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151.
Carvalho S Gaspar MB Moura A Vale C Antunes P Gil O da Fonseca LC Falcão M 《Marine pollution bulletin》2006,52(11):1414-1424
This study reports the longitudinal distribution of sediment properties, including inorganic and organic contaminants, and the structure of the benthic community in Obidos lagoon, a coastal system permanently connected to the sea and with negligible freshwater sources. Sediments from the upper to central lagoon consist of fine particles (91%) and from the lower lagoon of sands (94%). Chemical composition is strongly correlated to the percentage of fine particles. Contamination is relatively low in those sediments suggesting the effect of diffuse sources. The increase in organic matter content from down- to upstream areas was associated with the dominance of opportunistic species, while sensitive and indifferent species to organic enrichment were mainly associated to the clean sandy downstream area. The marine biotic index (AMBI) was suitable for the discrimination of the biological and environmental gradients in the Obidos lagoon and was highly related with the gradient of organic matter content in this system. 相似文献
152.
Christian Creixell Miguel ngel Parada Pierrick Roperch Diego Morata Csar Arriagada Carlos Prez de Arce 《Tectonophysics》2006,425(1-4):101-122
The Concón Mafic Dike Swarm (CMDS) consists of basaltic to andesitic dikes emplaced into deformed Late Paleozoic granitoids during the development of the Jurassic arc of central Chile. The dikes are divided into an early group of thick dikes (5–12 m) and a late group of thin dikes (0.5–3 m). Two new amphibole 40Ar/39Ar dates obtained from undeformed and deformed dikes, constrain the age of emplacement and deformation of the CMDS between 163 and 157 Ma. Based on radiometric ages, field observations, AMS studies and petrographic data, we conclude that the emplacement of the CMDS was syntectonic with the Jurassic arc extension and associated with sinistral displacements along the NW-trending structures that host the CMDS. The common occurrence of already deformed and rotated xenoliths in the dikes indicates that deformation in the granitoids started previously.The early thick dikes and country rocks appear to have been remagnetized during the exhumation of deep-seated coastal rocks in the Early Cretaceous (around 100 Ma). The remanent magnetization in late thin dikes is mainly retained by small amounts of low-Ti magnetite at high temperature and pyrrhotite at low temperature. The magnetization in these dikes appears to be primary in origin. Paleomagnetic results from the thin dikes also indicate that the whole area was tilted 23° to the NNW during cooling of the CMDS.The NNW–SSE extension vectors deduced from the paleomagnetic data and internal fabric of dikes are different with respect to extension direction deduced for the Middle–Late Jurassic of northern Chile, pointing to major heterogeneities along the margin of the overriding plate during the Mesozoic or differences in the mechanisms driving extension during such period. 相似文献
153.
AGUIRRE-SALADO Carlos Arturo TREVIO-GARZA Eduardo Javier AGUIRRE-CALDERóN Oscar Alberto JIMéNEZ-PéREZ Javier GONZáLEZ-TAGLE Marco Aurelio VALDEZ-LAZALDE José René MIRANDA-ARAGóN Liliana AGUIRRE-SALADO Alejandro Iván 《地理学报(英文版)》2012,22(4):669-680
Spatially-explicit estimation of aboveground biomass(AGB) plays an important role to generate action policies focused in climate change mitigation,since carbon(C) retained in the biomass is vital for regulating Earth’s temperature.This work estimates AGB using both chlorophyll(red,near infrared) and moisture(middle infrared) based normalized vegetation indices constructed with MCD43A4 MODerate-resolution Imaging Spectroradiometer(MODIS) and MOD44B vegetation continuous fields(VCF) data.The study area is located in San Luis Potosí,Mexico,a region that comprises a part of the upper limit of the intertropical zone.AGB estimations were made using both individual tree data from the National Forest Inventory of Mexico and allometric equations reported in scientific literature.Linear and nonlinear(expo-nential) models were fitted to find their predictive potential when using satellite spectral data as explanatory variables.Highly-significant correlations(p = 0.01) were found between all the explaining variables tested.NDVI62,linked to chlorophyll content and moisture stress,showed the highest correlation.The best model(nonlinear) showed an index of fit(Pseudo-r2) equal to 0.77 and a root mean square error equal to 26.00 Mg/ha using NDVI62 and VCF as explanatory variables.Validation correlation coefficients were similar for both models:lin-ear(r = 0.87**) and nonlinear(r = 0.86**). 相似文献
154.
