A palaeoecological test of the land-use hypothesis for recent lake acidification in South-West Norway using hill-top lakes     

H. J. B. Birks  Frode Berge  J. F. Boyle  B. F. Cumming 《Journal of Paleolimnology》1990,4(1):69-85

Lakes perched on hill-tops have very small catchments. Their water chemistry is largely influenced by the chemical composition of precipitation and by the underlying bedrock geology. They are ideal sites for testing the hypothesis that land-use and associated soil changes are a major cause of recent lake acidification. On this hypothesis, hill-top lakes in SW Norway are predicted not to show any recent lake acidification because, by their very nature, the chemistry of such lakes is little influenced by land-use or soil changes.Palaeolimnological analyses of diatoms and chrysophytes show that prior to ca. 1914 the two hill-top lakes investigated were naturally acid with reconstructed lake-pH values of at least 4.8–5.1. Since ca. 1914 lake pH values declined to ca. 4.5–4.7. These results contradict the land-use hypothesis. All the available palaeolimnological evidence (diatoms, chrysophytes, pollen, sediment geochemistry, carbonaceous particles) is consistent with the acid-deposition hypothesis.In the absence of any evidence to support the land-use hypothesis as a primary cause of recent lake acidification and in the light of several independent refutations, it is perhaps time to put the land-use hypothesis for recent lake acidification to rest.  相似文献   

Periodic long-term X-ray and radio variability of Cygnus X-1     

Pawe&#; Lachowicz  rzej A. Zdziarski  Alex Schwarzenberg-Czerny  Guy G. Pooley  Shunji Kitamoto 《Monthly notices of the Royal Astronomical Society》2006,368(3):1025-1039

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Book review     

Alex Woronow 《Mathematical Geology》1987,19(6):579-581

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VOCs in Ground Water Influenced by Large Scale Withdrawals   总被引：1，自引：0，他引：1  

Alex J. Fischer  Elizabeth A. Rowan  Roy F. Spalding 《Ground water》1987,25(4):407-414

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Woodleigh impact structure,Australia: Shock petrography and geochemical studies     

Wolf Uwe REIMOLD  Christian KOEBERL  Robert M. HOUGH  Iain MCDONALD  Alex BEVAN  Kassa AMARE  Bevan M. FRENCH 《Meteoritics & planetary science》2003,38(7):1109-1130

Abstract— The large, complex Woodleigh structure in the Carnarvon basin of Western Australia has recently been added to the terrestrial impact crater record. Many aspects of this structure are, however, still uncertain. This work provides a detailed petrographic assessment of a suite of representative drill core samples from the borehole Woodleigh 1 that penetrated uplifted basement rocks of the central part of this structure. Fundamental rock and mineral deformation data and high‐precision chemical data, including results of PGE and oxygen isotopic analysis, are presented. The sampled interval displays likely impact‐produced macrodeformation in the form of fracturing and breccia veining at the microscopic scale. Contrary to earlier reports that these breccias represent pseudotachylite (friction melt) or even shock/shear‐produced pseudotachylitic melt breccia cannot be confirmed due to pervasive post‐impact alteration. Abundant planar deformation features (PDFs) in quartz, in addition to diaplectic glass and partial isotropization, are the main shock deformation effects observed, confirming that Woodleigh is of impact origin. Over the investigated depth interval, the statistics of quartz grains with a variable number of sets of PDFs does not change significantly, and the patterns of crystallographic orientations of PDFs in randomly selected quartz grains does not indicate a change in absolute shock pressure with depth either. The value of oxygen isotopes for the recognition of meteoritic contamination, as proposed by earlier Woodleigh workers, is critically assessed. Neither INA nor PGE analyses of our samples support the presence of a meteoritic component within this basement section, as had been claimed in earlier work.  相似文献   

Climate change, adaptation and economic growth     

Alex Bowen  Sarah Cochrane  Samuel Fankhauser 《Climatic change》2012,113(2):95-106

This paper explores the links between economic growth and the impacts of climate change. Inclusive, pro-poor growth is central to the development of low-income countries. There is also a broad consensus that growth and development are important to reduce vulnerability to climate change. Growth does not automatically reduce vulnerability, only the right kind of growth does. The paper aims to develop a better understanding of what the ??right kind of growth?? may be. We find that many growth policies, such as investment in skills and access to finance, indeed reduce vulnerability to climate change. However, climate change calls for some adjustments in growth policy. In particular, investment in infrastructure and efforts to stimulate entrepreneurship and competitive markets must take more of a risk management perspective and recognise climate risks.  相似文献   

Why does the Antarctic Peninsula Warm in climate simulations?     

