| 1. |
- Barnes, Paul W., et al.
(författare)
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Ozone depletion, ultraviolet radiation, climate change and prospects for a sustainable future
- 2019
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Ingår i: Nature Sustainability. - : Springer Science and Business Media LLC. - 2398-9629. ; 2:7, s. 569-579
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Forskningsöversikt (refereegranskat)abstract
- © 2019, Springer Nature Limited. Changes in stratospheric ozone and climate over the past 40-plus years have altered the solar ultraviolet (UV) radiation conditions at the Earth’s surface. Ozone depletion has also contributed to climate change across the Southern Hemisphere. These changes are interacting in complex ways to affect human health, food and water security, and ecosystem services. Many adverse effects of high UV exposure have been avoided thanks to the Montreal Protocol with its Amendments and Adjustments, which have effectively controlled the production and use of ozone-depleting substances. This international treaty has also played an important role in mitigating climate change. Climate change is modifying UV exposure and affecting how people and ecosystems respond to UV; these effects will become more pronounced in the future. The interactions between stratospheric ozone, climate and UV radiation will therefore shift over time; however, the Montreal Protocol will continue to have far-reaching benefits for human well-being and environmental sustainability.
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| 2. |
- Tenzer, Robert, et al.
(författare)
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Analysis of the Refined CRUST1.0 Crustal Model and its Gravity Field
- 2015
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Ingår i: Surveys in geophysics. - : Springer Science and Business Media LLC. - 0169-3298 .- 1573-0956. ; 36:1, s. 139-165
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Forskningsöversikt (refereegranskat)abstract
- The global crustal model CRUST1.0 (refined using additional global datasets of the solid topography, polar ice sheets and geoid) is used in this study to estimate the average densities of major crustal structures. We further use this refined model to compile the gravity field quantities generated by the Earth's crustal structures and to investigate their spatial and spectral characteristics and their correlation with the crustal geometry in context of the gravimetric Moho determination. The analysis shows that the average crustal density is 2,830 kg/m(3), while it decreases to 2,490 kg/m(3) when including the seawater. The average density of the oceanic crust (without the seawater) is 2,860 kg/m(3), and the average continental crustal density (including the continental shelves) is 2,790 kg/m(3). The correlation analysis reveals that the gravity field corrected for major known anomalous crustal density structures has a maximum (absolute) correlation with the Moho geometry. The Moho signature in these gravity data is seen mainly at the long-to-medium wavelengths. At higher frequencies, the Moho signature is weakening due to a noise in gravity data, which is mainly attributed to crustal model uncertainties. The Moho determination thus requires a combination of gravity and seismic data. In global studies, gravimetric methods can help improving seismic results, because (1) large parts of the world are not yet sufficiently covered by seismic surveys and (2) global gravity models have a relatively high accuracy and resolution. In regional and local studies, the gravimetric Moho determination requires either a detailed crustal density model or seismic data (for a combined gravity and seismic data inversion). We also demonstrate that the Earth's long-wavelength gravity spectrum comprises not only the gravitational signal of deep mantle heterogeneities (including the core-mantle boundary zone), but also shallow crustal structures. Consequently, the application of spectral filtering in the gravimetric Moho determination will remove not only the gravitational signal of (unknown) mantle heterogeneities, but also the Moho signature at the long-wavelength gravity spectrum.
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| 3. |
- Pease, Victoria, et al.
