853 resultados para The Asian monsoon
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High-resolution studies of a planktonic foraminifer core record from the South China Sea (SCS) (31KL: 18°45.4'N, 115°52.4'E, water depth 3360 m) reveal changes driven by ice-volume forcings in the climate of the East Asian monsoon in the western Pacific marginal sea during the late Quaternary. The analyses of planktonic foraminifer faunal abundance data from the core indicate significant variations in the relative abundances of the dominant taxa over the past 100,000 years since the isotope stage 5. The transfer function estimates of faunal sea surface temperatures (SST) correlate well with a long-term (104-105 years) trend of global glaciation. About 65,000 years ago, there was an observable change in the mode of SST variability as many low-latitude records have shown. These findings suggest that the SCS surface circulation and the East Asian winter monsoon systems are mainly driven by variations in global glaciation levels. The association of surface ocean cooling in the SCS with global climatic events suggests that fluctuations in the strength of the East Asian winter monsoon may be linked to shifts in the latitudinal position of the westerly winds and the Siberian high-pressure system.
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The Indian monsoon system is an important climate feature of the northern Indian Ocean. Small variations of the wind and precipitation patterns have fundamental influence on the societal, agricultural, and economic development of India and its neighboring countries. To understand current trends, sensitivity to forcing, or natural variation, records beyond the instrumental period are needed. However, high-resolution archives of past winter monsoon variability are scarce. One potential archive of such records are marine sediments deposited on the continental slope in the NE Arabian Sea, an area where present-day conditions are dominated by the winter monsoon. In this region, winter monsoon conditions lead to distinctive changes in surface water properties, affecting marine plankton communities that are deposited in the sediment. Using planktic foraminifera as a sensitive and well-preserved plankton group, we first characterize the response of their species distribution on environmental gradients from a dataset of surface sediment samples in the tropical and sub-tropical Indian Ocean. Transfer functions for quantitative paleoenvironmental reconstructions were applied to a decadal-scale record of assemblage counts from the Pakistan Margin spanning the last 2000?years. The reconstructed temperature record reveals an intensification of winter monsoon intensity near the year 100 CE. Prior to this transition, winter temperatures were >1.5°C warmer than today. Conditions similar to the present seem to have established after 450 CE, interrupted by a singular event near 950 CE with warmer temperatures and accordingly weak winter monsoon. Frequency analysis revealed significant 75-, 40-, and 37-year cycles, which are known from decadal- to centennial-scale resolution records of Indian summer monsoon variability and interpreted as solar irradiance forcing. Our first independent record of Indian winter monsoon activity confirms that winter and summer monsoons were modulated on the same frequency bands and thus indicates that both monsoon systems are likely controlled by the same driving force.
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In the present paper, the ecology and feeding habits of euphausiids are described. The samples were taken at the time of the NE-monsoon (1964/65) by R. V. "Meteor" in the Arabian Sea and adjacent waters. 24 species were determined. According to distribution of the species, the following marine areas can be distinguished: Arabian Sea: 24 species, dominant are Euphausia diomedeae, E. tenera, E. distinguenda, Stylocheiron carinatum. Gulf of Aden: 10 species, dominant are Euphausia diomedeae, E. distinguenda. Red Sea: 6 species, dominant are Euphausia diomedeae, E. distinguenda. Gulf of Oman : 5 Species, dominant are Euphausia distinguenda, Pseudeupbaufia latifrons. Persian Gulf: 1 species - Pseudeuphausia latifrons. The total number of euphausiids indicate the biomass of this group. High densities of euphausiids (200-299 and > 300 individuals/100 m**3) occur in the innermost part of the Gulf cf Aden, in the area south of the equator near the African east coast, near Karachi (Indian west coast) and in the Persian Gulf. Comparison with data relating to production biology confirms that these are eutrophic zones which coincide with areas in which upwelling occurs at the time of the NE-monsoon. The central part of the Arabian Sea differs from adjacent waters by virtue of less dense euphausiid populations (> 199 individuals/100 m**3). Measurements relating to production biology demonstrate a relatively low concentration of primary food sources. Food material was ascertained by analysis of stomach content. The following omnivorous species were examined: Euphausia diomedeae, E. distinguenda, E. tenera, Pseudeuphausia latifrons and Thysanopoda tricuspidata. Apart from crustacean remains large numbers of Foraminifera, Radiolaria, tintinnids, dinoflagellates were found in the stomachs. Quantitatively crustaceans form the most important item in the diet. Food selection on the basis of size and form appears to be restricted to certain genera of tintinnids. The genera Stylocheiron and Nematoscelis are predators. Only crustacean remains were found in the stomachs of Stylocheiron abbreviatum, whereas Radiolaria, Foraminifera and tintinnids occurred to some extent in Nematasceli sp. Different euphausiids in the food chain in the Arabian Sea. In omnivorous species the position is variable, since they not only feed by filtering autotrophic and heterotrophic Protista, but also by predation on zooplankton. Carnivorous species without filtering apparatus feed exclusively on zooplankton of the size of copepods. Only these species are well established as occupying a higher position in the food chain. The parasitic protozoan Tbalassomyces fagei was found on Euphausia diomedeae, E. fenera, E. distinguenda and E. sanzoi.
