networks. Focusing...... on fundamental noise models, we derive analytic insights into which factors limit the dynamic robustness and how fluctuations may induce a system escape from an operating state. Moreover, we identify weak links in the grid that make it particularly vulnerable to fluctuations. These results thereby not only...

  11. Temporal and spatial variations in wildlife population fluctuations in Greenland; The effect of climate, environment and man

    DEFF Research Database (Denmark)

    Moshøj, Charlotte Margaret; Forchhammer, Mads C.; Forbes, Valery E.

    2009-01-01

    Temporal and spatial variations in wildlife population fluctuations in Greenland; The effect of climate, environment and man Moshøj, C.M, M.C.Forchhammer and V.E. Forbes Temporal and spatial variations in wildlife population fluctuations in Greenland; The effect of climate, environment and man...... and mammals display distinct population fluctuations of varying temporal and spatial scale. In Greenland, historical records, archaeological findings and oral accounts passed on from Inuit elders all document that the presence of wildlife species and their population sizes have undergone pronounced....... The results of this study will model future predictions of wildlife populations under changing climate variables and human hunting pressure....

  12. Interannual water-level fluctuations and the vegetation of prairie potholes: Potential impacts of climate change

    Science.gov (United States)

    van der Valk, Arnold; Mushet, David M.

    2016-01-01

    Mean water depth and range of interannual water-level fluctuations over wet-dry cycles in precipitation are major drivers of vegetation zone formation in North American prairie potholes. We used harmonic hydrological models, which require only mean interannual water depth and amplitude of water-level fluctuations over a wet–dry cycle, to examine how the vegetation zones in a pothole would respond to small changes in water depth and/or amplitude of water-level fluctuations. Field data from wetlands in Saskatchewan, North Dakota, and South Dakota were used to parameterize harmonic models for four pothole classes. Six scenarios in which small negative or positive changes in either mean water depth, amplitude of interannual fluctuations, or both, were modeled to predict if they would affect the number of zones in each wetland class. The results indicated that, in some cases, even small changes in mean water depth when coupled with a small change in amplitude of water-level fluctuations can shift a prairie pothole wetland from one class to another. Our results suggest that climate change could alter the relative proportion of different wetland classes in the prairie pothole region.

  13. How scaling fluctuation analyses can transform our view of the climate

    Science.gov (United States)

    Lovejoy, Shaun; Schertzer, Daniel

    2013-04-01

    There exist a bewildering diversity of proxy climate data including tree rings, ice cores, lake varves, boreholes, ice cores, pollen, foraminifera, corals and speleothems. Their quantitative use raises numerous questions of interpretation and calibration. Even in classical cases - such as the isotope signal in ice cores - the usual assumption of linear dependence on ambient temperature is only a first approximation. In other cases - such as speleothems - the isotope signals arise from multiple causes (which are not always understood) and this hinders their widespread use. We argue that traditional interpretations and calibrations - based on essentially deterministic comparisons between instrumental data, model outputs and proxies (albeit with the help of uncertainty analyses) - have been both overly ambitious while simultaneously underexploiting the data. The former since comparisons typically involve series at different temporal resolutions and from different geographical locations - one does not expect agreement in a deterministic sense, while with respect to climate models, one only expects statistical correspondences. The proxies are underexploited since comparisons are done at unique temporal and / or spatial resolutions whereas the fluctuations they describe provide information over wide ranges of scale. A convenient method of overcoming these difficulties is the use of fluctuation analysis systematically applied over the full range of available scales to determine the scaling proeprties. The new transformative element presented here, is to define fluctuations ΔT in a series T(t) at scale Δt not by differences (ΔT(Δt) = T(t+Δt) - T(t)) but rather by the difference in the means over the first and second halves of the lag Δt . This seemingly minor change - technically from "poor man's" to "Haar" wavelets - turns out to make a huge difference since for example, it is adequate for analysing temperatures from seconds to hundreds of millions of years yet

  14. A Science-Driven Photojournalistic Documentation of Climate Change (Invited)

    Science.gov (United States)

    Braasch, G.; Rothlein, J. E.

    2013-12-01

    Office of the President; two original books (one for middle schools with a co-author); publication in hundreds of magazines, textbooks and public interest websites; use during university, government and civic seminars and scientific meetings; and distribution among and use by Congressional offices. Most recently the project inspired films about youth involvement in citizen science and climate change education; and co-developed Apps for the iPad and iPhone which graphically show climate-driven changes in repeat photographs and maps. Financial support for this work has come principally from publication fees and grants from small foundations and individuals (via Blue Earth Alliance of Seattle).

  15. Life cycle ecophysiology of small pelagic fish and climate-driven changes in populations

    Science.gov (United States)

    Peck, Myron A.; Reglero, Patricia; Takahashi, Motomitsu; Catalán, Ignacio A.

    2013-09-01

    Due to their population characteristics and trophodynamic role, small pelagic fishes are excellent bio-indicators of climate-driven changes in marine systems world-wide. We argue that making robust projections of future changes in the productivity and distribution of small pelagics will require a cause-and-effect understanding of historical changes based upon physiological principles. Here, we reviewed the ecophysiology of small pelagic (clupeiform) fishes including a matrix of abiotic and biotic extrinsic factors (e.g., temperature, salinity, light, and prey characteristics) and stage-specific vital rates: (1) adult spawning, (2) survival and development of eggs and yolk sac larvae, and (3) feeding and growth of larvae, post-larvae and juveniles. Emphasis was placed on species inhabiting Northwest Pacific and Northeast Atlantic (European) waters for which summary papers are particularly scarce compared to anchovy and sardine in upwelling systems. Our review revealed that thermal niches (optimal and sub-optimal ranges in temperatures) were species- and stage-specific but that temperature effects only partly explained observed changes in the distribution and/or productivity of populations in the Northwest Pacific and Northeast Atlantic; changes in temperature may be necessary but not sufficient to induce population-level shifts. Prey availability during the late larval and early juvenile period was a common, density-dependent mechanism linked to fluctuations in populations but recruitment mechanisms were system-specific suggesting that generalizations of climate drivers across systems should be avoided. We identified gaps in knowledge regarding basic elements of the growth physiology of each life stage that will require additional field and laboratory study. Avenues of research are recommended that will aid the development of models that provide more robust, physiological-based projections of the population dynamics of these and other small pelagic fish. In our

  16. Predicting Chronic Climate-Driven Disturbances and Their Mitigation

    Energy Technology Data Exchange (ETDEWEB)

    McDowell, Nate G.; Michaletz, Sean T.; Bennett, Katrina E.; Solander, Kurt C.; Xu, Chonggang; Maxwell, Reed M.; Middleton, Richard S.

    2018-01-01

    Society increasingly demands the stable provision of ecosystem resources to support our population. Resource risks from climate-driven disturbances--including drought, heat, insect outbreaks, and wildfire--are rising as a chronic state of disequilibrium results from increasing temperatures and a greater frequency of extreme events. This confluence of increased demand and risk may soon reach critical thresholds. We explain here why extreme chronic disequilibrium of ecosystem function is likely to increase dramatically across the globe, creating no-analog conditions that challenge adaptation. We also present novel mechanistic theory that combines models for disturbance mortality and metabolic scaling to link size-dependent plant mortality to changes in ecosystem stocks and fluxes. Efforts must anticipate and model chronic ecosystem disequilibrium to properly prepare for resilience planning.

  17. Holocene Glacier Fluctuations in the Peruvian Andes Indicate Northern Climate Linkages

    Science.gov (United States)

    Licciardi, Joseph M.; Schaefer, Joerg M.; Taggart, Jean R.; Lund, David C.

    2009-09-01

    The role of the tropics in triggering, transmitting, and amplifying interhemispheric climate signals remains a key debate in paleoclimatology. Tropical glacier fluctuations provide important insight on regional paleoclimatic trends and forcings, but robust chronologies are scarce. Here, we report precise moraine ages from the Cordillera Vilcabamba (13°20‧S) of southern Peru that indicate prominent glacial events and associated climatic shifts in the outer tropics during the early Holocene and late in the “Little Ice Age” period. Our glacier chronologies differ from the New Zealand record but are broadly correlative with well-dated glacial records in Europe, suggesting climate linkages between the tropics and the North Atlantic region.

  18. Density Fluctuations in the Solar Wind Driven by Alfvén Wave Parametric Decay

    Science.gov (United States)

    Bowen, Trevor A.; Badman, Samuel; Hellinger, Petr; Bale, Stuart D.

    2018-02-01

    Measurements and simulations of inertial compressive turbulence in the solar wind are characterized by anti-correlated magnetic fluctuations parallel to the mean field and density structures. This signature has been interpreted as observational evidence for non-propagating pressure balanced structures, kinetic ion-acoustic waves, as well as the MHD slow-mode. Given the high damping rates of parallel propagating compressive fluctuations, their ubiquity in satellite observations is surprising and suggestive of a local driving process. One possible candidate for the generation of compressive fluctuations in the solar wind is the Alfvén wave parametric instability. Here, we test the parametric decay process as a source of compressive waves in the solar wind by comparing the collisionless damping rates of compressive fluctuations with growth rates of the parametric decay instability daughter waves. Our results suggest that generation of compressive waves through parametric decay is overdamped at 1 au, but that the presence of slow-mode-like density fluctuations is correlated with the parametric decay of Alfvén waves.

  19. Late Holocene vegetation changes in relation with climate fluctuations and human activities in Languedoc (Southern France)

    Science.gov (United States)

    Azuara, J.; Combourieu-Nebout, N.; Lebreton, V.; Mazier, F.; Müller, S. D.; Dezileau, L.

    2015-09-01

    Holocene climate fluctuations and human activities since the Neolithic have shaped present-day Mediterranean environments. Separating anthropogenic effects from climatic impacts to reconstruct Mediterranean paleoenvironments over the last millennia remains a challenging issue. High resolution pollen analyses were undertaken on two cores from the Palavasian lagoon system (Hérault, southern France). These records allow reconstruction of vegetation dynamics over the last 4500 years. Results are compared with climatic, historical and archeological archives. A long-term aridification trend is highlighted during the Late Holocene and three superimposed arid events are recorded at 4600-4300, 2800-2400 and 1300-1100 cal BP. These periods of climatic instability coincide in time with the rapid climatic events depicted in the Atlantic Ocean (Bond et al., 2001). From the Bronze Age (4000 cal BP) to the end of the Iron Age (around 2000 cal BP), the spread of evergreen taxa and loss of forest cover result from anthropogenic impact. The Antiquity is characterized by a major reforestation event related to the concentration of rural activities and populations in coastal plains leading to forest recovery in the mountains. A major regional deforestation occurred at the beginning of the High Middle Ages. Around 1000 cal BP, forest cover is minimal while cover of olive, chestnut and walnut expands in relation to increasing human influence. The present day vegetation dominated by Mediterranean shrubland and pines has been in existence since the beginning of the 20th century.

  20. Late Holocene vegetation changes in relation with climate fluctuations and human activity in Languedoc (southern France)

    Science.gov (United States)

    Azuara, J.; Combourieu-Nebout, N.; Lebreton, V.; Mazier, F.; Müller, S. D.; Dezileau, L.

    2015-12-01

    Holocene climate fluctuations and human activity since the Neolithic have shaped present-day Mediterranean environments. Separating anthropogenic effects from climatic impacts to better understand Mediterranean paleoenvironmental changes over the last millennia remains a challenging issue. High-resolution pollen analyses were undertaken on two cores from the Palavasian lagoon system (Hérault, southern France). These records allow reconstruction of vegetation dynamics over the last 4500 years. Results are compared with climatic, historical and archeological archives. A long-term aridification trend is highlighted during the late Holocene, and three superimposed arid events are recorded at 4600-4300, 2800-2400 and 1300-1100 cal BP. These periods of high-frequency climate variability coincide in time with the rapid climatic events observed in the Atlantic Ocean (Bond et al., 2001). From the Bronze Age (4000 cal BP) to the end of the Iron Age (around 2000 cal BP), the spread of sclerophyllous taxa and loss of forest cover result from anthropogenic impact. Classical Antiquity is characterized by a major reforestation event related to the concentration of rural activity and populations in coastal plains leading to forest recovery in the mountains. A major regional deforestation occurred at the beginning of the High Middle Ages. Around 1000 cal BP, forest cover is minimal while the cover of olive, chestnut and walnut expands in relation to increasing human influence. The present-day vegetation dominated by Mediterranean shrubland and pines has been in existence since the beginning of the 20th century.

  1. Multifractal fluctuations in joint angles during infant spontaneous kicking reveal multiplicativity-driven coordination

    International Nuclear Information System (INIS)

    Stephen, Damian G.; Hsu, Wen-Hao; Young, Diana; Saltzman, Elliot L.; Holt, Kenneth G.; Newman, Dava J.; Weinberg, Marc; Wood, Robert J.; Nagpal, Radhika; Goldfield, Eugene C.

    2012-01-01

    Previous research has considered infant spontaneous kicking as a form of exploration. According to this view, spontaneous kicking provides information about motor degrees of freedom and may shape multijoint coordinations for more complex movement patterns such as gait. Recent work has demonstrated that multifractal, multiplicative fluctuations in exploratory movements index energy flows underlying perceptual-motor information. If infant spontaneous kicking is exploratory and occasions an upstream flow of information from the motor periphery, we expected not only that multiplicativity of fluctuations at the hip should promote multiplicativity of fluctuations at more distal joints (i.e., reflecting downstream effects of neural control) but also that multiplicativity at more distal joints should promote multiplicativity at the hip. Multifractal analysis demonstrated that infant spontaneous kicking in four typically developing infants for evidence of multiplicative fluctuations in multiple joint angles along the leg (i.e., hip, knee, and ankle) exhibited multiplicativity. Vector autoregressive modeling demonstrated that only one leg exhibited downstream effects but that both legs exhibited upstream effects. These results confirm the exploratory aspect of infant spontaneous kicking and suggest chaotic dynamics in motor coordination. They also resonate with existing models of chaos-controlled robotics and noise-based interventions for rehabilitating motor coordination in atypically developing patients.

  2. Geomorphic features as indicators of climatic fluctuations in a periglacial environment, northern Sweden

    Energy Technology Data Exchange (ETDEWEB)

    Nyberg, R; Lindh, L [Lund Univ. (SE). Dept. of Physical Geography

    1990-01-01

    Goemorphic responses to climatic fluctuations in the periglacial mountain environment of northern Sweden, especially the Abisko mountains, are discussed. Although the frequency and magnitude of rapid mass movements are related to climatic conditions, the depositional patterns of the processes and the variable availability of source material complicate their use as climatic indicators. Possibly, debris flows and slushflows were frequent during the Little Ice Age, according to lichenometric dating of old deposits. Field observations suggest a fairly high frequency also during the last few decades. Boulder pavements, moraine-like ridges and glacial striae in front of major snowfields indicate these were previously larger and in some cases active as small glaciers perhaps in the cold beginning of the 1900's. During the warm 1920-30's snowpatches and glaciers, as well as permafrost mounds were affected by a general degeneration. Climatic inferences made from the mentioned features are still very crude. Tentatively, it is suggested that they are presently beginning to respond to the cooling trend affecting northern Scandinavia since about 1940. The anticipated impact of a greenhouse warming of the atmosphere has thus so far not been noticeable in this high latitude area. (authors).

  3. Time-dependent perpendicular fluctuations in the driven lattice Lorentz gas

    Science.gov (United States)

    Leitmann, Sebastian; Schwab, Thomas; Franosch, Thomas

    2018-02-01

    We present results for the fluctuations of the displacement of a tracer particle on a planar lattice pulled by a step force in the presence of impenetrable, immobile obstacles. The fluctuations perpendicular to the applied force are evaluated exactly in first order of the obstacle density for arbitrarily strong pulling and all times. The complex time-dependent behavior is analyzed in terms of the diffusion coefficient, local exponent, and the non-Skellam parameter, which quantifies deviations from the dynamics on the lattice in the absence of obstacles. The non-Skellam parameter along the force is analyzed in terms of an asymptotic model and reveals a power-law growth for intermediate times.

  4. Climate-driven seasonal geocenter motion during the GRACE period

    Science.gov (United States)

    Zhang, Hongyue; Sun, Yu

    2018-03-01

    Annual cycles in the geocenter motion time series are primarily driven by mass changes in the Earth's hydrologic system, which includes land hydrology, atmosphere, and oceans. Seasonal variations of the geocenter motion have been reliably determined according to Sun et al. (J Geophys Res Solid Earth 121(11):8352-8370, 2016) by combining the Gravity Recovery And Climate Experiment (GRACE) data with an ocean model output. In this study, we reconstructed the observed seasonal geocenter motion with geophysical model predictions of mass variations in the polar ice sheets, continental glaciers, terrestrial water storage (TWS), and atmosphere and dynamic ocean (AO). The reconstructed geocenter motion time series is shown to be in close agreement with the solution based on GRACE data supporting with an ocean bottom pressure model. Over 85% of the observed geocenter motion time series, variance can be explained by the reconstructed solution, which allows a further investigation of the driving mechanisms. We then demonstrated that AO component accounts for 54, 62, and 25% of the observed geocenter motion variances in the X, Y, and Z directions, respectively. The TWS component alone explains 42, 32, and 39% of the observed variances. The net mass changes over oceans together with self-attraction and loading effects also contribute significantly (about 30%) to the seasonal geocenter motion in the X and Z directions. Other contributing sources, on the other hand, have marginal (less than 10%) impact on the seasonal variations but introduce a linear trend in the time series.

  5. CLIMATIC SIGNALS FROM INTRA-ANNUAL DENSITY FLUCTUATION FREQUENCY IN MEDITERRANEAN PINES AT A REGIONAL SCALE

    Directory of Open Access Journals (Sweden)

    Enrica eZalloni

    2016-05-01

    Full Text Available Tree rings provide information about the climatic conditions during the growing season by recording them in different anatomical features, such as Intra-Annual Density Fluctuations (IADFs. IADFs are intra-annual changes of wood density appearing as latewood-like cells within earlywood, or earlywood-like cells within latewood. The occurrence of IADFs is dependent on the age and size of the tree, and it is triggered by climatic drivers. The variations of IADF frequency of different species and their dependence on climate across a wide geographical range have still to be explored. The objective of this study is to investigate the effect of age, tree-ring width and climate on IADF formation and frequency at a regional scale across the Mediterranean Basin in Pinus halepensis Mill., Pinus pinaster Ait. and Pinus pinea L. The analyzed tree-ring network was composed of P. pinea trees growing at 11 sites (2 in Italy, 4 in Spain and 4 in Portugal, P. pinaster from 19 sites (2 in Italy, 13 in Spain and 4 in Portugal, and P. halepensis from 38 sites in Spain. The correlations between IADF frequency and monthly minimum, mean and maximum temperatures, as well as between IADF frequency and total precipitation, were analyzed. A significant negative relationship between IADF frequency and tree-ring age was found for the three Mediterranean pines. Moreover, IADFs were more frequent in wider rings than in narrower ones, although the widest rings showed a reduced IADF frequency. Wet conditions during late summer/early autumn triggered the formation of IADFs in the three species. Our results suggest the existence of a common climatic driver for the formation of IADFs in Mediterranean pines, highlighting the potential use of IADF frequency as a proxy for climate reconstructions with geographical resolution.

  6. Climatic Signals from Intra-annual Density Fluctuation Frequency in Mediterranean Pines at a Regional Scale

    Science.gov (United States)

    Zalloni, Enrica; de Luis, Martin; Campelo, Filipe; Novak, Klemen; De Micco, Veronica; Di Filippo, Alfredo; Vieira, Joana; Nabais, Cristina; Rozas, Vicente; Battipaglia, Giovanna

    2016-01-01

    Tree rings provide information about the climatic conditions during the growing season by recording them in different anatomical features, such as intra-annual density fluctuations (IADFs). IADFs are intra-annual changes of wood density appearing as latewood-like cells within earlywood, or earlywood-like cells within latewood. The occurrence of IADFs is dependent on the age and size of the tree, and it is triggered by climatic drivers. The variations of IADF frequency of different species and their dependence on climate across a wide geographical range have still to be explored. The objective of this study is to investigate the effect of age, tree-ring width and climate on IADF formation and frequency at a regional scale across the Mediterranean Basin in Pinus halepensis Mill., Pinus pinaster Ait., and Pinus pinea L. The analyzed tree-ring network was composed of P. pinea trees growing at 10 sites (2 in Italy, 4 in Spain, and 4 in Portugal), P. pinaster from 19 sites (2 in Italy, 13 in Spain, and 4 in Portugal), and P. halepensis from 38 sites in Spain. The correlations between IADF frequency and monthly minimum, mean and maximum temperatures, as well as between IADF frequency and total precipitation, were analyzed. A significant negative relationship between IADF frequency and tree-ring age was found for the three Mediterranean pines. Moreover, IADFs were more frequent in wider rings than in narrower ones, although the widest rings showed a reduced IADF frequency. Wet conditions during late summer/early autumn triggered the formation of IADFs in the three species. Our results suggest the existence of a common climatic driver for the formation of IADFs in Mediterranean pines, highlighting the potential use of IADF frequency as a proxy for climate reconstructions with geographical resolution. PMID:27200052

  7. Soliton Coupling Driven by Phase Fluctuations in Auto-Parametric Resonance

    CERN Document Server

    Binder, B

    2002-01-01

    In this paper the interaction of sine-Gordon solitons and mediating linear waves is modelled by a special case of auto-parametric resonance, the Rayleigh-type self-excited non-linear autonomous system driven by a statistical phase gradient related to the soliton energy. Spherical symmetry can stimulate "whispering gallery modes" (WGM) with integral coupling number M=137.

  8. Experimental and theoretical evidence for fluctuation driven activations in an excitable chemical system

    Science.gov (United States)

    Hastings, Harold; Sobel, Sabrina; Field, Richard; Minchenberg, Scott; Spinelli, Nicole; Zauderer, Keith

    2011-03-01

    An excitable medium is a system in which small perturbations die out, but sufficiently large perturbations generate large ``excitations.'' Biological examples include neurons and the heart; the latter supports waves of excitation normally generated by the sinus node, but occasionally generated by other mechanisms. The ferroin-catalyzed Belousov-Zhabotinsky reaction is the prototype chemical excitable medium. We present experimental and theoretical evidence for that random fluctuations can generate excitations in the Belousov-Zhabothinsky reaction. Although the heart is significantly different, there are some scaling analogies. This material is based upon work supported by the Department of Energy under Award Number DE-FG02-08ER64623.

  9. Far-infrared laser scattering from spontaneous and driven fluctuations in the UCLA microtor tokamak

    International Nuclear Information System (INIS)

    Lee, P.; Luhmann, N.C.; Park, H. Jr.; Peebles, W.A.; Taylor, R.J.; Xu, Ying; Yu, C.X.

    1982-01-01

    A far-infrared (FIR) laser scattering system for the study of tokamak density fluctuations is described. Recent scattering data from low frequency microturbulence in high density (n >= 5 x 10 13 cm -3 ) microtor discharges are presented. In addition, the first observation and identification of internal modes generated during ICRF heating are described. The latter study directly conforms to fast wave mode conversion theory in a two-ion species plasma. In particular, the first internal observation of mode converted ion Bernstein waves in a tokamak plasma has been made. (author)

  10. Magnetic fluctuation driven cross-field particle transport in the reversed-field pinch

    International Nuclear Information System (INIS)

    Scheffel, J.; Liu, D.

    1997-01-01

    Electrostatic and electromagnetic fluctuations generally cause cross-field particle transport in confined plasmas. Thus core localized turbulence must be kept at low levels for sufficient energy confinement in magnetic fusion plasmas. Reversed-field pinch (RFP) equilibria can, theoretically, be completely stable to ideal and resistive (tearing) magnetohydrodynamic (MHD) modes at zero beta. Unstable resistive interchange modes are, however, always present at experimentally relevant values of the poloidal beta β θ . An analytical quasilinear, ambipolar diffusion model is here used to model associated particle transport. The results indicate that core density fluctuations should not exceed a level of about 1% for plasmas of fusion interest. Parameters of experimentally relevant stationary states of the RFP were adjusted to minimize growth rates, using a fully resistive linearized MHD stability code. Density gradient effects are included through employing a parabolic density profile. The scaling of particle diffusion [D(r)∝λ 2 n 0.5 T/aB, where λ is the mode width] is such that the effects of particle transport are milder in present day RFP experiments than in future reactor-relevant plasmas. copyright 1997 American Institute of Physics

  11. Flux-flow noise driven by quantum fluctuations in a thick amorphous film

    Energy Technology Data Exchange (ETDEWEB)

    Okuma, S. [Research Center for Low Temperature Physics, Tokyo Institute of Technology, 2-12-1 Ohokayama, Meguro-ku, Tokyo 152-8551 (Japan)]. E-mail: sokuma@o.cc.titech.ac.jp; Kainuma, K. [Research Center for Low Temperature Physics, Tokyo Institute of Technology, 2-12-1 Ohokayama, Meguro-ku, Tokyo 152-8551 (Japan); Kishimoto, T. [Research Center for Low Temperature Physics, Tokyo Institute of Technology, 2-12-1 Ohokayama, Meguro-ku, Tokyo 152-8551 (Japan); Kohara, M. [Research Center for Low Temperature Physics, Tokyo Institute of Technology, 2-12-1 Ohokayama, Meguro-ku, Tokyo 152-8551 (Japan)

    2006-10-01

    We measure the voltage-noise spectrum S {sub V}(f) (where f is a frequency) as well as the time (t)-dependent component {delta}V(t) of the flux-flow voltage in the low temperature liquid phase of a thick amorphous Mo {sub x}Si{sub 1-x} film. In the quantum-liquid phase both the amplitude vertical bar {delta}V vertical bar of voltage fluctuations and the asymmetry of the probability distribution of {delta}V(t) show an anomalous increase; the spectral shape of S {sub V}(f) is of a Lorentzian type, suggesting the shot-noise-like vortex motion with a large 'vortex-bundle size' and short characteristic time.

  12. Climate change and water table fluctuation: Implications for raised bog surface variability

    Science.gov (United States)

    Taminskas, Julius; Linkevičienė, Rita; Šimanauskienė, Rasa; Jukna, Laurynas; Kibirkštis, Gintautas; Tamkevičiūtė, Marija

    2018-03-01

    Cyclic peatland surface variability is influenced by hydrological conditions that highly depend on climate and/or anthropogenic activities. A low water level leads to a decrease of peatland surface and an increase of C emissions into the atmosphere, whereas a high water level leads to an increase of peatland surface and carbon sequestration in peatlands. The main aim of this article is to evaluate the influence of hydrometeorological conditions toward the peatland surface and its feedback toward the water regime. A regional survey of the raised bog water table fluctuation and surface variability was made in one of the largest peatlands in Lithuania. Two appropriate indicators for different peatland surface variability periods (increase and decrease) were detected. The first one is an 200 mm y- 1 average net rainfall over a three-year range. The second one is an average annual water depth of 25-30 cm. The application of these indicators enabled the reconstruction of Čepkeliai peatland surface variability during a 100 year period. Processes of peatland surface variability differ in time and in separate parts of peatland. Therefore, internal subbasins in peatland are formed. Subbasins involve autogenic processes that can later affect their internal hydrology, nutrient status, and vegetation succession. Internal hydrological conditions, surface fluctuation, and vegetation succession in peatland subbasins should be taken into account during evaluation of their state, nature management projects, and other peatland research works.

  13. The physicist's companion to current fluctuations: one-dimensional bulk-driven lattice gases

    International Nuclear Information System (INIS)

    Lazarescu, Alexandre

    2015-01-01

    One of the main features of statistical systems out of equilibrium is the currents they exhibit in their stationary state: microscopic currents of probability between configurations, which translate into macroscopic currents of mass, charge, etc. Understanding the general behaviour of these currents is an important step towards building a universal framework for non-equilibrium steady states akin to the Gibbs–Boltzmann distribution for equilibrium systems. In this review, we consider one-dimensional bulk-driven particle gases, and in particular the asymmetric simple exclusion process (ASEP) with open boundaries, which is one of the most popular models of one-dimensional transport. We focus, in particular, on the current of particles flowing through the system in its steady state, and on its fluctuations. We show how one can obtain the complete statistics of that current, through its large deviation function, by combining results from various methods: exact calculation of the cumulants of the current, using the integrability of the model; direct diagonalization of a biased process in the limits of very high or low current; hydrodynamic description of the model in the continuous limit using the macroscopic fluctuation theory. We give a pedagogical account of these techniques, starting with a quick introduction to the necessary mathematical tools, as well as a short overview of the existing works relating to the ASEP. We conclude by drawing the complete dynamical phase diagram of the current. We also remark on a few possible generalizations of these results. (topical review)

  14. Fluctuation-driven flocking movement in three dimensions and scale-free correlation.

    Science.gov (United States)

    Niizato, Takayuki; Gunji, Yukio-Pegio

    2012-01-01

    Recent advances in the study of flocking behavior have permitted more sophisticated analyses than previously possible. The concepts of "topological distances" and "scale-free correlations" are important developments that have contributed to this improvement. These concepts require us to reconsider the notion of a neighborhood when applied to theoretical models. Previous work has assumed that individuals interact with neighbors within a certain radius (called the "metric distance"). However, other work has shown that, assuming topological interactions, starlings interact on average with the six or seven nearest neighbors within a flock. Accounting for this observation, we previously proposed a metric-topological interaction model in two dimensions. The goal of our model was to unite these two interaction components, the metric distance and the topological distance, into one rule. In our previous study, we demonstrated that the metric-topological interaction model could explain a real bird flocking phenomenon called scale-free correlation, which was first reported by Cavagna et al. In this study, we extended our model to three dimensions while also accounting for variations in speed. This three-dimensional metric-topological interaction model displayed scale-free correlation for velocity and orientation. Finally, we introduced an additional new feature of the model, namely, that a flock can store and release its fluctuations.

  15. Fluctuation-driven flocking movement in three dimensions and scale-free correlation.

    Directory of Open Access Journals (Sweden)

    Takayuki Niizato

    Full Text Available Recent advances in the study of flocking behavior have permitted more sophisticated analyses than previously possible. The concepts of "topological distances" and "scale-free correlations" are important developments that have contributed to this improvement. These concepts require us to reconsider the notion of a neighborhood when applied to theoretical models. Previous work has assumed that individuals interact with neighbors within a certain radius (called the "metric distance". However, other work has shown that, assuming topological interactions, starlings interact on average with the six or seven nearest neighbors within a flock. Accounting for this observation, we previously proposed a metric-topological interaction model in two dimensions. The goal of our model was to unite these two interaction components, the metric distance and the topological distance, into one rule. In our previous study, we demonstrated that the metric-topological interaction model could explain a real bird flocking phenomenon called scale-free correlation, which was first reported by Cavagna et al. In this study, we extended our model to three dimensions while also accounting for variations in speed. This three-dimensional metric-topological interaction model displayed scale-free correlation for velocity and orientation. Finally, we introduced an additional new feature of the model, namely, that a flock can store and release its fluctuations.

  16. The Effect of Climate, Environment and Man on Variations in Wildlife Population Fluctuations in Greenland Over 200 Years

    DEFF Research Database (Denmark)

    Moshøj, Charlotte Margaret

    The Effect of Climate, Environment and Man on Variations in Wildlife Population Fluctuations in Greenland Over 200 Years Moshøj, Charlotte The underlying factors of species fluctuating population dynamics has been the dominant focus of attention in population ecology throughout much of this century...... passed on from Inuit elders all document that the presence of wildlife species and their population sizes have undergone pronounced fluctuations throughout recordable historical time. The most detailed accounts are found for the species that were harvested or had economical value. While several recent...... data, environmental factors and temporal variations in social and demographic parameters in the existing society. The results of this study model future predictions of wildlife populations under changing climate variables and human hunting pressure. View Presentation....

  17. Fordism, Finance-driven Capitalism, and Climate Change

    DEFF Research Database (Denmark)

    Buch-Hansen, Hubert

    2014-01-01

    Review of Capitalism and Climate Change: Theoretical Discussion, Historical Development and Policy Responses by Max Koch. New York: Palgrave Macmillan, 2012, pp. 240, ISBN: 9780230272514, £55 (hbk.)......Review of Capitalism and Climate Change: Theoretical Discussion, Historical Development and Policy Responses by Max Koch. New York: Palgrave Macmillan, 2012, pp. 240, ISBN: 9780230272514, £55 (hbk.)...

  18. Climate change driven plant-metal-microbe interactions.

    Science.gov (United States)

    Rajkumar, Mani; Prasad, Majeti Narasimha Vara; Swaminathan, Sandhya; Freitas, Helena

    2013-03-01

    Various biotic and abiotic stress factors affect the growth and productivity of crop plants. Particularly, the climatic and/or heavy metal stress influence various processes including growth, physiology, biochemistry, and yield of crops. Climatic changes particularly the elevated atmospheric CO₂ enhance the biomass production and metal accumulation in plants and help plants to support greater microbial populations and/or protect the microorganisms against the impacts of heavy metals. Besides, the indirect effects of climatic change (e.g., changes in the function and structure of plant roots and diversity and activity of rhizosphere microbes) would lead to altered metal bioavailability in soils and concomitantly affect plant growth. However, the effects of warming, drought or combined climatic stress on plant growth and metal accumulation vary substantially across physico-chemico-biological properties of the environment (e.g., soil pH, heavy metal type and its bio-available concentrations, microbial diversity, and interactive effects of climatic factors) and plant used. Overall, direct and/or indirect effects of climate change on heavy metal mobility in soils may further hinder the ability of plants to adapt and make them more susceptible to stress. Here, we review and discuss how the climatic parameters including atmospheric CO₂, temperature and drought influence the plant-metal interaction in polluted soils. Other aspects including the effects of climate change and heavy metals on plant-microbe interaction, heavy metal phytoremediation and safety of food and feed are also discussed. This review shows that predicting how plant-metal interaction responds to altering climatic change is critical to select suitable crop plants that would be able to produce more yields and tolerate multi-stress conditions without accumulating toxic heavy metals for future food security. Copyright © 2012 Elsevier Ltd. All rights reserved.

  19. Role of model structure on the response of soil biogeochemistry to hydro-climatic fluctuations

    Science.gov (United States)

    Manzoni, S.; Porporato, A.

    2005-05-01

    Soil carbon and nutrient cycles are strongly affected by hydro-climatic variability, which interacts with the internal ecosystem structure. Here we test the implications of biogeochemical model structure on such dynamics by extending an existing model by the authors and coworkers. When forced by hydro-climatic fluctuations, the different model structures induce specific preferential nutrient paths among the soil pools, which in turn affect nutrient distribution and availability to microbes and plants. In particular, if it is assumed that microbes can directly assimilate organic nitrogen, plants tend to be inferior competitors for nutrients even in well-watered conditions, while if a certain amount of organic nitrogen is assumed to be mineralized without being first incorporated into microbial cells, vegetation can be advantaged over a wide range of soil moisture values. We also investigate the intensification of competition for nutrients (e.g., nitrogen) between plant and soil microbial communities under extreme hydrologic conditions, such as droughts and intense storms. Frequent rainfall events may determine ideal soil moisture conditions for plant uptake, enhancing nitrogen leaching while lowering oxygen concentration and inhibiting microbial activity. During droughts, the soil water potential often drops to the point of hampering the plant nutrient uptake while still remaining high enough for microbial decomposition and nitrogen immobilization. The interplay of microbe and vegetation water stress is investigated in depth as it controls the ability of one community (e.g., plants or soil microbes) to establish competitive advantage on the other. The long-term effects of these dynamics of competition and nutrient allocation are explored under steady-state and stochastic soil moisture conditions to analyze the feedbacks between soil organic matter and vegetation dynamics.

  20. Metabolic Rate and Climatic Fluctuations Shape Continental Wide Pattern of Genetic Divergence and Biodiversity in Fishes

    Science.gov (United States)

    April, Julien; Hanner, Robert H.; Mayden, Richard L.; Bernatchez, Louis

    2013-01-01

    Taxonomically exhaustive and continent wide patterns of genetic divergence within and between species have rarely been described and the underlying evolutionary causes shaping biodiversity distribution remain contentious. Here, we show that geographic patterns of intraspecific and interspecific genetic divergence among nearly all of the North American freshwater fish species (>750 species) support a dual role involving both the late Pliocene-Pleistocene climatic fluctuations and metabolic rate in determining latitudinal gradients of genetic divergence and very likely influencing speciation rates. Results indicate that the recurrent glacial cycles caused global reduction in intraspecific diversity, interspecific genetic divergence, and species richness at higher latitudes. At the opposite, longer geographic isolation, higher metabolic rate increasing substitution rate and possibly the rapid accumulation of genetic incompatibilities, led to an increasing biodiversity towards lower latitudes. This indicates that both intrinsic and extrinsic factors similarly affect micro and macro evolutionary processes shaping global patterns of biodiversity distribution. These results also indicate that factors favouring allopatric speciation are the main drivers underlying the diversification of North American freshwater fishes. PMID:23922969

  1. Climate-driven seasonal geocenter motion during the GRACE period

    NARCIS (Netherlands)

    Zhang, Hongyue; Sun, Y.

    2018-01-01

    Annual cycles in the geocenter motion time series are primarily driven by mass changes in the Earth’s hydrologic system, which includes land hydrology, atmosphere, and oceans. Seasonal variations of the geocenter motion have been reliably determined according to Sun et al. (J Geophys Res Solid

  2. Fluctuations in ammonia oxidizing communities across agricultural soils are driven by soil structure and pH

    Directory of Open Access Journals (Sweden)

    Michele C ePereira e Silva

    2012-03-01

    Full Text Available The milieu in soil in which microorganisms dwell is never constant. Conditions such as temperature, water availability, pH and nutrients frequently change, impacting the overall functioning of the soil system. To understand the effects of such factors on soil functioning, proxies (indicators of soil function are needed that, in a sensitive manner, reveal normal amplitude of variation. Thus, the so-called normal operating range (NOR of soil can be defined. In this study we determined different components of nitrification by analyzing, in eight agricultural soils, how the community structures and sizes of ammonia oxidizing bacteria and archaea (AOB and AOA, respectively, and their activity, fluctuate over spatial and temporal scales. The results indicated that soil pH and soil type are the main factors that influence the size and structure of the AOA and AOB, as well as their function. The nitrification rates varied between 0.11 ± 0.03 µgN.h-1.gdw-1 and 1.68 ± 0.11 µgN.h-1.gdw-1, being higher in soils with higher clay content (1.09 ± 0.12 µgN.h-1.gdw-1 and lower in soils with lower clay percentages (0.27 ± 0.04 µgN.h-1.gdw-1. Nitrifying activity was driven by soil pH, mostly related to its effect on AOA but not on AOB abundance. Regarding the influence of soil parameters, clay content was the main soil factor shaping the structure of both the AOA and AOB communities. Overall, the potential nitrifying activities were higher and more variable over time in the clayey than in the sandy soils. Whereas the structure of AOB fluctuated more (62.7 ± 2.10% the structure of AOA communities showed lower amplitude of variation (53.65 ± 3.37%. Similar trends were observed for the sizes of these communities. The present work represents a first step towards defining a NOR for soil nitrification. Moreover, the clear effect of soil texture established here suggests that the NOR should be defined in a soil-type-specific manner.

  3. A decade of sea level rise slowed by climate-driven hydrology.

    Science.gov (United States)

    Reager, J T; Gardner, A S; Famiglietti, J S; Wiese, D N; Eicker, A; Lo, M-H

    2016-02-12

    Climate-driven changes in land water storage and their contributions to sea level rise have been absent from Intergovernmental Panel on Climate Change sea level budgets owing to observational challenges. Recent advances in satellite measurement of time-variable gravity combined with reconciled global glacier loss estimates enable a disaggregation of continental land mass changes and a quantification of this term. We found that between 2002 and 2014, climate variability resulted in an additional 3200 ± 900 gigatons of water being stored on land. This gain partially offset water losses from ice sheets, glaciers, and groundwater pumping, slowing the rate of sea level rise by 0.71 ± 0.20 millimeters per year. These findings highlight the importance of climate-driven changes in hydrology when assigning attribution to decadal changes in sea level. Copyright © 2016, American Association for the Advancement of Science.

  4. Separating out the influence of climatic trend, fluctuations, and extreme events on crop yield: a case study in Hunan Province, China

    Science.gov (United States)

    Wang, Zhu; Shi, Peijun; Zhang, Zhao; Meng, Yongchang; Luan, Yibo; Wang, Jiwei

    2017-09-01

    Separating out the influence of climatic trend, fluctuations and extreme events on crop yield is of paramount importance to climate change adaptation, resilience, and mitigation. Previous studies lack systematic and explicit assessment of these three fundamental aspects of climate change on crop yield. This research attempts to separate out the impacts on rice yields of climatic trend (linear trend change related to mean value), fluctuations (variability surpassing the "fluctuation threshold" which defined as one standard deviation (1 SD) of the residual between the original data series and the linear trend value for each climatic variable), and extreme events (identified by absolute criterion for each kind of extreme events related to crop yield). The main idea of the research method was to construct climate scenarios combined with crop system simulation model. Comparable climate scenarios were designed to express the impact of each climate change component and, were input to the crop system model (CERES-Rice), which calculated the related simulated yield gap to quantify the percentage impacts of climatic trend, fluctuations, and extreme events. Six Agro-Meteorological Stations (AMS) in Hunan province were selected to study the quantitatively impact of climatic trend, fluctuations and extreme events involving climatic variables (air temperature, precipitation, and sunshine duration) on early rice yield during 1981-2012. The results showed that extreme events were found to have the greatest impact on early rice yield (-2.59 to -15.89%). Followed by climatic fluctuations with a range of -2.60 to -4.46%, and then the climatic trend (4.91-2.12%). Furthermore, the influence of climatic trend on early rice yield presented "trade-offs" among various climate variables and AMS. Climatic trend and extreme events associated with air temperature showed larger effects on early rice yield than other climatic variables, particularly for high-temperature events (-2.11 to -12

  5. Disentangling the climate-driven bimodal growth pattern in coastal and continental Mediterranean pine stands.

    Science.gov (United States)

    Pacheco, Arturo; Camarero, J Julio; Ribas, Montse; Gazol, Antonio; Gutierrez, E; Carrer, Marco

    2018-02-15

    Mediterranean climate promotes two distinct growth peaks separated by summer quiescence in trees. This bimodal pattern has been associated to favourable growing conditions during spring and autumn when mild temperatures and soil-water availability enhance cambial activity. Climatic models predict progressive warming and drying for the Mediterranean Basin, which could shorten or shift the spring and autumn growing seasons. We explored this idea by comparing two sites with different Mediterranean climate types (continental/dry and coastal/wet) and studied how climate drives the bimodal growth pattern in Aleppo pine (Pinus halepensis). Specifically we investigated the intra-annual changes in wood anatomy and the corresponding formation of density fluctuations (IADF). Trees on both sites were analyzed by dendrometer monitoring and by developing chronologies of wood anatomical traits. Radial-increment dynamics followed a similar bimodal pattern in both sites but coastal trees showed higher increments during the spring and autumn growth peaks, especially in autumn. The summer rest of cambium activity occurs almost one month earlier in the coastal than in the inland site. Lumen area and cell-wall thickness were significantly smaller in the continental site, while the increment rate of cell-wall thickness during an IADF event was much higher in the coastal pines. The accumulated soil moisture deficit was the main climatic constraint of tracheid enlargement in continental pines. Intra-annual density fluctuations were more frequent in the coastal trees where wood anatomy features recover to average values after such events, meanwhile inland trees presented a much lower recovery rate. Growth bimodality and the formation of density fluctuations were linked, but mild climate of the coastal site allows a longer growing season, which explains why trees in this area showed higher and more variable growth rates. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Pastoral suitability driven by future climate change along the Apennines

    Directory of Open Access Journals (Sweden)

    Camilla Dibari

    2015-09-01

    Full Text Available This work aims at evaluating the impacts of climate change on pastoral resources located along the Apennines chain. To this end, random forest machine learning model was first calibrated for the present period and then applied to future conditions, as projected by HadCM3 general circulation model, in order to simulate possible spatial variation/shift of pastoral areas in two time slices (centred on 2050 and 2080 under A2 and B2 SRES scenarios. Pre-existent spatial database, namely Corine land cover map and WorldClim, were integrated and harmonised in a GIS environment in order to extract climate variables (mean seasonal precipitation, mean maximum temperature of the warmest month and minimum temperature of the coldest month and response variables (presence/absence of pastures to be used as model predictors. Random forest model resulted robust and coherent to simulate pastureland suitability under current climatology (classification accuracy error=19%. Accordingly, results indicated that increases in temperatures coupled with decreases in precipitation, as simulated by HadCM3 in the future, would have impacts of great concern on potential pasture distribution. In the specific, an overall decline of pasturelands suitability is predicted by the middle of the century in both A2 (–46% and B2 (–41% along the entire chain. However, despite alarming reductions in pastures suitability along the northern (–69% and –71% under A2 and B2 scenarios, respectively and central Apennines (–90% under both scenarios by the end of the century, expansions are predicted along the southern areas of the chain (+96% and +105% under A2 and B2 scenarios, respectively. This may be probably due to expansions in pastures dominated by xeric and thermophiles species, which will likely benefit from warmer and drier future conditions predicted in the southern zone of the chain by the HadCM3. Hence, the expected climate, coupled with an increasing abandonment of the

  7. Impact of climate fluctuations on deposition of DDT and hexachlorocyclohexane in mountain glaciers: Evidence from ice core records

    International Nuclear Information System (INIS)

    Wang Xiaoping; Gong Ping; Zhang, Qianggong; Yao Tandong

    2010-01-01

    How do climate fluctuations affect DDT and hexachlorocyclohexane (HCH) distribution in the global scale? In this study, the interactions between climate variations and depositions of DDT and HCH in ice cores from Mt. Everest (the Tibetan Plateau), Mt. Muztagata (the eastern Pamirs) and the Rocky Mountains were investigated. All data regarding DDT/HCH deposition were obtained from the published results. Concentrations of DDT and HCH in an ice core from Mt. Everest were associated with the El Nino-Southern Oscillation. Concentrations of DDT in an ice core from Mt. Muztagata were significantly correlated with the Siberia High pattern. Concentrations of HCH in an ice core from Snow Dome of the Rocky Mountains responded to the North Atlantic Oscillation. These associations suggested that there are some linkages between climate variations and the global distribution of persistent organic pollutants. - Our study approves the potential contribution of ice core records of POPs to transport mechanisms of POPs.

  8. Climate-change-driven accelerated sea-level rise detected in the altimeter era.

    Science.gov (United States)

    Nerem, R S; Beckley, B D; Fasullo, J T; Hamlington, B D; Masters, D; Mitchum, G T

    2018-02-27

    Using a 25-y time series of precision satellite altimeter data from TOPEX/Poseidon, Jason-1, Jason-2, and Jason-3, we estimate the climate-change-driven acceleration of global mean sea level over the last 25 y to be 0.084 ± 0.025 mm/y 2 Coupled with the average climate-change-driven rate of sea level rise over these same 25 y of 2.9 mm/y, simple extrapolation of the quadratic implies global mean sea level could rise 65 ± 12 cm by 2100 compared with 2005, roughly in agreement with the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (AR5) model projections. Copyright © 2018 the Author(s). Published by PNAS.

  9. Are fish outside their usual ranges early indicators of climate-driven range shifts?

    Science.gov (United States)

    Fogarty, Hannah E; Burrows, Michael T; Pecl, Gretta T; Robinson, Lucy M; Poloczanska, Elvira S

    2017-05-01

    Shifts in species ranges are a global phenomenon, well known to occur in response to a changing climate. New species arriving in an area may become pest species, modify ecosystem structure, or represent challenges or opportunities for fisheries and recreation. Early detection of range shifts and prompt implementation of any appropriate management strategies is therefore crucial. This study investigates whether 'first sightings' of marine species outside their normal ranges could provide an early warning of impending climate-driven range shifts. We examine the relationships between first sightings and marine regions defined by patterns of local climate velocities (calculated on a 50-year timescale), while also considering the distribution of observational effort (i.e. number of sampling days recorded with biological observations in global databases). The marine trajectory regions include climate 'source' regions (areas lacking connections to warmer areas), 'corridor' regions (areas where moving isotherms converge), and 'sink' regions (areas where isotherms locally disappear). Additionally, we investigate the latitudinal band in which first sightings were recorded, and species' thermal affiliations. We found that first sightings are more likely to occur in climate sink and 'divergent' regions (areas where many rapid and diverging climate trajectories pass through) indicating a role of temperature in driving changes in marine species distributions. The majority of our fish first sightings appear to be tropical and subtropical species moving towards high latitudes, as would be expected in climate warming. Our results indicate that first sightings are likely related to longer-term climatic processes, and therefore have potential use to indicate likely climate-driven range shifts. The development of an approach to detect impending range shifts at an early stage will allow resource managers and researchers to better manage opportunities resulting from range

  10. A Data-Driven Assessment of the Sensitivity of Global Ecosystems to Climate Anomalies

    Science.gov (United States)

    Miralles, D. G.; Papagiannopoulou, C.; Demuzere, M.; Decubber, S.; Waegeman, W.; Verhoest, N.; Dorigo, W.

    2017-12-01

    Vegetation is a central player in the climate system, constraining atmospheric conditions through a series of feedbacks. This fundamental role highlights the importance of understanding regional drivers of ecological sensitivity and the response of vegetation to climatic changes. While nutrient availability and short-term disturbances can be crucial for vegetation at various spatiotemporal scales, natural vegetation dynamics are overall driven by climate. At monthly scales, the interactions between vegetation and climate become complex: some vegetation types react preferentially to specific climatic changes, with different levels of intensity, resilience and lagged response. For our current Earth System Models (ESMs) being able to capture this complexity is crucial but extremely challenging. This adds uncertainty to our projections of future climate and the fate of global ecosystems. Here, following a Granger causality framework based on a non-linear random forest predictive model, we exploit the current wealth of satellite data records to uncover the main climatic drivers of monthly vegetation variability globally. Results based on three decades of satellite data indicate that water availability is the most dominant factor driving vegetation in over 60% of the vegetated land. This overall dependency of ecosystems on water availability is larger than previously reported, partly owed to the ability of our machine-learning framework to disentangle the co-linearites between climatic drivers, and to quantify non-linear impacts of climate on vegetation. Our observation-based results are then used to benchmark ESMs on their representation of vegetation sensitivity to climate and climatic extremes. Our findings indicate that the sensitivity of vegetation to climatic anomalies is ill-reproduced by some widely-used ESMs.

  11. The Medieval Climate Anomaly and Byzantium: A review of the evidence on climatic fluctuations, economic performance and societal change

    Science.gov (United States)

    Xoplaki, Elena; Fleitmann, Dominik; Luterbacher, Juerg; Wagner, Sebastian; Haldon, John F.; Zorita, Eduardo; Telelis, Ioannis; Toreti, Andrea; Izdebski, Adam

    2016-04-01

    At the beginning of the Medieval Climate Anomaly, in the ninth and tenth century, the medieval eastern Roman empire, more usually known as Byzantium, was recovering from its early medieval crisis and experiencing favourable climatic conditions for the agricultural and demographic growth. Although in the Balkans and Anatolia such favourable climate conditions were prevalent during the eleventh century, parts of the imperial territories were facing significant challenges as a result of external political/military pressure. The apogee of medieval Byzantine socio-economic development, around AD 1150, coincides with a period of adverse climatic conditions for its economy, so it becomes obvious that the winter dryness and high climate variability at this time did not hinder Byzantine society and economy from achieving that level of expansion. Soon after this peak, towards the end of the twelfth century, the populations of the Byzantine world were experiencing unusual climatic conditions with marked dryness and cooler phases. The weakened Byzantine socio-political system must have contributed to the events leading to the fall of Constantinople in AD 1204 and the sack of the city. The final collapse of the Byzantine political control over western Anatolia took place half century later, thus contemporaneous with the strong cooling effect after a tropical volcanic eruption in AD 1257. We suggest that, regardless of a range of other influential factors, climate change was also an important contributing factor to the socio-economic changes that took place in Byzantium during the Medieval Climate Anomaly. Crucially, therefore, while the relatively sophisticated and complex Byzantine society was certainly influenced by climatic conditions, and while it nevertheless displayed a significant degree of resilience, external pressures as well as tensions within the Byzantine society more broadly contributed to an increasing vulnerability in respect of climate impacts. Our

  12. Early Holocene hydroclimate of Baffin Bay: Understanding the interplay between abrupt climate change events and ice sheet fluctuations

    Science.gov (United States)

    Corcoran, M. C.; Thomas, E. K.; Castañeda, I. S.; Briner, J. P.

    2017-12-01

    Understanding the causes of ice sheet fluctuations resulting in sea level rise is essential in today's warming climate. In high-latitude ice-sheet-proximal environments such as Baffin Bay, studying both the cause and the rate of ice sheet variability during past abrupt climate change events aids in predictions. Past climate reconstructions are used to understand ice sheet responses to changes in temperature and precipitation. The 9,300 and 8,200 yr BP events are examples of abrupt climate change events in the Baffin Bay region during which there were multiple re-advances of the Greenland and Laurentide ice sheets. High-resolution (decadal-scale) hydroclimate variability near the ice sheet margins during these abrupt climate change events is still unknown. We will generate a decadal-scale record of early Holocene temperature and precipitation using leaf wax hydrogen isotopes, δ2Hwax, from a lake sediment archive on Baffin Island, western Baffin Bay, to better understand abrupt climate change in this region. Shifts in temperature and moisture source result in changes in environmental water δ2H, which in turn is reflected in δ2Hwax, allowing for past hydroclimate to be determined from these compound-specific isotopes. The combination of terrestrial and aquatic δ2Hwax is used to determine soil evaporation and is ultimately used to reconstruct moisture variability. We will compare our results with a previous analysis of δ2Hwax and branched glycerol dialkyl glycerol tetraethers, a temperature and pH proxy, in lake sediment from western Greenland, eastern Baffin Bay, which indicates that cool and dry climate occurred in response to freshwater forcing events in the Labrador Sea. Reconstructing and comparing records on both the western and eastern sides of Baffin Bay during the early Holocene will allow for a spatial understanding of temperature and moisture balance changes during abrupt climate events, aiding in ice sheet modeling and predictions of future sea level

  13. Scenario and modelling uncertainty in global mean temperature change derived from emission driven Global Climate Models

    Science.gov (United States)

    Booth, B. B. B.; Bernie, D.; McNeall, D.; Hawkins, E.; Caesar, J.; Boulton, C.; Friedlingstein, P.; Sexton, D.

    2012-09-01

    We compare future changes in global mean temperature in response to different future scenarios which, for the first time, arise from emission driven rather than concentration driven perturbed parameter ensemble of a Global Climate Model (GCM). These new GCM simulations sample uncertainties in atmospheric feedbacks, land carbon cycle, ocean physics and aerosol sulphur cycle processes. We find broader ranges of projected temperature responses arising when considering emission rather than concentration driven simulations (with 10-90 percentile ranges of 1.7 K for the aggressive mitigation scenario up to 3.9 K for the high end business as usual scenario). A small minority of simulations resulting from combinations of strong atmospheric feedbacks and carbon cycle responses show temperature increases in excess of 9 degrees (RCP8.5) and even under aggressive mitigation (RCP2.6) temperatures in excess of 4 K. While the simulations point to much larger temperature ranges for emission driven experiments, they do not change existing expectations (based on previous concentration driven experiments) on the timescale that different sources of uncertainty are important. The new simulations sample a range of future atmospheric concentrations for each emission scenario. Both in case of SRES A1B and the Representative Concentration Pathways (RCPs), the concentration pathways used to drive GCM ensembles lies towards the lower end of our simulated distribution. This design decision (a legecy of previous assessments) is likely to lead concentration driven experiments to under-sample strong feedback responses in concentration driven projections. Our ensemble of emission driven simulations span the global temperature response of other multi-model frameworks except at the low end, where combinations of low climate sensitivity and low carbon cycle feedbacks lead to responses outside our ensemble range. The ensemble simulates a number of high end responses which lie above the CMIP5 carbon

  14. Short-term climatic fluctuations and the interpretation of recent observations in terms of greenhouse effect

    International Nuclear Information System (INIS)

    Andre, J.C.; Royer, J.F.

    1999-01-01

    Simulations of future climate made with coupled general circulation models of the atmosphere and ocean predict that the increase of the concentration of greenhouse gases released in the atmosphere by man's activities will have a large influence on the climate of the next century. The identification of the climatic impact produced by the rapid increase in carbon dioxide concentration in the last decades is made difficult by strong inter-annual climate variability, and requires the application of statistical techniques combining several climatic indicators (method of climatic 'fingerprints') so as to improve the detection of a possible anthropogenic perturbation. In this paper we review the evolution through the last decades of several climate indicators showing global warming, its geographical distribution, sea level, the hydrological cycle and the response of vegetation, and we compare them to the model results predicted in climate scenarios. The coherence between model results and observed climatic trends shows that the additional greenhouse effect is starting to become detectable in recent climatic data. (authors)

  15. Climatic and land-use driven change of runoff throughout Sweden

    Science.gov (United States)

    Worman, A. L. E.; Riml, J.; Lindstrom, G.

    2015-12-01

    Changes in runoff can be caused by climatic variations, land-use changes and water regulation. In this paper we propose a separation of the power spectral response of runoff in watersheds in terms of the product of the power spectra of precipitation and the impulse response function for the watershed. This allows a formal separation of the spectral response in climatic factors - the precipitation - from those of land-use change and regulation - the impulse response function. The latter function characterizes the surface water-groundwater interaction, stream network topology and open channel hydraulics. Based on daily data of digitalized hydro-climatological data from 1961, we constructed synthetic, but calibrated data of runoff from 1001 watersheds in Sweden. From spectral analysis of the data we found periodic fluctuations occurring on time scales of about a decade and a bi-annual peak. These multi-annual fluctuations could be statistically linked through the coherence spectra to climatic indices like the NAO, PDO, geostrophic wind velocity and sun spot numbers on common periods of 3,6 and 7,6 years. Such long-term fluctuations in runoff are not significantly affected by the land-use or regulation other than indirectly through impact on local hydro-climate. Based on a spectral separation of precipitation and impulse response function of the watersheds, we found that the intra-annual variation in runoff was primarily affected by the land-use change in 79 unregulated catchments with up to century-long time series of measured daily discharge. There is a statistically significant increasing slope of the catchments impulse response function for 63 of the 79 catchments and this suggest a significant hydrological effect of land-use practice in agriculture, urbanisation and forestry.

  16. Climate-driven introduction of the Black Death and successive plague reintroductions into Europe

    Czech Academy of Sciences Publication Activity Database

    Schmid, B. V.; Büntgen, Ulf; Easterday, W. R.; Ginzler, Ch.; Walloe, L.; Bramanti, B.; Stenseth, N. C.

    2015-01-01

    Roč. 112, č. 10 (2015), s. 3020-3025 ISSN 0027-8424 Institutional support: RVO:67179843 Keywords : yersinia-pestis * xenopsylla-cheopis * bubonic plague * central-asia * synchrony * dynamics * transmission * temperature * populations * thresholds * Yersinia pestis * medieval epidemiology * climate-driven disease dynamics Subject RIV: EH - Ecology, Behaviour Impact factor: 9.423, year: 2015 http://www.pnas.org/content/112/10/3020.full.pdf

  17. Multi-scale response of runoff to climate fluctuation in the headwater region of Kaidu River in Xinjiang of China

    Science.gov (United States)

    Bai, Ling; Chen, Zhongsheng; Xu, Jianhua; Li, Weihong

    2016-08-01

    Based on the hydrological and meteorological data in the headwater region of the Kaidu River during 1960-2009, the multi-scale characteristics of runoff variability were analyzed using the ensemble empirical mode decomposition method (EEMD), and the aim is to investigate the oscillation mode structure characteristics of runoff change and its response to climate fluctuation at different time scales. Results indicated that in the past 50 years, the overall runoff of Kaidu River in Xinjiang has showed a significant nonlinear upward trend, and its changes have obviously exhibited an inter-annual scale (quasi-3 and quasi-6-year) and inter-decadal scale (quasi-10 and quasi-25-year). Variance contribution rates of each component manifested that the inter-decadal change had been playing a more important role in the overall runoff change for Kaidu River, and the reconstructed inter-annual variation trend could describe the fluctuation state of the original runoff anomaly during the study period. The reconstructed inter-decadal variability effectively revealed that the runoff for Kaidu River changed over the years, namely the states of abundance and low water period appear alternately. In addition, we found that runoff has a positive correlation to precipitation and temperature at different time scales, but they are most significant and relevant at inter-decadal scale, indicating the inter-decadal scale is most suitable for investigating the responses of runoff dynamics to climate fluctuation. At the same time, the results also suggested that EEMD is an effective method to analyze the multi-scale characteristics of nonlinear and non-stationary signal.

  18. Overfishing reduces resilience of kelp beds to climate-driven catastrophic phase shift.

    Science.gov (United States)

    Ling, S D; Johnson, C R; Frusher, S D; Ridgway, K R

    2009-12-29

    A key consideration in assessing impacts of climate change is the possibility of synergistic effects with other human-induced stressors. In the ocean realm, climate change and overfishing pose two of the greatest challenges to the structure and functioning of marine ecosystems. In eastern Tasmania, temperate coastal waters are warming at approximately four times the global ocean warming average, representing the fastest rate of warming in the Southern Hemisphere. This has driven range extension of the ecologically important long-spined sea urchin (Centrostephanus rodgersii), which has now commenced catastrophic overgrazing of productive Tasmanian kelp beds leading to loss of biodiversity and important rocky reef ecosystem services. Coincident with the overgrazing is heavy fishing of reef-based predators including the spiny lobster Jasus edwardsii. By conducting experiments inside and outside Marine Protected Areas we show that fishing, by removing large predatory lobsters, has reduced the resilience of kelp beds against the climate-driven threat of the sea urchin and thus increased risk of catastrophic shift to widespread sea urchin barrens. This shows that interactions between multiple human-induced stressors can exacerbate nonlinear responses of ecosystems to climate change and limit the adaptive capacity of these systems. Management actions focused on reducing the risk of catastrophic phase shift in ecosystems are particularly urgent in the face of ongoing warming and unprecedented levels of predator removal from the world's oceans.

  19. Contemporary white-band disease in Caribbean corals driven by climate change

    Science.gov (United States)

    Randall, C. J.; van Woesik, R.

    2015-04-01

    Over the past 40 years, two of the dominant reef-building corals in the Caribbean, Acropora palmata and Acropora cervicornis, have experienced unprecedented declines. That loss has been largely attributed to a syndrome commonly referred to as white-band disease. Climate change-driven increases in sea surface temperature (SST) have been linked to several coral diseases, yet, despite decades of research, the attribution of white-band disease to climate change remains unknown. Here we hindcasted the potential relationship between recent ocean warming and outbreaks of white-band disease on acroporid corals. We quantified eight SST metrics, including rates of change in SST and contemporary thermal anomalies, and compared them with records of white-band disease on A. palmata and A. cervicornis from 473 sites across the Caribbean, surveyed from 1997 to 2004. The results of our models suggest that decades-long climate-driven changes in SST, increases in thermal minima, and the breach of thermal maxima have all played significant roles in the spread of white-band disease. We conclude that white-band disease has been strongly coupled with thermal stresses associated with climate change, which has contributed to the regional decline of these once-dominant reef-building corals.

  20. The demography of climate-driven and density-regulated population dynamics in a perennial plant

    DEFF Research Database (Denmark)

    Dahlgren, Johan; Bengstsson, Karin; Ehrlén, Johan

    2016-01-01

    Identifying the internal and external drivers of population dynamics is a key objective in ecology, currently accentuated by the need to forecast the effects of climate change on species distributions and abundances. The interplay between environmental and density effects is one particularly...... important aspect of such forecasts. We examined the simultaneous impact of climate and intraspecific density on vital rates of the dwarf shrub Fumana procumbens over 20 yr, using generalized additive mixed models. We then analyzed effects on population dynamics using integral projection models...... to be driven solely by the environment can overestimate extinction risks if there is density dependence. We conclude that density regulation can dampen effects of climate change on Fumana population size, and discuss the need to quantify density dependence in predictions of population responses...

  1. The influence of coral reefs and climate change on wave-driven flooding of tropical coastlines

    Science.gov (United States)

    Quataert, Ellen; Storlazzi, Curt; van Rooijen, Arnold; van Dongeren, Ap; Cheriton, Olivia

    2015-01-01

    A numerical model, XBeach, calibrated and validated on field data collected at Roi-Namur Island on Kwajalein Atoll in the Republic of Marshall Islands, was used to examine the effects of different coral reef characteristics on potential coastal hazards caused by wave-driven flooding and how these effects may be altered by projected climate change. The results presented herein suggest that coasts fronted by relatively narrow reefs with steep fore reef slopes (~1:10 and steeper) and deeper, smoother reef flats are expected to experience the highest wave runup. Wave runup increases for higher water levels (sea level rise), higher waves, and lower bed roughness (coral degradation), which are all expected effects of climate change. Rising sea levels and climate change will therefore have a significant negative impact on the ability of coral reefs to mitigate the effects of coastal hazards in the future.

  2. The influence of coral reefs and climate change on wave-driven flooding of tropical coastlines

    Science.gov (United States)

    Quataert, Ellen; Storlazzi, Curt; Rooijen, Arnold; Cheriton, Olivia; Dongeren, Ap

    2015-08-01

    A numerical model, XBeach, calibrated and validated on field data collected at Roi-Namur Island on Kwajalein Atoll in the Republic of Marshall Islands, was used to examine the effects of different coral reef characteristics on potential coastal hazards caused by wave-driven flooding and how these effects may be altered by projected climate change. The results presented herein suggest that coasts fronted by relatively narrow reefs with steep fore reef slopes (~1:10 and steeper) and deeper, smoother reef flats are expected to experience the highest wave runup. Wave runup increases for higher water levels (sea level rise), higher waves, and lower bed roughness (coral degradation), which are all expected effects of climate change. Rising sea levels and climate change will therefore have a significant negative impact on the ability of coral reefs to mitigate the effects of coastal hazards in the future.

