A influência dos gases estufa no oceano Atlântico Sul: estudo climatológico

The purpose of this study is to analyze the impact of the increase in greenhouse gases caused by the industrialization in the climate of the South Atlantic Ocean. We used the National Center for Atmospheric Research - Community Climate System Model. Two climate conditions were used to force the model, one relative to the pre-industrial levels of greenhouse gases emissions and the other to the levels of the present days. The results have shown a significant sea surface warming in pos-industrial climatology in relation to the pre-industrial one, mainly during the spring season when it reaches 2.5°C south of South America. The climatological behavior of the barotropic streamfunction and the sea level pressure also showed relevant differences from one period to the next. This suggests an intensification of the subtropical high, the subtropical gyre and the Antarctic Circumpolar Current. Seasonally, the differences in the barotropic streamfunction were larger in autumn with values as high as 25 Sv around 0°E, 55°S. The sea level pressure for present simulation shows a straightening in summer and autumn with an intensification of 2mbar, and a weakening in winter in relation to the pre-industrial period.O presente trabalho tem como objetivo analisar os impactos climáticos no oceano Atlântico Sul causados pela industrialização e conseqüente aumento da emissão de gases estufa para a atmosfera. Para isso utilizou-se o modelo numérico acoplado National Center for Atmospheric Research - Community Climate System Model, sob duas condições climáticas: a primeira para o período pré-industrial e, a segunda, para o pós-industrial. Os resultados mostraram aquecimento da superfície do mar na climatologia do período pós-industrial em relação ao pré-industrial, principalmente durante a primavera quando alcança 2,5°C ao sul do continente sulamericano. O comportamento climatológico do transporte barotrópico e da pressão ao nível do mar também mostraram diferenças significativas de um período para o outro, sugerindo a intensificação da Alta Subtropical, Giro Subtropical e Corrente Circumpolar Antártica. Sazonalmente, as diferenças no transporte barotrópico foram maiores no outono, exibindo valores superiores a 25 Sv, em torno de 0°E, 55°S. A pressão atmosférica ao nível do mar foi levemente fortalecida no verão e outono, com intensificação máxima de 2mbar, e enfraquecida no inverno do período pré-industrial para a simulação do presente

Revisiting remote drivers of the 2014 drought in South-Eastern Brazil

South-Eastern Brazil experienced a devastating drought associated with significant agricultural losses in austral summer 2014. The drought was linked to the development of a quasi-stationary anticyclone in the South Atlantic in early 2014 that affected local precipitation patterns over South-East Brazil. Previous studies have suggested that the unusual blocking was triggered by tropical Pacific sea surface temperature (SST) anomalies and, more recently, by convection over the Indian Ocean related to the Madden-Julian Oscillation. Further investigation of the proposed teleconnections appears crucial for anticipating future economic impacts. In this study, we use numerical experiments with an idealized atmospheric general circulation model forced with the observed 2013/2014 SST anomalies in different ocean basins to understand the dominant mechanism that initiated the 2014 South Atlantic anticyclonic anomaly. We show that a forcing with global 2013/2014 SST anomalies enhances the chance for the occurrence of positive geopotential height anomalies in the South Atlantic. However, further sensitivity experiments with SST forcings in separate ocean basins suggest that neither the Indian Ocean nor tropical Pacific SST anomalies alone have contributed significantly to the anomalous atmospheric circulation that led to the 2014 South-East Brazil drought. The model study rather points to an important role of remote forcing from the South Pacific, local South Atlantic SSTs, and internal atmospheric variability in driving the persistent blocking over the South Atlantic

Functional food-related bioactive compounds: effect of sorghum phenolics on cancer cells in vivo and conversion of short- to long-chain omega-3 polyunsaturated fatty acids in duck liver in vivo