(författare)
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Baltica in the Cryogenian, 850-650 Ma
- 2008
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Ingår i: Precambrian Research. - : Elsevier BV. - 0301-9268 .- 1872-7433. ; 160:1-2, s. 46-65
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Forskningsöversikt (refereegranskat)abstract
- This new tectonic synthesis provides a framework for understanding the dynamic evolution of Baltica and for constraining tectonic correlations within the context of the Neoproterozoic break-up of Rodinia–Pannotia. Cryogenian Baltica is described with respect to five geographic regions: the northwest, northeast, east, south, and southwest (modern coordinates). These geographic regions define three principal Cryogenian tectonic margins: a rifting northwestern margin, a passive northeastern margin, and a poorly understood southern margin. The northwest region is characterized by Neoproterozoic to lower Ordovician sedimentary successions deposited on Archean to late Mesoproterozoic crystalline complexes, reworked during Caledonian orogenesis. Lare Neoproterozoic to lower Ordovician sedimentary strata record the change from an alluvial setting to a marine environment, and eventually to a partially starved (?) turbidite basin. They document rifting from the Rodinian-Pannotian supercontinent, which was unsuccessful until ca. 620–550 Ma when voluminous dikes and mafic/ultramafic complexes were intruded. Baltica's northeastern and eastern regions document episodic intracratonic rifting throughout the Mesoproterozoic, followed by pericontinental passive margin deposition throughout the Cryogenian. In the northeast platformal and deeper-water basin deposits are preserved, whereas the eastern region was later affected by Paleozoic rifting and preserves only shelf deposits. The northeastern and eastern regions define Baltica's Cryogenian northeastern tectonic margin, which was an ocean-facing passive margin of the Rodinia–Pannotia supercontinent. It remained a passive margin until the onset of Timanian orogenesis at ca. 615 Ma, approximately synchronous with the time of Rodinia–Pannotia rifting. Baltica's southern and southwestern regions remain enigmatic and controversial. Precambrian basement is generally hidden beneath thick successions of Ediacaran and younger platform sediments. Similarities between these regions exist, however, and suggest that they may share a similar tectonic evolution in the Cryogenian and therefore define the southern tectonic margin of Baltica at this time. Paleo- to Mesoproterozic basement was affected by Neoproterozoic and younger tectonism, including Cryogenian (?) and Ediacaran rifting. This was followed by Ediacaran (ca. 550 Ma) passive margin sediment deposition at the time of Rodinia–Pannotia break-up, until Early Paleozoic accretion of allochthonous terranes record the transition from rifting to a compressional regime. Paleomagnetic and paleontological data are consistent with Baltica and Laurentia drifting together between ca. 750 and 550 Ma, when they had similar apparent polar wander paths. Microfossil assemblages along the eastern margin of Laurentia and the western margin of Baltica (modern coordinates), suggest proximity between these two margins at this time. At ca. 550 Ma, Laurentia and Baltica separated, consistent with paleomagnetic, paleontological, and geological data, and a late break-up for Rodinia–Pannotia.
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| 4. |
- Elming, Sten-åke, et al.
(författare)
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A palaeomagnetic and Ar-40/Ar-39 study of late precambrian sills in the SW part of the Amazonian craton: Amazonia in the Rodinia reconstruction
- 2009
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Ingår i: Geophysical Journal International. - 0956-540X .- 1365-246X. ; 178:1, s. 106-122
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Forskningsöversikt (refereegranskat)abstract
- A new key palaeomagnetic pole (Plat. = 64.3 degrees S, Plon. = 271.0 degrees E, N = 14, A(95) = 9.2 degrees; Q = 5) is calculated from a primary magnetization isolated in early Neoproterozoic Aguapei basic sills and dykes hosted by 1.3-1.0 Ga sedimentary rocks from the southwestern part of the Amazon craton. The characteristic remanence carried by stable, pseudo-single domain titanomagnetite shows two antipodal polarities that pass a reversals test. Magnetic anisotropy for most sites shows fabric orientations that are typical of sills, with horizontal magnetic foliations concordant to the flat-lying bedding of the host sedimentary rocks. Ar-40/Ar-39 analyses for one of the sills reveal a well-defined plateau age at 981 +/- 2 Myr. A tectonic reconstruction for Amazonia relative Laurentia based on this new pole 'is consistent with' a position of the present northwestern part of Amazonia attached with eastern Laurentia close to Greenland at ca. 981 Ma. On basis of palaeomagnetic and geological data, we propose a scenario where Amazonia moved northeastwards along the present southeast coast of Laurentia from ca. 1200 to 980 Ma. By 980 Ma, Amazonia is placed alongside Laurentia and Baltica, in a position similar to other reconstructions of Rodinia but with a significantly different orientation.