  3. Disentangling the effects of feedback structure and climate on Poaceae annual airborne pollen fluctuations and the possible consequences of climate change.

    Science.gov (United States)

    García de León, David; García-Mozo, Herminia; Galán, Carmen; Alcázar, Purificación; Lima, Mauricio; González-Andújar, José L

    2015-10-15

    Pollen allergies are the most common form of respiratory allergic disease in Europe. Most studies have emphasized the role of environmental processes, as the drivers of airborne pollen fluctuations, implicitly considering pollen production as a random walk. This work shows that internal self-regulating processes of the plants (negative feedback) should be included in pollen dynamic systems in order to give a better explanation of the observed pollen temporal patterns. This article proposes a novel methodological approach based on dynamic systems to investigate the interaction between feedback structure of plant populations and climate in shaping long-term airborne Poaceae pollen fluctuations and to quantify the effects of climate change on future airborne pollen concentrations. Long-term historical airborne Poaceae pollen data (30 years) from Cordoba city (Southern Spain) were analyzed. A set of models, combining feedback structure, temperature and actual evapotranspiration effects on airborne Poaceae pollen were built and compared, using a model selection approach. Our results highlight the importance of first-order negative feedback and mean annual maximum temperature in driving airborne Poaceae pollen dynamics. The best model was used to predict the effects of climate change under two standardized scenarios representing contrasting temporal patterns of economic development and CO2 emissions. Our results predict an increase in pollen levels in southern Spain by 2070 ranging from 28.5% to 44.3%. The findings from this study provide a greater understanding of airborne pollen dynamics and how climate change might impact the future evolution of airborne Poaceae pollen concentrations and thus the future evolution of related pollen allergies. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Greenness and Carbon Stocks of Mangroves: A climate-driven Effect

    Science.gov (United States)

    Lule, A. V.; Colditz, R. R.; Herrera-Silveira, J.; Guevara, M.; Rodriguez-Zuniga, M. T.; Cruz, I.; Ressl, R.; Vargas, R.

    2017-12-01

    Mangroves cover less than 1% of the earth's surface and are one o­­­f the most productive ecosystems of the world. They are highly vulnerable to climate variability due to their sensitivity to environmental changes; therefore, there are scientific and societal needs to designed frameworks to assess mangrove's vulnerability. We study the relationship between climate drivers, canopy greenness and carbon stocks to quantify a potential climate-driven effect on mangrove carbon dynamics. We identify greenness trends and their relationships with climate drivers and carbon stocks throughout 15 years (2001-2015) across mangrove forests of Mexico. We defined several categories for mangroves: a) Arid mangroves with superficial water input (ARsw); b) Humid mangroves with interior or underground water input (HUiw); and c) Humid mangroves with superficial water input (HUsw). We found a positive significant trend of greenness for ARsw and HUsw categories (pmangrove's categories (pmangrove categories showed higher greenness values during winter; which is likely driven by temperature with a lag of -3 to -5 months (r2 > 0.69). Precipitation and temperature drive canopy greenness only across HUsw. Regarding carbon stocks, the HUiw shows the lower amount of aboveground carbon (AGC; 12.7 Mg C ha-1) and the higher belowground carbon (BGC; 219 Mg C ha-1). The HUsw shows the higher amount of AGC (169.5 Mg C ha-1) and the ARsw the lower of BGC (92.4 Mg C ha-1). Climate drivers are better related with canopy greenness and AGC for both humid mangrove categories (r2 > 0.48), while the relationship of BGC and canopy greenness is lower for all categories (r2 mangrove's ecosystem function and environmental services, as well as their potential vulnerability to climate variability.

  5. Managing uncertainty in climate-driven ecological models to inform adaptation to climate change

    Science.gov (United States)

    Jeremy S. Littell; Donald McKenzie; Becky K. Kerns; Samuel Cushman; Charles G. Shaw

    2011-01-01

    The impacts of climate change on forest ecosystems are likely to require changes in forest planning and natural resource management. Changes in tree growth, disturbance extent and intensity, and eventually species distributions are expected. In natural resource management and planning, ecosystem models are typically used to provide a "best estimate" about how...

  6. Is the number and size of scales in Liolaemus lizards driven by climate?

    Science.gov (United States)

    José Tulli, María; Cruz, Félix B

    2018-05-03

    Ectothermic vertebrates are sensitive to thermal fluctuations in the environments where they occur. To buffer these fluctuations, ectotherms use different strategies, including the integument, which is a barrier that minimizes temperature exchange between the inner body and the surrounding air. In lizards, this barrier is constituted by keratinized scales of variable size, shape and texture, and its main function is protection, water loss avoidance and thermoregulation. The size of scales in lizards has been proposed to vary in relation to climatic gradients; however, it has also been observed that in some groups of Iguanian lizards could be related to phylogeny. Thus, here, we studied the area and number of scales (dorsal and ventral) of 61 species of Liolaemus lizards distributed in a broad latitudinal and altitudinal gradient to determine the nature of the variation of the scales with climate, and found that the number and size of scales are related to climatic variables, such as temperature and geographical variables as altitude. The evolutionary process that better explained how these morphological variables evolved was the Ornstein-Uhlenbeck model. The number of scales seemed to be related to common ancestry, whereas dorsal and ventral scale areas seemed to vary as a consequence of ecological traits. In fact, the ventral area is less exposed to climate conditions such as ultraviolet radiation or wind and is thus under less pressure to change in response to alterations in external conditions. It is possible that scale ornamentation such as keels and granulosity may bring some more information in this regard. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  7. Climate Change driven evolution of hazards to Europe's transport infrastructure throughout the twenty-first century

    Science.gov (United States)

    Matulla, Christoph; Hollósi, Brigitta; Andre, Konrad; Gringinger, Julia; Chimani, Barbara; Namyslo, Joachim; Fuchs, Tobias; Auerbach, Markus; Herrmann, Carina; Sladek, Brigitte; Berghold, Heimo; Gschier, Roland; Eichinger-Vill, Eva

    2017-06-01

    Road authorities, freight, and logistic industries face a multitude of challenges in a world changing at an ever growing pace. While globalization, changes in technology, demography, and traffic, for instance, have received much attention over the bygone decades, climate change has not been treated with equal care until recently. However, since it has been recognized that climate change jeopardizes many business areas in transport, freight, and logistics, research programs investigating future threats have been initiated. One of these programs is the Conference of European Directors of Roads' (CEDR) Transnational Research Programme (TRP), which emerged about a decade ago from a cooperation between European National Road Authorities and the EU. This paper presents findings of a CEDR project called CliPDaR, which has been designed to answer questions from road authorities concerning climate-driven future threats to transport infrastructure. Pertaining results are based on two potential future socio-economic pathways of mankind (one strongly economically oriented "A2" and one more balanced scenario "A1B"), which are used to drive global climate models (GCMs) producing global and continental scale climate change projections. In order to achieve climate change projections, which are valid on regional scales, GCM projections are downscaled by regional climate models. Results shown here originate from research questions raised by European Road Authorities. They refer to future occurrence frequencies of severely cold winter seasons in Fennoscandia, to particularly hot summer seasons in the Iberian Peninsula and to changes in extreme weather phenomena triggering landslides and rutting in Central Europe. Future occurrence frequencies of extreme winter and summer conditions are investigated by empirical orthogonal function analyses of GCM projections driven with by A2 and A1B pathways. The analysis of future weather phenomena triggering landslides and rutting events requires

  8. Holocene fluctuations in human population demonstrate repeated links to food production and climate.

    Science.gov (United States)

    Bevan, Andrew; Colledge, Sue; Fuller, Dorian; Fyfe, Ralph; Shennan, Stephen; Stevens, Chris

    2017-12-05

    We consider the long-term relationship between human demography, food production, and Holocene climate via an archaeological radiocarbon date series of unprecedented sampling density and detail. There is striking consistency in the inferred human population dynamics across different regions of Britain and Ireland during the middle and later Holocene. Major cross-regional population downturns in population coincide with episodes of more abrupt change in North Atlantic climate and witness societal responses in food procurement as visible in directly dated plants and animals, often with moves toward hardier cereals, increased pastoralism, and/or gathered resources. For the Neolithic, this evidence questions existing models of wholly endogenous demographic boom-bust. For the wider Holocene, it demonstrates that climate-related disruptions have been quasi-periodic drivers of societal and subsistence change. Copyright © 2017 the Author(s). Published by PNAS.

  9. Climate-driven changes in functional biogeography of Arctic marine fish communities.

    Science.gov (United States)

    Frainer, André; Primicerio, Raul; Kortsch, Susanne; Aune, Magnus; Dolgov, Andrey V; Fossheim, Maria; Aschan, Michaela M

    2017-11-14

    Climate change triggers poleward shifts in species distribution leading to changes in biogeography. In the marine environment, fish respond quickly to warming, causing community-wide reorganizations, which result in profound changes in ecosystem functioning. Functional biogeography provides a framework to address how ecosystem functioning may be affected by climate change over large spatial scales. However, there are few studies on functional biogeography in the marine environment, and none in the Arctic, where climate-driven changes are most rapid and extensive. We investigated the impact of climate warming on the functional biogeography of the Barents Sea, which is characterized by a sharp zoogeographic divide separating boreal from Arctic species. Our unique dataset covered 52 fish species, 15 functional traits, and 3,660 stations sampled during the recent warming period. We found that the functional traits characterizing Arctic fish communities, mainly composed of small-sized bottom-dwelling benthivores, are being rapidly replaced by traits of incoming boreal species, particularly the larger, longer lived, and more piscivorous species. The changes in functional traits detected in the Arctic can be predicted based on the characteristics of species expected to undergo quick poleward shifts in response to warming. These are the large, generalist, motile species, such as cod and haddock. We show how functional biogeography can provide important insights into the relationship between species composition, diversity, ecosystem functioning, and environmental drivers. This represents invaluable knowledge in a period when communities and ecosystems experience rapid climate-driven changes across biogeographical regions. Copyright © 2017 the Author(s). Published by PNAS.

  10. Climate fluctuations of tropical coupled systems — The role of ocean dynamics

    Digital Repository Service at National Institute of Oceanography (India)

    Chang, P.; Yamagata, T.; Schopf, P.; Behera, S.K.; Carton, J.; Kessler, W.S.; Meyers, G.; Qu, T.; Schott, F.; Shetye, S.R.; Xie, S.P.

    on the active role of ocean dynamics in a seasonally locked east-west internal mode of variability, known as the Indian Ocean Dipole (IOD). We discuss influences of the IOD on climatic conditions in Asia, Australia, East Africa and Europe. While the attempt...

  11. Sensitivity of Water Scarcity Events to ENSO-Driven Climate Variability at the Global Scale

    Science.gov (United States)

    Veldkamp, T. I. E.; Eisner, S.; Wada, Y.; Aerts, J. C. J. H.; Ward, P. J.

    2015-01-01

    Globally, freshwater shortage is one of the most dangerous risks for society. Changing hydro-climatic and socioeconomic conditions have aggravated water scarcity over the past decades. A wide range of studies show that water scarcity will intensify in the future, as a result of both increased consumptive water use and, in some regions, climate change. Although it is well-known that El Niño- Southern Oscillation (ENSO) affects patterns of precipitation and drought at global and regional scales, little attention has yet been paid to the impacts of climate variability on water scarcity conditions, despite its importance for adaptation planning. Therefore, we present the first global-scale sensitivity assessment of water scarcity to ENSO, the most dominant signal of climate variability. We show that over the time period 1961-2010, both water availability and water scarcity conditions are significantly correlated with ENSO-driven climate variability over a large proportion of the global land area (> 28.1 %); an area inhabited by more than 31.4% of the global population. We also found, however, that climate variability alone is often not enough to trigger the actual incidence of water scarcity events. The sensitivity of a region to water scarcity events, expressed in terms of land area or population exposed, is determined by both hydro-climatic and socioeconomic conditions. Currently, the population actually impacted by water scarcity events consists of 39.6% (CTA: consumption-to-availability ratio) and 41.1% (WCI: water crowding index) of the global population, whilst only 11.4% (CTA) and 15.9% (WCI) of the global population is at the same time living in areas sensitive to ENSO-driven climate variability. These results are contrasted, however, by differences in growth rates found under changing socioeconomic conditions, which are relatively high in regions exposed to water scarcity events. Given the correlations found between ENSO and water availability and scarcity

  12. Effect of quantum lattice fluctuations on quantum coherent oscillations in a coherently driven quantum dot-cavity system

    International Nuclear Information System (INIS)

    Zhu, Ka-Di; Li, Wai-Sang

    2003-01-01

    The quantum coherent oscillations in a coherently driven quantum dot-cavity system with the presence of strong exciton-phonon interactions are investigated theoretically in a fully quantum treatment. It is shown that even at zero temperature, the strong exciton-phonon interactions still affect the quantum coherent oscillations significantly

  13. Millennial climatic fluctuations are key to the structure of last glacial ecosystems.

    Directory of Open Access Journals (Sweden)

    Brian Huntley

    Full Text Available Whereas fossil evidence indicates extensive treeless vegetation and diverse grazing megafauna in Europe and northern Asia during the last glacial, experiments combining vegetation models and climate models have to-date simulated widespread persistence of trees. Resolving this conflict is key to understanding both last glacial ecosystems and extinction of most of the mega-herbivores. Using a dynamic vegetation model (DVM we explored the implications of the differing climatic conditions generated by a general circulation model (GCM in "normal" and "hosing" experiments. Whilst the former approximate interstadial conditions, the latter, designed to mimic Heinrich Events, approximate stadial conditions. The "hosing" experiments gave simulated European vegetation much closer in composition to that inferred from fossil evidence than did the "normal" experiments. Given the short duration of interstadials, and the rate at which forest cover expanded during the late-glacial and early Holocene, our results demonstrate the importance of millennial variability in determining the character of last glacial ecosystems.

  14. Millennial climatic fluctuations are key to the structure of last glacial ecosystems.

    Science.gov (United States)

    Huntley, Brian; Allen, Judy R M; Collingham, Yvonne C; Hickler, Thomas; Lister, Adrian M; Singarayer, Joy; Stuart, Anthony J; Sykes, Martin T; Valdes, Paul J

    2013-01-01

    Whereas fossil evidence indicates extensive treeless vegetation and diverse grazing megafauna in Europe and northern Asia during the last glacial, experiments combining vegetation models and climate models have to-date simulated widespread persistence of trees. Resolving this conflict is key to understanding both last glacial ecosystems and extinction of most of the mega-herbivores. Using a dynamic vegetation model (DVM) we explored the implications of the differing climatic conditions generated by a general circulation model (GCM) in "normal" and "hosing" experiments. Whilst the former approximate interstadial conditions, the latter, designed to mimic Heinrich Events, approximate stadial conditions. The "hosing" experiments gave simulated European vegetation much closer in composition to that inferred from fossil evidence than did the "normal" experiments. Given the short duration of interstadials, and the rate at which forest cover expanded during the late-glacial and early Holocene, our results demonstrate the importance of millennial variability in determining the character of last glacial ecosystems.

  15. Spatially explicit integrated modeling and economic valuation of climate driven land use change and its indirect effects.

    OpenAIRE

    Bateman, Ian; Agarwala, M.; Binner, A.; Coombes, E.; Day, B.; Ferrini, Silvia; Fezzi, C.; Hutchins, M.; Lovett, A.; Posen, P.

    2016-01-01

    We present an integrated model of the direct consequences of climate change on land use, and the indirect effects of induced land use change upon the natural environment. The model predicts climate-driven shifts in the profitability of alternative uses of agricultural land. Both the direct impact of climate change and the induced shift in land use patterns will cause secondary effects on the water environment, for which agriculture is the major source of diffuse pollution. We model the impact...

  16. Climate fluctuations during the Holocene in NW Iberia: High and low latitude linkages

    Science.gov (United States)

    Pena, L. D.; Francés, G.; Diz, P.; Esparza, M.; Grimalt, J. O.; Nombela, M. A.; Alejo, I.

    2010-07-01

    High resolution benthic foraminiferal stable isotopes (δ 18O, δ 13C) and molecular biomarkers in the sediments are used here to infer rapid climatic changes for the last 8200 years in the Ría de Muros (NW Iberian Margin). Benthic foraminiferal δ 18O and δ 13C potentially register migrations in the position of the hydrographic front formed between two different intermediate water masses: Eastern North Atlantic Central Water of subpolar origin (ENACW sp) and subtropical origin (ENACW st). The molecular biomarkers in the sediment show a strong coupling between continental organic matter inputs and negative δ 13C values in benthic foraminifera. The rapid centennial and millennial events registered in these records have been compared with two well known North Atlantic Holocene records from the subtropical Atlantic sea surface temperatures (SST) anomalies off Cape Blanc, NW Africa and the subpolar Atlantic (Hematite Stained Grains percentage, subpolar North Atlantic). Comparison supports a strong link between high- and low-latitude climatic perturbations at centennial-millennial time scales during the Holocene. Spectral analyses also points to a pole-to-equator propagation of the so-called 1500 yr cycles. Our results demonstrate that during the Holocene, the NW Iberian Margin has undergone a series of rapid events which are likely triggered at high latitudes in the North Atlantic and are rapidly propagated towards lower latitudes. Conceivably, the propagation of these rapid climatic changes involves a shift in atmospheric and oceanic circulatory systems.

  17. Climate-driven ichthyoplankton drift model predicts growth of top predator young.

    Science.gov (United States)

    Myksvoll, Mari S; Erikstad, Kjell E; Barrett, Robert T; Sandvik, Hanno; Vikebø, Frode

    2013-01-01

    Climate variability influences seabird population dynamics in several ways including access to prey near colonies during the critical chick-rearing period. This study addresses breeding success in a Barents Sea colony of common guillemots Uria aalge where trophic conditions vary according to changes in the northward transport of warm Atlantic Water. A drift model was used to simulate interannual variations in transport of cod Gadus morhua larvae along the Norwegian coast towards their nursery grounds in the Barents Sea. The results showed that the arrival of cod larvae from southern spawning grounds had a major effect on the size of common guillemot chicks at fledging. Furthermore, the fraction of larvae from the south was positively correlated to the inflow of Atlantic Water into the Barents Sea thus clearly demonstrating the mechanisms by which climate-driven bottom-up processes influence interannual variations in reproductive success in a marine top predator.

  18. Climate-driven ichthyoplankton drift model predicts growth of top predator young.

    Directory of Open Access Journals (Sweden)

    Mari S Myksvoll

    Full Text Available Climate variability influences seabird population dynamics in several ways including access to prey near colonies during the critical chick-rearing period. This study addresses breeding success in a Barents Sea colony of common guillemots Uria aalge where trophic conditions vary according to changes in the northward transport of warm Atlantic Water. A drift model was used to simulate interannual variations in transport of cod Gadus morhua larvae along the Norwegian coast towards their nursery grounds in the Barents Sea. The results showed that the arrival of cod larvae from southern spawning grounds had a major effect on the size of common guillemot chicks at fledging. Furthermore, the fraction of larvae from the south was positively correlated to the inflow of Atlantic Water into the Barents Sea thus clearly demonstrating the mechanisms by which climate-driven bottom-up processes influence interannual variations in reproductive success in a marine top predator.

  19. Evolution of the earliest horses driven by climate change in the Paleocene-Eocene Thermal Maximum.

    Science.gov (United States)

    Secord, Ross; Bloch, Jonathan I; Chester, Stephen G B; Boyer, Doug M; Wood, Aaron R; Wing, Scott L; Kraus, Mary J; McInerney, Francesca A; Krigbaum, John

    2012-02-24

    Body size plays a critical role in mammalian ecology and physiology. Previous research has shown that many mammals became smaller during the Paleocene-Eocene Thermal Maximum (PETM), but the timing and magnitude of that change relative to climate change have been unclear. A high-resolution record of continental climate and equid body size change shows a directional size decrease of ~30% over the first ~130,000 years of the PETM, followed by a ~76% increase in the recovery phase of the PETM. These size changes are negatively correlated with temperature inferred from oxygen isotopes in mammal teeth and were probably driven by shifts in temperature and possibly high atmospheric CO(2) concentrations. These findings could be important for understanding mammalian evolutionary responses to future global warming.

  20. How realistic are air quality hindcasts driven by forcings from climate model simulations?

    Science.gov (United States)

    Lacressonnière, G.; Peuch, V.-H.; Arteta, J.; Josse, B.; Joly, M.; Marécal, V.; Saint Martin, D.; Déqué, M.; Watson, L.

    2012-12-01

    Predicting how European air quality could evolve over the next decades in the context of changing climate requires the use of climate models to produce results that can be averaged in a climatologically and statistically sound manner. This is a very different approach from the one that is generally used for air quality hindcasts for the present period; analysed meteorological fields are used to represent specifically each date and hour. Differences arise both from the fact that a climate model run results in a pure model output, with no influence from observations (which are useful to correct for a range of errors), and that in a "climate" set-up, simulations on a given day, month or even season cannot be related to any specific period of time (but can just be interpreted in a climatological sense). Hence, although an air quality model can be thoroughly validated in a "realistic" set-up using analysed meteorological fields, the question remains of how far its outputs can be interpreted in a "climate" set-up. For this purpose, we focus on Europe and on the current decade using three 5-yr simulations performed with the multiscale chemistry-transport model MOCAGE and use meteorological forcings either from operational meteorological analyses or from climate simulations. We investigate how statistical skill indicators compare in the different simulations, discriminating also the effects of meteorology on atmospheric fields (winds, temperature, humidity, pressure, etc.) and on the dependent emissions and deposition processes (volatile organic compound emissions, deposition velocities, etc.). Our results show in particular how differing boundary layer heights and deposition velocities affect horizontal and vertical distributions of species. When the model is driven by operational analyses, the simulation accurately reproduces the observed values of O3, NOx, SO2 and, with some bias that can be explained by the set-up, PM10. We study how the simulations driven by climate

  1. Theropod Fauna from Southern Australia Indicates High Polar Diversity and Climate-Driven Dinosaur Provinciality

    Science.gov (United States)

    Benson, Roger B. J.; Rich, Thomas H.; Vickers-Rich, Patricia; Hall, Mike

    2012-01-01

    hallmark ‘Gondwanan’ fauna of South America and Africa may therefore reflect climate-driven provinciality, not vicariant evolution driven by continental fragmentation. However, vicariance may still be detected at lower phylogenetic levels. PMID:22615916

  2. Atoll groundwater movement and its response to climatic and sea-level fluctuations

    Science.gov (United States)

    Oberle, Ferdinand; Swarzenski, Peter W.; Storlazzi, Curt

    2017-01-01

    Groundwater resources of low-lying atoll islands are threatened due to short-term and long-term changes in rainfall, wave climate, and sea level. A better understanding of how these forcings affect the limited groundwater resources was explored on Roi-Namur in the Republic of the Marshall Islands. As part of a 16-month study, a rarely recorded island-overwash event occurred and the island’s aquifer’s response was measured. The findings suggest that small-scale overwash events cause an increase in salinity of the freshwater lens that returns to pre-overwash conditions within one month. The overwash event is addressed in the context of climate-related local sea-level change, which suggests that overwash events and associated degradations in freshwater resources are likely to increase in severity in the future due to projected rises in sea level. Other forcings, such as severe rainfall events, were shown to have caused a sudden freshening of the aquifer, with salinity levels retuning to pre-rainfall levels within three months. Tidal forcing of the freshwater lens was observed in electrical resistivity profiles, high-resolution conductivity, groundwater-level well measurements and through submarine groundwater discharge calculations. Depth-specific geochemical pore water measurements further assessed and confirmed the distinct boundaries between fresh and saline water masses in the aquifer. The identification of the freshwater lens’ saline boundaries is essential for a quantitative evaluation of the aquifers freshwater resources and help understand how these resources may be impacted by climate change and anthropogenic activities.

  3. Atoll Groundwater Movement and Its Response to Climatic and Sea-Level Fluctuations

    Directory of Open Access Journals (Sweden)

    Ferdinand K. J. Oberle

    2017-08-01

    Full Text Available Groundwater resources of low-lying atoll islands are threatened due to short-term and long-term changes in rainfall, wave climate, and sea level. A better understanding of how these forcings affect the limited groundwater resources was explored on Roi-Namur in the Republic of the Marshall Islands. As part of a 16-month study, a rarely recorded island-overwash event occurred and the island’s aquifer’s response was measured. The findings suggest that small-scale overwash events cause an increase in salinity of the freshwater lens that returns to pre-overwash conditions within one month. The overwash event is addressed in the context of climate-related local sea-level change, which suggests that overwash events and associated degradations in freshwater resources are likely to increase in severity in the future due to projected rises in sea level. Other forcings, such as severe rainfall events, were shown to have caused a sudden freshening of the aquifer, with salinity levels retuning to pre-rainfall levels within three months. Tidal forcing of the freshwater lens was observed in electrical resistivity profiles, high-resolution conductivity, groundwater-level well measurements and through submarine groundwater discharge calculations. Depth-specific geochemical pore water measurements further assessed and confirmed the distinct boundaries between fresh and saline water masses in the aquifer. The identification of the freshwater lens’ saline boundaries is essential for a quantitative evaluation of the aquifers freshwater resources and help understand how these resources may be impacted by climate change and anthropogenic activities.

  4. Little Ice Age climate reconstruction from ensemble reanalysis of Alpine glacier fluctuations

    Directory of Open Access Journals (Sweden)

    M. P. Lüthi

    2014-04-01

    Full Text Available Mountain glaciers sample a combination of climate fields – temperature, precipitation and radiation – by accumulation and melting of ice. Flow dynamics acts as a transfer function that maps volume changes to a length response of the glacier terminus. Long histories of terminus positions have been assembled for several glaciers in the Alps. Here I analyze terminus position histories from an ensemble of seven glaciers in the Alps with a macroscopic model of glacier dynamics to derive a history of glacier equilibrium line altitude (ELA for the time span 400–2010 C.E. The resulting climatic reconstruction depends only on records of glacier variations. The reconstructed ELA history is similar to recent reconstructions of Alpine summer temperature and Atlantic Multidecadal Oscillation (AMO index, but bears little resemblance to reconstructed precipitation variations. Most reconstructed low-ELA periods coincide with large explosive volcano eruptions, hinting at a direct effect of volcanic radiative cooling on mass balance. The glacier advances during the LIA, and the retreat after 1860, can thus be mainly attributed to temperature and volcanic radiative cooling.

  5. Climate driven range divergence among host species affects range-wide patterns of parasitism

    Directory of Open Access Journals (Sweden)

    Richard E. Feldman

    2017-01-01

    Full Text Available Species interactions like parasitism influence the outcome of climate-driven shifts in species ranges. For some host species, parasitism can only occur in that part of its range that overlaps with a second host species. Thus, predicting future parasitism may depend on how the ranges of the two hosts change in relation to each other. In this study, we tested whether the climate driven species range shift of Odocoileus virginianus (white-tailed deer accounts for predicted changes in parasitism of two other species from the family Cervidae, Alces alces (moose and Rangifer tarandus (caribou, in North America. We used MaxEnt models to predict the recent (2000 and future (2050 ranges (probabilities of occurrence of the cervids and a parasite Parelaphostrongylus tenuis (brainworm taking into account range shifts of the parasite’s intermediate gastropod hosts. Our models predicted that range overlap between A. alces/R. tarandus and P. tenuis will decrease between 2000 and 2050, an outcome that reflects decreased overlap between A. alces/R. tarandus and O. virginianus and not the parasites, themselves. Geographically, our models predicted increasing potential occurrence of P. tenuis where A. alces/R. tarandus are likely to decline, but minimal spatial overlap where A. alces/R. tarandus are likely to increase. Thus, parasitism may exacerbate climate-mediated southern contraction of A. alces and R. tarandus ranges but will have limited influence on northward range expansion. Our results suggest that the spatial dynamics of one host species may be the driving force behind future rates of parasitism for another host species.

  6. Both temperature fluctuations and East Asian monsoons have driven plant diversification in the karst ecosystems from southern China.

    Science.gov (United States)

    Kong, Hanghui; Condamine, Fabien L; Harris, A J; Chen, Junlin; Pan, Bo; Möller, Michael; Hoang, Van Sam; Kang, Ming

    2017-11-01

    Karst ecosystems in southern China are species-rich and have high levels of endemism, yet little is known regarding the evolutionary processes responsible for the origin and diversification of karst biodiversity. The genus Primulina (Gesneriaceae) comprises ca. 170 species endemic to southern China with high levels of ecological (edaphic) specialization, providing an exceptional model to study the plant diversification in karsts. We used molecular data from nine chloroplast and 11 nuclear regions and macroevolutionary analyses to assess the origin and cause of species diversification due to palaeoenvironmental changes and edaphic specialization in Primulina. We found that speciation was positively associated with changes in past temperatures and East Asian monsoons through the evolutionary history of Primulina. Climatic change around the mid-Miocene triggered an early burst followed by a slowdown of diversification rate towards the present with the climate cooling. We detected different speciation rates among edaphic types, and transitions among soil types were infrequently and did not impact the overall speciation rate. Our findings suggest that both global temperature changes and East Asian monsoons have played crucial roles in floristic diversification within the karst ecosystems in southern China, such that speciation was higher when climate was warmer and wetter. This is the first study to directly demonstrate that past monsoon activity is positively correlated with speciation rate in East Asia. This case study could motivate further investigations to assess the impacts of past environmental changes on the origin and diversification of biodiversity in global karst ecosystems, most of which are under threat. © 2017 John Wiley & Sons Ltd.

  7. Cross-site comparisons of concentration-discharge relationships reveal climate-driven chemostatic set points

    Science.gov (United States)

    Godsey, S.; Kirchner, J. W.

    2017-12-01

    Streamflow solute concentrations often vary predictably with flows, providing insight into processes controlling solute generation and export. Previous work by the authors showed that log-transformed concentration-discharge relationships of weathering-derived solutes in 59 headwater catchments had relatively low slopes, implying that these watersheds behaved almost like chemostats. That is, their rates of solute production and/or mobilization were nearly proportional to water fluxes, on both event and inter-annual time scales. Here we re-examine these findings using data from roughly 1000 catchments, ranging from ˜10 to >1,000,000 sq. km in drainage area, and spanning a wide range of lithologic and climatic settings.Concentration-discharge relationships among this much larger set of much larger catchments are broadly consistent with the chemostatic behavior described above. However, site-to-site variations in mean concentrations among these catchments are negatively correlated with long-term average precipitation and discharge, suggesting dilution of stream concentrations under long-term leaching of the critical zone. Thus, on event and inter-annual time scales, stream solute concentrations are chemostatically buffered by groundwater storage and fast chemical reactions (such as ion exchange), but on much longer time scales, the catchment's chemostatic "set point" is determined by climatically driven critical zone evolution. We present examples illustrating short-term and long-term controls on water quality consistent with variations in weather and climate, and discuss their implications.

  8. Performance Investigation of a Solar Heat Driven Adsorption Chiller under Two Different Climatic Conditions

    Science.gov (United States)

    Choudhury, Biplab; Chatterjee, Pradip Kumar; Habib, Khairul; Saha, Bidyut Baran

    2018-06-01

    The demand for cooling, especially in the developing economies, is rising at a fast rate. Fast-depleting sources of fossil fuel and environmental concerns necessitate looking for alternative cooling solutions. Solar heat driven adsorption based cooling cycles are environmentally friendly due to their use of natural refrigerants and the thermal compression process. In this paper, a performance simulation study of a basic two-bed solar adsorption chiller has been performed through a transient model for two different climatic locations in India. Effect of operating temperatures and cycle time on the chiller performance has been studied. It is observed that the solar hot water temperature obtained in the composite climate of Delhi (28.65°N, 77.25°E) can run the basic adsorption cooling cycle efficiently throughout the year. Whereas, the monsoon months of July and August in the warm and humid climate of Durgapur (23.48°N, 87.32°E) are unable to supply the required driving heat.

  9. Critical current enhancement driven by suppression of superconducting fluctuation in ion-gated ultrathin FeSe

    Science.gov (United States)

    Harada, T.; Shiogai, J.; Miyakawa, T.; Nojima, T.; Tsukazaki, A.

    2018-05-01

    The framework of phase transition, such as superconducting transition, occasionally depends on the dimensionality of materials. Superconductivity is often weakened in the experimental conditions of two-dimensional thin films due to the fragile superconducting state against defects and interfacial effects. In contrast to this general trend, superconductivity in the thin limit of FeSe exhibits an opposite trend, such as an increase in critical temperature (T c) and the superconducting gap exceeding the bulk values; however, the dominant mechanism is still under debate. Here, we measured thickness-dependent electrical transport properties of the ion-gated FeSe thin films to evaluate the superconducting critical current (I c) in the ultrathin FeSe. Upon systematically decreasing the FeSe thickness by the electrochemical etching technique in the Hall bar-shaped electric double-layer transistors, we observed a dramatic enhancement of I c reaching about 10 mA and corresponding to about 107 A cm‑2 in the thinnest condition. By analyzing the transition behavior, we clarify that the suppressed superconducting fluctuation is one of the origins of the large I c in the ion-gated ultrathin FeSe films. These results indicate the existence of a robust superconducting state possibly with dense Cooper pairs at the thin limit of FeSe.

  10. Real-time observation of fluctuations in a driven-dissipative quantum many-body system undergoing a phase transition

    Science.gov (United States)

    Donner, Tobias

    2015-03-01

    A Bose-Einstein condensate whose motional degrees of freedom are coupled to a high-finesse optical cavity via a transverse pump beam constitutes a dissipative quantum many-body system with long range interactions. These interactions can induce a structural phase transition from a flat to a density-modulated state. The transverse pump field simultaneously represents a probe of the atomic density via cavity- enhanced Bragg scattering. By spectrally analyzing the light field leaking out of the cavity, we measure non-destructively the dynamic structure factor of the fluctuating atomic density while the system undergoes the phase transition. An observed asymmetry in the dynamic structure factor is attributed to the coupling to dissipative baths. Critical exponents for both sides of the phase transition can be extracted from the data. We further discuss our progress in adding strong short-range interactions to this system, in order to explore Bose-Hubbard physics with cavity-mediated long-range interactions and self-organization in lower dimensions.

  11. Fluctuation-driven directional flow of energy in biochemical cycle: Electric activation of Na,K ATPase

    Science.gov (United States)

    Yow Tsong, Tian

    1998-03-01

    Na,K ATPase is an ion pump which uses chemical bond energy of ATP to pump Na ion out of, and K ion into living cell thus maintaining ionic and osmotic balances of the cell. Both are uphill transport reactions. Surprisingly we have found that electric energy can also substitute chemical energy to fuel the pump activity. However, in this case only electric fields of certain waveforms, amplitudes, and frequencies are effective. Waveform, amplitude and frequency are three elements of signal. In other words, Na,K ATPase can recognize, process, and harvest energy from an oscillating or a fluctuating electric field to drive an endergonic reaction. The enzyme is a molecular transducer of electric signal. This report will describe electric activation experiment to define electric signal. Electric signal will then mixed with electric noise of broad power spectrum for experiment. Effect of white noise (WN) on the efficiency of Na,K ATPase will be investigated. It will be shown that WN of appropriate power level can improve the pump efficiency when a sub-optimal electric field is used. WN can also carry a sub-threshold signal to cross over the threshold. Stochastic resonance will be discussed in reference to these observations.

  12. Astronomical constraints on the duration of the Early Jurassic Pliensbachian Stage and global climatic fluctuations

    Science.gov (United States)

    Ruhl, Micha; Hesselbo, Stephen P.; Hinnov, Linda; Jenkyns, Hugh C.; Xu, Weimu; Riding, James B.; Storm, Marisa; Minisini, Daniel; Ullmann, Clemens V.; Leng, Melanie J.

    2016-12-01

    The Early Jurassic was marked by multiple periods of major global climatic and palaeoceanographic change, biotic turnover and perturbed global geochemical cycles, commonly linked to large igneous province volcanism. This epoch was also characterised by the initial break-up of the super-continent Pangaea and the opening and formation of shallow-marine basins and ocean gateways, the timing of which are poorly constrained. Here, we show that the Pliensbachian Stage and the Sinemurian-Pliensbachian global carbon-cycle perturbation (marked by a negative shift in δ13 C of 2- 4 ‰), have respective durations of ∼8.7 and ∼2 Myr. We astronomically tune the floating Pliensbachian time scale to the 405 Kyr eccentricity solution (La2010d), and propose a revised Early Jurassic time scale with a significantly shortened Sinemurian Stage duration of 6.9 ± 0.4 Myr. When calibrated against the new time scale, the existing Pliensbachian seawater 87Sr/86Sr record shows relatively stable values during the first ∼2 Myr of the Pliensbachian, superimposed on the long-term Early Jurassic decline in 87Sr/86Sr. This plateau in 87Sr/86Sr values coincides with the Sinemurian-Pliensbachian boundary carbon-cycle perturbation. It is possibly linked to a late phase of Central Atlantic Magmatic Province (CAMP) volcanism that induced enhanced global weathering of continental crustal materials, leading to an elevated radiogenic strontium flux to the global ocean.

  13. Ecological opportunities, habitat, and past climatic fluctuations influenced the diversification of modern turtles.

    Science.gov (United States)

    Rodrigues, João Fabrício Mota; Diniz-Filho, José Alexandre Felizola

    2016-08-01

    Habitat may be viewed as an important life history component potentially related to diversification patterns. However, differences in diversification rates between aquatic and terrestrial realms are still poorly explored. Testudines is a group distributed worldwide that lives in aquatic and terrestrial environments, but until now no-one has evaluated the diversification history of the group as a whole. We aim here to investigate the diversification history of turtles and to test if habitat influenced speciation rate in these animals. We reconstructed the phylogeny of the modern species of chelonians and estimated node divergence dates using molecular markers and a Bayesian approach. Then, we used Bayesian Analyses of Macroevolutionary Mixtures to evaluate the diversification history of turtles and evaluate the effect of habitat on this pattern. Our reconstructed phylogeny covered 300 species (87% of the total diversity of the group). We found that the emydid subfamily Deirochelyinae, which forms the turtle hotspot in south-eastern United States, had an increase in its speciation rate, and that Galapagos tortoises had similar increases. Current speciation rates are lower in terrestrial turtles, contradicting studies supporting the idea terrestrial animals diversify more than aquatic species. Our results suggest that habitat, ecological opportunities, island invasions, and climatic factors are important drivers of diversification in modern turtles and reinforce the importance of habitat as a diversification driver. Copyright © 2016 Elsevier Inc. All rights reserved.

  14. Daily cytokine fluctuations, driven by leptin, are associated with fatigue severity in chronic fatigue syndrome: evidence of inflammatory pathology.

    Science.gov (United States)

    Stringer, Elizabeth Ann; Baker, Katharine Susanne; Carroll, Ian R; Montoya, Jose G; Chu, Lily; Maecker, Holden T; Younger, Jarred W

    2013-04-09

    Chronic fatigue syndrome (CFS) is a debilitating disorder characterized by persistent fatigue that is not alleviated by rest. The lack of a clearly identified underlying mechanism has hindered the development of effective treatments. Studies have demonstrated elevated levels of inflammatory factors in patients with CFS, but findings are contradictory across studies and no biomarkers have been consistently supported. Single time-point approaches potentially overlook important features of CFS, such as fluctuations in fatigue severity. We have observed that individuals with CFS demonstrate significant day-to-day variability in their fatigue severity. Therefore, to complement previous studies, we implemented a novel longitudinal study design to investigate the role of cytokines in CFS pathophysiology. Ten women meeting the Fukuda diagnostic criteria for CFS and ten healthy age- and body mass index (BMI)-matched women underwent 25 consecutive days of blood draws and self-reporting of symptom severity. A 51-plex cytokine panel via Luminex was performed for each of the 500 serum samples collected. Our primary hypothesis was that daily fatigue severity would be significantly correlated with the inflammatory adipokine leptin, in the women with CFS and not in the healthy control women. As a post-hoc analysis, a machine learning algorithm using all 51 cytokines was implemented to determine whether immune factors could distinguish high from low fatigue days. Self-reported fatigue severity was significantly correlated with leptin levels in six of the participants with CFS and one healthy control, supporting our primary hypothesis. The machine learning algorithm distinguished high from low fatigue days in the CFS group with 78.3% accuracy. Our results support the role of cytokines in the pathophysiology of CFS.

  15. Downscaling of South America present climate driven by 4-member HadCM3 runs

    Energy Technology Data Exchange (ETDEWEB)

    Chou, Sin Chan; Marengo, Jose A.; Lyra, Andre A.; Sueiro, Gustavo; Pesquero, Jose F.; Alves, Lincoln M.; Chagas, Diego J.; Gomes, Jorge L.; Bustamante, Josiane F.; Tavares, Priscila [National Institute for Space Research (INPE), Sao Paulo (Brazil); Kay, Gillian; Betts, Richard [UK Met Office Hadley Centre, Devon (United Kingdom)

    2012-02-15

    The objective of this work is to evaluate climate simulations over South America using the regional Eta Model driven by four members of an ensemble of the UK Met Office Hadley Centre HadCM3 global model. The Eta Model has been modified with the purpose of performing long-term decadal integrations and has shown to reproduce ''present climate'' - the period 1961-1990 - reasonably well when forced by HadCM3. The global model lateral conditions with a resolution of 2.5 latitude x 3.75 longitude were provided at a frequency of 6 h. Each member of the global model ensemble has a different climate sensitivity, and the four members were selected to span the range of uncertainty encompassed by the ensemble. The Eta Model nested in the HadCM3 global model was configured with 40-km horizontal resolution and 38 layers in the vertical. No large-scale internal nudging was applied. Results are shown for austral summer and winter at present climate defined as 1961-90. The upper and low-level circulation patterns produced by the Eta-CPTEC/HadCM3 experiment set-up show good agreement with reanalysis data and the mean precipitation and temperature with CRU observation data. The spread in the downscaled mean precipitation and temperature is small when compared against model errors. On the other hand, the benefits in using an ensemble is clear in the improved representation of the seasonal cycle by the ensemble mean over any one realization. El Nino and La Nina years were identified in the HadCM3 member runs based on the NOAA Climate Prediction Center criterion of sea surface temperature anomalies in the Nino 3.4 area. The frequency of the El Nino and La Nina events in the studied period is underestimated by HadCM3. The precipitation and temperature anomalies typical of these events are reproduced by most of the Eta-CPTEC/HadCM3 ensemble, although small displacements of the positions of the anomalies occur. This experiment configuration is the first step on the

  16. Streamflow in the upper Mississippi river basin as simulated by SWAT driven by 20{sup th} century contemporary results of global climate models and NARCCAP regional climate models

    Energy Technology Data Exchange (ETDEWEB)

    Takle, Eugene S.; Jha, Manoj; Lu, Er; Arritt, Raymond W.; Gutowski, William J. [Iowa State Univ. Ames, IA (United States)

    2010-06-15

    We use Soil and Water Assessment Tool (SWAT) when driven by observations and results of climate models to evaluate hydrological quantities, including streamflow, in the Upper Mississippi River Basin (UMRB) for 1981-2003 in comparison to observed streamflow. Daily meteorological conditions used as input to SWAT are taken from (1) observations at weather stations in the basin, (2) daily meteorological conditions simulated by a collection of regional climate models (RCMs) driven by reanalysis boundary conditions, and (3) daily meteorological conditions simulated by a collection of global climate models (GCMs). Regional models used are those whose data are archived by the North American Regional Climate Change Assessment Program (NARCCAP). Results show that regional models correctly simulate the seasonal cycle of precipitation, temperature, and streamflow within the basin. Regional models also capture interannual extremes represented by the flood of 1993 and the dry conditions of 2000. The ensemble means of both the GCM-driven and RCM-driven simulations by SWAT capture both the timing and amplitude of the seasonal cycle of streamflow with neither demonstrating significant superiority at the basin level. (orig.)

  17. Field Performance of Inverter-Driven Heat Pumps in Cold Climates

    Energy Technology Data Exchange (ETDEWEB)

    Williamson, James [Consortium of Advanced Residential Buildings, Norwalk, CT (United States); Aldrich, Robb [Consortium of Advanced Residential Buildings, Norwalk, CT (United States)

    2015-08-19

    Traditionally, air-source heat pumps (ASHPs) have been used more often in warmer climates; however, some new ASHPs are gaining ground in colder areas. These systems operate at subzero (Fahrenheit) temperatures and many do not include backup electric resistance elements. There are still uncertainties, however, about capacity and efficiency in cold weather. Also, questions such as “how cold is too cold?” do not have clear answers. These uncertainties could lead to skepticism among homeowners; poor energy savings estimates; suboptimal system selection by heating, ventilating, and air-conditioning contractors; and inconsistent energy modeling. In an effort to better understand and characterize the heating performance of these units in cold climates, the U.S. Department of Energy Building America team, Consortium for Advanced Residential Buildings (CARB), monitored seven inverter-driven, ductless ASHPs across the Northeast. Operating data were collected for three Mitsubishi FE18 units, three Mitsubishi FE12 units, and one Fujitsu 15RLS2 unit. The intent of this research was to assess heat output, electricity consumption, and coefficients of performance (COPs) at various temperatures and load conditions. This assessment was accomplished with long- and short-term tests that measured power consumption; supply, return, and outdoor air temperatures; and airflow through the indoor fan coil.

  18. Climate-change-driven deterioration of water quality in a mineralized watershed.

    Science.gov (United States)

    Todd, Andrew S; Manning, Andrew H; Verplanck, Philip L; Crouch, Caitlin; McKnight, Diane M; Dunham, Ryan

    2012-09-04

    A unique 30-year streamwater chemistry data set from a mineralized alpine watershed with naturally acidic, metal-rich water displays dissolved concentrations of Zn and other metals of ecological concern increasing by 100-400% (400-2000 μg/L) during low-flow months, when metal concentrations are highest. SO(4) and other major ions show similar increases. A lack of natural or anthropogenic land disturbances in the watershed during the study period suggests that climate change is the underlying cause. Local mean annual and mean summer air temperatures have increased at a rate of 0.2-1.2 °C/decade since the 1980s. Other climatic and hydrologic indices, including stream discharge during low-flow months, do not display statistically significant trends. Consideration of potential specific causal mechanisms driven by rising temperatures suggests that melting of permafrost and falling water tables (from decreased recharge) are probable explanations for the increasing concentrations. The prospect of future widespread increases in dissolved solutes from mineralized watersheds is concerning given likely negative impacts on downstream ecosystems and water resources, and complications created for the establishment of attainable remediation objectives at mine sites.

  19. Climate-driven disparities among ecological interactions threaten kelp forest persistence.

    Science.gov (United States)

    Provost, Euan J; Kelaher, Brendan P; Dworjanyn, Symon A; Russell, Bayden D; Connell, Sean D; Ghedini, Giulia; Gillanders, Bronwyn M; Figueira, WillIAM; Coleman, Melinda A

    2017-01-01

    The combination of ocean warming and acidification brings an uncertain future to kelp forests that occupy the warmest parts of their range. These forests are not only subject to the direct negative effects of ocean climate change, but also to a combination of unknown indirect effects associated with changing ecological landscapes. Here, we used mesocosm experiments to test the direct effects of ocean warming and acidification on kelp biomass and photosynthetic health, as well as climate-driven disparities in indirect effects involving key consumers (urchins and rock lobsters) and competitors (algal turf). Elevated water temperature directly reduced kelp biomass, while their turf-forming competitors expanded in response to ocean acidification and declining kelp canopy. Elevated temperatures also increased growth of urchins and, concurrently, the rate at which they thinned kelp canopy. Rock lobsters, which are renowned for keeping urchin populations in check, indirectly intensified negative pressures on kelp by reducing their consumption of urchins in response to elevated temperature. Overall, these results suggest that kelp forests situated towards the low-latitude margins of their distribution will need to adapt to ocean warming in order to persist in the future. What is less certain is how such adaptation in kelps can occur in the face of intensifying consumptive (via ocean warming) and competitive (via ocean acidification) pressures that affect key ecological interactions associated with their persistence. If such indirect effects counter adaptation to changing climate, they may erode the stability of kelp forests and increase the probability of regime shifts from complex habitat-forming species to more simple habitats dominated by algal turfs. © 2016 John Wiley & Sons Ltd.

  20. Climate-driven trends in the occurrence of major floods across North America and Europe

    Science.gov (United States)

    Hodgkins, Glenn A.; Whitfield, Paul H.; Burn, Donald H.; Hannaford, Jamie; Renard, Benjamin; Stahl, Kerstin; Fleig, Anne K.; Madsen, Henrik; Mediero, Luis; Korhonen, Johanna; Murphy, Conor; Crochet, Philippe; Wilson, Donna

    2016-04-01

    Every year river floods cause enormous damage around the world. Recent major floods in North America and Europe, for example, have received much press, with some concluding that these floods are more frequent in recent years as a result of anthropogenic warming. There has been considerable scientific effort invested in establishing whether observed flood records show evidence of trends or variability in flood frequency, and to determine whether these patterns can be linked to climatic changes. However, the river catchments used in many published studies are influenced by direct human alteration such as reservoir regulation and urbanisation, which can confound the interpretation of climate-driven variability. Furthermore, a majority of previous studies have analysed changes in low magnitude floods, such as the annual peak flow, at a national scale. Few studies are known that have analysed changes in large floods (greater than 25-year floods) on a continental scale. To fill this research gap, we present a study analysing flood flows from reference hydrologic networks (RHNs) or RHN-like gauges across a large study domain embracing North America and much of Europe. RHNs comprise gauging stations with minimally disturbed catchment conditions, which have a near-natural flow regime and provide good quality data; RHN analyses thus allow hydro-climatic variability to be distinguished from direct artificial disturbances or data inhomogeneities. One of the key innovations in this study is the definition of an RHN-like network consisting of 1204 catchments on a continental scale. The network incorporates existing, well-established RHNs in Canada, the US, the UK, Ireland and Norway, alongside RHN-like catchments from Europe (France, Switzerland, Iceland, Denmark, Sweden, Finland, Spain), which have been incorporated in the network following a major effort to ensure RHN-like status of candidate gauges through consultation with local experts. As the aim of the study is to examine

  1. Modelling marine community responses to climate-driven species redistribution to guide monitoring and adaptive ecosystem-based management

    NARCIS (Netherlands)

    Marzloff, Martin Pierre; Melbourne-Thomas, Jessica; Hamon, Katell G.; Hoshino, Eriko; Jennings, Sarah; Putten, Van Ingrid E.; Pecl, Gretta T.

    2016-01-01

    As a consequence of global climate-driven changes, marine ecosystems are experiencing polewards redistributions of species – or range shifts – across taxa and throughout latitudes worldwide. Research on these range shifts largely focuses on understanding and predicting changes in the distribution of

  2. Climatically related millennial-scale fluctuations in strength of California margin oxygen-minimum zone during the past 60 k.y.

    Energy Technology Data Exchange (ETDEWEB)

    Cannariato, K.G.; Kennett, J.P.

    1999-11-01

    A strong oxygen-minimum zone (OMZ) currently exists along the California margin because of a combination of high surface-water productivity and poor intermediate-water ventilation. However, the strength of this OMZ may have been sensitive to late Quaternary ocean-circulation and productivity changes along the margin. Although sediment-lamination strength has been used to trace ocean-oxygenation changes in the past, oxygen levels on the open margin are not sufficiently low for laminations to form. In these regions, benthic foraminifera are highly sensitive monitors of OMZ strength, and their fossil assemblages can be used to reconstruct past fluctuations. Benthic foraminiferal assemblages from Ocean Drilling Program Site 1017, off Point Conception, exhibit major and rapid faunal oscillations in response to late Quaternary millennial-scale climate change (Dansgaard-Oeschger cycles) on the open central California margin. These faunal oscillations can be correlated to and are apparently synchronous with those reported from Santa Barbara Basin. Together they represent major fluctuations in the strength of the OMZ which were intimately associated with global climate change--weakening, perhaps disappearing, during cool periods and strengthening during warm periods. These rapid, major OMZ strength fluctuations were apparently widespread on the Northeast Pacific margin and must have influenced the evolution of margin biota and altered biogeochemical cycles with potential feedbacks to global climate change.

  3. On the data-driven inference of modulatory networks in climate science: an application to West African rainfall

    Science.gov (United States)

    González, D. L., II; Angus, M. P.; Tetteh, I. K.; Bello, G. A.; Padmanabhan, K.; Pendse, S. V.; Srinivas, S.; Yu, J.; Semazzi, F.; Kumar, V.; Samatova, N. F.

    2015-01-01

    Decades of hypothesis-driven and/or first-principles research have been applied towards the discovery and explanation of the mechanisms that drive climate phenomena, such as western African Sahel summer rainfall~variability. Although connections between various climate factors have been theorized, not all of the key relationships are fully understood. We propose a data-driven approach to identify candidate players in this climate system, which can help explain underlying mechanisms and/or even suggest new relationships, to facilitate building a more comprehensive and predictive model of the modulatory relationships influencing a climate phenomenon of interest. We applied coupled heterogeneous association rule mining (CHARM), Lasso multivariate regression, and dynamic Bayesian networks to find relationships within a complex system, and explored means with which to obtain a consensus result from the application of such varied methodologies. Using this fusion of approaches, we identified relationships among climate factors that modulate Sahel rainfall. These relationships fall into two categories: well-known associations from prior climate knowledge, such as the relationship with the El Niño-Southern Oscillation (ENSO) and putative links, such as North Atlantic Oscillation, that invite further research.

  4. Functional Resilience against Climate-Driven Extinctions - Comparing the Functional Diversity of European and North American Tree Floras.

    Directory of Open Access Journals (Sweden)

    Mario Liebergesell

    Full Text Available Future global change scenarios predict a dramatic loss of biodiversity for many regions in the world, potentially reducing the resistance and resilience of ecosystem functions. Once before, during Plio-Pleistocene glaciations, harsher climatic conditions in Europe as compared to North America led to a more depauperate tree flora. Here we hypothesize that this climate driven species loss has also reduced functional diversity in Europe as compared to North America. We used variation in 26 traits for 154 North American and 66 European tree species and grid-based co-occurrences derived from distribution maps to compare functional diversity patterns of the two continents. First, we identified similar regions with respect to contemporary climate in the temperate zone of North America and Europe. Second, we compared the functional diversity of both continents and for the climatically similar sub-regions using the functional dispersion-index (FDis and the functional richness index (FRic. Third, we accounted in these comparisons for grid-scale differences in species richness, and, fourth, investigated the associated trait spaces using dimensionality reduction. For gymnosperms we find similar functional diversity on both continents, whereas for angiosperms functional diversity is significantly greater in Europe than in North America. These results are consistent across different scales, for climatically similar regions and considering species richness patterns. We decomposed these differences in trait space occupation into differences in functional diversity vs. differences in functional identity. We show that climate-driven species loss on a continental scale might be decoupled from or at least not linearly related to changes in functional diversity. This might be important when analyzing the effects of climate-driven biodiversity change on ecosystem functioning.

  5. Increased Wildfire Risk Driven by Climate and Development Interactions in the Bolivian Chiquitania, Southern Amazonia.

    Science.gov (United States)

    Devisscher, Tahia; Anderson, Liana O; Aragão, Luiz E O C; Galván, Luis; Malhi, Yadvinder

    2016-01-01

    Wildfires are becoming increasingly dominant in tropical landscapes due to reinforcing feedbacks between land cover change and more severe dry conditions. This study focused on the Bolivian Chiquitania, a region located at the southern edge of Amazonia. The extensive, unique and well-conserved tropical dry forest in this region is susceptible to wildfires due to a marked seasonality. We used a novel approach to assess fire risk at the regional level driven by different development trajectories interacting with changing climatic conditions. Possible future risk scenarios were simulated using maximum entropy modelling with presence-only data, combining land cover, anthropogenic and climatic variables. We found that important determinants of fire risk in the region are distance to roads, recent deforestation and density of human settlements. Severely dry conditions alone increased the area of high fire risk by 69%, affecting all categories of land use and land cover. Interactions between extreme dry conditions and rapid frontier expansion further increased fire risk, resulting in potential biomass loss of 2.44±0.8 Tg in high risk area, about 1.8 times higher than the estimates for the 2010 drought. These interactions showed particularly high fire risk in land used for 'extensive cattle ranching', 'agro-silvopastoral use' and 'intensive cattle ranching and agriculture'. These findings have serious implications for subsistence activities and the economy in the Chiquitania, which greatly depend on the forestry, agriculture and livestock sectors. Results are particularly concerning if considering the current development policies promoting frontier expansion. Departmental protected areas inhibited wildfires when strategically established in areas of high risk, even under drought conditions. However, further research is needed to assess their effectiveness accounting for more specific contextual factors. This novel and simple modelling approach can inform fire and land

  6. Increased Wildfire Risk Driven by Climate and Development Interactions in the Bolivian Chiquitania, Southern Amazonia.

    Directory of Open Access Journals (Sweden)

    Tahia Devisscher

    Full Text Available Wildfires are becoming increasingly dominant in tropical landscapes due to reinforcing feedbacks between land cover change and more severe dry conditions. This study focused on the Bolivian Chiquitania, a region located at the southern edge of Amazonia. The extensive, unique and well-conserved tropical dry forest in this region is susceptible to wildfires due to a marked seasonality. We used a novel approach to assess fire risk at the regional level driven by different development trajectories interacting with changing climatic conditions. Possible future risk scenarios were simulated using maximum entropy modelling with presence-only data, combining land cover, anthropogenic and climatic variables. We found that important determinants of fire risk in the region are distance to roads, recent deforestation and density of human settlements. Severely dry conditions alone increased the area of high fire risk by 69%, affecting all categories of land use and land cover. Interactions between extreme dry conditions and rapid frontier expansion further increased fire risk, resulting in potential biomass loss of 2.44±0.8 Tg in high risk area, about 1.8 times higher than the estimates for the 2010 drought. These interactions showed particularly high fire risk in land used for 'extensive cattle ranching', 'agro-silvopastoral use' and 'intensive cattle ranching and agriculture'. These findings have serious implications for subsistence activities and the economy in the Chiquitania, which greatly depend on the forestry, agriculture and livestock sectors. Results are particularly concerning if considering the current development policies promoting frontier expansion. Departmental protected areas inhibited wildfires when strategically established in areas of high risk, even under drought conditions. However, further research is needed to assess their effectiveness accounting for more specific contextual factors. This novel and simple modelling approach can

  7. The climate warming effect of a fen peat meadow with fluctuating water table is reduced by young alder trees

    Directory of Open Access Journals (Sweden)

    V. Huth

    2018-03-01

    Full Text Available Black alder (Alnus glutinosa (L. Gaertn. occurs naturally in temperate marshes and in minerotrophic peatlands and is also suitable for paludiculture - the cultivation of biomass on wet or rewetted peatland. We investigated the effect of a newly established black alder plantation on the greenhouse gas (GHG balance of a degraded fen in north-eastern Germany over a two-year period (August 2010–August 2012. We compared the alder plantation (Awet with an extensively used meadow (Mwet and a drier reference meadow (Mmoist. GHG fluxes were measured monthly to bi-monthly using the closed chamber method. Our results show that Awet was a slight net GHG (in CO2-eq sink of 3.4 ± 1.7 t ha-1 yr-1, Mwet was a moderate net GHG source of 9.6 ± 1.2 t ha 1 yr-1, and Mmoist was a strong net GHG source of 24.5 ± 1.6 t ha-1 yr-1. This was mainly driven by CO2 uptake at the two very moist (wet sites and by high CO2 release at the drier reference site. Awet was a larger CO2 sink than Mwet, probably due to additional CO2 uptake by the alder stand at Awet and carbon export in plant material harvested from Mwet. All sites were significant CH4 sources. Substantial CH4 emission peaks were observed at all sites following extraordinarily heavy precipitation during the summer of 2011, which accounted for up to 70 % of the accumulated two-year CH4 emissions. However, the Awet site generally emitted less CH4, possibly due to the effective oxygen transport mechanism in black alders. N2O emissions were negligible at all three sites. Our results indicate that the GHG balances of formerly drained fens benefit in the short term from planting of black alders, mostly due to reduced CH4 emissions. This study highlights the importance of acknowledging extreme precipitation events and groundwater fluctuations for the derivation of reliable GHG emission factors.

  8. Climate change-driven cliff and beach evolution at decadal to centennial time scales

    Science.gov (United States)

    Erikson, Li; O'Neill, Andrea; Barnard, Patrick; Vitousek, Sean; Limber, Patrick

    2017-01-01

    Here we develop a computationally efficient method that evolves cross-shore profiles of sand beaches with or without cliffs along natural and urban coastal environments and across expansive geographic areas at decadal to centennial time-scales driven by 21st century climate change projections. The model requires projected sea level rise rates, extrema of nearshore wave conditions, bluff recession and shoreline change rates, and cross-shore profiles representing present-day conditions. The model is applied to the ~470-km long coast of the Southern California Bight, USA, using recently available projected nearshore waves and bluff recession and shoreline change rates. The results indicate that eroded cliff material, from unarmored cliffs, contribute 11% to 26% to the total sediment budget. Historical beach nourishment rates will need to increase by more than 30% for a 0.25 m sea level rise (~2044) and by at least 75% by the year 2100 for a 1 m sea level rise, if evolution of the shoreline is to keep pace with rising sea levels.

  9. Scenario and modelling uncertainty in global mean temperature change derived from emission-driven global climate models

    Directory of Open Access Journals (Sweden)

    B. B. B. Booth

    2013-04-01

    Full Text Available We compare future changes in global mean temperature in response to different future scenarios which, for the first time, arise from emission-driven rather than concentration-driven perturbed parameter ensemble of a global climate model (GCM. These new GCM simulations sample uncertainties in atmospheric feedbacks, land carbon cycle, ocean physics and aerosol sulphur cycle processes. We find broader ranges of projected temperature responses arising when considering emission rather than concentration-driven simulations (with 10–90th percentile ranges of 1.7 K for the aggressive mitigation scenario, up to 3.9 K for the high-end, business as usual scenario. A small minority of simulations resulting from combinations of strong atmospheric feedbacks and carbon cycle responses show temperature increases in excess of 9 K (RCP8.5 and even under aggressive mitigation (RCP2.6 temperatures in excess of 4 K. While the simulations point to much larger temperature ranges for emission-driven experiments, they do not change existing expectations (based on previous concentration-driven experiments on the timescales over which different sources of uncertainty are important. The new simulations sample a range of future atmospheric concentrations for each emission scenario. Both in the case of SRES A1B and the Representative Concentration Pathways (RCPs, the concentration scenarios used to drive GCM ensembles, lies towards the lower end of our simulated distribution. This design decision (a legacy of previous assessments is likely to lead concentration-driven experiments to under-sample strong feedback responses in future projections. Our ensemble of emission-driven simulations span the global temperature response of the CMIP5 emission-driven simulations, except at the low end. Combinations of low climate sensitivity and low carbon cycle feedbacks lead to a number of CMIP5 responses to lie below our ensemble range. The ensemble simulates a number of high

  10. Scenario and modelling uncertainty in global mean temperature change derived from emission-driven global climate models

    Science.gov (United States)

    Booth, B. B. B.; Bernie, D.; McNeall, D.; Hawkins, E.; Caesar, J.; Boulton, C.; Friedlingstein, P.; Sexton, D. M. H.

    2013-04-01

    We compare future changes in global mean temperature in response to different future scenarios which, for the first time, arise from emission-driven rather than concentration-driven perturbed parameter ensemble of a global climate model (GCM). These new GCM simulations sample uncertainties in atmospheric feedbacks, land carbon cycle, ocean physics and aerosol sulphur cycle processes. We find broader ranges of projected temperature responses arising when considering emission rather than concentration-driven simulations (with 10-90th percentile ranges of 1.7 K for the aggressive mitigation scenario, up to 3.9 K for the high-end, business as usual scenario). A small minority of simulations resulting from combinations of strong atmospheric feedbacks and carbon cycle responses show temperature increases in excess of 9 K (RCP8.5) and even under aggressive mitigation (RCP2.6) temperatures in excess of 4 K. While the simulations point to much larger temperature ranges for emission-driven experiments, they do not change existing expectations (based on previous concentration-driven experiments) on the timescales over which different sources of uncertainty are important. The new simulations sample a range of future atmospheric concentrations for each emission scenario. Both in the case of SRES A1B and the Representative Concentration Pathways (RCPs), the concentration scenarios used to drive GCM ensembles, lies towards the lower end of our simulated distribution. This design decision (a legacy of previous assessments) is likely to lead concentration-driven experiments to under-sample strong feedback responses in future projections. Our ensemble of emission-driven simulations span the global temperature response of the CMIP5 emission-driven simulations, except at the low end. Combinations of low climate sensitivity and low carbon cycle feedbacks lead to a number of CMIP5 responses to lie below our ensemble range. The ensemble simulates a number of high-end responses which lie

  11. Lake Sediment Records as an Indicator of Holocene Fluctuations of Quelccaya Ice Cap, Peru and Regional Climate

    Science.gov (United States)

    Stroup, J. S.; Kelly, M. A.; Lowell, T. V.; Beal, S. A.; Smith, C. A.; Baranes, H. E.

