Desarrollo y validación de tecnologías de intensificación lumínica para fotobiorreactores (FBR) para el aprovechamiento de la radiación en el cultivo de microalgas

En la actualidad la humanidad se enfrenta a una serie de problemas de gran transcendencia que van a determinar en alto grado los niveles de calidad de vida en los próximos años. El calentamiento global, el incremento demográfico incontrolado, la contaminación ambiental y la escasez de recursos así como una mala distribución de los mismos, son sólo algunos ejemplos. En este contexto, las microalgas, microrganismos fotosintéticos de alta eficiencia y versatilidad, presentan una serie de características que las convierten a priori en la base de una tecnología con un enorme potencial para formar parte de la solución a estos graves problemas planteados. Uno de los principales factores que impiden una mayor implantación de la tecnología de microalgas es de tipo económico. La baja productividad por unidad de área de los sistemas de cultivo actuales y la alta inversión necesaria en equipos y mantenimiento, hace que solo se justifique el cultivo de productos de muy alto valor añadido. Las soluciones pasan por aumentar el rendimiento global de los cultivos y por disminuir los costes de equipos e instalaciones. La presente tesis investiga sobre la posibilidad de conseguir un mejor aprovechamiento de la luz solar incidente sobre un cultivo de microalgas mediante el uso de una serie de dispositivos ópticos que vienen a denominarse intensificadores lumínicos. De entre los factores que determinan la productividad de un campo de cultivo de microalgas, posiblemente el más determinante sea la cantidad de radiación que las microalgas pueden aprovechar. Los intensificadores aumentan la disponibilidad de luz en el interior de los tubos de cultivo, de forma que la fotosíntesis se vea favorecida y, de este modo, se incremente la tasa de crecimiento de las microalgas. En el desarrollo de la tesis se proponen tres tipologías diferentes de intensificador diseñadas en base a criterios óptico-geométricos. Para cada una de estas tipologías se evalúa el incremento de radiación que se lograría sobre un tubo de cultivo. Paralelamente se desarrolla un modelo que permite la evaluación de la productividad del cultivo. Esto permite añadir el factor biológico al puramente óptico-físico y valorar las distintas propuestas de intensificadores en función de las características propias del microalga utilizada en el cultivo. El modelo es verificado y contrastado frente a datos de producción obtenidos en la bibliografía. Finalmente, la exposición concluye con una presentación general de las futuras líneas de investigación. ABSTRACT Today, humanity is facing a series of problems of global significance that will determine the standard of living in the years ahead. Global warming, uncontrolled population growth, pollution, lack of resources and poor distribution of them are just an example of the challenges we are facing. In this context, microalgae, high efficient photosynthetic microorganisms, have a number of characteristics that turn them into a very promising technology that can contribute or be part of a sustainable solution. One of the main factors preventing the adoption of microalgae technology is economical. The low productivity per unit area of current farming systems and the high investment needed in equipment and maintenance, only justifies the cultivation of algae for high value applications. One solution could be increasing the overall yield of the crops and reduce the equipment and facilities costs. Among the factors that determine the productivity of a microalgae culture, possibly the most influential one is the amount of radiation that microalgae receive. This Thesis develops the possibility of making better use of the sunlight radiation incident on a crop field using a series of devices similar to solar collectors. The solar collectors proposed are intended to increase the availability of light inside the culture tubes and within it, the tax of photosynthesis and the overall growth rate of the microalgae. In this research, three different configurations of collectors are designed, based on optical and geometrical criteria. For each one of these collectors, the increase on radiation that would be expected is evaluated. Furthermore, a model for light distribution inside the culture is developed in terms to estimate the biomass productivity. This allows adding the biological factor to purely optical-physical considerations and to assess the different solar collectors proposed, in terms specific for the microalgae. The model is tested against production data obtained in different scientific literature. Finally, the exposition concludes with some guidelines for future research.

