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No description available.

During the last 21,000 years, the planet underwent major changes. The atmospheric CO2 concentration increased ∼50% (Monnin et al., 2001) and the mean global temperature increased 4.0±0.8°C until pre-industrial times (Annan and Hargreaves, 2013). As a consequence of this warming, the huge ice sheets that covered North America, Northern Europe and part of Eurasia melted and the polar and subpolar ocean surface received a large amount of freshwater from these retracting ice sheets. The input of freshwater alters pressure gradients on the sea surface and also the density of water masses. Since the ocean circulation is partially driven by density differences, the deglacial meltwater has the potential to affect the ocean circulation. In this PhD thesis, the impacts of meltwater input since the Last Glacial Maximum into the high latitudes, especially of the Atlantic Ocean, are studied using the results of a transient simulation of the last 22 thousand years with NCAR-CCSM3. The main results show that: (1) the Atlantic Meridional Overturning Circulation (AMOC) slowed down during freshwater discharge events near dense water formation regions; (2) North Atlantic Deep Water (NADW) was absent in the beginning of the deglaciation, while its intermediate version -- Glacial North Atlantic Intermediate Water (GNAIW) -- was being formed; (3) GNAIW was a fresh and cold water mass, very similar to the Antarctic Intermediate Water (AAIW) in the thermohaline domain; (4) the deep and abyssal Atlantic basin was dominated by AABW in the first half of the simulation; (5) the transition from GNAIW to NADW occurred after the Heinrich Stadial 1; (6) when the NADW appeared, around 12 thousand years ago (ka), AABW retracted and was constrained to lie near the bottom; (7) the presence of a low-salinity layer in the Southern Ocean surface around ∼14,000 years ago prevented the release of heat from deep waters to the atmosphere, warming the AABW; (8) the Antarctic Coastal Current (ACoC) was reinforced by the meltwater discharge from the Antarctic ice sheet. Using the Indian Ocean as a comparison, it was observed that the North Atlantic affected the western tropical Indian through atmosphere, while climatic variations associated with the Southern Hemisphere were transmitted via ocean -- especially through intermediate waters. Although the initial conditions in the glacial and modern ocean are different, this study may be used to foresee the possible responses of the ocean to the accelerated melting of glaciers and ice sheets, which are associated with dramatic climate changes. / Durante os últimos 21.000 anos, o planeta sofreu grandes mudanças. A concentração de CO2 atmosférico aumentou cerca de ∼50% (Monnin et al., 2001) e a temperatura média global aumentou 4,0±0,8°C até a época pré industrial (Annan and Hargreaves, 2013). Como consequência deste aquecimento, os grandes mantos de gelo que cobriam a América do Norte, o norte da Europa e parte da Eurásia derreteram e o oceano polar e subpolar recebeu grandes quantidades de água doce destes mantos em retração. A entrada de água doce altera gradientes de pressão na superfície do mar e também a densidade de massas de água. Como a circulação oceânica é parcialmente forçada por diferenças de densidade, a água de degelo tem o potencial de afetar esta circulação. Nesta tese de Doutorado, os impactos da entrada de água de degelo no oceano desde o Último Máximo Glacial em altas latitudes, especialmente do Oceano Atlântico, são estudados usando os resultados de uma simulação transiente dos últimos 22 mil anos com o modelo NCAR-CCSM3. Os principais resultados mostram que: (1) a circulação de revolvimento meridional do Atlântico enfraqueceu durante eventos de descarga de água doce próxima a regiões de formação de água densa; (2) a Água Profunda do Atlântico Norte (APAN) estava ausente no começo da deglaciação, enquanto sua versão intermediária -- Água Glacial Intermediária do Atlântico Norte (AGIAN) -- era formada; (3) AGIAN era uma massa d\'água doce e fria, semelhante à Água Intermediária Antártica (AIA) no domínio termohalino; (4) as camadas profundas e de fundo da bacia do Atlântico eram dominadas pela Água de Fundo Antártica (AFA) na primeira metade da simulação; (5) a transição de AGIAN para APAN ocorreu após o Heinrich Stadial 1; (6) quando a APAN apareceu, cerca de 12 mil anos atrás (ka), a AFA retraiu e ficou limitada às camadas de fundo; (7) a presença de uma camada de baixa salinidade na superfície do Oceano Austral há ∼14 mil anos impedia a liberação de calor das águas profundas para a atmosfera, aquecendo a AFA; (8) a Corrente Costeira Antártica foi intensificada pela descarga de água de degelo proveniente do manto de gelo Antártico. Usando o Oceano Índico como comparação, foi observado que o Atlântico Norte afetou o Índico oeste tropical através de processos atmosféricos, enquanto variações climáticas associadas ao Hemisfério Sul foram transmitidas via oceano -- especialmente através das camadas intermediárias. Embora as condições iniciais dos oceanos glacial e moderno sejam diferentes, este estudo pode ser usado para prever as possíveis respostas do oceano ao presente derretimento acelerado de geleiras e mantos de gelo associado a mudanças climáticas abruptas.