Doctor of PhilosophyDepartment of Human NutritionWeiqun WangMany functional food related bioactive compounds have been discovered and draw the attention of scientists. This dissertation focused on sorghum phenolic compounds and omega-3 polyunsaturated fatty acids. Study 1: phenolic agents in plant foods have been associated with chronic disease prevention, especially cancer. However, a direct evidence and the underlying mechanisms are mostly unknown. This study selected 13 sorghum accessions and was aim to investigate: (1) the effect of extracted sorghum phenolics on inhibiting cancer cell growth using hepatocarcinoma HepG2 and colorectal adenocarcinoma Caco-2 cell lines; (2) and the underlying mechanisms regarding cytotoxicity, cell cycle interruption, and apoptosis induction. Treatment of HepG2 and Caco-2 cells with the extracted phenolics at 0-200 M GAE (Gallic acid equivalent) up to 72 hrs resulted in a dose- and time-dependent reduction in cell number. The underlying mechanism of cell growth inhibition was examined by flow cytometry, significant inverse correlations were observed between the decreased cell number and increased cell cycle arrest at G2/M or induced apoptosis cells in both HepG2 and Caco-2 cells. The cytotoxic assay showed that the sorghum phenolic extracts were non-toxic. Although it was less sensitive, a similar inhibitory impact and underlying mechanisms were found in Caco-2 cells. These results indicated for the 1st time that a direct inhibition of either HepG2 or Caco-2 cell growth by phenolic extracts from13 selected sorghum accessions was due to cytostatic and apoptotic but not cytotoxic mechanisms. In addition, these findings suggested that sorghum be a valuable functional food by providing sustainable phenolics for potential cancer prevention. Study 2: omega-3 polyunsaturated fatty acids (ω-3 PUFAs) especially long-chain ω-3 PUFAs, have been associated with potential health benefits in chronic disease prevention. However, the conversion rate from short- to long-chain ω-3 PUFAs is limited in human body. This study was aim to assess the modification of fatty acid profiles as well as investigate the conversion of short- to long-chain ω-3 PUFAs in the liver of Shan Partridge duck after feeding various dietary fats. The experimental diets substituted the basal diet by 2% of flaxseed oil, rapeseed oil, beef tallow, or fish oil, respectively. As expected, the total ω-3 fatty acids and the ratio of total ω-3/ ω-6 significantly increased in both flaxseed and fish oil groups when compared with the control diet. No significant change of total saturated fatty acids or ω-3 fatty acids was found in both rapeseed and beef tallow groups. Short-chain ω-3 α-linolenic acid (ALA) in flaxseed oil-fed group was efficiently converted to long-chain ω-3 docosahexaenoic acid (DHA) in the duck liver. This study showed the fatty acid profiling in the duck liver after various dietary fat consumption, provided insight into a dose response change of ω-3 fatty acids, indicated an efficient conversion of short- to long-chain ω-3 fatty acid, and suggested alternative long-chain ω-3 fatty acid-enriched duck products for human health benefits. In conclusion, the two studies in this dissertation provided a fundamental understanding of anti-cancer activity by sorghum phenolic extracts and the conversion of short- to long-chain ω-3 PUFAs in duck liver, contribute to a long term goal of promoting sorghum and duck as sustainable phenolic and ω-3 PUFAs sources as well as healthy food products for human beings

Uncertainty in near-term global surface warming linked to tropical Pacific climate variability

Climate models generally simulate a long-term slowdown of the Pacific Walker Circulation in a warming world. However, despite increasing greenhouse forcing, there was an unprecedented intensification of the Pacific Trade Winds during 1992–2011, that co-occurred with a temporary slowdown in global surface warming. Using ensemble simulations from three different climate models starting from different initial conditions, we find a large spread in projected 20-year globally averaged surface air temperature trends that can be linked to differences in Pacific climate variability. This implies diminished predictive skill for global surface air temperature trends over decadal timescales, to a large extent due to intrinsic Pacific Ocean variability. We show, however, that this uncertainty can be considerably reduced when the initial oceanic state is known and well represented in the model. In this case, the spatial patterns of 20-year surface air temperature trends depend largely on the initial state of the Pacific Ocean