Estimate of the total ice volume of Svalbard glaciers and their potential contribution to sea-level rise = Estimación del volumen de hielo de Svalbard y su contribución potencial a la subida del nivel del mar

El objetivo final de las investigaciones recogidas en esta tesis doctoral es la estimación del volumen de hielo total de los ms de 1600 glaciares de Svalbard, en el Ártico, y, con ello, su contribución potencial a la subida del nivel medio del mar en un escenario de calentamiento global. Los cálculos más exactos del volumen de un glaciar se efectúan a partir de medidas del espesor de hielo obtenidas con georradar. Sin embargo, estas medidas no son viables para conjuntos grandes de glaciares, debido al coste, dificultades logísticas y tiempo requerido por ellas, especialmente en las regiones polares o de montaña. Frente a ello, la determinación de áreas de glaciares a partir de imágenes de satélite sí es viable a escalas global y regional, por lo que las relaciones de escala volumen-área constituyen el mecanismo más adecuado para las estimaciones de volúmenes globales y regionales, como las realizadas para Svalbard en esta tesis. Como parte del trabajo de tesis, hemos elaborado un inventario de los glaciares de Svalbard en los que se han efectuado radioecosondeos, y hemos realizado los cálculos del volumen de hielo de más de 80 cuencas glaciares de Svalbard a partir de datos de georradar. Estos volúmenes han sido utilizados para calibrar las relaciones volumen-área desarrolladas en la tesis. Los datos de georradar han sido obtenidos en diversas campañas llevadas a cabo por grupos de investigación internacionales, gran parte de ellas lideradas por el Grupo de Simulación Numérica en Ciencias e Ingeniería de la Universidad Politécnica de Madrid, del que forman parte la doctoranda y los directores de tesis. Además, se ha desarrollado una metodología para la estimación del error en el cálculo de volumen, que aporta una novedosa técnica de cálculo del error de interpolación para conjuntos de datos del tipo de los obtenidos con perfiles de georradar, que presentan distribuciones espaciales con unos patrones muy característicos pero con una densidad de datos muy irregular. Hemos obtenido en este trabajo de tesis relaciones de escala específicas para los glaciares de Svalbard, explorando la sensibilidad de los parámetros a diferentes morfologías glaciares, e incorporando nuevas variables. En particular, hemos efectuado experimentos orientados a verificar si las relaciones de escala obtenidas caracterizando los glaciares individuales por su tamaño, pendiente o forma implican diferencias significativas en el volumen total estimado para los glaciares de Svalbard, y si esta partición implica algún patrón significativo en los parámetros de las relaciones de escala. Nuestros resultados indican que, para un valor constante del factor multiplicativo de la relacin de escala, el exponente que afecta al área en la relación volumen-área decrece según aumentan la pendiente y el factor de forma, mientras que las clasificaciones basadas en tamaño no muestran un patrón significativo. Esto significa que los glaciares con mayores pendientes y de tipo circo son menos sensibles a los cambios de área. Además, los volúmenes de la población total de los glaciares de Svalbard calculados con fraccionamiento en grupos por tamaño y pendiente son un 1-4% menores que los obtenidas usando la totalidad de glaciares sin fraccionamiento en grupos, mientras que los volúmenes calculados fraccionando por forma son un 3-5% mayores. También realizamos experimentos multivariable para obtener estimaciones óptimas del volumen total mediante una combinación de distintos predictores. Nuestros resultados muestran que un modelo potencial simple volumen-área explica el 98.6% de la varianza. Sólo el predictor longitud del glaciar proporciona significación estadística cuando se usa además del área del glaciar, aunque el coeficiente de determinación disminuye en comparación con el modelo más simple V-A. El predictor intervalo de altitud no proporciona información adicional cuando se usa además del área del glaciar. Nuestras estimaciones del volumen de la totalidad de glaciares de Svalbard usando las diferentes relaciones de escala obtenidas en esta tesis oscilan entre 6890 y 8106 km3, con errores relativos del orden de 6.6-8.1%. El valor medio de nuestras estimaciones, que puede ser considerado como nuestra mejor estimación del volumen, es de 7.504 km3. En términos de equivalente en nivel del mar (SLE), nuestras estimaciones corresponden a una subida potencial del nivel del mar de 17-20 mm SLE, promediando 19_2 mm