    2012-12-01

    The past fluctuations of Quelccaya Ice Cap, (QIC; 13°S, 70°W, 5200 m asl) located in the southeastern Peruvian Andes, provide a record of tropical climate since the last glacial-interglacial transition. A detailed surficial geomorphic record of past glacial extents developed over the last several decades (e.g. Mercer and Palacios 1977; Buffen et al. 2009; Kelly et al. 2012 accepted) demonstrates that QIC is a dynamic glacial system. These records show that the ice cap was larger than present and retreating by ~11,500 yr BP, and smaller than present between ~7,000 and ~4,600 yr BP. The most recent advance occurred during the late Holocene (Little Ice Age;LIA), dated with 10Be surface exposure ages (510±90 yrs (n = 8)) (Stroup et al. in prep.). This overrode earlier deposits obscuring a complete Holocene record; we aim to address the gaps in glacial chronology using the sedimentary record archived in lakes. We retrieved two sets cores (8 and 5 m-long) from Laguna Challpacocha (13.91°S, 70.86°W, 5040 m asl), a lake that currently receives meltwater from QIC. Four radiocarbon ages from the cores suggest a continuous record dating to at least ~10,500 cal. yr BP. Variations in magnetic susceptibility, percent organic and inorganic carbon, bulk density, grayscale and X-ray fluorescence chemistry indicate changes in the amount of clastic sediment deposition. We interpret clastic sediments to have been deposited from ice cap meltwater, thus indicating more extensive ice. Clastic sediments compose the top of the core from 4 to 30 cm depth, below there is a sharp transition to organic sediments radiocarbon dated to (500±30 and 550±20 cal. yr BP). The radiocarbon ages are similar to the 10Be dated (LIA) glacial position. At least three other clastic units exist in the core; dating to ~2600-4300, ~4800-7300 and older then ~10,500 cal. yr BP based on a linear age model with four radiocarbon dates. We obtained two, ~4 m long, cores from Laguna Yanacocha (13.95°S,70.87

  12. Response to Comment on "Sensitivity of seafloor bathymetry to climate-driven fluctuations in mid-ocean ridge magma supply".

    Science.gov (United States)

    Olive, J-A; Behn, M D; Ito, G; Buck, W R; Escartín, J; Howell, S

    2016-07-15

    Tolstoy reports the existence of a characteristic 100 thousand year (ky) period in the bathymetry of fast-spreading seafloor but does not argue that sea level change is a first-order control on seafloor morphology worldwide. Upon evaluating the overlap between tectonic and Milankovitch periodicities across spreading rates, we reemphasize that fast-spreading ridges are the best potential recorders of a sea level signature in seafloor bathymetry. Copyright © 2016, American Association for the Advancement of Science.

  13. Comment on "Sensitivity of seafloor bathymetry to climate-driven fluctuations in mid-ocean ridge magma supply".

    Science.gov (United States)

    Tolstoy, Maya

    2016-07-15

    Olive et al (Reports, 16 October 2015, p. 310) and Goff (Technical Comment, 4 September 2015, p. 1065) raise important concerns with respect to recent findings of Milankovitch cycles in seafloor bathymetry. However, their results inherently support that the Southern East Pacific Rise is the optimum place to look for such signals and, in fact, models match those observations quite closely. Copyright © 2016, American Association for the Advancement of Science.

  14. Climate-sensitive feedbacks between hillslope processes and fluvial erosion in sediment-driven incision models

    Science.gov (United States)

    Skov, Daniel S.; Egholm, David L.

    2016-04-01

    Surface erosion and sediment production seem to have accelerated globally as climate cooled in the Late Cenozoic, [Molnar, P. 2004, Herman et al 2013]. Glaciers emerged in many high mountain ranges during the Quaternary, and glaciation therefore represents a likely explanation for faster erosion in such places. Still, observations and measurements point to increases in erosion rates also in landscapes where erosion is driven mainly by fluvial processes [Lease and Ehlers (2013), Reusser (2004)]. Flume experiments and fieldwork have shown that rates of incision are to a large degree controlled by the sediment load of streams [e.g. Sklar and Dietrich (2001), Beer and Turowski (2015)]. This realization led to the formulation of sediment-flux dependent incision models [Sklar and Dietrich (2004)]. The sediment-flux dependence links incision in the channels to hillslope processes that supply sediment to the channels. The rates of weathering and soil transport on the hillslopes are processes that are likely to respond to changing temperatures, e.g. because of vegetation changes or the occurrence of frost. In this study, we perform computational landscape evolution experiments, where the coupling between fluvial incision and hillslope processes is accounted for by coupling a sediment-flux-dependent model for fluvial incision to a climate-dependent model for weathering and hillslope sediment transport. The computational experiments first of all demonstrate a strong positive feedback between channel and hillslope processes. In general, faster weathering leads to higher rates of channel incision, which further increases the weathering rates, mainly because of hillslope steepening. Slower weathering leads to the opposite result. The experiments also demonstrate, however, that the feedbacks vary significantly between different parts of a drainage network. For example, increasing hillslope sediment production may accelerate incision in the upper parts of the catchment, while at

  15. Evaluating the performance of infectious disease forecasts: A comparison of climate-driven and seasonal dengue forecasts for Mexico

    OpenAIRE

    Johansson, Michael A.; Reich, Nicholas G.; Hota, Aditi; Brownstein, John S.; Santillana, Mauricio

    2016-01-01

    Dengue viruses, which infect millions of people per year worldwide, cause large epidemics that strain healthcare systems. Despite diverse efforts to develop forecasting tools including autoregressive time series, climate-driven statistical, and mechanistic biological models, little work has been done to understand the contribution of different components to improved prediction. We developed a framework to assess and compare dengue forecasts produced from different types of models and evaluate...

  16. Changes in climate, catchment vegetation and hydrogeology as the causes of dramatic lake-level fluctuations in the Kurtna Lake District, NE Estonia

    Directory of Open Access Journals (Sweden)

    Marko Vainu

    2014-02-01

    Full Text Available Numerous lakes in the world serve as sensitive indicators of climate change. Water levels for lakes Ahnejärv and Martiska, two vulnerable oligotrophic closed-basin lakes on sandy plains in northeastern Estonia, fell more than 3 m in 1946–1987 and rose up to 2 m by 2009. Earlier studies indicated that changes in rates of groundwater abstraction were primarily responsible for the changes, but scientifically sound explanations for water-level fluctuations were still lacking. Despite the inconsistent water-level dataset, we were able to assess the importance of changing climate, catchment vegetation and hydrogeology in water-level fluctuations in these lakes. Our results from water-balance simulations indicate that before the initiation of ground­water abstraction in 1972 a change in the vegetation composition on the catchments triggered the lake-level decrease. The water-level rise in 1990–2009 was caused, in addition to the reduction of groundwater abstraction rates, by increased precipitation and decreased evaporation. The results stress that climate, catchment vegetation and hydrogeology must all be considered while evaluating the causes of modern water-level changes in lakes.

  17. Separating the Effects of Tropical Atlantic and Pacific SST-driven Climate Variability on Amazon Carbon Exchange

    Science.gov (United States)

    Liptak, J.; Keppel-Aleks, G.

    2016-12-01

    Amazon forests store an estimated 25% percent of global terrestrial carbon per year1, 2, but the responses of Amazon carbon uptake to climate change is highly uncertain. One source of this uncertainty is tropical sea surface temperature variability driven by teleconnections. El Nino-Southern Oscillation (ENSO) is a key driver of year-to-year Amazon carbon exchange, with associated temperature and precipitation changes favoring net carbon storage in La Nina years, and net carbon release during El Nino years3. To determine how Amazon climate and terrestrial carbon fluxes react to ENSO alone and in concert with other SST-driven teleconnections such as the Atlantic Multidecadal Oscillation (AMO), we force the atmosphere (CAM5) and land (CLM4) components of the CESM(BGC) with prescribed monthly SSTs over the period 1950—2014 in a Historical control simulation. We then run an experiment (PAC) with time-varying SSTs applied only to the tropical equatorial Pacific Ocean, and repeating SST seasonal cycle climatologies elsewhere. Limiting SST variability to the equatorial Pacific indicates that other processes enhance ENSO-driven Amazon climate anomalies. Compared to the Historical control simulation, warming, drying and terrestrial carbon loss over the Amazon during El Nino periods are lower in the PAC simulation, especially prior to 1990 during the cool phase of the AMO. Cooling, moistening, and net carbon uptake during La Nina periods are also reduced in the PAC simulation, but differences are greater after 1990 during the warm phase of the AMO. By quantifying the relationships among climate drivers and carbon fluxes in the Historical and PAC simulations, we both assess the sensitivity of these relationships to the magnitude of ENSO forcing and quantify how other teleconnections affect ENSO-driven Amazon climate feedbacks. We expect that these results will help us improve hypotheses for how Atlantic and Pacific climate trends will affect future Amazon carbon carbon

  18. Geological events and Pliocene climate fluctuations explain the phylogeographical pattern of the cold water fish Rhynchocypris oxycephalus (Cypriniformes: Cyprinidae) in China.

    Science.gov (United States)

    Yu, Dan; Chen, Ming; Tang, Qiongying; Li, Xiaojuan; Liu, Huanzhang

    2014-10-25

    Rhynchocypris oxycephalus is a cold water fish with a wide geographic distribution including the relatively warm temperate regions of southern China. It also occurs in second- and third-step geomorphic areas in China. Previous studies have postulated that high-altitude populations of R. oxycephalus in southern China are Quaternary glacial relics. In this study, we used the mitochondrial gene Cytb and the nuclear gene RAG2 to investigate the species phylogeographical patterns and to test two biogeographic hypotheses: (1) that divergence between lineages supports the three-step model and (2) climatic fluctuations during the Quaternary resulted in the present distribution in southern China. Phylogenetic analysis detected three major matrilines (A, B, and C); with matrilines B and C being further subdivided into two submatrilines. Based on genetic distances and morphological differences, matriline A potentially represents a cryptic subspecies. The geographic division between matrilines B and C coincided with the division of the second and third geomorphic steps in China, suggesting a historical vicariance event. Pliocene climatic fluctuations might have facilitated the southwards dispersal of R. oxycephalus in matriline C, with the subsequent warming resulting in its split into submatrilines C1 and C2, leaving submatriline C2 as a relic in southern China. Our study demonstrates that geological events (three steps orogenesis) and climate fluctuations during the Pliocene were important factors in shaping phylogeographical patterns in R. oxycephalus. Notably, no genetic diversity was detected in several populations, all of which possessed unique genotypes. This indicates the uniqueness of local populations and calls for a special conservation plan for the whole species at the population level.

  19. Teaching and Practicing Climate Politics at College of the Atlantic: Student-inspired, Student-driven

    Directory of Open Access Journals (Sweden)

    Doreen Stabinsky

    2015-06-01

    Full Text Available College of the Atlantic students past and present play leadership roles in the international climate justice youth movement. Student interest in climate change politics at the global level, particularly within the United Nations Framework Convention on Climate Change, has inspired the development of a range of courses at COA in global environmental diplomacy. The courses provide a climate justice framework for understanding the geopolitics and political economy of the negotiations, serve to link students with key actors in the climate justice movement, and ultimately to contribute to their own development as climate justice leaders.

  20. Radiocarbon dating and Dendrochronology for Statigraphic Units near Tebano, Senio Northern Apennines - Time frame of Climatic Fluctuation at the onset of the Younger Dryas

    Science.gov (United States)

    Eggenschwiler, Loren; Hajdas, Irka; Cherubini, Paolo; Picotti, Vincenzo; Saurer, Matthias

    2017-04-01

    The presence of Pinus [sylvestris] provides an insight into dramatic events due to climatic changes. Several major and minor climatic fluctuations have had a strong impact on terrestrial and marine environments since the last glacial period to present day (Ravazzi et al. 2006). This study aims to describe the response of a fluvial environment through the use of dendrochronology and stratigraphy. Here, we intend to get a better understanding of how these climatic fluctuations affect the behavior of the Senio River (Lotter et al. 1992). In Tebano, Italy, several Pinus sylvestris subfossil trunks were discovered during excavation for an irrigation pool. Subfossil samples were collected to analyze the climate during the Younger Dryas (11,000 years BP) in detail. Charcoal samples from the Bubano clay quarry extend our research to further to 35,500 cal. years BP. The combination of dendrochronology along with stratigraphy allowed us to examine the climate at a detailed local and apply it to a broader spectrum. Tree-ring measurements and cross dating provided a better understanding and verification of extreme events that occurred during the lifespans of the trees. The use of stable isotopes indicates the extreme conditions that occurred. Radiocarbon dating validates the age of the samples and what geological period they come from. Along with stratigraphy, we were able to compile depth data to create a sediment curve. Using various methods throughout this study, we discovered the climatic situation of Pinus 11,000 years BP and are able to compare them with samples from today. These present day samples mark two of the southernmost extents of the Pinus population. We were then able to comprehend the magnitude of sediment supply and precipitation. Through this collection of methods and data, we are able to understand the influence of climate change in the past and the potential changes of the future. REFERENCES Lotter, A. F.; Eicher, U.; Siegenthaler, U.; Birks, H. J. B

  1. Evaluation of regional climate simulations over the Great Lakes region driven by three global data sets

    Science.gov (United States)

    Shiyuan Zhong; Xiuping Li; Xindi Bian; Warren E. Heilman; L. Ruby Leung; William I. Jr. Gustafson

    2012-01-01

    The performance of regional climate simulations is evaluated for the Great Lakes region. Three 10-year (1990-1999) current-climate simulations are performed using the MM5 regional climate model (RCM) with 36-km horizontal resolution. The simulations employed identical configuration and physical parameterizations, but different lateral boundary conditions and sea-...

  2. Long term fluctuations of groundwater mine pollution in a sulfide mining district with dry Mediterranean climate: Implications for water resources management and remediation.

    Science.gov (United States)

    Caraballo, Manuel A; Macías, Francisco; Nieto, José Miguel; Ayora, Carlos

    2016-01-01

    Water resources management and restoration strategies, and subsequently ecological and human life quality, are highly influenced by the presence of short and long term cycles affecting the intensity of a targeted pollution. On this respect, a typical acid mine drainage (AMD) groundwater from a sulfide mining district with dry Mediterranean climate (Iberian Pyrite Belt, SW Spain) was studied to unravel the effect of long term weather changes in water flow rate and metal pollutants concentration. Three well differentiated polluting stages were observed and the specific geochemical, mineralogical and hydrological processes involved (pyrite and enclosing rocks dissolution, evaporitic salts precipitation-redisolution and pluviometric long term fluctuations) were discussed. Evidencing the importance of including longer background monitoring stage in AMD management and restoration strategies, the present study strongly advise a minimum 5-years period of AMD continuous monitoring previous to the design of any AMD remediation system in regions with dry Mediterranean climate. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Climate-driven changes to the spatio-temporal distribution of the parasitic nematode, Haemonchus contortus, in sheep in Europe.

    Science.gov (United States)

    Rose, Hannah; Caminade, Cyril; Bolajoko, Muhammad Bashir; Phelan, Paul; van Dijk, Jan; Baylis, Matthew; Williams, Diana; Morgan, Eric R

    2016-03-01

    Recent climate change has resulted in changes to the phenology and distribution of invertebrates worldwide. Where invertebrates are associated with disease, climate variability and changes in climate may also affect the spatio-temporal dynamics of disease. Due to its significant impact on sheep production and welfare, the recent increase in diagnoses of ovine haemonchosis caused by the nematode Haemonchus contortus in some temperate regions is particularly concerning. This study is the first to evaluate the impact of climate change on H. contortus at a continental scale. A model of the basic reproductive quotient of macroparasites, Q0 , adapted to H. contortus and extended to incorporate environmental stochasticity and parasite behaviour, was used to simulate Pan-European spatio-temporal changes in H. contortus infection pressure under scenarios of climate change. Baseline Q0 simulations, using historic climate observations, reflected the current distribution of H. contortus in Europe. In northern Europe, the distribution of H. contortus is currently limited by temperatures falling below the development threshold during the winter months and within-host arrested development is necessary for population persistence over winter. In southern Europe, H. contortus infection pressure is limited during the summer months by increased temperature and decreased moisture. Compared with this baseline, Q0 simulations driven by a climate model ensemble predicted an increase in H. contortus infection pressure by the 2080s. In northern Europe, a temporal range expansion was predicted as the mean period of transmission increased by 2-3 months. A bimodal seasonal pattern of infection pressure, similar to that currently observed in southern Europe, emerges in northern Europe due to increasing summer temperatures and decreasing moisture. The predicted patterns of change could alter the epidemiology of H. contortus in Europe, affect the future sustainability of contemporary

  4. Added value. Collaboration on mitigating climate change in coastal towns by community driven processes

    DEFF Research Database (Denmark)

    Mechlenborg, Mette; Hansen, Jesper Rohr

    2018-01-01

    How should the collaborations between private and public landowners be organized and driven in order to make the mitigation of coastal towns and lines more innovative, economic and environmental sustainable?......How should the collaborations between private and public landowners be organized and driven in order to make the mitigation of coastal towns and lines more innovative, economic and environmental sustainable?...

  5. Orbital Noise in the Earth System is a Common Cause of Climate and Greenhouse-Gas Fluctuation

    Science.gov (United States)

    Liu, H. S.; Kolenkiewicz, R.; Wade, C., Jr.; Smith, David E. (Technical Monitor)

    2002-01-01

    The mismatch between fossil isotopic data and climate models known as the cool-tropic paradox implies that either the data are flawed or we understand very little about the climate models of greenhouse warming. Here we question the validity of the climate models on the scientific background of orbital noise in the Earth system. Our study shows that the insolation pulsation induced by orbital noise is the common cause of climate change and atmospheric concentrations of carbon dioxide and methane. In addition, we find that the intensity of the insolation pulses is dependent on the latitude of the Earth. Thus, orbital noise is the key to understanding the troubling paradox in climate models.

  6. Climate-Driven Changes Within the Larch Forest of Northern Siberia

    Science.gov (United States)

    Kharuk, V.

    2015-12-01

    Thanks to the support of NASA's Carbon Cycle and Ecosystem Focus Area programs, joint NASA/ Siberian Branch of the Russian Academy of Sciences studies have been conducted throughout Siberia. The overall objective has been to obtain field and satellite measurements to examine carbon stocks and track changes in forests across this vast area. In this presentation, we discuss some of the finding from this 25+ year collaboration' i.e., observed climate-driven changes within larch communities in northern Siberia. Field measurements and satellite data, including Terra/MODIS, Landsat, GRACE and QuickBird were used for analysis of forest conditions. The following results will be discussed. (1). At the northern limit of larch (Larix gmelinii) range (i.e.,~72°N) tree mortality was observed during the cooling period from the 16th century to the beginning of the 19th century. Post- Little Ice Age (LIA) trees re-establishment followed warming temperatures by the middle of the19th century. The current tree line has recovered to the pre-LIA line location although tree heights and stand densities are comparatively lower. The mean rate of upward migration was found to be 0.35 m yr-1 (with a range of 0.21-0.58). (2) The migration of the "dark needle conifers" (DNC: Abies sibirica, Pinus sibirica, Picea obovata) into the southern margin zone of larch dominated forest was documented. Meanwhile, within the traditional DNC range decline and mortality of both Siberian pine and fir were observed and attributed, primarily, due to an increased drought. (3) Within Central Siberia larch growth is limited by early summer temperatures and available water from thawing permafrost. Larch tree ring width (TRW) correlated with early summer temperatures and water vapor pressure (r = 0.73 and r = 0.69, respectively), drought (SPEI; r = 0.68-0.82), snow accumulation (r = 0.61), previous year precipitation (r = 0.63) and soil water anomalies (r = 0.79). Larch TRW growth and Gross Primary Productivity

  7. Stable isotope ratios in swale sequences of Lake Superior as indicators of climate and lake level fluctuations during the Late Holocene

    Science.gov (United States)

    Sharma, Shruti; Mora, G.; Johnston, J.W.; Thompson, T.A.

    2005-01-01

    Beach ridges along the coastline of Lake Superior provide a long-term and detailed record of lake level fluctuations for the past 4000 cal BP. Although climate change has been invoked to explain these fluctuations, its role is still in debate. Here, we reconstruct water balance by employing peat samples collected from swale deposits present between beach ridge sequences at two locations along the coastline of Lake Superior. Carbon isotope ratios for Sphagnum remains from these peat deposits are used as a proxy for water balance because the presence or absence of water films on Sphagnum controls the overall isotope discrimination effects. Consequently, increased average water content in Sphagnum produces elevated ??13C values. Two maxima of Sphagnum ??13C values interpreted to reflect wetter conditions prevailed from 3400 to 2400 cal BP and from about 1900 to 1400 cal BP. There are two relatively short drier periods as inferred from low Sphagnum ??13C values: one is centered at about 2300 cal BP, and one begins at 1400 cal BP. A good covariance was found between Sphagnum ??13C values and reconstructed lake-levels for Lake Michigan in which elevated carbon isotope values correlate well with higher lake levels. Based on this covariance, we conclude that climate exerts a strong influence on lake levels in Lake Superior for the past 4000 cal BP. ?? 2005 Elsevier Ltd. All rights reserved.

  8. Spatially explicit integrated modeling and economic valuation of climate driven land use change and its indirect effects.

    Science.gov (United States)

    Bateman, Ian; Agarwala, Matthew; Binner, Amy; Coombes, Emma; Day, Brett; Ferrini, Silvia; Fezzi, Carlo; Hutchins, Michael; Lovett, Andrew; Posen, Paulette

    2016-10-01

    We present an integrated model of the direct consequences of climate change on land use, and the indirect effects of induced land use change upon the natural environment. The model predicts climate-driven shifts in the profitability of alternative uses of agricultural land. Both the direct impact of climate change and the induced shift in land use patterns will cause secondary effects on the water environment, for which agriculture is the major source of diffuse pollution. We model the impact of changes in such pollution on riverine ecosystems showing that these will be spatially heterogeneous. Moreover, we consider further knock-on effects upon the recreational benefits derived from water environments, which we assess using revealed preference methods. This analysis permits a multi-layered examination of the economic consequences of climate change, assessing the sequence of impacts from climate change through farm gross margins, land use, water quality and recreation, both at the individual and catchment scale. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Climate-Driven Reshuffling of Species and Genes: Potential Conservation Roles for Species Translocations and Recombinant Hybrid Genotypes

    Directory of Open Access Journals (Sweden)

    Jon Mark Scriber

    2013-12-01

    Full Text Available Comprising 50%–75% of the world’s fauna, insects are a prominent part of biodiversity in communities and ecosystems globally. Biodiversity across all levels of biological classifications is fundamentally based on genetic diversity. However, the integration of genomics and phylogenetics into conservation management may not be as rapid as climate change. The genetics of hybrid introgression as a source of novel variation for ecological divergence and evolutionary speciation (and resilience may generate adaptive potential and diversity fast enough to respond to locally-altered environmental conditions. Major plant and herbivore hybrid zones with associated communities deserve conservation consideration. This review addresses functional genetics across multi-trophic-level interactions including “invasive species” in various ecosystems as they may become disrupted in different ways by rapid climate change. “Invasive genes” (into new species and populations need to be recognized for their positive creative potential and addressed in conservation programs. “Genetic rescue” via hybrid translocations may provide needed adaptive flexibility for rapid adaptation to environmental change. While concerns persist for some conservationists, this review emphasizes the positive aspects of hybrids and hybridization. Specific implications of natural genetic introgression are addressed with a few examples from butterflies, including transgressive phenotypes and climate-driven homoploid recombinant hybrid speciation. Some specific examples illustrate these points using the swallowtail butterflies (Papilionidae with their long-term historical data base (phylogeographical diversity changes and recent (3-decade climate-driven temporal and genetic divergence in recombinant homoploid hybrids and relatively recent hybrid speciation of Papilio appalachiensis in North America. Climate-induced “reshuffling” (recombinations of species composition, genotypes

  10. Climate-Driven Reshuffling of Species and Genes: Potential Conservation Roles for Species Translocations and Recombinant Hybrid Genotypes.

    Science.gov (United States)

    Scriber, Jon Mark

    2013-12-24

    Comprising 50%-75% of the world's fauna, insects are a prominent part of biodiversity in communities and ecosystems globally. Biodiversity across all levels of biological classifications is fundamentally based on genetic diversity. However, the integration of genomics and phylogenetics into conservation management may not be as rapid as climate change. The genetics of hybrid introgression as a source of novel variation for ecological divergence and evolutionary speciation (and resilience) may generate adaptive potential and diversity fast enough to respond to locally-altered environmental conditions. Major plant and herbivore hybrid zones with associated communities deserve conservation consideration. This review addresses functional genetics across multi-trophic-level interactions including "invasive species" in various ecosystems as they may become disrupted in different ways by rapid climate change. "Invasive genes" (into new species and populations) need to be recognized for their positive creative potential and addressed in conservation programs. "Genetic rescue" via hybrid translocations may provide needed adaptive flexibility for rapid adaptation to environmental change. While concerns persist for some conservationists, this review emphasizes the positive aspects of hybrids and hybridization. Specific implications of natural genetic introgression are addressed with a few examples from butterflies, including transgressive phenotypes and climate-driven homoploid recombinant hybrid speciation. Some specific examples illustrate these points using the swallowtail butterflies (Papilionidae) with their long-term historical data base (phylogeographical diversity changes) and recent (3-decade) climate-driven temporal and genetic divergence in recombinant homoploid hybrids and relatively recent hybrid speciation of Papilio appalachiensis in North America. Climate-induced "reshuffling" (recombinations) of species composition, genotypes, and genomes may become

  11. Evaluation of the application of a thermal insulation system: in-situ comparison of seasonal and daily climatic fluctuations

    Czech Academy of Sciences Publication Activity Database

    Fořt, J.; Beran, Pavel; Konvalinka, P.; Pavlík, Z.; Černý, R.

    2017-01-01

    Roč. 57, č. 3 (2017), s. 159-166 ISSN 1210-2709 R&D Projects: GA ČR(CZ) GBP105/12/G059 Institutional support: RVO:68378297 Keywords : in-situ monitoring * temperature * relative humidity * thermal insulation * energy sustainability * seasonal fluctuations Subject RIV: JN - Civil Engineering OBOR OECD: Construction engineering, Municipal and structural engineering https://ojs.cvut.cz/ojs/index.php/ap/article/view/4087/4171

  12. Landscape change and human response during a thousand years of climatic fluctuation and volcanism: Skaftafell, Southeast Iceland

    Directory of Open Access Journals (Sweden)

    Ives, Jack D.

    1991-06-01

    Full Text Available climatic fluctuation and volcanism: Skaftafell, Southeast Iceland ABSTRACT- The ancient farm of Skaftafell, dating from the Saga Period in Icelandic history is taken as the center-piece for depiction of climatic and landscape change from the earliest settlement in the ninth century AD to the present. The study of landscape evolution is divided into four main periods: 1 the Saga Period, AD 874-1350; 2 the beginning of glacier advance and volcanic activity, AD 1350-1500; 3 the Little Ice Age, AD 1500-1900; and 4 the Modern Period, AD 1900-1990. Is/laps have been produced to represent each period; they show the positions of farms which have survived far more than a thousand years, and churches that have been overwhelmed by catastrophic geomorphic processes, the positions of the glacier termini, melt water rivers, and main pasture lands. These reconstructions are based upon a mixture of physical evidence and folklore and historical documentation. Landscape evaluation is also described through the eyes of historic personalities who lived at Skaftafell. Survival of a rich culture in this region is remarkable in face of a series of almost overwhelming disasters. Today the biggest threat, or challenge and opportunity for sustainable development, is the vast influx of tourists to this region, one of the most isolated in the world. They are drawn to Skaftafell through the establishment of a National Park in one of the most scenically dramatic and beautiful landscapes in the world.

    [es] La antigua granja de Skaftafell, que data del período de Sagas de la Historia islandesa se ha tomado como el eje en torno al cual gira la explicación de los cambios climáticos y paisajísticos que han tenido lugar desde el primitivo asentamiento del siglo IX hasta el presente. El estudio de la evolución del paisaje se divide en cuatro períodos principales: 1 El Período de Sagas, 874-1350; 2 El principio del avance glaciar y la actividad volcánica, 1350

  13. A data-driven approach to identify controls on global fire activity from satellite and climate observations (SOFIA V1

    Directory of Open Access Journals (Sweden)

    M. Forkel

    2017-12-01

    Full Text Available Vegetation fires affect human infrastructures, ecosystems, global vegetation distribution, and atmospheric composition. However, the climatic, environmental, and socioeconomic factors that control global fire activity in vegetation are only poorly understood, and in various complexities and formulations are represented in global process-oriented vegetation-fire models. Data-driven model approaches such as machine learning algorithms have successfully been used to identify and better understand controlling factors for fire activity. However, such machine learning models cannot be easily adapted or even implemented within process-oriented global vegetation-fire models. To overcome this gap between machine learning-based approaches and process-oriented global fire models, we introduce a new flexible data-driven fire modelling approach here (Satellite Observations to predict FIre Activity, SOFIA approach version 1. SOFIA models can use several predictor variables and functional relationships to estimate burned area that can be easily adapted with more complex process-oriented vegetation-fire models. We created an ensemble of SOFIA models to test the importance of several predictor variables. SOFIA models result in the highest performance in predicting burned area if they account for a direct restriction of fire activity under wet conditions and if they include a land cover-dependent restriction or allowance of fire activity by vegetation density and biomass. The use of vegetation optical depth data from microwave satellite observations, a proxy for vegetation biomass and water content, reaches higher model performance than commonly used vegetation variables from optical sensors. We further analyse spatial patterns of the sensitivity between anthropogenic, climate, and vegetation predictor variables and burned area. We finally discuss how multiple observational datasets on climate, hydrological, vegetation, and socioeconomic variables together with

  14. A data-driven approach to identify controls on global fire activity from satellite and climate observations (SOFIA V1)

    Science.gov (United States)

    Forkel, Matthias; Dorigo, Wouter; Lasslop, Gitta; Teubner, Irene; Chuvieco, Emilio; Thonicke, Kirsten

    2017-12-01

    Vegetation fires affect human infrastructures, ecosystems, global vegetation distribution, and atmospheric composition. However, the climatic, environmental, and socioeconomic factors that control global fire activity in vegetation are only poorly understood, and in various complexities and formulations are represented in global process-oriented vegetation-fire models. Data-driven model approaches such as machine learning algorithms have successfully been used to identify and better understand controlling factors for fire activity. However, such machine learning models cannot be easily adapted or even implemented within process-oriented global vegetation-fire models. To overcome this gap between machine learning-based approaches and process-oriented global fire models, we introduce a new flexible data-driven fire modelling approach here (Satellite Observations to predict FIre Activity, SOFIA approach version 1). SOFIA models can use several predictor variables and functional relationships to estimate burned area that can be easily adapted with more complex process-oriented vegetation-fire models. We created an ensemble of SOFIA models to test the importance of several predictor variables. SOFIA models result in the highest performance in predicting burned area if they account for a direct restriction of fire activity under wet conditions and if they include a land cover-dependent restriction or allowance of fire activity by vegetation density and biomass. The use of vegetation optical depth data from microwave satellite observations, a proxy for vegetation biomass and water content, reaches higher model performance than commonly used vegetation variables from optical sensors. We further analyse spatial patterns of the sensitivity between anthropogenic, climate, and vegetation predictor variables and burned area. We finally discuss how multiple observational datasets on climate, hydrological, vegetation, and socioeconomic variables together with data-driven

  15. Potential ecological and economic consequences of climate-driven agricultural and silvicultural transformations in central Siberia

    Science.gov (United States)

    Tchebakova, Nadezhda M.; Zander, Evgeniya V.; Pyzhev, Anton I.; Parfenova, Elena I.; Soja, Amber J.

    2014-05-01

    Increased warming predicted from general circulation models (GCMs) by the end of the century is expected to dramatically impact Siberian forests. Both natural climate-change-caused disturbance (weather, wildfire, infestation) and anthropogenic disturbance (legal/illegal logging) has increased, and their impact on Siberian boreal forest has been mounting over the last three decades. The Siberian BioClimatic Model (SiBCliM) was used to simulate Siberian forests, and the resultant maps show a severely decreased forest that has shifted northwards and a changed composition. Predicted dryer climates would enhance the risks of high fire danger and thawing permafrost, both of which challenge contemporary ecosystems. Our current goal is to evaluate the ecological and economic consequences of climate warming, to optimise economic loss/gain effects in forestry versus agriculture, to question the relative economic value of supporting forestry, agriculture or a mixed agro-forestry at the southern forest border in central Siberia predicted to undergo the most noticeable landcover and landuse changes. We developed and used forest and agricultural bioclimatic models to predict forest shifts; novel tree species and their climatypes are introduced in a warmer climate and/or potential novel agriculture are introduced with a potential variety of crops by the end of the century. We applied two strategies to estimate climate change effects, motivated by forest disturbance. One is a genetic means of assisting trees and forests to be harmonized with a changing climate by developing management strategies for seed transfer to locations that are best ecologically suited to the genotypes in future climates. The second strategy is the establishment of agricultural lands in new forest-steppe and steppe habitats, because the forests would retreat northwards. Currently, food, forage, and biofuel crops primarily reside in the steppe and forest-steppe zones which are known to have favorable

  16. Climate-driven changes in the ecological stoichiometry of aquatic ecosystems

    NARCIS (Netherlands)

    van de Waal, D.B.; Verschoor, A.M.; Verspagen, J.M.H.; van Donk, E.; Huisman, J.

    2010-01-01

    Advances in ecological stoichiometry, a rapidly expanding research field investigating the elemental composition of organisms and their environment, have shed new light on the impacts of climate change on freshwater and marine ecosystems. Current changes in the Earth's climate alter the availability

  17. Potential Climate-driven Silvicultural and Agricultural Transformations in Siberia in the 21 Century

    Science.gov (United States)

    Tchebakova, N. M.; Parfenova, E. I.; Shvetsov, E.; Soja, A. J.

    2017-12-01

    Simulations of Siberian forests in a changing climate showed them to be changed in composition, decreased, and shifted northwards. Our goals were to evaluate the ecological consequences for the forests and agriculture in Siberia and to offer adaptive measures that may be undertaken to minimize negative consequences and maximize benefits from a rapidly changing environment in the socially important region of southern Siberia. We considered two strategies to estimate climate-change effects on potentially failing forests within an expanding forest-steppe ecotone. To support forestry, seed transfers from locations that are best suited to the genotypes in future climates may be applied to assist trees and forests in a changing climate. To support agriculture, in view of the growing world concerns on food safety, new farming lands may be established in a new forest-steppe ecotone with its favorable climatic and soil resources. We used our bioclimatic vegetation models of various levels: a forest type model to predict forest shifts and forest-failing lands, tree species range and their climatypes models to predict what tree species/climatype would be suitable and crop models to predict crops to introduce in potentially climate-disturbed areas in Siberia. Climate change data for the 2080s were calculated from the ensemble of 20 general circulation models of the Coupled Model Intercomparison Project phase 5 (CMIP5) and two scenarios to characterize the range of climate change: mild climate (RCP2.6 scenario) and sharp climate (RCP 8.5 scenario). By the 2080s, forest-steppe and steppe rather than forests would dominate up to half of Siberia in the warmer and dryer RCP 8.5 climate. Water stress tolerant and fire-resistant light-needled species Pinus sylvestris and Larix spp. would dominate the forest-steppe ecotone. Failing forests in a dryer climate may be maintained by moving and substituting proper climatypes from locations often hundreds of km away. Agriculture in Siberia

  18. Climate-Driven Risk of Large Fire Occurrence in the Western United States, 1500 to 2003

    Science.gov (United States)

    Crockett, J.; Westerling, A. L.

    2017-12-01

    Spatially comprehensive fire climatology has provided managers with tools to understand thecauses and consequences of large forest wildfires, but a paleoclimate context is necessary foranticipating the trajectory of future climate-fire relationships. Although accumulated charcoalrecords and tree scars have been utilized in high resolution, regional fire reconstructions, there isuncertainty as to how current climate-fire relationships of the western United States (WUS) fitwithin the natural long-term variability. While contemporary PDSI falls within the naturalvariability of the past, contemporary temperatures skew higher. Here, we develop a WUSfire reconstruction by applying climate-fire-topography model built on the 1972 to 2003 periodto the past 500 years, validated by recently updated fire-scar histories from WUS forests. Theresultant narrative provides insight into changing climate-fire relationships during extendedperiods of high aridity and temperature, providing land managers with historical precedent toeffectively anticipate disturbances during future climate change.

  19. Potential distribution of Podocnemis lewyana (Reptilia: Podocnemididae) and its possible fluctuation under different global climate change scenarios

    International Nuclear Information System (INIS)

    Ortiz Yusty, Carlos; Restrepo, Adriana; Paez, Vivian P

    2014-01-01

    We implemented a species distribution modelling approach to establish the potential distribution of Podocnemis lewyana, to explore the climatic factors that may influence the species' distribution and to evaluate possible changes in distribution under future climate scenarios. The distribution models predicted a continuous distribution from south to north along the Magdalena River, from Rivera and Palermo in the Department of Huila to the departments of Atlantico and Magdalena in the north. Temperature was the variable most influential in the distribution of P. lewyana; this species tends to be present in warm regions with low temperature variability. The distribution model predicted an increase in the geographic range of P. lewyana under climate change scenarios. However, taking into account the habitat preferences of this species and its strong association with water, this result should be treated with caution since the model considered only terrestrial climatic variables. Given the life history characteristics of this species (temperature dependent sex determination, high pivotal temperature and a very narrow transition range) and the negative effect of changes in hydrological regimes on embryo survival, expansion of the potential distribution of P. lewyana in the future does not mean that the species will not be affected by global climate change.

  20. Climatic fluctuations as a significant contributing factor for volcanic collapses. Evidence from Mexico during the Late Pleistocene

    Science.gov (United States)

    Capra, L.; Bernal-Uruchurtu, J. P.; Carrasco, G.

    2013-05-01

    Climate oscillations have significantly contributed to the planet's evolution, including volcanic activity. Major glaciations have been considered not only as a triggering mechanism for large magmatic eruptions but also inducing volcano instability. Generally, volcano instability can be inferred from detailed volcanological and structural studies of a volcano and its associated depositional sequence, but the triggering mechanism has been always difficult to infer. In this paper, we present evidence of how climatic variations during the Late Pleistocene could have forced sector collapses of the main Mexican stratovolcanoes and enhanced the mobility of associated massive flows inducing the transformation of debris avalanche into debris flows. In particular, the climatic record based on atmospheric moisture content from robustly dated lake record from Guatemala and a U/Th dated speleothem from New Mexico are used here as indicators of summer and winter precipitation. Depositional sequences associated with Late Pleistocene sector collapses of Volcan de Colima, Nevado de Toluca, Citlaltepetl (Pico de Orizaba) and Cofre de Perote volcanoes are here analyzed. Comparing the timing of the event with the climatic record, a combination of summer and/or winter pluvial conditions could have forced and triggered the failure of already unstable volcanoes, even during glacier advances (as for the Citlaltepetl event). Independently of the main cause of the volcano instability (magmatic or tectonic) it is important to highlight that the climatic factor played an important role in enhancing the volcano instability and promoted the lateral transformation of debris avalanches, which under dry conditions would have affected more limited areas.

  1. Remote Sensing-Driven Climatic/Environmental Variables for Modelling Malaria Transmission in Sub-Saharan Africa

    Directory of Open Access Journals (Sweden)

    Osadolor Ebhuoma

    2016-06-01

    Full Text Available Malaria is a serious public health threat in Sub-Saharan Africa (SSA, and its transmission risk varies geographically. Modelling its geographic characteristics is essential for identifying the spatial and temporal risk of malaria transmission. Remote sensing (RS has been serving as an important tool in providing and assessing a variety of potential climatic/environmental malaria transmission variables in diverse areas. This review focuses on the utilization of RS-driven climatic/environmental variables in determining malaria transmission in SSA. A systematic search on Google Scholar and the Institute for Scientific Information (ISI Web of KnowledgeSM databases (PubMed, Web of Science and ScienceDirect was carried out. We identified thirty-five peer-reviewed articles that studied the relationship between remotely-sensed climatic variable(s and malaria epidemiological data in the SSA sub-regions. The relationship between malaria disease and different climatic/environmental proxies was examined using different statistical methods. Across the SSA sub-region, the normalized difference vegetation index (NDVI derived from either the National Oceanic and Atmospheric Administration (NOAA Advanced Very High Resolution Radiometer (AVHRR or Moderate-resolution Imaging Spectrometer (MODIS satellite sensors was most frequently returned as a statistically-significant variable to model both spatial and temporal malaria transmission. Furthermore, generalized linear models (linear regression, logistic regression and Poisson regression were the most frequently-employed methods of statistical analysis in determining malaria transmission predictors in East, Southern and West Africa. By contrast, multivariate analysis was used in Central Africa. We stress that the utilization of RS in determining reliable malaria transmission predictors and climatic/environmental monitoring variables would require a tailored approach that will have cognizance of the geographical/climatic

  2. Remote Sensing-Driven Climatic/Environmental Variables for Modelling Malaria Transmission in Sub-Saharan Africa.

    Science.gov (United States)

    Ebhuoma, Osadolor; Gebreslasie, Michael

    2016-06-14

    Malaria is a serious public health threat in Sub-Saharan Africa (SSA), and its transmission risk varies geographically. Modelling its geographic characteristics is essential for identifying the spatial and temporal risk of malaria transmission. Remote sensing (RS) has been serving as an important tool in providing and assessing a variety of potential climatic/environmental malaria transmission variables in diverse areas. This review focuses on the utilization of RS-driven climatic/environmental variables in determining malaria transmission in SSA. A systematic search on Google Scholar and the Institute for Scientific Information (ISI) Web of Knowledge(SM) databases (PubMed, Web of Science and ScienceDirect) was carried out. We identified thirty-five peer-reviewed articles that studied the relationship between remotely-sensed climatic variable(s) and malaria epidemiological data in the SSA sub-regions. The relationship between malaria disease and different climatic/environmental proxies was examined using different statistical methods. Across the SSA sub-region, the normalized difference vegetation index (NDVI) derived from either the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) or Moderate-resolution Imaging Spectrometer (MODIS) satellite sensors was most frequently returned as a statistically-significant variable to model both spatial and temporal malaria transmission. Furthermore, generalized linear models (linear regression, logistic regression and Poisson regression) were the most frequently-employed methods of statistical analysis in determining malaria transmission predictors in East, Southern and West Africa. By contrast, multivariate analysis was used in Central Africa. We stress that the utilization of RS in determining reliable malaria transmission predictors and climatic/environmental monitoring variables would require a tailored approach that will have cognizance of the geographical/climatic

  3. Hydrological simulations driven by RCM climate scenarios at basin scale in the Po River, Italy

    Directory of Open Access Journals (Sweden)

    R. Vezzoli

    2014-09-01

    Full Text Available River discharges are the main expression of the hydrological cycle and are the results of climate natural variability. The signal of climate changes occurrence raises the question of how it will impact on river flows and on their extreme manifestations: floods and droughts. This question can be addressed through numerical simulations spanning from the past (1971 to future (2100 under different climate change scenarios. This work addresses the capability of a modelling chain to reproduce the observed discharge of the Po River over the period 1971–2000. The modelling chain includes climate and hydrological/hydraulic models and its performance is evaluated through indices based on the flow duration curve. The climate datasets used for the 1971–2000 period are (a a high resolution observed climate dataset, and COSMO-CLM regional climate model outputs with (b perfect boundary condition, ERA40 Reanalysis, and (c suboptimal boundary conditions provided by the global climate model CMCC–CM. The aim of the different simulations is to evaluate how the uncertainties introduced by the choice of the regional and/or global climate models propagate in the simulated discharges. This point is relevant to interpret the results of the simulated discharges when scenarios for the future are considered. The hydrological/hydraulic components are simulated through a physically-based distributed model (TOPKAPI and a water balance model at the basin scale (RIBASIM. The aim of these first simulations is to quantify the uncertainties introduced by each component of the modelling chain and their propagation. Estimation of the overall uncertainty is relevant to correctly understand the future river flow regimes. The results show how bias correction algorithms can help in reducing the overall uncertainty associated to the different stages of the modelling chain.

  4. Loco or no loco? Holocene climatic fluctuations, human demography and community base management of coastal resources in northern Chile

    Science.gov (United States)

    Santoro, Calogero M.; Gayo, Eugenia M.; Carter, Chris; Standen, Vivien G.; Castro, Victoria; Valenzuela, Daniela; De Pol-Holz, Ricardo; Marquet, Pablo A.; Latorre, Claudio

    2017-10-01

    The abundance of the southern Pacific mollusk loco (Concholepas concholepas), among other conspicuous marine supplies, are often cited as critical resources behind the long-term cultural and demographic fluctuations of prehistoric hunter-gatherers at the coastal Atacama Desert. These societies inhabited one of the world’s most productive marine environments flanked by one the world’s driest deserts. Both of these environments have witnessed significant ecological variation since people first colonized them at the end of the Pleistocene (c. 13,000 cal yr BP). Here, we examine the relationship between the relative abundance of shellfish (a staple resource) along a 9,500-year sequence of archaeological shell midden accumulations at Caleta (a small inlet or cove) Vitor, with past demographic trends (established via summed probability distributions of radiocarbon ages) and technological innovations together with paleoceanographic data on past primary productivity. We find that shellfish extraction varied considerably from one cultural period to the next in terms of the number of species and their abundance, with diversity increasing during periods of regionally decreased productivity. Such shifts in consumption patterns are considered community based management decisions, and for the most part they were synchronous with large and unusual regional demographic fluctuations experienced by prehistoric coastal societies in northern Chile. When taken together with their technological innovations, our data illustrates how these human groups tailored their socio-cultural patterns to what were often abrupt and prolonged environmental changes throughout the Holocene.

  5. Loco or no Loco? Holocene Climatic Fluctuations, Human Demography, and Community Based Management of Coastal Resources in Northern Chile

    Directory of Open Access Journals (Sweden)

    Calogero M. Santoro

    2017-10-01

    Full Text Available The abundance of the southern Pacific mollusk loco (Concholepas concholepas, among other conspicuous marine supplies, are often cited as critical resources behind the long-term cultural and demographic fluctuations of prehistoric hunter-gatherers in the coastal Atacama Desert. These societies inhabited one of the world's most productive marine environments flanked by one the world's driest deserts. Both of these environments have witnessed significant ecological variation since people first colonized them at the end of the Pleistocene (c. 13,000 cal yr BP. Here, we examine the relationship between the relative abundance of shellfish (a staple resource along a 9,500-year sequence of archeological shell midden accumulations at Caleta (a small inlet or cove Vitor, with past demographic trends (established via summed probability distributions of radiocarbon ages and technological innovations together with paleoceanographic data on past primary productivity. We find that shellfish extraction varied considerably from one cultural period to the next in terms of the number of species and their abundance, with diversity increasing during periods of regionally decreased productivity. Such shifts in consumption patterns are considered community based management decisions, and for the most part they were synchronous with large and unusual regional demographic fluctuations experienced by prehistoric coastal societies in northern Chile. When taken together with their technological innovations, our data illustrates how these human groups tailored their socio-cultural patterns to what were often abrupt and prolonged environmental changes throughout the Holocene.

  6. Fully Quantum Fluctuation Theorems

    Science.gov (United States)

    Åberg, Johan

    2018-02-01

    Systems that are driven out of thermal equilibrium typically dissipate random quantities of energy on microscopic scales. Crooks fluctuation theorem relates the distribution of these random work costs to the corresponding distribution for the reverse process. By an analysis that explicitly incorporates the energy reservoir that donates the energy and the control system that implements the dynamic, we obtain a quantum generalization of Crooks theorem that not only includes the energy changes in the reservoir but also the full description of its evolution, including coherences. Moreover, this approach opens up the possibility for generalizations of the concept of fluctuation relations. Here, we introduce "conditional" fluctuation relations that are applicable to nonequilibrium systems, as well as approximate fluctuation relations that allow for the analysis of autonomous evolution generated by global time-independent Hamiltonians. We furthermore extend these notions to Markovian master equations, implicitly modeling the influence of the heat bath.

  7. Climate-driven coral reorganisation influences aggressive behaviour in juvenile coral-reef fishes

    Science.gov (United States)

    Kok, Judith E.; Graham, Nicholas A. J.; Hoogenboom, Mia O.

    2016-06-01

    Globally, habitat degradation is altering the abundance and diversity of species in a variety of ecosystems. This study aimed to determine how habitat degradation, in terms of changing coral composition under climate change, affected abundance, species richness and aggressive behaviour of juveniles of three damselfishes ( Pomacentrus moluccensis, P. amboinensis and Dischistodus perspicillatus, in order of decreasing reliance on coral). Patch reefs were constructed to simulate two types of reefs: present-day reefs that are vulnerable to climate-induced coral bleaching, and reefs with more bleaching-robust coral taxa, thereby simulating the likely future of coral reefs under a warming climate. Fish communities were allowed to establish naturally on the reefs during the summer recruitment period. Climate-robust reefs had lower total species richness of coral-reef fishes than climate-vulnerable reefs, but total fish abundance was not significantly different between reef types (pooled across all species and life-history stages). The nature of aggressive interactions, measured as the number of aggressive chases, varied according to coral composition; on climate-robust reefs, juveniles used the substratum less often to avoid aggression from competitors, and interspecific aggression became relatively more frequent than intraspecific aggression for juveniles of the coral-obligate P. moluccensis. This study highlights the importance of coral composition as a determinant of behaviour and diversity of coral-reef fishes.

  8. Climate-driven disturbances in the San Juan River sub-basin of the Colorado River

    Science.gov (United States)

    Bennett, Katrina E.; Bohn, Theodore J.; Solander, Kurt; McDowell, Nathan G.; Xu, Chonggang; Vivoni, Enrique; Middleton, Richard S.

    2018-01-01

    Accelerated climate change and associated forest disturbances in the southwestern USA are anticipated to have substantial impacts on regional water resources. Few studies have quantified the impact of both climate change and land cover disturbances on water balances on the basin scale, and none on the regional scale. In this work, we evaluate the impacts of forest disturbances and climate change on a headwater basin to the Colorado River, the San Juan River watershed, using a robustly calibrated (Nash-Sutcliffe efficiency 0.76) hydrologic model run with updated formulations that improve estimates of evapotranspiration for semi-arid regions. Our results show that future disturbances will have a substantial impact on streamflow with implications for water resource management. Our findings are in contradiction with conventional thinking that forest disturbances reduce evapotranspiration and increase streamflow. In this study, annual average regional streamflow under the coupled climate-disturbance scenarios is at least 6-11 % lower than those scenarios accounting for climate change alone; for forested zones of the San Juan River basin, streamflow is 15-21 % lower. The monthly signals of altered streamflow point to an emergent streamflow pattern related to changes in forests of the disturbed systems. Exacerbated reductions of mean and low flows under disturbance scenarios indicate a high risk of low water availability for forested headwater systems of the Colorado River basin. These findings also indicate that explicit representation of land cover disturbances is required in modeling efforts that consider the impact of climate change on water resources.

  9. CLIMOOR. Climate driven changes in the functioning of heath and moorland ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Beier, C. [ed.; Tietema, A.; Riis Nielsen, T.; Emmett, B.; Estiarte, M.; Penuelas, J.; Llorens Guash, L.; Williams, D.; Gordon, C.; Pugh, B.; Roda, F.; Gundersen, P.; Gorissen, A.

    2000-01-01

    Emission of green house gases, partly generated from human activities, reduces the loss of heat from the earth thereby potentially causing climate change. This change in climate has been predicted to result in a 1-3 deg. C increase in temperature with more vigorous rainstorms and prolonged drought periods in the coming 100 years. The consequence of such climatic changes for the terrestrial ecosystems are largely unknown. In order to improve our understanding of the ecosystem response to climate change and thereby to improve the basis for the international negotiations and political decisions to avoid or minimise climate change and its effects, a European research project CLIMOOR has been initiated. The project is a cross European research project involving 6 research groups from Denmark, the Netherlands, UK and Spain and is funded by EU and the participating institutions. The project investigates the potential effects of warming and drought on heath and moorland ecosystems at four European sites. The ecosystems are manipulated at field scale by reducing the heat loss at night by IR-reflective curtains and by removing the precipitation during a 2 month period in the summer. The effects of these manipulations on the plants and the soil are studied. This report describes the technique used to apply the climate change at field scale and presents some preliminary results after the first growing season. EU and the participating institutions fund CLIMOOR. (au)

  10. Short-term fluctuations in vegetation and phytoplankton during the Middle Eocene greenhouse climate: a 640-kyr record from the Messel oil shale (Germany)

    Science.gov (United States)

    Lenz, Olaf K.; Wilde, Volker; Riegel, Walter

    2011-11-01

    The Palaeogene was the most recent greenhouse period on Earth. Especially for the Late Palaeocene and Early Eocene, several superimposed short-term hyperthermal events have been described, including extremes such as the Palaeocene-Eocene Thermal Maximum. Major faunal and floral turnovers in the marine and terrestrial realms were recorded in association with these events. High-resolution palynological analysis of the early Middle Eocene maar lake sediments at Messel, near Darmstadt, Germany, provides an insight into the dynamics of a climax vegetation during the Middle Eocene greenhouse climate in a time span without significant climatic excursions. Numerical techniques like detrended correspondence analysis and wavelet analysis have been applied to recognize cyclic fluctuations and long-term trends in the vegetation through a time interval of approximately 640 kyr. Based on the numerical zoning of the pollen diagram, three phases in the development of the vegetation may be distinguished. Throughout these phases, the climax vegetation did not change substantially in qualitative composition, but a trend towards noticeably less humid conditions probably in combination with a drop of the water level in the lake may be recognized. A shift in algal population from the freshwater dinoflagellate cyst Messelodinium thielepfeifferae to a dominance of Botryococcus in the uppermost part of the core is interpreted as a response to changes in acidity and nutrient availability within the lake. Time series analyses of pollen assemblages show that variations in the Milankovitch range of eccentricity, obliquity and precession can be distinguished. In addition, fluctuations in the sub-Milankovitch range are indicated. This demonstrates that floral changes during steady depositional conditions in the Middle Eocene of Messel were controlled by orbital forcing.

  11. Groundwater movement on a Low-lying Carbonate Atoll Island and its Response to Climatic and Sea-level Fluctuations: Roi Namur, Republic of the Marshall Islands

    Science.gov (United States)

    Oberle, F. J.; Swarzenski, P. W.; Storlazzi, C. D.

    2017-12-01

    Atoll islands, most of which only average 1-2 meters above today's sea level, provide a tremendous natural laboratory in which to study and better understand the intensifying impacts of high rates of sea-level rise on tropical reef-lined islands. These islands are unique and on the frontline of negative societal impacts due to their geologic structure and limited water supply. Groundwater resources on atolls are typically minimal due to the low elevation and small surface area of the islands and are also subject to recurring droughts, and more frequent, storm-driven seawater overwash events. Although groundwater is the principal means of freshwater storage on atoll islands and is a major factor in determining the overall sustainability of island settlements, hydrological data on how an aquifer will response to changes in sea-level rise or storm-driven overwash remain limited. Here we present high-resolution time series hydrogeological and geochemical data from a 16 month study to determine the role of an atoll's carbonate geology, land use, and atmospheric and oceanographic forcing in driving coastal groundwater exchange including submarine groundwater discharge on the island of Roi-Namur on Kwajalein Atoll in the Republic of the Marshall Islands. This information can provide new estimates on the recovery and resilience of coastal groundwater resources on similar islands that are expected to experience climate change-driven perturbations.

  12. Projections of climate-driven changes in tuna vertical habitat based on species-specific differences in blood oxygen affinity.

    Science.gov (United States)

    Mislan, K A S; Deutsch, Curtis A; Brill, Richard W; Dunne, John P; Sarmiento, Jorge L

    2017-10-01

    Oxygen concentrations are hypothesized to decrease in many areas of the ocean as a result of anthropogenically driven climate change, resulting in habitat compression for pelagic animals. The oxygen partial pressure, pO 2 , at which blood is 50% saturated (P 50 ) is a measure of blood oxygen affinity and a gauge of the tolerance of animals for low ambient oxygen. Tuna species display a wide range of blood oxygen affinities (i.e., P 50 values) and therefore may be differentially impacted by habitat compression as they make extensive vertical movements to forage on subdaily time scales. To project the effects of end-of-the-century climate change on tuna habitat, we calculate tuna P 50 depths (i.e., the vertical position in the water column at which ambient pO 2 is equal to species-specific blood P 50 values) from 21st century Earth System Model (ESM) projections included in the fifth phase of the Climate Model Intercomparison Project (CMIP5). Overall, we project P 50 depths to shoal, indicating likely habitat compression for tuna species due to climate change. Tunas that will be most impacted by shoaling are Pacific and southern bluefin tunas-habitat compression is projected for the entire geographic range of Pacific bluefin tuna and for the spawning region of southern bluefin tuna. Vertical shifts in P 50 depths will potentially influence resource partitioning among Pacific bluefin, bigeye, yellowfin, and skipjack tunas in the northern subtropical and eastern tropical Pacific Ocean, the Arabian Sea, and the Bay of Bengal. By establishing linkages between tuna physiology and environmental conditions, we provide a mechanistic basis to project the effects of anthropogenic climate change on tuna habitats. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

  13. Climate-driven Sympatry does not Lead to Foraging Competition Between Adélie and Gentoo Penguins

    Science.gov (United States)

    Cimino, M. A.; Moline, M. A.; Fraser, W.; Patterson-Fraser, D.; Oliver, M. J.

    2016-02-01

    Climate-driven sympatry may lead to competition for food resources between species, population shifts and changes in ecosystem structure. Rapid warming in the West Antarctic Peninsula (WAP) is coincident with increasing gentoo penguin and decreasing Adélie penguin populations, suggesting that competition for food may exacerbate the Adélie penguin decline. At Palmer Station, we tested for foraging competition between these species by comparing their prey, Antarctic krill, distributions and penguin foraging behaviors on fine scales. To study these predator-prey dynamics, we simultaneously deployed penguin satellite transmitters, and a REMUS autonomous underwater vehicle that acoustically detected krill aggregations and measured physical and biological properties of the water column. We detected krill aggregations within the horizontal and vertical foraging ranges of Adélie and gentoo penguin. In the upper 100 m of the water column, the distribution of krill aggregations were mainly associated with CHL and light, suggesting that krill selected for habitats that balance the need to consume food and avoid predation. Adélie and gentoo penguins mainly had spatially segregated foraging areas but in areas of overlap, gentoo penguins switched foraging behavior by foraging at deeper depths, a strategy which limits competition with Adélie penguins. This suggests that climate-driven sympatry does not necessarily result in competitive exclusion. Contrary to a recent theory, which suggests that increased competition for krill is the major driver of Adélie penguin population declines, we suggest that declines in Adélie penguins along the WAP are more likely due to direct and indirect climate impacts on their life histories.

  14. Correlations between the geomagnetic field variations, the fluctuations of the earth`s rotation and climate change

    Energy Technology Data Exchange (ETDEWEB)

    Greiner-Mai, H; Jochmann, H

    1995-03-01

    The amplitude spectra of global geophysical phenomena were investigated to motivate research of physical connections between them. The suggested causality was derived from comparison of the spectra, and from cross correlation functions. The following global parameters were discussed: For the earth rotation by the variations of the length of day, for the geomagnetic variation by the global field intensity, changes of the dipole axis and the westward drift, and for climate change by the atmospheric excitation function derived from air pressure variations, and temperature variations. The model of atmospheric excitation, which can be proved most exactly for the annual variations of length of day, is responsible for the 11 and 22 years periods, too. It failed for longer periods, e.g. partially for the 30 years periods and completely for the 60 to 80 years periods, which were also discovered in the mean temperature and geomagnetic field variations. Therefore, it was suggested that longer periods in climate change and in the variations of the earth`s rotation are caused independently by the same process in the earth core, provided that a physical influence of the geomagnetic field on climate will be accepted in future. The investigation was completed by comparison with the spectra of some local temperature variations in Europe. (orig.)

  15. Interannual abundance changes of gelatinous carnivore zooplankton unveil climate-driven hydrographic variations in the Iberian Peninsula, Portugal.

    Science.gov (United States)

    D'Ambrosio, Mariaelena; Molinero, Juan C; Azeiteiro, Ulisses M; Pardal, Miguel A; Primo, Ana L; Nyitrai, Daniel; Marques, Sónia C

    2016-09-01

    The persistent massive blooms of gelatinous zooplankton recorded during recent decades may be indicative of marine ecosystem changes. In this study, we investigated the potential influence of the North Atlantic climate (NAO) variability on decadal abundance changes of gelatinous carnivore zooplankton in the Mondego estuary, Portugal, over the period 2003-2013. During the 11-year study, the community of gelatinous carnivores encompassed a larger diversity of hydromedusae than siphonophores; the former dominated by Obelia spp., Lizzia blondina, Clythia hemisphaerica, Liriope tetraphylla and Solmaris corona, while the latter dominated by Muggiaea atlantica. Gelatinous carnivore zooplankton displayed marked interannual variability and mounting species richness over the period examined. Their pattern of abundance shifted towards larger abundances ca. 2007 and significant phenological changes. The latter included a shift in the mean annual pattern (from unimodal to bimodal peak, prior and after 2007 respectively) and an earlier timing of the first annual peak concurrent with enhanced temperatures. These changes were concurrent with the climate-driven environmental variability mainly controlled by the NAO, which displayed larger variance after 2007 along with an enhanced upwelling activity. Structural equation modelling allowed depicting cascading effects derived from the NAO influence on regional climate and upwelling variability further shaping water temperature. Such cascading effect percolated the structure and dynamics of the community of gelatinous carnivore zooplankton in the Mondego estuary. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Assessment of climate-driven variations in malaria incidence in Swaziland: toward malaria elimination.

    Science.gov (United States)

    Chuang, Ting-Wu; Soble, Adam; Ntshalintshali, Nyasatu; Mkhonta, Nomcebo; Seyama, Eric; Mthethwa, Steven; Pindolia, Deepa; Kunene, Simon

    2017-06-01

    Swaziland aims to eliminate malaria by 2020. However, imported cases from neighbouring endemic countries continue to sustain local parasite reservoirs and initiate transmission. As certain weather and climatic conditions may trigger or intensify malaria outbreaks, identification of areas prone to these conditions may aid decision-makers in deploying targeted malaria interventions more effectively. Malaria case-surveillance data for Swaziland were provided by Swaziland's National Malaria Control Programme. Climate data were derived from local weather stations and remote sensing images. Climate parameters and malaria cases between 2001 and 2015 were then analysed using seasonal autoregressive integrated moving average models and distributed lag non-linear models (DLNM). The incidence of malaria in Swaziland increased between 2005 and 2010, especially in the Lubombo and Hhohho regions. A time-series analysis indicated that warmer temperatures and higher precipitation in the Lubombo and Hhohho administrative regions are conducive to malaria transmission. DLNM showed that the risk of malaria increased in Lubombo when the maximum temperature was above 30 °C or monthly precipitation was above 5 in. In Hhohho, the minimum temperature remaining above 15 °C or precipitation being greater than 10 in. might be associated with malaria transmission. This study provides a preliminary assessment of the impact of short-term climate variations on malaria transmission in Swaziland. The geographic separation of imported and locally acquired malaria, as well as population behaviour, highlight the varying modes of transmission, part of which may be relevant to climate conditions. Thus, the impact of changing climate conditions should be noted as Swaziland moves toward malaria elimination.

  17. Advancing the climate data driven crop-modeling studies in the dry areas of Northern Syria and Lebanon: an important first step for assessing impact of future climate.

    Science.gov (United States)

    Dixit, Prakash N; Telleria, Roberto

    2015-04-01

    Inter-annual and seasonal variability in climatic parameters, most importantly rainfall, have potential to cause climate-induced risk in long-term crop production. Short-term field studies do not capture the full nature of such risk and the extent to which modifications to crop, soil and water management recommendations may be made to mitigate the extent of such risk. Crop modeling studies driven by long-term daily weather data can predict the impact of climate-induced risk on crop growth and yield however, the availability of long-term daily weather data can present serious constraints to the use of crop models. To tackle this constraint, two weather generators namely, LARS-WG and MarkSim, were evaluated in order to assess their capabilities of reproducing frequency distributions, means, variances, dry spell and wet chains of observed daily precipitation, maximum and minimum temperature, and solar radiation for the eight locations across cropping areas of Northern Syria and Lebanon. Further, the application of generated long-term daily weather data, with both weather generators, in simulating barley growth and yield was also evaluated. We found that overall LARS-WG performed better than MarkSim in generating daily weather parameters and in 50 years continuous simulation of barley growth and yield. Our findings suggest that LARS-WG does not necessarily require long-term e.g., >30 years observed weather data for calibration as generated results proved to be satisfactory with >10 years of observed data except in area with higher altitude. Evaluating these weather generators and the ability of generated weather data to perform long-term simulation of crop growth and yield is an important first step to assess the impact of future climate on yields, and to identify promising technologies to make agricultural systems more resilient in the given region. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Runoff scenarios of the Ötz catchment (Tyrol, Austria) considering climate change driven changes of the cryosphere

    Science.gov (United States)

    Helfricht, Kay; Schneeberger, Klaus; Welebil, Irene; Schöber, Johannes; Huss, Matthias; Formayer, Herbert; Huttenlau, Matthias; Schneider, Katrin

    2014-05-01

    The seasonal distribution of runoff in alpine catchments is markedly influenced by the cryospheric contribution (snow and ice). Long-term climate change will alter these reservoirs and consequently have an impact on the water balance. Glacierized catchments like the Ötztal (Tyrol, Austria) are particularly sensitive to changes in the cryosphere and the hydrological changes related to them. The Ötztal possesses an outstanding role in Austrian and international cryospheric research and reacts sensitive to changes in hydrology due to its socio-economic structure (e.g. importance of tourism, hydro-power). In this study future glacier scenarios for the runoff calculations in the Ötztal catchment are developed. In addition to climatological scenario data, glacier scenarios were established for the hydrological simulation of future runoff. Glacier outlines and glacier surface elevation changes of the Austrian Glacier Inventory were used to derive present ice thickness distribution and scenarios of glacier area distribution. Direct effects of climate change (i.e. temperature and precipitation change) and indirect effects in terms of variations in the cryosphere were considered for the analysis of the mean runoff and particularly flood frequencies. Runoff was modelled with the hydrological model HQSim, which was calibrated for the runoff gauges at Brunau, Obergurgl and Vent. For a sensitivity study, the model was driven by separate glacier scenarios. Keeping glacier area constant, variable climate input was used to separate the effect of climate sensitivity. Results of the combination of changed glacier areas and changed climate input were subsequently analysed. Glacier scenarios show first a decrease in volume, before glacier area shrinks. The applied method indicates a 50% ice volume loss by 2050 relative to today. Further, model results show a reduction in glacier volume and area to less than 20% of the current ice cover towards the end of the 21st century. The effect

  19. Climate and air quality-driven scenarios of ozone and aerosol precursor abatement

    International Nuclear Information System (INIS)

    Rypdal, Kristin; Rive, Nathan; Berntsen, Terje; Fagerli, Hilde; Klimont, Zbigniew; Mideksa, Torben K.; Fuglestvedt, Jan S.