Xin Qu  Alex Hall  Julien Boé 《Climate Dynamics》2012,38(5-6):913-927

The Antarctic Peninsula has warmed significantly since the 1950s. This pronounced and isolated warming trend is collectively captured by 29 twentieth-century climate hindcasts participating in the version 3 Coupled Model Intercomparison Project. To understand the factors driving warming trends in the hindcasts, we examine trends in Peninsula region’s atmospheric heat budget in every simulation. We find that atmospheric latent heat release increases in nearly all hindcasts. These increases are generally anthropogenic in origin, and account for about 60% of the ensemble-mean warming trend in the Peninsula. They are driven primarily by well-understood features of the anthropogenic intensification of global hydrological cycle. As sea surface temperature increases, moisture contained in atmospheric flows increases. When such flows are forced to ascend the Peninsula’s topography, enhanced local latent heat release results. The mechanism driving the warming of the Antarctic Peninsula is therefore clear in the models. Evidence for a similar mechanism operating in the real world is seen in the increasing snow accumulation rates inferred from ice cores drilled in the Peninsula. However, the relative importance of this mechanism and other processes previously identified as potentially causing the observed warming, such as the recent sea ice retreat in the Bellingshausen Sea, is difficult to assess. Thus the relevance of the simulated warming mechanism to the observed warming is unclear, in spite of its robustness in the models.  相似文献   

Sources of spread in simulations of Arctic sea ice loss over the twenty-first century     

Julien Boé  Alex Hall  Xin Qu 《Climatic change》2010,99(3-4):637-645

We show that intermodel variations in the anthropogenically-forced evolution of September sea ice extent (SSIE) in the Arctic stem mainly from two factors: the baseline climatological sea ice thickness (SIT) distribution, and the local climate feedback parameter. The roles of these two factors evolve over the course of the twenty-first century. The SIT distribution is the most important factor in current trends and those of coming decades, accounting for roughly half the intermodel variations in SSIE trends. Then, its role progressively decreases, so that around the middle of the twenty-first century the local climate feedback parameter becomes the dominant factor. Through this analysis, we identify the investments in improved simulation of Arctic climate necessary to reduce uncertainties both in projections of sea ice loss over the coming decades and in the ultimate fate of the ice pack.  相似文献   

Rural household demographics, livelihoods and the environment   总被引：8，自引：0，他引：8  

Alex de Sherbinin  Leah K. VanWey  Kendra McSweeney  Rimjhim Aggarwal  Alisson Barbieri  Sabine Henry  Lori M. Hunter  Wayne Twine  Robert Walker 《Global Environmental Change》2008,18(1):38-53

This paper reviews and synthesizes findings from scholarly work on linkages among rural household demographics, livelihoods and the environment. Using the livelihood approach as an organizing framework, we examine evidence on the multiple pathways linking environmental variables and the following demographic variables: fertility, migration, morbidity and mortality, and lifecycles. Although the review draws on studies from the entire developing world, we find the majority of microlevel studies have been conducted in either marginal (mountainous or arid) or frontier environments, especially Amazonia. Though the linkages are mediated by many complex and often context-specific factors, there is strong evidence that dependence on natural resources intensifies when households lose human and social capital through adult morbidity and mortality, and qualified evidence for the influence of environmental factors on household decision-making regarding fertility and migration. Two decades of research on lifecycles and land cover change at the farm level have yielded a number of insights about how households make use of different land-use and natural resource management strategies at different stages. A thread running throughout the review is the importance of managing risk through livelihood diversification, ensuring future income security, and culture-specific norms regarding appropriate and desirable activities and demographic responses. Recommendations for future research are provided.  相似文献   

蒙特卡罗不确定性分析在O3模拟中的初步应用     

唐晓  王自发  朱江  吴其重  GBAGUIDI Alex 《气候与环境研究》2010,15(5):541-550

利用蒙特卡罗不确定性分析方法,分析了嵌套网格空气质量模式系统(NAQPMS/IAP)中154个模式输入变量不确定性对臭氧模拟的影响,量化了模式在北京奥运会期间臭氧模拟的不确定性,并确定出了主要不确定性因子。结果表明:(1)在奥运会期间(2008年8月8日～2008年8月24日),北京城区臭氧模拟的平均不确定性为19ppb,不确定性存在明显的日变化特征,白天不确定性大,夜间不确定性小。(2)在白天,北京城区近地层臭氧模拟最重要的不确定性来源是局地前体物排放,其次是NO2光解系数、风向、北京周边前体物排放和垂直扩散系数。另外,地面约150m以上,对臭氧模拟影响最大的不确定性因子是风向和北京周边前体物排放;夜间,北京城区近地层臭氧模拟的最大不确定性来源是局地NOx排放和垂直扩散系数。  相似文献