SLE, donde el error corresponde al error en volumen antes indicado. En comparación, las estimaciones usando las relaciones V-A de otros autores son de 13-26 mm SLE, promediando 20 _ 2 mm SLE, donde el error representa la desviación estándar de las distintas estimaciones. ABSTRACT The final aim of the research involved in this doctoral thesis is the estimation of the total ice volume of the more than 1600 glaciers of Svalbard, in the Arctic region, and thus their potential contribution to sea-level rise under a global warming scenario. The most accurate calculations of glacier volumes are those based on ice-thicknesses measured by groundpenetrating radar (GPR). However, such measurements are not viable for very large sets of glaciers, due to their cost, logistic difficulties and time requirements, especially in polar or mountain regions. On the contrary, the calculation of glacier areas from satellite images is perfectly viable at global and regional scales, so the volume-area scaling relationships are the most useful tool to determine glacier volumes at global and regional scales, as done for Svalbard in this PhD thesis. As part of the PhD work, we have compiled an inventory of the radio-echo sounded glaciers in Svalbard, and we have performed the volume calculations for more than 80 glacier basins in Svalbard from GPR data. These volumes have been used to calibrate the volume-area relationships derived in this dissertation. Such GPR data have been obtained during fieldwork campaigns carried out by international teams, often lead by the Group of Numerical Simulation in Science and Engineering of the Technical University of Madrid, to which the PhD candidate and her supervisors belong. Furthermore, we have developed a methodology to estimate the error in the volume calculation, which includes a novel technique to calculate the interpolation error for data sets of the type produced by GPR profiling, which show very characteristic data distribution patterns but with very irregular data density. We have derived in this dissertation scaling relationships specific for Svalbard glaciers, exploring the sensitivity of the scaling parameters to different glacier morphologies and adding new variables. In particular, we did experiments aimed to verify whether scaling relationships obtained through characterization of individual glacier shape, slope and size imply significant differences in the estimated volume of the total population of Svalbard glaciers, and whether this partitioning implies any noticeable pattern in the scaling relationship parameters. Our results indicate that, for a fixed value of the factor in the scaling relationship, the exponent of the area in the volume-area relationship decreases as slope and shape increase, whereas size-based classifications do not reveal any clear trend. This means that steep slopes and cirque-type glaciers are less sensitive to changes in glacier area. Moreover, the volumes of the total population of Svalbard glaciers calculated according to partitioning in subgroups by size and slope are smaller (by 1-4%) than that obtained considering all glaciers without partitioning into subgroups, whereas the volumes calculated according to partitioning in subgroups by shape are 3-5% larger. We also did multivariate experiments attempting to optimally predict the volume of Svalbard glaciers from a combination of different predictors. Our results show that a simple power-type V-A model explains 98.6% of the variance. Only the predictor glacier length provides statistical significance when used in addition to the predictor glacier area, though the coefficient of determination decreases as compared with the simpler V-A model. The predictor elevation range did not provide any additional information when used in addition to glacier area. Our estimates of the volume of the entire population of Svalbard glaciers using the different scaling relationships that we have derived along this thesis range within 6890-8106 km3, with estimated relative errors in total volume of the order of 6.6-8.1% The average value of all of our estimates, which could be used as a best estimate for the volume, is 7,504 km3. In terms of sea-level equivalent (SLE), our volume estimates correspond to a potential contribution to sea-level rise within 17-20 mm SLE, averaging 19 _ 2 mm SLE, where the quoted error corresponds to our estimated relative error in volume. For comparison, the estimates using the V-A scaling relations found in the literature range within 13-26 mm SLE, averaging 20 _ 2 mm SLE, where the quoted error represents the standard deviation of the different estimates.