José Carlos G. Aguiar 《Singapore journal of tropical geography》2012,33(2):171-183
The vision of a borderless world, of people, ideas and products freely circulating within a self‐regulating market, is one that clashes with the emerging legal regime based on the punitive force of the state. After a period of liberalization, seen in the opening of national economies and the promotion of regional trade projects and free‐trade zones, the ambivalence of neoliberalism is manifest in a borderless capitalism that ambiguously depends on the securitization of national borders. Such a changing regime of state intervention is clearly seen at the Iguazú triangle – the tri‐border urban conglomerate that straddles Brazil, Paraguay and Argentina – where the illegality of informal cross‐border trading has been tolerated for decades. Recently stepped up police raids and controls hinder the passage of people and goods, while a new fiscal regime introduced in 2009 in Brazil attempts to regularize cross‐border trafficking by turning petty smugglers into micro entrepreneurs. Petty smugglers – dubbed sacoleiros– can hardly be defined as entrepreneurs and do not constitute an identifiable category of entrepreneurship but, as typical in the informal sector, act on opportunity and need. Drawing on ethnographic research, this paper contextualizes the programmes for border controls and regularizing smuggling inspired by neoliberal ideology in South America. 相似文献
155.
156.
Francisco Estrada Benjamín Martínez-López Cecilia Conde Carlos Gay-García 《Climatic change》2012,110(3-4):1029-1046
This paper presents a review of the methodology applied for generating the regional climate change scenarios utilized in important National Documents of Mexico, such as the Fourth National Communication to the United Nations Framework Convention on Climate Change, the Fourth National Report to the Convention on Biological Diversity and The Economics of Climate Change in Mexico. It is shown that these regional climate change scenarios, which are one of the main inputs to support the assessments presented in these documents, are an example of the erroneous use of statistical downscaling techniques. The arguments presented here imply that the work based on such scenarios should be revised and therefore, these documents are inadequate for supporting national decision- making. 相似文献
157.
Extreme climatic events in the Amazon basin 总被引:1,自引:0,他引:1
Jose Antonio Marengo Javier Tomasella Wagner R. Soares Lincoln M. Alves Carlos A. Nobre 《Theoretical and Applied Climatology》2012,107(1-2):73-85
During 2009 the Amazon basin was hit by a heavy flooding with a magnitude and duration few times observed in several decades. Torrential rain in northern and eastern Amazonia during the austral summer of 2008–2009 swelled the Amazon River and its tributaries. By July 2009, water levels of the Rio Negro, a major Amazon tributary, reached at Manaus harbor a new record, the highest mark of the last 107?years. During the 2008–2009 hydrological year, the rainy season on northern and northwestern Amazonia started prematurely, and was followed by a longer-than-normal rainy season. An anomalously southward migration of the ITCZ during May–June 2009, due to the warmer than normal surface waters in the tropical South Atlantic, was responsible for abundant rainfall in large regions of eastern Amazonia and Northeast Brazil from May to July 2009. We also compared the flood of 2009 with other major events recorded in 1989 and 1999. The hydrological consequences of this pattern were earlier than normal floods in Amazon northern tributaries, which peak discharges at their confluences with the main stem almost coincided with the peaks of southern tributaries. Since the time displacement of the contribution to the main stem of northern and southern Amazon tributaries is fundamental for damping flood waves in the main stem, the simultaneous combinations of peak discharges of tributaries resulted in an extreme flood. 相似文献
158.
