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Fenglin WANG Xumei MAO Cunfu LIU 《中国地球化学学报》2006,25(B08):280-281
One kind of climatic proxies only can describes the comparative change of temperature or rainfall, but dissolved noble gases in groundwater can be used to date groundwater, calculate temperature and rainfall, and this method can give the exact change value of three parameters in one time. Dissolved noble gases in groundwater has four sources, radioactivity-formed noble gases which are from radioactive decay of some radioactive elements in the aquifers, balance-dissolved noble gases from dissolved air in balance condition in the course of supplying, excess noble gases from excess air for groundwater-air mixing and water table changing during infiltrating, and outer-interfused noble gases from outer interfusing air in open conditions during runoff. Because the contents of radioagenic noble gases in groundwater are correlated to flowing time, such as He, the age of groundwater can be dated with 4He based on the solubility of He and the radioactive intensity of aquifers. The solubility of noble gases is the function of temperature. We can compare the contents of balance-dissolved noble gases in groundwater with the temperature-solubility experimental curves of noble gases, and calculate the forming temperature of groundwater. The contents of excess noble gases are related to the water column of infiltration which can reveal the volume of rainfall in a given period of time in general, and it may increase along with the pressure of aquifers when groundwater table rises greatly. So we can calculate the value of rainfall by comparing the contents of excess noble gases in groundwater samples with those in modem groundwater. Reconstruction of climatic change on a quantitative basis with the method of dissolved noble gases in Hebei plain （China） shows that the temperature changed from 3.8 to 19.7℃ in the past forty thousand years, it decreased to 3.8℃ in 16000 a B.P. but higher than 19.7℃ in 5060 a B.P. The rainfall was about 600mm during 40000 to 15000 a B.P., then decreased gradually to 410mm in 11000 a B.P., but subsequently increased to 950mm in 4400 a B.P. The change of noble gas temperature is consistent with 180 shift, and 6D varied with the change of other climatic proxy, such as rainfall. 相似文献
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《Gondwana Research》2014,25(3):1186-1201
The modern Koala Phascolarctos cinereus is the last surviving member of a once diverse family Phascolarctidae (Marsupialia, Phascolarctomorphia). Nine genera and at least 16 species of koala are known. Late Oligocene sediments of central Australia record the oldest fossils and highest species diversity. Five species are known from the early to middle Miocene rainforest assemblages of the Riversleigh World Heritage Area, Queensland. With the onset of dryer conditions after the middle Miocene climatic optimum (~ 16 Ma), rainforest habitats contracted resulting in the apparent extinction of three koala lineages (Litokoala, Nimiokoala, Priscakoala). Phascolarctos first appears in the fossil record during the Pliocene and the modern species around 350 ka. Despite a dramatic decline in taxonomic diversity to a single extant species, the fossil record indicates that at most only three koala species coexisted in any given faunal assemblage throughout their 24 million year history. Within these assemblages, the vast majority of extinct koalas are extremely rare (some known from only a single specimen) which may reflect a general rarity within their palaeohabitats compared with the modern species which is represented by an estimated 400,000 individuals spread over most of eastern mainland Australia. Be that as it may, P. cinereus, although once geographically more widespread, occurring for example in Western Australia in the Pleistocene, underwent significant range contractions and localized population extinctions during the stressful climatic conditions of the late Pleistocene and more recently through human-induced habitat destruction. Combined with threats of disease, reduced genetic diversity and climate change, the survival of this iconic Australian marsupial is arguably a cause for concern. 相似文献
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《Geoforum》2015
In the United States, contemporary anti-science education coalitions are increasingly linking climate change and evolution using “teach the controversy” campaigns. Awareness of this political phenomena raises questions about the extent to which portrayals of global warming predictions as mere knowledge claims undermine efforts to increase public understanding of scientific consensus about global warming. This paper uses a critical political ecology framework to explore the problematization of climate change consensus located and performed across discourses of secondary science teaching and learning. Theories of resistance are used to analyze teachers’ everyday experiences with classroom pushback about climate change. Data collection included key informant interviews with state science education stakeholders and on-line survey of 5th–12th grade science teachers in Oklahoma, USA. The article synthesizes the situated discourses of Oklahoma science teachers’ and their attitudes about teaching climate change in the face of public controversy. Our analysis demonstrates teachers marginalized by anti-science controversies but engaged in everyday acts of resistance to political, ideological, and religious norms. Most notably, science teachers re-purpose “teach the controversy” frames as a way to introduce climate change where it might not otherwise be included. We argue that, contextualized within a history of contestation over the teaching of evolution, the practice of teaching ‘both sides’ is an important boundary ordering device that bridges convinced and skeptical discourses in the classroom. This research informs new roles and possibilities for science education on global environmental change by reminding climate scientists, educators, and policy advocates that all climate change knowledge is coproduced. 相似文献
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Late cretaceous tectonic change of the eastern margin of the Tibetan Plateau — results from multisystem thermochronology 总被引：2，自引：0，他引：2
Bin Deng Shugen Liu Zhiwu Li Junxing Cao Wei Sun 《Journal of the Geological Society of India》2012,80(2):241-254
Partially due to lack of structural and sedimentary records to constrain the Jurassic-to-Cretaceous evolution, there was a
missing process here in the eastern margin of Tibetan Plateau as it changed from the Paleo-Tethyan to Neo-Tethyan regime.