Mejora de los modelos térmicos de las presas bóveda en explotación : aplicación al análisis del efecto del cambio climático

Las cargas de origen térmico causadas por las acciones medioambientales generan esfuerzos apreciables en estructuras hiperestáticas masivas, como es el caso de las presas bóvedas. Ciertas investigaciones apuntan que la variación de la temperatura ambiental es la segunda causa de reparaciones en las presas del hormigón en servicio. Del mismo modo, es una causa de fisuración en un porcentaje apreciable de casos. Las presas son infraestructuras singulares por sus dimensiones, su vida útil, su impacto sobre el territorio y por el riesgo que implica su presencia. La evaluación de ese riesgo requiere, entre otras herramientas, de modelos matemáticos de predicción del comportamiento. Los modelos han de reproducir la realidad del modo más fidedigno posible. Además, en un escenario de posible cambio climático en el que se prevé un aumento de las temperaturas medias, la sociedad ha de conocer cuál será el comportamiento estructural de las infraestructuras sensibles en los futuros escenarios climáticos. No obstante, existen escasos estudios enfocados a determinar el campo de temperaturas de las presas de hormigón. Así, en esta investigación se han mejorado los modelos de cálculo térmico existentes con la incorporación de nuevos fenómenos físicos de transferencia de calor entre la estructura y el medio ambiente que la rodea. También se han propuesto nuevas metodologías más eficientes para cuantificar otros mecanismos de transferencia de calor. La nueva metodología se ha aplicado a un caso de estudio donde se disponía de un amplio registro de temperaturas de su hormigón. Se ha comprobado la calidad de las predicciones realizadas por los diversos modelos térmicos en el caso piloto. También se han comparado los resultados de los diversos modelos entre sí. Finalmente, se ha determinado las consecuencias de las predicciones de las temperaturas por algunos de los modelos térmicos sobre la respuesta estructural del caso de estudio. Los modelos térmicos se han empleado para caracterizar térmicamente las presas bóveda. Se ha estudiado el efecto de ciertas variables atmosféricas y determinados aspectos geométricos de las presas sobre su respuesta térmica. También se ha propuesto una metodología para evaluar la respuesta térmica y estructural de las infraestructuras frente a los posibles cambios meteorológicos inducidos por el cambio climático. La metodología se ha aplicado a un caso de estudio, una presa bóveda, y se ha obtenido su futura respuesta térmica y estructural frente a diversos escenarios climáticos. Frente a este posible cambio de las variables meteorológicas, se han detallado diversas medidas de adaptación y se ha propuesto una modificación de la normativa española de proyecto de presas en el punto acerca del cálculo de la distribución de temperaturas de diseño. Finalmente, se han extraído una serie de conclusiones y se han sugerido posibles futuras líneas de investigación para ampliar el conocimiento del fenómeno de la distribución de temperaturas en el interior de las presas y las consecuencias sobre su respuesta estructural. También se han propuesto futuras investigaciones para desarrollar nuevos procedimiento para definir las cargas térmicas de diseño, así como posibles medidas de adaptación frente al cambio climático. Thermal loads produced by external temperature variations may cause stresses in massive hyperstatic structures, such as arch dams. External temperature changes are pointed out as the second most major repairs in dams during operation. Moreover, cracking is caused by thermal loads in a quite number of cases. Dams are unique infrastructures given their dimensions, lifetime, spatial impacts and the risks involve by their presence. The risks are assessed by means of mathematical models which compute the behavior of the structure. The behavior has to be reproduced as reliable as possible. Moreover, since mean temperature on Earth is expected to increase, society has to know the structural behavior of sensitive structures to climate change. However, few studies have addressed the assessment of the thermal field in concrete dams. Thermal models are improved in this research. New heat transfer phenomena have been accounted for. Moreover, new and more efficient methodologies for computing other heat transfer phenomena have been proposed. The methodology has been applied to a case study where observations from thermometers embedded in the concrete were available. Recorded data were predicted by several thermal models and the quality of the predictions was assessed. Furthermore, predictions were compared between them. Finally, the consequences on the stress calculations were analyzed. Thermal models have been used to characterize arch dams from a thermal point of view. The effect of some meteorological and geometrical variables on the thermal response of the dam has been analyzed. Moreover, a methodology for assessing the impacts of global warming on the thermal and structural behavior of infrastructures has been proposed. The methodology was applied to a case study, an arch dam, and its thermal and structural response to several future climatic scenarios was computed. In addition, several adaptation strategies has been outlined and a new formulation for computing design thermal loads in concrete dams has been proposed. Finally, some conclusions have been reported and some future research works have been outlined. Future research works will increase the knowledge of the concrete thermal field and its consequences on the structural response of the infrastructures. Moreover, research works will develope a new procedure for computing the design thermal loads and will study some adaptation strategies against the climate change.

