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Sökning: L773:1752 0894 OR L773:1752 0908 > Linköpings universitet

  • Resultat 1-5 av 5
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1.
  • Acosta Navarro, Juan Camilo, et al. (författare)
  • Amplification of Arctic warming by past air pollution reductions in Europe
  • 2016
  • Ingår i: Nature Geoscience. - : Nature Publishing Group. - 1752-0894 .- 1752-0908. ; 9:4, s. 277-
  • Tidskriftsartikel (refereegranskat)abstract
    • The Arctic region is warming considerably faster than the rest of the globe(1), with important consequences for the ecosystems(2) and human exploration of the region(3). However, the reasons behind this Arctic amplification are not entirely clear(4). As a result of measures to enhance air quality, anthropogenic emissions of particulate matter and its precursors have drastically decreased in parts of the Northern Hemisphere over the past three decades(5). Here we present simulations with an Earth system model with comprehensive aerosol physics and chemistry that show that the sulfate aerosol reductions in Europe since 1980 can potentially explain a significant fraction of Arctic warming over that period. Specifically, the Arctic region receives an additional 0.3Wm(-2) of energy, and warms by 0.5 degrees C on annual average in simulations with declining European sulfur emissions in line with historical observations, compared with a model simulation with fixed European emissions at 1980 levels. Arctic warming is amplified mainly in fall and winter, but the warming is initiated in summer by an increase in incoming solar radiation as well as an enhanced poleward oceanic and atmospheric heat transport. The simulated summertime energy surplus reduces sea-ice cover, which leads to a transfer of heat from the Arctic Ocean to the atmosphere. We conclude that air quality regulations in the Northern Hemisphere, the ocean and atmospheric circulation, and Arctic climate are inherently linked.
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2.
  • Barros, Nathan, et al. (författare)
  • Carbon emission from hydroelectric reservoirs linked to reservoir age and latitude
  • 2011
  • Ingår i: Nature Geoscience. - : Nature Publishing Group. - 1752-0894 .- 1752-0908. ; 4:9, s. 593-596
  • Tidskriftsartikel (refereegranskat)abstract
    • Hydroelectric reservoirs cover an area of 3.4 x 10(5) km(2) and comprise about 20% of all reservoirs. In addition, they contain large stores of formerly terrestrial organic carbon. Significant amounts of greenhouse gases are emitted(2), especially in the early years following reservoir creation, but the global extent of these emissions is poorly known. Previous estimates of emissions from all types of reservoir indicate that these human-made systems emit 321 Tg of carbon per year (ref. 4). Here we assess the emissions of carbon dioxide and methane from hydroelectric reservoirs, on the basis of data from 85 globally distributed hydroelectric reservoirs that account for 20% of the global area of these systems. We relate the emissions to reservoir age, location biome, morphometric features and chemical status. We estimate that hydroelectric reservoirs emit about 48 Tg C as CO(2) and 3 Tg C as CH(4), corresponding to 4% of global carbon emissions from inland waters. Our estimates are smaller than previous estimates on the basis of more limited data. Carbon emissions are correlated to reservoir age and latitude, with the highest emission rates from the tropical Amazon region. We conclude that future emissions will be highly dependent on the geographic location of new hydroelectric reservoirs.
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3.
  • Belonoshko, Anatoly B., et al. (författare)
  • Stabilization of body-centred cubic iron under inner-core conditions
  • 2017
  • Ingår i: Nature Geoscience. - : Nature Publishing Group. - 1752-0894 .- 1752-0908. ; 10:4, s. 312-
  • Tidskriftsartikel (refereegranskat)abstract
    • The Earth's solid core is mostly composed of iron. However, despite being central to our understanding of core properties, the stable phase of iron under inner-core conditions remains uncertain. The two leading candidates are hexagonal close-packed and body-centred cubic (bcc) crystal structures, but the dynamic and thermodynamic stability of bcc iron under inner-core conditions has been challenged. Here we demonstrate the stability of the bcc phase of iron under conditions consistent with the centre of the core using ab initio molecular dynamics simulations. We find that the bcc phase is stabilized at high temperatures by a diffusion mechanism that arises due to the dynamical instability of the phase at lower temperatures. On the basis of our simulations, we reinterpret experimental data as support for the stability of bcc iron under inner-core conditions. We suggest that the diffusion of iron atoms in solid state may explain both the anisotropy and the low shear modulus of the inner core.
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4.
  • Ekblad, Alf, 1957-, et al. (författare)
  • Deforestation releases old carbon
  • 2019
  • Ingår i: Nature Geoscience. - : Nature Publishing Group. - 1752-0894 .- 1752-0908. ; 12:7, s. 499-500
  • Tidskriftsartikel (refereegranskat)abstract
    • Abstract not available.
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5.
  • Wik, Martin, et al. (författare)
  • Climate-sensitive northern lakes and ponds are critical components of methane release
  • 2016
  • Ingår i: Nature Geoscience. - : NATURE PUBLISHING GROUP. - 1752-0894 .- 1752-0908. ; 9:2, s. 99-
  • Forskningsöversikt (refereegranskat)abstract
    • Lakes and ponds represent one of the largest natural sources of the greenhouse gas methane. By surface area, almost half of these waters are located in the boreal region and northwards. A synthesis of measurements of methane emissions from 733 lakes and ponds north of similar to 50 degrees N, combined with new inventories of inland waters, reveals that emissions from these high latitudes amount to around 16.5 Tg CH4 yr(-1) (12.4 Tg CH4-C yr(-1)). This estimate - from lakes and ponds alone - is equivalent to roughly two-thirds of the inverse model calculation of all natural methane sources in the region. Thermokarst water bodies have received attention for their high emission rates, but we find that post-glacial lakes are a larger regional source due to their larger areal extent. Water body depth, sediment type and ecoclimatic region are also important in explaining variation in methane fluxes. Depending on whether warming and permafrost thaw cause expansion or contraction of lake and pond areal coverage, we estimate that annual water body emissions will increase by 20-54% before the end of the century if ice-free seasons are extended by 20 days. We conclude that lakes and ponds are a dominant methane source at high northern latitudes.
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  • Resultat 1-5 av 5

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