Based on the analysis of 125 thermochronology ages (U/Pb, 40Ar/39A, 87Rb/86Sr, FT, U-Th/He) of igneous rocks from the eastern margin of Tibet, we propose a multisystem thermochronology approach to
restore the cooling and emplacement of granites and decipher the missing process. Our integrated study suggests that a key
Late Cretaceous (about 100Ma) tectonic change from the Paleo-Tethyan to Neo-Tethyan regime took place there. In the Late Triassic
period, the initial emplacement of granite in the Songpan-Ganzi Fold Belt (SGFB) was characterized by a decrease in emplacement
age and depth from west to east, and from north to south. Subsequently, all were followed by a very long period of slow cooling,
which was followed by a rapid emplacement of about 100Ma. The intensive granite emplacement took place all over except northeastern
SGFB, with a decrease in emplacement depth from west to east, which was linked with the far-field effect of Lhasa-Qiangtang
collision. After this episode, the cooling history of granite in SGFB had a rapid emplacement on the subsurface under the
control of the Neo-Tethyan regime. This process has control of the post Late Cretaceous regional magmatic activity and tectonics,
as well as the sedimentary response in Sichuan and Xichang basin. 相似文献
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The Denver Basin bedrock aquifer system is an important source of water for municipal and agricultural uses in the Denver and Colorado Springs metropolitan areas. The Denver area is one of the fastest growing areas in the United States with a population of 1.2 million in 1960 that has increased to over 2.4 million by 2000. This rapid population growth has produced a corresponding increase in demand for potable water. Historically, the Denver area has relied on surface water, however, in the past 10 years new housing and recreation developments have begun to rely on groundwater from the bedrock aquifers as the surface water is fully appropriated and in short supply.The Denver Basin bedrock aquifer system consists of Tertiary and Cretaceous age sedimentary rocks known as the Dawson, Denver, Arapahoe and Laramie-Fox Hills Aquifers. The number of bedrock wells has increased from 12,000 in 1985 to 33,700 in 2001 and the withdrawal of groundwater has caused water level declines of 76 m. Water level declines for the past 10 years have ranged from 3 to 12 m per year. The groundwater supplies were once thought to last 100 years but there is concern that the groundwater supplies may be essentially depleted in 10 to 15 years in areas on the west side of the basin.Extensive development of the aquifer system has occurred in the last 25 years especially near the center of the basin in Douglas and El Paso Counties where rapid urban growth continues and surface water is lacking. Groundwater is being mined from the aquifer system because the discharge by wells exceeds the rate of recharge. Concern is mounting that increased groundwater withdrawal will cause water level declines, increased costs to withdraw groundwater, reduced well yield, and reduced groundwater storage. As the long-term sustainability of the groundwater resource is in doubt, water managers believe that the life of the Denver Basin aquifers can be extended with artificial recharge, water reuse, restrictions on lawn watering, well permit restrictions and conservation measures. 相似文献
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This paper examines changes in gender relations in a small coastal community as a result of the 2010 Chile earthquake and tsunami. Vulnerability and resilience are used as a conceptual framework to analyse these changes. Based on empirical evidence from a seven-year longitudinal study and quasi-ethnographic work, we explore changes in power relations at the different stages of the disaster and longer-term recovery as well as the conditions that fostered these changes. Our findings show distinct patterns of change. First, disasters can trigger long-lasting changes that challenge historical patriarchal relations. Second, while vulnerability increases following a disaster, resilience can potentially counteract women’s vulnerability. We propose that resilience can be a pathway to produce long-term changes in gender relations and empower women in the context of disasters. 相似文献
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For our ancestors, oil seeps were both a fascination and a resource but as the planet's reserves of high quality low density oil becomes increasingly depleted, so there is now a renewed interest in heavier,biodegraded oils such as those encountered in terrestrial seeps. One such seep is Pitch Lake in the Caribbean island of Trinidad, which is the largest natural deposit of asphalt in the world. At the northern end of the Caribbean, oil emerges along a tectonic contact on the island on Cuba. The sources of the oils from these seeps are relatively recent and both are subject to intense weathering due to the tropical conditions. When analysed by gas chromatography(GC) both oils appear as unresolved complex mixtures(UCM) and show a very high degree of biodegradation thus presenting an analytical challenge. In this case study, these two Caribbean seep oils were analysed by comprehensive two dimensional GC with time of flight