Loss of speciation rate will impoverish future diversity

Human activities have greatly reduced the amount of the earth's area available to wild species. As the area they have left declines, so will their rates of speciation. This loss of speciation will occur for two reasons: species with larger geographical ranges speciate faster; and loss of area drives up extinction rates, thus reducing the number of species available for speciation. Theory predicts steady states in species diversity, and fossils suggest that these have typified life for most of the past 500 million years. Modern and fossil evidence indicates that, at the scale of the whole earth and its major biogeographical provinces, those steady states respond linearly, or nearly so, to available area. Hence, a loss of x% of area will produce a loss of about x% of species. Local samples of habitats merely echo the diversity available in the whole province of which they are a part. So, conservation tactics that rely on remnant patches to preserve diversity cannot succeed for long. Instead, diversity will decay to a depauperate steady state in two phases. The first will involve deterministic extinctions, reflecting the loss of all areas in which a species can ordinarily sustain its demographics. The second will be stochastic, reflecting accidents brought on by global warming, new diseases, and commingling the species of the separate bio-provinces. A new kind of conservation effort, reconciliation ecology, can avoid this decay. Reconciliation ecology discovers how to modify and diversify anthropogenic habitats so that they harbor a wide variety of species. It develops management techniques that allow humans to share their geographical range with wild species.

Nitrogen management and the future of food: Lessons from the management of energy and carbon

The food system dominates anthropogenic disruption of the nitrogen cycle by generating excess fixed nitrogen. Excess fixed nitrogen, in various guises, augments the greenhouse effect, diminishes stratospheric ozone, promotes smog, contaminates drinking water, acidifies rain, eutrophies bays and estuaries, and stresses ecosystems. Yet, to date, regulatory efforts to limit these disruptions largely ignore the food system. There are many parallels between food and energy. Food is to nitrogen as energy is to carbon. Nitrogen fertilizer is analogous to fossil fuel. Organic agriculture and agricultural biotechnology play roles analogous to renewable energy and nuclear power in political discourse. Nutrition research resembles energy end-use analysis. Meat is the electricity of food. As the agriculture and food system evolves to contain its impacts on the nitrogen cycle, several lessons can be extracted from energy and carbon: (i) set the goal of ecosystem stabilization; (ii) search the entire production and consumption system (grain, livestock, food distribution, and diet) for opportunities to improve efficiency; (iii) implement cap-and-trade systems for fixed nitrogen; (iv) expand research at the intersection of agriculture and ecology, and (v) focus on the food choices of the prosperous. There are important nitrogen-carbon links. The global increase in fixed nitrogen may be fertilizing the Earth, transferring significant amounts of carbon from the atmosphere to the biosphere, and mitigating global warming. A modern biofuels industry someday may produce biofuels from crop residues or dedicated energy crops, reducing the rate of fossil fuel use, while losses of nitrogen and other nutrients are minimized.

Isobutane Alkylation Process Synthesis by means of Hybrid Simulation-Multiobjective Optimization

Multiobjective Generalized Disjunctive Programming (MO-GDP) optimization has been used for the synthesis of an important industrial process, isobutane alkylation. The two objective functions to be simultaneously optimized are the environmental impact, determined by means of LCA (Life Cycle Assessment), and the economic potential of the process. The main reason for including the minimization of the environmental impact in the optimization process is the widespread environmental concern by the general public. For the resolution of the problem we employed a hybrid simulation- optimization methodology, i.e., the superstructure of the process was developed directly in a chemical process simulator connected to a state of the art optimizer. The model was formulated as a GDP and solved using a logic algorithm that avoids the reformulation as MINLP -Mixed Integer Non Linear Programming-. Our research gave us Pareto curves compounded by three different configurations where the LCA has been assessed by two different parameters: global warming potential and ecoindicator-99.

Potential Future Coral Habitats Around Japan Depend Strongly on Anthropogenic CO2 Emissions

Using the results from the NCAR CSM1.4-coupled global carbon cycle– climate model under the Intergovernmental Panel on Climate Change (IPCC) emission scenarios SRES A2 and B1, we estimated the effects of both global warming and ocean acidification on the future habitats of corals in the seas around Japan during this century. As shown by Yara et al. (Biogeosciences 9:4955–4968,2012), under the high-CO₂-emission scenario (SRES A2), coral habitats will be sandwiched and narrowed between the northern region, where the saturation state of the carbonate mineral aragonite (Ωarag) decreases, and the southern region, where coral bleaching occurs. We found that under the low-emission scenario SRES B1, the coral habitats will also shrink in the northern region by the reduced Ωarag but to a lesser extent than under SRES A2, and in contrast to SRES A2, no bleaching will occur in the southern region. Therefore, coral habitats in the southern region are expected to be largely unaffected by ocean acidification or surface warming under the low-emission scenario. Our results show that potential future coral habitats depend strongly on CO₂ emissions and emphasize the importance of reducing CO₂ emissions to prevent negative impacts on coral habitats.

