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1.
Pierre‐Yves Pascal Claude Bellemare Wolfgang Sterrer Henricus T. S. Boschker Silvina Gonzalez‐Rizzo Olivier Gros 《Marine Ecology》2015,36(2):246-257
Haplognathia ruberrima is a cosmopolitan gnathostomulid species found in sulfur bacterial mats in mangroves in Guadeloupe (French West Indies). Haplognathia ruberrima presents a δ13C value lower than all measured meiofaunal grazers and lower than the available measured food sources of this environment. This low δ13C value can not be due to specific ingestion of 13C‐depleted methanogenic bacteria because abundances of those bacteria are reduced in surficial and deep sediments as revealed by δ13C of bacterial fatty acid. According to scanning electron microscope observations, no bacterial ectosymbionts were observed at the surface of the gnathostomulids, and transmission electron microscope views revealed the absence of bacterial endosymbionts. Energy‐dispersive X‐ray spectroscopy analysis detected low levels of sulfur (0.32%±0.8) in biological tissues of H. ruberrima, confirming the absence of thioautotrophic bacterial symbionts in these animals. Consequently, the low δ13C value of H. ruberrima can not be due to the presence of sulfur‐oxidizing symbionts but more probably to the selective and exclusive consumption of free‐living, sulfur‐oxidizing bacteria. 相似文献
2.
Silvina A. Solman E. Sanchez P. Samuelsson R. P. da Rocha L. Li J. Marengo N. L. Pessacg A. R. C. Remedio S. C. Chou H. Berbery H. Le Treut M. de Castro D. Jacob 《Climate Dynamics》2013,41(5-6):1139-1157
The capability of a set of 7 coordinated regional climate model simulations performed in the framework of the CLARIS-LPB Project in reproducing the mean climate conditions over the South American continent has been evaluated. The model simulations were forced by the ERA-Interim reanalysis dataset for the period 1990–2008 on a grid resolution of 50 km, following the CORDEX protocol. The analysis was focused on evaluating the reliability of simulating mean precipitation and surface air temperature, which are the variables most commonly used for impact studies. Both the common features and the differences among individual models have been evaluated and compared against several observational datasets. In this study the ensemble bias and the degree of agreement among individual models have been quantified. The evaluation was focused on the seasonal means, the area-averaged annual cycles and the frequency distributions of monthly means over target sub-regions. Results show that the Regional Climate Model ensemble reproduces adequately well these features, with biases mostly within ±2 °C and ±20 % for temperature and precipitation, respectively. However, the multi-model ensemble depicts larger biases and larger uncertainty (as defined by the standard deviation of the models) over tropical regions compared with subtropical regions. Though some systematic biases were detected particularly over the La Plata Basin region, such as underestimation of rainfall during winter months and overestimation of temperature during summer months, every model shares a similar behavior and, consequently, the uncertainty in simulating current climate conditions is low. Every model is able to capture the variety in the shape of the frequency distribution for both temperature and precipitation along the South American continent. Differences among individual models and observations revealed the nature of individual model biases, showing either a shift in the distribution or an overestimation or underestimation of the range of variability. 相似文献
3.
We present an analysis of a regional simulation of present-day climate (1981–1990) over southern South America. The regional
model MM5 was nested within time-slice global atmospheric model experiments conducted by the HadAM3H model. We evaluate the
capability of the model in simulating the observed climate with emphasis on low-level circulation patterns and surface variables,
such as precipitation and surface air mean, maximum and minimum temperatures. The regional model performance was evaluated
in terms of seasonal means, seasonal cycles, interannual variability and extreme events. Overall, the regional model is able
to capture the main features of the observed mean surface climate over South America, its seasonal evolution and the regional
detail due to topographic forcing. The observed regional patterns of surface air temperatures (mean, maxima and minima) are
well reproduced. Biases are mostly within 3°C, temperature being overestimated over central Argentina and underestimated in
mountainous regions during all seasons. Biases in northeastern Argentina and southeastern Brazil are positive during austral
spring season and negative in other seasons. In general, maximum temperatures are better represented than minimum temperatures.
Warm bias is larger during austral summer for maximum temperature and during austral winter for minimum temperature, mainly
over central Argentina. The broad spatial pattern of precipitation and its seasonal evolution are well captured; however,
the regional model overestimates the precipitation over the Andes region in all seasons and in southern Brazil during summer.