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| 5. |
- Pesonen, LJ, et al.
(författare)
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Palaeomagnetic configuration of continents during the Proterozoic
- 2003
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Ingår i: Tectonophysics. - 0040-1951 .- 1879-3266. ; 375:1-4, s. 289-324
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Forskningsöversikt (refereegranskat)abstract
- Palaeomagnetic data are used to study the configurations of continents during the Proterozoic. Applying stringent reliability criteria, the positions of the continents at 12 times in the 2.45- to 1.00-Ga period have been constructed. The continents lie predominantly in low to intermediate latitudes. The sedimentological indicators of palaeoclimate are generally consistent with the palaeomagnetic latitudes, with the exception of the Early Proterozoic, when low latitude glaciations took place on several continents. The Proterozoic continental configurations are generally in agreement with current geological models of the evolution of the continents. The data suggest that three large continental landmasses existed during the Proterozoic. The oldest one is the Neoarchaean Kenorland, which comprised at least Laurentia, Baltica, Australia and the Kalahari craton. The protracted breakup of Kenorland during the 2.45- to 2.10-Ga interval is manifested by mafic dykes and sedimentary rift-basins on many continents. The second 'supercontinental' landmass is Hudsonland (also known as Columbia). On the basis of purely palaeomagnetic data, this supercontinent consisted of Laurentia, Baltica, Ukraine, Amazonia and Australia and perhaps also Siberia, North China and Kalahari. Hudsonland existed from 1.83 to ca. 1.50-1.25 Ga. The youngest assembly is the Neoproterozoic supercontinent of Rodinia, which was formed by continent-continent collisions during similar to 1.10-1.00 Ga and which involved most of the continents. A new model for its assembly and configuration is presented, which suggests that multiple Grenvillian age collisions took place during 1.10-1.00 Ga. The configurations of Kenorland, Hudsonland and Rodinia depart from each other and also from the Pangaea assembly. The tectonic styles of their amalgamation are also different reflecting probable changes in sizes and thicknesses of the cratonic blocks as well as changes in the thermal conditions of the mantle through time. (C) 2003 Elsevier B.V. All rights reserved.
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| 6. |
- Stephenson, Randell, et al.
(författare)
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Late Cretaceous-Cenozoic basin inversion and palaeostress fields in the North Atlantic-western Alpine-Tethys realm : Implications for intraplate tectonics
- 2020
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Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 210
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Forskningsöversikt (refereegranskat)abstract
- Intraplate basin/structural inversion (indicating tectonic shortening) is a good marker of ("far-field") tectonic stress regime changes that are linked to plate geometries and interactions, a premise that is qualitatively well-established in the literature. There is also quantitative evidence that Late Cretaceous-Palaeocene inversion of sedimentary basins in north-central Europe was explicitly driven by an intraplate, relaxational response to forces developed during rapid reconfigurations of the Alpine-Tethys (Europe-Africa) convergent plate boundary. Although with a degree of temporal ambiguity, three main periods of intraplate tectonics (marked primarily by structural inversion in initially extensional sedimentary basins) are indicated in the North Atlantic-western Alpine-Tethys realm. These are in the Late Cretaceous-Palaeocene, the Eocene-Oligocene and the Miocene. Examples recording these periods are primarily interpreted seismic reflection profiles (of varying quality and resolution) from the published literature. Additional examples where seismic data are not present, but timing constraints are robust from other observations, have also been considered. The schematic distribution and orientation of the literature-compiled intraplate inversion structures are compared to the model palaeostress fields derived from Late Cretaceous-Palaeocene, Eocene-Oligocene and Miocene tectonic reconstructions of the North Atlantic-western Alpine-Tethys realm. The modelled palaeostress fields include geopotential effects from palaeobathymetry and palaeotopography of the Earths surface as well as laterally variable lithosphere and crustal palaeo-thicknesses but do not include any component of the stress field produced by processes occurring at contiguous convergent plate margins. The former satisfactorily provides the background stress field of most of the Earth's plate interiors and it is inferred that the latter is paramount in producing "stress trauma" in the interior of plates resulting in permanent intraplate deformation such as basin inversion.
