A large epeiric methanogenic Bambui sea in the core of Gondwana supercontinent?     

Sergio Caetano-Filho  Pierre Sansjofre  Magali Ader  Gustavo M.Paula-Santos  Cristian Guacaneme  Marly Babinski  Carolina Bedoya-Rueda  Matheus Kuchenbecker  Humberto L.S.Reis  Ricardo I.F.Trindade 《地学前缘(英文版)》2021,12(1):203-218

Carbon isotope compositions of both sedimentary carbonate and organic matter can be used as key proxies of the global carbon cycle and of its evolution through ...  相似文献   

A model of diffuse degassing at three subduction-related volcanoes     

Glyn Williams-Jones  John Stix  Martin Heiligmann  Anne Charland  Barbara Sherwood Lollar  N. Arner  Gustavo V. Garzón  Jorge Barquero  Erik Fernandez 《Bulletin of Volcanology》2000,62(2):130-142

2 and δ¹³C in soil gas were measured at three active subduction-related stratovolcanoes (Arenal and Poás, Costa Rica; Galeras, Colombia). In general, Rn, CO₂ and δ¹³C values are higher on the lower flanks of the volcanoes, except near fumaroles in the active craters. The upper flanks of these volcanoes have low Rn concentrations and light δ¹³C values. These observations suggest that diffuse degassing of magmatic gas on the upper flanks of these volcanoes is negligible and that more magmatic degassing occurs on the lower flanks where major faults and greater fracturing in the older lavas can channel magmatic gases to the surface. These results are in contrast to findings for Mount Etna where a broad halo of magmatic CO₂ has been postulated to exist over much of the edifice. Differences in radon levels among the three volcanoes studied here may result from differences in age, the degree of fracturing and faulting, regional structures or the level of hydrothermal activity. Volcanoes, such as those studied here, act as plugs in the continental crust, focusing magmatic degassing towards crater fumaroles, faults and the fractured lower flanks. Received: 16 December 1997 / Accepted: 27 January 2000  相似文献   

Predicting forest fire in the Brazilian Amazon using MODIS imagery and artificial neural networks     

Eduardo Eiji Maeda  Antonio Roberto Formaggio  Yosio Edemir Shimabukuro  Gustavo Felipe Balué Arcoverde  Matthew C. Hansen 《International Journal of Applied Earth Observation and Geoinformation》2009

The presented work describes a methodology that employs artificial neural networks (ANN) and multi-temporal imagery from the MODIS/Terra-Aqua sensors to detect areas of high risk of forest fire in the Brazilian Amazon. The hypothesis of this work is that due to characteristic land use and land cover change dynamics in the Amazon forest, forest areas likely to be burned can be separated from other land targets. A study case was carried out in three municipalities located in northern Mato Grosso State, Brazilian Amazon. Feedforward ANNs, with different architectures, were trained with a backpropagation algorithm, taking as inputs the NDVI values calculated from MODIS imagery acquired during five different periods preceding the 2005 fire season. Selected samples were extracted from areas where forest fires were detected in 2005 and from other non-burned forest and agricultural areas. These samples were used to train, validate and test the ANN. The results achieved a mean squared error of 0.07. In addition, the model was simulated for an entire municipality and its results were compared with hotspots detected by the MODIS sensor during the year. A histogram analysis showed that the spatial distribution of the areas with fire risk were consistent with the fire events observed from June to December 2005. The ANN model allowed a fast and relatively precise method to predict forest fire events in the studied area. Hence, it offers an excellent alternative for supporting forest fire prevention policies, and in assisting the assessment of burned areas, reducing the uncertainty involved in currently used methods.  相似文献   

Observing GRB host galaxies with the integral field unit of X‐shooter     

H. Flores  P. Goldoni  F. Royer  S. Piranomonte  S.D. Vergani  F. Onori  E. Palazzi  S. Covino  S. Randich  F. Hammer  E. Pian  S. Savaglio  G. Tagliaferri 《Astronomische Nachrichten》2011,332(3):288-291