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Site 723 is located in a water depth of 808 m at the center of the oxygen minimum zone and the middle part of the main thermocline on the Oman Margin. Oxygen isotope curves of planktonic delta18OP and benthic delta18OB can be traced back continuously to Stage 23 with high resolution measurements. A tentative correlation to Stage 53 has been tried using oxygen isotope stratigraphy. The amplitudes of the fluctuations of the benthic delta18OB curve are small, compared with the planktonic delta18OP curve. The delays of benthic oxygen isotopes delta18OB related to the planktonic delta18OP appear in the transgressive stages. Carbon isotopes of benthic delta13CB and planktonic delta13CP generally show an inverse correlation with oxygen isotope values delta18OB and delta18OB and delta18OP, however, the changes of delta13C are more gradual than those of delta18O during transgressive stages in spite of the synchronized changes of delta13C with those of delta18O during regressive stages. The difference of oxygen isotope between benthic and planktonic foraminifers represents the degree of pushing up the thermocline by upwelling, and the difference of carbon isotope represents the relative amount of upwelling Sigma[CO2] to the biological uptake in the surface water. These isotopic differences can be used as indicators of upwelling and show strong upwelling in the interglacial and weak upwelling in the glacial stages. The organic carbon content is correlated with the isotopic upwelling indicators, and higher content is correlated with the isotopic upwelling indicators and higher content appears in the interglacial stages. The calculated rate of sedimentation based on oxygen isotope stratigraphy in glacial stages is significantly high, two to four times that of interglacial stages, and the absolute flux of fluvial sediments with variability of lithofacies increased in the glacial stage. The present glacial-interglacial cycle with the fluctuation of upwelling relating to the southwest monsoon can be traced back to Stage 8, 250 ka. From Stage 8 to 12, 250-450 ka, the upwelling indicator of oxygen isotope difference did not show such distinct cyclicity. For Stages 12-15, 450-600 ka, the upwelling can be estimated as strong as in interglacial stage of the present cycles, with slightly weak upwelling in the glacial stage. This upwelling and climate can be traced back to the late Pliocene. The strongest upwelling can be estimated in the Pliocene-Pleistocene time by the isotopic indicators and the high organic carbon content.
