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The thesis concerns the analysis and interpretation of data from satellite borne radar altimeters over ice covered ocean surfaces. The applications of radar altimetry are described in detail and consider monitoring global climate change, the role that sea ice plays in the climate system, operational applications and the extension of high precision surface elevation measurements into areas of sea ice. The general nature of sea ice cover is discussed and a list of requirements for sea ice monitoring is provided and the capability of different satellite sensors to satisfy needs is examined. The operation of satellite borne altimeter over non-ocean surfaces is discussed in detail. Theories of radar backscatter over sea ice are described and are used to predict the radar altimeter response to different types of sea ice cover. Methods employed for analysis of altimeter data over sea ice are also described. Data from the Seasat altimeter is examined on a regional and global scale and compared with sea ice climatology. Data from the Geosat altimeter is compared with co-incident imagery from the Advanced Very High Resolution Radiometer and also from airborne Synthetic Aperture Radar. Correlations are observed between the altimeter data and imagery for the ice edge position, zones within the ice cover, new ice and leads, vast floes and the fast ice boundary. An analysis of data collected by the Geosat altimeter over a period of more than two years is used to derive seasonal and inter-annual variations in the total Antarctic sea ice extent. In addition the retrieval of high accuracy elevation measurements over sea ice areas is carried out. These data are used to produce improved maps of sea surface topography over icecovered ocean and provide evidence of the ability of the altimeter to determine sea ice freeboard directly. In addition the changing freeboard of two giant Antarctic tabular icebergs, as measured by the Geosat altimeter, is presented. As a summary the achievements are reviewed and suggestions are made towards directions for further work on present data sets and for future data from the ERS-1 satellite.

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Orientador: Raquel Ghini / Banca: Flávia Rodrigues Alves Patrício / Banca: Antônio Carlos Maringoni / Resumo: Os níveis de concentração de CO2 atmosférico estão se elevando nas últimas décadas devido principalmente à queima de combustíveis fósseis. Essa alteração atmosférica, além de intensificar o fenômeno do efeito estufa, pode afetar o comportamento de algumas plantas e microrganismos de interesse agrícola. O CO2, por ser um componente básico da fotossíntese, em alta concentração, pode causar alterações na morfologia e nos processos fisiológicos das plantas, assim como na interação destas com fitopatógenos. Sendo assim, o presente estudo teve por objetivo avaliar o efeito da alta concentração de CO2 atmosférico na severidade do oídio, causado por Microsphaera diffusa, e da ferrugem asiática, causado por Phakopsora pachyrhizi, na soja e também em alguns fatores relacionados ao desenvolvimento da planta que podem exercer influência na doença, como o crescimento, peso da matéria seca e nodulação. Foram realizados três ensaios em estufas de topo aberto com (E+CO2) ou sem (E) injeção de CO2 e sem estufa (T), correspondendo às concentrações de, aproximadamente, 647 ppm, 474 ppm e 453 ppm, respectivamente. No primeiro ensaio, foram avaliadas características de desenvolvimento da planta; no segundo, a severidade da ferrugem asiática, que ocorreu de forma espontânea; e no terceiro, a severidade do oídio em quatro cultivares com diferentes níveis de resistência. As cultivares foram: FT-Estrela, altamente suscetível (AS); Embrapa 48, suscetível (S); FT-Cometa, moderadamente resistente (MR) e FT-5 (Formosa), resistente (R). Nos resultados obtidos, foi verificado um aumento significativo na severidade do oídio, no tratamento com injeção de CO2,em folhas primárias e na planta inteira das cultivares analisadas em conjunto, mas não houve alteração na expressão de resistência das cultivares. Para a ferrugem asiática, houve redução da severidade... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The concentration of atmospheric CO2 is increasing in recent decades, mainly due to burning of fossil fuels. This atmospheric change can intensify the phenomenon of the greenhouse effect, and can affect the behavior of important agricultural plants and microorganisms. The CO2, as a basic component of photosynthesis, in high concentrations, can cause changes in morphological and physiological processes of plants, as well as interaction with plant pathogens. Therefore, this study aimed to assess the effect of high concentrations of atmospheric CO2 on the severity of powdery mildew in soybean, caused by Microsphaera diffusa, and also in some characteristics related to the development of the plant that may influence the disease, such as growth, weight of dry matter and nodulation. Three trials were developed under open-top chambers with (E+CO2) or without (E) injection of CO2 and without greenhouse (T), with the approximate concentrations of 647 ppm, 474 ppm, and 453 ppm, respectively. On the first trial, growth characteristics were evaluated, on the second, the severity of rust, caused by Phakopsora pachyrhizi, which occurred spontaneously; on the third, the severity of powdery mildew on four cultivars with different levels of resistance: FT-Estrela, highly susceptible (AS); Embrapa 48, ...(Complete abstract click electronic access below) / Mestre