Os estudos sobre a ecologia de ovos e larvas de peixes em áreas costeiras desempenham um papel relevante para o entendimento da biologia das espécies, visto que essa fase de desenvolvimento é o mais crítico do seu ciclo de vida. Este trabalho tem como objetivo principal descrever a variação temporal da comunidade ictioplanctônica em estação fixa localizada em Ubatuba-SP (23º 36,79’ S; 44º 53,46’ W), e analisar sua relação com a hidrografia local, entre fevereiro/2014 e fevereiro/2015. Para o melhor entendimento da área de estudo foi realizado: análise de percentuais de massa de água, composição, densidade, distribuição temporal das larvas de peixes e uma análise multivariada de componentes principais (ACP). Os principais resultados mostram a alta influência da Água Costeira (≥ 50%) nos primeiros 10 m de profundidade em todos os meses de coleta. A Água Tropical não foi identificada com altos percentuais (≥ 50%), com exceção de junho e julho . A Água Central do Atlântico Sul (ACAS) comparece com altos percentuais (≥ 50%) em fevereiro, outubro, novembro e dezembro/2014. A concentração média de Clorofila a, nas campanhas com alta influência da ACAS, foi de 1,98±1,25 mg m-3 e, nas campanhas com baixa influência da ACAS, foi de 1,04±0,71 mg m-3. A biomassa total do zooplâncton foi maior na rede de malha 50 μm e menor na de 200 μm. Foram coletadas 2.446 larvas de peixes, sendo que 1.906 foram identificadas em 17 ordens, 25 famílias, 23 gêneros e 26 espécies. Paralichthyidae e Sciaenidae tiveram frequência de ocorrência (FO) superior a 80% e densidade superior a 40 larvas 100 m-3; a FO de Ophidiidae e Carangidae foi de 58 e 67%, respetivamente. A análise de PCA evidenciou a formação de três grupos de espécies, cuja densidade e frequência de ocorrência variam no decorrer do ano, especialmente em função da maior ou menor influência da ACAS. / Studies on the ecology of fish eggs and larvae in coastal regions are important to understand the biology of species, since this developmental stage is the most critical in its life cycle. This study aims to describe the temporal variation of ichthyoplankton community in a fixed sampling station at Ubatuba-SP (23º 36.79’ S; 44º 53.46’ W), and to evaluate its relation with the local hydrographical regime along a year, February/2014 to February/2015. To better understand the study area, we performed: an analysis of water masse percentages, composition, density and temporal distribution of larval fishes and a principal component analysis (PCA). The main results show the high influence of Coastal Water (≥50%) in the first 10 m depth on all sampling months. The Tropical Water was not recognized with high percentages (≥50%), with exception on June and July. ACAS occurs with high percentages (≥50%) on February, October, November and December /2014. Chlorophyll-a was 1.98±1.25 mg m-3, in campaigns with high ACAS influence, while under low ACAS influence the average chlorophyll-a was 1.04±0.71 mg m-3. Total biomass was highest for 50μm zooplankton and lowest for 200μm ones. A total of 2,446 larvae were collected and 1,906 were identified, totaling 17 orders, 25 families, 23 genera and 26 species. Occurrence frequency of Paralichthyidae and Sciaenidae was superior than 80% and density higher than 40 larvae 100 m-3. For Ophidiidae and Carangidae, occurrence frequency was 58 and 67%, respectively. According the PCA, three groups of species were formed, whose occurrence frequence and density vary during the year, especially in light of the greater or lesser influence of the ACAS.