Drivers and impacts of the most extreme marine heatwaves events

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Sen Gupta, A., Thomsen, M., Benthuysen, J. A., Hobday, A. J., Oliver, E., Alexander, L. V., Burrows, M. T., Donat, M. G., Feng, M., Holbrook, N. J., Perkins-Kirkpatrick, S., Moore, P. J., Rodrigues, R. R., Scannell, H. A., Taschetto, A. S., Ummenhofer, C. C., Wernberg, T., & Smale, D. A. Drivers and impacts of the most extreme marine heatwaves events. Scientific Reports, 10(1), (2020): 19359. doi:10.1038/s41598-020-75445-3.Prolonged high-temperature extreme events in the ocean, marine heatwaves, can have severe and long-lasting impacts on marine ecosystems, fisheries and associated services. This study applies a marine heatwave framework to analyse a global sea surface temperature product and identify the most extreme events, based on their intensity, duration and spatial extent. Many of these events have yet to be described in terms of their physical attributes, generation mechanisms, or ecological impacts. Our synthesis identifies commonalities between marine heatwave characteristics and seasonality, links to the El Niño-Southern Oscillation, triggering processes and impacts on ocean productivity. The most intense events preferentially occur in summer, when climatological oceanic mixed layers are shallow and winds are weak, but at a time preceding climatological maximum sea surface temperatures. Most subtropical extreme marine heatwaves were triggered by persistent atmospheric high-pressure systems and anomalously weak wind speeds, associated with increased insolation, and reduced ocean heat losses. Furthermore, the most extreme events tended to coincide with reduced chlorophyll-a concentration at low and mid-latitudes. Understanding the importance of the oceanic background state, local and remote drivers and the ocean productivity response from past events are critical steps toward improving predictions of future marine heatwaves and their impacts.Concepts and analyses were developed during three workshops organized by an international working group on marine heatwaves (https://www.marineheatwaves.org) funded by a University of Western Australia Research Collaboration Award and a Natural Environment Research Council (UK) International Opportunity Fund (NE/N00678X/1). D.A.S. is supported by a UKRI Future Leaders Fellowship (MR/S032827/1). The Australian Research Council supported T.W. (FT110100174 and DP170100023) and A.S.T. (FT160100495). N.J.H. and L.V.A. are supported by the ARC Centre of Excellence for Climate Extremes (CE170100023). M.S.T was supported by the Brian Mason Trust. P.J.M. is supported by a Marie Curie Career Integration Grant (PCIG10-GA-2011–303685) and a Natural Environment Research Council (UK) Grant (NE/J024082/1). E.C.J.O. was supported by National Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant RGPIN-2018-05255 and Marine Environmental Observation, Prediction and Response Network (MEOPAR) project 1-02-02-059.1. C.C.U. acknowledges financial support through the Early Career Scientist Endowed Fund, George E. Thibault Early Career Scientist Fund, and The Joint Initiative Awards Fund from the Andrew W. Mellon Foundation at WHOI. M.G.D. received funding by the Spanish Ministry for the Economy, Industry and Competitiveness Ramón y Cajal 2017 grant reference RYC-2017-22964. NOAA High Resolution SST data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their Web site at https://www.esrl.noaa.gov/psd/

The impacts of greenhouse gases on sea-air variables through a coupled general circulation model