Pyrethroid insecticides applied on crops and in urban areas are being found in aquatic ecosystems due to natural processes, such as run-off. Although highly toxic to invertebrates and fish, populations of Hyalella azteca have become resistant to some of these compounds, which pose risks to not only their populations, but higher trophic level populations via bioaccumulation (in this thesis, the Inland silverside (Menidia beryllina)). Concurrently, the impact of global climate change (GCC) is impacting environmental water parameters, such as temperature and salinity. The objective of this thesis was to analyze the relationship between varying water parameters due to GCC on the fate of permethrin (a type of pyrethroid) in resistant H. azteca (by measuring toxicokinetic rates) and in M. beryllina (by measuring bioaccumulation after consuming permethrin-dosed resistant H. azteca). Permethrin bioconcentration testing used two distinct populations (Mosher Slough and Escondido Creek) of pyrethroid-resistant H. azteca and showed that temperature and salinity affected toxicokinetic rates. Statistical differences in metabolite formation rates (km) across temperatures were found between and within populations. Salinity also exhibited statistical differences in the elimination of parent compound (kep). No statistically significant differences in uptake rates (ku) were found for either population. In the M. beryllina testing, the ability for the fish to bioaccumulate permethrin via a dietary route of exposure was confirmed, contradicting previous findings. Statistically significant bioaccumulation was found across salinities, whereas no statistically significant temperature effects were observed. With the predicted increased use of pyrethroids over the course of the next century, the emergence of resistant populations of H. azteca may increase, simultaneously increasing the risk for bioaccumulation by higher trophic species. With rates of biotransformation in H. azteca affected by changing water parameters due to GCC change, the ratio of parent and metabolite compound transferred to fish will also be altered. Pyrethroid metabolites in fish act as endocrine disruptors rather than inhibit nerve function like the parent compound, which can significantly affect fish development. Overall, this thesis demonstrates important potential effects of GCC on the rates and biological transfer of pyrethroids by aquatic species, and the potential combined effects of these multiple stressors on two trophic levels of aquatic organisms.

Mangrove ecosystems are among the world's most endangered biomes; nearly one-half of the overall coverage is threatened by human activity, invasive species, and global climate change. Mangroves play an important ecosystem role through detrital production and by providing: fisheries and wildlife nursery habitat, shoreline protection, a sink for nutrients, carbon, and sediment. In addition to human activity, the Florida mangroves (Avicennia germinans, Laguncularia racemosa, and Rhizophora mangle) are being threatened by the invasive Brazilian pepper (Schinus terebinthifolius). This study was performed along a 261 km stretch of the east coast of Florida from Sebastian Inlet to the northern extent of mangroves, near St. Augustine. It entailed two parts. The first examined the phenology and leafing rates of the four species and attempted to find if there was a relationship between growth and latitude or temperature. Although a correlation between peaks in temperature and phenology was observed for all species, no leafing pattern could be discerned. In terms of mangrove growth for branch diameter, a logarithmic model (y=a + b·log [Initial diameter]) best fitted the data for R. mangle and L. racemosa but neither latitude nor temperature appeared to be important. However, S. terebinthifolius' and A. germinans's branch diameter growth were best represented by a logarithmic model (y=a + b·log [Initial diameter] + c·log x2) that incorporated temperature and latitudinal respectively. In the second part, a simulation model was developed to focus on understanding the relationships between establishment and competition among the three mangrove species and the invading S. terebinthifolius. This model was run under various invasion and/or climate change scenarios to determine possible outcomes under global climate change with or without the presence of S. terebinthifolius. Conclusions were drawn that under all scenarios of invasion, other than sea level rise as part of global climate change, S. terebinthifolius would dominate the landscape if allowed to invade and establish in areas in which it is not currently present although the amount of this response is dependent on the S. terebinthifolius response curves.