The investigation of the role of basin-scale forcing on the circulation of the Faroe-Shetland Channel (FSC) is important to further understanding of the inter-annual variability of the Atlantic water (AW) fluxes in this region. The FSC plays a key role in the transfer of warm and saline AW towards the Nordic Seas that is an integral part of the Atlantic Meridional Overturning Circulation which is projected to decline over the twenty-first century and might reduce the oceanic heat and salt transports towards the Arctic. So far little attention has been paid to the mechanisms driving the AW fluxes in the FSC, reliable estimates of AW temperature and salt transports time series are lacking. This study presents a new time series of the AW fluxes based on the combination of hydrography and altimetry data. The mechanisms involved in driving the variability of AW fluxes are considered based on observational data and the output from a high-resolution ocean model (VIKING20). The hydrographic observations from 1993 to 2015 show an increase in temperature and salinity of AW. However, there is no evidence of trends in AW volume, temperature or salt transports during the observed period. This analysis confirms that the amount of heat and salt transported through the FSC is dominated by the volume transport. Moreover, this study identifies a bias in the standard deviation of the geostrophic velocity at a depth associated with referencing the geostrophic calculations to the sea surface geostrophic velocity from satellite altimetry. This finding does not strongly influence the AW volume transports in the AW layer, however, it has important implications for estimates of the geostrophic volume transport at depth. This study shows that the Ekman driven up/downwelling and the differential Ekman pumping mechanisms driven by the local wind forcing may influence sea surface height (SSH) and the displacement of isopycnals in the channel, leading to AW volume transport variabilit However, due to the large associated error bars on the surface and subsurface parameters, there is no clear evidence that these mechanisms are significantly responsible for the AW volume transport variability in the FSC. Lagrangian trajectories show evidence of two pathways from the North Atlantic to the FSC that may explain AW variability in the FSC: one pathway involves the flow of warm and saline waters from the Rockall Trough that corresponds to high temperatures and low AW volume transport in the channel, and the other pathway involves the flow of relatively cooler and less saline waters from the Iceland Basin that is linked to low temperatures and stronger volume transport in the FSC. Moreover, we show that the first (second) pathway is associated with the negative (positive) phases of the North Atlantic Oscillation (NAO) and the ocean gyre contraction (expansion). The changes of the NAO index phases explain 26 % of the AW volume transport variance in the FSC. Another important mechanism that leads to stronger (weaker) AW volume transport is stronger (weaker) pressure gradient across the Greenland-Scotland Ridge, reflected by the SSH changes. This mechanism explains 29 % of AW volume transport variance in the FSC.