Using the integral field unit of X‐shooter at VLT, we have recovered the first velocity fields of GRB host galaxies at redshift <0.6. This facility is able to recover not only the velocity fields from almost all emission lines thanks to an unrivaled wavelength coverage, but also to recover maps of physical properties. We present the preliminary analysis of X‐shooter/IFU observations dedicated to the study of GRB host galaxies undertaken in the frame of the Italian‐French GTO program. Our goal is to understand the physical processes at the origin of the GRB by analyzing in detail the spatial distributions of the kinematics, metallicities, extinction, star‐formation, and how they are inter‐related (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Ocean heat content for tropical cyclone intensity forecasting and its impact on storm surge   总被引：1，自引：0，他引：1  

I.-I. Lin  Gustavo J. Goni  John A. Knaff  Cristina Forbes  M. M. Ali 《Natural Hazards》2013,66(3):1481-1500

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Integrating the LISFLOOD‐FP 2D hydrodynamic model with the CAESAR model: implications for modelling landscape evolution     

Tom J. Coulthard  Jeff C. Neal  Paul D. Bates  Jorge Ramirez  Gustavo A. M. de Almeida  Greg R. Hancock 《地球表面变化过程与地形》2013,38(15):1897-1906

Landscape evolution models (LEMs) simulate the geomorphic development of river basins over long time periods and large space scales (100s–1000s of years, 100s of km²). Due to these scales they have been developed with simple steady flow models that enable long time steps (e.g. years) to be modelled, but not shorter term hydrodynamic effects (e.g. the passage of a flood wave). Nonsteady flow models that incorporate these hydrodynamic effects typically require far shorter time steps (seconds or less) and use more expensive numerical solutions hindering their inclusion in LEMs. The recently developed LISFLOOD‐FP simplified 2D flow model addresses this issue by solving a reduced form of the shallow water equations using a very simple numerical scheme, thus generating a significant increase in computational efficiency over previous hydrodynamic methods. This leads to potential convergence of computational cost between LEMs and hydrodynamic models, and presents an opportunity to combine such schemes. This paper outlines how two such models (the LEM CAESAR and the hydrodynamic model LISFLOOD‐FP) were merged to create the new CAESAR‐Lisflood model, and through a series of preliminary tests shows that using a hydrodynamic model to route flow in an LEM affords many advantages. The new model is fast, computationally efficient and has a stronger physical basis than a previous version of the CAESAR model. For the first time it allows hydrodynamic effects (tidal flows, lake filling, alluvial fans blocking valley floor) to be represented in an LEM, as well as producing noticeably different results to steady flow models. This suggests that the simplification of using steady flow in existing LEMs may bias their findings significantly. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Unique episodic groundwater recharge event in a South American sedimentary aquifer and its long-term impact on baseflow     

Maurício Dambros Melati  Fernando Mainardi Fan  Gustavo Barbosa Athayde  Pedro Antônio Roehe Reginato  Walter Collischonn  Camila de Vasconcelos Muller Athayde 《水文研究》2021,35(10):e14388

The anomalous entrance of water into groundwater systems can affect storage throughout long periods and normally relies on infrequent and irregular pulses of groundwater recharge defined by the term episodic recharge. Recently there was a groundwater recharge of large magnitude with unknown circumstances in the Caiuá aquifer. This unique event was explored in detail here and allowed to better understand the occurrence of such events in humid subtropical climates in South America. For this study, groundwater monitoring daily data from the Integrated Groundwater Monitoring Network was used combined with a specific yield obtained from geophysical wireline logging to obtain groundwater recharge rates. To improve the investigation, we also used a baseflow separation method to obtain the groundwater contribution into local rivers. The groundwater storage variations were also assessed by remote sensing with the GRACE data. Results showed the importance of high soil moisture storage on the occurrence of large episodic recharge events. We estimated that the groundwater recharger volumes derived from 1 year that included the unique episodic recharge observed (total of 866 mm for April 2015–March 2016) were comparable with the sum of 7 years of groundwater recharge (total of 867 mm). Atypical rainfall in winter periods were responsible for the increase in soil moisture that explained that unique event. GRACE-based GWS showed concordance detecting the occurrence of the unique episodic recharge. However, the variation in terms of volumes obtained by GRACE does not represent the behaviour observed in the aquifer by the WTF method. The results also indicated that changes in aquifer storage caused by episodic recharge events directly affect low flows in rivers over long periods. The main knowledge gap addressed here relates to exploring a unique episodic recharge event quite rare to observe with its long-term impacts on hydroclimatic variability over a humid subtropical portion of the Caiuá aquifer.  相似文献   