Precipitation amounts are underestimated over the La Plata basin from fall to spring. Extremes of precipitation are better
reproduced by the regional model compared with the driving model. Interannual variability is well reproduced too, but strongly
regulated by boundary conditions, particularly during summer months. Overall, taking into account the quality of the simulation,
we can conclude that the regional model is capable in reproducing the main regional patterns and seasonal cycle of surface
variables. The present reference simulation constitutes the basis to examine the climate change simulations resulting from
the A2 and B2 forcing scenarios which are being reported in a separate study. 相似文献
4.
Federico M. Ledesma Silvina Van der Molen Pedro J. Barón 《Journal of Sea Research》2010,63(3-4):213-216
The European green crab Carcinus maenas is a widely spread invasive species. Studying the most recently introduced population of the species in the Atlantic coast off Patagonia, it became apparent to us that carapaces (the dorsal cover of the visceral-cavity detaching from the rest of the exoskeleton after ecdysis) accumulated on the intertidal may be used as a valuable complementary material to analyze the size structure of crabs. However, since growth rate (and consequently size at instar) of crabs differs between males and females, finding a method to distinguish crab sex by observation of carapace morphology was necessary to allow the construction of independent size frequency distributions for each sex. In this work, we examined the shape of the carapaces from both sexes of C. maenas, and using Elliptical Fourier Analysis successfully identified sexual dimorphism. Thus, a reliable method to identify sexes by visual observation of the carapace was developed. Based on our results, we discuss the evolutionary significance of carapace form differentiation of both sexes. 相似文献
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6.
The simulated low-frequency variability patterns of the atmospheric circulation, ranging from interannual to interdecadal timescales, are studied in an area encompassing southern South America. The experiment is a transient simulation performed with the IPSL CCM2 coupled global model, in which the greenhouse forcing is continuously increasing. The main modes of low-frequency variability are found to remain stationary throughout the simulation, suggesting they depend more on the internal dynamics of the atmospheric flow than on its external forcing. Inspection of the circulation regimes that represent the more recurrent patterns at interannual and interdecadal timescales showed that climate change manifests itself as a change in regime population, suggesting that the negative phase of the Antarctic Oscillation-like pattern becomes more frequented in a climate change scenario. Changes of regime occurrence are superimposed to a positive trend whose spatial pattern is reminiscent of the structure of the Antarctic Oscillation-mode of variability. Moreover, it resembles the spatial patterns of those regimes that show a significant change in population. The change in regime frequencies of the circulation patterns of low-frequency variability are in opposite phase with respect to the trend, thus, the behaviour of these patterns of variability, superimposed to a changing mean state, modulates the climate change signal. The analysis of the high frequencies, in terms of recurrent patterns representing intraseasonal and synoptic-scale of variability, shows no significant changes in regime characteristics, concerning both spatial and temporal behaviour. 相似文献
7.
Daniel Richarte Marianela Lupari Agustina Pesce Silvina Nacif Mario Gimenez 《地学前缘(英文版)》2018,9(1):239-248
The San Rafael Block(SRB)is part of one of the main retroarc volcanic provinces in southern Central Andes in Mendoza,Argentina.This block is located in the Andean foothills between the orogenic front and foreland basement uplifts of late Miocene age.In order to analyze the geochronological evolution of the Quaternary volcanism in the region,several geologic and geophysical studies have been conducted.Nevertheless,the crust,where the SRB is located,has not been well characterized yet.Based on gravimetric and magnetic data,together with isostatic and elastic thickness analyses,we modeled the crustal structure of the area.Information obtained has allowed us to understand the crust where the SRB and the Payenia volcanic province are located.Bouguer anomalies indicate that the SRB presents higher densities to the North of Cerro Nevado and Moho calculations suggest depths for this block between 40 and 50 km.Determinations of elastic thickness would indicate that the crust supporting the San Rafael Block presents values of approximately 10 km,being enough to support the block loading.However,in the Payenia region,elastic thickness values are close to zero due to the regional temperature increase. 相似文献
8.