Há evidências de que o clima vem sendo alterado pela ação humana desde a época da Revolução Industrial devido à crescente emissão de gases estufa na atmosfera. Inúmeras curvas da variação da temperatura média anual têm sido publicadas com uma característica comum: o crescimento da temperatura durante o último século, totalizando aproximadamente 0,5ºC. Acredita-se que o aumento na concentração atmosférica dos gases responsáveis pelo efeito estufa tenha influência direta na tendência da temperatura dos últimos 100 anos. Este trabalho foi realizado com o intuito de estudar as mudanças no comportamento sazonal e anual da temperatura da superfície do mar (TSM), pressão atmosférica ao nível do mar (PNM) e transporte barotrópico (TB) devido ao aumento na concentração dos gases estufa. Foram utilizadas duas simulações do modelo acoplado NCAR CCSM sob as condições atmosféricas do período pré-industrial e pós-industrial. Os resultados revelam que, na média anual, as variáveis estudadas sofreram intensificação do período pré para o pós-industrial. A temperatura da superfície do mar mostrou aumento no período pós-industrial, principalmente durante o inverno e primavera, quando ocorre um aquecimento superior a 2,5ºC ao sul do continente sul-americano. A pressão atmosférica ao nível do mar na maior parte da região de estudo apresentou aumento no verão e outono e diminuição nas demais estações do ano, indicando uma intensificação no padrão sazonal dessa variável durante o período pós-industrial em relação ao pré-industrial. O transporte barotrópico revelou diferenças significativas entre os dois experimentos, mostrando maiores valores no período pós-industrial. A média da região apresentou um ciclo anual com diferenças de 2,5Sv ao longo do ano entre os dois períodos, com aumento para o pós-industrial. Esse aumento deve-se basicamente à intensificação do transporte barotrópico da Corrente Circumpolar Antártica durante todas as estações do ano. O Giro Subtropical também sofreu aumento de transporte, de menor intensidade, durante o período pós-industrial. Essa mudança no comportamento do transporte barotrópico sugere uma intensificação no padrão do Giro Subtropical e no transporte da Corrente Circumpolar Antártica para o período pós-industrial. As maiores mudanças entre os dois períodos simulados ocorreram nas latitudes mais altas.The main objective of this research is to study the impacts of the increase in greenhouse gases concentration on variables behavior at the sea-air interface. For this the NCAR CCSM coupled model is used by two climate conditions: the first one to pre-industrial period and the second one, to present day levels. Annual and seasonal climatology differences are analyzed for the of the following variables: air temperature, sea surface temperature, sea level pressure, wind stress, latent and sensible heat fluxes and barotropic transport. Statistics methods such as Empirical Ortoghonal Functions (EOF), Singular Value Decomposition (SVD) and Multi-Taper Method (MTM) are used to analyze changes in interannual behavior of these variables. The main results show that these surface variable are intensified from one period to the next. The air temperature and sea surface temperature showed increase in the pos-industrial period, mainly during the winter and spring. The sea level pressure also showed an increase on the annual mean. The wind stress revealed that the trade winds are intensified in autumn and the meridional wind component increases over the South Atlantic during winter. The winds adjacent to the South American continent also increased. Latent and sensible heat fluxes also increase, but not much, over some regions and decrease over others. Barotropic transport shows significant differences between the two experiments. There was increase of barotropic transport associated with the Subtropical Gyre and on Antartic Circumpolar Current. EOF, SVD and MTM analysis showed significant differences with respect to spatial patterns, behavior of the expansion coeficients time series and their variability

The impact of the South Atlantic Ocean on regional climate

Esta tese visa estudar o impacto da temperatura superfí-cie do mar (TSM) do Atlântico Sul na circulação atmos-férica regional, com ênfase na América do Sul. Os efeitos do Atlântico Sul na atmosfera são examinados através de dois conjuntos de simulações numéricas (ensemble), com o modelo atmosférico do NCAR (CCM3), forçados com a TSM observacional sobre dois domínios: o oceano global e o Atlântico Sul Subtropical, entre 20ºS e 60ºS. Uma metodologia de tratamento do ensemble é aplicada com o intuito de diminuir a variabilidade interna da atmosfera e ressaltar a resposta devido à forçante local de TSM. A comparação entre os experimentos numéricos através das análises de EOF e SVD mostrou que o Atlântico Sul exerce influência sobre a intensidade e posição geográfica da Zona de Convergência do Atlântico Sul (ZCAS) durante os meses de verão austral, associado a uma circulação ciclônica junto à costa sudeste brasileira, que advecta ar relativamente quente e úmido para a banda de precipitação oceânica. Este trabalho também mostra a importância conjunta da TSM do Atlântico Sul e Pacífico equatorial na modulação da intensidade e posição da ITCZ durante os meses de outono e inverno. Os resultados confirmam ainda o El Niño Oscilação Sul como um fator de impacto remoto na intensidade de chuvas na região sul do Brasil durante o inverno.This work aims to study the impact of South Atlantic sea surface temperature (SST) on regional atmosfheric circulation. In order to achieve this purpose we used the atmospheric global circulation model Community Climate Model (CCM 3) from National Center for Atmosfheric Research (NCAR). the effects of South Atlantic on atmosphere are examined through two sets of numerical simulations (ensemble) generated with different SST configurations. The integrations were forced by SST from observational data over two domains: global ocean and South Atlantic from 20ºS to 60ºS. Looking for the reduction of the internal variability of the atmosphere and for increase of the response from the local SST forcing, a forcing, a special treatment was applied to the ensembles. The statistical methodology used in this study includes simple analysis such as climatology, variance and correlation as well as Empirical Orthogonal Functions and Singular Value Decomposition. the comparasion between the numerical experiments showed that the South Atlantic influences the interannual variability of precipitation over South America, especially with respect to the intensity and geographic position od South Atlantic Convergenge Zone (SACZ) during the austral summer season. The anomalous SST of the Subtropical South Atlantic induces the heat exchange between ocean and atmosphere, which togeter with a cyclonic circulation near the southern Brazilian coast, advects relatively moist and warm air to the oceanic part of SACZ. The increase of convection over this band inhibits the solar radiation in the surface, preventing the continuous increase of SST (negative feedback). This work also shows the importance of SST from the South Atlantic and Equatorial Pacific in modulating the intensity and position of ITCZ during the autumn and winter monhths. This study also confirms the El Niño - Southern Oscillation (ENSO) as a remote impact factor controling the intensity of rain over southern Brazil mainly during winter