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The Northern Bay of Bengal (NBoB) is a globally important region for deep-sea organic matter (OM) deposition due to massive fluvial discharge from the Ganges-Brahmaputra-Meghna (G-B-M) rivers and moderate to high surface productivity. Previous studies have focused on carbon burial in turbiditic sediments of the Bengal Fan. However, little is known about the storage of carbon in pelagic and hemipelagic sediments of the Bay of Bengal over millennial time scales. This study presents a comprehensive history of OM origin and fate as well as a quantification of carbon sediment storage in the Eastern Bengal Slope (EBS) during the last 18 ka. Bulk organic proxies (TOC, TIC, TN, d13CTOC, d15NTN) and content and composition of total hydrolysable amino acids (THAA) in a sediment core (SO188-342KL) from the EBS were analyzed. Three periods of high OM accumulation were identified: the Late Glacial (LG), the Bölling/Alleröd (B/A), and the Early Holocene Climatic Optimum (EHCO). Lower eustatic sea level before 15 ka BP allowed a closer connection between the EBS and the fluvial debouch, favoring high terrestrial OM input to the core site. This connection was progressively lost between 15 and 7 ka BP as sea level rose to its present height and terrestrial OM input decreased considerably. Export and preservation of marine OM was stimulated during periods of summer monsoon intensification (B/A and EHCO) as a consequence of higher surface productivity enhanced by cyclonic-eddy nutrient pumping and fluvial nutrient delivery into the photic zone. Changes in the THAA composition indicate that the marine plankton community structure shifted from calcareous-dominated before 13 ka BP to siliceous-dominated afterwards. They also indicate that the relative proportion of marine versus terrestrial OM deposited at site 342KL was primarily driven by relative sea level and enlarged during the Holocene. The ballasting effect of lithogenic particles during periods of high coastal proximity and/or enhanced fluvial discharge promoted the export and preservation of OM. The high organic carbon accumulation rates in the EBS during the LG (18-17 ka BP) were 5-fold higher than at present and comparable to those of glacial upwelling areas. Despite the differences in sediment and OM transport and storage among the Western and Eastern sectors of the NBoB, this region remains important for global carbon sequestration during sea level low-stands. In addition, the summer monsoon was a key promotor of terrestrial and marine OM export to the deep-ocean, highlighting its relevance as regulator of the global carbon budget.
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Results from sediment trap experiments conducted in the seasonal upwelling area off south Java from November 2000 until July 2003 revealed significant monsoon-, El Niño-Southern Oscillation-, and Indian Ocean Dipole-induced seasonal and interannual variations in flux and shell geochemistry of planktonic foraminifera. Surface net primary production rates together with total and species-specific planktonic foraminiferal flux rates were highest during the SE monsoon-induced coastal upwelling period from July to October, with three species Globigerina bulloides, Neogloboquadrina pachyderma dex., and Globigerinita glutinata contributing to 40% of the total foraminiferal flux. Shell stable oxygen isotopes (d18O) and Mg/Ca data of Globigerinoides ruber sensu stricto (s.s.), G. ruber sensu lato (s.l.), Neogloboquadrina dutertrei, Pulleniatina obliquiloculata, and Globorotalia menardii in the sediment trap time series recorded surface and subsurface conditions. We infer habitats of 0-30 m for G. ruber at the mixed layer depth, 60-80 m (60-90 m) for P. obliquiloculata (N. dutertrei) at the upper thermocline depth, and 90-110 m (100-150 m) for G. menardii in the 355-500 mm (>500 µm) size fraction corresponding to the (lower) thermocline depth in the study area. Shell Mg/Ca ratio of G. ruber (s.l. and s.s.) reveals an exponential relationship with temperature that agrees with published relationships particularly with the Anand et al. (2003) equations. Flux-weighted foraminiferal data in sediment trap are consistent with average values in surface sediment samples off SW Indonesia. This consistency confirms the excellent potential of these proxies for reconstructing past environmental conditions in this part of the ocean realm.
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Pelagic clay of the east-central Pacific province is shown to be a mixture of three primary detrital components, reflecting continental source areas in Asia, North America, and Central and South America. Relative contributions from each source area are a function of geography, and this distribution appears to have remained constant over the past five million years, despite changing flux rates. A Q-mode factor analysis of downcore records for Pb, Sr, and Nd isotopes identified three factors that account for 98% of the total variance. These factors represent the radiogenic isotopic signatures of 1) late Cenozoic Asian dust, which dominates in the central North Pacific; 2) North American continental hemipelagic/eolian sources, restricted mainly to the easternmost North Pacific at ~30 °N latitude; and 3) Central and South American sources, restricted to areas east of ~100 °W longitude. South of the Intertropical Convergence Zone (~6 °N), the Asian dust signature diminishes abruptly. We conclude that late Cenozoic Asian dust sources can be isotopically differentiated downcore from both North American and South and Central American sources in the eastcentral Pacific. This approach has a utility for identifying changes in long-term Cenozoic atmospheric circulation patterns.
