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Para citar este documentoRabelo da Rocha Repinaldo, C.., Müller, G. V., Martins Andrade, K.. (2017). Patrones atmosfericos simulados en el clima presente y futuro asociados al descenso de temperatura en el sudeste de Sudamerica. Boletín geográfico, 39, 13-34. ResumenLas características atmosféricas asociadas a eventos extremos fríos, identificados a partir del descenso de la temperatura en el invierno en tres regiones en el sudeste de Sudamérica, son analizadas con datos de reanálisis NCEP/NCAR y simulaciones de los modelos HadCM3 y GFDL-CM2.0 en la versión acoplada océano-atmósfera, para el clima presente y el escenario futuro más crítico A2 del CMIP3. Para las simulaciones del clima presente, el modelo que mejor representó las características observadas en el conjunto del reanálisis fue el GFDL-CM2.0, presentándose más coherente con relación a las posiciones de las altas pos frontales y de las isotermas de 0°C y 10°C. Para el futuro, el modelo GFDL-CM2.0 proyecta un debilitamiento de las anomalías negativas de temperatura y los eventos extremos de caída de temperatura con menos avance en dirección al Ecuador, mientras que, según el modelo HadCM3, la simulación para el futuro

The size partitioning of dissolved Fe (dFe<0.2 µm) into soluble (sFe<0.02 µm) and colloidal (0.02 µm < cFe < 0.2 µm) species was investigated at 28 stations along the GEOTRACES GA03 North Atlantic Transect. Upper ocean dFe size partitioning was highly variable with depth: 79±6% of aerosolderived surface dFe was maintained in the colloidal size fraction, while cFe disappeared completely at the deep chlorophyll maximum, presumably a result of preferential cFe biological uptake and/or scavenging. In the intermediate and deep ocean, however, dFe was evenly partitioned ~50:50% into sFe and cFe phases, which we hypothesize results from a "steady state" of dFe exchange reactions during and following remineralization including ligand exchange, sorption/desorption, and aggregation/disaggregation. There were only two exceptions to this constant partitioning in the intermediate/deep ocean. First, cFe dominated (82-96%) at and downstream of the Mid-Atlantic Ridge hydrothermal system. Also, along Line W between Woods Hole and Bermuda the dFe partitioning

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a b s t r a c tWith the common goal of more accurately and consistently quantifying ambient concentrations of free metal ions and natural organic ligands in aquatic ecosystems, researchers from 15 laboratories that routinely analyze trace metal speciation participated in an intercomparison of statistical methods used to model their most common type of experimental dataset, the complexometric titration. All were asked to apply statistical techniques that they were familiar with to model synthetic titration data that are typical of those obtained by applying stateof-the-art electrochemical methods -anodic stripping voltammetry (ASV) and competitive ligand equilibration-adsorptive cathodic stripping voltammetry (CLE-ACSV) -to the analysis of natural waters. Herein, we compare their estimates for parameters describing the natural ligands, examine the accuracy of inferred ambient free metal ion concentrations ([M f ]), and evaluate the influence of the various methods and assumptions used on these results. The ASV-type titrations were designed to test each participant's ability to correctly describe the natural ligands present in a sample when provided with data free of measurement error, i.e., random noise. For the three virtual samples containing just one natural ligand, all participants were able to correctly identify the number of ligand classes present and accurately estimate their parameters. For the four samples containing two or three ligand classes, a few participants detected too few or too many classes and consequently reported inaccurate 'measurements' of ambient [M f ]. Since the problematic results arose from human error rather than any specific method of analyzing the data, we recommend that analysts should make a practice of using one's parameter estimates to generate simulated (back-calculated) titration curves for comparison to the original data. The root-meansquared relative error between the fitted observations and the simulated curves should be comparable to the expected precision of the analytical method and upon visual inspection the distribution of residuals should not be skewed.Marine Chemistry 173 (2015) 3-24 BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Modeling the synthetic, CLE-ACSV-type titration dataset, which comprises 5 titration curves generated at different analytical windows or levels of competing ligand added to the virtual sample, proved to be more challenging due to the random measurement error that was incorporated. Comparison of the submitted results was complicated by the participants' differing interpretations of their task. Most adopted the provided 'true' instrumental sensitivity in modeling the CLE-ACSV curves, but several estimated sensitivities using internal calibration, exactly as is required for actual samples. Since most fitted sensitivities were biased low, systematic error in inferred ambient [M f ] and in estimated weak ligand (L 2 ) concentrations resulted. The main distinction between the mathematical approaches taken by participants lie...

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One contribution of 20 to a discussion meeting issue 'Biological and climatic impacts of ocean trace element chemistry'.

Pb is a trace metal that tracks anthropogenic pollution in natural environments. Despite recent leaded petrol phase out around Southeast Asia, the region's growth has resulted in continued exposure of Pb from a variety of sources. In this study, sources of Pb into Singapore, a highly urbanised city-state situated in the central axis of Southeast Asia, are investigated using isotopic ratios and concentrations. We compiled data from our previous analyses of aerosols, incineration fly ash and sediments, with new data from analyses of soil from gas stations, water from runoff and round-island coastal seawater to obtain a spatio-temporal overview of sources of Pb into the Singapore environment. Using Pb/Pb ratio, we identified three main Pb source origins: natural Pb (1.215 ± 0.001), historic/remnant leaded petrol (1.123 ± 0.013), and present-day industrial and incinerated waste (1.148 ± 0.005). Deep reservoir sediments bore larger traces of Pb from leaded petrol, but present-day runoff waters and coastal seawater were a mix of industrial and natural sources with somewhat variable concentrations. We found temporal variability in Pb isotopic ratio in aerosols indicating alternating transboundary Pb sources to Singapore that correspond to seasonal changes in monsoon winds. By contrast, seasonal monsoon circulation did not significantly influence isotopic ratios of coastal seawater Pb. Instead, seawater Pb was driven more by location differences, suggesting stronger local-scale drivers of Pb such as point sources, water flushing, and isotope exchange. The combination of multiple historic and current sources of Pb shown in this study highlights the need for continued monitoring of Pb in Southeast Asia, especially in light of emerging industries and potential large sources of Pb such as coal combustion.