Engineering model of future motor vehicles. Volume I. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Engineering model of future motor vehicles. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Evaluation of climate change scenarios based on aquatic food web modelling

In the years 2004 and 2005 we collected samples of phytoplankton, zooplankton and macroinvertebrates in an artificial small pond in Budapest. We set up a simulation model predicting the abundance of the cyclopoids, Eudiaptomus zachariasi and Ischnura pumilio by considering only temperature as it affects the abundance of population of the previous day. Phytoplankton abundance was simulated by considering not only temperature, but the abundance of the three mentioned groups. This discrete-deterministic model could generate similar patterns like the observed one and testing it on historical data was successful. However, because the model was overpredicting the abundances of Ischnura pumilio and Cyclopoida at the end of the year, these results were not considered. Running the model with the data series of climate change scenarios, we had an opportunity to predict the individual numbers for the period around 2050. If the model is run with the data series of the two scenarios UKHI and UKLO, which predict drastic global warming, then we can observe a decrease in abundance and shift in the date of the maximum abundance occurring (excluding Ischnura pumilio, where the maximum abundance increases and it occurs later), whereas under unchanged climatic conditions (BASE scenario) the change in abundance is negligible. According to the scenarios GFDL 2535, GFDL 5564 and UKTR, a transition could be noticed.

High natural gene expression variation in the reef-building coral Acropora millepora: potential for acclimative and adaptive plasticity

Background: Ecosystems worldwide are suffering the consequences of anthropogenic impact. The diverse ecosystem of coral reefs, for example, are globally threatened by increases in sea surface temperatures due to global warming. Studies to date have focused on determining genetic diversity, the sequence variability of genes in a species, as a proxy to estimate and predict the potential adaptive response of coral populations to environmental changes linked to climate changes. However, the examination of natural gene expression variation has received less attention. This variation has been implicated as an important factor in evolutionary processes, upon which natural selection can act. Results: We acclimatized coral nubbins from six colonies of the reef-building coral Acropora millepora to a common garden in Heron Island (Great Barrier Reef, GBR) for a period of four weeks to remove any site-specific environmental effects on the physiology of the coral nubbins. By using a cDNA microarray platform, we detected a high level of gene expression variation, with 17% (488) of the unigenes differentially expressed across coral nubbins of the six colonies (jsFDR-corrected, p < 0.01). Among the main categories of biological processes found differentially expressed were transport, translation, response to stimulus, oxidation-reduction processes, and apoptosis. We found that the transcriptional profiles did not correspond to the genotype of the colony characterized using either an intron of the carbonic anhydrase gene or microsatellite loci markers. Conclusion: Our results provide evidence of the high inter-colony variation in A. millepora at the transcriptomic level grown under a common garden and without a correspondence with genotypic identity. This finding brings to our attention the importance of taking into account natural variation between reef corals when assessing experimental gene expression differences. The high transcriptional variation detected in this study is interpreted and discussed within the context of adaptive potential and phenotypic plasticity of reef corals. Whether this variation will allow coral reefs to survive to current challenges remains unknown.

