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41.
42.
The “overshoot scenario” is an emissions scenario in which CO2 concentration in the atmosphere temporarily exceeds some pre-defined, “dangerous” threshold (before being reduced to non-dangerous levels). Support for this idea comes from its potential to achieve a balance between the burdens of current and future generations in dealing with global warming. Before it can be considered a viable policy, the overshoot scenario needs to be examined in terms of its impacts on the global climate and the environment. In, particular, it must be determined if climate change cause by the overshoot scenario is reversible or not, since crossing that “dangerous” CO2 threshold could result in climate change from which we might not be able to recover. In this study, we quantify the change in several climatic and environmental variables under the overshoot scenario using a global climate model of intermediate complexity. Compared to earlier studies on the overshoot scenario, we have an explicit carbon cycle model that allows us to represent carbon-climate feedbacks and force the climate model more realistically with CO2 emissions rates rather than with prescribed atmospheric pCO2. Our standard CO2 emissions rate is calculated on the basis of historical atmospheric pCO2 data and the WRE S650 non-overshoot stabilization profile. It starts from the preindustrial year 1760, peaks in the year 2056, and ends in the year 2300. A variety of overshoot scenarios were constructed by increasing the amplitude of the control emissions peak but decreasing the peak duration so that the cumulative emissions remain essentially constant. Sensitivity simulations of various overshoot scenarios in our model show that many aspects of the global climate are largely reversible by year 2300. The significance of the reversibility, which takes roughly 200 years in our experiments, depends on the time horizon with which it is viewed or the number of future generations for whom equity is sought. At times when the overshoot scenario has emissions rates higher then the control scenario, the transient changes in atmospheric and oceanic temperatures and surface ocean pH can be significant, even for moderate overshoot scenarios that remain within IPCC SRES emissions scenarios. The large transient changes and the centennial timescale of climate reversibility suggest that the overshoot might not be the best mitigation approach, even if it technically follows the optimal economic path. 相似文献
43.
A Palaeoaplysina reef occurs in the Gzhelian-Asselian interval of the Panthalassan atoll carbonates, Akiyoshi Terrane, SW Japan. An alga, Palaeoaplysina was paleogeographically distributed mainly along the northern margin of Pangea and is regarded as a boreal element. Its distribution extended to the tropical or subtropical area of the Panthalassa Ocean caused by global cooling during an icehouse period. The Palaeoaplysina community was succeeded by a calcisponge community in the late Early Permian. This biotic turnover almost corresponds to the climatic change from icehouse to greenhouse conditions and coincides with the timing of a superplume activity in the mid-Panthalassa Ocean. 相似文献
44.
Simplified design methods for obtaining the maximum strain in pipelines crossing active faults proposed by Newmark, Kennedy and Wang have not considered the section deformation of the pipe. In this study, a new simplified method is developed for obtaining the maximum strain in steel pipes crossing faults considering non‐linearity of material and geometry of pipe section. It is assumed that the pipe will bend near the fault and the geometry of pipe in the longitudinal direction will change according to a bent deformation. On the other hand, the relation between maximum strain and bent angle has been obtained using a beam–shell hybrid FEM for different pipe‐fault conditions. The developed method can be used for calculating the maximum strains for fault‐crossing steel pipes with different angles of crossing both in tension and compression, by considering the deformation of the pipe cross‐section. Copyright © 2001 John Wiley Sons, Ltd. 相似文献
45.
Horizontal earth's strains preceding the Kanto, Japan, earthquake of 1, September 1923, are deduced from the analysis of the old triangulation data. The anomalous strains that are several times larger than usual tectonic strain are found in the western part of Tokyo Bay, Sagamihara district, Japan for the observational period 1882/91–1898/1910, while any significant strain is not revealed in the other region of the Kanto district. The Kanto district was surveyed twice during the period 1883/85–1890/92 in the west and during the period 1890/92–1897/99 in the east respectively. The polarity of the detected anomalous strains, the directions and the signs of the principal strains, are quite the same as those of the postseismic crustal strains during the period 1924–74, and are reversed as compared to the coseismic one.The Philippine Sea plate thrusts under the South Kanto district with N25°W direction and pulls down the land during the interseismic period. The aseismic reverse faulting would begin several decades before the 1923 Kanto earthquake along the deep interface between the Asian plate and the convergent Philippine Sea plate. The down-going along the locked part of the interface would be accelerated, thus the compressional stress on the earth's surface might be concentrated over the deep fault plane together with the acceleration of the subsidence at the tip of the peninsula close to the Sagami trough. 相似文献
46.