    2009-01-01

    In addition to causing domestic and regional environmental effects, many air pollutants contribute to radiative forcing (RF) of the climate system. However, climate effects are not considered when cost-effective abatement targets for these pollutants are established, nor are they included in current international climate agreements. We construct air pollution abatement scenarios in 2030 which target cost-effective reductions in RF in the EU, USA, and China and compare these to abatement scenarios which instead target regional ozone effects and particulate matter concentrations. Our analysis covers emissions of PM (fine, black carbon and organic carbon), SO 2 , NO x , CH 4 , VOCs, and CO. We find that the effect synergies are strong for PM/BC, VOC, CO and CH 4 . While an air quality strategy targeted at reducing ozone will also reduce RF, this will not be the case for a strategy targeting particulate matter. Abatement in China dominates RF reduction, but there are cheap abatement options also available in the EU and USA. The justification for international cooperation on air quality issues is underlined when the co-benefits of reduced RF are considered. Some species, most importantly SO 2 , contribute a negative forcing on climate. We suggest that given current knowledge, NO x and SO 2 should be ignored in RF-targeted abatement policies.

  20. Past climate-driven range shifts and population genetic diversity in arctic plants

    DEFF Research Database (Denmark)

    Pellissier, Loïc; Eidesen, Pernille Bronken; Ehrich, Dorothee

    2016-01-01

    High intra-specific genetic diversity is necessary for species adaptation to novel environments under climate change, but species tracking suitable conditions are losing alleles through successive founder events during range shift. Here, we investigated the relationship between range shift since ...... the Last Glacial Maximum (LGM) and extant population genetic diversity across multiple plant species to understand variability in species responses...

  1. Becoming a First Mover in Green Electricity Supply: Corporate Change Driven by Liberalisation and Climate Change

    NARCIS (Netherlands)

    Hofman, Peter

    2003-01-01

    This paper presents a study of a trend-setting company in the electricity sector in the Netherlands and its innovative response to the combined influence of liberalisation and climate change. The company became a first mover through its invention of the concept of green electricity and the

  2. Predicting climate-driven regime shifts versus rebound potential in coral reefs.

    Science.gov (United States)

    Graham, Nicholas A J; Jennings, Simon; MacNeil, M Aaron; Mouillot, David; Wilson, Shaun K

    2015-02-05

    Climate-induced coral bleaching is among the greatest current threats to coral reefs, causing widespread loss of live coral cover. Conditions under which reefs bounce back from bleaching events or shift from coral to algal dominance are unknown, making it difficult to predict and plan for differing reef responses under climate change. Here we document and predict long-term reef responses to a major climate-induced coral bleaching event that caused unprecedented region-wide mortality of Indo-Pacific corals. Following loss of >90% live coral cover, 12 of 21 reefs recovered towards pre-disturbance live coral states, while nine reefs underwent regime shifts to fleshy macroalgae. Functional diversity of associated reef fish communities shifted substantially following bleaching, returning towards pre-disturbance structure on recovering reefs, while becoming progressively altered on regime shifting reefs. We identified threshold values for a range of factors that accurately predicted ecosystem response to the bleaching event. Recovery was favoured when reefs were structurally complex and in deeper water, when density of juvenile corals and herbivorous fishes was relatively high and when nutrient loads were low. Whether reefs were inside no-take marine reserves had no bearing on ecosystem trajectory. Although conditions governing regime shift or recovery dynamics were diverse, pre-disturbance quantification of simple factors such as structural complexity and water depth accurately predicted ecosystem trajectories. These findings foreshadow the likely divergent but predictable outcomes for reef ecosystems in response to climate change, thus guiding improved management and adaptation.

  3. Climatically driven loss of calcium in steppe soil as a sink for atmospheric carbon

    Science.gov (United States)

    A.G. Lapenis; G.B. Lawrence; S.W. Bailey; B.F. Aparin; A.I. Shiklomanov; N.A. Speranskaya; M.S. Torn; M. Calef

    2008-01-01

    During the last several thousand years the semi-arid, cold climate of the Russian steppe formed highly fertile soils rich in organic carbon and calcium (classified as Chernozems in the Russian system). Analysis of archived soil samples collected in Kemannaya Steppe Preserve in 1920, 1947, 1970, and fresh samples collected in 1998 indicated that the native steppe...

  4. Climatically driven yield variability of major crops in Khakassia (South Siberia)

    Science.gov (United States)

    Babushkina, Elena A.; Belokopytova, Liliana V.; Zhirnova, Dina F.; Shah, Santosh K.; Kostyakova, Tatiana V.

    2017-12-01

    We investigated the variability of yield of the three main crop cultures in the Khakassia Republic: spring wheat, spring barley, and oats. In terms of yield values, variability characteristics, and climatic response, the agricultural territory of Khakassia can be divided into three zones: (1) the Northern Zone, where crops yield has a high positive response to the amount of precipitation, May-July, and a moderately negative one to the temperatures of the same period; (2) the Central Zone, where crops yield depends mainly on temperatures; and (3) the Southern Zone, where climate has the least expressed impact on yield. The dominant pattern in the crops yield is caused by water stress during periods of high temperatures and low moisture supply with heat stress as additional reason. Differences between zones are due to combinations of temperature latitudinal gradient, precipitation altitudinal gradient, and the presence of a well-developed hydrological network and the irrigational system as moisture sources in the Central Zone. More detailed analysis shows differences in the climatic sensitivity of crops during phases of their vegetative growth and grain development and, to a lesser extent, during harvesting period. Multifactor linear regression models were constructed to estimate climate- and autocorrelation-induced variability of the crops yield. These models allowed prediction of the possibility of yield decreasing by at least 2-11% in the next decade due to increasing of the regional summer temperatures.

  5. Holocene climate aridification trend and human impact interrupted by millennial- and centennial-scale climate fluctuations from a new sedimentary record from Padul (Sierra Nevada, southern Iberian Peninsula)

    Science.gov (United States)

    Ramos-Román, María J.; Jiménez-Moreno, Gonzalo; Camuera, Jon; García-Alix, Antonio; Anderson, R. Scott; Jiménez-Espejo, Francisco J.; Carrión, José S.

    2018-01-01

    Holocene centennial-scale paleoenvironmental variability has been described in a multiproxy analysis (i.e., lithology, geochemistry, macrofossil, and microfossil analyses) of a paleoecological record from the Padul Basin in Sierra Nevada, southern Iberian Peninsula. This sequence covers a relevant time interval hitherto unreported in the studies of the Padul sedimentary sequence. The ˜ 4700-year record has preserved proxies of climate variability, with vegetation, lake levels, and sedimentological change during the Holocene in one of the most unique and southernmost wetlands in Europe. The progressive middle and late Holocene trend toward arid conditions identified by numerous authors in the western Mediterranean region, mostly related to a decrease in summer insolation, is also documented in this record; here it is also superimposed by centennial-scale variability in humidity. In turn, this record shows centennial-scale climate oscillations in temperature that correlate with well-known climatic events during the late Holocene in the western Mediterranean region, synchronous with variability in solar and atmospheric dynamics. The multiproxy Padul record first shows a transition from a relatively humid middle Holocene in the western Mediterranean region to more aridity from ˜ 4700 to ˜ 2800 cal yr BP. A relatively warm and humid period occurred between ˜ 2600 and ˜ 1600 cal yr BP, coinciding with persistent negative North Atlantic Oscillation (NAO) conditions and the historic Iberian-Roman Humid Period. Enhanced arid conditions, co-occurring with overall positive NAO conditions and increasing solar activity, are observed between ˜ 1550 and ˜ 450 cal yr BP (˜ 400 to ˜ 1400 CE) and colder and warmer conditions occurred during the Dark Ages and Medieval Climate Anomaly (MCA), respectively. Slightly wetter conditions took place during the end of the MCA and the first part of the Little Ice Age, which could be related to a change towards negative NAO conditions

  6. Holocene climate aridification trend and human impact interrupted by millennial- and centennial-scale climate fluctuations from a new sedimentary record from Padul (Sierra Nevada, southern Iberian Peninsula

    Directory of Open Access Journals (Sweden)

    M. J. Ramos-Román

    2018-01-01

    Full Text Available Holocene centennial-scale paleoenvironmental variability has been described in a multiproxy analysis (i.e., lithology, geochemistry, macrofossil, and microfossil analyses of a paleoecological record from the Padul Basin in Sierra Nevada, southern Iberian Peninsula. This sequence covers a relevant time interval hitherto unreported in the studies of the Padul sedimentary sequence. The  ∼  4700-year record has preserved proxies of climate variability, with vegetation, lake levels, and sedimentological change during the Holocene in one of the most unique and southernmost wetlands in Europe. The progressive middle and late Holocene trend toward arid conditions identified by numerous authors in the western Mediterranean region, mostly related to a decrease in summer insolation, is also documented in this record; here it is also superimposed by centennial-scale variability in humidity. In turn, this record shows centennial-scale climate oscillations in temperature that correlate with well-known climatic events during the late Holocene in the western Mediterranean region, synchronous with variability in solar and atmospheric dynamics. The multiproxy Padul record first shows a transition from a relatively humid middle Holocene in the western Mediterranean region to more aridity from  ∼  4700 to  ∼  2800 cal yr BP. A relatively warm and humid period occurred between  ∼  2600 and  ∼  1600 cal yr BP, coinciding with persistent negative North Atlantic Oscillation (NAO conditions and the historic Iberian–Roman Humid Period. Enhanced arid conditions, co-occurring with overall positive NAO conditions and increasing solar activity, are observed between  ∼  1550 and  ∼  450 cal yr BP (∼  400 to  ∼  1400 CE and colder and warmer conditions occurred during the Dark Ages and Medieval Climate Anomaly (MCA, respectively. Slightly wetter conditions took place during the end of

  7. Economic implications of climate-driven trends in global hydropower generation

    Science.gov (United States)

    Turner, S. W. D.; Galelli, S.; Hejazi, M. I.; Clarke, L.; Edmonds, J.; Kim, S. H.

    2017-12-01

    Recent progress in global scale hydrological and dam modeling has allowed for the study of climate change impacts on global hydropower production. Here we explore how these impacts could affect the composition of global electricity supply, and what those changes could mean for power sector emissions and investment needs in the 21st century. Regional hydropower projections are developed for two emissions scenarios by forcing a coupled global hydrological and dam model (1593 major hydropower dams; 54% global installed capacity) with downscaled, bias-corrected climate realizations derived from sixteen General Circulation Models (GCMs). To incorporate possible non-linearity in hydropower response to climate change, dam simulations incorporate plant specifications (e.g., maximum turbine flow), reservoir storage dynamics, reservoir bathymetry, evaporation losses and bespoke, site specific operations. Consequent impacts on regional and global-level electricity generation and associated emissions and investment costs are examined using the Global Change Assessment Model (GCAM). We show that changes in hydropower generation resulting from climate change can shift power demands onto and away from carbon intensive technologies, resulting in significant impacts on CO2 emissions for several regions. Many of these countries are also highly vulnerable to investment impacts (costs of new electricity generating facilities to make up for shortfalls in hydro), which in some cases amount to tens of billions of dollars by 2100. The Balkans region—typified by weak economies in a drying region that relies heavily on hydropower—emerges as the most vulnerable. Reduced impacts of climate change on hydropower production under a low emissions scenario coincide with increased costs of marginal power generating capacity (low emissions requires greater uptake of clean generating technologies, which are more expensive). This means impacts on power sector investment costs are similar for high

  8. Fire Regime and Ecosystem Effects of Climate-driven Changes in Rocky Mountains Hydrology

    Science.gov (United States)

    Westerling, A. L.; Das, T.; Lubetkin, K.; Romme, W.; Ryan, M. G.; Smithwick, E. A.; Turner, M.

    2009-12-01

    Western US Forest managers face more wildfires than ever before, and it is increasingly imperative to anticipate the consequences of this trend. Large fires in the northern Rocky Mountains have increased in association with warmer temperatures, earlier snowmelt, and longer fire seasons (1), and this trend is likely to continue with global warming (2). Increased wildfire occurrence is already a concern shared by managers from many federal land-management agencies (3). However, new analyses for the western US suggest that future climate could diverge even more rapidly from past climate than previously suggested. Current model projections suggest end-of-century hydroclimatic conditions like those of 1988 (the year of the well-known Yellowstone Fires) may represent close to the average year rather than an extreme year. The consequences of a shift of this magnitude for the fire regime, post-fire succession and carbon (C) balance of western forest ecosystems are well beyond what scientists have explored to date, and may fundamentally change the potential of western forests to sequester atmospheric C. We link hydroclimatic extremes (spring and summer temperature and cumulative water-year moisture deficit) to extreme fire years in northern Rockies forests, using large forest fire histories and 1/8-degree gridded historical hydrologic simulations (1950 - 2005) (4) forced with historical gridded temperature and precipitation (5). The frequency of extremes in hydroclimate associated with historic severe fire years in the northern Rocky Mountains is compared to those projected under a range of climate change projections, using global climate model runs for the A2 and B1 emissions pathways for three global climate models (NCAR PCM1, GFDL CM2.1, CNRM CM3). Coarse-scale climatic variables are downscaled to a 1/8 degree grid and used to force hydrologic simulations (6, 7). We will present preliminary results using these hydrologic simulations to model spatially explicit annual

  9. Solar ultraviolet radiation and ozone depletion-driven climate change: effects on terrestrial ecosystems.

    Science.gov (United States)

    Bornman, J F; Barnes, P W; Robinson, S A; Ballaré, C L; Flint, S D; Caldwell, M M

    2015-01-01

    In this assessment we summarise advances in our knowledge of how UV-B radiation (280-315 nm), together with other climate change factors, influence terrestrial organisms and ecosystems. We identify key uncertainties and knowledge gaps that limit our ability to fully evaluate the interactive effects of ozone depletion and climate change on these systems. We also evaluate the biological consequences of the way in which stratospheric ozone depletion has contributed to climate change in the Southern Hemisphere. Since the last assessment, several new findings or insights have emerged or been strengthened. These include: (1) the increasing recognition that UV-B radiation has specific regulatory roles in plant growth and development that in turn can have beneficial consequences for plant productivity via effects on plant hardiness, enhanced plant resistance to herbivores and pathogens, and improved quality of agricultural products with subsequent implications for food security; (2) UV-B radiation together with UV-A (315-400 nm) and visible (400-700 nm) radiation are significant drivers of decomposition of plant litter in globally important arid and semi-arid ecosystems, such as grasslands and deserts. This occurs through the process of photodegradation, which has implications for nutrient cycling and carbon storage, although considerable uncertainty exists in quantifying its regional and global biogeochemical significance; (3) UV radiation can contribute to climate change via its stimulation of volatile organic compounds from plants, plant litter and soils, although the magnitude, rates and spatial patterns of these emissions remain highly uncertain at present. UV-induced release of carbon from plant litter and soils may also contribute to global warming; and (4) depletion of ozone in the Southern Hemisphere modifies climate directly via effects on seasonal weather patterns (precipitation and wind) and these in turn have been linked to changes in the growth of plants

  10. Causes and projections of abrupt climate-driven ecosystem shifts in the North Atlantic

    DEFF Research Database (Denmark)

    Beaugrand, G.; Edwards, M.; Brander, Keith

    2008-01-01

    Warming of the global climate is now unequivocal and its impact on Earth' functional units has become more apparent. Here, we show that marine ecosystems are not equally sensitive to climate change and reveal a critical thermal boundary where a small increase in temperature triggers abrupt...... ecosystem shifts seen across multiple trophic levels. This large-scale boundary is located in regions where abrupt ecosystem shifts have been reported in the North Atlantic sector and thereby allows us to link these shifts by a global common phenomenon. We show that these changes alter the biodiversity...... and carrying capacity of ecosystems and may, combined with fishing, precipitate the reduction of some stocks of Atlantic cod already severely impacted by exploitation. These findings offer a way to anticipate major ecosystem changes and to propose adaptive strategies for marine exploited resources such as cod...

  11. Climate-driven range shifts of the king penguin in a fragmented ecosystem

    Science.gov (United States)

    Cristofari, Robin; Liu, Xiaoming; Bonadonna, Francesco; Cherel, Yves; Pistorius, Pierre; Le Maho, Yvon; Raybaud, Virginie; Stenseth, Nils Christian; Le Bohec, Céline; Trucchi, Emiliano

    2018-03-01

    Range shift is the primary short-term species response to rapid climate change, but it is often hampered by natural or anthropogenic habitat fragmentation. Different critical areas of a species' niche may be exposed to heterogeneous environmental changes and modelling species response under such complex spatial and ecological scenarios presents well-known challenges. Here, we use a biophysical ecological niche model validated through population genomics and palaeodemography to reconstruct past range shifts and identify future vulnerable areas and potential refugia of the king penguin in the Southern Ocean. Integrating genomic and demographic data at the whole-species level with specific biophysical constraints, we present a refined framework for predicting the effect of climate change on species relying on spatially and ecologically distinct areas to complete their life cycle (for example, migratory animals, marine pelagic organisms and central-place foragers) and, in general, on species living in fragmented ecosystems.

  12. Climate-driven extinctions shape the phylogenetic structure of temperate tree floras.

    Science.gov (United States)

    Eiserhardt, Wolf L; Borchsenius, Finn; Plum, Christoffer M; Ordonez, Alejandro; Svenning, Jens-Christian

    2015-03-01

    When taxa go extinct, unique evolutionary history is lost. If extinction is selective, and the intrinsic vulnerabilities of taxa show phylogenetic signal, more evolutionary history may be lost than expected under random extinction. Under what conditions this occurs is insufficiently known. We show that late Cenozoic climate change induced phylogenetically selective regional extinction of northern temperate trees because of phylogenetic signal in cold tolerance, leading to significantly and substantially larger than random losses of phylogenetic diversity (PD). The surviving floras in regions that experienced stronger extinction are phylogenetically more clustered, indicating that non-random losses of PD are of increasing concern with increasing extinction severity. Using simulations, we show that a simple threshold model of survival given a physiological trait with phylogenetic signal reproduces our findings. Our results send a strong warning that we may expect future assemblages to be phylogenetically and possibly functionally depauperate if anthropogenic climate change affects taxa similarly. © 2015 John Wiley & Sons Ltd/CNRS.

  13. Contribution of physical modelling to climate-driven landslide hazard mapping: an alpine test site

    Science.gov (United States)

    Vandromme, R.; Desramaut, N.; Baills, A.; Hohmann, A.; Grandjean, G.; Sedan, O.; Mallet, J. P.

    2012-04-01

    The aim of this work is to develop a methodology for integrating climate change scenarios into quantitative hazard assessment and especially their precipitation component. The effects of climate change will be different depending on both the location of the site and the type of landslide considered. Indeed, mass movements can be triggered by different factors. This paper describes a methodology to address this issue and shows an application on an alpine test site. Mechanical approaches represent a solution for quantitative landslide susceptibility and hazard modeling. However, as the quantity and the quality of data are generally very heterogeneous at a regional scale, it is necessary to take into account the uncertainty in the analysis. In this perspective, a new hazard modeling method is developed and integrated in a program named ALICE. This program integrates mechanical stability analysis through a GIS software taking into account data uncertainty. This method proposes a quantitative classification of landslide hazard and offers a useful tool to gain time and efficiency in hazard mapping. However, an expertise approach is still necessary to finalize the maps. Indeed it is the only way to take into account some influent factors in slope stability such as heterogeneity of the geological formations or effects of anthropic interventions. To go further, the alpine test site (Barcelonnette area, France) is being used to integrate climate change scenarios into ALICE program, and especially their precipitation component with the help of a hydrological model (GARDENIA) and the regional climate model REMO (Jacob, 2001). From a DEM, land-cover map, geology, geotechnical data and so forth the program classifies hazard zones depending on geotechnics and different hydrological contexts varying in time. This communication, realized within the framework of Safeland project, is supported by the European Commission under the 7th Framework Programme for Research and Technological

  14. Large Ensemble Analytic Framework for Consequence-Driven Discovery of Climate Change Scenarios

    Science.gov (United States)

    Lamontagne, Jonathan R.; Reed, Patrick M.; Link, Robert; Calvin, Katherine V.; Clarke, Leon E.; Edmonds, James A.

    2018-03-01

    An analytic scenario generation framework is developed based on the idea that the same climate outcome can result from very different socioeconomic and policy drivers. The framework builds on the Scenario Matrix Framework's abstraction of "challenges to mitigation" and "challenges to adaptation" to facilitate the flexible discovery of diverse and consequential scenarios. We combine visual and statistical techniques for interrogating a large factorial data set of 33,750 scenarios generated using the Global Change Assessment Model. We demonstrate how the analytic framework can aid in identifying which scenario assumptions are most tied to user-specified measures for policy relevant outcomes of interest, specifically for our example high or low mitigation costs. We show that the current approach for selecting reference scenarios can miss policy relevant scenario narratives that often emerge as hybrids of optimistic and pessimistic scenario assumptions. We also show that the same scenario assumption can be associated with both high and low mitigation costs depending on the climate outcome of interest and the mitigation policy context. In the illustrative example, we show how agricultural productivity, population growth, and economic growth are most predictive of the level of mitigation costs. Formulating policy relevant scenarios of deeply and broadly uncertain futures benefits from large ensemble-based exploration of quantitative measures of consequences. To this end, we have contributed a large database of climate change futures that can support "bottom-up" scenario generation techniques that capture a broader array of consequences than those that emerge from limited sampling of a few reference scenarios.

  15. Climate-driven endemic cholera is modulated by human mobility in a megacity

    Science.gov (United States)

    Perez-Saez, Javier; King, Aaron A.; Rinaldo, Andrea; Yunus, Mohammad; Faruque, Abu S. G.; Pascual, Mercedes

    2017-10-01

    Although a differential sensitivity of cholera dynamics to climate variability has been reported in the spatially heterogeneous megacity of Dhaka, Bangladesh, the specific patterns of spread of the resulting risk within the city remain unclear. We build on an established probabilistic spatial model to investigate the importance and role of human mobility in modulating spatial cholera transmission. Mobility fluxes were inferred using a straightforward and generalizable methodology that relies on mapping population density based on a high resolution urban footprint product, and a parameter-free human mobility model. In accordance with previous findings, we highlight the higher sensitivity to the El Niño Southern Oscillation (ENSO) in the highly populated urban center than in the more rural periphery. More significantly, our results show that cholera risk is largely transmitted from the climate-sensitive core to the periphery of the city, with implications for the planning of control efforts. In addition, including human mobility improves the outbreak prediction performance of the model with an 11 month lead. The interplay between climatic and human mobility factors in cholera transmission is discussed from the perspective of the rapid growth of megacities across the developing world.

  16. Analysis of changes in crop farming in the Dudh Koshi (Nepal) driven by climate changes

    Science.gov (United States)

    Gianinetto, Marco; Polinelli, Francesco; Frassy, Federico; Aiello, Martina; Rota Nodari, Francesco; Soncini, Andrea; Bocchiola, Daniele

    2017-10-01

    Nepal is one of the poorest nations of the world and the Koshi Basin includes some of the poorest regions of this country. It's farming system is subsistence agriculture, mainly rainfed, with crop productivity among the lowest in South Asia. Nepal is also severely impacted by climate changes, such as retreat of glaciers, rise in temperature, erratic rainfalls and increase in frequency of extreme weather. This paper describes the spatio-temporal evolution of cultivated land in Dudh Koshi during the last four decades (1970s-2010s), by mapping the farming of its four main cereals in the districts of Solukhumbu, Okhaldunga and Kothang from space. The analysis of satellite time series showed a 10% of increment in farmland from 1970s to 1990s, and about 60% in the following twenty years. With a shift of cropping to higher altitudes. Data belonging to of the second twenty years are strongly correlated with the population growth observed in the same period (0.97demographic and socioeconomic pressures are driving the expansion, while climatic and topographic parameters are just channeling the expansion. Apart from any policies that could change the tack, Dudh Koshi should be able to meet the increasing demand of cereals in the near future and climate seems not being a limiting factor for further development as it will be the availability of an irrigation system.

  17. Climate-driven speedup of alpine treeline forest growth in the Tianshan Mountains, Northwestern China.

    Science.gov (United States)

    Qi, Zhaohuan; Liu, Hongyan; Wu, Xiuchen; Hao, Qian

    2015-02-01

    Forest growth is sensitive to interannual climatic change in the alpine treeline ecotone (ATE). Whether the alpine treeline ecotone shares a similar pattern of forest growth with lower elevational closed forest belt (CFB) under changing climate remains unclear. Here, we reported an unprecedented acceleration of Picea schrenkiana forest growth since 1960s in the ATE of Tianshan Mountains, northwestern China by a stand-total sampling along six altitudinal transects with three plots in each transect: one from the ATE between the treeline and the forest line, and the other two from the CFB. All the sampled P. schrenkiana forest patches show a higher growth speed after 1960 and, comparatively, forest growth in the CFB has sped up much slower than that in the ATE. The speedup of forest growth at the ATE is mainly accounted for by climate factors, with increasing temperature suggested to be the primary driver. Stronger water deficit as well as more competition within the CFB might have restricted forest growth there more than that within the ATE, implying biotic factors were also significant for the accelerated forest growth in the ATE, which should be excluded from simulations and predictions of warming-induced treeline dynamics. © 2014 John Wiley & Sons Ltd.

  18. Monitoring strategies of stream phosphorus under contrasting climate-driven flow regimes

    DEFF Research Database (Denmark)

    Goyenola, Guillermo; Meerhoff, Marianna; Teixeira-de Mello, Franco

    2015-01-01

    Climate and hydrology are relevant control factors determining the timing and amount of nutrient losses from land to downstream aquatic systems, in particular of phosphorus (P) from agricultural lands. The main objective of the study was to evaluate the differences in P export patterns and the pe......Climate and hydrology are relevant control factors determining the timing and amount of nutrient losses from land to downstream aquatic systems, in particular of phosphorus (P) from agricultural lands. The main objective of the study was to evaluate the differences in P export patterns...... applied two alternative nutrient sampling programs (high-frequency composite sampling and low-frequency instantaneous-grab sampling) and estimated the contribution derived from point and diffuse sources fitting a source apportionment model. We expected to detect a pattern of higher total and particulate...... program to estimate P exports in flashy streams compared to the less variable streams. We also found signs of interaction between climate/hydrology and land use intensity, in particular in the presence of point sources of P, leading to a bias towards underestimation of P in hydrologically stable streams...

  19. Free boundary models for mosquito range movement driven by climate warming.

    Science.gov (United States)

    Bao, Wendi; Du, Yihong; Lin, Zhigui; Zhu, Huaiping

    2018-03-01

    As vectors, mosquitoes transmit numerous mosquito-borne diseases. Among the many factors affecting the distribution and density of mosquitoes, climate change and warming have been increasingly recognized as major ones. In this paper, we make use of three diffusive logistic models with free boundary in one space dimension to explore the impact of climate warming on the movement of mosquito range. First, a general model incorporating temperature change with location and time is introduced. In order to gain insights of the model, a simplified version of the model with the change of temperature depending only on location is analyzed theoretically, for which the dynamical behavior is completely determined and presented. The general model can be modified into a more realistic one of seasonal succession type, to take into account of the seasonal changes of mosquito movements during each year, where the general model applies only for the time period of the warm seasons of the year, and during the cold season, the mosquito range is fixed and the population is assumed to be in a hibernating status. For both the general model and the seasonal succession model, our numerical simulations indicate that the long-time dynamical behavior is qualitatively similar to the simplified model, and the effect of climate warming on the movement of mosquitoes can be easily captured. Moreover, our analysis reveals that hibernating enhances the chances of survival and successful spreading of the mosquitoes, but it slows down the spreading speed.

  20. Managing consequences of climate-driven species redistribution requires integration of ecology, conservation and social science.

    Science.gov (United States)

    Bonebrake, Timothy C; Brown, Christopher J; Bell, Johann D; Blanchard, Julia L; Chauvenet, Alienor; Champion, Curtis; Chen, I-Ching; Clark, Timothy D; Colwell, Robert K; Danielsen, Finn; Dell, Anthony I; Donelson, Jennifer M; Evengård, Birgitta; Ferrier, Simon; Frusher, Stewart; Garcia, Raquel A; Griffis, Roger B; Hobday, Alistair J; Jarzyna, Marta A; Lee, Emma; Lenoir, Jonathan; Linnetved, Hlif; Martin, Victoria Y; McCormack, Phillipa C; McDonald, Jan; McDonald-Madden, Eve; Mitchell, Nicola; Mustonen, Tero; Pandolfi, John M; Pettorelli, Nathalie; Possingham, Hugh; Pulsifer, Peter; Reynolds, Mark; Scheffers, Brett R; Sorte, Cascade J B; Strugnell, Jan M; Tuanmu, Mao-Ning; Twiname, Samantha; Vergés, Adriana; Villanueva, Cecilia; Wapstra, Erik; Wernberg, Thomas; Pecl, Gretta T

    2018-02-01

    Climate change is driving a pervasive global redistribution of the planet's species. Species redistribution poses new questions for the study of ecosystems, conservation science and human societies that require a coordinated and integrated approach. Here we review recent progress, key gaps and strategic directions in this nascent research area, emphasising emerging themes in species redistribution biology, the importance of understanding underlying drivers and the need to anticipate novel outcomes of changes in species ranges. We highlight that species redistribution has manifest implications across multiple temporal and spatial scales and from genes to ecosystems. Understanding range shifts from ecological, physiological, genetic and biogeographical perspectives is essential for informing changing paradigms in conservation science and for designing conservation strategies that incorporate changing population connectivity and advance adaptation to climate change. Species redistributions present challenges for human well-being, environmental management and sustainable development. By synthesising recent approaches, theories and tools, our review establishes an interdisciplinary foundation for the development of future research on species redistribution. Specifically, we demonstrate how ecological, conservation and social research on species redistribution can best be achieved by working across disciplinary boundaries to develop and implement solutions to climate change challenges. Future studies should therefore integrate existing and complementary scientific frameworks while incorporating social science and human-centred approaches. Finally, we emphasise that the best science will not be useful unless more scientists engage with managers, policy makers and the public to develop responsible and socially acceptable options for the global challenges arising from species redistributions. © 2017 Cambridge Philosophical Society.

  1. Climate-driven effects of fire on winter habitat for caribou in the Alaskan-Yukon Arctic

    Science.gov (United States)

    Gustine, David D.; Brinkman, Todd J.; Lindgren, Michael A.; Schmidt, Jennifer I.; Rupp, T. Scott; Adams, Layne G.

    2014-01-01

    Climatic warming has direct implications for fire-dominated disturbance patterns in northern ecosystems. A transforming wildfire regime is altering plant composition and successional patterns, thus affecting the distribution and potentially the abundance of large herbivores. Caribou (Rangifer tarandus) are an important subsistence resource for communities throughout the north and a species that depends on terrestrial lichen in late-successional forests and tundra systems. Projected increases in area burned and reductions in stand ages may reduce lichen availability within caribou winter ranges. Sufficient reductions in lichen abundance could alter the capacity of these areas to support caribou populations. To assess the potential role of a changing fire regime on winter habitat for caribou, we used a simulation modeling platform, two global circulation models (GCMs), and a moderate emissions scenario to project annual fire characteristics and the resulting abundance of lichen-producing vegetation types (i.e., spruce forests and tundra >60 years old) across a modeling domain that encompassed the winter ranges of the Central Arctic and Porcupine caribou herds in the Alaskan-Yukon Arctic. Fires were less numerous and smaller in tundra compared to spruce habitats throughout the 90-year projection for both GCMs. Given the more likely climate trajectory, we projected that the Porcupine caribou herd, which winters primarily in the boreal forest, could be expected to experience a greater reduction in lichen-producing winter habitats (−21%) than the Central Arctic herd that wintered primarily in the arctic tundra (−11%). Our results suggest that caribou herds wintering in boreal forest will undergo fire-driven reductions in lichen-producing habitats that will, at a minimum, alter their distribution. Range shifts of caribou resulting from fire-driven changes to winter habitat may diminish access to caribou for rural communities that reside in fire-prone areas.

  2. Climate-driven effects of fire on winter habitat for caribou in the Alaskan-Yukon Arctic.

    Directory of Open Access Journals (Sweden)

    David D Gustine

    Full Text Available Climatic warming has direct implications for fire-dominated disturbance patterns in northern ecosystems. A transforming wildfire regime is altering plant composition and successional patterns, thus affecting the distribution and potentially the abundance of large herbivores. Caribou (Rangifer tarandus are an important subsistence resource for communities throughout the north and a species that depends on terrestrial lichen in late-successional forests and tundra systems. Projected increases in area burned and reductions in stand ages may reduce lichen availability within caribou winter ranges. Sufficient reductions in lichen abundance could alter the capacity of these areas to support caribou populations. To assess the potential role of a changing fire regime on winter habitat for caribou, we used a simulation modeling platform, two global circulation models (GCMs, and a moderate emissions scenario to project annual fire characteristics and the resulting abundance of lichen-producing vegetation types (i.e., spruce forests and tundra >60 years old across a modeling domain that encompassed the winter ranges of the Central Arctic and Porcupine caribou herds in the Alaskan-Yukon Arctic. Fires were less numerous and smaller in tundra compared to spruce habitats throughout the 90-year projection for both GCMs. Given the more likely climate trajectory, we projected that the Porcupine caribou herd, which winters primarily in the boreal forest, could be expected to experience a greater reduction in lichen-producing winter habitats (-21% than the Central Arctic herd that wintered primarily in the arctic tundra (-11%. Our results suggest that caribou herds wintering in boreal forest will undergo fire-driven reductions in lichen-producing habitats that will, at a minimum, alter their distribution. Range shifts of caribou resulting from fire-driven changes to winter habitat may diminish access to caribou for rural communities that reside in fire-prone areas.

  3. Climate-driven effects of fire on winter habitat for caribou in the Alaskan-Yukon Arctic.

    Science.gov (United States)

    Gustine, David D; Brinkman, Todd J; Lindgren, Michael A; Schmidt, Jennifer I; Rupp, T Scott; Adams, Layne G

    2014-01-01

    Climatic warming has direct implications for fire-dominated disturbance patterns in northern ecosystems. A transforming wildfire regime is altering plant composition and successional patterns, thus affecting the distribution and potentially the abundance of large herbivores. Caribou (Rangifer tarandus) are an important subsistence resource for communities throughout the north and a species that depends on terrestrial lichen in late-successional forests and tundra systems. Projected increases in area burned and reductions in stand ages may reduce lichen availability within caribou winter ranges. Sufficient reductions in lichen abundance could alter the capacity of these areas to support caribou populations. To assess the potential role of a changing fire regime on winter habitat for caribou, we used a simulation modeling platform, two global circulation models (GCMs), and a moderate emissions scenario to project annual fire characteristics and the resulting abundance of lichen-producing vegetation types (i.e., spruce forests and tundra >60 years old) across a modeling domain that encompassed the winter ranges of the Central Arctic and Porcupine caribou herds in the Alaskan-Yukon Arctic. Fires were less numerous and smaller in tundra compared to spruce habitats throughout the 90-year projection for both GCMs. Given the more likely climate trajectory, we projected that the Porcupine caribou herd, which winters primarily in the boreal forest, could be expected to experience a greater reduction in lichen-producing winter habitats (-21%) than the Central Arctic herd that wintered primarily in the arctic tundra (-11%). Our results suggest that caribou herds wintering in boreal forest will undergo fire-driven reductions in lichen-producing habitats that will, at a minimum, alter their distribution. Range shifts of caribou resulting from fire-driven changes to winter habitat may diminish access to caribou for rural communities that reside in fire-prone areas.

  4. Advancing the climate data driven crop-modeling studies in the dry areas of Northern Syria and Lebanon: An important first step for assessing impact of future climate

    Energy Technology Data Exchange (ETDEWEB)

    Dixit, Prakash N., E-mail: p.dixit@cgiar.org; Telleria, Roberto

    2015-04-01

    Inter-annual and seasonal variability in climatic parameters, most importantly rainfall, have potential to cause climate-induced risk in long-term crop production. Short-term field studies do not capture the full nature of such risk and the extent to which modifications to crop, soil and water management recommendations may be made to mitigate the extent of such risk. Crop modeling studies driven by long-term daily weather data can predict the impact of climate-induced risk on crop growth and yield however, the availability of long-term daily weather data can present serious constraints to the use of crop models. To tackle this constraint, two weather generators namely, LARS-WG and MarkSim, were evaluated in order to assess their capabilities of reproducing frequency distributions, means, variances, dry spell and wet chains of observed daily precipitation, maximum and minimum temperature, and solar radiation for the eight locations across cropping areas of Northern Syria and Lebanon. Further, the application of generated long-term daily weather data, with both weather generators, in simulating barley growth and yield was also evaluated. We found that overall LARS-WG performed better than MarkSim in generating daily weather parameters and in 50 years continuous simulation of barley growth and yield. Our findings suggest that LARS-WG does not necessarily require long-term e.g., > 30 years observed weather data for calibration as generated results proved to be satisfactory with > 10 years of observed data except in area with higher altitude. Evaluating these weather generators and the ability of generated weather data to perform long-term simulation of crop growth and yield is an important first step to assess the impact of future climate on yields, and to identify promising technologies to make agricultural systems more resilient in the given region. - Highlights: • LARS-WG performed better than MarkSim in generating daily weather parameters. • LARS-WG can serve

  5. Advancing the climate data driven crop-modeling studies in the dry areas of Northern Syria and Lebanon: An important first step for assessing impact of future climate

    International Nuclear Information System (INIS)

    Dixit, Prakash N.; Telleria, Roberto

    2015-01-01

    Inter-annual and seasonal variability in climatic parameters, most importantly rainfall, have potential to cause climate-induced risk in long-term crop production. Short-term field studies do not capture the full nature of such risk and the extent to which modifications to crop, soil and water management recommendations may be made to mitigate the extent of such risk. Crop modeling studies driven by long-term daily weather data can predict the impact of climate-induced risk on crop growth and yield however, the availability of long-term daily weather data can present serious constraints to the use of crop models. To tackle this constraint, two weather generators namely, LARS-WG and MarkSim, were evaluated in order to assess their capabilities of reproducing frequency distributions, means, variances, dry spell and wet chains of observed daily precipitation, maximum and minimum temperature, and solar radiation for the eight locations across cropping areas of Northern Syria and Lebanon. Further, the application of generated long-term daily weather data, with both weather generators, in simulating barley growth and yield was also evaluated. We found that overall LARS-WG performed better than MarkSim in generating daily weather parameters and in 50 years continuous simulation of barley growth and yield. Our findings suggest that LARS-WG does not necessarily require long-term e.g., > 30 years observed weather data for calibration as generated results proved to be satisfactory with > 10 years of observed data except in area with higher altitude. Evaluating these weather generators and the ability of generated weather data to perform long-term simulation of crop growth and yield is an important first step to assess the impact of future climate on yields, and to identify promising technologies to make agricultural systems more resilient in the given region. - Highlights: • LARS-WG performed better than MarkSim in generating daily weather parameters. • LARS-WG can serve

  6. Towards a climate-driven dengue decision support system for Thailand

    Science.gov (United States)

    Lowe, Rachel; Cazelles, Bernard; Paul, Richard; Rodó, Xavier

    2014-05-01

    Dengue is a peri-urban mosquito-transmitted disease, ubiquitous in the tropics and the subtropics. The geographic distribution of dengue and its more severe form, dengue haemorrhagic fever (DHF), have expanded dramatically in the last decades and dengue is now considered to be the world's most important arboviral disease. Recent demographic changes have greatly contributed to the acceleration and spread of the disease along with uncontrolled urbanization, population growth and increased air travel, which acts as a mechanism for transporting and exchanging dengue viruses between endemic and epidemic populations. The dengue vector and virus are extremely sensitive to environmental conditions such as temperature, humidity and precipitation that influence mosquito biology, abundance and habitat and the virus replication speed. In order to control the spread of dengue and impede epidemics, decision support systems are required that take into account the multi-faceted array of factors that contribute to increased dengue risk. Due to availability of seasonal climate forecasts, that predict the average climate conditions for forthcoming months/seasons in both time and space, there is an opportunity to incorporate precursory climate information in a dengue decision support system to aid epidemic planning months in advance. Furthermore, oceanic indicators from teleconnected areas in the Pacific and Indian Ocean, that can provide some indication of the likely prevailing climate conditions in certain regions, could potentially extend predictive lead time in a dengue early warning system. In this paper we adopt a spatio-temporal Bayesian modelling framework for dengue in Thailand to support public health decision making. Monthly cases of dengue in the 76 provinces of Thailand for the period 1982-2012 are modelled using a multi-layered approach. Environmental explanatory variables at various spatial and temporal resolutions are incorporated into a hierarchical model in order to

  7. Relative Contributions of Mean-State Shifts and ENSO-Driven Variability to Precipitation Changes in a Warming Climate*

    Energy Technology Data Exchange (ETDEWEB)

    Bonfils, Céline J. W.; Santer, Benjamin D.; Phillips, Thomas J.; Marvel, Kate; Leung, L. Ruby; Doutriaux, Charles; Capotondi, Antonietta

    2015-12-01

    The El Niño-Southern Oscillation (ENSO) is an important driver of regional hydroclimate variability through far-reaching teleconnections. Most climate models project an increase in the frequency of extreme El Niño events under increased greenhouse-gas (GHG) forcing. However, it is unclear how other aspects of ENSO and ENSO-driven teleconnections will evolve in the future. Here, we identify in 20th century sea-surface temperature (SST) observations a time-invariant ENSO-like (ENSOL) pattern that is largely uncontaminated by GHG forcing. We use this pattern to investigate the future precipitation (P) response to ENSO-like SST anomalies. Models that better capture observed ENSOL characteristics produce P teleconnection patterns that are in better accord with observations and more stationary in the 21st century. We decompose the future P response to ENSOL into the sum of three terms: (1) the change in P mean state, (2) the historical P response to ENSOL, and (3) a future enhancement in the P response to ENSOL. In many regions, this last term can aggravate the P extremes associated with ENSO variability. This simple decomposition allows us to identify regions likely to experience ENSOL-induced P changes that are without precedent in the current climate.

  8. Variations in Modeled Dengue Transmission over Puerto Rico Using a Climate Driven Dynamic Model

    Science.gov (United States)

    Morin, Cory; Monaghan, Andrew; Crosson, William; Quattrochi, Dale; Luvall, Jeffrey

    2014-01-01

    Dengue fever is a mosquito-borne viral disease reemerging throughout much of the tropical Americas. Dengue virus transmission is explicitly influenced by climate and the environment through its primary vector, Aedes aegypti. Temperature regulates Ae. aegypti development, survival, and replication rates as well as the incubation period of the virus within the mosquito. Precipitation provides water for many of the preferred breeding habitats of the mosquito, including buckets, old tires, and other places water can collect. Because of variations in topography, ocean influences and atmospheric processes, temperature and rainfall patterns vary across Puerto Rico and so do dengue virus transmission rates. Using NASA's TRMM (Tropical Rainfall Measuring Mission) satellite for precipitation input, ground-based observations for temperature input, and laboratory confirmed dengue cases reported by the Centers for Disease Control and Prevention for parameter calibration, we modeled dengue transmission at the county level across Puerto Rico from 2010-2013 using a dynamic dengue transmission model that includes interacting vector ecology and epidemiological components. Employing a Monte Carlo approach, we performed ensembles of several thousands of model simulations for each county in order to resolve the model uncertainty arising from using different combinations of parameter values that are not well known. The top 1% of model simulations that best reproduced the reported dengue case data were then analyzed to determine the most important parameters for dengue virus transmission in each county, as well as the relative influence of climate variability on transmission. These results can be used by public health workers to implement dengue control methods that are targeted for specific locations and climate conditions.

  9. Evaluation of the effects of ENSO teleconnection on climatic parameters fluctuations in Khorasan Province I.R. of Iran

    International Nuclear Information System (INIS)

    Ehteramian, Kourosh; Shahabfar, Alireza; Gharaei, Sohrab M.; Jamali, Javad B.

    2004-01-01

    The long term forecasting and monitoring of climatological parameters depends on identification of all effective factors, which are affects on this phenomena. One of these parameters is the weather signal. These signals are determinable and specific pattern and occurs in the distinguished regions in the world, but it's effects are world wide. One of the famous signals is ENSO phenomenon, which have two phases. In this paper with using annual and seasonal correlations between southern oscillation index (SOI) and precipitation and temperature data the effective amounts of ENSO phases on the differences of these factors was studied in the all regions of Khorasan province in Iran, then for more comprehensive study the classification maps in relation of ENSO and variability of precipitation and temperature were drown. It was concluded that the mentioned parameters in the whole of the province especially in central and north strip have shown significant action to ENSO, in other word the average of precipitation and temperature correlation indices are negative annually and seasonally, it means when SOI amounts are increased the precipitation and temperature in Khorasan will be decreased. With regard to increasing the above weather parameters in all regions of Khorasan at the time of ENSO negative phases (El Nino condition) variations of precipitation and temperature could be related to the changes of the pattern of occurrence this phenomenon (ENSO) due to climatic change around the world. (Author)

  10. Seasonal fluctuations of airborne pollen grains count and its correlation with climatic factors from khairpur; sindh, pakistan

    International Nuclear Information System (INIS)

    Perveen, A.; Khan, M.

    2014-01-01

    This is the first aerobiological survey of Khairpur, Sindh. The survey was conducted from January-December, 2011 using Burkard's Seven Days Volumetric Spore trap. A total of 4559 pollen/m3 were recorded belonging to 33 plant families and 41 pollen types. The major pollen types were Poaceae (13.84%), Amaranthaceae/ Chenopodiaceae (10.40%), Cyperus rotundus (7.61%); Prosopis juliflora (6.19%), Brassica campestris (4.91%), Typha angustifolia (4.89%), Tamarix indica (4.43%), Eucalyptus globules (4.28%), Conocarpus erectus (3.73%), Asteraceae (3.01%), Guaicum officinale (2.94%), Azadirachta indica (2.74%), Malvaceae (2.15%) and Phoenix dactylifera (1.84%) constituting more than 70% of total pollen catch. The highest pollen grains concentration was observed in May-2011 with 880 pollen/m3 count while second highest pollen concentration was detected in September 2011 with 682 pollen/m3. The lowest count was found in December- 2011. Climatic factors like wind speed, average temperature, humidity and rainfall were correlated with the pollen counts. Different pollen types showed significant positive correlation with average temperature while negative correlation with humidity and wind speed. (author)

  11. Coupled European and Greenland last glacial dust activity driven by North Atlantic climate

    DEFF Research Database (Denmark)

    Újvári, Gábor; Stevens, Thomas; Molnár, Mihály

    2017-01-01

    Centennial-scale mineral dust peaks in last glacial Greenland ice cores match the timing of lowest Greenland temperatures, yet little is known of equivalent changes in dust-emitting regions, limiting our understanding of dust−climate interaction. Here, we present the most detailed and precise age...... model for European loess dust deposits to date, based on 125 accelerator mass spectrometry14C ages from Dunaszekcso, } Hungary. The record shows that variations in glacial dust deposition variability on centennial–millennial timescales in east central Europe and Greenland were synchronous within...

  12. Human population growth offsets climate-driven increase in woody vegetation in sub-Saharan Africa

    DEFF Research Database (Denmark)

    Brandt, Martin Stefan; Rasmussen, Kjeld; Peñuelas, Josep

    2017-01-01

    The rapidly growing human population in sub-Saharan Africa generates increasing demand for agricultural land and forest products, which presumably leads to deforestation. Conversely, a greening of African drylands has been reported, but this has been difficult to associate with changes in woody...... an increase in woody cover largely in drylands, and 11% had a decrease (2,150,000 km2), mostly in humid zones. Increases in woody cover were associated with low population growth, and were driven by increases in CO2 in the humid zones and by increases in precipitation in drylands, whereas decreases in woody...... cover were associated with high population growth. The spatially distinct pattern of these opposing trends reflects, first, the natural response of vegetation to precipitation and atmospheric CO2, and second, deforestation in humid areas, minor in size but important for ecosystem services...

  13. Evaluating the Performance of a Climate-Driven Mortality Model during Heat Waves and Cold Spells in Europe

    Science.gov (United States)

    Lowe, Rachel; Ballester, Joan; Creswick, James; Robine, Jean-Marie; Herrmann, François R.; Rodó, Xavier

    2015-01-01

    The impact of climate change on human health is a serious concern. In particular, changes in the frequency and intensity of heat waves and cold spells are of high relevance in terms of mortality and morbidity. This demonstrates the urgent need for reliable early-warning systems to help authorities prepare and respond to emergency situations. In this study, we evaluate the performance of a climate-driven mortality model to provide probabilistic predictions of exceeding emergency mortality thresholds for heat wave and cold spell scenarios. Daily mortality data corresponding to 187 NUTS2 regions across 16 countries in Europe were obtained from 1998–2003. Data were aggregated to 54 larger regions in Europe, defined according to similarities in population structure and climate. Location-specific average mortality rates, at given temperature intervals over the time period, were modelled to account for the increased mortality observed during both high and low temperature extremes and differing comfort temperatures between regions. Model parameters were estimated in a Bayesian framework, in order to generate probabilistic simulations of mortality across Europe for time periods of interest. For the heat wave scenario (1–15 August 2003), the model was successfully able to anticipate the occurrence or non-occurrence of mortality rates exceeding the emergency threshold (75th percentile of the mortality distribution) for 89% of the 54 regions, given a probability decision threshold of 70%. For the cold spell scenario (1–15 January 2003), mortality events in 69% of the regions were correctly anticipated with a probability decision threshold of 70%. By using a more conservative decision threshold of 30%, this proportion increased to 87%. Overall, the model performed better for the heat wave scenario. By replacing observed temperature data in the model with forecast temperature, from state-of-the-art European forecasting systems, probabilistic mortality predictions could

  14. Evaluating the Performance of a Climate-Driven Mortality Model during Heat Waves and Cold Spells in Europe

    Directory of Open Access Journals (Sweden)

    Rachel Lowe

    2015-01-01

    Full Text Available The impact of climate change on human health is a serious concern. In particular, changes in the frequency and intensity of heat waves and cold spells are of high relevance in terms of mortality and morbidity. This demonstrates the urgent need for reliable early-warning systems to help authorities prepare and respond to emergency situations. In this study, we evaluate the performance of a climate-driven mortality model to provide probabilistic predictions of exceeding emergency mortality thresholds for heat wave and cold spell scenarios. Daily mortality data corresponding to 187 NUTS2 regions across 16 countries in Europe were obtained from 1998–2003. Data were aggregated to 54 larger regions in Europe, defined according to similarities in population structure and climate. Location-specific average mortality rates, at given temperature intervals over the time period, were modelled to account for the increased mortality observed during both high and low temperature extremes and differing comfort temperatures between regions. Model parameters were estimated in a Bayesian framework, in order to generate probabilistic simulations of mortality across Europe for time periods of interest. For the heat wave scenario (1–15 August 2003, the model was successfully able to anticipate the occurrence or non-occurrence of mortality rates exceeding the emergency threshold (75th percentile of the mortality distribution for 89% of the 54 regions, given a probability decision threshold of 70%. For the cold spell scenario (1–15 January 2003, mortality events in 69% of the regions were correctly anticipated with a probability decision threshold of 70%. By using a more conservative decision threshold of 30%, this proportion increased to 87%. Overall, the model performed better for the heat wave scenario. By replacing observed temperature data in the model with forecast temperature, from state-of-the-art European forecasting systems, probabilistic mortality

  15. Whitebark pine vulnerability to climate-driven mountain pine beetle disturbance in the Greater Yellowstone Ecosystem.

    Science.gov (United States)

    Logan, Jesse A; MacFarlane, William W; Willcox, Louisa

    2010-06-01

    Widespread outbreaks of mountain pine beetles (MPB) are occurring throughout the range of this native insect. Episodic outbreaks are a common occurrence in the beetles' primary host, lodgepole pine. Current outbreaks, however, are occurring in habitats where outbreaks either did not previously occur or were limited in scale. Herein, we address widespread, ongoing outbreaks in high-elevation, whitebark pine forests of the Greater Yellowstone Ecosystem, where, due to an inhospitable climate, past outbreaks were infrequent and short lived. We address the basic question: are these outbreaks truly unprecedented and a threat to ecosystem continuity? In order to evaluate this question we (1) present evidence that the current outbreak is outside the historic range of variability; (2) examine system resiliency to MPB disturbance based on adaptation to disturbance and host defenses to MPB attack; and (3) investigate the potential domain of attraction to large-scale MPB disturbance based on thermal developmental thresholds, spatial structure of forest types, and the confounding influence of an introduced pathogen. We conclude that the loss of dominant whitebark pine forests, and the ecological services they provide, is likely under continuing climate warming and that new research and strategies are needed to respond to the crisis facing whitebark pine.

  16. Climate-driven ground-level ozone extreme in the fall over the Southeast United States.

    Science.gov (United States)

    Zhang, Yuzhong; Wang, Yuhang

    2016-09-06

    Ground-level ozone is adverse to human and vegetation health. High ground-level ozone concentrations usually occur over the United States in the summer, often referred to as the ozone season. However, observed monthly mean ozone concentrations in the southeastern United States were higher in October than July in 2010. The October ozone average in 2010 reached that of July in the past three decades (1980-2010). Our analysis shows that this extreme October ozone in 2010 over the Southeast is due in part to a dry and warm weather condition, which enhances photochemical production, air stagnation, and fire emissions. Observational evidence and modeling analysis also indicate that another significant contributor is enhanced emissions of biogenic isoprene, a major ozone precursor, from water-stressed plants under a dry and warm condition. The latter finding is corroborated by recent laboratory and field studies. This climate-induced biogenic control also explains the puzzling fact that the two extremes of high October ozone both occurred in the 2000s when anthropogenic emissions were lower than the 1980s and 1990s, in contrast to the observed decreasing trend of July ozone in the region. The occurrences of a drying and warming fall, projected by climate models, will likely lead to more active photochemistry, enhanced biogenic isoprene and fire emissions, an extension of the ozone season from summer to fall, and an increase of secondary organic aerosols in the Southeast, posing challenges to regional air quality management.

  17. Temperature fluctuations in the Atlantic Ocean

    International Nuclear Information System (INIS)

    Hjoello, Solfrid Saetre

    2005-01-01

    The article discusses the temperature fluctuations in connection with drought in Africa, the climate in North America, the European heat waves and the frequent tropical hurricanes in the Atlantic Ocean. Problems with climate modelling and some pollution aspects are mentioned

  18. Climate-driven changes to the atmospheric CO2 sink in the subtropical North Pacific Ocean.

    Science.gov (United States)

    Dore, John E; Lukas, Roger; Sadler, Daniel W; Karl, David M

    2003-08-14

    The oceans represent a significant sink for atmospheric carbon dioxide. Variability in the strength of this sink occurs on interannual timescales, as a result of regional and basin-scale changes in the physical and biological parameters that control the flux of this greenhouse gas into and out of the surface mixed layer. Here we analyse a 13-year time series of oceanic carbon dioxide measurements from station ALOHA in the subtropical North Pacific Ocean near Hawaii, and find a significant decrease in the strength of the carbon dioxide sink over the period 1989-2001. We show that much of this reduction in sink strength can be attributed to an increase in the partial pressure of surface ocean carbon dioxide caused by excess evaporation and the accompanying concentration of solutes in the water mass. Our results suggest that carbon dioxide uptake by ocean waters can be strongly influenced by changes in regional precipitation and evaporation patterns brought on by climate variability.

  19. Animal culture impacts species' capacity to realise climate-driven range shifts

    DEFF Research Database (Denmark)

    Keith, Sally A.; Bull, Joseph William

    2017-01-01

    Ecological predictions of how species will shift their geographical distributions under climate change generally consider individuals as machines that respond optimally to changing environmental conditions. However, animals frequently make active behavioural decisions based on imperfect information...... about their external environment, potentially mediated by information transmitted through social learning (i.e. culture). Vertical transmission of culture (between generations) might encourage conservative behaviour, constraining the ability of a species to respond, whilst horizontal transmission...... (within generations) can encourage innovation and so facilitate dynamic responses to a changing environment. We believe that the time is right to unite recent advances in ecological modelling and behavioural understanding to explicitly incorporate the influence of animal culture into future predictions...

  20. Climate-driven vertical acceleration of Icelandic crust measured by continuous GPS geodesy

    KAUST Repository

    Compton, Kathleen; Bennett, Richard A.; Hreinsdó ttir, Sigrú n

    2015-01-01

    © 2015 The Authors. Earth's present-day response to enhanced glacial melting resulting from climate change can be measured using Global Positioning System (GPS) technology. We present data from 62 continuously operating GPS instruments in Iceland. Statistically significant upward velocity and accelerations are recorded at 27 GPS stations, predominantly located in the Central Highlands region of Iceland, where present-day thinning of the Iceland ice caps results in velocities of more than 30mm/yr and uplift accelerations of 1-2mm/yr2. We use our acceleration estimates to back calculate to a time of zero velocity, which coincides with the initiation of ice loss in Iceland from ice mass balance calculations and Arctic warming trends. We show, through a simple inversion, a direct relationship between ice mass balance measurements and vertical position and show that accelerated unloading is required to reproduce uplift observations for a simple elastic layer over viscoelastic half-space model.

  1. Human population growth offsets climate-driven increase in woody vegetation in sub-Saharan Africa.

    Science.gov (United States)

    Brandt, Martin; Rasmussen, Kjeld; Peñuelas, Josep; Tian, Feng; Schurgers, Guy; Verger, Aleixandre; Mertz, Ole; Palmer, John R B; Fensholt, Rasmus

    2017-03-06

    The rapidly growing human population in sub-Saharan Africa generates increasing demand for agricultural land and forest products, which presumably leads to deforestation. Conversely, a greening of African drylands has been reported, but this has been difficult to associate with changes in woody vegetation. There is thus an incomplete understanding of how woody vegetation responds to socio-economic and environmental change. Here we used a passive microwave Earth observation data set to document two different trends in land area with woody cover for 1992-2011: 36% of the land area (6,870,000 km 2 ) had an increase in woody cover largely in drylands, and 11% had a decrease (2,150,000 km 2 ), mostly in humid zones. Increases in woody cover were associated with low population growth, and were driven by increases in CO 2 in the humid zones and by increases in precipitation in drylands, whereas decreases in woody cover were associated with high population growth. The spatially distinct pattern of these opposing trends reflects, first, the natural response of vegetation to precipitation and atmospheric CO 2 , and second, deforestation in humid areas, minor in size but important for ecosystem services, such as biodiversity and carbon stocks. This nuanced picture of changes in woody cover challenges widely held views of a general and ongoing reduction of the woody vegetation in Africa.

  2. Regional Climate Modeling and Remote Sensing to Characterize Impacts of Civil War Driven Land Use Change on Regional Hydrology and Climate

    Science.gov (United States)

    Maksimowicz, M.; Masarik, M. T.; Brandt, J.; Flores, A. N.

    2016-12-01

    Land use/land cover (LULC) change directly impacts the partitioning of surface mass and energy fluxes. Regional-scale weather and climate are potentially altered by LULC if the resultant changes in partitioning of surface energy fluxes are extensive enough. Dynamics of land use, particularly those related to the social dimensions of the Earth System, are often simplified or not represented in regional land-atmosphere models. This study explores the role of LULC change on a regional hydroclimate system, focusing on potential hydroclimate changes arising from an extended civil conflict in Mozambique. Civil war from 1977-1992 in Mozambique led to land use change at a regional scale as a result of the collapse of large herbivore populations due to poaching. Since the war ended, farming has increased, poaching was curtailed, and animal populations were reintroduced. In this study LULC in a region encompassing Gorongosa is classified at three instances between 1977 to 2015 using Landsat imagery. We use these derived LULC datasets to inform lower boundary conditions in the Weather Research and Forecasting (WRF) model. To quantify potential hydrometeorological changes arising from conflict-driven land use change, we performed a factorial-like experiment by mixing input LULC maps and atmospheric forcing data from before, during, and after the civil war. Analysis of the Landsat data shows measurable land cover change from 1977-present as tree cover encroached into grasslands. Initial tests show corresponding sensitivities to different LULC schemes within the WRF model. Preliminary results suggest that the war did indeed impact regional hydroclimate in a significant way via its direct and indirect impacts on land-atmosphere interactions. Results of this study suggest that LULC change arising from regional conflicts are a potentially understudied, yet important human process to capture in both regional reanalyses and climate change projections.

  3. Climate-driven vertical acceleration of Icelandic crust measured by continuous GPS geodesy

    KAUST Repository

    Compton, Kathleen

    2015-02-06

    © 2015 The Authors. Earth\\'s present-day response to enhanced glacial melting resulting from climate change can be measured using Global Positioning System (GPS) technology. We present data from 62 continuously operating GPS instruments in Iceland. Statistically significant upward velocity and accelerations are recorded at 27 GPS stations, predominantly located in the Central Highlands region of Iceland, where present-day thinning of the Iceland ice caps results in velocities of more than 30mm/yr and uplift accelerations of 1-2mm/yr2. We use our acceleration estimates to back calculate to a time of zero velocity, which coincides with the initiation of ice loss in Iceland from ice mass balance calculations and Arctic warming trends. We show, through a simple inversion, a direct relationship between ice mass balance measurements and vertical position and show that accelerated unloading is required to reproduce uplift observations for a simple elastic layer over viscoelastic half-space model.

  4. Feedback-driven response to multidecadal climatic variability at an alpine treeline

    Science.gov (United States)

    Alftine, K.J.; Malanson, G.P.; Fagre, D.B.

    2003-01-01

    The Pacific Decadal Oscillation (PDO) has significant climatological and ecological effects in northwestern North America. Its possible effects and their modification by feedbacks are examined in the forest-tundra ecotone in Glacier National Park, Montana, USA. Tree ring samples were collected to estimate establishment dates in 10 quadrats. Age-diameter regressions were used to estimate the ages of uncored trees. The temporal pattern of establishment and survival was compared to the pattern of the PDO. A wave of establishment began in the mid-1940s, rose to a peak rate in the mid-1970s, and dropped precipitously beginning ca. 1980 to near zero for the 1990s. The period of establishment primarily coincided with the negative phase of the PDO, but the establishment and survival pattern is not correlated with the PDO index. The pattern indicates a period during which establishment was possible and was augmented by positive feedback from surviving trees. Snow may be the most important factor in the feedback, but studies indicate that its effects vary locally. Spatially differentiated analyses of decadal or longer periodicity may elucidate responses to climatic variation. ?? 2003 by V. H. Winston and Son, Inc. All rights reserved.

  5. Forecasting the poleward range expansion of an intertidal species driven by climate alterations

    Directory of Open Access Journals (Sweden)

    Raquel Xavier

    2010-11-01

    Full Text Available Accurate distributional models can be used to reliably predict the response of organisms to climatic changes. Though such models have been extensively applied to terrestrial organisms, they have hardly ever been applied to the marine environment. Recent changes in the distribution of the marine gastropod Patella rustica (L. were previously modelled with Classification and Regression Tree (CART and the results revealed that increases in temperature were the major driver of those changes. However, the accuracy scores during the validation of the model were unsatisfactory, preventing its use for forecasting purposes. To fulfil this objective, in the present study a more robust method, Artificial Neural Network (ANN, was employed to produce a model suited to forecasting changes in the distribution of P. rustica. Results confirmed that the ANN model behaved better than the CART, and that it could be used for forecasting future distributional scenarios. The model forecasts that by the 2020s P. rustica is likely to expand its range at least 1000 km northwards. These results should be interpreted with caution considering the dispersal limitations of this species, but if such an expansion took place, major changes in the colonized ecosystems are expected due to the key role of limpets in intertidal communities.

  6. The treatment of climate-driven environmental change and associated uncertainty in post-closure assessments

    International Nuclear Information System (INIS)

    Wilmot, R.D.

    1993-01-01

    The post-closure performance of radioactive waste repositories is influenced by a range of processes such as groundwater flow and fracture movement which are in turn affected by conditions in the surface environment. For deep repositories the period for which an assessment must be performed is in the order of 10 6 years. The geological record of the last 10 6 years shows that surface environmental conditions have varied considerably over such time-scales. A model of surface environmental change, known as TIME4, has been developed on behalf of the UK Department of the Environment for use with the probabilistic risk assessment code VANDAL. This paper describes the extent of surface environmental change, discusses possible driving mechanisms for such changes and summarises the processes which have been incorporated within the TIME4 model. The underlying cause of change in surface environment sub-systems is inferred to be climate change but considerable uncertainty remains over the mechanisms of such change. Methods for treating these uncertainties are described. (author)

  7. Response of faults to climate-driven changes in ice and water volumes on Earth's surface.

    Science.gov (United States)

    Hampel, Andrea; Hetzel, Ralf; Maniatis, Georgios

    2010-05-28

    Numerical models including one or more faults in a rheologically stratified lithosphere show that climate-induced variations in ice and water volumes on Earth's surface considerably affect the slip evolution of both thrust and normal faults. In general, the slip rate and hence the seismicity of a fault decreases during loading and increases during unloading. Here, we present several case studies to show that a postglacial slip rate increase occurred on faults worldwide in regions where ice caps and lakes decayed at the end of the last glaciation. Of note is that the postglacial amplification of seismicity was not restricted to the areas beneath the large Laurentide and Fennoscandian ice sheets but also occurred in regions affected by smaller ice caps or lakes, e.g. the Basin-and-Range Province. Our results do not only have important consequences for the interpretation of palaeoseismological records from faults in these regions but also for the evaluation of the future seismicity in regions currently affected by deglaciation like Greenland and Antarctica: shrinkage of the modern ice sheets owing to global warming may ultimately lead to an increase in earthquake frequency in these regions.