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In June 2015, legal frameworks of the Asian Infrastructural Investment Bank were signed by its 57 founding members. Proposed and initiated by China, this multilateral development bank is considered to be an Asian counterpart to break the monopoly of the World Bank and the International Monetary Fund. In October 2015, China’s Central Bank announced a benchmark interest rate cut to combat the economic slowdown. The easing policy coincides with the European Central Bank’s announcement of doubts over US Fed’s commitment to raise interest rates. Global stock markets responded positively to China’s move, with the exception of the indexes from Wall Street (Bland, 2015; Elliott, 2015). In the meantime, China’s ‘One Belt, One Road’ (or New Silk Road Economic Belt) became atopic of discourse in relation to its growing global economy, as China pledged $40 billion to trade and infrastructure projects (Bermingham, 2015). The foreign policy aims to reinforce the economic belt from western China through Central Asia towards Europe, as well as to construct maritime trading routes from coastal China through the South China Sea (Summers, 2015). In 2012, The Economist launched a new China section, to reveal the complexity of the‘meteoric rise’ of China. John Micklethwait, who was then the chief editor of the magazine, said that China’s emergence as a global power justified giving it a section of its own(Roush, 2012). In July 2015, Hu Shuli, the former chief editor of Caijing, announced the launch of a think tank and financial data service division called Caixin Insight Group, which encompasses the new Caixin China Purchasing Managers Index (PMI). Incooperation with with Markit Group, a principal global provider of PMI, the index soon became a widely cited economic indicator. One anecdote from November’s Caixin shows how much has changed: in a high-profile dialogue between Hu Shuli and Kevin Rudd, Hu insisted on asking questions in English; interestingly, the former Prime Minister of Australia insisted on replying in Chinese. These recent developments point to one thing: the economic ascent of China and its increasing influence on the power play between economics and politics in world markets. China has begun to take a more active role in rule making and enforcement under neoliberal frameworks. However, due to the country’s size and the scale of its economy in comparison to other countries, China’s version of globalisation has unique characteristics. The ‘Capitalist-socialist’ paradox is vital to China’s market-oriented transformation. In order to comprehend how such unique features are articulated and understood, there are several questions worth investigating in the realms of media and communication studies,such as how China’s neoliberal restructuring is portrayed and perceived by different types of interested parties, and how these portrayals are de-contextualised and re-contextualised in global or Anglo-American narratives. Therefore, based on a combination of the themes of globalisation, financial media and China’s economic integration, this thesis attempts to explore how financial media construct the narratives of China’s economic globalisation through the deployment of comparative and multi-disciplinary approaches. Two outstanding elite financial magazines, Britain’s The Economist, which has a global readership and influence, and Caijing, China’s leading financial magazine, are chosen as case studies to exemplify differing media discourses, representing, respectively, Anglo-American and Chinese socio-economic and political backgrounds, as well as their own journalistic cultures. This thesis tries to answer the questions of how and why China’s neoliberal restructuring is constructed from a globally-oriented perspective. The construction primarily involves people who are influential in business and policymaking. Hence, the analysis falls into the paradigm of elite-elite communication, which is an important but relatively less developed perspective in studying China and its globalisation. The comparing of characteristics of narrative construction are the result of the textual analysis of articles published over a ten-year period (mid-1998 to mid-2008). The corpus of samples come from the two media outlets’ coverage of three selected events:China becoming a member of the World Trade Organization, its outward direct investment, and the listing of stocks of Chinese companies in overseas exchanges, which are mutually exclusive in sample collection and collectively exhaustive in the inclusion of articles regarding China’s economic globalisation. The findings help to understand that, despite language, socio-economic and political differences, elite financial media with globally-oriented readerships share similar methods of and approaches to agenda setting, the evaluation of news prominence, the selection of frame, and the advocacy of deeply rooted neoliberal ideas. The comparison of their distinctive features reflects the different phases of building up the sense of identity in their readers as global elites, as well as the different economic interests that are aligned with the corresponding readerships. However, textual analysis is only relevant in terms of exploring how the narratives are constructed and the elements they include; textual analysis alone prevents us from seeing the obstacles and the constrains of the journalistic practices of construction. Therefore, this thesis provides a brief discussion of interviews with practitioners from the two media, in order to understand how similar or different narratives are manifested and perceived, how the concept of neoliberalism deviates from and is justified in the Chinese context, and how and for what purpose deviations arise from Western to Chinese contexts. The thesis also contributes to defining financial media in the domain of elite communication. The relevant and closely interlocking concepts of globalisation, elitism and neoliberalism are discussed, and are used as a theoretical bedrock in the analysis of texts and contexts. It is important to address the agenda-setting and ideological role of elite financial media, because of its narrative formula of infusing business facts with opinions,which is important in constructing the global elite identity as well as influencing neoliberal policy-making. On the other hand, ‘journalistic professionalism’ has been redefined, in that the elite identity is shared by the content producer, reader and the actors in the news stories emerging from the much-compressed news cycle. The professionalism of elite financial media requires a dual definition, that of being professional in the understanding of business facts and statistics, and that of being professional in the making sense of stories by deploying economic logic.