Evolution and modulation of tropical heating from the last glacial maximum through the twenty-first century 总被引:1,自引:1,他引:0
Twentieth century observations show that during the last 50?years the sea-surface temperature (SST) of the tropical oceans has increased by ~0.5°C and the area of SST >26.5 and 28°C (arbitrarily referred to as the oceanic warm pool: OWP) by 15 and 50% respectively in association with an increase in green house gas concentrations, with non-understood natural variability or a combination of both. Based on CMIP3 projections the OWP is projected to double during twenty-first century in a moderate CO2 forcing scenario (IPCC A1B scenario). However, during the observational period the area of positive atmospheric heating (referred to as the dynamic warm pool, DWP), has remained constant. The threshold SST (T H ), which demarks the region of net heating and cooling, has increased from 26.6°C in the 1950s to 27.1°C in the last decade and it is projected to increase to ~28.5°C by 2100. Based on climate model simulations, the area of the DWP is projected to remain constant during the twenty-first century. Analysis of the paleoclimate model intercomparison project (PMIP I and II) simulations for the Last Glacial maximum and the Mid-Holocene periods show a very similar behaviour, with a larger OWP in periods of elevated tropical SST, and an almost constant DWP associated with a varying T H . The constancy of the DWP area, despite shifts in the background SST, is shown to be the result of a near exact matching between increases in the integrated convective heating within the DWP and the integrated radiative cooling outside the DWP as SST changes. Although the area of the DWP remains constant, the total tropical atmospheric heating is a strong function of the SST. For example the net heating has increased by about 10% from 1950 to 2000 and it is projected to increase by a further 20% by 2100. Such changes must be compensated by a more vigorous atmospheric circulation, with growth in convective heating within the warm pool, and an increase of subsiding air and stability outside the convective warm pool and an increase of vertical shear at the DWP boundaries. This finding is contrary to some conclusions from other studies but in accord with others. We discuss the similarities and differences at length. 相似文献
159.
In this paper, the unfeasibility of producing “objective” probabilistic climate change scenarios is discussed. Realizing that the knowledge of “true” probabilities of the different scenarios and temperature changes is unachievable, the objective must be to find the probabilities that are the most consistent with what our state of knowledge and expert judgment are. Therefore, subjective information plays, and should play, a crucial role. A new methodology, based on the Principle of Maximum Entropy, is proposed for constructing probabilistic climate change scenarios when only partial information is available. The objective is to produce relevant information for decision-making according to different agents’ judgment and subjective beliefs. These estimates have desirable properties such as: they are the least biased estimate possible on the available information; maximize the uncertainty (entropy) subject to the partial information that is given; The maximum entropy distribution assigns a positive probability to every event that is not excluded by the given information; no possibility is ignored. The probabilities obtained in this manner are the best predictions possible with the state of knowledge and subjective information that is available. This methodology allows distinguishing between reckless and cautious positions regarding the climate change threat. 相似文献
160.
The influence of ocean–atmosphere coupling on the simulation and prediction of the boreal winter Madden–Julian Oscillation
(MJO) is examined using the Seoul National University coupled general circulation model (CGCM) and atmospheric—only model
(AGCM). The AGCM is forced with daily SSTs interpolated from pentad mean CGCM SSTs. Forecast skill is examined using serial
extended simulations spanning 26 different winter seasons with 30-day forecasts commencing every 5 days providing a total
of 598 30-day simulations. By comparing both sets of experiments, which share the same atmospheric components, the influence
of coupled ocean–atmosphere processes on the simulation and prediction of MJO can be studied. The mean MJO intensity possesses
more realistic amplitude in the CGCM than in AGCM. In general, the ocean–atmosphere coupling acts to improve the simulation
of the spatio-temporal evolution of the eastward propagating MJO and the phase relationship between convection (OLR) and SST
over the equatorial Indian Ocean and the western Pacific. Both the CGCM and observations exhibit a near-quadrature relationship
between OLR and SST, with the former lagging by about two pentads. However, the AGCM shows a less realistic phase relationship.
As the initial conditions are the same in both models, the additional forcing by SST anomalies in the CGCM extends the prediction
skill beyond that of the AGCM. To test the applicability of the CGCM to real-time prediction, we compute the Real-time Multivariate
MJO (RMM) index and compared it with the index computed from observations. RMM1 (RMM2) falls away rapidly to 0.5 after 17–18
(15–16) days in the AGCM and 18–19 (16–17) days in the CGCM. The prediction skill is phase dependent in both the CGCM and
AGCM. 相似文献