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  • 1
    Publication Date: 2023-09-12
    Description: Supervolcano eruptions have occurred throughout Earth’s history and have major environmental impacts. These impacts are mostly associated with the attenuation of visible sunlight by stratospheric sulfate aerosols, which causes cooling and deceleration of the water cycle. Supereruptions have been assumed to cause so-called volcanic winters that act as primary evolutionary factors through ecosystem disruption and famine, however, winter conditions alone may not be sufficient to cause such disruption. Here we use Earth system model simulations to show that stratospheric sulfur emissions from the Toba supereruption 74,000 years ago caused severe stratospheric ozone loss through a radiation attenuation mechanism that only moderately depends on the emission magnitude. The Toba plume strongly inhibited oxygen photolysis, suppressing ozone formation in the tropics, where exceptionally depleted ozone conditions persisted for over a year. This effect, when combined with volcanic winter in the extra-tropics, can account for the impacts of supereruptions on ecosystems and humanity.
    Description: Stratospheric sulfur emissions from the Toba supereruption about 74,000 years ago suppressed ozone formation which caused severe tropical ozone layer depletion and enhanced solar ultraviolet radiation stress, according to Earth system model simulations.
    Description: King Abdullah University of Science and Technology (KAUST) https://doi.org/10.13039/501100004052
    Description: http://hdl.handle.net/10754/667404
    Description: https://github.com/SeregaOsipov/NASA-GISS-ModelE/releases/tag/toba_o3
    Description: https://simplex.giss.nasa.gov/snapshots/
    Keywords: ddc:551 ; Atmospheric chemistry ; Natural hazards ; Palaeoclimate ; Volcanology
    Language: English
    Type: doc-type:article
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6529-6529 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: MicroMAG-2D (version 2.0) system has been developed for investigations of statics and dynamics of two-dimensional 180° domain walls in the thin ferromagnetic films with arbitrary uniaxial anisotropy. This system is intended for developers of magnetic memory devices, physicists (experimentators and theoreticians), and may be used for illustration at high school (university) educational process. Static structure is a result of solving of nonlinear variational micromagnetic problem with magnetostatic interaction. Domain wall dynamics is computed by direct integration of Landau–Lifshits–Gilbert equation. Computational method used fast algorithm for demagnetization field and unconditionally stable scheme for temporal integration. Domain wall is keeping in the center of computational region by shadowing method.1 MicroMAG-2D system consists of (a) initial data generation module; (b) computational module; (c) Editor/Viewer module; (d) Animator module. System requirements: IBM PC AT compatible (Intel 80386/387 or 80486 processor).
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6093-6093 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dynamics of magnetic domain walls is a subject of intensive computer simulation of last years. Now it is well understood, that strongly twisted structures (like horizontal Bloch lines) of domain walls can be created. In some cases this HBL can have a very small localization region. Appearance of such inconvenient objects, like HBL, states a new scale for numerical model and it required a significant increase of node number for the uniform grid model. The main idea of the new adaptive computational method for LLG equation for two-dimensional (2D) domain wall dynamics is to inject and delete additional nodes only to the HBL localization region, using a special target function, which is based on the twisting angle of the domain wall. Node injection occurs when HBL is created, and node deleting occurs when HBL is breakthrough. The conjugated gradient method was used for fast demagnetization field computation by two Dirichlet problems for Poisson equations. We show an effective application of this method for 2D computations of domain wall dynamics for bubble film with parameters: Q=4, D=3(l), α=0.2, h=(0,8,−3), (Ms) [Here Q is the quality factor of the film, D the film thickness in characterization units, α the damping parameter, h the external magnetic field in Ms units, 8(Ms) the value of in-plane magnetic field via chirality, −3(Ms) is the driven magnetic field.] We found that HBL has very strong localization in this case. To carry out this computation we need nx×nz=65×162 for uniform grid sytem, and only nx×nz=33×60 for adaptive grid system. A color computer movie was created for this case. The new mechanics of HBL generation and breakthrough is discussed. Here we can see significant asymmetry in HBL generation: two HBL created at one moment at the lower surface of the film, but upper HBL goes to the upper surface of the film and the lower goes to the opposite direction. The next pair of HBL is created at the lower surface of the film at the same place.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2021-10-07
    Description: Volcanic eruptions are an important climate driver. The impact of Pinatubo-sized eruptions has been observed and is well constrained. The magnitude and duration of volcanic winter effects after supereruptions such as Toba remain disputed due to disagreement between the strong cooling predicted by models and much milder climate perturbations according to the paleodata. Here we present a reevaluated climate impact of a Toba-sized supereruption based on up-to-date GISS ModelE simulations. In this study, we account for all known primary mechanisms that govern the evolution of the volcanic plume and their nonlinear interactions. The SO 2 radiative effects are evaluated for the first time in coupled climate simulations with the interactive atmospheric chemistry module. We found that SO 2 effects on photochemistry, dynamics, and radiative forcing are especially prominent. Due to strong absorption in ultraviolet, SO 2 feedback on photochemistry partially offsets the limiting effect associated with aerosol microphysical processes. SO 2 greenhouse warming soothes the radiative cooling exerted by sulfate aerosols. SO 2 absorption in the shortwave and longwave causes radiative heating and lofting of the volcanic plume, and boosts the efficiency of SO 2 impact on photochemistry. Our analysis shows that SO 2 lifetime and magnitude of effects scale up and increase with the amount of emitted material. For a Pinatubo-sized eruption, SO 2 feedbacks on chemistry and dynamics are relevant only during the initial stage of the volcanic plume evolution, while local SO 2 concentrations are high. For a Toba-sized eruption, SO 2 effects are as important as sulfate aerosols and produce a less extreme volcanic winter.
    Keywords: 551.5 ; supereruption ; Toba ; volcanic winter ; sulfate aerosols ; climate impact ; sulfur dioxide
    Language: English
    Type: map
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