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Ten GPS-Met stations were installed in northwest Mexico from June - September 2013. Each station included a Trimble NetR9 GPS receiver for PWV and a Vaisala WXT520 surface meteorological package measuring wind speed and direction, air temperature, humidity, pressure and precipitation. The geographic location, elevation and data period for each station are provided in Serra et al. (2016). The GPS receiver at Rayon failed on July 16, 21 days after installation, thus these data are not included in the archive but are available upon request (yserra@uw.edu). Data include 1-min surface meteorological variables, while the GPS PWV is calculated at 5-min intervals. A full description of the experiment can be found in Serra et al., 2016: Bull. Am. Meteor. Soc., doi: 10.1175/BAMS-D-14-00250.1.
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In this paper, we use an observational dataset built from Argo in situ profiles to describe the main large-scale patterns of intraseasonal mixed layer depth (MLD) variations in the Indian Ocean. An eddy permitting (0.25A degrees) regional ocean model that generally agrees well with those observed estimates is then used to investigate the mechanisms that drive MLD intraseasonal variations and to assess their potential impact on the related SST response. During summer, intraseasonal MLD variations in the Bay of Bengal and eastern equatorial Indian Ocean primarily respond to active/break convective phases of the summer monsoon. In the southern Arabian Sea, summer MLD variations are largely driven by seemingly-independent intraseasonal fluctuations of the Findlater jet intensity. During winter, the Madden-Julian Oscillation drives most of the intraseasonal MLD variability in the eastern equatorial Indian Ocean. Large winter MLD signals in northern Arabian Sea can, on the other hand, be related to advection of continental temperature anomalies from the northern end of the basin. In all the aforementioned regions, peak-to-peak MLD variations usually reach 10 m, but can exceed 20 m for the largest events. Buoyancy flux and wind stirring contribute to intraseasonal MLD fluctuations in roughly equal proportions, except for the Northern Arabian Sea in winter, where buoyancy fluxes dominate. A simple slab ocean analysis finally suggests that the impact of these MLD fluctuations on intraseasonal sea surface temperature variability is probably rather weak, because of the compensating effects of thermal capacity and sunlight penetration: a thin mixed-layer is more efficiently warmed at the surface by heat fluxes but loses more solar flux through its lower base.
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2014
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2014
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ABSTRACT: Brazil is the second - largest soybean producer. With the arrival of Asian soybean rust in the Western Hemisphere in 2001, a considerable amount of resources has been allocated to understand and control this important yield - limiting disease. Due its rapidly dissemination, in 2004, the federal government led an effort to create the Asian soybean rust consortium, with the main goal of coordinating research activities involving public and private sector. This paper describes the development of a mobile application, designed to support the Asian Soybean Rust Consortium to monitor, in time and space, occurrences of Asian soybean rust in Brazil. RESUMO: O Brasil é o segundo maior produtor de soja do mundo. Com a chegada da ferrugem da soja no hemisfério ocidental em 2001, uma quantidade considerável de recursos foram alocados para entender e controlar esta importante doença. Devido a sua rápida disseminação, em 2004, o governo federal uniu esforços e criou o Consórcio Antiferrugem, cujo objetivo principal seria de coordenar atividades de pesquisa envolvendo empresas públicas e privadas. Este artigo apresenta o desenvolvimento de um aplicativo móvel, projetado para auxiliar este Consórcio no monitoramento em tempo e espaço, de ocorrências de ferrugem asiática de soja no Brasil.
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2015