Carolina Montero‐López Manfred R. Strecker Taylor F. Schildgen Fernando Hongn Silvina Guzmán Bodo Bookhagen Masafumi Sudo 《地学学报》2014,26(6):454-460
A valley‐filling ignimbrite re‐exposed through subsequent river incision at the southern margin of the Andean (Puna) plateau preserves pristine geological evidence of pre‐late Miocene palaeotopography in the north western Argentine Andes. Our new 40Ar/39Ar dating of the Las Papas Ignimbrites yields a plateau age of 9.24 ± 0.03 Ma, indicating valley‐relief and orographic‐barrier conditions comparable to the present‐day. A later infill of Plio–Pleistocene coarse conglomerates has been linked to wetter conditions, but resulted in no additional net incision of the Las Papas valley, considering that the base of the ignimbrite remains unexposed in the valley bottom. Our observations indicate that at least 550 m of local plateau margin relief (and likely >2 km) existed by 9 Ma at the southern Puna margin, which likely aided the efficiency of the orographic barrier to rainfall along the eastern and south eastern flanks of the Puna and causes aridity in the plateau interior. 相似文献
9.
Evaluating uncertainties in regional climate simulations over South America at the seasonal scale 总被引：1，自引：0，他引：1
This work focuses on the evaluation of different sources of uncertainty affecting regional climate simulations over South America at the seasonal scale, using the MM5 model. The simulations cover a 3-month period for the austral spring season. Several four-member ensembles were performed in order to quantify the uncertainty due to: the internal variability; the definition of the regional model domain; the choice of physical parameterizations and the selection of physical parameters within a particular cumulus scheme. The uncertainty was measured by means of the spread among individual members of each ensemble during the integration period. Results show that the internal variability, triggered by differences in the initial conditions, represents the lowest level of uncertainty for every variable analyzed. The geographic distribution of the spread among ensemble members depends on the variable: for precipitation and temperature the largest spread is found over tropical South America while for the mean sea level pressure the largest spread is located over the southeastern Atlantic Ocean, where large synoptic-scale activity occurs. Using nudging techniques to ingest the boundary conditions reduces dramatically the internal variability. The uncertainty due to the domain choice displays a similar spatial pattern compared with the internal variability, except for the mean sea level pressure field, though its magnitude is larger all over the model domain for every variable. The largest spread among ensemble members is found for the ensemble in which different combinations of physical parameterizations are selected. The perturbed physics ensemble produces a level of uncertainty slightly larger than the internal variability. This study suggests that no matter what the source of uncertainty is, the geographical distribution of the spread among members of the ensembles is invariant, particularly for precipitation and temperature. 相似文献
10.
The surface radiation budget over South America in a set of regional climate models from the CLARIS-LPB project 总被引：1，自引：0，他引：1
Natalia L. Pessacg Silvina A. Solman Patrick Samuelsson Enrique Sanchez José Marengo Laurent Li Armelle Reca C. Remedio Rosmeri P. da Rocha Caroline Mourão Daniela Jacob 《Climate Dynamics》2014,43(5-6):1221-1239
The performance of seven regional climate models in simulating the radiation and heat fluxes at the surface over South America (SA) is evaluated. Sources of uncertainty and errors are identified. All simulations have been performed in the context of the CLARIS-LPB Project for the period 1990–2008 and are compared with the GEWEX-SRB, CRU, and GLDAS2 dataset and NCEP-NOAA reanalysis. Results showed that most of the models overestimate the net surface short-wave radiation over tropical SA and La Plata Basin and underestimate it over oceanic regions. Errors in the short-wave radiation are mainly associated with uncertainties in the representation of surface albedo and cloud fraction. For the net surface long-wave radiation, model biases are diverse. However, the ensemble mean showed a good agreement with the GEWEX-SRB dataset due to the compensation of individual model biases. Errors in the net surface long-wave radiation can be explained, in a large proportion, by errors in cloud fraction. For some particular models, errors in temperature also contribute to errors in the net long-wave radiation. Analysis of the annual cycle of each component of the energy budget indicates that the RCMs reproduce generally well the main characteristics of the short- and long-wave radiations in terms of timing and amplitude. However, a large spread among models over tropical SA is apparent. The annual cycle of the sensible heat flux showed a strong overestimation in comparison with the reanalysis and GLDAS2 dataset. For the latent heat flux, strong differences between the reanalysis and GLDAS2 are calculated particularly over tropical SA. 相似文献