Factors Affecting Current and Future Treeline Locations and Dynamics in the Peruvian Andes

The elevational distributions of tropical treelines are thought to be determined by temperature, and are predicted to shift upslope in response to global warming. In contrast to this hypothesis, global-scale studies have shown that only half of all studied treelines are shifting upslope. Understanding how treelines will respond to climate change has important implications for global biodiversity, especially in the tropics, because tropical treelines generally represent the upper-elevation distribution limit of the hyper-diverse cloudforest ecosystem. In Chapter 1, I introduce the idea that grasslands found above tropical treelines may represent a potential grass ceiling which forest species cannot cross or invade. I use an extensive literature review to outline potential mechanisms which may be acting to stabilize treeline and prevent forest expansion into high-elevation grasslands. In Chapters 2-4, I begin to explore these potential mechanisms through the use of observational and experimental methods. In Chapter 2, I show that there are significant numbers of seedlings occurring just outside of the treeline in the open grasslands and that seed rain is unlikely to limit seedling recruitment above treeline. I also show that microclimates outside of the closed-canopy cloudforest are highly variable and that mean temperatures are likely a poor explanation of tropical treeline elevations. In Chapter 3, I show that juvenile trees maintain freezing resistances similar to adults, but nighttime radiative cooling near the ground in the open grassland results in lower cold temperatures relative to the free atmosphere, exposing seedlings of some species growing above treeline to lethal frost events. In Chapter 4, I use a large-scale seedling transplant experiment to test the effects of mean temperature, absolute low temperature and shade on transplanted seedling survival. I find that increasing mean temperature negatively affects seedling survival of two treeline species while benefiting another. In addition, low temperature extremes and the presence of shade also appear to be important factors affecting seedling survival above tropical treelines. This work demonstrates that mean temperature is a poor predictor of tropical treelines and that temperature extremes, especially low temperatures, and non-climatic variables should be included in predictions of current and future tropical treeline dynamics.

Física do meio ambiente como disciplina nas licenciaturas em física: proposta de uma unidade didática para ensinar efeito estufa e aquecimento global

In this dissertation we propose a Teaching Unit of Physics to teach content through environmental discussions of the greenhouse effect and global warming. This teaching unit is based on a problem-methodological intervention from the application of the method of the Arch of Charles Maguerez. The methodological foundations of the thesis are embedded in action research and this is structured in five chapters: the first chapter deals with the Physical Environment (FMA) as a subject in Degree Courses in Physics in Brazil, bringing the concern of how this discipline has been taught. We started the first chapter explaining the reasons behind the inclusion of the discipline of Physical Environment in a Physics Degree Courses. Then we did a search on the websites of Institutions of Higher Education, to know of the existence or not of this discipline on curricular. We then analyzed the menus to see what bibliographies are being adopted and what content of Physics are being worked, and how it has been done. The courses surveyed were those of Federal and Federal Institutes Universities. Thus ended the first chapter. Given the inseparability between studies in Physics Teaching and studies on competencies, skills and significant learning, wrote the second chapter. In this chapter we discuss the challenge of converting information into knowledge. Initially on initial teacher training, because even if this is not our focus, the study is a discipline on the upper reaches, therefore, offered to future teachers. Then we talked about the culture of knowledge, where we emphasize the use of a teaching approach that promotes meanings taught by content and make sense to the student. We finished the third chapter, making some considerations on skills and abilities, in order to identify what skills and competencies were developed and worked during and after the implementation of Curriculum Unit. The third chapter is the result of a literature review and study of the radioactive EarthSun interaction. The subjects researched approach from the generation of energy in the sun to topics stain solar coronal mass ejections, solar wind, black body radiation, Wien displacement law, Stefan-Boltzmann Law, greenhouse effect and global warming. This chapter deals with material support for the teacher of the aforementioned discipline. The fourth chapter talks about the arc method of Charles Maguerez; Here we explain the structure of each of the five steps of the Arc and how to use them in teaching. We also show another version of this method adapted by Bordenave. In the fifth and final chapter brought a description of how the method of Arc was used in physics classes of Environment, with students majoring in Physics IFRN Campus Santa Cruz. Here, in this chapter, a transcript of classes to show how was the application of a problem-based methodology in the teaching of content proposed for Physics Teaching Unit from the environmental discussion about the greenhouse effect and global warming phenomena

Estimation of sea surface temperatures and salinity of ODP Site 177-1089 (Appendix A)