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| 7. |
- Olivetti, Leonardo, et al.
(författare)
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Advances and prospects of deep learning for medium-range extreme weather forecasting
- 2024
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Ingår i: Geoscientific Model Development. - : Copernicus Publications. - 1991-959X .- 1991-9603. ; 17:6, s. 2347-2358
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Forskningsöversikt (refereegranskat)abstract
- In recent years, deep learning models have rapidly emerged as a stand-alone alternative to physics-based numerical models for medium-range weather forecasting. Several independent research groups claim to have developed deep learning weather forecasts that outperform those from state-of-the-art physics-based models, and operational implementation of data-driven forecasts appears to be drawing near. However, questions remain about the capabilities of deep learning models with respect to providing robust forecasts of extreme weather. This paper provides an overview of recent developments in the field of deep learning weather forecasts and scrutinises the challenges that extreme weather events pose to leading deep learning models. Lastly, it argues for the need to tailor data-driven models to forecast extreme events and proposes a foundational workflow to develop such models.
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| 8. |
- Rosero, Viviana, et al.
(författare)
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The SOMA Radio Survey. I. Comprehensive SEDs of High-mass Protostars from Infrared to Radio and the Emergence of Ionization Feedback
- 2019
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 873:1
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Forskningsöversikt (refereegranskat)abstract
- We study centimeter continuum emission of eight high- and intermediate-mass protostars that are part of the SOFIA Massive Star Formation Survey, thus building extended spectral energy distributions (SEDs) from the radio to the infrared. We discuss the morphology seen in the centimeter continuum images, which are mostly derived from archival Very Large Array data, and the relation to infrared morphology. We use the SEDs to test new models of high-mass star formation including radiative and disk-wind feedback and associated free-free and dust continuum emission. We show that interferometric data of the centimeter continuum flux densities provide additional, stringent tests of the models by constraining the ionizing luminosity of the source; they also help to break degeneracies encountered when modeling the infrared-only SEDs, especially for the protostellar mass. Our derived parameters are consistent with physical parameters estimated by other methods, such as dynamical protostellar masses. We find a few examples of additional stellar sources in the vicinity of the high-mass protostars, which may be low-mass young stellar objects. However, the stellar multiplicity of the regions, at least as traced by radio continuum emission, appears to be relatively low.
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| 9. |
- Rashidi, Amin, et al.
(författare)
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A Review of Tsunami Hazards in the Makran Subduction Zone
- 2020
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Ingår i: Geosciences. - : MDPI AG. - 2076-3263. ; 10:9
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Forskningsöversikt (refereegranskat)abstract
- The uncertain tsunamigenic potential of the Makran Subduction Zone (MSZ) has made it an interesting natural laboratory for tsunami-related studies. This study aims to review the recent activities on tsunami hazard in the Makran subduction zone with a focus on deterministic and probabilistic tsunami hazard assessments. While almost all studies focused on tsunami hazard from the Makran subduction thrust, other local sources such as splay faults and landslides can be also real threats in the future. Far-field tsunami sources such as Sumatra-Andaman and Java subduction zones, commonly lumped as the Sunda subduction zone, do not seem to pose a serious risk to the Makran coastlines. The tsunamigenic potential of the western segment of the MSZ should not be underestimated considering the new evidence from geological studies and lessons from past tsunamis in the world. An overview of the results of tsunami hazard studies shows that the coastal area between Kereti to Ormara along the shoreline of Iran-Pakistan and the coastal segment between Muscat and Sur along Oman's shoreline are the most hazardous areas. Uncertainties in studying tsunami hazard for the Makran region are large. We recommend that future studies mainly focus on the role of thick sediments, a better understanding of the plates interface geometry, the source mechanism and history of extreme-wave deposits, the contribution of other local tsunamigenic sources and vulnerability assessment for all coastlines of the whole Makran region.
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| 10. |
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