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4 pp. / This is part of a series on climate variability and forested ecosystems / Recent events in the forests of the Southwest have prompted scientists to consider the role of climate variability in insect and disease cycles. Over 70 million pine trees along with millions of other conifers died in 2002-03. Average temperature increases of 3°C enabled the MPB at those high elevations to achieve univoltine (having one generation per year) reproduction leading to previously unheard of outbreaks in white bark pine at high elevation sites in Idaho.Aspen defoliation in Arizona and New Mexico averaged ~ 20,375 acres from 1990 to 1997. A series of events has contributed to the decline of aspen since 1997.

This thesis uses geological field data and numerical ice sheet modelling to study the Younger Dryas ice cap in Scotland. The Younger Dryas stadial is important because it represents the most recent period of high-magnitude global climate change, and was marked by the expansion of ice sheets in North America and Scandinavia, and the regrowth of glaciers in the British Isles. An integrated methodology linking field results and modelling is developed and applied here, specifically focussing on the deposits, landforms, and palaeoglaciology of Younger Dryas glaciers in western Scotland. This combined approach enables data of different scales to be compared, and connected, from local sedimentological investigations and empirically derived reconstructions, to regional ice-sheet simulations from a high-resolution numerical model. Previous geological mapping in western Scotland resulted in contradictory views of the thickness and extent of ice during the Younger Dryas, consequently leading to uncertainty about the dynamics of the former ice cap. By using a ‘landsystem’ method to characterise the terrain, it is argued here that geological evidence in the study area implies a relatively thick central ice cap that fed steep outlet glaciers around its margins. These glaciers oscillated throughout the stadial, and during deglaciation produced suites of moraines that marked successive positions of glacier retreat. Widespread preservation of superimposed landforms, and of sediment sequences pre-dating the Younger Dryas, suggest that, despite being active, the Younger Dryas ice cap was not particularly erosive in its central area and only subtly modified its bed. These geological interpretations are supported by high-resolution numerical modelling of the ice cap, which reveals clear spatial variability in the velocity structure, thermal regime, and flow mechanism of the ice cap; patterns that led to local contrasts in basal processes and diversity in the geological imprint. These model experiments also highlight the non-linear relationship between climate forcing and glacier response, identifying evidence of ice sheet hysteresis and climatically decoupled glacier oscillations – concepts as relevant to geological investigations of former ice masses as they are to the prediction of glacier response under future climate changes.

Esta pesquisa avaliou a discussão científica acerca das supostas alterações climáticas globais de origem antrópica sob o embate das correntes cética e aquecimentista, evidenciando que o chamado consenso acerca do tema não existe. Tal análise serviu de base para a avaliação de alguns dos mais importantes tratados ambientais internacionais voltados à proteção climática que originaram diversas regulamentações ambientais nacionais também em função da causa climática. Essa análise, baseada nas verificações prévias, evidenciou que diversas regulamentações nacionais não se sustentam cientificamente e, dessa forma, legalmente, uma vez que partem de um pressuposto inverídico, além do fato de que estas se apresentam danosas aos países em desenvolvimento uma vez que obstam seu desenvolvimento quando apontam como caminho a ideologia ambientalista. / This research evaluated the scientific discussion about the alleged global climate change of anthropogenic origin in the clash of currents global warmers and skepticals, showing that the so-called consensus about the topic does not exist. This analysis formed the basis for the assessment of some of the most important international environmental treaties aimed at climate protection that arose several environmental regulations also due to the climate cause. This analysis, based on previous findings, showed that different national regulations do not hold up scientifically and thus legally, since they start from an assumption untrue, besides the fact that they present themselves harmful to developing countries since they prevent its development indicating the environmentalist ideology as the right path.