mass spectrometry(GC×GC-TOFMS) to expose many thousands of the individual compounds that comprise the UCM. The high chromatographic resolution of the GC×GC-TOFMS produced good quality mass spectra allowing many compounds including molecular fossil ‘biomarkers' to be identified. Compound classes included diamondoid hydrocarbons, demethylated hopanes and secohopanes, mono-and tri-aromatic steroids. D-ring aromatised structures of the 8,14-seco-hopanes,including demethylated forms were present in both oils but further demethylation, probably at position C-25 during biodegradation, was only observed in the Pitch Lake oil. Many polycyclic aromatic hydrocarbons(PAHs) were absent although the fungal-derived pentacyclic PAH perylene was present in both oils. The presence of the angiosperm biomarker lupane in the Pitch Lake oil constrained the age to the Late Cretaceous. The higher degree of biodegradation observed in the Cuban oil was likely due to relatively slow anaerobic processes whereas oil within Pitch Lake was probably subject to additional more rapid aerobic metabolism within the lake. 相似文献
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GeoJournal - Climate change is recognised among the drivers of conflicts in developing regions but the growing studies on climate change–violent conflict nexus in Africa have paid little... 相似文献
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《Comptes Rendus Geoscience》2018,350(7):347-353
After the well-reported record loss of Arctic stratospheric ozone of up to 38% in the winter 2010–2011, further large depletion of 27% occurred in the winter 2015–2016. Record low winter polar vortex temperatures, below the threshold for ice polar stratospheric cloud (PSC) formation, persisted for one month in January 2016. This is the first observation of such an event and resulted in unprecedented dehydration/denitrification of the polar vortex. Although chemistry–climate models (CCMs) generally predict further cooling of the lower stratosphere with the increasing atmospheric concentrations of greenhouse gases (GHGs), significant differences are found between model results indicating relatively large uncertainties in the predictions. The link between stratospheric temperature and ozone loss is well understood and the observed relationship is well captured by chemical transport models (CTMs). However, the strong dynamical variability in the Arctic means that large ozone depletion events like those of 2010–2011 and 2015–2016 may still occur until the concentrations of ozone-depleting substances return to their 1960 values. It is thus likely that the stratospheric ozone recovery, currently anticipated for the mid-2030s, might be significantly delayed. Most important in order to predict the future evolution of Arctic ozone and to reduce the uncertainty of the timing for its recovery is to ensure continuation of high-quality ground-based and satellite ozone observations with special focus on monitoring the annual ozone loss during the Arctic winter. 相似文献
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With rising public awareness of climate change, celebrities have become an increasingly important community of non nation-state ‘actors’ influencing discourse and action, thereby comprising an emergent climate science-policy-celebrity complex. Some feel that these amplified and prominent voices contribute to greater public understanding of climate change science, as well as potentially catalyze climate policy cooperation. However, critics posit that increased involvement from the entertainment industry has not served to influence substantive long-term advancements in these arenas; rather, it has instead reduced the politics of climate change to the domain of fashion and fad, devoid of political and public saliency. Through tracking media coverage in Australia, Canada, the United States, and United Kingdom, we map out the terrain of a ‘Politicized Celebrity System’ in attempts to cut through dualistic characterizations of celebrity involvement in politics. We develop a classification system of the various types of climate change celebrity activities, and situate movements in contemporary consumer- and spectacle-driven carbon-based society. Through these analyses, we place dynamic and contested interactions in a spatially and temporally-sensitive ‘Cultural Circuits of Climate Change Celebrities’ model. In so doing, first we explore how these newly ‘authorized’ speakers and ‘experts’ might open up spaces in the public sphere and the science/policy nexus through ‘celebritization’ effects. Second, we examine how the celebrity as the ‘heroic individual’ seeking ‘conspicuous redemption’ may focus climate change actions through individualist frames. Overall, this paper explores potential promises, pitfalls and contradictions of this increasingly entrenched set of ‘agents’ in the cultural politics of climate change. Thus, as a form of climate change action, we consider whether it is more effective to ‘plant’ celebrities instead of trees. 相似文献
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Junfang HUANG Ranghui WANG 《中国地球化学学报》2006,25(B08):163-164