DDT in endangered Galapagos sea lions (Zalophus wollebaeki)     

Alava JJ  Ross PS  Ikonomou MG  Cruz M  Jimenez-Uzcátegui G  Dubetz C  Salazar S  Costa DP  Villegas-Amtmann S  Howorth P  Gobas FA 《Marine pollution bulletin》2011,62(4):660-671

We characterize for the first time the presence of DDT and its metabolites in tropical Galapagos sea lions (Zalophus wolleabeki). ∑DDT concentrations in Galapagos sea lion pups sampled in 2005 and 2008 ranged from 16 to 3070 μg/kg lipid. Concentrations of ∑DDT in pups in 2008 averaged 525 μg/kg lipid and were 1.9 times higher than that (281 μg/kg lipid) detected in pups in 2005. These concentrations are lower than those reported in many pinnipeds elsewhere, comparable to those in Hawaiian monk seals, and higher than those in southern elephant seals. The health risk characterization showed that 1% of the male pups exceeded the p,p′-DDE toxic effect concentration associated with anti-androgenic effects reported in rats. The findings provide preliminary guidance on the relationship between DDT use and ecological impacts, serving as a reference point against which possible future impact of tropical DDT use can be assessed.  相似文献   

Gillnet fisheries as a major mortality factor of Magellanic penguins in wintering areas     

Cardoso LG  Bugoni L  Mancini PL  Haimovici M 《Marine pollution bulletin》2011,62(4):840-844

The incidental capture in fisheries is probably the main conservation problem affecting seabirds. While the capture of albatrosses and petrels on longline hooks is well-known worldwide, the bycatch of diving seabirds in gillnets is an overlooked conservation problem. During a winter coastal fishing trip, the capture of Magellanic penguins (Spheniscus magellanicus) was recorded in driftnet and bottom setnet fisheries for the first time in southern Brazil. The highest captures rates were found in driftnets, from 146.5 to 545.5 penguins/km² of net and a total of 56 dead penguins were recorded. In the bottom gillnet, a total of 12 birds were killed and the capture rates varied from 41.7 to 125.0 penguins/km² of net. Although preliminary, the results presented in this paper were consistent between sets. If we consider the magnitude of driftnet and setnet fishing fleets, and that most dead penguins were adults, the impact upon Magellanic penguin populations is probably significant.  相似文献   

Stratospheric ozone depletion: a key driver of recent precipitation trends in South Eastern South America     

Paula L. M. Gonzalez  Lorenzo M. Polvani  Richard Seager  Gustavo J. P. Correa 《Climate Dynamics》2014,42(7-8):1775-1792

On a hemispheric scale, it is now well established that stratospheric ozone depletion has been the principal driver of externally forced atmospheric circulation changes south of the Equator in the last decades of the 20th Century. The impact of ozone depletion has been felt over the entire hemisphere, as reflected in the poleward drift of the midlatitude jet, the southward expansion of the summertime Hadley cell and accompanying precipitation trends deep into the subtropics. On a regional scale, however, surface impacts directly attributable to ozone depletion have yet to be identified. In this paper we focus on South Eastern South America (SESA), a region that has exhibited one of the largest wetting trends during the 20th Century. We study the impact of ozone depletion on SESA precipitation using output from 6 different climate models, spanning a wide range of complexity. In all cases we contrast pairs of model integrations with and without ozone depletion, but with all other forcings identically specified. This allows for unambiguous attribution of the computed precipitation trends. All 6 climate models consistently reveal that stratospheric ozone depletion results in a significant wetting of SESA over the period 1960–1999. Taken as a whole, these model results strongly suggest that the impact of ozone depletion on SESA precipitation has been as large as, and quite possibly larger than, the one caused by increasing greenhouse gases over the same period.  相似文献