  8. River piracy and drainage basin reorganization led by climate-driven glacier retreat

    Science.gov (United States)

    Shugar, Daniel H.; Clague, John J.; Best, James L.; Schoof, Christian; Willis, Michael J.; Copland, Luke; Roe, Gerard H.

    2017-04-01

    River piracy--the diversion of the headwaters of one stream into another one--can dramatically change the routing of water and sediment, with a profound effect on landscape evolution. Stream piracy has been investigated in glacial environments, but so far it has mainly been studied over Quaternary or longer timescales. Here we document how retreat of Kaskawulsh Glacier--one of Canada's largest glaciers--abruptly and radically altered the regional drainage pattern in spring 2016. We use a combination of hydrological measurements and drone-generated digital elevation models to show that in late May 2016, meltwater from the glacier was re-routed from discharge in a northward direction into the Bering Sea, to southward into the Pacific Ocean. Based on satellite image analysis and a signal-to-noise ratio as a metric of glacier retreat, we conclude that this instance of river piracy was due to post-industrial climate change. Rapid regional drainage reorganizations of this type can have profound downstream impacts on ecosystems, sediment and carbon budgets, and downstream communities that rely on a stable and sustained discharge. We suggest that the planforms of Slims and Kaskawulsh rivers will adjust in response to altered flows, and the future Kaskawulsh watershed will extend into the now-abandoned headwaters of Slims River and eventually capture the Kluane Lake drainage.

  9. Climate change and ocean deoxygenation within intensified surface-driven upwelling circulations.

    Science.gov (United States)

    Bakun, Andrew

    2017-09-13

    Ocean deoxygenation often takes place in proximity to zones of intense upwelling. Associated concerns about amplified ocean deoxygenation arise from an arguable likelihood that coastal upwelling systems in the world's oceans may further intensify as anthropogenic climate change proceeds. Comparative examples discussed include the uniquely intense seasonal Somali Current upwelling, the massive upwelling that occurs quasi-continuously off Namibia and the recently appearing and now annually recurring 'dead zone' off the US State of Oregon. The evident 'transience' in causal dynamics off Oregon is somewhat mirrored in an interannual-scale intermittence in eruptions of anaerobically formed noxious gases off Namibia. A mechanistic scheme draws the three examples towards a common context in which, in addition to the obvious but politically problematic remedy of actually reducing 'greenhouse' gas emissions, the potentially manageable abundance of strongly swimming, finely gill raker-meshed small pelagic fish emerges as a plausible regulating factor.This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'. © 2017 The Author(s).

  10. Impact of wind-driven rain on historic brick wall buildings in a moderately cold and humid climate: Numerical analyses of mould growth risk, indoor climate and energy consumption

    DEFF Research Database (Denmark)

    Masaru, Abuku; Janssen, Hans; Roels, Staf

    2009-01-01

    This paper gives an onset to whole building hygrothermal modelling in which the interaction between interior and exterior climates via building enclosures is simulated under a moderately cold and humid climate. The focus is particularly on the impact of wind-driven rain (WDR) oil the hygrothermal...... response, mould growth at interior wall surfaces, indoor climate and energy consumption. First the WDR load oil the facades of a 4 m x 4 m x 10 m tower is determined. Then the hygrothermal behaviour of the brick walls is analysed oil a horizontal slice through the tower. The simulations demonstrate...

  11. Collaborative Project: The problem of bias in defining uncertainty in computationally enabled strategies for data-driven climate model development. Final Technical Report.

    Energy Technology Data Exchange (ETDEWEB)

    Huerta, Gabriel [Univ. of New Mexico, Albuquerque, NM (United States)

    2016-05-10

    The objective of the project is to develop strategies for better representing scientific sensibilities within statistical measures of model skill that then can be used within a Bayesian statistical framework for data-driven climate model development and improved measures of model scientific uncertainty. One of the thorny issues in model evaluation is quantifying the effect of biases on climate projections. While any bias is not desirable, only those biases that affect feedbacks affect scatter in climate projections. The effort at the University of Texas is to analyze previously calculated ensembles of CAM3.1 with perturbed parameters to discover how biases affect projections of global warming. The hypothesis is that compensating errors in the control model can be identified by their effect on a combination of processes and that developing metrics that are sensitive to dependencies among state variables would provide a way to select version of climate models that may reduce scatter in climate projections. Gabriel Huerta at the University of New Mexico is responsible for developing statistical methods for evaluating these field dependencies. The UT effort will incorporate these developments into MECS, which is a set of python scripts being developed at the University of Texas for managing the workflow associated with data-driven climate model development over HPC resources. This report reflects the main activities at the University of New Mexico where the PI (Huerta) and the Postdocs (Nosedal, Hattab and Karki) worked on the project.

  12. The influence of climatically-driven surface loading variations on continental strain and seismicity

    Science.gov (United States)

    Craig, Tim; Calais, Eric; Fleitout, Luce; Bollinger, Laurent; Scotti, Oona

    2016-04-01

    In slowly deforming regions of plate interiors, secondary sources of stress and strain can result in transient deformation rates comparable to, or greater than, the background tectonic rates. Highly variable in space and time, these transients have the potential to influence the spatio-temporal distribution of seismicity, interfering with any background tectonic effects to either promote or inhibit the failure of pre-existing faults, and potentially leading to a clustered, or 'pulse-like', seismic history. Here, we investigate the ways in which the large-scale deformation field resulting from climatically-controlled changes in surface ice mass over the Pleistocene and Holocene may have influenced not only the seismicity of glaciated regions, but also the wider seismicity around the ice periphery. We first use a set of geodynamic models to demonstrate that a major pulse of seismic activity occurring in Fennoscandia, coincident with the time of end-glaciation, occurred in a setting where the contemporaneous horizontal strain-rate resulting from the changing ice mass, was extensional - opposite to the reverse sense of coseismic displacement accommodated on these faults. Therefore, faulting did not release extensional elastic strain that was building up at the time of failure, but compressional elastic strain that had accumulated in the lithosphere on timescales longer than the glacial cycle, illustrating the potential for a non-tectonic trigger to tap in to the background tectonic stress-state. We then move on to investigate the more distal influence that changing ice (and ocean) volumes may have had on the evolving strain field across intraplate Europe, how this is reflected in the seismicity across intraplate Europe, and what impact this might have on the paleoseismic record.

  13. Analysis of the Relationship Between Climate and NDVI Variability at Global Scales

    Science.gov (United States)

    Zeng, Fan-Wei; Collatz, G. James; Pinzon, Jorge; Ivanoff, Alvaro

    2011-01-01

    interannual variability in modeled (CASA) C flux is in part caused by interannual variability in Normalized Difference Vegetation Index (NDVI) Fraction of Photosynthetically Active Radiation (FPAR). This study confirms a mechanism producing variability in modeled NPP: -- NDVI (FPAR) interannual variability is strongly driven by climate; -- The climate driven variability in NDVI (FPAR) can lead to much larger fluctuation in NPP vs. the NPP computed from FPAR climatology

  14. Influence of urbanization-driven land use/cover change on climate: The case of Addis Ababa, Ethiopia

    Science.gov (United States)

    Arsiso, Bisrat Kifle; Mengistu Tsidu, Gizaw; Stoffberg, Gerrit Hendrik; Tadesse, Tsegaye

    2018-06-01

    Land use change is the second most important anthropogenic influence on climate beside the emission of greenhouse gases. Urbanization is leading to significant land use changes in Africa since the continent is undergoing rapid urbanization and population growth in recent decades. Addis Ababa is one of these fast growing cities in the continent. Therefore, detection of land use change is very important to identify its impact on climate and sustainable land use management of the city. The study used Landsat images to generate land use/land cover change map for the city. The normalized difference vegetation index (NDVI) is used to detect the major changes of vegetation cover occurred between 1986 and 2011 as a result of land use and land cover change. Downscaled HadCM3 simulations under A2 and B2 emission scenarios is used to investigate future urban heat island (UHI) over the city of Addis Ababa. In the city, the analysis of Landsat images has shown that the built-up areas have increased by 121.88 km2 within the last 25 years. This finding is consistent with NDVI images taken over the same period that reveal a decline in vegetation cover. The impact of the urbanization-driven land use/cover change has resulted in notable nocturnal urban heat island (UHI) as revealed from an average increase in minimum temperature of 1.5 °C at the centre of the city relative to rural site over the 1960-2001 period. The mean of the 2006-2010 spatial minimum temperature anomaly with respect to the base period mean of 1981-2005 is consistent with the observed UHI. The temperature in the central areas (both commercial and residential sectors) of Addis Ababa is warmer than the surrounding areas. The thermal gradient increase from about 1.44 °C at the centre (Arada, Addis Ketema, Lideta and Kirkos) to 0.21 °C at the peripheral parts of the city (Gulele, Bole, Nefasilk-Lafto, Kolfe Keranio and east of Yeka sub-cities) transecting across the hot (high-density urban) to moderately warm to

  15. Nonequilibrium fluctuations in a resistor.

    Science.gov (United States)

    Garnier, N; Ciliberto, S

    2005-06-01

    In small systems where relevant energies are comparable to thermal agitation, fluctuations are of the order of average values. In systems in thermodynamical equilibrium, the variance of these fluctuations can be related to the dissipation constant in the system, exploiting the fluctuation-dissipation theorem. In nonequilibrium steady systems, fluctuations theorems (FT) additionally describe symmetry properties of the probability density functions (PDFs) of the fluctuations of injected and dissipated energies. We experimentally probe a model system: an electrical dipole driven out of equilibrium by a small constant current I, and show that FT are experimentally accessible and valid. Furthermore, we stress that FT can be used to measure the dissipated power P = R I2 in the system by just studying the PDFs' symmetries.

  16. Changes in North Atlantic deep-sea temperature during climatic fluctuations of the last 25,000 years based on ostracode Mg/Ca ratios

    Science.gov (United States)

    Dwyer, Gary S.; Cronin, Thomas M.; Baker, Paul A.; Rodriguez-Lazaro, Julio

    2000-01-01

    values that match those of the early Holocene maximum of ∼7°C. Intermediate water BWT changes must also be driven by changes in ocean circulation. These results thus provide independent evidence that supports the hypothesis that deep-ocean circulation is closely linked to climate change over a range of timescales regardless of the mean climate state. More generally, the results further demonstrate the potential of benthic Mg/Ca ratios as a tool for reconstructing past ocean and climate conditions.

  17. Quantum fluctuations

    International Nuclear Information System (INIS)

    Reynaud, S.; Giacobino, S.; Zinn-Justin, J.

    1997-01-01

    This course is dedicated to present in a pedagogical manner the recent developments in peculiar fields concerned by quantum fluctuations: quantum noise in optics, light propagation through dielectric media, sub-Poissonian light generated by lasers and masers, quantum non-demolition measurements, quantum electrodynamics applied to cavities and electrical circuits involving superconducting tunnel junctions. (A.C.)

  18. Simulation of climate-tick-host-landscape interactions: Effects of shifts in the seasonality of host population fluctuations on tick densities.

    Science.gov (United States)

    Wang, Hsiao-Hsuan; Grant, W E; Teel, P D; Hamer, S A

    2015-12-01

    Tick vector systems are comprised of complex climate-tick-host-landscape interactions that are difficult to identify and estimate from empirical observations alone. We developed a spatially-explicit, individual-based model, parameterized to represent ecological conditions typical of the south-central United States, to examine effects of shifts in the seasonal occurrence of fluctuations of host densities on tick densities. Simulated shifts in the seasonal occurrence of periods of high and low host densities affected both the magnitude of unfed tick densities and the seasonality of tick development. When shifting the seasonal densities of all size classes of hosts (small, medium, and large) synchronously, densities of nymphs were affected more by smaller shifts away from the baseline host seasonality than were densities of larval and adult life stages. When shifting the seasonal densities of only a single size-class of hosts while holding other size classes at their baseline levels, densities of larval, nymph, and adult life stages responded differently. Shifting seasonal densities of any single host-class earlier resulted in a greater increase in adult tick density than when seasonal densities of all host classes were shifted earlier simultaneously. The mean densities of tick life stages associated with shifts in host densities resulted from system-level interactions of host availability with tick phenology. For example, shifting the seasonality of all hosts ten weeks earlier resulted in an approximately 30% increase in the relative degree of temporal co-occurrence of actively host-seeking ticks and hosts compared to baseline, whereas shifting the seasonality of all hosts ten weeks later resulted in an approximately 70% decrease compared to baseline. Differences among scenarios in the overall presence of active host-seeking ticks in the system were due primarily to the degree of co-occurrence of periods of high densities of unfed ticks and periods of high densities

  19. Insects in fluctuating thermal environments.

    Science.gov (United States)

    Colinet, Hervé; Sinclair, Brent J; Vernon, Philippe; Renault, David

    2015-01-07

    All climate change scenarios predict an increase in both global temperature means and the magnitude of seasonal and diel temperature variation. The nonlinear relationship between temperature and biological processes means that fluctuating temperatures lead to physiological, life history, and ecological consequences for ectothermic insects that diverge from those predicted from constant temperatures. Fluctuating temperatures that remain within permissive temperature ranges generally improve performance. By contrast, those which extend to stressful temperatures may have either positive impacts, allowing repair of damage accrued during exposure to thermal extremes, or negative impacts from cumulative damage during successive exposures. We discuss the mechanisms underlying these differing effects. Fluctuating temperatures could be used to enhance or weaken insects in applied rearing programs, and any prediction of insect performance in the field-including models of climate change or population performance-must account for the effect of fluctuating temperatures.

  20. Sap-feeding insects on forest trees along latitudinal gradients in northern Europe: a climate-driven patterns.

    Science.gov (United States)

    Kozlov, Mikhail V; Stekolshchikov, Andrey V; Söderman, Guy; Labina, Eugenia S; Zverev, Vitali; Zvereva, Elena L

    2015-01-01

    Knowledge of the latitudinal patterns in biotic interactions, and especially in herbivory, is crucial for understanding the mechanisms that govern ecosystem functioning and for predicting their responses to climate change. We used sap-feeding insects as a model group to test the hypotheses that the strength of plant-herbivore interactions in boreal forests decreases with latitude and that this latitudinal pattern is driven primarily by midsummer temperatures. We used a replicated sampling design and quantitatively collected and identified all sap-feeding insects from four species of forest trees along five latitudinal gradients (750-1300 km in length, ten sites in each gradient) in northern Europe (59 to 70°N and 10 to 60°E) during 2008-2011. Similar decreases in diversity of sap-feeding insects with latitude were observed in all gradients during all study years. The sap-feeder load (i.e. insect biomass per unit of foliar biomass) decreased with latitude in typical summers, but increased in an exceptionally hot summer and was independent of latitude during a warm summer. Analysis of combined data from all sites and years revealed dome-shaped relationships between the loads of sap-feeders and midsummer temperatures, peaking at 17 °C in Picea abies, at 19.5 °C in Pinus sylvestris and Betula pubescens and at 22 °C in B. pendula. From these relationships, we predict that the losses of forest trees to sap-feeders will increase by 0-45% of the current level in southern boreal forests and by 65-210% in subarctic forests with a 1 °C increase in summer temperatures. The observed relationships between temperatures and the loads of sap-feeders differ between the coniferous and deciduous tree species. We conclude that climate warming will not only increase plant losses to sap-feeding insects, especially in subarctic forests, but can also alter plant-plant interactions, thereby affecting both the productivity and the structure of future forest ecosystems. © 2014

  1. Nonequilibrium quantum fluctuations of work.

    Science.gov (United States)

    Allahverdyan, A E

    2014-09-01

    The concept of work is basic for statistical thermodynamics. To gain a fuller understanding of work and its (quantum) features, it needs to be represented as an average of a fluctuating quantity. Here I focus on the work done between two moments of time for a thermally isolated quantum system driven by a time-dependent Hamiltonian. I formulate two natural conditions needed for the fluctuating work to be physically meaningful for a system that starts its evolution from a nonequilibrium state. The existing definitions do not satisfy these conditions due to issues that are traced back to noncommutativity. I propose a definition of fluctuating work that is free of previous drawbacks and that applies for a wide class of nonequilibrium initial states. It allows the deduction of a generalized work-fluctuation theorem that applies for an arbitrary (out-of-equilibrium) initial state.

  2. Evidence from northwest European bogs shows ‘Little Ice Age’ climatic changes driven by variations in solar activity

    NARCIS (Netherlands)

    Mauquoy, D; van Geel, B; Blaauw, Maarten; van der Plicht, J

    2002-01-01

    Fluctuations in Holocene atmospheric radiocarbon concentrations have been shown to be due to variations in solar activity. Analyses of both Be-10 and C-14 nuclides confirm that production-rate changes during the Holocene were largely modulated by solar activity. Analyses of peat samples from two

  3. Spatial and temporal variation in the relative contribution of density dependence, climate variation and migration to fluctuations in the size of great tit populations

    NARCIS (Netherlands)

    Grøtan, V.; Sæther, B-E.; Engen, S.; van Balen, J.H.; Perdeck, A.C.; Visser, M.E.

    2009-01-01

    1. The aim of the present study is to model the stochastic variation in the size of five populations of great tit Parus major in the Netherlands, using a combination of individual-based demographic data and time series of population fluctuations. We will examine relative contribution of

  4. Fluctuation analysis

    International Nuclear Information System (INIS)

    Clarke, J.

    1980-01-01

    This paper briefly reviews sources of noise in Josephson junctions, and the limits they impose on the sensitivity of dc and rf SQUIDS. The results are strictly valid only for a resistively shunted junction (RSJ) with zero capacitance, but should be applicable to point contact junctions and microbridges in so far as these devices can be approximated by the RSJ model. Fluctuations arising from Nyquist noise in the resistive shunt of a single junction are discussed in the limit eI/sub o/R/k/sub B/T << 1 in which a classical treatment is appropriate, and then extend the treatment to the limit eI/sub o/R/k/sub B/T greater than or equal to 1 in which quantum effects become important. The Nyquist limit theory is used to calculate the noise in a dc SQUID, and the results are compared with a number of practical devices. The quantum limit is briefly considered. Results for the predicted sensitivity of rf SQUIDS are presented, and also compared with a number of practical devices. Finally, the importance of l/f noise (f is the frequency) in limiting the low frequency performance of SQUIDS is discussed

  5. Derivation of RCM-driven potential evapotranspiration for hydrological climate change impact analysis in Great Britain: a comparison of methods and associated uncertainty in future projections

    Directory of Open Access Journals (Sweden)

    C. Prudhomme

    2013-04-01

    Full Text Available Potential evapotranspiration (PET is the water that would be lost by plants through evaporation and transpiration if water was not limited in the soil, and it is commonly used in conceptual hydrological modelling in the calculation of runoff production and hence river discharge. Future changes of PET are likely to be as important as changes in precipitation patterns in determining changes in river flows. However PET is not calculated routinely by climate models so it must be derived independently when the impact of climate change on river flow is to be assessed. This paper compares PET estimates from 12 equations of different complexity, driven by the Hadley Centre's HadRM3-Q0 model outputs representative of 1961–1990, with MORECS PET, a product used as reference PET in Great Britain. The results show that the FAO56 version of the Penman–Monteith equations reproduces best the spatial and seasonal variability of MORECS PET across GB when driven by HadRM3-Q0 estimates of relative humidity, total cloud, wind speed and linearly bias-corrected mean surface temperature. This suggests that potential biases in HadRM3-Q0 climate do not result in significant biases when the physically based FAO56 equations are used. Percentage changes in PET between the 1961–1990 and 2041–2070 time slices were also calculated for each of the 12 PET equations from HadRM3-Q0. Results show a large variation in the magnitude (and sometimes direction of changes estimated from different PET equations, with Turc, Jensen–Haise and calibrated Blaney–Criddle methods systematically projecting the largest increases across GB for all months and Priestley–Taylor, Makkink, and Thornthwaite showing the smallest changes. We recommend the use of the FAO56 equation as, when driven by HadRM3-Q0 climate data, this best reproduces the reference MORECS PET across Great Britain for the reference period of 1961–1990. Further, the future changes of PET estimated by FAO56 are within

  6. Climate-driven environmental changes around 8,200 years ago favoured increases in cetacean strandings and Mediterranean hunter-gatherers exploited them.

    Science.gov (United States)

    Mannino, Marcello A; Talamo, Sahra; Tagliacozzo, Antonio; Fiore, Ivana; Nehlich, Olaf; Piperno, Marcello; Tusa, Sebastiano; Collina, Carmine; Di Salvo, Rosaria; Schimmenti, Vittoria; Richards, Michael P

    2015-11-17

    Cetacean mass strandings occur regularly worldwide, yet the compounded effects of natural and anthropogenic factors often complicate our understanding of these phenomena. Evidence of past stranding episodes may, thus, be essential to establish the potential influence of climate change. Investigations on bones from the site of Grotta dell'Uzzo in North West Sicily (Italy) show that the rapid climate change around 8,200 years ago coincided with increased strandings in the Mediterranean Sea. Stable isotope analyses on collagen from a large sample of remains recovered at this cave indicate that Mesolithic hunter-gatherers relied little on marine resources. A human and a red fox dating to the 8.2-kyr-BP climatic event, however, acquired at least one third of their protein from cetaceans. Numerous carcasses should have been available annually, for at least a decade, to obtain these proportions of meat. Our findings imply that climate-driven environmental changes, caused by global warming, may represent a serious threat to cetaceans in the near future.

  7. Future habitat loss and extinctions driven by land-use change in biodiversity hotspots under four scenarios of climate-change mitigation.

    Science.gov (United States)

    Jantz, Samuel M; Barker, Brian; Brooks, Thomas M; Chini, Louise P; Huang, Qiongyu; Moore, Rachel M; Noel, Jacob; Hurtt, George C

    2015-08-01

    Numerous species have been pushed into extinction as an increasing portion of Earth's land surface has been appropriated for human enterprise. In the future, global biodiversity will be affected by both climate change and land-use change, the latter of which is currently the primary driver of species extinctions. How societies address climate change will critically affect biodiversity because climate-change mitigation policies will reduce direct climate-change impacts; however, these policies will influence land-use decisions, which could have negative impacts on habitat for a substantial number of species. We assessed the potential impact future climate policy could have on the loss of habitable area in biodiversity hotspots due to associated land-use changes. We estimated past extinctions from historical land-use changes (1500-2005) based on the global gridded land-use data used for the Intergovernmental Panel on Climate Change Fifth Assessment Report and habitat extent and species data for each hotspot. We then estimated potential extinctions due to future land-use changes under alternative climate-change scenarios (2005-2100). Future land-use changes are projected to reduce natural vegetative cover by 26-58% in the hotspots. As a consequence, the number of additional species extinctions, relative to those already incurred between 1500 and 2005, due to land-use change by 2100 across all hotspots ranged from about 220 to 21000 (0.2% to 16%), depending on the climate-change mitigation scenario and biological factors such as the slope of the species-area relationship and the contribution of wood harvest to extinctions. These estimates of potential future extinctions were driven by land-use change only and likely would have been higher if the direct effects of climate change had been considered. Future extinctions could potentially be reduced by incorporating habitat preservation into scenario development to reduce projected future land-use changes in hotspots or by

  8. Climate- and successional-related changes in functional composition of European forests are strongly driven by tree mortality.

    Science.gov (United States)

    Ruiz-Benito, Paloma; Ratcliffe, Sophia; Zavala, Miguel A; Martínez-Vilalta, Jordi; Vilà-Cabrera, Albert; Lloret, Francisco; Madrigal-González, Jaime; Wirth, Christian; Greenwood, Sarah; Kändler, Gerald; Lehtonen, Aleksi; Kattge, Jens; Dahlgren, Jonas; Jump, Alistair S

    2017-10-01

    Intense droughts combined with increased temperatures are one of the major threats to forest persistence in the 21st century. Despite the direct impact of climate change on forest growth and shifts in species abundance, the effect of altered demography on changes in the composition of functional traits is not well known. We sought to (1) quantify the recent changes in functional composition of European forests; (2) identify the relative importance of climate change, mean climate and forest development for changes in functional composition; and (3) analyse the roles of tree mortality and growth underlying any functional changes in different forest types. We quantified changes in functional composition from the 1980s to the 2000s across Europe by two dimensions of functional trait variation: the first dimension was mainly related to changes in leaf mass per area and wood density (partially related to the trait differences between angiosperms and gymnosperms), and the second dimension was related to changes in maximum tree height. Our results indicate that climate change and mean climatic effects strongly interacted with forest development and it was not possible to completely disentangle their effects. Where recent climate change was not too extreme, the patterns of functional change generally followed the expected patterns under secondary succession (e.g. towards late-successional short-statured hardwoods in Mediterranean forests and taller gymnosperms in boreal forests) and latitudinal gradients (e.g. larger proportion of gymnosperm-like strategies at low water availability in forests formerly dominated by broad-leaved deciduous species). Recent climate change generally favoured the dominance of angiosperm-like related traits under increased temperature and intense droughts. Our results show functional composition changes over relatively short time scales in European forests. These changes are largely determined by tree mortality, which should be further

  9. A framework for examining climate-driven changes to the seasonality and geographical range of coastal pathogens and harmful algae

    Directory of Open Access Journals (Sweden)

    John Jacobs

    2015-01-01

    Full Text Available Climate change is expected to alter coastal ecosystems in ways which may have predictable consequences for the seasonality and geographical distribution of human pathogens and harmful algae. Here we demonstrate relatively simple approaches for evaluating the risk of occurrence of pathogenic bacteria in the genus Vibrio and outbreaks of toxin-producing harmful algae in the genus Alexandrium, with estimates of uncertainty, in U.S. coastal waters under future climate change scenarios through the end of the 21st century. One approach forces empirical models of growth, abundance and the probability of occurrence of the pathogens and algae at specific locations in the Chesapeake Bay and Puget Sound with ensembles of statistically downscaled climate model projections to produce first order assessments of changes in seasonality. In all of the case studies examined, the seasonal window of occurrence for Vibrio and Alexandrium broadened, indicating longer annual periods of time when there is increased risk for outbreaks. A second approach uses climate model projections coupled with GIS to identify the potential for geographic range shifts for Vibrio spp. in the coastal waters of Alaska. These two approaches could be applied to other coastal pathogens that have climate sensitive drivers to investigate potential changes to the risk of outbreaks in both time (seasonality and space (geographical distribution under future climate change scenarios.

  10. Mid- to late Holocene climate-driven regime shifts inferred from diatom, ostracod and stable isotope records from Lake Son Kol (Central Tian Shan, Kyrgyzstan)

    Science.gov (United States)

    Schwarz, Anja; Turner, Falko; Lauterbach, Stefan; Plessen, Birgit; Krahn, Kim J.; Glodniok, Sven; Mischke, Steffen; Stebich, Martina; Witt, Roman; Mingram, Jens; Schwalb, Antje

    2017-12-01

    Arid Central Asia represents a key region for understanding climate variability and interactions in the Northern Hemisphere. Patterns and mechanisms of Holocene climate change in arid Central Asia are, however, only partially understood. Multi-proxy data combining diatom, ostracod, sedimentological, geochemical and stable isotope analyses from a ca. 6000-year-old lake sediment core from Son Kol (Central Kyrgyzstan) show distinct and repeated changes in species assemblages. Diatom- and ostracod-inferred conductivity shifts between meso-euhaline and freshwater conditions suggest water balance and regime shifts. Organism-derived data are corroborated by stable isotope, mineralogical and geochemical records, underlining that Son Kol was affected by strong lake level fluctuations of several meters. The δ13Ccarb/δ18Ocarb correlation shows repeated switchovers from a closed to an open lake system. From 6000 to 3800 and 3250 to 1950 cal. yr BP, Son Kol was a closed basin lake with higher conductivities, increased nutrient availability and a water level located below the modern outflow. Son Kol became again a hydrologically open lake at 3800 and 1950 cal. yr BP. Comparisons to other local and regional paleoclimate records indicate that these regime shifts were largely controlled by changing intensity and position of the Westerlies and the Siberian Anticyclone that triggered changes in the amount of winter precipitation. A strong influence of the Westerlies ca. 5000-4400, 3800-3250 and since 1950 cal. yr BP enhanced the amount of precipitation during spring, autumn and winter, whereas cold and dry winters prevailed during phases with a strong Siberian Anticyclone and southward shifted Westerlies at ca. 6000-5000, 4400-3800 and 3250-1950 cal. yr BP. Similarities between variations in winter precipitation at Son Kol and records of the predominant NAO-mode further suggest a teleconnection between wet (dry) winter climate in Central Asia and a positive (negative) NAO

  11. Climate

    International Nuclear Information System (INIS)

    Fellous, J.L.

    2005-02-01

    This book starts with a series of about 20 preconceived ideas about climate and climatic change and analyses each of them in the light of the present day knowledge. Using this approach, it makes a status of the reality of the climatic change, of its causes and of the measures to be implemented to limit its impacts and reduce its most harmful consequences. (J.S.)

  12. The interaction of neutral evolutionary processes with climatically-driven adaptive changes in the 3D shape of the human os coxae.

    Science.gov (United States)

    Betti, Lia; von Cramon-Taubadel, Noreen; Manica, Andrea; Lycett, Stephen J

    2014-08-01

    Differences in the breadth of the pelvis among modern human populations and among extinct hominin species have often been interpreted in the light of thermoregulatory adaptation, whereby a larger pelvic girdle would help preserve body temperature in cold environments while a narrower pelvis would help dissipate heat in tropical climates. There is, however, a theoretical problem in interpreting a pattern of variation as evidence of selection without first accounting for the effects of neutral evolutionary processes (i.e., mutation, genetic drift and migration). Here, we analyse 3D configurations of 27 landmarks on the os coxae of 1494 modern human individuals representing 30 male and 23 female populations from five continents and a range of climatic conditions. We test for the effects of climate on the size and shape of the pelvic bone, while explicitly accounting for population history (i.e., geographically-mediated gene flow and genetic drift). We find that neutral processes account for a substantial proportion of shape variance in the human os coxae in both sexes. Beyond the neutral pattern due to population history, temperature is a significant predictor of shape and size variation in the os coxae, at least in males. The effect of climate on the shape of the pelvic bone, however, is comparatively limited, explaining only a small percentage of shape variation in males and females. In accordance with previous hypotheses, the size of the os coxae tends to increase with decreasing temperature, although the significance of the association is reduced when population history is taken into account. In conclusion, the shape and size of the human os coxae reflect both neutral evolutionary processes and climatically-driven adaptive changes. Neutral processes have a substantial effect on pelvic variation, suggesting such factors will need to be taken into account in future studies of human and fossil hominin coxal variation. Copyright © 2014 Elsevier Ltd. All rights

  13. RF current drive and plasma fluctuations

    International Nuclear Information System (INIS)

    Peysson, Yves; Decker, Joan; Morini, L; Coda, S

    2011-01-01

    The role played by electron density fluctuations near the plasma edge on rf current drive in tokamaks is assessed quantitatively. For this purpose, a general framework for incorporating density fluctuations in existing modelling tools has been developed. It is valid when rf power absorption takes place far from the fluctuating region of the plasma. The ray-tracing formalism is modified in order to take into account time-dependent perturbations of the density, while the Fokker–Planck solver remains unchanged. The evolution of the electron distribution function in time and space under the competing effects of collisions and quasilinear diffusion by rf waves is determined consistently with the time scale of fluctuations described as a statistical process. Using the ray-tracing code C3PO and the 3D linearized relativistic bounce-averaged Fokker–Planck solver LUKE, the effect of electron density fluctuations on the current driven by the lower hybrid (LH) and the electron cyclotron (EC) waves is estimated quantitatively. A thin fluctuating layer characterized by electron drift wave turbulence at the plasma edge is considered. The effect of fluctuations on the LH wave propagation is equivalent to a random scattering process with a broadening of the poloidal mode spectrum proportional to the level of the perturbation. However, in the multipass regime, the LH current density profile remains sensitive to the ray chaotic behaviour, which is not averaged by fluctuations. The effect of large amplitude fluctuations on the EC driven current is found to be similar to an anomalous radial transport of the fast electrons. The resulting lower current drive efficiency and broader current profile are in better agreement with experimental observations. Finally, applied to the ITER ELMy H-mode regime, the model predicts a significant broadening of the EC driven current density profile with the fluctuation level, which can make the stabilization of neoclassical tearing mode potentially

  14. Fluctuations in quantum chaos

    International Nuclear Information System (INIS)

    Casati, G.; Chirikov, B.V.

    1996-01-01

    Various fluctuations in quantum systems with discrete spectrum are discussed, including recent unpublished results. Open questions and unexplained peculiarities of quantum fluctuations are formulated [ru

  15. Fluctuations and stability in the Advanced Toroidal Facility (ATF) torsatron

    International Nuclear Information System (INIS)

    Harris, J.H.; Charlton, L.A.; Bell, J.D.; Bigelow, T.S.; Carreras, B.A.; Colchin, R.J.; Crume, E.C.; Dominguez, N.; Dunlap, J.L.; Dyer, G.R.; England, A.C.; Glowienka, J.C.; Hillis, D.L.; Hiroe, S.; Horton, L.D.; Howe, H.C.; Isler, R.C.; Jernigan, T.C.; Leboeuf, J.N.; Lee, D.K.; Lynch, V.E.; Lyon, J.F.; Menon, M.M.; Murakami, M.; Rasmussen, D.A.; Uckan, T.; Wilgen, J.B.; Wing, W.R.; Bell, G.L.; Crocker, N.A.; Hanson, G.R.; Thomas, C.E.; Wade, M.R.; Ritz, C.P.

    1990-01-01

    We present the results of experimental and theoretical studies of fluctuations and instabilities in the ATF torsatron, a type of stellarator. Measurements of globally coherent magnetic fluctuations in high-β plasmas with narrow pressure profiles produced by a field error show evidence of self-stabilization ('second stability'); the trends are compatible with theoretical analysis of self-stabilization of resistive curvature-driven instabilities, but there are discrepancies between the absolute experimental and theoretical fluctuation amplitudes. Fluctuation measurements in plasma with broad pressure profiles reveal new phenomena--specifically, toroidally localized magnetic fluctuations, whose amplitudes increase with plasma pressure, and coherent density fluctuations with significant radial width

  16. Herbarium records are reliable sources of phenological change driven by climate and provide novel insights into species' phenological cueing mechanisms.

    Science.gov (United States)

    Davis, Charles C; Willis, Charles G; Connolly, Bryan; Kelly, Courtland; Ellison, Aaron M

    2015-10-01

    Climate change has resulted in major changes in the phenology of some species but not others. Long-term field observational records provide the best assessment of these changes, but geographic and taxonomic biases limit their utility. Plant specimens in herbaria have been hypothesized to provide a wealth of additional data for studying phenological responses to climatic change. However, no study to our knowledge has comprehensively addressed whether herbarium data are accurate measures of phenological response and thus applicable to addressing such questions. We compared flowering phenology determined from field observations (years 1852-1858, 1875, 1878-1908, 2003-2006, 2011-2013) and herbarium records (1852-2013) of 20 species from New England, United States. Earliest flowering date estimated from herbarium records faithfully reflected field observations of first flowering date and substantially increased the sampling range across climatic conditions. Additionally, although most species demonstrated a response to interannual temperature variation, long-term temporal changes in phenological response were not detectable. Our findings support the use of herbarium records for understanding plant phenological responses to changes in temperature, and also importantly establish a new use of herbarium collections: inferring primary phenological cueing mechanisms of individual species (e.g., temperature, winter chilling, photoperiod). These latter data are lacking from most investigations of phenological change, but are vital for understanding differential responses of individual species to ongoing climate change. © 2015 Botanical Society of America.

  17. Climate and Pest-Driven Geographic Shifts in Global Coffee Production: Implications for Forest Cover, Biodiversity and Carbon Storage

    Science.gov (United States)

    Magrach, Ainhoa; Ghazoul, Jaboury

    2015-01-01

    Coffee is highly sensitive to temperature and rainfall, making its cultivation vulnerable to geographic shifts in response to a changing climate. This could lead to the establishment of coffee plantations in new areas and potential conflicts with other land covers including natural forest, with consequent implications for biodiversity and ecosystem services. We project areas suitable for future coffee cultivation based on several climate scenarios and expected responses of the coffee berry borer, a principle pest of coffee crops. We show that the global climatically-suitable area will suffer marked shifts from some current major centres of cultivation. Most areas will be suited to Robusta coffee, demand for which could be met without incurring forest encroachment. The cultivation of Arabica, which represents 70% of consumed coffee, can also be accommodated in the future, but only by incurring some natural forest loss. This has corresponding implications for carbon storage, and is likely to affect areas currently designated as priority areas for biodiversity. Where Arabica coffee does encroach on natural forests, we project average local losses of 35% of threatened vertebrate species. The interaction of climate and coffee berry borer greatly influences projected outcomes. PMID:26177201

  18. Hydroregime prediction models for ephemeral groundwater-driven sinkhole wetlands: a planning tool for climate change and amphibian conservation

    Science.gov (United States)

    C. H. Greenberg; S. Goodrick; J. D. Austin; B. R. Parresol

    2015-01-01

    Hydroregimes of ephemeral wetlands affect reproductive success of many amphibian species and are sensitive to altered weather patterns associated with climate change.We used 17 years of weekly temperature, precipitation, and waterdepth measurements for eight small, ephemeral, groundwaterdriven sinkhole wetlands in Florida sandhills to develop a hydroregime predictive...

  19. Impact of value-driven scenarios on the geomorphology and ecology of lower Rhine floodplains under a changing climate

    NARCIS (Netherlands)

    Straatsma, M.W.; Schipper, A.; Perk, M. van der; Brink, N.G. van den; Leuven, R.S.E.W.; Middelkoop, H.

    2011-01-01

    In the future, the bio-geomorphological functioning of lowland floodplains is likely to be altered at an increasing pace. Together with increasing socio-economic demands, climatic changes are expected to increase the pressures on lowland rivers in developed countries. To cope with

  20. Climate-Driven or Human-Induced: Indicating Severe Water Scarcity in the Moulouya River Basin (Morocco

    Directory of Open Access Journals (Sweden)

    Vera Tekken

    2012-12-01

    Full Text Available Many agriculture-based economies are increasingly under stress from climate change and socio-economic pressures. The excessive exploitation of natural resources still represents the standard procedure to achieve socio-economic development. In the area of the Moulouya river basin, Morocco, natural water availability represents a key resource for all economic activities. Agriculture represents the most important sector, and frequently occurring water deficits are aggravated by climate change. On the basis of historical trends taken from CRU TS 2.1, this paper analyses the impact of climate change on the per capita water availability under inclusion of population trends. The Climatic Water Balance (CWB shows a significant decrease for the winter period, causing adverse effects for the main agricultural season. Further, moisture losses due to increasing evapotranspiration rates indicate problems for the annual water budget and groundwater recharge. The per capita blue water availability falls below a minimum threshold of 500 m3 per year, denoting a high regional vulnerability to increasing water scarcity assuming a no-response scenario. Regional development focusing on the water-intense sectors of agriculture and tourism appears to be at risk. Institutional capacities and policies need to address the problem, and the prompt implementation of innovative water production and efficiency measures is recommended.

  1. Long-term monitoring of an amphibian community after a climate change- and infectious disease-driven species extirpation.

    Science.gov (United States)

    Bosch, Jaime; Fernández-Beaskoetxea, Saioa; Garner, Trenton W J; Carrascal, Luis María

    2018-02-15

    Infectious disease and climate change are considered major threats to biodiversity and act as drivers behind the global amphibian decline. This is, to a large extent, based on short-term studies that are designed to detect the immediate and strongest biodiversity responses to a threatening process. What few long-term studies are available, although typically focused on single species, report outcomes that often diverge significantly from the short-term species responses. Here, we report the results of an 18-year survey of an amphibian community exposed to both climate warming and the emergence of lethal chytridiomycosis. Our study shows that the impacts of infectious disease are ongoing but restricted to two out of nine species that form the community, despite the fact all species can become infected with the fungus. Climate warming appears to be affecting four out of the nine species, but the response of three of these is an increase in abundance. Our study supports a decreasing role of infectious disease on the community, and an increasing and currently positive effect of climate warming. We caution that if the warming trends continue, the net positive effect will turn negative as amphibian breeding habitat becomes unavailable as water bodies dry, a pattern that already may be underway. © 2018 John Wiley & Sons Ltd.

  2. Data from: Testing models of speciation from genome sequences: divergence and asymmetric admixture in Island Southeast Asian Sus species during the Plio-Pleistocene climatic fluctuations

    NARCIS (Netherlands)

    Frantz, L.A.F.; Madsen, O.; Megens, H.J.W.C.; Groenen, M.; Lohse, H.

    2014-01-01

    In many temperate regions, ice ages promoted range contractions into refugia resulting in divergence (and potentially speciation), while warmer periods led to range expansions and hybridization. However, the impact these climatic oscillations had in many parts of the tropics remains elusive. Here,

  3. Testing models of speciation from genome sequences: divergence and asymmetric admixture in Island Southeast Asian Sus species during the Plio-Pleistocene climatic fluctuations

    NARCIS (Netherlands)

    Frantz, L.A.F.; Madsen, O.; Megens, H.J.W.C.; Groenen, M.; Lohse, H.

    2014-01-01

    In many temperate regions, ice ages promoted range contractions into refugia resulting in divergence (and potentially speciation), while warmer periods led to range expansions and hybridization. However, the impact these climatic oscillations had in many parts of the tropics remains elusive. Here,

  4. A vulnerability driven approach to identify adverse climate and land use change combinations for critical hydrologic indicator thresholds: Application to a watershed in Pennsylvania, USA

    Science.gov (United States)

    Singh, R.; Wagener, T.; Crane, R.; Mann, M. E.; Ning, L.

    2014-04-01

    Large uncertainties in streamflow projections derived from downscaled climate projections of precipitation and temperature can render such simulations of limited value for decision making in the context of water resources management. New approaches are being sought to provide decision makers with robust information in the face of such large uncertainties. We present an alternative approach that starts with the stakeholder's definition of vulnerable ranges for relevant hydrologic indicators. Then the modeled system is analyzed to assess under what conditions these thresholds are exceeded. The space of possible climates and land use combinations for a watershed is explored to isolate subspaces that lead to vulnerability, while considering model parameter uncertainty in the analysis. We implement this concept using classification and regression trees (CART) that separate the input space of climate and land use change into those combinations that lead to vulnerability and those that do not. We test our method in a Pennsylvania watershed for nine ecological and water resources related streamflow indicators for which an increase in temperature between 3°C and 6°C and change in precipitation between -17% and 19% is projected. Our approach provides several new insights, for example, we show that even small decreases in precipitation (˜5%) combined with temperature increases greater than 2.5°C can push the mean annual runoff into a slightly vulnerable regime. Using this impact and stakeholder driven strategy, we explore the decision-relevant space more fully and provide information to the decision maker even if climate change projections are ambiguous.

  5. Development of a database-driven system for simulating water temperature in the lower Yakima River main stem, Washington, for various climate scenarios

    Science.gov (United States)

    Voss, Frank; Maule, Alec

    2013-01-01

    A model for simulating daily maximum and mean water temperatures was developed by linking two existing models: one developed by the U.S. Geological Survey and one developed by the Bureau of Reclamation. The study area included the lower Yakima River main stem between the Roza Dam and West Richland, Washington. To automate execution of the labor-intensive models, a database-driven model automation program was developed to decrease operation costs, to reduce user error, and to provide the capability to perform simulations quickly for multiple management and climate change scenarios. Microsoft© SQL Server 2008 R2 Integration Services packages were developed to (1) integrate climate, flow, and stream geometry data from diverse sources (such as weather stations, a hydrologic model, and field measurements) into a single relational database; (2) programmatically generate heavily formatted model input files; (3) iteratively run water temperature simulations; (4) process simulation results for export to other models; and (5) create a database-driven infrastructure that facilitated experimentation with a variety of scenarios, node permutations, weather data, and hydrologic conditions while minimizing costs of running the model with various model configurations. As a proof-of-concept exercise, water temperatures were simulated for a "Current Conditions" scenario, where local weather data from 1980 through 2005 were used as input, and for "Plus 1" and "Plus 2" climate warming scenarios, where the average annual air temperatures used in the Current Conditions scenario were increased by 1degree Celsius (°C) and by 2°C, respectively. Average monthly mean daily water temperatures simulated for the Current Conditions scenario were compared to measured values at the Bureau of Reclamation Hydromet gage at Kiona, Washington, for 2002-05. Differences ranged between 1.9° and 1.1°C for February, March, May, and June, and were less than 0.8°C for the remaining months of the year

  6. The first millennium AD climate fluctuations in the Tavoliere Plain (Apulia, Italy): New preliminary data from the 14C AMS-dated plant remains from the archaeological site of Faragola

    International Nuclear Information System (INIS)

    Fiorentino, G.; Caracuta, V.; Volpe, G.; Turchiano, M.; Quarta, G.; D'Elia, M.; Calcagnile, L.

    2010-01-01

    The identification of ancient climate fluctuations represents an hard challenge for studies intended to outline the human-environment interaction in fragile ecosystems. The aim of this work is to test the potentialities of carbon stable isotopic content of AMS-dated archaeological plant remains as tool to infer variations in rainfall/temperature regimes. The results obtained in the analysis of the carbon stable isotopic content of 10 plant remains selected among the archaeobotanical remains collected at the archaeological site in Faragola (Apulia, Italy) and radiocarbon-dated by AMS are presented. The variation of δ 13 C values was considered on a chronological scale covering a time range comprised between the II century BC and the VII century AD. The obtained patterns were also compared with local and global-scale palaeoclimatic records.

  7. Control of fruit flies by sterile insect technique. I. Population fluctuation studies of oriental fruit fly (Dacus dorsalis Hendel and Dacus zonatus Saunders) and micro climates at Royal Ang Khang Highland Research Station Chiang Mai

    International Nuclear Information System (INIS)

    Chiravathanapong, S.

    1984-12-01

    The studies of population fluctuation of male oriental fruit fly, (Dacus dorsalis Hendel) and [Dacus zontanus (Saunders)] and micro climate at Royal Ang Khang Highland Research Station Chiang Mai in 1983 were conducted. It was found that population of Dacus zonatus was rather high and almost seemed equal to that of Dacus dorsalis. Population of these two species increased at the beginning of February. Population of Dacus zonatus increased rapidly and reached the peak in the middle of May and of June. The number at peaks were 103 males and 87 males/trap/day respectively. However, the population of Dacus dorsalis increased slowly and followed the pattern of Dacus zonatus until the beginning of June, after that, the population increased rapidly and reached the peak in the middle of July. The number at peak was 240 males/trap/day. Later on they dropped rapidly in the middle of August, then the population of the two species fluctuated together. Finally they decreased down to near zero in November, December and January of the following year. In summary, population density of the said two species adult flies were rather high from the end of winter (the beginning of February) to the middle of raining season (July) and this period coincided with the time of fruit development in many introduced varieties (peach, persimmon, apple, pear and plum)

  8. Scaling up nanoscale water-driven energy conversion into evaporation-driven engines and generators

    Science.gov (United States)

    Chen, Xi; Goodnight, Davis; Gao, Zhenghan; Cavusoglu, Ahmet H.; Sabharwal, Nina; Delay, Michael; Driks, Adam; Sahin, Ozgur

    2015-06-01

    Evaporation is a ubiquitous phenomenon in the natural environment and a dominant form of energy transfer in the Earth's climate. Engineered systems rarely, if ever, use evaporation as a source of energy, despite myriad examples of such adaptations in the biological world. Here, we report evaporation-driven engines that can power common tasks like locomotion and electricity generation. These engines start and run autonomously when placed at air-water interfaces. They generate rotary and piston-like linear motion using specially designed, biologically based artificial muscles responsive to moisture fluctuations. Using these engines, we demonstrate an electricity generator that rests on water while harvesting its evaporation to power a light source, and a miniature car (weighing 0.1 kg) that moves forward as the water in the car evaporates. Evaporation-driven engines may find applications in powering robotic systems, sensors, devices and machinery that function in the natural environment.

  9. The causality analysis of climate change and large-scale human crisis.

    Science.gov (United States)

    Zhang, David D; Lee, Harry F; Wang, Cong; Li, Baosheng; Pei, Qing; Zhang, Jane; An, Yulun

    2011-10-18

    Recent studies have shown strong temporal correlations between past climate changes and societal crises. However, the specific causal mechanisms underlying this relation have not been addressed. We explored quantitative responses of 14 fine-grained agro-ecological, socioeconomic, and demographic variables to climate fluctuations from A.D. 1500-1800 in Europe. Results show that cooling from A.D. 1560-1660 caused successive agro-ecological, socioeconomic, and demographic catastrophes, leading to the General Crisis of the Seventeenth Century. We identified a set of causal linkages between climate change and human crisis. Using temperature data and climate-driven economic variables, we simulated the alternation of defined "golden" and "dark" ages in Europe and the Northern Hemisphere during the past millennium. Our findings indicate that climate change was the ultimate cause, and climate-driven economic downturn was the direct cause, of large-scale human crises in preindustrial Europe and the Northern Hemisphere.

  10. Cheatgrass percent cover change: Comparing recent estimates to climate change − Driven predictions in the Northern Great Basin

    Science.gov (United States)

    Boyte, Stephen P.; Wylie, Bruce K.; Major, Donald J.

    2016-01-01

    Cheatgrass (Bromus tectorum L.) is a highly invasive species in the Northern Great Basin that helps decrease fire return intervals. Fire fragments the shrub steppe and reduces its capacity to provide forage for livestock and wildlife and habitat critical to sagebrush obligates. Of particular interest is the greater sage grouse (Centrocercus urophasianus), an obligate whose populations have declined so severely due, in part, to increases in cheatgrass and fires that it was considered for inclusion as an endangered species. Remote sensing technologies and satellite archives help scientists monitor terrestrial vegetation globally, including cheatgrass in the Northern Great Basin. Along with geospatial analysis and advanced spatial modeling, these data and technologies can identify areas susceptible to increased cheatgrass cover and compare these with greater sage grouse priority areas for conservation (PAC). Future climate models forecast a warmer and wetter climate for the Northern Great Basin, which likely will force changing cheatgrass dynamics. Therefore, we examine potential climate-caused changes to cheatgrass. Our results indicate that future cheatgrass percent cover will remain stable over more than 80% of the study area when compared with recent estimates, and higher overall cheatgrass cover will occur with slightly more spatial variability. The land area projected to increase or decrease in cheatgrass cover equals 18% and 1%, respectively, making an increase in fire disturbances in greater sage grouse habitat likely. Relative susceptibility measures, created by integrating cheatgrass percent cover and temporal standard deviation datasets, show that potential increases in future cheatgrass cover match future projections. This discovery indicates that some greater sage grouse PACs for conservation could be at heightened risk of fire disturbance. Multiple factors will affect future cheatgrass cover including changes in precipitation timing and totals and

  11. Predicting Monsoonal-Driven Stream Discharge and Sediment Yield in Himalaya Mountain Basins with Changing Climate and Deforestation

    Science.gov (United States)

    Neupane, R. P.; White, J. D.

    2014-12-01

    Short and long term effects of site water availability impacts the spectrum of management outcomes including landslide risk, hydropower generation, and sustainable agriculture in mountain systems heavily influenced by climate and land use changes. Climate change and land use may predominantly affect the hydrologic cycle of mountain basins as soil precipitation interception is affected by land cover. Using the Soil and Water Assessment Tool, we estimated stream discharge and sediment yield associated with climate and land use changes for two Himalaya basins located at eastern and western margins of Nepal that included drainages of the Tamor and Seti Rivers. Future climate change was modeled using average output of temperature and precipitation changes derived from Special Report on Emission Scenarios (B1, A1B & A2) of 16 global circulation models for 2080 as meteorological inputs into SWAT. Land use change was modeled spatially and included 1) deforestation, 2) expansion of agricultural land, and 3) increased human settlement that were produced by considering current land use with projected changes associated with viability of elevation and slope characteristics of the basins capable of supporting different land use types. We found higher annual stream discharge in all GCM-derived scenarios compared to the baseline with maximum increases of 13 and 8% in SRES-A2 and SRES-A1B for the Tamor and Seti basins, respectively. With 7% of original forest land removed, sediment yield for Tamor basin was estimated to be 65% higher, but increased to 124% for the SRES-B1 scenario. For the Seti basin, 4% deforestation yielded 33% more sediment for the SRES-A1B scenario. Our results indicated that combined effects of future, intensified monsoon rainfall with deforestation lead to dramatic potential for increased stream discharge and sediment yield as rainfall on steep slopes with thin exposed soils increases surface runoff and soil erosion in the Himalayas. This effect appears to

  12. Buoyancy-Driven Ventilation Generated by the Double-Skin Façade of a High-Rise Building in Tropical Climate: Case Study Bandung, Indonesia

    Directory of Open Access Journals (Sweden)

    Aziiz Akhlish Diinal

    2017-01-01

    Full Text Available High-rise buildings in tropical region is identical to the use of mechanical Air Conditioning in massive scale. Nevertheless, there is an encouragement to high-rise buildings to reduce its energy consumptions, since they consume quite large amount of energy. This challenge can be overcome with various of strategies, one of them, by means of reducing the cooling load of mechanical Air Conditioning in high-rise building. Prospects come from the modern tall building design strategies, for example the use of double-skin façade to give addition of building skin which could provide indoor temperature protection from outside. Double-skin façade system has continued to increase in buildings in a tropical region such as in Indonesia. However, there is another potential of double skin façade, which is the possibility to increase the buoyancy effect in the air gap between the skin and building envelope. The possibility needs to be studied in order to give a proper way in designing double-skin façade of a high-rise building, especially on Bandung-Indonesia tropical climate. This paper explores the potential of double-skin façade in driving the air inside the façade to generate natural ventilation for a high-rise building in Bandung climate condition. Two parameters are used in exploring the buoyancy force, the width of double-skin façade and the temperature of the skin façade. In general, double-skin façade of a high-rise building in tropical climate can generate buoyancy driven ventilation for the building, it relates strongly to the distance between of the double-skin façade and the building envelope.

  13. Change in the Green-Up Dates for Quercus mongolica in Northeast China and Its Climate-Driven Mechanism from 1962 to 2012.

    Science.gov (United States)

    Fan, Deqin; Zhu, Wenquan; Zheng, Zhoutao; Zhang, Donghai; Pan, Yaozhong; Jiang, Nan; Zhou, Xiafei

    2015-01-01

    The currently available studies on the green-up date were mainly based on ground observations and/or satellite data, and few model simulations integrated with wide coverage satellite data have been reported at large scale over a long time period (i.e., > 30 years). In this study, we combined phenology mechanism model, long-term climate data and synoptic scale remote sensing data to investigate the change in the green-up dates for Quercus mongolica over 33 weather stations in Northeast China and its climate-driven mechanism during 1962-2012. The results indicated that the unified phenology model can be well parameterized with the satellite derived green-up dates. The optimal daily mean temperature for chilling effect was between -27°C and 1°C for Q. mongolica in Northeast China, while the optimal daily mean temperature for forcing effect was above -3°C. The green-up dates for Q. mongolica across Northeast China showed a delayed latitudinal gradient of 2.699 days degree-1, with the earliest date on the Julian day 93 (i.e., 3th April) in the south and the latest date on the Julian day 129 (i.e., 9th May) in the north. The green-up date for Q. mongolica in Northeast China has advanced 6.6 days (1.3 days decade-1) from 1962 to 2012. With the prevailing warming in autumn, winter and spring in Northeast China during the past 51 years, the chilling effect for Q. mongolica has been weakened, while the forcing effect has been enhanced. The advancing trend in the green-up dates for Q. mongolica implied that the enhanced forcing effect to accelerate green-up was stronger than the weakened chilling effect to hold back green-up while the changes of both effects were caused by the warming climate.

  14. Change in the Green-Up Dates for Quercus mongolica in Northeast China and Its Climate-Driven Mechanism from 1962 to 2012.

    Directory of Open Access Journals (Sweden)

    Deqin Fan

    Full Text Available The currently available studies on the green-up date were mainly based on ground observations and/or satellite data, and few model simulations integrated with wide coverage satellite data have been reported at large scale over a long time period (i.e., > 30 years. In this study, we combined phenology mechanism model, long-term climate data and synoptic scale remote sensing data to investigate the change in the green-up dates for Quercus mongolica over 33 weather stations in Northeast China and its climate-driven mechanism during 1962-2012. The results indicated that the unified phenology model can be well parameterized with the satellite derived green-up dates. The optimal daily mean temperature for chilling effect was between -27°C and 1°C for Q. mongolica in Northeast China, while the optimal daily mean temperature for forcing effect was above -3°C. The green-up dates for Q. mongolica across Northeast China showed a delayed latitudinal gradient of 2.699 days degree-1, with the earliest date on the Julian day 93 (i.e., 3th April in the south and the latest date on the Julian day 129 (i.e., 9th May in the north. The green-up date for Q. mongolica in Northeast China has advanced 6.6 days (1.3 days decade-1 from 1962 to 2012. With the prevailing warming in autumn, winter and spring in Northeast China during the past 51 years, the chilling effect for Q. mongolica has been weakened, while the forcing effect has been enhanced. The advancing trend in the green-up dates for Q. mongolica implied that the enhanced forcing effect to accelerate green-up was stronger than the weakened chilling effect to hold back green-up while the changes of both effects were caused by the warming climate.

  15. Using a community-driven approach to identify local forest and climate change priorities in Teslin, Yukon

    Directory of Open Access Journals (Sweden)

    Joleen Timko

    2015-12-01

    Full Text Available The likelihood of addressing the complex environmental, economic, and social/cultural issues associated with local climate change impacts is enhanced when collaborative partnerships with local people are established. Using a community-centered approach in the Teslin region of Canada’s Yukon Territory, we utilized our research skills to respond to local needs for information by facilitating both an internal community process to clarify traditional and local knowledge, values, and perceptions on locally identified priorities, while gathering external information to enable local people to make sound decisions. Specifically, we sought to clarify local perceptions surrounding climate change impacts on fire risk and wildlife habitat, and the potential adaptation strategies appropriate and feasible within the Teslin Tlingit Traditional Territory. This paper provides a characterization of the study region and our project team; provides background on the interview and data collection process; presents our key results; and discusses the importance of our findings and charts a way forward for our continued work with the people in the Teslin region. This approach presents an excellent opportunity to help people holistically connect a range of local values, including fire risk mitigation, habitat enhancement, economic development, and enhanced social health.

  16. How will coral reef fish communities respond to climate-driven disturbances? Insight from landscape-scale perturbations.

    Science.gov (United States)

    Adam, Thomas C; Brooks, Andrew J; Holbrook, Sally J; Schmitt, Russell J; Washburn, Libe; Bernardi, Giacomo

    2014-09-01

    Global climate change is rapidly altering disturbance regimes in many ecosystems including coral reefs, yet the long-term impacts of these changes on ecosystem structure and function are difficult to predict. A major ecosystem service provided by coral reefs is the provisioning of physical habitat for other organisms, and consequently, many of the effects of climate change on coral reefs will be mediated by their impacts on habitat structure. Therefore, there is an urgent need to understand the independent and combined effects of coral mortality and loss of physical habitat on reef-associated biota. Here, we use a unique series of events affecting the coral reefs around the Pacific island of Moorea, French Polynesia to differentiate between the impacts of coral mortality and the degradation of physical habitat on the structure of reef fish communities. We found that, by removing large amounts of physical habitat, a tropical cyclone had larger impacts on reef fish communities than an outbreak of coral-eating sea stars that caused widespread coral mortality but left the physical structure intact. In addition, the impacts of declining structural complexity on reef fish assemblages accelerated as structure became increasingly rare. Structure provided by dead coral colonies can take up to decades to erode following coral mortality, and, consequently, our results suggest that predictions based on short-term studies are likely to grossly underestimate the long-term impacts of coral decline on reef fish communities.

  17. Eutrophication and warming-driven green tides (Ulva rigida) are predicted to increase under future climate change scenarios.

    Science.gov (United States)

    Gao, Guang; Clare, Anthony S; Rose, Craig; Caldwell, Gary S

    2017-01-15

    The incidence and severity of extraordinary macroalgae blooms (green tides) are increasing. Here, climate change (ocean warming and acidification) impacts on life history and biochemical responses of a causative green tide species, Ulva rigida, were investigated under combinations of pH (7.95, 7.55, corresponding to lower and higher pCO 2 ), temperature (14, 18°C) and nitrate availability (6 and 150μmolL -1 ). The higher temperature accelerated the onset and magnitude of gamete settlement. Any two factor combination promoted germination and accelerated growth in young plants. The higher temperature increased reproduction, which increased further in combination with elevated pCO 2 or nitrate. Reproductive success was highest (64.4±5.1%) when the upper limits of all three variables were combined. Biochemically, more protein and lipid but less carbohydrate were synthesized under higher temperature and nitrate conditions. These results suggest that climate change may cause more severe green tides, particularly when eutrophication cannot be effectively controlled. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Charge Fluctuations in Nanoscale Capacitors

    Science.gov (United States)

    Limmer, David T.; Merlet, Céline; Salanne, Mathieu; Chandler, David; Madden, Paul A.; van Roij, René; Rotenberg, Benjamin

    2013-09-01

    The fluctuations of the charge on an electrode contain information on the microscopic correlations within the adjacent fluid and their effect on the electronic properties of the interface. We investigate these fluctuations using molecular dynamics simulations in a constant-potential ensemble with histogram reweighting techniques. This approach offers, in particular, an efficient, accurate, and physically insightful route to the differential capacitance that is broadly applicable. We demonstrate these methods with three different capacitors: pure water between platinum electrodes and a pure as well as a solvent-based organic electrolyte each between graphite electrodes. The total charge distributions with the pure solvent and solvent-based electrolytes are remarkably Gaussian, while in the pure ionic liquid the total charge distribution displays distinct non-Gaussian features, suggesting significant potential-driven changes in the organization of the interfacial fluid.

  19. Charge fluctuations in nanoscale capacitors.

    Science.gov (United States)

    Limmer, David T; Merlet, Céline; Salanne, Mathieu; Chandler, David; Madden, Paul A; van Roij, René; Rotenberg, Benjamin

    2013-09-06

    The fluctuations of the charge on an electrode contain information on the microscopic correlations within the adjacent fluid and their effect on the electronic properties of the interface. We investigate these fluctuations using molecular dynamics simulations in a constant-potential ensemble with histogram reweighting techniques. This approach offers, in particular, an efficient, accurate, and physically insightful route to the differential capacitance that is broadly applicable. We demonstrate these methods with three different capacitors: pure water between platinum electrodes and a pure as well as a solvent-based organic electrolyte each between graphite electrodes. The total charge distributions with the pure solvent and solvent-based electrolytes are remarkably Gaussian, while in the pure ionic liquid the total charge distribution displays distinct non-Gaussian features, suggesting significant potential-driven changes in the organization of the interfacial fluid.

  20. Fluctuation theorems and atypical trajectories

    International Nuclear Information System (INIS)

    Sahoo, M; Lahiri, S; Jayannavar, A M

    2011-01-01

    In this work, we have studied simple models that can be solved analytically to illustrate various fluctuation theorems. These fluctuation theorems provide symmetries individually to the distributions of physical quantities such as the classical work (W c ), thermodynamic work (W), total entropy (Δs tot ) and dissipated heat (Q), when the system is driven arbitrarily out of equilibrium. All these quantities can be defined for individual trajectories. We have studied the number of trajectories which exhibit behaviour unexpected at the macroscopic level. As the time of observation increases, the fraction of such atypical trajectories decreases, as expected at the macroscale. The distributions for the thermodynamic work and entropy production in nonlinear models may exhibit a peak (most probable value) in the atypical regime without violating the expected average behaviour. However, dissipated heat and classical work exhibit a peak in the regime of typical behaviour only.

  1. Effects of geological changes and climatic fluctuations on the demographic histories and low genetic diversity of Squaliobarbus curriculus in Yellow River.

    Science.gov (United States)

    Zhou, Wei; Song, Na; Wang, Jun; Gao, Tianxiang

    2016-09-15

    The 104 samples of Squaliobarbus curriculus were collected from four localities in Yellow River and one region in Yangtze River. Analyses of the first hypervariable region of mitochondrial DNA control region of 555bp revealed only 15 polymorphism sites and defined 19 haplotypes. Low-to-moderate levels of haplotype diversity and low nucleotide diversity were observed in Yellow River populations (h=0.2529-0.7510, π=0.0712%-0.2197%). In contrast, Poyang Lake population showed high haplotype diversity and lower-middle nucleotide diversity (h=0.9636, π=0.5317%). Low genetic differentiation was estimated among Yellow River populations and significant level of genetic structure was detected between two rivers. Population genetic structure between two rivers was believed to be connected with geographical barriers and paleoclimatic events. The demographic history of S. curriculus in Yellow River examined by neutrality tests, mismatch distribution analysis, and Bayesian skyline analysis suggested a sudden and spatial population expansion dating to the Holocene. Climatic warming and changes of Yellow River course may have important effects on demographic facet of S. curriculus history. The same signal was also obtained on Poyang Lake population in late Pleistocene during the last interglacial period. During the period, the pronounced climatic change and the water system variation of PYL may have an important influence on the population. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Comment on "Astronomical constraints on the duration of the Early Jurassic Pliensbachian Stage and global climatic fluctuations" [Earth Planet. Sci. Lett. 455 (2016) 149-165

    Science.gov (United States)

    Smith, David G.; Bailey, Robin J.