The process of salinization has increased dramatically over the past several decades in the northwest arid zone of China. Soil salinization has been recognized as a major environmental problem for many years in the Tarim River Basin. It is the key issue of solving the soil salinization problem to study interaction between water and salt in arid zone, which will provide useful principle and methodology to its solution. Taking Tarim River and Bosten Lake for example, by systematically collecting the basic data of hydrogeology, meteorology, and social economy, we analyzed the interaction of water and salt of Tarim River and Bostan Lake in natural and artificial conditions in aspects of basins, oases, lakes and marshes. The results showed that： （1） Temperature and precipitation are both increasing gradually in the whole Tarim River Basin, the climate tends to be come warmer and wetter, but the water quality condition is not optimistic; （2） At the end of the 1950s, mineralization degree was less than 1.0 g/L from the upper reaches to the lower reaches of the Tarim River. At present, it is more than 3.0 g/L in Alaer Lake （the upper reaches of the Tarim River） except in July, August and October, during which it is less than 1.0 g/L. In Qiala （the lower reaches）, it is more than 1.0 g/L except in March, moreover, it is about 5.0 g/L in July and December. The eco-water conveyance project implementation has still not improved Tarim River＇s water quality condition; （3） Bostan Lake was a tiny salt-water lake in the late 1950s, but the water-soil development of the oasis has aggravated the salinization in recent thirty years. Since the West Pumping Station was brought into operation in 1982, the Bostan Lake which accumulated salt has begun to be desalted. We consider that climate may not be the key factor for salinization in this area. Instead, socio-economic factors relevant to human activities should be mainly responsible for such changes, as is confirmed by our further analysis. In order to improve present situation of water-soil salinization, water resources utilization and management should be strengthened, highly efficient and water-saving irrigating technology should be spread, 相似文献
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Jaeil Cho Yang-Won Lee Pat J.-F. Yeh Kyung-Soo Han Shinjiro Kanae 《Environmental Earth Sciences》2014,71(9):3935-3944
Arid regions in Asia are commonly characterized by rapidly growing populations with limited land resources and varying rainfall frequencies under climatic change. Despite being one of the most important environmental challenges in Asia, the changing aridity in this region, particularly due to large-scale land cover change, has not been well documented. In this study, we used rainfall data and a new land heterogeneity index to identify recent trend in land cover changes in the Asian arid regions. The result indicates a significant decreasing trend of barren lands and an increasing trend of vegetated lands. Although the potential land cover change is commonly believed to be strongly sensitive to rainfall change, such sensitivity has not been observed during the nine-year period (2001–2009) analyzed. Through the analyses of two separate periods (2001–2005 and 2005–2009), the sensitivity of rainfall to land cover change in arid regions is found to be dependent on the initial spatial heterogeneity of vegetated land cover. The approach used and the findings in this study represent an important step toward better understanding of large-scale land cover change in the Asian arid regions, and have the potential to predict future land cover change under various climate change scenarios. 相似文献
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《Journal of Structural Geology》2001,23(2-3):431-453
The Tertiary Falcón Basin in northwestern Venezuela has a privileged position in the geodynamic puzzle of northwestern South America, occurring in a region where several major plates (Caribbean, South America and Nazca) and minor lithospheric blocks (Maracaibo, Bonaire and Western Colombia) are interacting. A combination of good exposures due to aridity and a near-continuous sedimentary record in a now inverted basin helps to unravel the Neogene and Quaternary geodynamic evolution of this region. A neotectonic and microtectonic investigation of the Plio-Quaternary sedimentary rocks of the northern Falcón Basin reveals that this region is subject to a compressive to transpressive regime at present. This regime is characterized by a NNW–SSE oriented maximum horizontal stress, and a ENE–WSW trending intermediate (or minimum) horizontal stress, as is confirmed by focal mechanism solutions. This stress field is in agreement both with the NNE-directed extrusion of the Maracaibo and Bonaire blocks in Western Venezuela, where the Falcón Basin is located, and present-day transpression along the Caribbean-South America plate boundary zone. 相似文献
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Qiao Hu Zhenghong Tang Martha Shulski Natalie Umphlett Tarik Abdel-Monem Frank E. Uhlarik 《Natural Hazards》2018,90(2):777-801