Os estudos sobre a ecologia de ovos e larvas de peixes em áreas costeiras desempenham um papel relevante para o entendimento da biologia das espécies, visto que essa fase de desenvolvimento é o mais crítico do seu ciclo de vida. Este trabalho tem como objetivo principal descrever a variação temporal da comunidade ictioplanctônica em estação fixa localizada em Ubatuba-SP (23º 36,79’ S; 44º 53,46’ W), e analisar sua relação com a hidrografia local, entre fevereiro/2014 e fevereiro/2015. Para o melhor entendimento da área de estudo foi realizado: análise de percentuais de massa de água, composição, densidade, distribuição temporal das larvas de peixes e uma análise multivariada de componentes principais (ACP). Os principais resultados mostram a alta influência da Água Costeira (≥ 50%) nos primeiros 10 m de profundidade em todos os meses de coleta. A Água Tropical não foi identificada com altos percentuais (≥ 50%), com exceção de junho e julho . A Água Central do Atlântico Sul (ACAS) comparece com altos percentuais (≥ 50%) em fevereiro, outubro, novembro e dezembro/2014. A concentração média de Clorofila a, nas campanhas com alta influência da ACAS, foi de 1,98±1,25 mg m-3 e, nas campanhas com baixa influência da ACAS, foi de 1,04±0,71 mg m-3. A biomassa total do zooplâncton foi maior na rede de malha 50 μm e menor na de 200 μm. Foram coletadas 2.446 larvas de peixes, sendo que 1.906 foram identificadas em 17 ordens, 25 famílias, 23 gêneros e 26 espécies. Paralichthyidae e Sciaenidae tiveram frequência de ocorrência (FO) superior a 80% e densidade superior a 40 larvas 100 m-3; a FO de Ophidiidae e Carangidae foi de 58 e 67%, respetivamente. A análise de PCA evidenciou a formação de três grupos de espécies, cuja densidade e frequência de ocorrência variam no decorrer do ano, especialmente em função da maior ou menor influência da ACAS. / Studies on the ecology of fish eggs and larvae in coastal regions are important to understand the biology of species, since this developmental stage is the most critical in its life cycle. This study aims to describe the temporal variation of ichthyoplankton community in a fixed sampling station at Ubatuba-SP (23º 36.79’ S; 44º 53.46’ W), and to evaluate its relation with the local hydrographical regime along a year, February/2014 to February/2015. To better understand the study area, we performed: an analysis of water masse percentages, composition, density and temporal distribution of larval fishes and a principal component analysis (PCA). The main results show the high influence of Coastal Water (≥50%) in the first 10 m depth on all sampling months. The Tropical Water was not recognized with high percentages (≥50%), with exception on June and July. ACAS occurs with high percentages (≥50%) on February, October, November and December /2014. Chlorophyll-a was 1.98±1.25 mg m-3, in campaigns with high ACAS influence, while under low ACAS influence the average chlorophyll-a was 1.04±0.71 mg m-3. Total biomass was highest for 50μm zooplankton and lowest for 200μm ones. A total of 2,446 larvae were collected and 1,906 were identified, totaling 17 orders, 25 families, 23 genera and 26 species. Occurrence frequency of Paralichthyidae and Sciaenidae was superior than 80% and density higher than 40 larvae 100 m-3. For Ophidiidae and Carangidae, occurrence frequency was 58 and 67%, respectively. According the PCA, three groups of species were formed, whose occurrence frequence and density vary during the year, especially in light of the greater or lesser influence of the ACAS.