ODP Site 1089 is optimally located in order to monitor the occurrence of maxima in Agulhas heat and salt spillage from the Indian to the Atlantic Ocean. Radiolarian-based paleotemperature transfer functions allowed to reconstruct the climatic history for the last 450 kyr at this location. A warm sea surface temperature anomaly during Marine Isotope Stage (MIS) 10 was recognized and traced to other oceanic records along the surface branch of the global thermohaline (THC) circulation system, and is particularly marked at locations where a strong interaction between oceanic and atmospheric overturning cells and fronts occurs. This anomaly is absent in the Vostok ice core deuterium, and in oceanic records from the Antarctic Zone. However, it is present in the deuterium excess record from the Vostok ice core, interpreted as reflecting the temperature at the moisture source site for the snow precipitated at Vostok Station. As atmospheric models predict a subtropical Indian source for such moisture, this provides the necessary teleconnection between East Antarctica and ODP Site 1089, as the subtropical Indian is also the source area of the Agulhas Current, the main climate agent at our study location. The presence of the MIS 10 anomaly in the delta13C foraminiferal records from the same core supports its connection to oceanic mechanisms, linking stronger Agulhas spillover intensity to increased productivity in the study area. We suggest, in analogy to modern oceanographic observations, this to be a consequence of a shallow nutricline, induced by eddy mixing and baroclinic tide generation, which are in turn connected to the flow geometry, and intensity, of the Agulhas Current as it flows past the Agulhas Bank. We interpret the intensified inflow of Agulhas Current to the South Atlantic as responding to the switch between lower and higher amplitude in the insolation forcing in the Agulhas Current source area. This would result in higher SSTs in the Cape Basin during the glacial MIS 10, due to the release into the South Atlantic of the heat previously accumulating in the subtropical and equatorial Indian and Pacific Ocean. If our explanation for the MIS 10 anomaly in terms of an insolation variability switch is correct, we might expect that a future Agulhas SSST anomaly event will further delay the onset of next glacial age. In fact, the insolation forcing conditions for the Holocene (the current interglacial) are very similar to those present during MIS 11 (the interglacial preceding MIS 10), as both periods are characterized by a low insolation variability for the Agulhas Current source area. Natural climatic variability will force the Earth system in the same direction as the anthropogenic global warming trend, and will thus lead to even warmer than expected global temperatures in the near future.

(Table S1) Chronostratigraphic constrains for sediment core AND1-1B

Thirty years after oxygen isotope records from microfossils deposited in ocean sediments confirmed the hypothesis that variations in the Earth's orbital geometry control the ice ages (Hays et al., 1976, doi:10.1126/science.194.4270.1121), fundamental questions remain over the response of the Antarctic ice sheets to orbital cycles (Raymo and Huybers, 2008, doi:10.1038/nature06589). Furthermore, an understanding of the behaviour of the marine-based West Antarctic ice sheet (WAIS) during the 'warmer-than-present' early-Pliocene epoch (~5-3 Myr ago) is needed to better constrain the possible range of ice-sheet behaviour in the context of future global warming (Solomon et al., 2007). Here we present a marine glacial record from the upper 600 m of the AND-1B sediment core recovered from beneath the northwest part of the Ross ice shelf by the ANDRILL programme and demonstrate well-dated, ~40-kyr cyclic variations in ice-sheet extent linked to cycles in insolation influenced by changes in the Earth's axial tilt (obliquity) during the Pliocene. Our data provide direct evidence for orbitally induced oscillations in the WAIS, which periodically collapsed, resulting in a switch from grounded ice, or ice shelves, to open waters in the Ross embayment when planetary temperatures were up to ~3° C warmer than today ( Kim and Crowley, 2000, doi:10.1029/1999PA000459) and atmospheric CO2 concentration was as high as ~400 p.p.m.v. (van der Burgh et al., 1993, doi:10.1126/science.260.5115.1788, Raymo et al., 1996, doi:10.1016/0377-8398(95)00048-8). The evidence is consistent with a new ice-sheet/ice-shelf model (Pollard and DeConto, 2009, doi:10.1038/nature07809) that simulates fluctuations in Antarctic ice volume of up to +7 m in equivalent sea level associated with the loss of the WAIS and up to +3 m in equivalent sea level from the East Antarctic ice sheet, in response to ocean-induced melting paced by obliquity. During interglacial times, diatomaceous sediments indicate high surface-water productivity, minimal summer sea ice and air temperatures above freezing, suggesting an additional influence of surface melt (Huybers, 2006, doi:10.1126/science.1125249) under conditions of elevated CO2.