Disasters continue to have a dramatic impact on lives, livelihoods and environments communities depend on. In response to these losses, the global community has developed various theories, assessment methodologies and policies aimed at reducing global losses. A contemporary outcome of these interventions is to build the disaster resilience. However, despite the disaster resilience-building endeavours espoused by policies, theories and methodologies, very little progress is being made in reducing disaster losses. This paper argues that a possible reason behind the limitations of current resilience-building policies and methodologies could be that most of these policies are based a mechanistic scientific paradigm that places an emphasis on system components that are perceived to build resilience and not the function of systems as a whole. This often leads to resilience-building initiatives that are based on a ‘one-size-fits-all’ approach. This paper argues for the use of a complex adaptive systems approach to building resilience. This approach argues that contextual factors within different social systems will have a nonlinear affect on disaster resilience-building efforts. Therefore, it is crucial to move away from ‘one-size-fits-all’ approaches to more flexible approaches to building resilience. These hypotheses are tested by means of a correlation statistical analysis of agricultural communities in Southern Africa. Results of this analysis indicate that unique resilience profiles are evident in almost all of the communities studied. This indicates that resilience is not the same for everybody, and that resilience-building endeavours should be flexible enough to be adapted for different contexts. 相似文献
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Mangrove forest stores large organic carbon stocks in a setting that is highly vulnerable to climate change and direct anthropogenic influences. As such there is a need to elucidate the causes and consequences of land use change on these ecosystems that have high value in terms of ecosystem services. We examine the areal pattern of land types in a coastal region located in southern Iran over a period of 14 years to predict future loss and gain in land types to the year 2025. We applied a CA–Markov model to simulate and predict mangrove forest change. Landsat satellite images from 2000 to 2014 were used to analyze the land cover changes between soil, open water and mangroves. Major changes during this period were observed in soil and water which could be attributed to rising sea level. Furthermore, the mangrove area in the more seaward position was converted to open water due to sea-level rise. A cellular automata model was then used to predict the land cover changes that would occur by the year 2025. Results demonstrated that approximately 21 ha of mangrove area will be converted to open water, while mangroves are projected to expand by approximately 28 ha in landward direction. These changes need to be delineated to better inform precise mitigation and adaptation measures. 相似文献
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The results derived from geological data show that the half-spreading rate between the African and South American plates has
remained relatively constant at 2 cm/year over the past 80 million years (Silver et al. in Science 279:60–63, 1998). In this paper, we have reestimated a new relative angular velocity of Africa–South America plates using the selected space
geodetic station data through a new method. Our angular velocity estimates the spreading rates of Africa–South America plate
over several years that are similar in azimuth but significantly slower in rate than the NUVEL-1A predictions averaged over
the past 3 million years. The implied rates of deceleration coincide with longer-term trends over the past 35 million years
and may reflect the effects of plate interaction and coupling of Africa–South America plates.
An erratum to this article can be found at 相似文献
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In recent years, climate and environment changes since the Little Ice Age have become a focus in modern research. The paper selected the sediment (77 cm) of Sihu Lake, which was located in Guilin, southern China, as the research object and analyzed the karst wetland environmental changes within nearly 450 years. According to the vertical profile of indicators and geochemical elements in sediment core, the regional environmental evolution was divided into four stages. The former two stages were mainly influenced by Little Ice Age (1562–1895). The third stage climate has changed slowly. The fourth stage was mainly affected by human activities and global warming. The factor analysis of geochemical elements indicated that karst wetland regional environmental change was affected by four major factors. In the 53–77 cm stage (1562–1703), F1 (erosion factor), F2 (watershed runoff and diagenesis factor) and F3 (regional background factor) were reduced, indicating that it was in cold and dry stage of Little Ice Age. In the 20–53 cm stage (1703–1895), F1 and F2 increased, indicating that it was in cold and wet stage of Little Ice Age. In the 4–20 cm stage (1895–1987), F1, F2 and F4 (human activity factor) increased slowly, indicating that the climate was affected by global warming and more precipitation. In the 0–4 cm stage (1987–2007), F1 and F2 reduced and F4 increased, indicating the reduced precipitation, rising temperature and more impact of human activities. In addition, it was proposed that the Little Ice Age in Guilin District in southern China started in the 1560s and lasted until the 1895s or so. 相似文献