Abstract Fusulinoidean faunal succession from Paleo–Tethyan seamount-type carbonates of the Yutangzhai section in the Central zone of the Changning–Menglian Belt of West Yunnan, Southwest China, is presented for the first time. The Changning–Menglian Belt is one of the orogenic belts that represent the closed main Paleo–Tethys in East Asia. The Yutangzhai section is represented by basalts and overlying carbonates, about 1100 m thick. It exhibits a continuous faunal succession composed of 17 fusulinoidean assemblages ranging from the Serpukhovian (late Mississippian/late Early Carboniferous) to Midian/Capitanian (late Middle Permian/late Guadalupian). No significant faunal break can be recognized in this section. The generic and some specific composition of the Yutangzhai assemblages indicates that the faunal succession is similar to those observed in Tethyan and Panthalassan areas and is of tropical Tethyan type although their generic diversity is definitely lower than those of Paleo–Tethyan shelves, such as South China, Indochina, and Central Asia. Throughout the Yutangzhai section, the carbonate rocks are essentially massive, very pure in composition, and devoid of terrigenous siliciclastic inputs. These lithologic characters are identical to those observed in accreted shallow-marine carbonate successions of seamount origin in Permian and Jurassic accretionary complexes of Japan, for example the Akiyoshi Limestone. This evidence further demonstrates the seamount origin of the basalt–limestone succession in the Central zone of the Changning–Menglian Belt from the viewpoint of lithofacies. In middle Mississippian (middle Early Carboniferous) time, oceanic submarine volcanism that was probably related to hot spot activities formed a number of seamounts and oceanic plateaus. It was active not only in the Panthalassa, but also in the Paleo–Tethys. 相似文献
47.
Abstract: Microorganisms found at terrestrial and seafloor hydrothermal systems are classified based on their optimum growth temperatures. Prokaryotes exhibiting optimum growth temperatures above 45C are defined as thermophiles, while those with optimum growth temperatures above 80C are called hyperthermophiles. Hyperthermophiles have chemically and thermodynamically stable cytoplasmic‐membrane consisting of ether–lipids. Hyperthermophiles observed at temperature up to 113C in seafloor hydrothermal areas should have thermostable proteins. Presumably, the thermostable proteins are replacing certain amino acid residue by proline instead of alanine in order to increase hydrogen bonds and salt bridges. Microorganisms inhabiting terrestrial and seafloor hydrothermal areas obtain energy mainly by use of chemical disequilibrium, so that their habitat may be restricted to the redox boundary between ambient water and reduced hydrothermal fluids. Among more than 200 species of cultivable thermophiles and hyperthermophiles, hyperthermophiles mainly obtain energy by sulfur reduction, because this reaction can produce energy efficiently at > 80C. Some hyperthermophilic sulfur reducers can reduce Cr(VI), Mn(IV), Fe(III), Co(III), As(V), Se(VI), Tc(VII), Au(III) and U(VI) through hydrogen or organic compounds that act as reducing agents for yielding energy. Some hyperther‐mophiles use W instead of Mo for activating their enzymes. Bacteria can pump out toxic metal ions from their cells, however toxic metal resistance systems of archaea, including hyperthermophiles, have not yet been studied. Methane producing hyperthermophiles can yield energy by the autotrophic reaction, when sufficient carbon dioxide and molecular hydrogen can be supplied and methane can be removed from hydrothermal systems. If nitrogen can be supplied into a hydrothermal system, hydrogen oxidization by nitrogen species (e.g. NO3‐, NO2‐, NO and N2O) may be expected through the metabolism of some hyperthermophiles. 相似文献
48.
Ken-ichiro Hisada Masaaki Sugiyama Katsumi Ueno Punya Charusiri Shoji Arai 《Island Arc》2004,13(1):119-127
Abstract Thailand comprises two continental blocks: Sibumasu and Indochina. The clastic rocks of the Triassic Mae Sariang Group are distributed in the Mae Hong Son–Mae Sariang area, north‐west Thailand, which corresponds to the central part of Sibumasu. The clastic rocks yield abundant detrital chromian spinels, indicating a source of ultramafic/mafic rocks. The chemistry of the detrital chromian spinels suggests that they were derived from three different rock types: ocean‐floor peridotite, chromitite and intraplate basalt, and that ophiolitic rocks were exposed in the area, where there are no outcrops of them at present. Exposition of an ophiolitic complex denotes a suture zone or other tectonic boundary. The discovery of chromian spinels suggests that the Gondwana–Tethys divide is located along the Mae Yuam Fault zone. Both paleontological and tectonic aspects support this conclusion. 相似文献
49.
Jun-Ichi Matsuda Kenji Notsu Jun Okano Katsumi Yaskawa Leonard Chungue 《Tectonophysics》1984,104(1-2)
Sr isotopes and K-Ar ages were determined for volcanic rocks from three islands, Samoa, Rarotonga and Rurutu in the Austral-Gilbert-Marshall chain. We have established that Rurutu originated from the same “hot spot” as Tubuai and Raivavae in the Cook-Austral chain as indicated by its 11 m.y. K-Ar age and (
) ratios. The (
) ratios for Rurutu, Tubuai and Raivavae lie in the restricted range 0.7026–0.7035. K-Ar ages of all volcanic rocks from Samoa and Rarotonga are all less than 4 m.y. and their (
) ratios are much higher than those in Rurutu, Tubuai and Raivavae. These findings suggest that Samoa and Rarotonga did not originate in a single hot spot for the Cook-Austral islands. 相似文献
50.