    2018-01-01

    Astrochronology employs spectral analysis of stratigraphic data series to substantiate and quantify depositional cyclicity, and thus to establish a probable causal link between cases of rhythmic bedding and periodic orbitally-forced climate change. Vaughan et al. (2011 - not cited by Ruhl et al.) showed that the spectral methods conventionally used in cyclostratigraphy will generate false positive results - they will identify multiple cycles that are not present in the data. Tests with synthetic random datasets are both a simple and an essential way to prove this. Ruhl et al. (2016) used the methods to which these criticisms apply in their analysis of XRF-compositional data series from the Early Jurassic of the Mochras borehole, Wales. We use properly corrected methods to re-examine some of their data, showing that their spectral results are not valid, thus casting doubt on their proposed calibration of Pliensbachian time.

  3. An analytical model for climatic predictions

    International Nuclear Information System (INIS)

    Njau, E.C.

    1990-12-01

    A climatic model based upon analytical expressions is presented. This model is capable of making long-range predictions of heat energy variations on regional or global scales. These variations can then be transformed into corresponding variations of some other key climatic parameters since weather and climatic changes are basically driven by differential heating and cooling around the earth. On the basis of the mathematical expressions upon which the model is based, it is shown that the global heat energy structure (and hence the associated climatic system) are characterized by zonally as well as latitudinally propagating fluctuations at frequencies downward of 0.5 day -1 . We have calculated the propagation speeds for those particular frequencies that are well documented in the literature. The calculated speeds are in excellent agreement with the measured speeds. (author). 13 refs

  4. Phenological shifts conserve thermal niches in North American birds and reshape expectations for climate-driven range shifts.

    Science.gov (United States)

    Socolar, Jacob B; Epanchin, Peter N; Beissinger, Steven R; Tingley, Morgan W

    2017-12-05

    Species respond to climate change in two dominant ways: range shifts in latitude or elevation and phenological shifts of life-history events. Range shifts are widely viewed as the principal mechanism for thermal niche tracking, and phenological shifts in birds and other consumers are widely understood as the principal mechanism for tracking temporal peaks in biotic resources. However, phenological and range shifts each present simultaneous opportunities for temperature and resource tracking, although the possible role for phenological shifts in thermal niche tracking has been widely overlooked. Using a canonical dataset of Californian bird surveys and a detectability-based approach for quantifying phenological signal, we show that Californian bird communities advanced their breeding phenology by 5-12 d over the last century. This phenological shift might track shifting resource peaks, but it also reduces average temperatures during nesting by over 1 °C, approximately the same magnitude that average temperatures have warmed over the same period. We further show that early-summer temperature anomalies are correlated with nest success in a continental-scale database of bird nests, suggesting avian thermal niches might be broadly limited by temperatures during nesting. These findings outline an adaptation surface where geographic range and breeding phenology respond jointly to constraints imposed by temperature and resource phenology. By stabilizing temperatures during nesting, phenological shifts might mitigate the need for range shifts. Global change ecology will benefit from further exploring phenological adjustment as a potential mechanism for thermal niche tracking and vice versa.

  5. Demographically idiosyncratic responses to climate change and rapid Pleistocene diversification of the walnut genus Juglans (Juglandaceae) revealed by whole-genome sequences

    Science.gov (United States)

    Wei-Ning Bai; Peng-Cheng Yan; Bo-Wen Zhang; Keith E. Woeste; Kui Lin; Da-Yong. Zhang

    2018-01-01

    Whether species demography and diversification are driven primarily by extrinsic environmental changes such as climatic oscillations in the Quaternary or by intrinsic biological interactions like coevolution between antagonists is a matter of active debate. In fact, their relative importance can be assessed by tracking past population fluctuations over considerable...

  6. Evaluating and Quantifying the Climate-Driven Interannual Variability in Global Inventory Modeling and Mapping Studies (GIMMS) Normalized Difference Vegetation Index (NDVI3g) at Global Scales

    Science.gov (United States)

    Zeng, Fanwei; Collatz, George James; Pinzon, Jorge E.; Ivanoff, Alvaro

    2013-01-01

    Satellite observations of surface reflected solar radiation contain informationabout variability in the absorption of solar radiation by vegetation. Understanding thecauses of variability is important for models that use these data to drive land surface fluxesor for benchmarking prognostic vegetation models. Here we evaluated the interannualvariability in the new 30.5-year long global satellite-derived surface reflectance index data,Global Inventory Modeling and Mapping Studies normalized difference vegetation index(GIMMS NDVI3g). Pearsons correlation and multiple linear stepwise regression analyseswere applied to quantify the NDVI interannual variability driven by climate anomalies, andto evaluate the effects of potential interference (snow, aerosols and clouds) on the NDVIsignal. We found ecologically plausible strong controls on NDVI variability by antecedent precipitation and current monthly temperature with distinct spatial patterns. Precipitation correlations were strongest for temperate to tropical water limited herbaceous systemswhere in some regions and seasons 40 of the NDVI variance could be explained byprecipitation anomalies. Temperature correlations were strongest in northern mid- to-high-latitudes in the spring and early summer where up to 70 of the NDVI variance was explained by temperature anomalies. We find that, in western and central North America,winter-spring precipitation determines early summer growth while more recent precipitation controls NDVI variability in late summer. In contrast, current or prior wetseason precipitation anomalies were correlated with all months of NDVI in sub-tropical herbaceous vegetation. Snow, aerosols and clouds as well as unexplained phenomena still account for part of the NDVI variance despite corrections. Nevertheless, this study demonstrates that GIMMS NDVI3g represents real responses of vegetation to climate variability that are useful for global models.

  7. Fluctuations and Photons

    International Nuclear Information System (INIS)

    Gupta, Sourendu

    2007-01-01

    In this talk I discuss measures of fluctuations, especially those leading to the proof that the quark gluon plasma indeed contains quarks. I discuss the quark mass dependence of the critical end point of QCD. Then I discuss probes of the QCD critical point. Non-gaussian behaviour of event-to-event fluctuations of conserved quantum numbers is one such probe. Another is due to the coupling of fluctuations in baryon number and electrical charge, giving rise to long range random fluctuations of local charge density which relax slowly. These fluctuations can scatter photons, giving rise to critical opalescence

  8. Fluctuations and Photons

    Science.gov (United States)

    Gupta, Sourendu

    2007-02-01

    In this talk I discuss measures of fluctuations, especially those leading to the proof that the quark gluon plasma indeed contains quarks. I discuss the quark mass dependence of the critical end point of QCD. Then I discuss probes of the QCD critical point. Non-gaussian behaviour of event-to-event fluctuations of conserved quantum numbers is one such probe. Another is due to the coupling of fluctuations in baryon number and electrical charge, giving rise to long range random fluctuations of local charge density which relax slowly. These fluctuations can scatter photons, giving rise to critical opalescence.

  9. Fluctuations and Photons

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Sourendu [Department of Theoretical Physics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India)

    2007-02-15

    In this talk I discuss measures of fluctuations, especially those leading to the proof that the quark gluon plasma indeed contains quarks. I discuss the quark mass dependence of the critical end point of QCD. Then I discuss probes of the QCD critical point. Non-gaussian behaviour of event-to-event fluctuations of conserved quantum numbers is one such probe. Another is due to the coupling of fluctuations in baryon number and electrical charge, giving rise to long range random fluctuations of local charge density which relax slowly. These fluctuations can scatter photons, giving rise to critical opalescence.

  10. Quantum Fluctuations of Low Dimensional Bose-Einstein ...

    African Journals Online (AJOL)

    A system of low dimensional condensed ultracold atomic gases inside a field of a laser-driven optical cavity exhibits dispersive optical bistability. During such a process the system also shows quantum fluctuations. Condensate fluctuations are highly manifested particularly in low dimensional systems. In this paper we have ...

  11. The Effect of Pleistocene Climate Fluctuations on Distribution of European Abalone (Haliotis tuberculata), Revealed by Combined Mitochondrial and Nuclear Marker Analyses.

    Science.gov (United States)

    Roussel, Valérie; Van Wormhoudt, Alain

    2017-04-01

    The genetic differentiation among the populations of the European abalone Haliotis tuberculata was investigated using different markers to better understand the evolutionary history and exchanges between populations. Three markers were used: mitochondrial cytochrome oxidase I (COI), the sperm lysin nuclear gene, and eight nuclear microsatellites. These markers present different characteristics concerning mutation rate and inheritance, which provided complementary information about abalone history and gene diversity. Genetic diversity and relationships among subspecies were calculated from a sample of approximately 500 individuals, collected from 17 different locations in the north-eastern Atlantic Ocean, Macaronesia, and Mediterranean Sea. COI marker was used to explore the phylogeny of the species with a network analysis and two phylogenetic methods. The analysis revealed 18 major haplotypes grouped into two distinct clades with a pairwise sequence divergence up to 3.5 %. These clades do not correspond to subspecies but revealed many contacts along Atlantic coast during the Pleistocene interglaciations. The sperm lysin gene analysis separated two different subtaxa: one associated to Macaronesian islands, and the other to all other populations. Moreover, a small population of the northern subtaxon was isolated in the Adriatic Sea-probably before the separation of the two lineages-and evolved independently. Microsatellites were analyzed by different genetics methods, including the Bayesian clustering method and migration patterns analysis. It revealed genetically distinct microsatellite patterns among populations from Mediterranean Sea, Brittany and Normandy, Morocco, and Canary and Balearic islands. Gene flow is asymmetric among the regions; the Azores and the Canary Islands are particularly isolated and have low effective population sizes. Our results support the hypothesis that climate changes since the Pleistocene glaciations have played a major role in the

  12. The Water Level Fall of Lake Megali Prespa (N Greece): an Indicator of Regional Water Stress Driven by Climate Change and Amplified by Water Extraction?

    Science.gov (United States)

    van der Schriek, Tim; Giannakopoulos, Christos

    2014-05-01

    The Mediterranean stands out globally due to its sensitivity to (future) climate change, with future projections predicting an increase in excessive drought events and declining rainfall. Regional freshwater ecosystems are particularly threatened: precipitation decreases, while extreme droughts increase and human impacts intensify (e.g. water extraction, drainage, pollution and dam-building). Many Mediterranean lake-wetland systems have shrunk or disappeared over the past two decades. Protecting the remaining systems is extremely important for supporting global biodiversity and for ensuring sustainable water availability. This protection should be based on a clear understanding of lake-wetland hydrological responses to natural and human-induced changes, which is currently lacking in many parts of the Mediterranean. The interconnected Prespa-Ohrid Lake system is a global hotspot of biodiversity and endemism. The unprecedented fall in water level (~8m) of Lake Megali Prespa threatens this system, but causes remain debated. Modelling suggests that the S Balkan will experience rainfall and runoff decreases of ~30% by 2050. However, projections revealing the potential impact of these changes on future lake level are unavailable as lake regime is not understood. A further drop in lake level may have serious consequences. The Prespa Lakes contribute ~25% of the total inflow into Lake Ohrid through underground karst channels; falling lake levels decrease this discharge. Lake Ohrid, in turn, feeds the Drim River. This entire catchment may therefore be affected by falling lake levels; its water resources are of great importance for Greece, Albania, FYROM and Montenegro (e.g. tourism, agriculture, hydro-energy, urban & industrial use). This new work proves that annual water level fluctuations of Lake Megali Prespa are predominantly related to precipitation during the first 7 months (Oct-Apr) of the hydrological year (Oct-Sep). Lake level is very sensitive to regional and

  13. Interaction of the fluctuation of the population density of sweet potato pests with changes in farming practices, climate and physical environments: A 11-year preliminary observation from South-Kivu Province, Eastern DRCongo

    Directory of Open Access Journals (Sweden)

    Munyuli Théodore

    2017-10-01

    spp. or as vectors of diseases (Bemisi tabaci, Aphis spp.. The results indicated a high fluctuation in the population density of different pests. The change in the population dynamics were characterized by gradual increase in the populations during rainy seasons followed by decline during dry seasons (hot months of the year. Significant (P<0.05 differences were observed in the population dynamics between sole sweetpotato and mixed sweetpotato intercropping. There was a synchronization of multiple pest generations (biannual, multiannual cycles of reproduction built up with early rains. The results indicate that rainfall and maximum temperature were critical to the survival and population built up of the pest population. High rainfall in the previous months caused increases in the population density in the subsequent months within a year. The population dynamic (seasonal occurrence over months and years was likely to coincide with favorable feeding and breeding conditions available within sweetpotato biotopes when temperatures were sufficiently high or after heavy rainfall. For some species, maximum temperature and dry seasons were associated with declines in the pest populations whereas for other species, heavy rainfall was associated with subsequent outbreaks (high populations in the following months of the years. It is likely that perturbations in temperature/ rainfall patterns may cause serious changes in the pest population, therefore favoring the build-up of multiple generations within a year, thus. Rainfall and maximum temperatures were reliable predictors of key pest species. In fact, regressions analyses indicated that there were significant relationships (P<0.01 between the fluctuation of the population density of different pest species and the variability of climatic factors (mean monthly maximum/ minimum temperature, average rainfall. The population density of different insect pest species varied according to cropping system and to altitude. For example, a

  14. Fluctuating Asymmetry of Human Populations: A Review

    Directory of Open Access Journals (Sweden)

    John H. Graham

    2016-12-01

    Full Text Available Fluctuating asymmetry, the random deviation from perfect symmetry, is a widely used population-level index of developmental instability, developmental noise, and robustness. It reflects a population’s state of adaptation and genomic coadaptation. Here, we review the literature on fluctuating asymmetry of human populations. The most widely used bilateral traits include skeletal, dental, and facial dimensions; dermatoglyphic patterns and ridge counts; and facial shape. Each trait has its advantages and disadvantages, but results are most robust when multiple traits are combined into a composite index of fluctuating asymmetry (CFA. Both environmental (diet, climate, toxins and genetic (aneuploidy, heterozygosity, inbreeding stressors have been linked to population-level variation in fluctuating asymmetry. In general, these stressors increase average fluctuating asymmetry. Nevertheless, there have been many conflicting results, in part because (1 fluctuating asymmetry is a weak signal in a sea of noise; and (2 studies of human fluctuating asymmetry have not always followed best practices. The most serious concerns are insensitive asymmetry indices (correlation coefficient and coefficient of indetermination, inappropriate size scaling, unrecognized mixture distributions, inappropriate corrections for directional asymmetry, failure to use composite indices, and inattention to measurement error. Consequently, it is often difficult (or impossible to compare results across traits, and across studies.

  15. Climate-driven mathematical models to understand the spatio-temporal heterogeneity of a chikungunya outbreak in the presence of widespread asymptomatic infection

    Science.gov (United States)

    Dommar, Carlos J.; Robinson, Marguerite; Lowe, Rachel; Conan, Anne; Buchy, Philippe; Tarantola, Arnaud; Rodó, Xavier

    2014-05-01

    The emergence and persistence of human pathogens in the environment represents a constant threat to society, with global implications for human health, economies and ecosystems. Of particular concern are vector-borne diseases, such as dengue, malaria and chikungunya, which are increasing across their traditional ranges and continuing to infiltrate new regions. This unprecedented situation has been partly attributed to the increase in global temperatures in recent decades which has allowed non-native mosquito species to invade and successfully colonise previously inhospitable environments. The spatio-temporal evolution of these diseases is determined by the interaction of the host and vector, which is strongly dependent on social structures and mobility patterns. In turn, vector populations are thought to be driven by external environmental variables, such as precipitation and temperature. Furthermore, the ability of asymptomatic individuals to successfully transmit the infection and evade control measures can undermine public health interventions. We employed a stochastic model, which explicitly included asymptomatic and undocumented laboratory confirmed cases, and applied it to a documented outbreak in Cambodia in 2012 (Trapeang Roka village, Kampong Speu Province). The resulting estimate of the reproduction number was considerably higher than values obtained for previous outbreaks and highlights the importance of asymptomatic transmission. Subsequently, we develop an agent-based model (ABM), in which each individual is explicitly represented and vector populations are linked to precipitation estimates in a tropical setting. The model is implemented on both scale-free and regular networks. The spatio-temporal transmission of chikungunya is analysed and the presence of asymptomatic silent spreaders within the population is investigated in the context of implementing travel restrictions during an outbreak. Preventing the movement of symptomatic individuals alone is

  16. Event-by-Event Elliptic Flow Fluctuations from PHOBOS

    Science.gov (United States)

    Wosiek, B.; Alver, B.; Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Betts, R. R.; Bickley, A. A.; Bindel, R.; Busza, W.; Carroll, A.; Chai, Z.; Chetluru, V.; Decowski, M. P.; García, E.; Gburek, T.; George, N.; Gulbrandsen, K.; Halliwell, C.; Hamblen, J.; Harnarine, I.; Hauer, M.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Hołyński, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Khan, N.; Kulinich, P.; Kuo, C. M.; Li, W.; Lin, W. T.; Loizides, C.; Manly, S.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Reed, C.; Richardson, E.; Roland, C.; Roland, G.; Sagerer, J.; Seals, H.; Sedykh, I.; Smith, C. E.; Stankiewicz, M. A.; Steinberg, P.; Stephans, G. S. F.; Sukhanov, A.; Szostak, A.; Tonjes, M. B.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Vaurynovich, S. S.; Verdier, R.; Veres, G. I.; Walters, P.; Wenger, E.; Willhelm, D.; Wolfs, F. L. H.; Woźniak, K.; Wyngaardt, S.; Wysłouch, B.

    2009-04-01

    Recently PHOBOS has focused on the study of fluctuations and correlations in particle production in heavy-ion collisions at the highest energies delivered by the Relativistic Heavy Ion Collider (RHIC). In this report, we present results on event-by-event elliptic flow fluctuations in (Au+Au) collisions at sqrt {sNN}=200 GeV. A data-driven method was used to estimate the dominant contribution from non-flow correlations. Over the broad range of collision centralities, the observed large elliptic flow fluctuations are in agreement with the fluctuations in the initial source eccentricity.

  17. Belowground Plant–Herbivore Interactions Vary among Climate-Driven Range-Expanding Plant Species with Different Degrees of Novel Chemistry

    Directory of Open Access Journals (Sweden)

    Rutger A. Wilschut

    2017-10-01

    Full Text Available An increasing number of studies report plant range expansions to higher latitudes and altitudes in response to global warming. However, consequences for interactions with other species in the novel ranges are poorly understood. Here, we examine how range-expanding plant species interact with root-feeding nematodes from the new range. Root-feeding nematodes are ubiquitous belowground herbivores that may impact the structure and composition of natural vegetation. Because of their ecological novelty, we hypothesized that range-expanding plant species will be less suitable hosts for root-feeding nematodes than native congeneric plant species. In greenhouse and lab trials we compared nematode preference and performance of two root-feeding nematode species between range-expanding plant species and their congeneric natives. In order to understand differences in nematode preferences, we compared root volatile profiles of all range-expanders and congeneric natives. Nematode preferences and performances differed substantially among the pairs of range-expanders and natives. The range-expander that had the most unique volatile profile compared to its related native was unattractive and a poor host for nematodes. Other range-expanding plant species that differed less in root chemistry from native congeners, also differed less in nematode attraction and performance. We conclude that the three climate-driven range-expanding plant species studied varied considerably in their chemical novelty compared to their congeneric natives, and therefore affected native root-feeding nematodes in species-specific ways. Our data suggest that through variation in chemical novelty, range-expanding plant species may vary in their impacts on belowground herbivores in the new range.

  18. Superconductivity and spin fluctuations

    International Nuclear Information System (INIS)

    Scalapino, D.J.

    1999-01-01

    The organizers of the Memorial Session for Herman Rietschel asked that the author review some of the history of the interplay of superconductivity and spin fluctuations. Initially, Berk and Schrieffer showed how paramagnon spin fluctuations could suppress superconductivity in nearly-ferromagnetic materials. Following this, Rietschel and various co-workers wrote a number of papers in which they investigated the role of spin fluctuations in reducing the Tc of various electron-phonon superconductors. Paramagnon spin fluctuations are also believed to provide the p-wave pairing mechanism responsible for the superfluid phases of 3 He. More recently, antiferromagnetic spin fluctuations have been proposed as the mechanism for d-wave pairing in the heavy-fermion superconductors and in some organic materials as well as possibly the high-Tc cuprates. Here the author will review some of this early history and discuss some of the things he has learned more recently from numerical simulations

  19. Evaluating the Sensitivity of Agricultural Model Performance to Different Climate Inputs: Supplemental Material

    Science.gov (United States)

    Glotter, Michael J.; Ruane, Alex C.; Moyer, Elisabeth J.; Elliott, Joshua W.

    2015-01-01

    Projections of future food production necessarily rely on models, which must themselves be validated through historical assessments comparing modeled and observed yields. Reliable historical validation requires both accurate agricultural models and accurate climate inputs. Problems with either may compromise the validation exercise. Previous studies have compared the effects of different climate inputs on agricultural projections but either incompletely or without a ground truth of observed yields that would allow distinguishing errors due to climate inputs from those intrinsic to the crop model. This study is a systematic evaluation of the reliability of a widely used crop model for simulating U.S. maize yields when driven by multiple observational data products. The parallelized Decision Support System for Agrotechnology Transfer (pDSSAT) is driven with climate inputs from multiple sources reanalysis, reanalysis that is bias corrected with observed climate, and a control dataset and compared with observed historical yields. The simulations show that model output is more accurate when driven by any observation-based precipitation product than when driven by non-bias-corrected reanalysis. The simulations also suggest, in contrast to previous studies, that biased precipitation distribution is significant for yields only in arid regions. Some issues persist for all choices of climate inputs: crop yields appear to be oversensitive to precipitation fluctuations but under sensitive to floods and heat waves. These results suggest that the most important issue for agricultural projections may be not climate inputs but structural limitations in the crop models themselves.

  20. Hadronic Correlations and Fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Koch, Volker

    2008-10-09

    We will provide a review of some of the physics which can be addressed by studying fluctuations and correlations in heavy ion collisions. We will discuss Lattice QCD results on fluctuations and correlations and will put them into context with observables which have been measured in heavy-ion collisions. Special attention will be given to the QCD critical point and the first order co-existence region, and we will discuss how the measurement of fluctuations and correlations can help in an experimental search for non-trivial structures in the QCD phase diagram.

  1. Quantum fluctuations and inflation

    International Nuclear Information System (INIS)

    Bardeen, J.M.; Bublik, G.J.

    1986-05-01

    We study the effect of quantum fluctuations on the roll-down rate of the inflation field in a semiclassical approximation; this is done by treating the inflation field as a classical random field. The quantum fluctuations are simulated by a noise term in the equation of motion. We consider two different inflationary scenarios (new and chaotic inflation) and find that the roll-down rate of the median value of the inflation field is increased by the quantum fluctuations. Non-linear effects may become important in the later stages of the inflationary regime. 8 refs., 2 figs

  2. Quantum fluctuations and inflation

    International Nuclear Information System (INIS)

    Bardeen, J.M.; Bublik, G.J.

    1987-01-01

    The authors study the effect of quantum fluctuations on the roll-down rate of the inflation field in a semiclassical approximation; this is done by treating the inflation field as a classical random field. The quantum fluctuations are simulated by a noise term in the equation of motion. Two different inflationary scenarios (new and chaotic inflation) are considered and it is found that the roll-down rate of the median value of the inflation field is increased by the quantum fluctuations. Non-linear effects may become important in the later stages of the inflationary regime. (author)

  3. Universal bounds on current fluctuations.

    Science.gov (United States)

    Pietzonka, Patrick; Barato, Andre C; Seifert, Udo

    2016-05-01

    For current fluctuations in nonequilibrium steady states of Markovian processes, we derive four different universal bounds valid beyond the Gaussian regime. Different variants of these bounds apply to either the entropy change or any individual current, e.g., the rate of substrate consumption in a chemical reaction or the electron current in an electronic device. The bounds vary with respect to their degree of universality and tightness. A universal parabolic bound on the generating function of an arbitrary current depends solely on the average entropy production. A second, stronger bound requires knowledge both of the thermodynamic forces that drive the system and of the topology of the network of states. These two bounds are conjectures based on extensive numerics. An exponential bound that depends only on the average entropy production and the average number of transitions per time is rigorously proved. This bound has no obvious relation to the parabolic bound but it is typically tighter further away from equilibrium. An asymptotic bound that depends on the specific transition rates and becomes tight for large fluctuations is also derived. This bound allows for the prediction of the asymptotic growth of the generating function. Even though our results are restricted to networks with a finite number of states, we show that the parabolic bound is also valid for three paradigmatic examples of driven diffusive systems for which the generating function can be calculated using the additivity principle. Our bounds provide a general class of constraints for nonequilibrium systems.

  4. Fluorescence fluctuation spectroscopy (FFS)

    CERN Document Server

    Tetin, Sergey

    2012-01-01

    This new volume of Methods in Enzymology continues the legacy of this premier serial with quality chapters authored by leaders in the field. This volume covers fluorescence fluctuation spectroscopy and includes chapters on such topics as Förster resonance energy transfer (fret) with fluctuation algorithms, protein corona on nanoparticles by FCS, and FFS approaches to the study of receptors in live cells. Continues the legacy of this premier serial with quality chapters authored by leaders in the field Covers fluorescence fluctuation spectroscopy Contains chapters on such topics as Förster resonance energy transfer (fret) with fluctuation algorithms, protein corona on nanoparticles by FCS, and FFS approaches to the study of receptors in live cells.

  5. Magnetic fluctuation measurements in the Tokapole II tokamak

    International Nuclear Information System (INIS)

    LaPointe, M.A.

    1990-09-01

    Magnetic fluctuation measurements have been made in the Tokapole II tokamak in the frequency range 10 kHz ≤ f ≤ 5 MHz. The fluctuations above 500 kHz varied greatly as the effective edge safety factor, q a , was varied over the range 0.8 ≤ q a ≤ 3.8. As q a was varied from 3.8 to 0.8 the high frequency magnetic fluctuation amplitude increased by over three orders of magnitude. The fluctuation amplitude for 0.5 to 2.0 MHz was a factor of 10 lower than the fluctuation amplitude in the range 100 to 400 kHz for q a of 0.8. When q a was increased to 3.8 the difference between the differing frequency ranges increased to a factor of 10 3 . Comparison of the measured broadband fluctuation amplitudes with those predicted from thermally driven Alfven and magnetosonic waves shows that the amplitudes are at least 1000 times larger than the theoretical predictions. This indicates that there is some other mechanism driving the higher frequency magnetic fluctuations. Estimates show that the contribution by the magnetic fluctuations above 500 kHz to the estimated electron energy loss from stochastic fields is negligible. The profiles of the various components of the magnetic fluctuations indicate the possibility that the shear in the magnetic field may stabilize whatever instabilities drive the magnetic fluctuations

  6. Quantum work fluctuation theorem: Nonergodic Brownian motion case

    International Nuclear Information System (INIS)

    Bai, Zhan-Wu

    2014-01-01

    The work fluctuations of a quantum Brownian particle driven by an external force in a general nonergodic heat bath are studied under a general initial state. The exact analytical expression of the work probability distribution function is derived. Results show the existence of a quantum asymptotic fluctuation theorem, which is in general not a direct generalization of its classical counterpart. The form of this theorem is dependent on the structure of the heat bath and the specified initial condition.

  7. Theoretical studies on rapid fluctuations in solar flares

    International Nuclear Information System (INIS)

    Vlahos, L.

    1986-01-01

    Rapid fluctuations in the emission of solar bursts may have many different origins, e.g., the acceleration process can have a pulsating structure, the propagation of energetic electrons and ions can be interrupted from plasma instabilities and finally the electromagnetic radiation produced by the interaction of electrostatic and electromagnetic waves may have a pulsating behavior in time. In two separate studies the conditions for rapid fluctuations in solar flare driven emission were analyzed

  8. Theoretical studies on rapid fluctuations in solar flares

    Science.gov (United States)

    Vlahos, Loukas

    1986-01-01

    Rapid fluctuations in the emission of solar bursts may have many different origins e.g., the acceleration process can have a pulsating structure, the propagation of energetic electrons and ions can be interrupted from plasma instabilities and finally the electromagnetic radiation produced by the interaction of electrostatic and electromagnetic waves may have a pulsating behavior in time. In two separate studies the conditions for rapid fluctuations in solar flare driven emission were analyzed.

  9. Universal mesoscopic conductance fluctuations

    International Nuclear Information System (INIS)

    Evangelou, S.N.

    1992-01-01

    The theory of conductance fluctuations in disordered metallic systems with size large compared to the mean free path of the electron but small compared to localization length is considered. It is demonstrates that fluctuations have an universal character and are due to repulsion between levels and spectral rigidity. The basic fluctuation measures for the energy spectrum in the mesoscopic regime of disordered systems are consistent with the Gaussian random matrix ensemble predictions. Although our disordered electron random matrix ensemble does not belong to the Gaussian ensemble the two ensembles turn out to be essentially similar. The level repulsion and the spectral rigidity found in nuclear spectra should also be observed in the metallic regime of Anderson localization. 7 refs. (orig.)

  10. Spin fluctuations and the

    Directory of Open Access Journals (Sweden)

    V.M. Loktev

    2008-09-01

    Full Text Available We analyze the spectral properties of a phenomenological model for a weakly doped two-dimensional antiferromagnet, in which the carriers move within one of the two sublattices where they were introduced. Such a constraint results in the free carrier spectra with the maxima at k=(± π/2 , ± π/2 observed in some cuprates. We consider the spectral properties of the model by taking into account fluctuations of the spins in the antiferromagnetic background. We show that such fluctuations lead to a non-pole-like structure of the single-hole Green's function and these fluctuations can be responsible for some anomalous "strange metal" properties of underdoped cuprates in the nonsuperconducting regime.

  11. The fluctuating gap model

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Xiaobin

    2011-01-15

    The quasi-one-dimensional systems exhibit some unusual phenomenon, such as the Peierls instability, the pseudogap phenomena and the absence of a Fermi-Dirac distribution function line shape in the photoemission spectroscopy. Ever since the discovery of materials with highly anisotropic properties, it has been recognized that fluctuations play an important role above the three-dimensional phase transition. This regime where the precursor fluctuations are presented can be described by the so called fluctuating gap model (FGM) which was derived from the Froehlich Hamiltonian to study the low energy physics of the one-dimensional electron-phonon system. Not only is the FGM of great interest in the context of quasi-one-dimensional materials, liquid metal and spin waves above T{sub c} in ferromagnets, but also in the semiclassical approximation of superconductivity, it is possible to replace the original three-dimensional problem by a directional average over effectively one-dimensional problem which in the weak coupling limit is described by the FGM. In this work, we investigate the FGM in a wide temperature range with different statistics of the order parameter fluctuations. We derive a formally exact solution to this problem and calculate the density of states, the spectral function and the optical conductivity. In our calculation, we show that a Dyson singularity appears in the low energy density of states for Gaussian fluctuations in the commensurate case. In the incommensurate case, there is no such kind of singularity, and the zero frequency density of states varies differently as a function of the correlation lengths for different statistics of the order parameter fluctuations. Using the density of states we calculated with non-Gaussian order parameter fluctuations, we are able to calculate the static spin susceptibility which agrees with the experimental data very well. In the calculation of the spectral functions, we show that as the correlation increases, the

  12. The fluctuating gap model

    International Nuclear Information System (INIS)

    Cao, Xiaobin

    2011-01-01

    The quasi-one-dimensional systems exhibit some unusual phenomenon, such as the Peierls instability, the pseudogap phenomena and the absence of a Fermi-Dirac distribution function line shape in the photoemission spectroscopy. Ever since the discovery of materials with highly anisotropic properties, it has been recognized that fluctuations play an important role above the three-dimensional phase transition. This regime where the precursor fluctuations are presented can be described by the so called fluctuating gap model (FGM) which was derived from the Froehlich Hamiltonian to study the low energy physics of the one-dimensional electron-phonon system. Not only is the FGM of great interest in the context of quasi-one-dimensional materials, liquid metal and spin waves above T c in ferromagnets, but also in the semiclassical approximation of superconductivity, it is possible to replace the original three-dimensional problem by a directional average over effectively one-dimensional problem which in the weak coupling limit is described by the FGM. In this work, we investigate the FGM in a wide temperature range with different statistics of the order parameter fluctuations. We derive a formally exact solution to this problem and calculate the density of states, the spectral function and the optical conductivity. In our calculation, we show that a Dyson singularity appears in the low energy density of states for Gaussian fluctuations in the commensurate case. In the incommensurate case, there is no such kind of singularity, and the zero frequency density of states varies differently as a function of the correlation lengths for different statistics of the order parameter fluctuations. Using the density of states we calculated with non-Gaussian order parameter fluctuations, we are able to calculate the static spin susceptibility which agrees with the experimental data very well. In the calculation of the spectral functions, we show that as the correlation increases, the quasi

  13. Temporal fluctuations after a quantum quench: Many-particle dephasing

    Science.gov (United States)

    Marquardt, Florian; Kiendl, Thomas

    After a quantum quench, the expectation values of observables continue to fluctuate in time. In the thermodynamic limit, one expects such fluctuations to decrease to zero, in order for standard statistical physics to hold. However, it is a challenge to determine analytically how the fluctuations decay as a function of system size. So far, there have been analytical predictions for integrable models (which are, naturally, somewhat special), analytical bounds for arbitrary systems, and numerical results for moderate-size systems. We have discovered a dynamical regime where the decrease of fluctuations is driven by many-particle dephasing, instead of a redistribution of occupation numbers. On the basis of this insight, we are able to provide exact analytical expressions for a model with weak integrability breaking (transverse Ising chain with additional terms). These predictions explicitly show how fluctuations are exponentially suppressed with system size.

  14. Spectra of turbulent static pressure fluctuations in jet mixing layers

    Science.gov (United States)

    Jones, B. G.; Adrian, R. J.; Nithianandan, C. K.; Planchon, H. P., Jr.

    1977-01-01

    Spectral similarity laws are derived for the power spectra of turbulent static pressure fluctuations by application of dimensional analysis in the limit of large turbulent Reynolds number. The theory predicts that pressure spectra are generated by three distinct types of interaction in the velocity fields: a fourth order interaction between fluctuating velocities, an interaction between the first order mean shear and the third order velocity fluctuations, and an interaction between the second order mean shear rate and the second order fluctuating velocity. Measurements of one-dimensional power spectra of the turbulent static pressure fluctuations in the driven mixing layer of a subsonic, circular jet are presented, and the spectra are examined for evidence of spectral similarity. Spectral similarity is found for the low wavenumber range when the large scale flow on the centerline of the mixing layer is self-preserving. The data are also consistent with the existence of universal inertial subranges for the spectra of each interaction mode.

  15. Controlling fluctuations in an ITB and comparison with gyrokinetic simulations

    Science.gov (United States)

    Ernst, D. R.; Fiore, C. L.; Dominguez, A.; Podpaly, Y.; Reinke, M. L.; Terry, J. L.; Tsujii, N.; Bespamyatnov, I.; Churchill, M.; Greenwald, M.; Hubbard, A.; Hughes, J. W.; Lee, J.; Ma, Y.; Wolfe, S.; Wukitch, S.

    2011-10-01

    We have modulated on-axis ICRF minority heating to trigger fluctuations and core electron transport in Alcator C-Mod Internal Transport Barriers (ITB's). Temperature swings of 50% produced strong bursts of density fluctuations, measured by phase contrast imaging (PCI), while edge fluctuations from reflectometry, Mirnov coils, and gas puff imaging (GPI) simultaneously diminished. The PCI fluctuations are in phase with sawteeth, further evidence that they originate within the ITB foot. Linear gyrokinetic analysis with GS2 shows TEMs are driven unstable in the ITB by the on-axis heating, as in Refs.,. Nonlinear gyrokinetic simulations of turbulence in the ITB are compared with fluctuation data using a synthetic diagnostic. Strong ITB's were produced with high quality ion and electron profile data. Supported by U.S. DoE awards DE-FC02-99ER54512, DE-FG02-91ER54109, DE-FC02-08ER54966.

  16. Bioclim Deliverable D10 - 12: development and application of a methodology for taking climate-driven environmental change into account in performance assessments

    International Nuclear Information System (INIS)

    2004-01-01

    The BIOCLIM project on modelling sequential Biosphere systems under Climate change for radioactive waste disposal is part of the EURATOM fifth European framework programme. The project was launched in October 2000 for a three-year period. The project aims at providing a scientific basis and practical methodology for assessing the possible long term impacts on the safety of radioactive waste repositories in deep formations due to climate and environmental change. Five work packages have been identified to fulfill the project objectives: - Work package 1 will consolidate the needs of the European agencies of the consortium and summarize how environmental change has been treated to date in performance assessments. - Work packages 2 and 3 will develop two innovative and complementary strategies for representing time series of long term climate change using different methods to analyse extreme climate conditions (the hierarchical strategy) and a continuous climate simulation over more than the next glacial-interglacial cycle (the integrated strategy). - Work package 4 will explore and evaluate the potential effects of climate change on the nature of the biosphere systems. - Work package 5 will disseminate information on the results obtained from the three year project among the international community for further use. The output from the climate models developed and applied in WP2 and WP3 has been interpreted in WP4 ('Biosphere system description') in terms of model requirements for the post-closure radiological performance assessment of deep geological repositories for radioactive wastes, in order to develop a methodology to demonstrate how biosphere systems can be represented in the long-term. The work undertaken in WP4 is described in this report. This report describes the methodology used for identification and characterisation of specific climate states and transitions between those climate states. It also covers the application of those methods in the context of

  17. Fluctuating Asymmetry and Intelligence

    Science.gov (United States)

    Bates, Timothy C.

    2007-01-01

    The general factor of mental ability ("g") may reflect general biological fitness. If so, "g"-loaded measures such as Raven's progressive matrices should be related to morphological measures of fitness such as fluctuating asymmetry (FA: left-right asymmetry of a set of typically left-right symmetrical body traits such as finger…

  18. Ecosystem Evapotranspiration as a Response to Climate and Vegetation Coverage Changes in Northwest Yunnan, China.

    Science.gov (United States)

    Yang, Hao; Luo, Peng; Wang, Jun; Mou, Chengxiang; Mo, Li; Wang, Zhiyuan; Fu, Yao; Lin, Honghui; Yang, Yongping; Bhatta, Laxmi Dutt

    2015-01-01

    Climate and human-driven changes play an important role in regional droughts. Northwest Yunnan Province is a key region for biodiversity conservation in China, and it has experienced severe droughts since the beginning of this century; however, the extent of the contributions from climate and human-driven changes remains unclear. We calculated the ecosystem evapotranspiration (ET) and water yield (WY) of northwest Yunnan Province, China from 2001 to 2013 using meteorological and remote sensing observation data and a Surface Energy Balance System (SEBS) model. Multivariate regression analyses were used to differentiate the contribution of climate and vegetation coverage to ET. The results showed that the annual average vegetation coverage significantly increased over time with a mean of 0.69 in spite of the precipitation fluctuation. Afforestation/reforestation and other management efforts attributed to vegetation coverage increase in NW Yunnan. Both ET and WY considerably fluctuated with the climate factors, which ranged from 623.29 mm to 893.8 mm and -51.88 mm to 384.40 mm over the time period. Spatially, ET in the southeast of NW Yunnan (mainly in Lijiang) increased significantly, which was in line with the spatial trend of vegetation coverage. Multivariate linear regression analysis indicated that climatic factors accounted for 85.18% of the ET variation, while vegetation coverage explained 14.82%. On the other hand, precipitation accounted for 67.5% of the WY. We conclude that the continuous droughts in northwest Yunnan were primarily climatically driven; however, man-made land cover and vegetation changes also increased the vulnerability of local populations to drought. Because of the high proportion of the water yield consumed for subsistence and poor infrastructure for water management, local populations have been highly vulnerable to climate drought conditions. We suggest that conservation of native vegetation and development of water

  19. Ecosystem Evapotranspiration as a Response to Climate and Vegetation Coverage Changes in Northwest Yunnan, China.

    Directory of Open Access Journals (Sweden)

    Hao Yang

    Full Text Available Climate and human-driven changes play an important role in regional droughts. Northwest Yunnan Province is a key region for biodiversity conservation in China, and it has experienced severe droughts since the beginning of this century; however, the extent of the contributions from climate and human-driven changes remains unclear. We calculated the ecosystem evapotranspiration (ET and water yield (WY of northwest Yunnan Province, China from 2001 to 2013 using meteorological and remote sensing observation data and a Surface Energy Balance System (SEBS model. Multivariate regression analyses were used to differentiate the contribution of climate and vegetation coverage to ET. The results showed that the annual average vegetation coverage significantly increased over time with a mean of 0.69 in spite of the precipitation fluctuation. Afforestation/reforestation and other management efforts attributed to vegetation coverage increase in NW Yunnan. Both ET and WY considerably fluctuated with the climate factors, which ranged from 623.29 mm to 893.8 mm and -51.88 mm to 384.40 mm over the time period. Spatially, ET in the southeast of NW Yunnan (mainly in Lijiang increased significantly, which was in line with the spatial trend of vegetation coverage. Multivariate linear regression analysis indicated that climatic factors accounted for 85.18% of the ET variation, while vegetation coverage explained 14.82%. On the other hand, precipitation accounted for 67.5% of the WY. We conclude that the continuous droughts in northwest Yunnan were primarily climatically driven; however, man-made land cover and vegetation changes also increased the vulnerability of local populations to drought. Because of the high proportion of the water yield consumed for subsistence and poor infrastructure for water management, local populations have been highly vulnerable to climate drought conditions. We suggest that conservation of native vegetation and development of water

  20. Multi-scalar agent-based complex design systems - the case of CECO (Climatic -Ecologies) Studio; informed generative design systems and performance-driven design workflows

    NARCIS (Netherlands)

    Mostafavi, S.; Yu, S.; Biloria, N.M.

    2014-01-01

    This paper illustrates the application of different types of complex systems for digital form finding and design decision making with underlying methodological and pedagogical aims to emphasize performance-driven design solutions via combining generative methods of complex systems with simulation

  1. Cytoskeleton dynamics: Fluctuations within the network

    International Nuclear Information System (INIS)

    Bursac, Predrag; Fabry, Ben; Trepat, Xavier; Lenormand, Guillaume; Butler, James P.; Wang, Ning; Fredberg, Jeffrey J.; An, Steven S.

    2007-01-01

    Out-of-equilibrium systems, such as the dynamics of a living cytoskeleton (CSK), are inherently noisy with fluctuations arising from the stochastic nature of the underlying biochemical and molecular events. Recently, such fluctuations within the cell were characterized by observing spontaneous nano-scale motions of an RGD-coated microbead bound to the cell surface [Bursac et al., Nat. Mater. 4 (2005) 557-561]. While these reported anomalous bead motions represent a molecular level reorganization (remodeling) of microstructures in contact with the bead, a precise nature of these cytoskeletal constituents and forces that drive their remodeling dynamics are largely unclear. Here, we focused upon spontaneous motions of an RGD-coated bead and, in particular, assessed to what extent these motions are attributable to (i) bulk cell movement (cell crawling), (ii) dynamics of focal adhesions, (iii) dynamics of lipid membrane, and/or (iv) dynamics of the underlying actin CSK driven by myosin motors

  2. Phase Transition in Protocols Minimizing Work Fluctuations

    Science.gov (United States)

    Solon, Alexandre P.; Horowitz, Jordan M.

    2018-05-01

    For two canonical examples of driven mesoscopic systems—a harmonically trapped Brownian particle and a quantum dot—we numerically determine the finite-time protocols that optimize the compromise between the standard deviation and the mean of the dissipated work. In the case of the oscillator, we observe a collection of protocols that smoothly trade off between average work and its fluctuations. However, for the quantum dot, we find that as we shift the weight of our optimization objective from average work to work standard deviation, there is an analog of a first-order phase transition in protocol space: two distinct protocols exchange global optimality with mixed protocols akin to phase coexistence. As a result, the two types of protocols possess qualitatively different properties and remain distinct even in the infinite duration limit: optimal-work-fluctuation protocols never coalesce with the minimal-work protocols, which therefore never become quasistatic.

  3. Climate catastrophes

    Science.gov (United States)

    Budyko, Mikhail

    1999-05-01

    Climate catastrophes, which many times occurred in the geological past, caused the extinction of large or small populations of animals and plants. Changes in the terrestrial and marine biota caused by the catastrophic climate changes undoubtedly resulted in considerable fluctuations in global carbon cycle and atmospheric gas composition. Primarily, carbon dioxide and other greenhouse gas contents were affected. The study of these catastrophes allows a conclusion that climate system is very sensitive to relatively small changes in climate-forcing factors (transparency of the atmosphere, changes in large glaciations, etc.). It is important to take this conclusion into account while estimating the possible consequences of now occurring anthropogenic warming caused by the increase in greenhouse gas concentration in the atmosphere.

  4. Deep soil carbon dynamics are driven more by soil type than by climate: a worldwide meta-analysis of radiocarbon profiles.

    Science.gov (United States)

    Mathieu, Jordane A; Hatté, Christine; Balesdent, Jérôme; Parent, Éric

    2015-11-01

    The response of soil carbon dynamics to climate and land-use change will affect both the future climate and the quality of ecosystems. Deep soil carbon (>20 cm) is the primary component of the soil carbon pool, but the dynamics of deep soil carbon remain poorly understood. Therefore, radiocarbon activity (Δ14C), which is a function of the age of carbon, may help to understand the rates of soil carbon biodegradation and stabilization. We analyzed the published 14C contents in 122 profiles of mineral soil that were well distributed in most of the large world biomes, except for the boreal zone. With a multivariate extension of a linear mixed-effects model whose inference was based on the parallel combination of two algorithms, the expectation-maximization (EM) and the Metropolis-Hasting algorithms, we expressed soil Δ14C profiles as a four-parameter function of depth. The four-parameter model produced insightful predictions of soil Δ14C as dependent on depth, soil type, climate, vegetation, land-use and date of sampling (R2=0.68). Further analysis with the model showed that the age of topsoil carbon was primarily affected by climate and cultivation. By contrast, the age of deep soil carbon was affected more by soil taxa than by climate and thus illustrated the strong dependence of soil carbon dynamics on other pedologic traits such as clay content and mineralogy. © 2015 John Wiley & Sons Ltd.

  5. Fluctuations in quantum devices

    Directory of Open Access Journals (Sweden)

    H.Haken

    2004-01-01

    Full Text Available Logical gates can be formalized by Boolean algebra whose elementary operations can be realized by devices that employ the interactions of macroscopic numbers of elementary excitations such as electrons, holes, photons etc. With increasing miniaturization to the nano scale and below, quantum fluctuations become important and can no longer be ignored. Based on Heisenberg equations of motion for the creation and annihilation operators of elementary excitations, I determine the noise sources of composite quantum systems.

  6. Idiosyncratic responses to climate-driven forest fragmentation and marine incursions in reed frogs from Central Africa and the Gulf of Guinea Islands

    DEFF Research Database (Denmark)

    Bell, Rayna C.; Parra, Juan L.; Badjedjea, Gabriel

    2017-01-01

    Organismal traits interact with environmental variation to mediate how species respond to shared landscapes. Thus, differences in traits related to dispersal ability or physiological tolerance may result in phylogeographic discordance among co-distributed taxa, even when they are responding....... Our species-specific estimates of climatic suitability through time are consistent with temporal and spatial heterogeneity in diversification among the species complexes, indicating that differences in ecological breadth may partly explain these idiosyncratic patterns. Likewise, we demonstrated...... of the species complexes. Despite marked differences in the geographic extent of stable climates and temporal estimates of divergence among the species complexes, we recovered a shared pattern of intermittent climatic suitability with recent population connectivity and demographic expansion across the Congo...

  7. Climate-driven shifts in continental net primary production implicated as a driver of a recent abrupt increase in the land carbon sink

    Science.gov (United States)

    Buermann, Wolfgang; Beaulieu, Claudie; Parida, Bikash; Medvigy, David; Collatz, George J.; Sheffield, Justin; Sarmiento, Jorge L.

    2016-03-01

    The world's ocean and land ecosystems act as sinks for anthropogenic CO2, and over the last half century their combined sink strength grew steadily with increasing CO2 emissions. Recent analyses of the global carbon budget, however, have uncovered an abrupt, substantial ( ˜ 1 PgC yr-1) and sustained increase in the land sink in the late 1980s whose origin remains unclear. In the absence of this prominent shift in the land sink, increases in atmospheric CO2 concentrations since the late 1980s would have been ˜ 30 % larger than observed (or ˜ 12 ppm above current levels). Global data analyses are limited in regards to attributing causes to changes in the land sink because different regions are likely responding to different drivers. Here, we address this challenge by using terrestrial biosphere models constrained by observations to determine if there is independent evidence for the abrupt strengthening of the land sink. We find that net primary production significantly increased in the late 1980s (more so than heterotrophic respiration), consistent with the inferred increase in the global land sink, and that large-scale climate anomalies are responsible for this shift. We identify two key regions in which climatic constraints on plant growth have eased: northern Eurasia experienced warming, and northern Africa received increased precipitation. Whether these changes in continental climates are connected is uncertain, but North Atlantic climate variability is important. Our findings suggest that improved understanding of climate variability in the North Atlantic may be essential for more credible projections of the land sink under climate change.

  8. Developing User-Driven Climate Information Services to Build Resilience Amongst Groups at Risk of Drought and Flood in Arid and Semi-Arid Land Counties in Kenya

    Science.gov (United States)

    Githungo, W. N.; Shaka, A.; Kniveton, D.; Muithya, L.; Powell, R.; Visman, E. L.

    2014-12-01

    The Arid and Semi-Arid Land (ASAL) counties of Kitui and Makueni in Kenya are experiencing increasing climate variability in seasonal rainfall, including changes in the onset, cessation and distribution of the two principal rains upon which the majority of the population's small-holder farmers and livestock keepers depend. Food insecurity is prevalent with significant numbers also affected by flooding during periods of intense rainfall. As part of a multi-partner Adaptation Consortium, Kenya Meteorological Services (KMS) are developing Climate Information Services (CIS) which can better support decision making amongst the counties' principal livelihoods groups and across County Government ministries. Building on earlier pilots and stakeholder discussion, the system combines the production of climate information tailored for transmission via regional and local radio stations with the establishment of a new SMS service. SMS are provided through a network of CIS intermediaries drawn from across key government ministries, religious networks, non-governmental and community groups, aiming to achieve one SMS recipient per 3-500 people. It also introduces a demand-led, premium-rate SMS weather information service which is designed to be self-financing in the long term. Supporting the ongoing process of devolution, KMS is downscaling national forecasts for each county, and providing seasonal, monthly, weekly and daily forecasts, as well as warnings of weather-related hazards. Through collaboration with relevant ministries, government bodies and research institutions, including livestock, agriculture, drought management and health, technical advisories are developed to provide guidance on application of the climate information. The system seeks to provide timely, relevant information which can enable people to use weather and climate information to support decisions which protect life and property and build resilience to ongoing climate variability and future change.

  9. Long-Term Trends and Temporal Synchrony in Plankton Richness, Diversity and Biomass Driven by Re-Oligotrophication and Climate across 17 Danish Lakes

    Directory of Open Access Journals (Sweden)

    Korhan Özkan

    2016-09-01

    Full Text Available A two-decade (1989–2008 time series of lake phyto- and zooplankton, water characteristics and climate in 17 Danish lakes was analysed to examine the long term changes and the effects of lake restoration efforts. The analyses of the pair-wise correlations across time series revealed a strong synchrony in climatic variables among the lakes. A significant, but weak increase in air temperature was observed and resulted in a corresponding increase in surface water temperature only in summer. Lake physico-chemical variables had weaker synchrony than climatic variables. Synchrony in water temperature and stratification was stronger than lake chemistry as the former is mostly affected by atmospheric energy flux. Synchrony in the taxonomic richness of the plankton groups and phytoplankton biomass was apparent, to a similar degree as observed for lake chemistry. The synchrony and the temporal trends in lake chemistry and plankton were more pronounced for the lakes with strong re-oligotrophication. Phytoplankton biomass decreased and plankton richness increased in these lakes, with a shift from Chlorophyta dominance towards more heterogeneous phytoplankton communities. Notably, a widespread significant positive trend in plankton richness was observed not only in lakes with strong re-oligotrophication but across all lakes. The widespread increase in plankton richness coincided with widespread decrease in phosphate and total nitrogen concentrations, as well as with the trends in climate indicating a likely joint effect of nutrient reduction and climate in driving lake plankton. However, temporal changes and synchrony as well as the recovery of richness and composition of lake plankton more coherently corresponded with the nutrient loading reduction across the Danish landscape, while the role of climate control of the lake plankton was less pronounced.

  10. Glacial Fluctuation in the Source Region of the Yangtze River

    International Nuclear Information System (INIS)

    Shengyi, Gao; Qingsong, Fan; Xi, Cao; Li, Ma

    2014-01-01

    Glaciers in the source region of the Yangtze River are not only water resources but also important energy and environmental resources. Glacial fluctuation is an important component of the study of changes in the natural environment, including climate change. We investigated the glaciers in the source region of the Yangtze River, and analyzed the fluctuations using multi-temporal remote sensing data. The trend in glacial fluctuation and the factors that influence it were determined. The results have implications for water resource management and environmental conservation in the Yangtze River region

  11. Lake level fluctuations boost toxic cyanobacterial "oligotrophic blooms".

    Directory of Open Access Journals (Sweden)

    Cristiana Callieri

    Full Text Available Global warming has been shown to strongly influence inland water systems, producing noticeable increases in water temperatures. Rising temperatures, especially when combined with widespread nutrient pollution, directly favour the growth of toxic cyanobacteria. Climate changes have also altered natural water level fluctuations increasing the probability of extreme events as dry periods followed by heavy rains. The massive appearance of Dolichospermum lemmermannii ( = planktonic Anabaena, a toxic species absent from the pelagic zone of the subalpine oligotrophic Lake Maggiore before 2005, could be a consequence of the unusual fluctuations of lake level in recent years. We hypothesized that these fluctuations may favour the cyanobacterium as result of nutrient pulses from the biofilms formed in the littoral zone when the lake level is high. To help verify this, we exposed artificial substrates in the lake, and evaluated their nutrient enrichment and release after desiccation, together with measurements of fluctuations in lake level, precipitation and D. lemmermannii population. The highest percentage of P release and the lowest C:P molar ratio of released nutrients coincided with the summer appearance of the D. lemmermannii bloom. The P pulse indicates that fluctuations in level counteract nutrient limitation in this lake and it is suggested that this may apply more widely to other oligotrophic lakes. In view of the predicted increase in water level fluctuations due to climate change, it is important to try to minimize such fluctuations in order to mitigate the occurrence of cyanobacterial blooms.

  12. Fluctuations and Instability in Sedimentation

    KAUST Repository

    Guazzelli, É lisabeth; Hinch, John

    2011-01-01

    This review concentrates on the fluctuations of the velocities of sedimenting spheres, and on the structural instability of a suspension of settling fibers. For many years, theoretical estimates and numerical simulations predicted the fluctuations

  13. Fluctuation theorems and orbital magnetism in nonequilibrium state

    Indian Academy of Sciences (India)

    We study Langevin dynamics of a driven charged particle in the presence as well as in the absence of magnetic field. We discuss the validity of various work fluctuation theorems using different model potentials and external drives. We also show that one can generate an orbital magnetic moment in a nonequilibrium state ...

  14. Queues and Lévy fluctuation theory

    CERN Document Server

    Dębicki, Krzysztof

    2015-01-01

    The book provides an extensive introduction to queueing models driven by Lévy-processes as well as a systematic account of the literature on Lévy-driven queues. The objective is to make the reader familiar with the wide set of probabilistic techniques that have been developed over the past decades, including transform-based techniques, martingales, rate-conservation arguments, change-of-measure, importance sampling, and large deviations. On the application side, it demonstrates how Lévy traffic models arise when modelling current queueing-type systems (as communication networks) and includes applications to finance. Queues and Lévy Fluctuation Theory will appeal to graduate/postgraduate students and researchers in mathematics, computer science, and electrical engineering. Basic prerequisites are probability theory and stochastic processes.

  15. Neodymium isotope constraints on provenance, dispersal, and climate-driven supply of Zambezi sediments along the Mozambique Margin during the past similar to 45,000 years

    NARCIS (Netherlands)

    van der Lubbe, H.J.L.; Frank, M.; Tjallingii, R.; Schneider, R.

    2016-01-01

    Marine sediments deposited off the Zambezi River that drains a considerable part of the south-east African continent provide continuous records of the continental climatic and environmental conditions.Here we present time series of neodymium (Nd) isotope signatures of the detrital sediment fraction

  16. Idiosyncratic responses to climate-driven forest fragmentation and marine incursions in reed frogs from Central Africa and the Gulf of Guinea Islands

    Czech Academy of Sciences Publication Activity Database

    Bell, R. C.; Parra, J. L.; Badjedjea, G.; Barej, M. F.; Blackburn, D. C.; Burger, M.; Channing, A.; Dehling, J. M.; Greenbaum, E.; Gvoždík, Václav; Kielgast, J.; Kusamba, C.; Lötters, S.; McLaughlin, P. J.; Nagy, Z. T.; Rödel, M.-O.; Portik, D. M.; Stuart, B. L.; VanDerWal, J.; Zassi-Boulou, A.-G.; Zamudio, K. R.

    2017-01-01

    Roč. 26, č. 19 (2017), s. 5223-5244 ISSN 0962-1083 R&D Projects: GA ČR GJ15-13415Y Institutional support: RVO:68081766 Keywords : climatic refugia * ecological niche modelling * Hyperolius * land-bridge island * lineage divergence * riverine barriers Subject RIV: EH - Ecology, Behaviour OBOR OECD: Ecology Impact factor: 6.086, year: 2016

  17. Large regional variability of recent climatic change driven sub-surface temperature changes as derived from temperature logs-central Canada example

    Czech Academy of Sciences Publication Activity Database

    Majorowicz, J.; Šafanda, Jan

    2018-01-01

    Roč. 107, č. 1 (2018), s. 123-135 ISSN 1437-3254 Institutional support: RVO:67985530 Keywords : ground warming * borehole climatology * land use change climate change drivers * Central Canada Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 2.283, year: 2016

  18. Fluctuations in Schottky barrier heights

    International Nuclear Information System (INIS)

    Mahan, G.D.

    1984-01-01

    A double Schottky barrier is often formed at the grain boundary in polycrystalline semiconductors. The barrier height is shown to fluctuate in value due to the random nature of the impurity positions. The magnitude of the fluctuations is 0.1 eV, and the fluctuations cause the barrier height measured by capacitance to differ from the one measured by electrical conductivity

  19. Strain fluctuations and elastic constants

    Energy Technology Data Exchange (ETDEWEB)

    Parrinello, M.; Rahman, A.

    1982-03-01

    It is shown that the elastic strain fluctuations are a direct measure of elastic compliances in a general anisotropic medium; depending on the ensemble in which the fluctuation is measured either the isothermal or the adiabatic compliances are obtained. These fluctuations can now be calculated in a constant enthalpy and pressure, and hence, constant entropy, ensemble due to recent develpments in the molecular dynamics techniques. A calculation for a Ni single crystal under uniform uniaxial 100 tensile or compressive load is presented as an illustration of the relationships derived between various strain fluctuations and the elastic modulii. The Born stability criteria and the behavior of strain fluctuations are shown to be related.

  20. Holocene glacial fluctuations in southern South America

    Science.gov (United States)

    Reynhout, S.; Sagredo, E. A.; Kaplan, M. R.; Aravena, J. C.; Martini, M. A.; Strelin, J. A.; Schaefer, J. M.

    2016-12-01

    Understanding the timing and magnitude of former glacier fluctuations is critical to decipher long-term climatic trends and to unravel both natural cycles and human impact on the current glacial behavior. Despite more than seven decades of research efforts, a unifying model of Holocene glacial fluctuations in Southern South America remains elusive. Here, we present the state-of-the-art regarding the timing of Holocene glacial fluctuation in southern Patagonia-Tierra del Fuego, with a focus on a new generation of high-resolution radiocarbon and 10Be surface exposure dating chronologies. Recently acquired evidence suggest that after receding from advanced Late Glacial positions, Patagonian glaciers were for the most part close to, or even behind, present ice margins during the Early Holocene. On the other hand, emerging chronologies indicate that in some areas there were extensive expansions (century scale?) that punctuated the warm interval. Subsequently, we have evidence of multiple millennial timescale glacial advances starting in the middle Holocene. Several glacial maxima are defined by moraines and other landforms from 7000 years ago to the 19th century, with a gap sometime between 4,500 and 2,500 years ago. The last set of advances began around 800-600 years ago. Although glacial activity is documented in Patagonia at the same time as the European Little Ice Age, the extent of these glacial events are less prominent than those of the mid-Holocene. The causes that may explain these glacial fluctuations remain elusive. Finally, we discuss ongoing efforts to better define the timing and extent of Holocene glaciations in southern South America, and to establish the basis to test competing hypothesis of regional Holocene climate variability.

  1. Gambling with Superconducting Fluctuations

    Science.gov (United States)

    Foltyn, Marek; Zgirski, Maciej

    2015-08-01

    Josephson junctions and superconducting nanowires, when biased close to superconducting critical current, can switch to a nonzero voltage state by thermal or quantum fluctuations. The process is understood as an escape of a Brownian particle from a metastable state. Since this effect is fully stochastic, we propose to use it for generating random numbers. We present protocol for obtaining random numbers and test the experimentally harvested data for their fidelity. Our work is prerequisite for using the Josephson junction as a tool for stochastic (probabilistic) determination of physical parameters such as magnetic flux, temperature, and current.

  2. Fluctuations in the hadronization

    International Nuclear Information System (INIS)

    Bozek, P.; Ploszajaczak, M.

    1992-01-01

    The multiscaling in the fluctuations of the multiparticle distributions at small scales is studied. Similarly to the multiscaling effect, recently found in multifractal models, the dependence of the intermittency patterns on the low density cut-off in the cascade is analyzed. The effect changes the scaling behaviour and leads to stronger dependence of the scaled factorial moments on the resolution than the power law. This could be an explanation of the behaviour observed recently in the experimental 3-dimensional data. The multiscaling analysis allows to restore the universality in the processes with different cut-offs and could be used in the analysis of the experimental data. (author) 17 refs., 5 figs

  3. Photoinduced Coherent Spin Fluctuation in Primary Dynamics of Insulator to Metal Transition in Perovskite Cobalt Oxide

    Directory of Open Access Journals (Sweden)

    Arima T.

    2013-03-01

    Full Text Available Coherent spin fluctuation was detected in the photoinduced Mott insulator-metal transition in perovskite cobalt oxide by using 3 optical-cycle infrared pulse. Such coherent spin fluctuation is driven by the perovskite distortion changing orbital gap.

  4. Climate Benefits of Potential Avoided Emissions from Forest Conversion Diminished by Albedo Warming: Comprehensive, Data-Driven Assessment for the US and Beyond

    Science.gov (United States)

    Williams, C. A.; Gu, H.; Jiao, T.

    2017-12-01

    Avoided deforestation is a leading pathway for climate change mitigation, featuring prominently in many country's Intended Nationally Determined Contributions, but its climate benefits remain contested, in part because of reports of large offsetting effects in some regions of the world. It is well known that avoiding forest to non-forest conversion prevents forest carbon release, and sustains forest carbon uptake, but also increases albedo thus diminishing the potency of this mitigation strategy. While the mechanisms are known, their relative importance and the resulting climate benefit remain unclear. This is in part due to a lack of quantitative assessments documenting geographic variation in rates of forest conversion, associated carbon emissions, resulting radiative forcing, and the magnitude of simultaneous albedo offsets. This study (i) quantifies the current rate of forest conversion and carbon release in the United States with Landsat remote sensing and a carbon assessment framework, and (ii) compares this to quantitative estimates of the radiative forcing from the corresponding albedo change. Albedo radiative forcing is assessed with a recently-generated, global atlas of land-cover-specific albedos derived from a fusion of MODIS and Landsat reflectances, combined with snow cover and solar radiation datasets. We document the degree to which albedo warming offsets carbon cooling from contemporary forest conversions taking place in different regions of the United States and identify the underlying drivers of spatial variability. We then extend this to other regions of the world where forests are under threat and where avoided deforestation is viewed as a primary tool for climate mitigation. Results shed light on the, at times contentious, debate about the efficacy of forest protection as a mitigation mechanism.

  5. Drainage isolation and climate change-driven population expansion shape the genetic structures of Tuber indicum complex in the Hengduan Mountains region.

    Science.gov (United States)

    Feng, Bang; Zhao, Qi; Xu, Jianping; Qin, Jiao; Yang, Zhu L

    2016-02-24

    The orogenesis of the Qinghai-Tibetan Plateau and the Quaternary climate changes have played key roles in driving the evolution of flora and fauna in Southwest China, but their effects on higher fungi are poorly addressed. In this study, we investigated the phylogeographic pattern of the Tuber indicum species complex, an economically important fungal group distributed in the Hengduan Mountains region. Our data confirmed the existence of two distinct lineages, T. indicum and T. himalayense, within this species complex. Three geographic groups (Groups W, N and C) were revealed within T. indicum, with Group W found in the paleo-Lancang River region, while Groups N and C corresponded to the two banks along the contemporary Jinsha River, suggesting that rivers have acted as barriers for gene flow among populations from different drainages. Historical range expansion resulted from climate changes was inferred in Group C, contributing to the observed gene flow among geographic populations within this group. Although no significant geographic structure was identified in T. himalayense, evidence of drainage isolation for this species was also detected. Our findings demonstrate that both topographic changes and Quaternary climate oscillations have played important roles in driving the genetic structures of the T. indicum species complex.