The impacts of greenhouse gases on sea-air variables through a coupled general circulation model

Há evidências de que o clima vem sendo alterado pela ação humana desde a época da Revolução Industrial devido à crescente emissão de gases estufa na atmosfera. Inúmeras curvas da variação da temperatura média anual têm sido publicadas com uma característica comum: o crescimento da temperatura durante o último século, totalizando aproximadamente 0,5ºC. Acredita-se que o aumento na concentração atmosférica dos gases responsáveis pelo efeito estufa tenha influência direta na tendência da temperatura dos últimos 100 anos. Este trabalho foi realizado com o intuito de estudar as mudanças no comportamento sazonal e anual da temperatura da superfície do mar (TSM), pressão atmosférica ao nível do mar (PNM) e transporte barotrópico (TB) devido ao aumento na concentração dos gases estufa. Foram utilizadas duas simulações do modelo acoplado NCAR CCSM sob as condições atmosféricas do período pré-industrial e pós-industrial. Os resultados revelam que, na média anual, as variáveis estudadas sofreram intensificação do período pré para o pós-industrial. A temperatura da superfície do mar mostrou aumento no período pós-industrial, principalmente durante o inverno e primavera, quando ocorre um aquecimento superior a 2,5ºC ao sul do continente sul-americano. A pressão atmosférica ao nível do mar na maior parte da região de estudo apresentou aumento no verão e outono e diminuição nas demais estações do ano, indicando uma intensificação no padrão sazonal dessa variável durante o período pós-industrial em relação ao pré-industrial. O transporte barotrópico revelou diferenças significativas entre os dois experimentos, mostrando maiores valores no período pós-industrial. A média da região apresentou um ciclo anual com diferenças de 2,5Sv ao longo do ano entre os dois períodos, com aumento para o pós-industrial. Esse aumento deve-se basicamente à intensificação do transporte barotrópico da Corrente Circumpolar Antártica durante todas as estações do ano. O Giro Subtropical também sofreu aumento de transporte, de menor intensidade, durante o período pós-industrial. Essa mudança no comportamento do transporte barotrópico sugere uma intensificação no padrão do Giro Subtropical e no transporte da Corrente Circumpolar Antártica para o período pós-industrial. As maiores mudanças entre os dois períodos simulados ocorreram nas latitudes mais altas.The main objective of this research is to study the impacts of the increase in greenhouse gases concentration on variables behavior at the sea-air interface. For this the NCAR CCSM coupled model is used by two climate conditions: the first one to pre-industrial period and the second one, to present day levels. Annual and seasonal climatology differences are analyzed for the of the following variables: air temperature, sea surface temperature, sea level pressure, wind stress, latent and sensible heat fluxes and barotropic transport. Statistics methods such as Empirical Ortoghonal Functions (EOF), Singular Value Decomposition (SVD) and Multi-Taper Method (MTM) are used to analyze changes in interannual behavior of these variables. The main results show that these surface variable are intensified from one period to the next. The air temperature and sea surface temperature showed increase in the pos-industrial period, mainly during the winter and spring. The sea level pressure also showed an increase on the annual mean. The wind stress revealed that the trade winds are intensified in autumn and the meridional wind component increases over the South Atlantic during winter. The winds adjacent to the South American continent also increased. Latent and sensible heat fluxes also increase, but not much, over some regions and decrease over others. Barotropic transport shows significant differences between the two experiments. There was increase of barotropic transport associated with the Subtropical Gyre and on Antartic Circumpolar Current. EOF, SVD and MTM analysis showed significant differences with respect to spatial patterns, behavior of the expansion coeficients time series and their variability