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881.
Many tools that are helpful for evaluating emissions mitigation measures, such as carbon abatement cost curves, focus exclusively on cost and emissions reduction potential without quantifying the direct and indirect impacts on stakeholders. The impacts of climate change will be the most severe and immediate for billions of poor people, especially for those whose livelihoods are based on agriculture and subsistence activities and are directly dependent on weather patterns. Thus, equity and vulnerability considerations must be central to GHG emissions reduction strategies. A case study of a carbon abatement cost curve for an electricity system in two Nicaraguan rural villages is presented and is complemented with assessments based on the poverty metrics of the poverty headcount, the Gini coefficient, and the Kuznets ratios. Although these metrics are relatively easy to calculate, the study provides a general indication as to how the social impacts of mitigation strategies on the poor (whether they are in rural or urban environments, developed or developing countries) can be revealed and highlights the inequalities that are embedded in them. Further work analysing how mitigation measures affect the various more detailed poverty indices, such as the Human Development, Gender Equality, or Multidimensional Poverty indices, is needed.  相似文献   
882.
A prominent weakening in equatorial Atlantic sea surface temperature (SST) variability, occurring around the year 2000, is investigated by means of observations, reanalysis products and the linear recharge oscillator (ReOsc) model. Compared to the time period 1982–1999, during 2000–2017 the May–June–July SST variability in the eastern equatorial Atlantic has decreased by more than 30%. Coupled air–sea feedbacks, namely the positive Bjerknes feedback and the negative net heat flux damping are important drivers for the equatorial Atlantic interannual SST variability. We find that the Bjerknes feedback weakened after 2000 while the net heat flux damping increased. The weakening of the Bjerknes feedback does not appear to be fully explainable by changes in the mean state of the tropical Atlantic. The increased net heat flux damping is related to an enhanced response of the latent heat flux to the SST anomalies (SSTa). Strengthened trade winds as well as warmer SSTs are suggested to increase the air–sea specific humidity difference and hence, enhancing the latent heat flux response to SSTa. A combined effect of those two processes is proposed to be responsible for the weakened SST variability in the eastern equatorial Atlantic. The ReOsc model supports the link between reduced SST variability, weaker Bjerknes feedback and stronger net heat flux damping.  相似文献   
883.
This study aims to evaluate soil climate quantitatively under present and projected climatic conditions across Central Europe (12.1°–18.9° E and 46.8°–51.1° N) and the U.S. Central Plains (90°–104° W and 37°–49° N), with a special focus on soil temperature, hydric regime, drought risk and potential productivity (assessed as a period suitable for crop growth). The analysis was completed for the baselines (1961–1990 for Europe and 1985–2005 for the U.S.) and time horizons of 2025, 2050 and 2100 based on the outputs of three global circulation models using two levels of climate sensitivity. The results indicate that the soil climate (soil temperature and hydric soil regimes) will change dramatically in both regions, with significant consequences for soil genesis. However, the predicted changes of the pathways are very uncertain because of the range of future climate systems predicted by climate models. Nevertheless, our findings suggest that the risk of unfavourable dry years will increase, resulting in greater risk of soil erosion and lower productivity. The projected increase in the variability of dry and wet events combined with the uncertainty (particularly in the U.S.) poses a challenge for selecting the most appropriate adaptation strategies and for setting adequate policies. The results also suggest that the soil resources are likely be under increased pressure from changes in climate.  相似文献   
884.