  6. Climate and Global Change

    International Nuclear Information System (INIS)

    Duplessy, J.C.; Pons, A.; Fantechi, R.

    1991-01-01

    The present volume contains the lessons delivered at the course held in Arles, France, on the subject Climate and Global Change: natural variability of the geosphere and biosphere systems, biogeochemical cycles and their perturbation by human activities, monitoring and forecasting global changes (satellite observations, modelling,...). Short presentations of students' own research activities are also proposed (climatic fluctuation in the Mediterranean area, climate/vegetation relations, etc.)

  7. Climate-driven unsteady denudation and sediment flux in a high-relief unglaciated catchment-fan using 26Al and 10Be: Panamint Valley, California

    Science.gov (United States)

    Mason, Cody C.; Romans, Brian W.

    2018-06-01

    Environmental changes within erosional catchments of sediment routing systems are predicted to modulate sediment transfer dynamics. However, empirical and numerical models that predict such phenomena are difficult to test in natural systems over multi-millennial timescales. Tectonic boundary conditions and climate history in the Panamint Range, California, are relatively well-constrained by existing low-temperature thermochronology and regional multi-proxy paleoclimate studies, respectively. Catchment-fan systems present there minimize sediment storage and recycling, offering an excellent natural laboratory to test models of climate-sedimentary dynamics. We used stratigraphic characterization and cosmogenic radionuclides (CRNs; 26Al and 10Be) in the Pleasant Canyon complex (PCC), a linked catchment-fan system, to examine the effects of Pleistocene high-magnitude, high-frequency climate change on CRN-derived denudation rates and sediment flux in a high-relief, unglaciated catchment-fan system. Calculated 26Al/10Be burial ages from 13 samples collected in an ∼180 m thick outcropping stratigraphic succession range from ca. 1.55 ± 0.22 Ma in basal strata, to ca. 0.36 ± 0.18-0.52 ± 0.20 Ma within the uppermost part of the succession. The mean long-term CRN-derived paleodenudation rate, 36 ± 8 mm/kyr (1σ), is higher than the modern rate of 24 ± 0.6 mm/kyr from Pleasant Canyon, and paleodenudation rates during the middle Pleistocene display some high-frequency variability in the high end (up to 54 ± 10 mm/kyr). The highest CRN-derived denudation rates are associated with stratigraphic evidence for increased precipitation during glacial-pluvial events after the middle Pleistocene transition (post ca. 0.75 Ma), suggesting 100 kyr Milankovitch periodicity could drive the observed variability. We investigated the potential for non-equilibrium sedimentary processes, i.e. increased landslides or sediment storage/recycling, to influence apparent paleodenudation rates

  8. Assessing Disparities of Dengue Virus Transmission Risk across the US-Mexican Border Using a Climate Driven Vector-Epidemiological Model

    Science.gov (United States)

    Morin, Cory; Monaghan, Andrew; Quattrochi, Dale; Crosson, William; Hayden, Mary; Ernst, Kacey

    2015-01-01

    Dengue fever is a mosquito-borne viral disease reemerging throughout much of the tropical Americas. Dengue virus transmission is explicitly influenced by climate and the environment through its primary vector, Aedes aegypti. Temperature regulates Ae. aegypti development, survival, and replication rates as well as the incubation period of the virus within the mosquito. Precipitation provides water for many of the preferred breeding habitats of the mosquito, including buckets, old tires, and other places water can collect. Although transmission regularly occurs along the border region in Mexico, dengue virus transmission in bordering Arizona has not occurred. Using NASA's TRMM (Tropical Rainfall Measuring Mission) satellite for precipitation input and Daymet for temperature and supplemental precipitation input, we modeled dengue transmission along a US-Mexico transect using a dynamic dengue transmission model that includes interacting vector ecology and epidemiological components. Model runs were performed for 5 cities in Sonora, Mexico and southern Arizona. Employing a Monte Carlo approach, we performed ensembles of several thousands of model simulations in order to resolve the model uncertainty arising from using different combinations of parameter values that are not well known. For cities with reported dengue case data, the top model simulations that best reproduced dengue case numbers were retained and their parameter values were extracted for comparison. These parameter values were used to run simulations in areas where dengue virus transmission does not occur or where dengue fever case data was unavailable. Additional model runs were performed to reveal how changes in climate or parameter values could alter transmission risk along the transect. The relative influence of climate variability and model parameters on dengue virus transmission is assessed to help public health workers prepare location specific infection prevention strategies.

  9. Fluctuation Relations for Currents

    Science.gov (United States)

    Sinitsyn, Nikolai; Akimov, Alexei; Chernyak, Vladimir; Chertkov, Michael

    2011-03-01

    We consider a non-equilibrium statistical system on a graph or a network. Identical particles are injected, interact with each other, traverse, and leave the graph in a stochastic manner described in terms of Poisson rates, possibly strongly dependent on time and instantaneous occupation numbers at the nodes of the graph. We show that the system demonstrates a profound statistical symmetry, leading to new Fluctuation Relations that originate from the supersymmetry and the principle of the geometric universality of currents rather than from the relations between probabilities of forward and reverse trajectories. NSF/ECCS-0925618, NSF/CHE-0808910 and DOE at LANL under Contract No. DE-AC52-06NA25396.

  10. Fluctuations in email size

    Science.gov (United States)

    Matsubara, Yoshitsugu; Musashi, Yasuo

    2017-12-01

    The purpose of this study is to explain fluctuations in email size. We have previously investigated the long-term correlations between email send requests and data flow in the system log of the primary staff email server at a university campus, finding that email size frequency follows a power-law distribution with two inflection points, and that the power-law property weakens the correlation of the data flow. However, the mechanism underlying this fluctuation is not completely understood. We collected new log data from both staff and students over six academic years and analyzed the frequency distribution thereof, focusing on the type of content contained in the emails. Furthermore, we obtained permission to collect "Content-Type" log data from the email headers. We therefore collected the staff log data from May 1, 2015 to July 31, 2015, creating two subdistributions. In this paper, we propose a model to explain these subdistributions, which follow log-normal-like distributions. In the log-normal-like model, email senders -consciously or unconsciously- regulate the size of new email sentences according to a normal distribution. The fitting of the model is acceptable for these subdistributions, and the model demonstrates power-law properties for large email sizes. An analysis of the length of new email sentences would be required for further discussion of our model; however, to protect user privacy at the participating organization, we left this analysis for future work. This study provides new knowledge on the properties of email sizes, and our model is expected to contribute to the decision on whether to establish upper size limits in the design of email services.

  11. Fluctuating Thermodynamics for Biological Processes

    Science.gov (United States)

    Ham, Sihyun

    Because biomolecular processes are largely under thermodynamic control, dynamic extension of thermodynamics is necessary to uncover the mechanisms and driving factors of fluctuating processes. The fluctuating thermodynamics technology presented in this talk offers a practical means for the thermodynamic characterization of conformational dynamics in biomolecules. The use of fluctuating thermodynamics has the potential to provide a comprehensive picture of fluctuating phenomena in diverse biological processes. Through the application of fluctuating thermodynamics, we provide a thermodynamic perspective on the misfolding and aggregation of the various proteins associated with human diseases. In this talk, I will present the detailed concepts and applications of the fluctuating thermodynamics technology for elucidating biological processes. This work was supported by Samsung Science and Technology Foundation under Project Number SSTF-BA1401-13.

  12. Magnetic fluctuations in heavy fermion systems

    International Nuclear Information System (INIS)

    Broholm, C.L.

    1989-06-01

    Magnetic order and fluctuations in the heavy Fermion systems UPt 3 , U 2 Zn 17 and URu 2 Si 2 have been studied by neutron scattering. Single crystalline samples and triple-axis neutron-scattering techniques with energy transfers between 0 and 40 meV and energy resolutions between 0.1 meV and 4 meV have been employed. UPt 3 develops an antiferromagnetically ordered moment of (0.02±0.005) μ B below T N = 5 K which doubles the unit cell in the basal plane and coexists with superconductivity below T c = 0.5 K. The magnetic fluctuations are relaxational, and enhanced at the antiferromagnetic zone center in a low-energy regime. The characteristic zone-center relaxation energy is 0.3 meV. The temperature- and field-dependence of the antiferromagnetic order in the superconducting phase suggest a close relation between these two properties in UPt 3 . U 2 Zn 17 has a broad spectrum of magnetic fluctuations, even below T N = 9.7 K, of which the transverse part below 10 meV is strongly enhanced at the antiferromagnetic zone center. The system has an anomalously extended critical region and the antiferromagnetic phase transition seems to be driven by the temperature-dependence of an effective RKKY interaction, as anticipated theoretically. URu 2 Si 2 , a strongly anisotropic heavy Fermion system, has a high-energy regime of antiferromagnetically-correlated overdamped magnetic fluctuations. Below T N = 17.5 K weak antiferromagnetic order, μ = (0.04±0.01)μ B , with finite correlations along the tetragonal c axis, develops along with a low-energy regime of strongly dispersive singlet-singlet excitations. Below T c = 1 K antiferromagnetism coexists with superconductivity. A phenomenological model describing the exchange-enhanced overdamped magnetic fluctuations of heavy Fermion systems is proposed. Our experimental results are compared to the anomalous bulk properties of heavy Fermion systems, and to magnetic fluctuations in other metallic magnets. (orig.)

  13. Big Bang or vacuum fluctuation

    International Nuclear Information System (INIS)

    Zel'dovich, Ya.B.

    1980-01-01

    Some general properties of vacuum fluctuations in quantum field theory are described. The connection between the ''energy dominance'' of the energy density of vacuum fluctuations in curved space-time and the presence of singularity is discussed. It is pointed out that a de-Sitter space-time (with the energy density of the vacuum fluctuations in the Einstein equations) that matches the expanding Friedman solution may describe the history of the Universe before the Big Bang. (P.L.)

  14. Two Late Pleistocene climate-driven incision/aggradation rhythms in the middle Dnieper River basin, west-central Russian Plain

    Science.gov (United States)

    Panin, Andrei; Adamiec, Grzegorz; Buylaert, Jan-Pieter; Matlakhova, Ekaterina; Moska, Piotr; Novenko, Elena

    2017-06-01

    In valleys of the River Seim and its tributaries in the middle Dnieper basin (west-central Russian Plain), two low terraces (T1, 10-16 m, and T0, 5-7 m above the river) and a floodplain (2-4 m) with characteristic large and small palaeochannels exist. A range of field and laboratory techniques was applied and ∼30 new numerical ages (OSL and 14C dates) were obtained to establish a chronology of incision and aggradation events that resulted in the current valley morphology. Two full incision/aggradation rhythms and one additional aggradation phase from the previous rhythm were recognized in the Late Pleistocene - Holocene climate cycle. The following events were detected. (1) Late MIS 5 - early MIS 4: aggradation of Terrace T1 following the deep incision at the end of MIS 6. (2) Late MIS 4 (40-30 ka): incision into Terrace T1 below the present-day river, formation of the main scarp in the bottom of the valley between Terrace T1 and Terrace T0/Floodplain levels. (3) MIS 2: aggradation of Terrace T0, lateral migrations of a shallow braided channel located few meters above the present-day river since ∼25 ka through the LGM. (4) 18-13 ka: incision into Terrace T0 below the modern river. Multiple-thread channels concentrated in a single flow that at some places formed large meanders. In the period 15-13 ka, high floods that rose above the present-day floods left large levees and overbank loams on Terrace T0. (5) Younger Dryas - Holocene transition: aggradation up to the modern channel level, transformation of large Late Glacial to small Holocene meanders. The established incision/aggradation rhythms are believed to be manifested over the Central Russian Plain outside the influence of ice sheets in the north and base level changes in the south. The two-phase deepening of the valley occurred in the last quarter of the last glacial epoch but can not be attributed directly to the glacial-interglacial transition. Both the detected incision events correspond to relatively

  15. Thermodynamic theory of equilibrium fluctuations

    International Nuclear Information System (INIS)

    Mishin, Y.

    2015-01-01

    The postulational basis of classical thermodynamics has been expanded to incorporate equilibrium fluctuations. The main additional elements of the proposed thermodynamic theory are the concept of quasi-equilibrium states, a definition of non-equilibrium entropy, a fundamental equation of state in the entropy representation, and a fluctuation postulate describing the probability distribution of macroscopic parameters of an isolated system. Although these elements introduce a statistical component that does not exist in classical thermodynamics, the logical structure of the theory is different from that of statistical mechanics and represents an expanded version of thermodynamics. Based on this theory, we present a regular procedure for calculations of equilibrium fluctuations of extensive parameters, intensive parameters and densities in systems with any number of fluctuating parameters. The proposed fluctuation formalism is demonstrated by four applications: (1) derivation of the complete set of fluctuation relations for a simple fluid in three different ensembles; (2) fluctuations in finite-reservoir systems interpolating between the canonical and micro-canonical ensembles; (3) derivation of fluctuation relations for excess properties of grain boundaries in binary solid solutions, and (4) derivation of the grain boundary width distribution for pre-melted grain boundaries in alloys. The last two applications offer an efficient fluctuation-based approach to calculations of interface excess properties and extraction of the disjoining potential in pre-melted grain boundaries. Possible future extensions of the theory are outlined.

  16. Two Late Pleistocene climate-driven incision/aggradation rhythms in the middle Dnieper River basin, west-central Russian Plain

    DEFF Research Database (Denmark)

    Panin, Andrei; Adamiec, Grzegorz; Buylaert, Jan-Pieter

    2017-01-01

    Pleistocene - Holocene climate cycle. The following events were detected. (1) Late MIS 5 - early MIS 4: aggradation of Terrace T1 following the deep incision at the end of MIS 6. (2) Late MIS 4 (40-30 ka): incision into Terrace T1 below the present-day river, formation of the main scarp in the bottom...... of the valley between Terrace T1 and Terrace T0/Floodplain levels. (3) MIS 2: aggradation of Terrace T0, lateral migrations of a shallow braided channel located few meters above the present-day river since ∼25 ka through the LGM. (4) 18-13 ka: incision into Terrace T0 below the modern river. Multiple...

  17. Analysis of nucleation events in the European boundary layer using the regional aerosol–climate model REMO-HAM with a solar radiation-driven OH-proxy

    Directory of Open Access Journals (Sweden)

    J.-P. Pietikäinen

    2014-11-01

    Full Text Available This work describes improvements in the regional aerosol–climate model REMO-HAM in order to simulate more realistically the process of atmospheric new particle formation (NPF. A new scheme was implemented to simulate OH radical concentrations using a proxy approach based on observations and also accounting for the effects of clouds upon OH concentrations. Second, the nucleation rate calculation was modified to directly simulate the formation rates of 3 nm particles, which removes some unnecessary steps in the formation rate calculations used earlier in the model. Using the updated model version, NPF over Europe was simulated for the periods 2003–2004 and 2008–2009. The statistics of the simulated particle formation events were subsequently compared to observations from 13 ground-based measurement sites. The new model shows improved agreement with the observed NPF rates compared to former versions and can simulate the event statistics realistically for most parts of Europe.

  18. Energy and Heat Fluctuations in a Temperature Quench

    Energy Technology Data Exchange (ETDEWEB)

    Zannetti, M.; Corberi, F. [Dipartimento di Fisica “E. Caianiello”, and CNISM, Unità di Salerno, Università di Salerno, via Giovanni Paolo II 132, 84084 Fisciano (Italy); Gonnella, G. [Dipartimento di Fisica, Università di Bari and INFN, Sezione di Bari, via Amendola 173, 70126 Bari (Italy); Piscitelli, A., E-mail: mrc.zannetti@gmail.com, E-mail: corberi@sa.infn.it, E-mail: gonnella@ba.infn.it, E-mail: antps@hotmial.it [Division of Physical Sciences, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, 637371 (Singapore)

    2014-10-15

    Fluctuations of energy and heat are investigated during the relaxation following the instantaneous temperature quench of an extended system. Results are obtained analytically for the Gaussian model and for the large N model quenched below the critical temperature T{sub c}. The main finding is that fluctuations exceeding a critical threshold do condense. Though driven by a mechanism similar to that of Bose—Einstein condensation, this phenomenon is an out-of-equilibrium feature produced by the breaking of energy equipartition occurring in the transient regime. The dynamical nature of the transition is illustrated by phase diagrams extending in the time direction. (general)

  19. Climate-change driven increase in high intensity rainfall events: Analysis of development in the last decades and towards an extrapolation of future progression

    Science.gov (United States)

    Müller, Eva; Pfister, Angela; Gerd, Büger; Maik, Heistermann; Bronstert, Axel

    2015-04-01

    Hydrological extreme events can be triggered by rainfall on different spatiotemporal scales: river floods are typically caused by event durations of between hours and days, while urban flash floods as well as soil erosion or contaminant transport rather result from storms events of very short duration (minutes). Still, the analysis of climate change impacts on rainfall-induced extreme events is usually carried out using daily precipitation data at best. Trend analyses of extreme rainfall at sub-daily or even sub-hourly time scales are rare. In this contribution two lines of research are combined: first, we analyse sub-hourly rainfall data for several decades in three European regions.Second, we investigate the scaling behaviour of heavy short-term precipitation with temperature, i.e. the dependence of high intensity rainfall on the atmospheric temperature at that particular time and location. The trend analysis of high-resolution rainfall data shows for the first time that the frequency of short and intensive storm events in the temperate lowland regions in Germany has increased by up to 0.5 events per year over the last decades. I.e. this trend suggests that the occurrence of these types of storms have multiplied over only a few decades. Parallel to the changes in the rainfall regime, increases in the annual and seasonal average temperature and changes in the occurrence of circulation patterns responsible for the generation of high-intensity storms have been found. The analysis of temporally highly resolved rainfall records from three European regions further indicates that extreme precipitation events are more intense with warmer temperatures during the rainfall event. These observations follow partly the Clausius-Clapeyron relation. Based on this relation one may derive a general rule of maximum rainfall intensity associated to the event temperature, roughly following the Clausius-Clapeyron (CC) relation. This rule might be used for scenarios of future maximum

  20. Magnetic fluctuations associated with density fluctuations in the tokamak edge

    International Nuclear Information System (INIS)

    Kim, Y.J.; Gentle, K.W.; Ritz, C.P.; Rhodes, T.L.; Bengtson, R.D.

    1989-01-01

    Electrostatic density and potential fluctuations occurring with high amplitude near the edge of a tokamak are correlated with components of the fluctuating magnetic field measured outside the limiter radius. It has been established that this turbulence is associated with fluctuations in current as well as density and potential. The correlation extends for substantial toroidal distances, but only if the probes are displaced approximately along field lines, consistent with the short coherence lengths poloidally but long coherence lengths parallel to the field which are characteristic for this turbulence. Furthermore, the correlation can be found only with density fluctuations measured inside the limiter radius; density fluctuations behind the limiter have no detectable magnetic concomitant for the toroidally spaced probes used here. (author). Letter-to-the-editor. 12 refs, 3 figs

  1. UV Screening in Native and Non-native Plant Species in the Tropical Alpine: Implications for Climate Change-Driven Migration of Species to Higher Elevations

    Directory of Open Access Journals (Sweden)

    Paul W. Barnes

    2017-08-01

    Full Text Available Ongoing changes in Earth’s climate are shifting the elevation ranges of many plant species with non-native species often experiencing greater expansion into higher elevations than native species. These climate change-induced shifts in distributions inevitably expose plants to novel biotic and abiotic environments, including altered solar ultraviolet (UV-B (280–315 nm radiation regimes. Do the greater migration potentials of non-native species into higher elevations imply that they have more effective UV-protective mechanisms than native species? In this study, we surveyed leaf epidermal UV-A transmittance (TUV A in a diversity of plant species representing different growth forms to test whether native and non-native species growing above 2800 m elevation on Mauna Kea, Hawaii differed in their UV screening capabilities. We further compared the degree to which TUV A varied along an elevation gradient in the native shrub Vaccinium reticulatum and the introduced forb Verbascum thapsus to evaluate whether these species differed in their abilities to adjust their levels of UV screening in response to elevation changes in UV-B. For plants growing in the Mauna Kea alpine/upper subalpine, we found that adaxial TUV A, measured with a UVA-PAM fluorometer, varied significantly among species but did not differ between native (mean = 6.0%; n = 8 and non-native (mean = 5.8%; n = 11 species. When data were pooled across native and non-native taxa, we also found no significant effect of growth form on TUV A, though woody plants (shrubs and trees were represented solely by native species whereas herbaceous growth forms (grasses and forbs were dominated by non-native species. Along an elevation gradient spanning 2600–3800 m, TUV A was variable (mean range = 6.0–11.2% and strongly correlated with elevation and relative biologically effective UV-B in the exotic V. thapsus; however, TUV A was consistently low (3% and did not vary with elevation in the native

  2. Charge Fluctuations in Nanoscale Capacitors

    NARCIS (Netherlands)

    Limmer, D.T.; Merlet, C.; Salanne, M.; Chandler, D.; Madden, P.A.; van Roij, R.H.H.G.; Rotenberg, B.

    2013-01-01

    The fluctuations of the charge on an electrode contain information on the microscopic correlations within the adjacent fluid and their effect on the electronic properties of the interface. We investigate these fluctuations using molecular dynamics simulations in a constant-potential ensemble with

  3. Fluctuating attention in Parkinson's disease

    DEFF Research Database (Denmark)

    Starrfelt, Randi; Aarsland, Dag; Janvin, Carmen

    2001-01-01

    Lewy body dementia (DLB), which share many clinical and pathological features with Parkinson’s disease (PD), is charac- terised by marked fluctuations in cognition and consciousness. Fluctuating cognition has not been formally studied in PD, although some studies indicate that PD patients show...

  4. On the origin of shape fluctuations of the cell nucleus.

    Science.gov (United States)

    Chu, Fang-Yi; Haley, Shannon C; Zidovska, Alexandra

    2017-09-26

    The nuclear envelope (NE) presents a physical boundary between the cytoplasm and the nucleoplasm, sandwiched in between two highly active systems inside the cell: cytoskeleton and chromatin. NE defines the shape and size of the cell nucleus, which increases during the cell cycle, accommodating for chromosome decondensation followed by genome duplication. In this work, we study nuclear shape fluctuations at short time scales of seconds in human cells. Using spinning disk confocal microscopy, we observe fast fluctuations of the NE, visualized by fluorescently labeled lamin A, and of the chromatin globule surface (CGS) underneath the NE, visualized by fluorescently labeled histone H2B. Our findings reveal that fluctuation amplitudes of both CGS and NE monotonously decrease during the cell cycle, serving as a reliable cell cycle stage indicator. Remarkably, we find that, while CGS and NE typically fluctuate in phase, they do exhibit localized regions of out-of-phase motion, which lead to separation of NE and CGS. To explore the mechanism behind these shape fluctuations, we use biochemical perturbations. We find the shape fluctuations of CGS and NE to be both thermally and actively driven, the latter caused by forces from chromatin and cytoskeleton. Such undulations might affect gene regulation as well as contribute to the anomalously high rates of nuclear transport by, e.g., stirring of molecules next to NE, or increasing flux of molecules through the nuclear pores.

  5. Climate-driven changes in life-history traits of the bastard grunt (Pomadasys incisus in the north-western Mediterranean

    Directory of Open Access Journals (Sweden)

    H. VILLEGAS-HERNÁNDEZ

    2014-07-01

    Full Text Available This study evaluates the influence of sea water temperature on the life-history traits of the thermophilic bastard grunt Pomadasys incisus in the Catalan coast. We compared two key traits of this species, condition and reproduction, from populations in two separate areas with different thermal regimes: the Gulf of Roses (cold area and the Ebre Delta (warm area. Specimens were collected monthly from each area between 2010 and 2012. The results were also compared with those given in the literature from sites where the species is more common, i.e. the southern Mediterranean and eastern Atlantic. Our findings indicate that, compared to the populations in warmer environments, the population inhabiting the colder waters appears to be in significantly poorer condition and there is some deviance in their life-history traits: egg size and quality being traded-off for higher egg numbers; lower lengths at maturity and alterations to spawning phenology. A certain degree of plasticity in life-history traits may favour the process of expansion and establishment of this thermophilic species into newly available but colder habitats of the north-western Mediterranean under a scenario of climate change.

  6. Increased dissolved organic carbon (DOC) in Central European streams is driven by reductions in ionic strength rather than climate change or decreasing acidity.

    Science.gov (United States)

    Hruska, Jakub; Krám, Pavel; McDowell, William H; Oulehle, Filip

    2009-06-15

    Temporal trends in DOC concentration and flux were investigated at two geochemically distinct forested catchments in western Czech Republic. Mean discharge-weighted DOC concentrations averaged 18.8 mg L(-1) at the acidic Lysina catchment, and 20.2 mg L(-1) at base-rich and well-buffered Pluhuv Bor. Between 1993 and 2007 DOC in streamwater increased significantly in both catchments: the mean annual increase was 0.42 mg L(-1) yr(-1) (p DOC were correlated with only modest increases in stream pH in both catchments, but large declines in ionic strength (IS), that resulted from declining atmospheric deposition. Neither catchment has undergone changes in soil-water pH, yet DOC concentrations tripled in the soil-water of both catchments. We conclude that changes in ionic strength of soil-water and streamwater, rather than acidity, are the primary drivers of changes in streamwater DOC in this region. Temperature, precipitation and discharge show no statistically significant trends during the study period, suggesting that climate change has played no role in the changes in DOC that we have observed.

  7. Quantum fluctuations from thermal fluctuations in Jacobson formalism

    Energy Technology Data Exchange (ETDEWEB)

    Faizal, Mir [University of British Columbia-Okanagan, Irving K. Barber School of Arts and Sciences, Kelowna, BC (Canada); University of Lethbridge, Department of Physics and Astronomy, Lethbridge, AB (Canada); Ashour, Amani; Alcheikh, Mohammad [Damascus University, Mathematics Department, Faculty of Science, Damascus (Syrian Arab Republic); Alasfar, Lina [Universite Clermont Auvergne, Laboratoire de Physique Corpusculaire de Clermont-Ferrand, Aubiere (France); Alsaleh, Salwa; Mahroussah, Ahmed [King Saud University, Department of Physics and Astronomy, Riyadh (Saudi Arabia)

    2017-09-15

    In the Jacobson formalism general relativity is obtained from thermodynamics. This is done by using the Bekenstein-Hawking entropy-area relation. However, as a black hole gets smaller, its temperature will increase. This will cause the thermal fluctuations to also increase, and these will in turn correct the Bekenstein-Hawking entropy-area relation. Furthermore, with the reduction in the size of the black hole, quantum effects will also start to dominate. Just as the general relativity can be obtained from thermodynamics in the Jacobson formalism, we propose that the quantum fluctuations to the geometry can be obtained from thermal fluctuations. (orig.)

  8. Climate change and wildfires

    Science.gov (United States)

    William J. De Groot; Michael D. Flannigan; Brian J. Stocks

    2013-01-01

    Wildland fire regimes are primarily driven by climate/weather, fuels and people. All of these factors are dynamic and their variable interactions create a mosaic of fire regimes around the world. Climate change will have a substantial impact on future fire regimes in many global regions. Current research suggests a general increase in area burned and fire occurrence...

  9. Leggett-Garg Inequalities for Quantum Fluctuating Work

    Directory of Open Access Journals (Sweden)

    Harry J. D. Miller

    2018-03-01

    Full Text Available The Leggett-Garg inequalities serve to test whether or not quantum correlations in time can be explained within a classical macrorealistic framework. We apply this test to thermodynamics and derive a set of Leggett-Garg inequalities for the statistics of fluctuating work done on a quantum system unitarily driven in time. It is shown that these inequalities can be violated in a driven two-level system, thereby demonstrating that there exists no general macrorealistic description of quantum work. These violations are shown to emerge within the standard Two-Projective-Measurement scheme as well as for alternative definitions of fluctuating work that are based on weak measurement. Our results elucidate the influences of temporal correlations on work extraction in the quantum regime and highlight a key difference between quantum and classical thermodynamics.

  10. Fluctuations of inflationary magnetogenesis

    CERN Document Server

    Giovannini, Massimo

    2013-01-01

    This analysis aims at exploring what can be said about the growth rate of magnetized inhomogeneities under two concurrent hypotheses: a phase of quasi-de Sitter dynamics driven by a single inflaton field and the simultaneous presence of a spectator field coupled to gravity and to the gauge sector. Instead of invoking ad hoc correlations between the various components, the system of scalar inhomogeneities is diagonalized in terms of two gauge-invariant quasi-normal modes whose weighted sum gives the curvature perturbations on comoving orthogonal hypersurfaces. The predominance of the conventional adiabatic scalar mode implies that the growth rate of magnetized inhomogeneities must not exceed 2.2 in Hubble units if the conventional inflationary phase is to last about 70 efolds and for a range of slow roll parameters between 0.1 and 0.001. Longer and shorter durations of the quasi-de Sitter stage lead, respectively, either to tighter or to looser bounds which are anyway more constraining than the standard backre...

  11. Towards uncovering the structure of power fluctuations of wind farms.

    Science.gov (United States)

    Liu, Huiwen; Jin, Yaqing; Tobin, Nicolas; Chamorro, Leonardo P

    2017-12-01

    The structure of the turbulence-driven power fluctuations in a wind farm is fundamentally described from basic concepts. A derived tuning-free model, supported with experiments, reveals the underlying spectral content of the power fluctuations of a wind farm. It contains two power-law trends and oscillations in the relatively low- and high-frequency ranges. The former is mostly due to the turbulent interaction between the flow and the turbine properties, whereas the latter is due to the advection between turbine pairs. The spectral wind-farm scale power fluctuations Φ_{P} exhibit a power-law decay proportional to f^{-5/3-2} in the region corresponding to the turbulence inertial subrange and at relatively large scales, Φ_{P}∼f^{-2}. Due to the advection and turbulent diffusion of large-scale structures, a spectral oscillation exists with the product of a sinusoidal behavior and an exponential decay in the frequency domain.

  12. Current density fluctuations and ambipolarity of transport

    International Nuclear Information System (INIS)

    Shen, W.; Dexter, R.N.; Prager, S.C.

    1991-10-01

    The fluctuation in the plasma current density is measured in the MIST reversed field pinch experiment. Such fluctuations, and the measured radial profile of the k spectrum of magnetic fluctuations, supports the view and that low frequency fluctuations (f r >) demonstrates that radial particle transport from particle motion parallel to a fluctuating magnetic field is ambipolar over the full frequency range

  13. Dengue outlook for the World Cup in Brazil: an early warning model framework driven by real-time seasonal climate forecasts.

    Science.gov (United States)

    Lowe, Rachel; Barcellos, Christovam; Coelho, Caio A S; Bailey, Trevor C; Coelho, Giovanini Evelim; Graham, Richard; Jupp, Tim; Ramalho, Walter Massa; Carvalho, Marilia Sá; Stephenson, David B; Rodó, Xavier

    2014-07-01

    With more than a million spectators expected to travel among 12 different cities in Brazil during the football World Cup, June 12-July 13, 2014, the risk of the mosquito-transmitted disease dengue fever is a concern. We addressed the potential for a dengue epidemic during the tournament, using a probabilistic forecast of dengue risk for the 553 microregions of Brazil, with risk level warnings for the 12 cities where matches will be played. We obtained real-time seasonal climate forecasts from several international sources (European Centre for Medium-Range Weather Forecasts [ECMWF], Met Office, Meteo-France and Centro de Previsão de Tempo e Estudos Climáticos [CPTEC]) and the observed dengue epidemiological situation in Brazil at the forecast issue date as provided by the Ministry of Health. Using this information we devised a spatiotemporal hierarchical Bayesian modelling framework that enabled dengue warnings to be made 3 months ahead. By assessing the past performance of the forecasting system using observed dengue incidence rates for June, 2000-2013, we identified optimum trigger alert thresholds for scenarios of medium-risk and high-risk of dengue. Our forecasts for June, 2014, showed that dengue risk was likely to be low in the host cities Brasília, Cuiabá, Curitiba, Porto Alegre, and São Paulo. The risk was medium in Rio de Janeiro, Belo Horizonte, Salvador, and Manaus. High-risk alerts were triggered for the northeastern cities of Recife (p(high)=19%), Fortaleza (p(high)=46%), and Natal (p(high)=48%). For these high-risk areas, particularly Natal, the forecasting system did well for previous years (in June, 2000-13). This timely dengue early warning permits the Ministry of Health and local authorities to implement appropriate, city-specific mitigation and control actions ahead of the World Cup. European Commission's Seventh Framework Research Programme projects DENFREE, EUPORIAS, and SPECS; Conselho Nacional de Desenvolvimento Científico e Tecnol

  14. What Drives Farmers to Make Top-Down or Bottom-Up Adaptation to Climate Change and Fluctuations? A Comparative Study on 3 Cases of Apple Farming in Japan and South Africa

    Science.gov (United States)

    Fujisawa, Mariko; Kobayashi, Kazuhiko; Johnston, Peter; New, Mark

    2015-01-01

    Agriculture is one of the most vulnerable sectors to climate change. Farmers have been exposed to multiple stressors including climate change, and they have managed to adapt to those risks. The adaptation actions undertaken by farmers and their decision making are, however, only poorly understood. By studying adaptation practices undertaken by apple farmers in three regions: Nagano and Kazuno in Japan and Elgin in South Africa, we categorize the adaptation actions into two types: farmer initiated bottom-up adaptation and institution led top-down adaptation. We found that the driver which differentiates the type of adaptation likely adopted was strongly related to the farmers’ characteristics, particularly their dependence on the institutions, e.g. the farmers’ cooperative, in selling their products. The farmers who rely on the farmers’ cooperative for their sales are likely to adopt the institution-led adaptation, whereas the farmers who have established their own sales channels tend to start innovative actions by bottom-up. We further argue that even though the two types have contrasting features, the combinations of the both types of adaptations could lead to more successful adaptation particularly in agriculture. This study also emphasizes that more farm-level studies for various crops and regions are warranted to provide substantial feedbacks to adaptation policy. PMID:25822534

  15. What drives farmers to make top-down or bottom-up adaptation to climate change and fluctuations? A comparative study on 3 cases of apple farming in Japan and South Africa.

    Directory of Open Access Journals (Sweden)

    Mariko Fujisawa

    Full Text Available Agriculture is one of the most vulnerable sectors to climate change. Farmers have been exposed to multiple stressors including climate change, and they have managed to adapt to those risks. The adaptation actions undertaken by farmers and their decision making are, however, only poorly understood. By studying adaptation practices undertaken by apple farmers in three regions: Nagano and Kazuno in Japan and Elgin in South Africa, we categorize the adaptation actions into two types: farmer initiated bottom-up adaptation and institution led top-down adaptation. We found that the driver which differentiates the type of adaptation likely adopted was strongly related to the farmers' characteristics, particularly their dependence on the institutions, e.g. the farmers' cooperative, in selling their products. The farmers who rely on the farmers' cooperative for their sales are likely to adopt the institution-led adaptation, whereas the farmers who have established their own sales channels tend to start innovative actions by bottom-up. We further argue that even though the two types have contrasting features, the combinations of the both types of adaptations could lead to more successful adaptation particularly in agriculture. This study also emphasizes that more farm-level studies for various crops and regions are warranted to provide substantial feedbacks to adaptation policy.

  16. Modification of boundary fluctuations by LHCD in the HT-7 tokamak

    International Nuclear Information System (INIS)

    Song Mei; Wan Baonian; Xu Guosheng; Ling Bili

    2003-01-01

    Measurements of boundary fluctuations and fluctuation driven electron fluxes have been performed in ohmic and lower hybrid current drive enhanced confinement plasma using a graphite Langmuir probe array on HT-7 tokamak. The fluctuations are significantly suppressed and the turbulent fluxes are remarkably depressed in the enhanced plasma. We characterized the statistical properties of fluctuations and the particle flux and found a non-Gaussian character in the whole scrape-off layer with minimum deviations from Gaussian in the proximity of the velocity shear layer in ohmic plasma. In the enhanced plasma the deviations in the boundary region are all reduces obviously. The fluctuations and induced electron fluxes show sporadic bursts asymmetric in time and the asymmetry is remarkably weakened in the lower hybrid current driving (LHCD) phase. The results suggest a coupling between the statistical behaviour of fluctuations and the turbulent flow

  17. Near resonant absorption by atoms in intense, fluctuating fields: [Progress report

    International Nuclear Information System (INIS)

    1989-01-01

    During the present grant period preparations for photon echo studies of the role of phase fluctuations of an optical driving field resonant with the 1 S 0 - 3 P 1 transition in 174 Yb are moving forward. This experimental study emphasizes the role of fluctuations as a decorrelating mechanism on a phased array of excited atoms. Improvements in laser stabilization and in the quality of the fluctuation spectrum have been carried out and the first spectroscopic measurements will be carried out during this grant year. In response to an important recent theoretical study we have also applied the phase fluctuation synthesizing capability to the study of the atomic sodium resonance fluorescence line profile, driven by a phase fluctuating laser. The measured fluctuations in the fluorescence, characterized in terms of the standard deviation of the fluorescence intensity, have an unexpected and strong dependence on detuning of the driving laser

  18. Fluctuations When Driving Between Nonequilibrium Steady States

    Science.gov (United States)

    Riechers, Paul M.; Crutchfield, James P.

    2017-08-01

    Maintained by environmental fluxes, biological systems are thermodynamic processes that operate far from equilibrium without detailed-balanced dynamics. Yet, they often exhibit well defined nonequilibrium steady states (NESSs). More importantly, critical thermodynamic functionality arises directly from transitions among their NESSs, driven by environmental switching. Here, we identify the constraints on excess heat and dissipated work necessary to control a system that is kept far from equilibrium by background, uncontrolled "housekeeping" forces. We do this by extending the Crooks fluctuation theorem to transitions among NESSs, without invoking an unphysical dual dynamics. This and corresponding integral fluctuation theorems determine how much work must be expended when controlling systems maintained far from equilibrium. This generalizes thermodynamic feedback control theory, showing that Maxwellian Demons can leverage mesoscopic-state information to take advantage of the excess energetics in NESS transitions. We also generalize an approach recently used to determine the work dissipated when driving between functionally relevant configurations of an active energy-consuming complex system. Altogether, these results highlight universal thermodynamic laws that apply to the accessible degrees of freedom within the effective dynamic at any emergent level of hierarchical organization. By way of illustration, we analyze a voltage-gated sodium ion channel whose molecular conformational dynamics play a critical functional role in propagating action potentials in mammalian neuronal membranes.

  19. Atlantic multidecadal oceanic variability and its influence on the atmosphere in a climate model

    Energy Technology Data Exchange (ETDEWEB)

    Msadek, Rym; Frankignoul, Claude [Universite Pierre et Marie Curie, Paris 6, LOCEAN/IPSL, Paris (France)

    2009-07-15

    The mechanisms controlling the decadal to multidecadal variability of the Atlantic Meridional Overturning Circulation (MOC) and its influence on the atmosphere are investigated using a control simulation with the IPSL-CM4 climate model. The multidecadal fluctuations of the MOC are mostly driven by deep convection in the subpolar gyre, which occurs south of Iceland in the model. The latter is primarily influenced by the anomalous advection of salinity due to changes in the East Atlantic Pattern (EAP), which is the second mode of atmospheric variability in the North Atlantic region. The North Atlantic Oscillation is the dominant mode, but it plays a secondary role in the MOC fluctuations. During summer, the MOC variability is shown to have a significant impact on the atmosphere in the North Atlantic-European sector. The MOC influence is due to an interhemispheric sea surface temperature (SST) anomaly with opposite signs in the two hemispheres but largest amplitude in the northern one. The SST pattern driven by the MOC mostly resembles the model Atlantic Multidecadal Oscillation (AMO) and bears some similarity with the observed one. It is shown that the AMO reflects both the MOC influence and the local atmospheric forcing. Hence, the MOC influence on climate is best detected using lagged relations between climatic fields. The atmospheric response resembles the EAP, in a phase that might induce a weak positive feedback on the MOC. (orig.)

  20. Holocene sea-level fluctuation in the southern hemisphere

    Science.gov (United States)

    Isla, Federico Ignacio

    If rising sea levels dominate in the northern hemisphere (NH), falling or fluctuating sea levels predominate in the southern hemisphere (SH). Endogenic processes (tectonics, isostasy or geoidal changes) could explain local or regional mean sea level (MSL) fluctuations but not an hemispherical one. Evidence from South America, Africa, Antarctica, Australia and the Pacific and Indian Oceans suggest that the Holocene transgression rose above the present MSL, in higher latitudes before the tropics. By plotting latitude against the age of MSL arrival at present coasts, good correlation is observed. Oceanic salinity mixing has been already proposed to explain this mid-Holocene sea-level fluctuation. Climate could be the only factor responsible for this hemisphere-wide behavior of MSL. It has been suggested previously that the climate of the SH precedes that of the NH by 3000 years. The climatic optimum, or maximum warmth, occurred predominantly about 6000 BP in the NH, but about 10-9000 BP in the SH. Short-term climatic effects on the sea level (monsoons, southern oscillation/El Niño phenomena) should have significant occurrences during the past in the windiest oceanic hemisphere. This latitudinal trend in former MSL should be considered when using shorelines as reference points for measuring vertical crustal movements.

  1. Do interactions of land use and climate affect productivity of waterbirds and prairie-pothole wetlands?

    Science.gov (United States)

    Anteau, Michael J.

    2012-01-01

    Availability of aquatic invertebrates on migration and breeding areas influences recruitment of ducks and shorebirds. In wetlands of Prairie Pothole Region (PPR), aquatic invertebrate production primarily is driven by interannual fluctuations of water levels in response to wet-dry cycles in climate. However, this understanding comes from studying basins that are minimally impacted by agricultural landscape modifications. In the past 100–150 years, a large proportion of wetlands within the PPR have been altered; often water was drained from smaller to larger wetlands at lower elevations creating consolidated, interconnected basins. Here I present a case study and I hypothesize that large basins receiving inflow from consolidation drainage have reduced water-level fluctuations in response to climate cycles than those in undrained landscapes, resulting in relatively stable wetlands that have lower densities of invertebrate forage for ducks and shorebirds and also less foraging habitat, especially for shorebirds. Furthermore, stable water-levels and interconnected basins may favor introduced or invasive species (e.g., cattail [Typha spp.] or fish) because native communities "evolved" in a dynamic and isolated system. Accordingly, understanding interactions between water-level fluctuations and landscape modifications is a prerequisite step to modeling effects of climate change on wetland hydrology and productivity and concomitant recruitment of waterbirds.

  2. Localized description of valence fluctuations

    International Nuclear Information System (INIS)

    Alascio, B.; Allub, R.; Aligia, A.

    1979-07-01

    The authors set up a model for intermediate valence equivalent to the ''atomic'' limit of the Anderson Hamiltonian. Detailed analysis of this model shows that most of the essential characteristics of valence fluctuators are already present in this crudely simplified Hamiltonian. The spin-spin and the 4f charge-charge correlation functions are studied and it is shown that it is possible to define a spin fluctuation frequency ωsub(s.f.) and a charge fluctuation frequency ωsub(ch.f.).ωsub(s.f.) and ωsub(ch.f.) can differ considerably for some values of the parameters of the model. The magnetic susceptibility and the specific heat are calculated as functions of temperature and it is shown how the results simulate the behaviour found in valence fluctuators. (author)

  3. The Fluctuation Niche in Plants

    Directory of Open Access Journals (Sweden)

    Jaume Terradas

    2009-01-01

    Full Text Available Classical approaches to niche in coexisting plants have undervalued temporal fluctuations. We propose that fluctuation niche is an important dimension of the total niche and interacts with habitat and life-history niches to provide a better understanding of the multidimensional niche space where ecological interactions occur. To scale a fluctuation niche, it is necessary to relate environmental constrictions or species performance not only to the absolute values of the usual environmental and ecophysiological variables but also to their variances or other measures of variability. We use Mediterranean plant communities as examples, because they present characteristic large seasonal and interannual fluctuations in water and nutrient availabilities, along an episodic-constant gradient, and because the plant responses include a number of syndromes coupled to this gradient.

  4. The Fluctuation Niche in Plants

    International Nuclear Information System (INIS)

    Terradas, J.; Penuelas, J.; Lloret, F.; Penuelas, J.

    2009-01-01

    Classical approaches to niche in coexisting plants have undervalued temporal fluctuations. We propose that fluctuation niche is an important dimension of the total niche and interacts with habitat and life-history niches to provide a better understanding of the multidimensional niche space where ecological interactions occur. To scale a fluctuation niche, it is necessary to relate environmental constrictions or species performance not only to the absolute values of the usual environmental and eco physiological variables but also to their variances or other measures of variability. We use Mediterranean plant communities as examples, because they present characteristic large seasonal and inter annual fluctuations in water and nutrient availabilities, along an episodic-constant gradient, and because the plant responses include a number of syndromes coupled to this gradient.

  5. Quantum fluctuations in insulating ferroelectrics

    International Nuclear Information System (INIS)

    Riseborough, Peter S.

    2010-01-01

    Graphical abstract: It has been proposed that in a ferroelectric insulator, an applied magnetic field may couple the transverse phonon modes and produce left and right circularly polarized phonon modes which are no longer degenerate. We quantize the theory and examine the effects of quantal fluctuations. In particular, we show that the zero point fluctuations result in a large diamagnetic contribution to the magnetic susceptibility. - Abstract: It has been proposed that in a ferroelectric insulator, an applied magnetic field may couple the transverse phonon modes and produce left and right circularly polarized phonon modes which are no longer degenerate. We quantize the theory and examine the effects of quantal fluctuations. In particular, we show that the zero-point fluctuations result in a large diamagnetic contribution to the magnetic susceptibility.

  6. Fluctuations and Instability in Sedimentation

    KAUST Repository

    Guazzelli, Élisabeth

    2011-01-21

    This review concentrates on the fluctuations of the velocities of sedimenting spheres, and on the structural instability of a suspension of settling fibers. For many years, theoretical estimates and numerical simulations predicted the fluctuations of the velocities of spheres to increase with the size of the container, whereas experiments found no such variation. Two ideas have increased our understanding. First, the correlation length of the velocity fluctuations was found experimentally to be 20 interparticle separations. Second, in dilute suspensions, a vertical variation in the concentration due to the spreading of the front with the clear fluid can inhibit the velocity fluctuations. In a very dilute regime, a homogeneous suspension of fibers suffers a spontaneous instability in which fast descending fiber-rich columns are separated by rising fiber-sparse columns. In a semidilute regime, the settling is hindered, more so than for spheres. © 2011 by Annual Reviews. All rights reserved.

  7. Revisiting the evolutionary events in Allium subgenus Cyathophora (Amaryllidaceae): Insights into the effect of the Hengduan Mountains Region (HMR) uplift and Quaternary climatic fluctuations to the environmental changes in the Qinghai-Tibet Plateau.

    Science.gov (United States)

    Li, Min-Jie; Tan, Jin-Bo; Xie, Deng-Feng; Huang, De-Qing; Gao, Yun-Dong; He, Xing-Jin

    2016-01-01

    The respective roles that the Hengduan Mountains Region (HMR) uplift around 4-3 Ma and Quaternary climatic oscillations played in causing the environmental changes in the Qinghai-Tibet Plateau (QTP) remain unknown. Here, we reconstruct the evolutionary history of two varieties of Allium cyathophorum and A. spicatum of subgenus Cyathophora, restricted to the HMR and the western QTP, respectively. Forty-five populations were surveyed for chloroplast and nuclear sequence variation to evaluate phylogenetic relationships, dates of divergence and ancestral area/inflorescence reconstructions. In addition, analyses were conducted on discernable micromorphologies, cytotypes and seed size variation. Our results indicated that two varieties of A. cyathophorum are separate species, i.e. A. farreri and A. cyathophorum, and the initial split of Cyathophora was triggered by the HMR uplift around 4-3 Ma. Subsequently, A. spicatum originated through the strengthened aridification in the western QTP induced vicariance of the ancestral populations in the HMR during the early Pleistocene. A self-sustaining allotetraploid species from A. farreri and A. cyathophorum was established during an interglacial period of penultimate glaciation of the QTP. Seed size variation also supports these by the colonization-competition tradeoff among small and large seeds. Our findings appear to suggest that the HMR uplift could have strengthened the development of the Asian monsoon regimes in this region and aridification in the western QTP, while the Quaternary climatic oscillations spurred the allopatric species' range shifts and created new open microhabitat for the alloploid species. Copyright © 2015 Elsevier Inc. All rights reserved.

  8. Principle of minimal work fluctuations.

    Science.gov (United States)

    Xiao, Gaoyang; Gong, Jiangbin

    2015-08-01

    Understanding and manipulating work fluctuations in microscale and nanoscale systems are of both fundamental and practical interest. For example, in considering the Jarzynski equality 〈e-βW〉=e-βΔF, a change in the fluctuations of e-βW may impact how rapidly the statistical average of e-βW converges towards the theoretical value e-βΔF, where W is the work, β is the inverse temperature, and ΔF is the free energy difference between two equilibrium states. Motivated by our previous study aiming at the suppression of work fluctuations, here we obtain a principle of minimal work fluctuations. In brief, adiabatic processes as treated in quantum and classical adiabatic theorems yield the minimal fluctuations in e-βW. In the quantum domain, if a system initially prepared at thermal equilibrium is subjected to a work protocol but isolated from a bath during the time evolution, then a quantum adiabatic process without energy level crossing (or an assisted adiabatic process reaching the same final states as in a conventional adiabatic process) yields the minimal fluctuations in e-βW, where W is the quantum work defined by two energy measurements at the beginning and at the end of the process. In the classical domain where the classical work protocol is realizable by an adiabatic process, then the classical adiabatic process also yields the minimal fluctuations in e-βW. Numerical experiments based on a Landau-Zener process confirm our theory in the quantum domain, and our theory in the classical domain explains our previous numerical findings regarding the suppression of classical work fluctuations [G. Y. Xiao and J. B. Gong, Phys. Rev. E 90, 052132 (2014)].

  9. Redox Fluctuations Increase the Contribution of Lignin to Soil Respiration

    Science.gov (United States)

    Hall, S. J.; Silver, W. L.; Timokhin, V.; Hammel, K.

    2014-12-01

    Lignin mineralization represents a critical flux in the terrestrial carbon (C) cycle, yet little is known about mechanisms and environmental factors controlling lignin breakdown in mineral soils. Hypoxia has long been thought to suppress lignin decomposition, yet variation in oxygen (O2) availability in surface soils accompanying moisture fluctuations could potentially stimulate this process by generating reactive oxygen species via coupled biotic and abiotic iron (Fe) redox cycling. Here, we tested the impact of redox fluctuations on lignin breakdown in humid tropical forest soils during ten-week laboratory incubations. We used synthetic lignins labeled with 13C in either of two positions (aromatic methoxyl and propyl Cβ) to provide highly sensitive and specific measures of lignin mineralization not previously employed in soils. Four-day redox fluctuations increased the percent contribution of methoxyl C to soil respiration, and cumulative methoxyl C mineralization was equivalent under static aerobic and fluctuating redox conditions despite lower total C mineralization in the latter treatment. Contributions of the highly stable Cβ to mineralization were also equivalent in static aerobic and fluctuating redox treatments during periods of O2 exposure, and nearly doubled in the fluctuating treatment after normalizing to cumulative O2 exposure. Oxygen fluctuations drove substantial net Fe reduction and oxidation, implying that reactive oxygen species generated during abiotic Fe oxidation likely contributed to the elevated contribution of lignin to C mineralization. Iron redox cycling provides a mechanism for lignin breakdown in soils that experience conditions unfavorable for canonical lignin-degrading organisms, and provides a potential mechanism for lignin depletion in soil organic matter during late-stage decomposition. Thus, close couplings between soil moisture, redox fluctuations, and lignin breakdown provide potential a link between climate variability and

  10. Predicting impacts of climate change on Fasciola hepatica risk.

    Science.gov (United States)

    Fox, Naomi J; White, Piran C L; McClean, Colin J; Marion, Glenn; Evans, Andy; Hutchings, Michael R

    2011-01-10

    Fasciola hepatica (liver fluke) is a physically and economically devastating parasitic trematode whose rise in recent years has been attributed to climate change. Climate has an impact on the free-living stages of the parasite and its intermediate host Lymnaea truncatula, with the interactions between rainfall and temperature having the greatest influence on transmission efficacy. There have been a number of short term climate driven forecasts developed to predict the following season's infection risk, with the Ollerenshaw index being the most widely used. Through the synthesis of a modified Ollerenshaw index with the UKCP09 fine scale climate projection data we have developed long term seasonal risk forecasts up to 2070 at a 25 km square resolution. Additionally UKCIP gridded datasets at 5 km square resolution from 1970-2006 were used to highlight the climate-driven increase to date. The maps show unprecedented levels of future fasciolosis risk in parts of the UK, with risk of serious epidemics in Wales by 2050. The seasonal risk maps demonstrate the possible change in the timing of disease outbreaks due to increased risk from overwintering larvae. Despite an overall long term increase in all regions of the UK, spatio-temporal variation in risk levels is expected. Infection risk will reduce in some areas and fluctuate greatly in others with a predicted decrease in summer infection for parts of the UK due to restricted water availability. This forecast is the first approximation of the potential impacts of climate change on fasciolosis risk in the UK. It can be used as a basis for indicating where active disease surveillance should be targeted and where the development of improved mitigation or adaptation measures is likely to bring the greatest benefits.

  11. Predicting impacts of climate change on Fasciola hepatica risk.

    Directory of Open Access Journals (Sweden)

    Naomi J Fox

    2011-01-01

    Full Text Available Fasciola hepatica (liver fluke is a physically and economically devastating parasitic trematode whose rise in recent years has been attributed to climate change. Climate has an impact on the free-living stages of the parasite and its intermediate host Lymnaea truncatula, with the interactions between rainfall and temperature having the greatest influence on transmission efficacy. There have been a number of short term climate driven forecasts developed to predict the following season's infection risk, with the Ollerenshaw index being the most widely used. Through the synthesis of a modified Ollerenshaw index with the UKCP09 fine scale climate projection data we have developed long term seasonal risk forecasts up to 2070 at a 25 km square resolution. Additionally UKCIP gridded datasets at 5 km square resolution from 1970-2006 were used to highlight the climate-driven increase to date. The maps show unprecedented levels of future fasciolosis risk in parts of the UK, with risk of serious epidemics in Wales by 2050. The seasonal risk maps demonstrate the possible change in the timing of disease outbreaks due to increased risk from overwintering larvae. Despite an overall long term increase in all regions of the UK, spatio-temporal variation in risk levels is expected. Infection risk will reduce in some areas and fluctuate greatly in others with a predicted decrease in summer infection for parts of the UK due to restricted water availability. This forecast is the first approximation of the potential impacts of climate change on fasciolosis risk in the UK. It can be used as a basis for indicating where active disease surveillance should be targeted and where the development of improved mitigation or adaptation measures is likely to bring the greatest benefits.

  12. Man-Made Climatic Changes

    Science.gov (United States)

    Landsberg, Helmut E.

    1970-01-01

    Reviews environmental studies which show that national climatic fluctuations vary over a wide range. Solar radiation, earth temperatures, precipitation, atmospheric gases and suspended particulates are discussed in relation to urban and extraurban effects. Local weather modifications and attempts at climate control by man seem to have substantial…

  13. Fluctuating selection on basal metabolic rate.

    Science.gov (United States)

    Nilsson, Johan F; Nilsson, Jan-Åke

    2016-02-01

    BMR (Basal metabolic rate) is an important trait in animal life history as it represents a significant part of animal energy budgets. BMR has also been shown to be positively related to sustainable work rate and maximal thermoregulatory capacity. To this date, most of the studies have focused on the causes of interspecific and intraspecific variation in BMR, and fairly little is known about the fitness consequences of different metabolic strategies. In this study, we show that winter BMR affects local survival in a population of wild blue tits (Cyanistes caeruleus), but that the selection direction differs between years. We argue that this fluctuating selection is probably a consequence of varying winter climate with a positive relation between survival and BMR during cold and harsh conditions, but a negative relation during mild winters. This fluctuating selection can not only explain the pronounced variation in BMR in wild populations, but will also give us new insights into how energy turnover rates can shape the life-history strategies of animals. Furthermore, the study shows that the process of global warming may cause directional selection for a general reduction in BMR, affecting the general life-history strategy on the population level.

  14. Fluctuation analysis of rotational spectra

    International Nuclear Information System (INIS)

    Doessing, T.; Bracco, A.; Broglia, R.A.; Matsuo, M.

    1996-01-01

    The compound state rotational degree of freedom is ''damped'' in the sense that the electric quadrupole decay of a single quantum state with angular momentum I exhibits a spectrum of final states all having spin I-2. In actual experiments, the cascade of γ-rays associated with each of the members of the ensemble of compound nuclei uses each of the ''discrete'' transitions many more times than the ''continuum'' transitions. Relatively large and small fluctuations in the recorded coincidence spectrum ensue, respectively. The analysis of the fluctuations will be shown to be instrumental to gain insight into the phenomenon of rotational damping. For this purpose, two- and higher-fold coincidence spectra emitted from rotating nuclei are analyzed with respect to the count fluctuations. The coincidences from consecutive γ-rays emitted from discrete rotational bands generate ridges in the E γ1 .E γ2 spectrum, and the fluctuation analysis of the ridges is based upon the ansatz of a random selection of transition energies from band to band. This ansatz is supported by a cranked mean-field calculation for the nucleus 168 Yb, as well as by analyzing resolved bands in 168 Yb and its neighbors. The fluctuation analysis of the central valley (E γ1 =E γ2 ) is based upon the ansatz of fluctuations in the intensity of the transitions of Porter-Thomas type superposed on a smooth spectrum of transition energies. This ansatz is again supported by a mixed-band calculation. The mathematical treatment of count fluctuations is formulated in general (orig.)

  15. Beyond Tree Throw: Wind, Water, Rock and the Mechanics of Tree-Driven Bedrock Physical Weathering

    Science.gov (United States)

    Marshall, J. A.; Anderson, R. S.; Dawson, T. E.; Dietrich, W. E.; Minear, J. T.

    2017-12-01

    Tree throw is often invoked as the dominant process in converting bedrock to soil and thus helping to build the Critical Zone (CZ). In addition, observations of tree roots lifting sidewalk slabs, occupying cracks, and prying slabs of rock from cliff faces have led to a general belief in the power of plant growth forces. These common observations have led to conceptual models with trees at the center of the soil genesis process. This is despite the observation that tree throw is rare in many forested settings, and a dearth of field measurements that quantify the magnitude of growth forces. While few trees blow down, every tree grows roots, inserting many tens of percent of its mass below ground. Yet we lack data quantifying the role of trees in both damaging bedrock and detaching it (and thus producing soil). By combing force measurements at the tree-bedrock interface with precipitation, solar radiation, wind speed, and wind-driven tree sway data we quantified the magnitude and frequency of tree-driven soil-production mechanisms from two contrasting climatic and lithologic regimes (Boulder and Eel Creek CZ Observatories). Preliminary data suggests that in settings with relatively thin soils, trees can damage and detach rock due to diurnal fluctuations, wind response and rainfall events. Surprisingly, our data suggests that forces from roots and trunks growing against bedrock are insufficient to pry rock apart or damage bedrock although much more work is needed in this area. The frequency, magnitude and style of wind-driven tree forces at the bedrock interface varies considerably from one to another species. This suggests that tree properties such as mass, elasticity, stiffness and branch structure determine whether trees respond to gusts big or small, move at the same frequency as large wind gusts, or are able to self-dampen near-ground sway response to extended wind forces. Our measurements of precipitation-driven and daily fluctuations in root pressures exerted on

  16. Large-scale climatic effects on traditional Hawaiian fishpond aquaculture.

    Directory of Open Access Journals (Sweden)

    Daniel McCoy

    Full Text Available Aquaculture accounts for almost one-half of global fish consumption. Understanding the regional impact of climate fluctuations on aquaculture production thus is critical for the sustainability of this crucial food resource. The objective of this work was to understand the role of climate fluctuations and climate change in subtropical coastal estuarine environments within the context of aquaculture practices in He'eia Fishpond, O'ahu Island, Hawai'i. To the best of our knowledge, this was the first study of climate effects on traditional aquaculture systems in the Hawaiian Islands. Data from adjacent weather stations were analyzed together with in situ water quality instrument deployments spanning a 12-year period (November 2004 -November 2016. We found correlations between two periods with extremely high fish mortality at He'eia Fishpond (May and October 2009 and slackening trade winds in the week preceding each mortality event, as well as surface water temperatures elevated 2-3°C higher than the background periods (March-December 2009. We posit that the lack of trade wind-driven surface water mixing enhanced surface heating and stratification of the water column, leading to hypoxic conditions and stress on fish populations, which had limited ability to move within net pen enclosures. Elevated water temperature and interruption of trade winds previously have been linked to the onset of El Niño in Hawai'i. Our results provide empirical evidence regarding El Niño effects on the coastal ocean, which can inform resource management efforts about potential impact of climate variation on aquaculture production. Finally, we provide recommendations for reducing the impact of warming events on fishponds, as these events are predicted to increase in magnitude and frequency as a consequence of global warming.

  17. Topics in fluctuating nonlinear hydrodynamics

    International Nuclear Information System (INIS)

    Milner, S.T.

    1986-01-01

    Models of fluctuating nonlinear hydrodynamics have enjoyed much success in explaining the effect of long-wavelength fluctuations in diverse hydrodynamic systems. This thesis explores two such problems; in both, the body of hydrodynamic assumptions powerfully constrains the predictions of a well-posed theory. The effects of layer fluctuations in smectic-A liquid crystals are first examined. The static theory (introduced by Grinstein and Pelcovits) is reviewed. Ward identities, resulting from the arbitrariness of the layering direction, are derived and exploited. The static results motivate an examination of dynamic fluctuation effects. A new sound-damping experiment is proposed that would probe singular dependence of viscosities on applied stress. A theory of Procaccia and Gitterman that reaction rates of chemically reacting binary mixtures are drastically reduced near their thermodynamic critical points is analyzed. Hydrodynamic arguments and Van Hove theory are applied, concluding that the PG idea is drastically slowed, and spatially varying composition fluctuations are at best slowed down over a narrow range of wavenumbers

  18. Electric Field Fluctuations in Water

    Science.gov (United States)

    Thorpe, Dayton; Limmer, David; Chandler, David

    2013-03-01

    Charge transfer in solution, such as autoionization and ion pair dissociation in water, is governed by rare electric field fluctuations of the solvent. Knowing the statistics of such fluctuations can help explain the dynamics of these rare events. Trajectories short enough to be tractable by computer simulation are virtually certain not to sample the large fluctuations that promote rare events. Here, we employ importance sampling techniques with classical molecular dynamics simulations of liquid water to study statistics of electric field fluctuations far from their means. We find that the distributions of electric fields located on individual water molecules are not in general gaussian. Near the mean this non-gaussianity is due to the internal charge distribution of the water molecule. Further from the mean, however, there is a previously unreported Bjerrum-like defect that stabilizes certain large fluctuations out of equilibrium. As expected, differences in electric fields acting between molecules are gaussian to a remarkable degree. By studying these differences, though, we are able to determine what configurations result not only in large electric fields, but also in electric fields with long spatial correlations that may be needed to promote charge separation.

  19. Current-driven turbulence in plasmas

    International Nuclear Information System (INIS)

    Kluiver, H. de.

    1977-10-01

    Research on plasma heating in linear and toroidal systems using current-driven turbulence is reviewed. The motivation for this research is presented. Relations between parameters describing the turbulent plasma state and macroscopic observables are given. Several linear and toroidal devices used in current-driven turbulence studies are described, followed by a discussion of special diagnostic methods used. Experimental results on the measurement of electron and ion heating, anomalous plasma conductivity and associated turbulent fluctuation spectra are reviewed. Theories on current-driven turbulence are discussed and compared with experiments. It is demonstrated from the experimental results that current-driven turbulence occurs not only for extreme values of the electric field but also for an experimentally much more accessible and wide range of parameters. This forms a basis for a discussion on possible future applications in fusion-oriented plasma research

  20. Global climate change, war, and population decline in recent human history.

    Science.gov (United States)

    Zhang, David D; Brecke, Peter; Lee, Harry F; He, Yuan-Qing; Zhang, Jane

    2007-12-04

    Although scientists have warned of possible social perils resulting from climate change, the impacts of long-term climate change on social unrest and population collapse have not been quantitatively investigated. In this study, high-resolution paleo-climatic data have been used to explore at a macroscale the effects of climate change on the outbreak of war and population decline in the preindustrial era. We show that long-term fluctuations of war frequency and population changes followed the cycles of temperature change. Further analyses show that cooling impeded agricultural production, which brought about a series of serious social problems, including price inflation, then successively war outbreak, famine, and population decline successively. The findings suggest that worldwide and synchronistic war-peace, population, and price cycles in recent centuries have been driven mainly by long-term climate change. The findings also imply that social mechanisms that might mitigate the impact of climate change were not significantly effective during the study period. Climate change may thus have played a more important role and imposed a wider ranging effect on human civilization than has so far been suggested. Findings of this research may lend an additional dimension to the classic concepts of Malthusianism and Darwinism.

  1. Multiscale fluctuations in nuclear response

    International Nuclear Information System (INIS)

    Lacroix, D.; Chomaz, Ph.