El'gygytgyn (Chukotka, Arctic Russia) is a well‐preserved impact structure, mostly excavated in siliceous volcanic rocks. For this reason, the El'gygytgyn structure has been investigated in recent years and drilled in 2009 in the framework of an ICDP (International Continental Scientific Drilling Program) project. The target rocks mostly consist of rhyodacitic ignimbrites and tuffs, which make it difficult to distinguish impact melt clasts from fragments of unshocked target rock within the impact breccia. Several chemical and petrologic attempts, other than dating individual clasts, have been considered to distinguish impact melt from unshocked volcanic rock of the targets, but none has proven reliable. Here, we propose to use cathodoluminescence (imaging and spectrometry), whose intensity is inversely correlated with the degree of shock metamorphism experienced by the investigated lithology, to aid in such a distinction. Specifically, impact melt rocks display low cathodoluminescence intensity, whereas unshocked volcanic rocks from the area typically show high luminescence. This high luminescence decreases with the degree of shock experienced by the individual clasts in the impact breccia, down to almost undetectable when the groundmass is completely molten. This might apply only to El'gygytgyn, because the luminescence in volcanic rocks might be due to devitrification and recrystallization processes of the relatively old (Cretaceous) target rock with respect to the young impactites (3.58 Ma). The alteration that affects most samples from the drill core does not have a significant effect on the cathodoluminescence response. In conclusion, cathodoluminescence imaging and spectra, supported by Raman spectroscopy, potentially provide a useful tool for in situ characterization of siliceous impactites formed in volcanic target.  相似文献   
885.
886.
The complex impact structure El'gygytgyn (age 3.6 Ma, diameter 18 km) in northeastern Russia was formed in ~88 Ma old volcanic target rocks of the Ochotsk‐Chukotsky Volcanic Belt (OCVB). In 2009, El'gygytgyn was the target of a drilling project of the International Continental Scientific Drilling Program (ICDP), and in summer 2011 it was investigated further by a Russian–German expedition. Drill core material and surface samples, including volcanic target rocks and impactites, have been investigated by various geochemical techniques in order to improve the record of trace element characteristics for these lithologies and to attempt to detect and constrain a possible meteoritic component. The bedrock units of the ICDP drill core reflect the felsic volcanics that are predominant in the crater vicinity. The overlying suevites comprise a mixture of all currently known target lithologies, dominated by felsic rocks but lacking a discernable meteoritic component based on platinum group element abundances. The reworked suevite, directly overlain by lake sediments, is not only comparatively enriched in shocked minerals and impact glass spherules, but also contains the highest concentrations of Os, Ir, Ru, and Rh compared to other El'gygytgyn impactites. This is—to a lesser extent—the result of admixture of a mafic component, but more likely the signature of a chondritic meteoritic component. However, the highly siderophile element contribution from target material akin to the mafic blocks of the ICDP drill core to the impactites remains poorly constrained.  相似文献   
887.
Remarkable bedding features occur in Middle Cambrian platy limestone of the Western Hills close to Beijing in NE-China, which are intercalated in a sequence of shallow water carbonates (mudstones, storm deposits, oolitic grainstones). The platy limestone beds (up to 5 cm thickness) have undergone complex diagenetic compaction and pressure solution. Varying facies types are characterized by wavy, stylolitic boundaries with different thickness of clay accumulation and common lateral pinch out. Cross-cutting relationships of stylolites commonly destroy primary bed-surfaces. This indicates an intimate interfingering resulting in an indenting fabric of primary separated facies types. Nevertheless, primary sedimentary boundaries can be recognized. There occur varying types of compaction features documented by different stylolite types with varying amplitudes and thickness of clay-enrichments (parallel clay seams, stylolamination, stylo-nodular and stylo-brecciated structures with multi-grained seams). Bedded limestone of the type documented, generally belong to the limestone family of Plattenkalk, Lithographic Limestone or platy limestone, which can form in different environments. Consequently, using these names without detailed data on some specific parameters (e.g. thickness, surface morphology, composition of allochems, particle and crystal size) results in more confusion and hinders the comparison of Plattenkalk, Lithographic Limestone and platy limestone from different locations throughout the earth history. Therefore, a classification is proposed here which is based on macroscopic, microscopic, and sub-microscopic parameters. Plattenkalk and platy limestone are considered to form the two main groups. Plattenkalk beds are laterally consistent and have parallel, horizontal surfaces. Platy limestone can pinch out laterally and reveals irregular and inclined bed surfaces. Single beds in both can have different thickness, internal structure (e.g. micritic, microsparitic) and fabric (e.g. homogeneous, nodular), particle content and other variations (e.g. chemical, mineralogical). These parameters should be added to the basic name and used in a system similar to Folk’s limestone classification. Lithographic Limestone is defined as a subgroup of Plattenkalk with well-defined parameters. A consequent use of this classification will also help to understand fossil preservation and/or non-preservation in different types of Plattenkalk, Lithographic Limestone, and platy limestone.  相似文献   
888.