    1999-01-01

    The nuclear collective response is investigated in the framework of a doorway picture in which the spreading width of the collective emotion is described as a coupling to more and more complex configurations. It is shown that this coupling induces fluctuations of the observed strength. In the case of a hierarchy of overlapping decay channels, Ericson fluctuations are observed at different scales. Methods for extracting these scales and the related lifetimes are discussed. Finally, it is shown that the coupling of different states at one level of complexity to some common decay channels at the next level, may produce interference-like patterns in the nuclear response. This quantum effect leads to anew type of fluctuations with a typical width related to the level spacing. (author)

  2. Fluctuation relations for anomalous dynamics

    International Nuclear Information System (INIS)

    Chechkin, A V; Klages, R

    2009-01-01

    We consider work fluctuation relations (FRs) for generic types of dynamics generating anomalous diffusion: Lévy flights, long-correlated Gaussian processes and time-fractional kinetics. By combining Langevin and kinetic approaches we calculate the probability distributions of mechanical and thermodynamical work in two paradigmatic nonequilibrium situations, respectively: a particle subject to a constant force and a particle in a harmonic potential dragged by a constant force. We check the transient FR for two models exhibiting superdiffusion, where a fluctuation-dissipation relation does not exist, and for two other models displaying subdiffusion, where there is a fluctuation-dissipation relation. In the two former cases the conventional transient FR is not recovered, whereas in the latter two it holds either exactly or in the long-time limit. (letter)

  3. Fluctuations in the multiparticle dynamics

    International Nuclear Information System (INIS)

    Bozek, P.; Ploszajczak, M.

    1993-01-01

    The appearance and properties of intermittent fluctuations in physical systems, in particular the formation of rare structures in transport phenomena are discussed. The distribution of fluctuations approaches a limiting log-normal statistical distribution. The log-normal distribution is introduced as a simple parametrization of the energy fluctuations leading to the subthreshold production of particles in nuclear collisions, and it is shown that it fits all available data both for total π 0 production cross section as well as the π 0 kinetic energy spectra for E/A < 90 MeV. It is suggested that the same universal distribution should also describe the subthreshold production of other hadrons like η and K. (author) 36 refs., 11 figs

  4. Multiscale fluctuations in nuclear response

    Energy Technology Data Exchange (ETDEWEB)

    Lacroix, D.; Chomaz, Ph

    1999-01-01

    The nuclear collective response is investigated in the framework of a doorway picture in which the spreading width of the collective emotion is described as a coupling to more and more complex configurations. It is shown that this coupling induces fluctuations of the observed strength. In the case of a hierarchy of overlapping decay channels, Ericson fluctuations are observed at different scales. Methods for extracting these scales and the related lifetimes are discussed. Finally, it is shown that the coupling of different states at one level of complexity to some common decay channels at the next level, may produce interference-like patterns in the nuclear response. This quantum effect leads to anew type of fluctuations with a typical width related to the level spacing. (author) 25 refs.

  5. Phase space fluctuations and dynamics of fluctuations of collective variables

    Energy Technology Data Exchange (ETDEWEB)

    Benhassine, B.; Farine, M.; Idier, D.; Remaud, B.; Sebille, F. (Lab. de Physique Nucleaire, IN2P3/CNRS, 44 - Nantes (France) Nantes Univ., 44 (France)); Hernandez, E.S. (Dept. de Fisica, Ciudad Universitaria, Buenos Aires (Argentina))

    1992-08-03

    Within the framework of theoretical approaches based on stochastic transport equation of one-body distribution function, a numerical treatment of the fluctuations of collective observables is studied and checked in comparison with analytical results either at equilibrium or close to it. (orig.).

  6. Phase space fluctuations and dynamics of fluctuations of collective variables

    International Nuclear Information System (INIS)

    Benhassine, B.; Farine, M.; Idier, D.; Remaud, B.; Sebille, F.; Hernandez, E.S.

    1992-01-01

    Within the framework of theoretical approaches based on stochastic transport equation of one-body distribution function, a numerical treatment of the fluctuations of collective observables is studied and checked in comparison with analytical results either at equilibrium or close to it. (orig.)

  7. Entropic Repulsion Between Fluctuating Surfaces

    Science.gov (United States)

    Janke, W.

    The statistical mechanics of fluctuating surfaces plays an important role in a variety of physical systems, ranging from biological membranes to world sheets of strings in theories of fundamental interactions. In many applications it is a good approximation to assume that the surfaces possess no tension. Their statistical properties are then governed by curvature energies only, which allow for gigantic out-of-plane undulations. These fluctuations are the “entropic” origin of long-range repulsive forces in layered surface systems. Theoretical estimates of these forces for simple model surfaces are surveyed and compared with recent Monte Carlo simulations.

  8. Origin of cosmological density fluctuations

    International Nuclear Information System (INIS)

    Carr, B.J.

    1984-11-01

    The density fluctuations required to explain the large-scale cosmological structure may have arisen spontaneously as a result of a phase transition in the early Universe. There are several ways in which such fluctuations may have ben produced, and they could have a variety of spectra, so one should not necessarily expect all features of the large-scale structure to derive from a simple power law spectrum. Some features may even result from astrophysical amplification mechanisms rather than gravitational instability. 128 references

  9. Plague dynamics are driven by climate variation

    DEFF Research Database (Denmark)

    Stenseth, Nils Chr.; Samia, Noelle I.; Viljugrein, Hildegunn

    2006-01-01

    The bacterium Yersinia pestis causes bubonic plague. In Central Asia, where human plague is still reported regularly, the bacterium is common in natural populations of great gerbils. By using field data from 1949-1995 and previously undescribed statistical techniques, we show that Y. pestis...

  10. Market-oriented ethanol and corn-trade policies can reduce climate-induced US corn price volatility

    International Nuclear Information System (INIS)

    Verma, Monika; Diffenbaugh, Noah; Hertel, Thomas

    2014-01-01

    Agriculture is closely affected by climate. Over the past decade, biofuels have emerged as another important factor shaping the agricultural sector. We ask whether the presence of the US ethanol sector can play a role in moderating increases in US corn price variability, projected to occur in response to near-term global warming. Our findings suggest that the answer to this question depends heavily on the underlying forces shaping the ethanol industry. If mandate-driven, there is little doubt that the presence of the corn-ethanol sector will exacerbate price volatility. However, if market-driven, then the emergence of the corn-ethanol sector can be a double-edged sword for corn price volatility, possibly cushioning the impact of increased climate driven supply volatility, but also inheriting volatility from the newly integrated energy markets via crude oil price fluctuations. We find that empirically the former effect dominates, reducing price volatility by 27%. In contrast, mandates on ethanol production increase future price volatility by 54% in under future climate after 2020. We also consider the potential for liberalized international corn trade to cushion corn price volatility in the US. Our results suggest that allowing corn to move freely internationally serves to reduce the impact of near-term climate change on US corn price volatility by 8%. (letter)

  11. Market-oriented ethanol and corn-trade policies can reduce climate-induced US corn price volatility

    Science.gov (United States)

    Verma, Monika; Hertel, Thomas; Diffenbaugh, Noah

    2014-05-01

    Agriculture is closely affected by climate. Over the past decade, biofuels have emerged as another important factor shaping the agricultural sector. We ask whether the presence of the US ethanol sector can play a role in moderating increases in US corn price variability, projected to occur in response to near-term global warming. Our findings suggest that the answer to this question depends heavily on the underlying forces shaping the ethanol industry. If mandate-driven, there is little doubt that the presence of the corn-ethanol sector will exacerbate price volatility. However, if market-driven, then the emergence of the corn-ethanol sector can be a double-edged sword for corn price volatility, possibly cushioning the impact of increased climate driven supply volatility, but also inheriting volatility from the newly integrated energy markets via crude oil price fluctuations. We find that empirically the former effect dominates, reducing price volatility by 27%. In contrast, mandates on ethanol production increase future price volatility by 54% in under future climate after 2020. We also consider the potential for liberalized international corn trade to cushion corn price volatility in the US. Our results suggest that allowing corn to move freely internationally serves to reduce the impact of near-term climate change on US corn price volatility by 8%.

  12. The intrinsic periodic fluctuation of forest: a theoretical model based on diffusion equation

    Science.gov (United States)

    Zhou, J.; Lin, G., Sr.

    2015-12-01

    Most forest dynamic models predict the stable state of size structure as well as the total basal area and biomass in mature forest, the variation of forest stands are mainly driven by environmental factors after the equilibrium has been reached. However, although the predicted power-law size-frequency distribution does exist in analysis of many forest inventory data sets, the estimated distribution exponents are always shifting between -2 and -4, and has a positive correlation with the mean value of DBH. This regular pattern can not be explained by the effects of stochastic disturbances on forest stands. Here, we adopted the partial differential equation (PDE) approach to deduce the systematic behavior of an ideal forest, by solving the diffusion equation under the restricted condition of invariable resource occupation, a periodic solution was gotten to meet the variable performance of forest size structure while the former models with stable performance were just a special case of the periodic solution when the fluctuation frequency equals zero. In our results, the number of individuals in each size class was the function of individual growth rate(G), mortality(M), size(D) and time(T), by borrowing the conclusion of allometric theory on these parameters, the results perfectly reflected the observed "exponent-mean DBH" relationship and also gave a logically complete description to the time varying form of forest size-frequency distribution. Our model implies that the total biomass of a forest can never reach a stable equilibrium state even in the absence of disturbances and climate regime shift, we propose the idea of intrinsic fluctuation property of forest and hope to provide a new perspective on forest dynamics and carbon cycle research.

  13. Spectrum of resistivity gradient driven turbulence

    International Nuclear Information System (INIS)

    Terry, P.W.; Diamond, P.H.; Shaing, K.C.; Garcia, L.; Carreras, B.A.

    1986-01-01

    The resistivity fluctuation correlation function and electrostatic potential spectrum of resistivity gradient driven turbulence are calculated analytically and compared to the results of three dimensional numerical calculations. Resistivity gradient driven turbulence is characterized by effective Reynolds' numbers of order unity. Steady-state solution of the renormalized spectrum equations yields an electrostatic potential spectrum (circumflex phi 2 )/sub ktheta/ approx. k/sub theta//sup -3.25/. Agreement of the analytically calculated potential spectrum and mean-square radial velocity with the results of multiple helicity numerical calculations is excellent. This comparison constitutes a quantitative test of the analytical turbulence theory used. The spectrum of magnetic fluctuations is also calculated, and agrees well with that obtained from the numerical computations. 13 refs., 8 figs

  14. Fluctuations in Overlapping Generations Economies

    DEFF Research Database (Denmark)

    Tvede, Mich

    . The approach to existence of endogenous fluctuations is basic in the sense that the prime ingredients are the implicit function theorem and linear algebra. Moreover the approach is applied to show that for an open and dense set of utility functions there exist endowment vectors such that sunspot equilibria...

  15. Magnetic fluctuations in turbulent flow

    International Nuclear Information System (INIS)

    Ruzmaikin, A.A.

    1990-01-01

    For dynamo excitation of the magnetic fluctuations in infinite fluid only a sufficient large magnetic Reynolds number is needed. In a infinite region an additional condition appears. Due to the diffusion of the magnetic field through the boundaries a size of the region must be large enough compare with a correlation length of the turbulence. Author)

  16. Firm default and aggregate fluctuations

    NARCIS (Netherlands)

    Jacobson, Tor; Linde, Jesper; Roszbach, Kasper

    This paper studies the relationship between macroeconomic fluctuations and corporate defaults while conditioning on industry affiliation and an extensive set of firm-specific factors. By using a panel data set for virtually all incorporated Swedish businesses over 1990-2009, a period which includes

  17. Fluctuating hydrodynamics for ionic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Lazaridis, Konstantinos [Department of Mathematics and Statistics, Washington State University, Pullman, 99163 (United States); Wickham, Logan [Department of Computer Science, Washington State University, Richland, 99354 (United States); Voulgarakis, Nikolaos, E-mail: n.voulgarakis@wsu.edu [Department of Mathematics and Statistics, Washington State University, Pullman, 99163 (United States)

    2017-04-25

    We present a mean-field fluctuating hydrodynamics (FHD) method for studying the structural and transport properties of ionic liquids in bulk and near electrified surfaces. The free energy of the system consists of two competing terms: (1) a Landau–Lifshitz functional that models the spontaneous separation of the ionic groups, and (2) the standard mean-field electrostatic interaction between the ions in the liquid. The numerical approach used to solve the resulting FHD-Poisson equations is very efficient and models thermal fluctuations with remarkable accuracy. Such density fluctuations are sufficiently strong to excite the experimentally observed spontaneous formation of liquid nano-domains. Statistical analysis of our simulations provides quantitative information about the properties of ionic liquids, such as the mixing quality, stability, and the size of the nano-domains. Our model, thus, can be adequately parameterized by directly comparing our prediction with experimental measurements and all-atom simulations. Conclusively, this work can serve as a practical mathematical tool for testing various theories and designing more efficient mixtures of ionic liquids. - Highlights: • A new fluctuating hydrodynamics method for ionic liquids. • Description of ionic liquid morphology in bulk and near electrified surfaces. • Direct comparison with experimental measurements.

  18. The Sahel Region of West Africa: Examples of Climate Analyses Motivated By Drought Management Needs

    Science.gov (United States)

    Ndiaye, O.; Ward, M. N.; Siebert, A. B.

    2011-12-01

    The Sahel is one of the most drought-prone regions in the world. This paper focuses on climate sources of drought, and some new analyses mostly driven by users needing climate information to help in drought management strategies. The Sahel region of West Africa is a transition zone between equatorial climate and vegetation to the south, and desert to the north. The climatology of the region is dominated by dry conditions for most of the year, with a single peak in rainfall during boreal summer. The seasonal rainfall total contains both interannual variability and substantial decadal to multidecadal variability (MDV). This brings climate analysis and drought management challenges across this range of timescales. The decline in rainfall from the wet decades of the 1950s and 60s to the dry decades of the 1970s and 80s has been well documented. In recent years, a moderate recovery has emerged, with seasonal totals in the period 1994-2010 significantly higher than the average rainfall 1970-1993. These MDV rainfall fluctuations have expression in large-scale sea-surface temperature fluctuations in all ocean basins, placing the changes in drought frequency within broader ocean-atmosphere climate fluctuation. We have evaluated the changing character of low seasonal rainfall total event frequencies in the Sahel region 1950-2010, highlighting the role of changes in the mean, variance and distribution shape of seasonal rainfall totals as the climate has shifted through the three observed phases. We also consider the extent to which updating climate normals in real-time can damp the bias in expected event frequency, an important issue for the feasibility of index insurance as a drought management tool in the presence of a changing climate. On the interannual timescale, a key factor long discussed for agriculture is the character of rainfall onset. An extended dry spell often occurs early in the rainy season before the crop is fully established, and this often leads to crop

  19. Transport and fluctuations in high temperature spheromak plasmas

    International Nuclear Information System (INIS)

    McLean, H.S.; Wood, R.D.; Cohen, B.I.; Hooper, E.B.; Hill, D.N.; Moller, J.M.; Romero-Talamas, C.; Woodruff, S.

    2006-01-01

    Higher electron temperature (T e >350 eV) and reduced electron thermal diffusivity (χ e 2 /s) is achieved in the Sustained Spheromak Physics Experiment (SSPX) by increasing the discharge current=I gun and gun bias flux=ψ gun in a prescribed manner. The internal current and q=safety factor profile derived from equilibrium reconstruction as well as the measured magnetic fluctuation amplitude can be controlled by programming the ratio λ gun =μ 0 I gun /ψ gun . Varying λ gun above and below the minimum energy eigenvalue=λ FC of the flux conserver (∇xB-vector=λ FC B-vector) varies the q profile and produces the m/n=poloidal/toroidal magnetic fluctuation mode spectrum expected from mode-rational surfaces with q=m/n. The highest T e is measured when the gun is driven with λ gun slightly less than λ FC , producing low fluctuation amplitudes ( e as T e increases, differing from Bohm or open field line transport models where χ e increases with T e . Detailed resistive magnetohydrodynamic simulations with the NIMROD code support the analysis of energy confinement in terms of the causal link with the q profile, magnetic fluctuations associated with low-order mode-rational surfaces, and the quality of magnetic surfaces

  20. Glacial greenhouse-gas fluctuations controlled by ocean circulation changes.

    Science.gov (United States)

    Schmittner, Andreas; Galbraith, Eric D

    2008-11-20

    Earth's climate and the concentrations of the atmospheric greenhouse gases carbon dioxide (CO(2)) and nitrous oxide (N(2)O) varied strongly on millennial timescales during past glacial periods. Large and rapid warming events in Greenland and the North Atlantic were followed by more gradual cooling, and are highly correlated with fluctuations of N(2)O as recorded in ice cores. Antarctic temperature variations, on the other hand, were smaller and more gradual, showed warming during the Greenland cold phase and cooling while the North Atlantic was warm, and were highly correlated with fluctuations in CO(2). Abrupt changes in the Atlantic meridional overturning circulation (AMOC) have often been invoked to explain the physical characteristics of these Dansgaard-Oeschger climate oscillations, but the mechanisms for the greenhouse-gas variations and their linkage to the AMOC have remained unclear. Here we present simulations with a coupled model of glacial climate and biogeochemical cycles, forced only with changes in the AMOC. The model simultaneously reproduces characteristic features of the Dansgaard-Oeschger temperature, as well as CO(2) and N(2)O fluctuations. Despite significant changes in the land carbon inventory, CO(2) variations on millennial timescales are dominated by slow changes in the deep ocean inventory of biologically sequestered carbon and are correlated with Antarctic temperature and Southern Ocean stratification. In contrast, N(2)O co-varies more rapidly with Greenland temperatures owing to fast adjustments of the thermocline oxygen budget. These results suggest that ocean circulation changes were the primary mechanism that drove glacial CO(2) and N(2)O fluctuations on millennial timescales.

  1. Climate change and human colonization triggered habitat loss and fragmentation in Madagascar.

    Science.gov (United States)

    Salmona, Jordi; Heller, Rasmus; Quéméré, Erwan; Chikhi, Lounès

    2017-10-01

    The relative effect of past climate fluctuations and anthropogenic activities on current biome distribution is subject to increasing attention, notably in biodiversity hot spots. In Madagascar, where humans arrived in the last ~4 to 5,000 years, the exact causes of the demise of large vertebrates that cohabited with humans are yet unclear. The prevailing narrative holds that Madagascar was covered with forest before human arrival and that the expansion of grasslands was the result of human-driven deforestation. However, recent studies have shown that vegetation and fauna structure substantially fluctuated during the Holocene. Here, we study the Holocene history of habitat fragmentation in the north of Madagascar using a population genetics approach. To do so, we infer the demographic history of two northern Madagascar neighbouring, congeneric and critically endangered forest dwelling lemur species-Propithecus tattersalli and Propithecus perrieri-using population genetic analyses. Our results highlight the necessity to consider population structure and changes in connectivity in demographic history inferences. We show that both species underwent demographic fluctuations which most likely occurred after the mid-Holocene transition. While mid-Holocene climate change probably triggered major demographic changes in the two lemur species range and connectivity, human settlements that expanded over the last four millennia in northern Madagascar likely played a role in the loss and fragmentation of the forest cover. © 2017 John Wiley & Sons Ltd.

  2. Quenched disorder and thermopower fluctuations in high temperature superconductors

    International Nuclear Information System (INIS)

    Khalil, A.E.

    1997-01-01

    Thermopower behavior in high temperature superconductors YBa 2 Cu 3 O 7-δ single crystals near the transition temperature was examined. An expression for the thermoelectric power containing the divergent term (1-T/T c ) -s , where s is a scaling exponent that does not appear in Maki's calculations, was derived. This divergent term is the result of contributions due to the flow of currents across disordered conduction paths in the sample. These currents are driven by the density gradients of the conductivity fluctuations as a result of the increased disorder due to the existence of amorphous regions in the two-dimensional lattice. The present calculations include the most divergent effects to the thermopower due to the conductivity fluctuations near the transition temperature. The model predictions are in good agreement with recent experimental measurements reported in the literature. (orig.)

  3. Science in the Sandbox: Fluctuations, Friction and Instabilities

    DEFF Research Database (Denmark)

    Behringer, R.B.; Clement, Eric; Geng, Junfei

    2001-01-01

    The study of granular materials is a novel and rapidly growing field. These materials are interest for a number of reasons, both practical and theoretical. They exhibit a rich of novel dyanamical states, and they exhibit ‘phases’-solid, liquid, and gas-that resemble conventional thermodynamic...... descriptions for the mean and fluctuating behavior of these materials. We explore recent work that focuses on several important issues. These include force propagation and fluctuations in static and driven systems. It is well known that forces propagate through granular structures along networks-force chains......, whose structure is a function of history. It is much less clear how to describe this process, and even what kind of structures evolve in physical experiments. After a brief overview of the field, we consider models of force propagation and recent experiments to test these models. Among the latter...

  4. Interdisciplinary process driven performative morphologies : A morphogenomic approach towards developing context aware spatial formations

    NARCIS (Netherlands)

    Biloria, N.M.

    2011-01-01

    Architectural praxis is in continuous state of change. The introduction of information technology driven design techniques, constantly updating building information modeling protocols, new policy demands coupled together with environmental regulations and cultural fluctuations are all open-ended

  5. Climate and atmospheric research

    International Nuclear Information System (INIS)

    Kramer, G.; Schumacher, R.

    1992-01-01

    This issue of the scientific journal of the Humboldt university is dedicated to results of research work carried out to the greatest extent at the meteorological institute in the last two years on the area of climate and atmospheric research. The traditional research areas of the institute are climatology and the dynamics of the atmosphere, in particular the atmospherical boundary layer. Considering the high probability of a global climatic fluctuation due to the anthropogenic change of composition of the atmosphere and other climate-relevant factors imminent in the next century, climatological research today is an important part of global and regional environmental research. From the necessity of determination and evaluation of the effect of climatic fluctuations on nature and society the contours of a new interdisciplinary research area are already visible now. This is suitable as hardly any other area to be the supporting idea of environmental research at universities. The contributions contained in the issue already consider, in addition to results on climate diagnosis, also results on aspects of climate effect research. (orig./KW) [de

  6. Potential effects of climate change on aquatic ecosystems of the Great Plains of North America

    Science.gov (United States)

    Covich, A.P.; Fritz, S.C.; Lamb, P.J.; Marzolf, R.D.; Matthews, W.J.; Poiani, K.A.; Prepas, E.E.; Richman, M.B.; Winter, T.C.

    1997-01-01

    The Great Plains landscape is less topographically complex than most other regions within North America, but diverse aquatic ecosystems, such as playas, pothole lakes, ox-bow lakes, springs, groundwater aquifers, intermittent and ephemeral streams, as well as large rivers and wetlands, are highly dynamic and responsive to extreme climatic fluctuations. We review the evidence for climatic change that demonstrates the historical importance of extremes in north-south differences in summer temperatures and east-west differences in aridity across four large subregions. These physical driving forces alter density stratification, deoxygenation, decomposition and salinity. Biotic community composition and associated ecosystem processes of productivity and nutrient cycling respond rapidly to these climatically driven dynamics. Ecosystem processes also respond to cultural effects such as dams and diversions of water for irrigation, waste dilution and urban demands for drinking water and industrial uses. Distinguishing climatic from cultural effects in future models of aquatic ecosystem functioning will require more refinement in both climatic and economic forecasting. There is a need, for example, to predict how long-term climatic forecasts (based on both ENSO and global warming simulations) relate to the permanence and productivity of shallow water ecosystems. Aquatic ecologists, hydrologists, climatologists and geographers have much to discuss regarding the synthesis of available data and the design of future interdisciplinary research. ?? 1997 by John Wiley & Sons, Ltd.

  7. Fluctuation current in superconducting loops

    International Nuclear Information System (INIS)

    Berger, Jorge

    2012-01-01

    A superconducting loop that encloses noninteger flux holds a permanent current. On the average, this current is also present above T c , and has been measured in recent years. We are able to evaluate the permanent current within the TDGL or the Kramer-Watts-Tobin models for loops of general configuration, i.e., we don't require uniform cross section, material or temperature. We can also consider situations in which the width is not negligible in comparison to the radius. Our results agree with experiments. The situations with which we deal at present include fluctuation superconductivity in two-band superconductors, equilibrium thermal fluctuations of supercurrent along a weak link, and ratchet effects.

  8. Fluctuations and confinement in ATF

    International Nuclear Information System (INIS)

    Isler, R.C.; Harris, J.H.; Murakami, M.

    1993-01-01

    In the period immediately prior to the suspension of ATF operation in November, 1991, a great deal of emphasis was palced on investigations of the fundamental mechanisms controlling confinement in this device. At that time, measurements of the density fluctuations throughout the plasma volume indicated the existence of theoretically predicted dissipative trapped electron and resistive interchange instabilities. These identifications were supported by results of dynamic configuration scans of the magnetic fields during which the extent of the magnetic well, shear, and fraction of confined trapped particles were changed continuously. Interpretation of the data from these experiments has been an ongoing exercise. Most recently, analysis of discharges employing strong gas puffing to change density gradients and fluctuation levels have strengthened the view that dissipative trapped electron modes may be present but do not play a significant direct role in energy transport. The present paper summarizes the current understanding concerning the identification of instabilities and their relationship to confinement in ATF

  9. Challenging climate change : competition and cooperation among pastoralists and agriculturalists in northern Mesopotamia (c. 3000-1600 BC)

    NARCIS (Netherlands)

    Wossink, Arne

    2009-01-01

    Throughout history, climate change has been an important driving force behind human behaviour. This archaeological study seeks to understand the complex interrelations between that behaviour and climatic fluctuations, focussing on how climate affected the social relations between neighbouring

  10. Random numbers from vacuum fluctuations

    International Nuclear Information System (INIS)

    Shi, Yicheng; Kurtsiefer, Christian; Chng, Brenda

    2016-01-01

    We implement a quantum random number generator based on a balanced homodyne measurement of vacuum fluctuations of the electromagnetic field. The digitized signal is directly processed with a fast randomness extraction scheme based on a linear feedback shift register. The random bit stream is continuously read in a computer at a rate of about 480 Mbit/s and passes an extended test suite for random numbers.

  11. Random numbers from vacuum fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Yicheng; Kurtsiefer, Christian, E-mail: christian.kurtsiefer@gmail.com [Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Center for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore); Chng, Brenda [Center for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore)

    2016-07-25

    We implement a quantum random number generator based on a balanced homodyne measurement of vacuum fluctuations of the electromagnetic field. The digitized signal is directly processed with a fast randomness extraction scheme based on a linear feedback shift register. The random bit stream is continuously read in a computer at a rate of about 480 Mbit/s and passes an extended test suite for random numbers.

  12. Electron temperature fluctuation in the HT-7 tokamak plasma observed by electron cyclotron emission imaging

    International Nuclear Information System (INIS)

    Xiao-Yuan, Xu; Jun, Wang; Yi, Yu; Yi-Zhi, Wen; Chang-Xuan, Yu; Wan-Dong, Liu; Bao-Nian, Wan; Xiang, Gao; Luhmann, N. C.; Domier, C. W.; Wang, Jian; Xia, Z. G.; Shen, Zuowei

    2009-01-01

    The fluctuation of the electron temperature has been measured by using the electron cyclotron emission imaging in the Hefei Tokamak-7 (HT-7) plasma. The electron temperature fluctuation with a broadband spectrum shows that it propagates in the electron diamagnetic drift direction, and the mean poloidal wave-number k-bar θ is calculated to be about 1.58 cm −1 , or k-bar θρ s thickapprox 0.34. It indicates that the fluctuation should come from the electron drift wave turbulence. The linear global scaling of the electron temperature fluctuation with the gradient of electron temperature is consistent with the mixing length scale qualitatively. Evolution of spectrum of the fluctuation during the sawtooth oscillation phases is investigated, and the fluctuation is found to increase with the gradient of electron temperature increasing during most phases of the sawtooth oscillation. The results indicate that the electron temperature gradient is probably the driver of the fluctuation enhancement. The steady heat flux driven by electron temperature fluctuation is estimated and compared with the results from power balance estimation. (fluids, plasmas and electric discharges)

  13. Influence of Signal and Noise on Statistical Fluctuation of Single-Mode Laser System

    International Nuclear Information System (INIS)

    Xu Dahai; Cheng Qinghua; Cao Li; Wu Dajin

    2006-01-01

    On the basis of calculating the steady-state mean normalized intensity fluctuation of a signal-mode laser system driven by both colored pump noise with signal modulation and the quantum noise with cross-correlation between its real and imaginary parts, we analyze the influence of modulation signal, noise, and its correlation form on the statistical fluctuation of the laser system. We have found that when the amplitude of modulation signal weakens and its frequency quickens, the statistical fluctuation will reduce rapidly. The statistical fluctuation of the laser system can be restrained by reducing the intensity of pump noise and quantum noise. Moreover, with prolonging of colored cross-correlation time, the statistical fluctuation of laser system experiences a repeated changing process, that is, from decreasing to augmenting, then to decreasing, and finally to augmenting again. With the decreasing of the value of cross-correlation coefficient, the statistical fluctuation will decrease too. When the cross-correlation form between the real part and imaginary part of quantum noise is zero correlation, the statistical fluctuation of laser system has a minimum. Compared with the influence of intensity of pump noise, the influence of intensity of quantum noise on the statistical fluctuation is smaller.

  14. Elucidation of the fluctuation history of cosmic radiation and global environmental using AMS

    International Nuclear Information System (INIS)

    Horiuchi, Kazuho

    2008-01-01

    Recently, accuracy of AMS has further been raised in trace amounts of sample. Besides application of 14 C to the age estimation, it has been able to restore in detail the past fluctuation of cosmic radiation strength using the other radioactive isotopes ( 10 Be, 36 Cl etc) in environmental samples and to elucidate the correlation of this with the fluctuation of climate and environment. In this report, the attempts to elucidate the fluctuation history of cosmic radiation and global environment with ice cores using AMS are presented. (M.H.)

  15. Quantum Fluctuations for Gravitational Impulsive Waves

    OpenAIRE

    Enginer, Y.; Hortacsu, M.; Ozdemir, N.

    1998-01-01

    Quantum fluctuations for a massless scalar field in the background metric of spherical impulsive gravitational waves through Minkowski and de Sitter spaces are investigated. It is shown that there exist finite fluctuations for de Sitter space.

  16. Net charge fluctuations and local charge compensation

    International Nuclear Information System (INIS)

    Fu Jinghua

    2006-01-01

    We propose net charge fluctuation as a measure of local charge correlation length. It is demonstrated that, in terms of a schematic multiperipheral model, net charge fluctuation satisfies the same Quigg-Thomas relation as satisfied by charge transfer fluctuation. Net charge fluctuations measured in finite rapidity windows depend on both the local charge correlation length and the size of the observation window. When the observation window is larger than the local charge correlation length, the net charge fluctuation only depends on the local charge correlation length, while forward-backward charge fluctuations always have strong dependence on the observation window size. Net charge fluctuations and forward-backward charge fluctuations measured in the present heavy ion experiments show characteristic features similar to those from multiperipheral models. But the data cannot all be understood within this simple model

  17. Profiling the regional wind power fluctuation in China

    International Nuclear Information System (INIS)

    Yu Dayang; Liang Jun; Han Xueshan; Zhao Jianguo

    2011-01-01

    As China starts to build 6 10-GW wind zones in 5 provinces by 2020, accommodating the wind electricity generated from these large wind zones will be a great challenge for the regional grids. Inadequate wind observing data hinders profiling the wind power fluctuations at the regional grid level. This paper proposed a method to assess the seasonal and diurnal wind power patterns based on the wind speed data from the NASA GEOS-5 DAS system, which provides data to the study of climate processes including the long-term estimates of meteorological quantities. The wind power fluctuations for the 6 largest wind zones in China are presented with both the capacity factor and the megawatt wind power output. The measured hourly wind output in a regional grid is compared to the calculating result to test the analyzing model. To investigate the offsetting effect of dispersed wind farms over large regions, the regional correlations of hourly wind power fluctuations are calculated. The result illustrates the different offsetting effects of minute and hourly fluctuations.

  18. Concentration fluctuations in non-isothermal reaction-diffusion systems. II. The nonlinear case

    NARCIS (Netherlands)

    Bedeaux, D.; Ortiz de Zárate, J.M.; Pagonabarraga, I.; Sengers, J.V.; Kjelstrup, S.

    2011-01-01

    In this paper, we consider a simple reaction-diffusion system, namely, a binary fluid mixture with an association-dissociation reaction between two species. We study fluctuations at hydrodynamic spatiotemporal scales when this mixture is driven out of equilibrium by the presence of a temperature

  19. Bistability and low-frequency fluctuations in semiconductor lasers with optical feedback: a theoretical analysis

    DEFF Research Database (Denmark)

    Mørk, Jesper; Tromborg, Bjarne; Christiansen, Peter Leth

    1988-01-01

    Near-threshold operation of a semiconductor laser exposed to moderate optical feedback may lead to low-frequency fluctuations. In the same region, a kink is observed in the light-current characteristic. Here it is demonstrated that these nonlinear phenomena are predicted by a noise driven multimode...

  20. Measurement of magnetic fluctuation induced energy transport

    International Nuclear Information System (INIS)

    Fiksel, G.; Prager, S.C.; Shen, W.; Stoneking, M.

    1993-11-01

    The local electron energy flux produced by magnetic fluctuations has been measured directly in the MST reversed field pinch (over the radial range r/a > 0.75). The flux, produced by electrons traveling parallel to a fluctuating magnetic field, is obtained from correlation between the fluctuations in the parallel heat flux and the radial magnetic field. The fluctuation induced flux is large (100 kW/cm 2 ) in the ''core'' (r/a 2 ) in the edge

  1. Limiter effects on scrape-off layer fluctuations and transport

    International Nuclear Information System (INIS)

    Thayer, D.R.; Diamond, P.H.; Wootton, A.J.

    1987-01-01

    Edge turbulence experiments indicate that radial particle flux increases as a function of radius up to the scrape-off layer (SOL), and that the Boltzman relation is violated. Resistivity gradient driven turbulence (RGDT) theory has been shown to track the radial dependence of the particle flux in the plasma edge closer than dissipative density gradient driven turbulence (DDGDT) theory. Also, the Boltzman relation is not invoked for RGDT while it is usually assumed for DDGDT. Consequently, RGDT is a more likely candidate for an edge turbulence model. However, Langmuir probe experiments indicate that the particle flux is reduced by as much as 50% in the SOL. Thus, since basic turbulence theories do not account for limiter effects, the primary focus of this study is to include such effects in a RGDT theory of the SOL. We present an analysis of SOL fluctuations using a rippling mode or RGDT calculation which incorporates the essential limiter boundary condition.(orig./GG)

  2. Holocene climatic fluctuations from Lower Brahmaputra flood plain

    Indian Academy of Sciences (India)

    Pollen analysis of a 3.2-m deep sedimentary profile cored from the Dabaka Swamp, Nagaon District, Lower Brahmaputra flood plain, Assam has revealed persistent fluvial activity during 14,120–12,700 cal years BP which may be attributed to the paucity of pollen and spores with encounterance of fluvial marker taxa like ...

  3. Optimal control of quantum systems: Origins of inherent robustness to control field fluctuations

    International Nuclear Information System (INIS)

    Rabitz, Herschel

    2002-01-01

    The impact of control field fluctuations on the optimal manipulation of quantum dynamics phenomena is investigated. The quantum system is driven by an optimal control field, with the physical focus on the evolving expectation value of an observable operator. A relationship is shown to exist between the system dynamics and the control field fluctuations, wherein the process of seeking optimal performance assures an inherent degree of system robustness to such fluctuations. The presence of significant field fluctuations breaks down the evolution of the observable expectation value into a sequence of partially coherent robust steps. Robustness occurs because the optimization process reduces sensitivity to noise-driven quantum system fluctuations by taking advantage of the observable expectation value being bilinear in the evolution operator and its adjoint. The consequences of this inherent robustness are discussed in the light of recent experiments and numerical simulations on the optimal control of quantum phenomena. The analysis in this paper bodes well for the future success of closed-loop quantum optimal control experiments, even in the presence of reasonable levels of field fluctuations

  4. Analysis of dynamic multiplicity fluctuations at PHOBOS

    Science.gov (United States)

    Chai, Zhengwei; PHOBOS Collaboration; Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Betts, R. R.; Bickley, A. A.; Bindel, R.; Budzanowski, A.; Busza, W.; Carroll, A.; Chai, Z.; Decowski, M. P.; García, E.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Heintzelman, G. A.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Holynski, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Katzy, J.; Khan, N.; Kucewicz, W.; Kulinich, P.; Kuo, C. M.; Lin, W. T.; Manly, S.; McLeod, D.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Park, I. C.; Pernegger, H.; Reed, C.; Remsberg, L. P.; Reuter, M.; Roland, C.; Roland, G.; Rosenberg, L.; Sagerer, J.; Sarin, P.; Sawicki, P.; Skulski, W.; Steinberg, P.; Stephans, G. S. F.; Sukhanov, A.; Tang, J. L.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Verdier, R.; Wolfs, F. L. H.; Wosiek, B.; Wozniak, K.; Wuosmaa, A. H.; Wyslouch, B.

    2005-01-01

    This paper presents the analysis of the dynamic fluctuations in the inclusive charged particle multiplicity measured by PHOBOS for Au+Au collisions at surdsNN = 200GeV within the pseudo-rapidity range of -3 < η < 3. First the definition of the fluctuations observables used in this analysis is presented, together with the discussion of their physics meaning. Then the procedure for the extraction of dynamic fluctuations is described. Some preliminary results are included to illustrate the correlation features of the fluctuation observable. New dynamic fluctuations results will be available in a later publication.

  5. Noise and fluctuations an introduction

    CERN Document Server

    MacDonald, D K C

    2006-01-01

    An understanding of fluctuations and their role is both useful and fundamental to the study of physics. This concise study of random processes offers graduate students and research physicists a survey that encompasses both the relationship of Brownian Movement with statistical mechanics and the problem of irreversible processes. It outlines the basics of the physics involved, without the strictures of mathematical rigor.The three-part treatment starts with a general survey of Brownian Movement, including electrical Brownian Movement and ""shot-noise,"" Part two explores correlation, frequency

  6. Electrostatic fluctuations in soap films

    International Nuclear Information System (INIS)

    Dean, D.S.; Horgan, R.R.

    2002-01-01

    A field theory to describe electrostatic interactions in soap films, described by electric multilayers with a generalized thermodynamic surface-charging mechanism, is studied. In the limit where the electrostatic interactions are weak, this theory is exactly soluble. The theory incorporates in a consistent way, the surface-charging mechanism and the fluctuations in the electrostatic field that correspond to the zero-frequency component of the van der Waals force. It is shown that these terms lead to a Casimir-like attraction that can be sufficiently large to explain the transition between the common black film to a Newton black film

  7. Chaotic fluctuations in mathematical economics

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Hiroyuki, E-mail: yoshida.hiroyuki@nihon-u.ac.jp [College of Economics, Nihon University, Chiyoda-ku, Tokyo 101-8360 (Japan)

    2011-03-01

    In this paper we examine a Cournot duopoly model, which expresses the strategic interaction between two firms. We formulate the dynamic adjustment process and investigate the dynamic properties of the stationary point. By introducing a memory mechanism characterized by distributed lag functions, we presuppose that each firm makes production decisions in a cautious manner. This implies that we have to deal with the system of integro-differential equations. By means of numerical simulations we show the occurrence of chaotic fluctuations in the case of fixed delays.

  8. An Objective Fluctuation Score for Parkinson's Disease

    Science.gov (United States)

    Horne, Malcolm K.; McGregor, Sarah; Bergquist, Filip

    2015-01-01

    Introduction Establishing the presence and severity of fluctuations is important in managing Parkinson’s Disease yet there is no reliable, objective means of doing this. In this study we have evaluated a Fluctuation Score derived from variations in dyskinesia and bradykinesia scores produced by an accelerometry based system. Methods The Fluctuation Score was produced by summing the interquartile range of bradykinesia scores and dyskinesia scores produced every 2 minutes between 0900-1800 for at least 6 days by the accelerometry based system and expressing it as an algorithm. Results This Score could distinguish between fluctuating and non-fluctuating patients with high sensitivity and selectivity and was significant lower following activation of deep brain stimulators. The scores following deep brain stimulation lay in a band just above the score separating fluctuators from non-fluctuators, suggesting a range representing adequate motor control. When compared with control subjects the score of newly diagnosed patients show a loss of fluctuation with onset of PD. The score was calculated in subjects whose duration of disease was known and this showed that newly diagnosed patients soon develop higher scores which either fall under or within the range representing adequate motor control or instead go on to develop more severe fluctuations. Conclusion The Fluctuation Score described here promises to be a useful tool for identifying patients whose fluctuations are progressing and may require therapeutic changes. It also shows promise as a useful research tool. Further studies are required to more accurately identify therapeutic targets and ranges. PMID:25928634

  9. Modelling Interglacial Climate

    DEFF Research Database (Denmark)

    Pedersen, Rasmus Anker

    the impact of a changing sea ice cover. The first part focusses on the last interglacial climate (125,000 years before present) which was characterized by substantial warming at high northern latitudes due to an increased insolation during summer. The simulations reveal that the oceanic changes dominate......Past warm climate states could potentially provide information on future global warming. The past warming was driven by changed insolation rather than an increased greenhouse effect, and thus the warm climate states are expected to be different. Nonetheless, the response of the climate system......, with maximum warming occurring in winter. The three scenarios all affect the climate beyond the Arctic, especially the mid-latitude circulation which is sensitive to the location of the ice loss. Together, the results presented in this thesis illustrate that the changes in the Arctic sea ice cover...

  10. Influence of temperature fluctuations on equilibrium ice sheet volume

    Science.gov (United States)

    Bøgeholm Mikkelsen, Troels; Grinsted, Aslak; Ditlevsen, Peter

    2018-01-01

    Forecasting the future sea level relies on accurate modeling of the response of the Greenland and Antarctic ice sheets to changing temperatures. The surface mass balance (SMB) of the Greenland Ice Sheet (GrIS) has a nonlinear response to warming. Cold and warm anomalies of equal size do not cancel out and it is therefore important to consider the effect of interannual fluctuations in temperature. We find that the steady-state volume of an ice sheet is biased toward larger size if interannual temperature fluctuations are not taken into account in numerical modeling of the ice sheet. We illustrate this in a simple ice sheet model and find that the equilibrium ice volume is approximately 1 m SLE (meters sea level equivalent) smaller when the simple model is forced with fluctuating temperatures as opposed to a stable climate. It is therefore important to consider the effect of interannual temperature fluctuations when designing long experiments such as paleo-spin-ups. We show how the magnitude of the potential bias can be quantified statistically. For recent simulations of the Greenland Ice Sheet, we estimate the bias to be 30 Gt yr-1 (24-59 Gt yr-1, 95 % credibility) for a warming of 3 °C above preindustrial values, or 13 % (10-25, 95 % credibility) of the present-day rate of ice loss. Models of the Greenland Ice Sheet show a collapse threshold beyond which the ice sheet becomes unsustainable. The proximity of the threshold will be underestimated if temperature fluctuations are not taken into account. We estimate the bias to be 0.12 °C (0.10-0.18 °C, 95 % credibility) for a recent estimate of the threshold. In light of our findings it is important to gauge the extent to which this increased variability will influence the mass balance of the ice sheets.

  11. Currency speculation and dollar fluctuations

    Directory of Open Access Journals (Sweden)

    Stephan Schulmeister

    1988-12-01

    Full Text Available In this study the reasons behind the wide fluctuations of the dollar exchange rate following the breakdown of the Bretton Woods system, for the most part unexplained by the prevailing exchange rate theories, are explored. To do so, the author investigates the exchange rate between the two most traded currencies, the dollar and the deutschemark, from 1973 to 1988. In the first part, the pattern of the daily exchange rate movements is examined to show that a sequence of upward and downward trends interrupted by non-directional movements is typical of exchange rate dynamics in the short run. Moreover, this pattern is systemically exploited through currency speculation, particularly through the use of “technical analysis”. In the second part, the author focuses on the medium-term, arguing that fluctuations can be explained as the result of interacting disequilibria in the goods and asset markets. Although currency speculation has been systemically profitable for most currencies, it should be considered to be destabilizing since the sequence of price runs caused large and persistent deviations of exchange rates from their equilibrium values (purchasing power parity.

  12. Entropic fluctuations in DNA sequences

    Science.gov (United States)

    Thanos, Dimitrios; Li, Wentian; Provata, Astero

    2018-03-01

    The Local Shannon Entropy (LSE) in blocks is used as a complexity measure to study the information fluctuations along DNA sequences. The LSE of a DNA block maps the local base arrangement information to a single numerical value. It is shown that despite this reduction of information, LSE allows to extract meaningful information related to the detection of repetitive sequences in whole chromosomes and is useful in finding evolutionary differences between organisms. More specifically, large regions of tandem repeats, such as centromeres, can be detected based on their low LSE fluctuations along the chromosome. Furthermore, an empirical investigation of the appropriate block sizes is provided and the relationship of LSE properties with the structure of the underlying repetitive units is revealed by using both computational and mathematical methods. Sequence similarity between the genomic DNA of closely related species also leads to similar LSE values at the orthologous regions. As an application, the LSE covariance function is used to measure the evolutionary distance between several primate genomes.

  13. Fractional Stochastic Differential Equations Satisfying Fluctuation-Dissipation Theorem

    Science.gov (United States)

    Li, Lei; Liu, Jian-Guo; Lu, Jianfeng

    2017-10-01

    We propose in this work a fractional stochastic differential equation (FSDE) model consistent with the over-damped limit of the generalized Langevin equation model. As a result of the `fluctuation-dissipation theorem', the differential equations driven by fractional Brownian noise to model memory effects should be paired with Caputo derivatives, and this FSDE model should be understood in an integral form. We establish the existence of strong solutions for such equations and discuss the ergodicity and convergence to Gibbs measure. In the linear forcing regime, we show rigorously the algebraic convergence to Gibbs measure when the `fluctuation-dissipation theorem' is satisfied, and this verifies that satisfying `fluctuation-dissipation theorem' indeed leads to the correct physical behavior. We further discuss possible approaches to analyze the ergodicity and convergence to Gibbs measure in the nonlinear forcing regime, while leave the rigorous analysis for future works. The FSDE model proposed is suitable for systems in contact with heat bath with power-law kernel and subdiffusion behaviors.

  14. Driving reconnection in sheared magnetic configurations with forced fluctuations

    Science.gov (United States)

    Pongkitiwanichakul, Peera; Makwana, Kirit D.; Ruffolo, David

    2018-02-01

    We investigate reconnection of magnetic field lines in sheared magnetic field configurations due to fluctuations driven by random forcing by means of numerical simulations. The simulations are performed with an incompressible, pseudo-spectral magnetohydrodynamics code in 2D where we take thick, resistively decaying, current-sheet like sheared magnetic configurations which do not reconnect spontaneously. We describe and test the forcing that is introduced in the momentum equation to drive fluctuations. It is found that the forcing does not change the rate of decay; however, it adds and removes energy faster in the presence of the magnetic shear structure compared to when it has decayed away. We observe that such a forcing can induce magnetic reconnection due to field line wandering leading to the formation of magnetic islands and O-points. These reconnecting field lines spread out as the current sheet decays with time. A semi-empirical formula is derived which reasonably explains the formation and spread of O-points. We find that reconnection spreads faster with stronger forcing and longer correlation time of forcing, while the wavenumber of forcing does not have a significant effect. When the field line wandering becomes large enough, the neighboring current sheets with opposite polarity start interacting, and then the magnetic field is rapidly annihilated. This work is useful to understand how forced fluctuations can drive reconnection in large scale current structures in space and astrophysical plasmas that are not susceptible to reconnection.

  15. Holocene lake-level fluctuations of Lake Aricota, Southern Peru

    Science.gov (United States)

    Placzek, C.; Quade, Jay; Betancourt, J.L.

    2001-01-01

    Lacustrine deposits exposed around Lake Aricota, Peru (17?? 22???S), a 7.5-km2 lake dammed by debris flows, provide a middle to late Holocene record of lake-level fluctuations. Chronological context for shoreline deposits was obtained from radiocarbon dating of vascular plant remains and other datable material with minimal 14C reservoir effects (Titicaca (16?? S), which is only 130 km to the northeast and shares a similar climatology. Comparisons with other marine and terrestrial records highlight emerging contradictions over the nature of mid-Holocene climate in the central Andes. ?? 2001 University of Washington.

  16. World Regionalization of Climate Change(1961–2010)

    Institute of Scientific and Technical Information of China (English)

    Peijun; Shi; Shao; Sun; Daoyi; Gong; Tao; Zhou

    2016-01-01

    Traditional climate classification or regionalization characterizes the mean state of climate condition, which cannot meet the demand of addressing climate change currently. We have developed a climate change classification method, as well as the fundamental principles, an indicator system, and mapping techniques of climate change regionalization. This study used annual mean temperature and total precipitation as climatic indices, and linear trend and variation change as change indices to characterize climate change quantitatively. The study has proposed a scheme for world climate change regionalization based on a half century of climate data(1961–2010). Level-I regionalization divides the world into 12 tendency zones based on the linear trend of climate, level-II regionalization resulted in 28 fluctuation regions based on the variation change of climate. Climate change regionalization provides a scientific basis for countries and regions to develop plans for adapting to climate change, especially for managing climate-related disaster or environmental risks.

  17. Hydrodynamical fluctuations in smooth shear flows

    International Nuclear Information System (INIS)

    Chagelishvili, G.D.; Khujadze, G.R.; Lominadze, J.G.

    1999-11-01

    Background of hydrodynamical fluctuations in a intrinsically/stochastically forced, laminar, uniform shear flow is studied. The employment of so-called nonmodal mathematical analysis makes it possible to represent the background of fluctuations in a new light and to get more insight into the physics of its formation. The basic physical processes responsible for the formation of vortex and acoustic wave fluctuation backgrounds are analyzed. Interplay of the processes at low and moderate shear rates is described. Three-dimensional vortex fluctuations around a given macroscopic state are numerically calculated. The correlation functions of the fluctuations of physical quantities are analyzed. It is shown that there exists subspace D k in the wave-number space (k-space) that is limited externally by spherical surface with radius k ν ≡ A/ν (where A is the velocity shear parameter, ν - the kinematic viscosity) in the nonequilibrium open system under study. The spatial Fourier harmonics of vortex as well as acoustic wave fluctuations are strongly subjected by flow shear (by the open character of the system) at wave-numbers satisfying the condition k ν . Specifically it is shown that in D k : The fluctuations are non-Markovian; the spatial spectral density of energy of the vortex fluctuations by far exceeds the white-noise; the term of a new type associated to the hydrodynamical fluctuation of velocity appears in the correlation function of pressure; the fluctuation background of the acoustic waves is completely different at low and moderate shear rates (at low shear rates it is reduced in D k in comparison to the uniform (non-shear) flow; at moderate shear rates it it comparable to the background of the vortex fluctuations). The fluctuation background of both the vortex and the acoustic wave modes is anisotropic. The possible significance of the fluctuation background of vortices for the subcritical transition to turbulence and Brownian motion of small macroscopic

  18. Elastically driven intermittent microscopic dynamics in soft solids

    Science.gov (United States)

    Bouzid, Mehdi; Colombo, Jader; Barbosa, Lucas Vieira; Del Gado, Emanuela

    2017-06-01

    Soft solids with tunable mechanical response are at the core of new material technologies, but a crucial limit for applications is their progressive aging over time, which dramatically affects their functionalities. The generally accepted paradigm is that such aging is gradual and its origin is in slower than exponential microscopic dynamics, akin to the ones in supercooled liquids or glasses. Nevertheless, time- and space-resolved measurements have provided contrasting evidence: dynamics faster than exponential, intermittency and abrupt structural changes. Here we use 3D computer simulations of a microscopic model to reveal that the timescales governing stress relaxation, respectively, through thermal fluctuations and elastic recovery are key for the aging dynamics. When thermal fluctuations are too weak, stress heterogeneities frozen-in upon solidification can still partially relax through elastically driven fluctuations. Such fluctuations are intermittent, because of strong correlations that persist over the timescale of experiments or simulations, leading to faster than exponential dynamics.

  19. Fluctuating hyperfine interactions: computational implementation

    International Nuclear Information System (INIS)

    Zacate, M. O.; Evenson, W. E.

    2010-01-01

    A library of computational routines has been created to assist in the analysis of stochastic models of hyperfine interactions. We call this library the stochastic hyperfine interactions modeling library (SHIML). It provides routines written in the C programming language that (1) read a text description of a model for fluctuating hyperfine fields, (2) set up the Blume matrix, upon which the evolution operator of the system depends, and (3) find the eigenvalues and eigenvectors of the Blume matrix so that theoretical spectra of experimental hyperfine interaction measurements can be calculated. Example model calculations are included in the SHIML package to illustrate its use and to generate perturbed angular correlation spectra for the special case of polycrystalline samples when anisotropy terms of higher order than A 22 can be neglected.

  20. Fluctuating nonlinear hydrodynamics of flocking

    Science.gov (United States)

    Yadav, Sunil Kumar; Das, Shankar P.

    2018-03-01

    Starting from a microscopic model, the continuum field theoretic description of the dynamics of a system of active ingredients or "particles" is presented. The equations of motion for the respective collective densities of mass and momentum follow exactly from that of a single element in the flock. The single-particle dynamics has noise and anomalous momentum dependence in its frictional terms. The equations for the collective densities are averaged over a local equilibrium distribution to obtain the corresponding coarse grained equations of fluctuating nonlinear hydrodynamics (FNH). The latter are the equations used frequently for describing active systems on the basis of intuitive arguments. The transport coefficients which appear in the macroscopic FNH equations are determined in terms of the parameters of the microscopic dynamics.

  1. Generic analysis of kinetically driven inflation

    Science.gov (United States)

    Saitou, Rio

    2018-04-01

    We perform a model-independent analysis of kinetically driven inflation (KDI) which (partially) includes generalized G-inflation and ghost inflation. We evaluate the background evolution splitting into the inflationary attractor and the perturbation around it. We also consider the quantum fluctuation of the scalar mode with a usual scaling and derive the spectral index, ignoring the contribution from the second-order products of slow-roll parameters. Using these formalisms, we find that within our generic framework the models of KDI which possess the shift symmetry of scalar field cannot create the quantum fluctuation consistent with the observation. Breaking the shift symmetry, we obtain a few essential conditions for viable models of KDI associated with the graceful exit.

  2. Impact of long-term climate change on a deep geological repository for spent nuclear fuel

    International Nuclear Information System (INIS)

    Boulton, G.S.; Kautsky, U.; Moren, L.; Wallroth, T.

    2001-05-01

    The radioactivity of spent nuclear fuel will decay over a period of time (100,000 years or longer) in which we expect major environmental change. Climatically driven changes such as glaciation, permafrost and changes in sea level will affect the subsurface environment and must therefore be considered in performance and safety assessments. We regard the state of climate to be determined by the climate system, comprising the atmosphere, the biosphere, the oceans, the ice sheets and the surface of the lithosphere. Climate can change as a consequence of external forcing or as a consequence of the internal dynamics. The changes in the past show a complex cyclical pattern with repetitive periodicities and magnitudes of change. On the relatively long time scale which is of concern in this report climate changes are believed to be triggered by changes in insolation due to cyclical changes in the earth's orbit around the sun. This is referred to as the Milankovitch theory or the astronomical climate theory. A brief review of our knowledge of the climate system, proxy records and observations of past climate change is presented in the report. The most extreme departures from modern environmental conditions in Sweden have occurred during the cold, glacial cycles with ice sheets covering the whole of Sweden. As part of SKB's palaeohydrogeological research programme a time-dependent, thermo-mechanically coupled model of ice sheet behaviour has been developed in order to simulate past fluctuations of the Scandinavian ice sheet and forecast its future. The ice sheet model can calculate the temperature field and isostatic response of the underlying bedrock, subglacial and proglacial permafrost and the subglacial melt rates. By connecting the glaciation model with hydrogeological and rock mechanical models, the response of the subsurface to climate change can be investigated. In this report the climate-driven environmental changes are represented as a series of successive climate-driven

  3. Impact of long-term climate change on a deep geological repository for spent nuclear fuel

    Energy Technology Data Exchange (ETDEWEB)

    Boulton, G.S. [Edinburgh Univ. (United Kingdom); Kautsky, U.; Moren, L. [Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden); Wallroth, T. [Bergab Consulting Geologists (Sweden)

    2001-05-01

    The radioactivity of spent nuclear fuel will decay over a period of time (100,000 years or longer) in which we expect major environmental change. Climatically driven changes such as glaciation, permafrost and changes in sea level will affect the subsurface environment and must therefore be considered in performance and safety assessments. We regard the state of climate to be determined by the climate system, comprising the atmosphere, the biosphere, the oceans, the ice sheets and the surface of the lithosphere. Climate can change as a consequence of external forcing or as a consequence of the internal dynamics. The changes in the past show a complex cyclical pattern with repetitive periodicities and magnitudes of change. On the relatively long time scale which is of concern in this report climate changes are believed to be triggered by changes in insolation due to cyclical changes in the earth's orbit around the sun. This is referred to as the Milankovitch theory or the astronomical climate theory. A brief review of our knowledge of the climate system, proxy records and observations of past climate change is presented in the report. The most extreme departures from modern environmental conditions in Sweden have occurred during the cold, glacial cycles with ice sheets covering the whole of Sweden. As part of SKB's palaeohydrogeological research programme a time-dependent, thermo-mechanically coupled model of ice sheet behaviour has been developed in order to simulate past fluctuations of the Scandinavian ice sheet and forecast its future. The ice sheet model can calculate the temperature field and isostatic response of the underlying bedrock, subglacial and proglacial permafrost and the subglacial melt rates. By connecting the glaciation model with hydrogeological and rock mechanical models, the response of the subsurface to climate change can be investigated. In this report the climate-driven environmental changes are represented as a series of successive

  4. Interplanetary Alfvenic fluctuations: A stochastic model

    International Nuclear Information System (INIS)

    Barnes, A.

    1981-01-01

    The strong alignment of the average directions of minimum magnetic variance and mean magnetic field in interplanetary Alfvenic fluctuations is inconsistent with the usual wave-propagation models. We investigate the concept of minimum variance for nonplanar Alfvenic fluctuations in which the field direction varies stochastically. It is found that the tendency of the minimum variance and mean field directions to be aligned may be purely a consequence of the randomness of the field direction. In particular, a well-defined direction of minimum variance does not imply that the fluctuations are necessarily planar. The fluctuation power spectrum is a power law for frequencies much higher than the inverse of the correlation time. The probability distribution of directions a randomly fluctuating field of constant magnitude is calculated. A new approach for observational studies of interplanetary fluctuations is suggested

  5. Measurements of fluctuations in the flux of runaway electrons to the PLT limiter

    International Nuclear Information System (INIS)

    Barnes, C.W.; Strachan, J.D.

    1982-07-01

    Fluctuations in the flux of runaway electrons to the limiter have been measured during many PLT discharges. Oscillations at 60, 120, and 720 Hz are driven by variations in the vertical magnetic field which moves the plasma major radius. Fluctuations are seen in the range of 2 → 20 kHz due to MHD magnetic islands which extend to the plasma surface. A continuous spectrum of fluctuations is observed up to 200 kHz which correlates with drift-wave turbulence. The magnitude of the driven fluctuations can be used to measure transport properties of the runaway electrons. The amplitude of electron motion due to the MHD and drift-wave oscillations, and hence a measure of the radial size of the instability, can be determined as a function of frequency. The slope of the frequency power spectrum of the drift-wave-induced fluctuations steepens with increasing runaway electron drift orbit displacement during the current drop at the end of the discharge, and as the power in the MHD oscillations increases. A magnetic probe was used to confirm the presence of oscillating magnetic fields capable of perturbing the electron orbits

  6. Charge Fluctuations of an Uncharged Black Hole

    OpenAIRE

    Schiffer, Marcelo

    2016-01-01

    In this paper we calculate charge fluctuations of a Schwarzschild black-hole of mass $M$ confined within a perfectly reflecting cavity of radius R in thermal equilibrium with various species of radiation and fermions . Charge conservation is constrained by a Lagrange multiplier (the chemical potential). Black hole charge fluctuations are expected owing to continuous absorption and emission of particles by the black hole. For black holes much more massive than $10^{16} g$ , these fluctuations ...

  7. Implication of climate change for the persistence of raptors in arid savanna

    Energy Technology Data Exchange (ETDEWEB)

    Wichmann, M.C.; Wissel, C. [UFZ-Center for Environmental Research, Dept. of Ecological Modelling, Leipzig (Germany); Jeltsch, F. [Univ. of Potsdam, Inst. for Biochemistry and Biology, Potsdam (Germany); Dean, W.R.J. [Univ. of Cape Town, Percy FitzPatrick Inst. of African Ornithology, Rondebosch (South Africa); Moloney, K.A. [Iowa State Univ., Dept. of Botany, Ames, IA (United States)

    2003-07-01

    Arid savannas are regarded as one of the ecosystems most likely to be affected by climate change. In these dry conditions, even top predators like raptors are affected by water availability and precipitation. However, few research initiatives have a adressed the question of how climate change will affect population dynamics and extinction risk of particular species in and ecosystems. Here, we use an individual-oriented modeling approach to conduct experiments on the population dynamics of long lived raptors. We investigate the potential impact of precipitation variation caused by climate change on raptors in and savanna using the tawny eagle (Aquila rapax) in the southern Kalahari as a case study. We simulated various modifications of precipitation scenarios predicted for climate change, such as lowered annual precipitation mean, increased inter-annual variation and increased auto-correlation in precipitation. We found a high impact of these modifications on extinction risk of tawny eagles, with reduced population persistence in most cases. Decreased mean annual precipitation and increased inter-annual variation both caused dramatic decreases in population persistence. Increased autocorrelation in precipitation led only to slightly accelerated extinction of simulated populations. Finally. for various patterns of periodically fluctuating precipitation, we found both increased and decreased population persistence. In summary, our results suggest that the impacts on raptor population dynamics and survival caused by climate change in and savannas will be great. We emphasize that even if under climate change the mean annual precipitation remains constant but the inter-annual variation increases the persistence of raptor populations in and savannas will decrease considerably. This suggests a new dimension, of climate change driven impacts on population persistence and consequently on biodiversity. However, more investigations on particular species and/or species groups

  8. Wind fluctuations over the North Sea

    DEFF Research Database (Denmark)

    Vincent, Claire Louise; Pinson, Pierre; Giebel, Gregor

    2011-01-01

    Climatological patterns in wind speed fluctuations with periods of 1 min to 10 h are analysed using data from a meteorological mast in the Danish North Sea. Fluctuations on these time scales are of particular relevance to the effective management of the power supply from large wind farms. The Hil......Climatological patterns in wind speed fluctuations with periods of 1 min to 10 h are analysed using data from a meteorological mast in the Danish North Sea. Fluctuations on these time scales are of particular relevance to the effective management of the power supply from large wind farms...

  9. Neutrino propagation in a fluctuating sun

    International Nuclear Information System (INIS)

    Burgess, C.P.; Michaud, D.

    1997-01-01

    We adapt to neutrino physics a general formulation for particle propagation in fluctuating media, initially developed for applications to electromagnetism and neutron optics. In leading approximation this formalism leads to the usual MSW effective Hamiltonian governing neutrino propagation through a medium. Next-to-leading contributions describe deviations from this description, which arise due to neutrino interactions with fluctuations in the medium. We compute these corrections for two types of fluctuations: (i) microscopic thermal fluctuations and (ii) macroscopic fluctuations in the medium s density. While the first of these reproduces standard estimates, which are negligible for applications to solar neutrinos, we find that the second can be quite large, since it grows in size with the correlation length of the fluctuation. We consider two models in some detail. For fluctuations whose correlations extend only over a local region in space of length l, appreciable effects for MSW oscillations arise if (δn/n) 2 l approx-gt 100m or so. Alternatively, a crude model of helioseismic p-waves gives appreciable effects only when (δn/n)approx-gt 1%. In general the dominant effect is to diminish the quality of the resonance, making the suppression of the 7 Be neutrinos a good experimental probe of fluctuations deep within the sun. Fluctuations can also provide a new mechanism for reducing the solar neutrino flux, giving an energy-independent suppression factor of 1/2 away from the resonant region, even for small vacuum mixing angles. copyright 1997 Academic Press, Inc

  10. Non-Gaussian conductivity fluctuations in semiconductors

    International Nuclear Information System (INIS)

    Melkonyan, S.V.

    2010-01-01

    A theoretical study is presented on the statistical properties of conductivity fluctuations caused by concentration and mobility fluctuations of the current carriers. It is established that mobility fluctuations result from random deviations in the thermal equilibrium distribution of the carriers. It is shown that mobility fluctuations have generation-recombination and shot components which do not satisfy the requirements of the central limit theorem, in contrast to the current carrier's concentration fluctuation and intraband component of the mobility fluctuation. It is shown that in general the mobility fluctuation consist of thermal (or intraband) Gaussian and non-thermal (or generation-recombination, shot, etc.) non-Gaussian components. The analyses of theoretical results and experimental data from literature show that the statistical properties of mobility fluctuation and of 1/f-noise fully coincide. The deviation from Gaussian statistics of the mobility or 1/f fluctuations goes hand in hand with the magnitude of non-thermal noise (generation-recombination, shot, burst, pulse noises, etc.).

  11. Three dimensional numerical simulation of a full scale CANDU reactor moderator to study temperature fluctuations

    International Nuclear Information System (INIS)

    Sarchami, Araz; Ashgriz, Nasser; Kwee, Marc

    2014-01-01

    Highlights: • 3D model of a Candu reactor is modeled to investigate flow distribution. • The results show the temperature distribution is not symmetrical. • Temperature contours show the hot regions at the top left-hand side of the tank. • Interactions of momentum flows and buoyancy flows create circulation zones. • The results indicate that the moderator tank operates in the buoyancy