Understanding and interpretation of ‘numbers’ produced about the depositional age of an erratic boulder by cosmogenic nuclide surface-exposure dating is important in the construction of glacial chronology. We have sampled three ‘Findlinge’ (glacially transported boulders) located on the right-lateral margin of the Aare glacier at Möschberg, Grosshöchstetten, southeast of Bern, with the aim of shedding light on this topic. The boulders have the same depositional, but different post-depositional histories: simple exposure; exhumation; and human impact. This sampling is specially selected for this study, since the boulders showing exhumation and human impact would not have been sampled in a regular surface-exposure dating application. We measured cosmogenic 10Be concentrations and calculated apparent exposure ages that are 13.6 ± 0.5, 18.1 ± 0.8, and 7.5 ± 0.4 ka, respectively. The exposure age of the first boulder reflects exhumation. The apparent exposure age of 18.1 ± 0.8 ka (erosion-corrected exposure age 19.0 ± 0.9 ka) from the second boulder correlates well with the end of the Alpine and global last glacial maximum. The third boulder shows evidence of quarrying as it is surrounded by a rim of excavation material, which is also reflected by the 7.5 ± 0.4 ka apparent exposure age. We modeled the variation of 10Be concentrations with depth down into the sediment in which the first (exhumed) boulder was once buried in, and down into the third (quarried) boulder. According to our modeling, we determined that the exhumed ‘Findling’ was buried in sediment at a depth of around 0.5 m, and around 2 m of rock was quarried from the third ‘Findling’. Our results reveal the importance of sampling for surface-exposure dating within a well defined field context, as post-depositional impacts can easily hinder exposure-dating of surfaces.  相似文献   
889.
The settlement and development of Québec’s maritime coastline has generally taken place without consideration for coastal dynamics and coastal hazards. Consequently, fighting coastal erosion has become a necessity. Until now, the construction of rigid walls and encroachments has been the preferred approach to the problem. In the Chaleur Bay region, coastal communities are particularly vulnerable to erosion and flooding because a number of residential, commercial and transportation infrastructures have been installed on beach terraces and sand spits. Recent storms, such as the storm of December 2, 2005, have made possible a better understanding of how these rigid defence structures amplify the effects of storm surges and waves. These structures drive the sand away from the coast, lowering beach levels and even causing beaches to vanish entirely from the areas situated in front of the defence structures. The end result is a weakening of the natural capacity of these coastal systems to absorb the energy of waves and a greater risk of coastal flooding. An integrated approach using local knowledge on the one hand, along with LIDAR surveys and a DGPS system on the other hand, have made possible to map the levels reached by flooding at the time of the storm. The results indicate that such levels vary greatly in spatial terms and that the difference between the levels actually reached and the water level measured by tide gauge can be as much as 2 m; a difference that is due to anthropogenic perturbations. This raises questions concerning the safety and the reference levels used for mapping coastal flooding risk. Taking into account knowledge of local communities, analysis of water levels, geomorphological indicators and aggravating anthropogenic factors, an approach and basic criteria are put forward with a view of establishing a reference level for the mapping of flood risk that can be used by community land-use planners.  相似文献   
890.
This paper presents two novel nonlinear models of u-shaped anti-roll tanks for ships, and their linearizations. In addition, a third simplified nonlinear model is presented. The models are derived using Lagrangian mechanics. This formulation not only simplifies the modeling process, but also allows one to obtain models that satisfy energy-related physical properties. The proposed nonlinear models and their linearizations are validated using model-scale experimental data. Unlike other models in the literature, the nonlinear models in this paper are valid for large roll amplitudes. Even at moderate roll angles, the nonlinear models have three orders of magnitude lower mean square error relative to experimental data than the linear models.  相似文献   
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