During the last 21,000 years, the planet underwent major changes. The atmospheric CO2 concentration increased ∼50% (Monnin et al., 2001) and the mean global temperature increased 4.0±0.8°C until pre-industrial times (Annan and Hargreaves, 2013). As a consequence of this warming, the huge ice sheets that covered North America, Northern Europe and part of Eurasia melted and the polar and subpolar ocean surface received a large amount of freshwater from these retracting ice sheets. The input of freshwater alters pressure gradients on the sea surface and also the density of water masses. Since the ocean circulation is partially driven by density differences, the deglacial meltwater has the potential to affect the ocean circulation. In this PhD thesis, the impacts of meltwater input since the Last Glacial Maximum into the high latitudes, especially of the Atlantic Ocean, are studied using the results of a transient simulation of the last 22 thousand years with NCAR-CCSM3. The main results show that: (1) the Atlantic Meridional Overturning Circulation (AMOC) slowed down during freshwater discharge events near dense water formation regions; (2) North Atlantic Deep Water (NADW) was absent in the beginning of the deglaciation, while its intermediate version -- Glacial North Atlantic Intermediate Water (GNAIW) -- was being formed; (3) GNAIW was a fresh and cold water mass, very similar to the Antarctic Intermediate Water (AAIW) in the thermohaline domain; (4) the deep and abyssal Atlantic basin was dominated by AABW in the first half of the simulation; (5) the transition from GNAIW to NADW occurred after the Heinrich Stadial 1; (6) when the NADW appeared, around 12 thousand years ago (ka), AABW retracted and was constrained to lie near the bottom; (7) the presence of a low-salinity layer in the Southern Ocean surface around ∼14,000 years ago prevented the release of heat from deep waters to the atmosphere, warming the AABW; (8) the Antarctic Coastal Current (ACoC) was reinforced by the meltwater discharge from the Antarctic ice sheet. Using the Indian Ocean as a comparison, it was observed that the North Atlantic affected the western tropical Indian through atmosphere, while climatic variations associated with the Southern Hemisphere were transmitted via ocean -- especially through intermediate waters. Although the initial conditions in the glacial and modern ocean are different, this study may be used to foresee the possible responses of the ocean to the accelerated melting of glaciers and ice sheets, which are associated with dramatic climate changes. / Durante os últimos 21.000 anos, o planeta sofreu grandes mudanças. A concentração de CO2 atmosférico aumentou cerca de ∼50% (Monnin et al., 2001) e a temperatura média global aumentou 4,0±0,8°C até a época pré industrial (Annan and Hargreaves, 2013). Como consequência deste aquecimento, os grandes mantos de gelo que cobriam a América do Norte, o norte da Europa e parte da Eurásia derreteram e o oceano polar e subpolar recebeu grandes quantidades de água doce destes mantos em retração. A entrada de água doce altera gradientes de pressão na superfície do mar e também a densidade de massas de água. Como a circulação oceânica é parcialmente forçada por diferenças de densidade, a água de degelo tem o potencial de afetar esta circulação. Nesta tese de Doutorado, os impactos da entrada de água de degelo no oceano desde o Último Máximo Glacial em altas latitudes, especialmente do Oceano Atlântico, são estudados usando os resultados de uma simulação transiente dos últimos 22 mil anos com o modelo NCAR-CCSM3. Os principais resultados mostram que: (1) a circulação de revolvimento meridional do Atlântico enfraqueceu durante eventos de descarga de água doce próxima a regiões de formação de água densa; (2) a Água Profunda do Atlântico Norte (APAN) estava ausente no começo da deglaciação, enquanto sua versão intermediária -- Água Glacial Intermediária do Atlântico Norte (AGIAN) -- era formada; (3) AGIAN era uma massa d\'água doce e fria, semelhante à Água Intermediária Antártica (AIA) no domínio termohalino; (4) as camadas profundas e de fundo da bacia do Atlântico eram dominadas pela Água de Fundo Antártica (AFA) na primeira metade da simulação; (5) a transição de AGIAN para APAN ocorreu após o Heinrich Stadial 1; (6) quando a APAN apareceu, cerca de 12 mil anos atrás (ka), a AFA retraiu e ficou limitada às camadas de fundo; (7) a presença de uma camada de baixa salinidade na superfície do Oceano Austral há ∼14 mil anos impedia a liberação de calor das águas profundas para a atmosfera, aquecendo a AFA; (8) a Corrente Costeira Antártica foi intensificada pela descarga de água de degelo proveniente do manto de gelo Antártico. Usando o Oceano Índico como comparação, foi observado que o Atlântico Norte afetou o Índico oeste tropical através de processos atmosféricos, enquanto variações climáticas associadas ao Hemisfério Sul foram transmitidas via oceano -- especialmente através das camadas intermediárias. Embora as condições iniciais dos oceanos glacial e moderno sejam diferentes, este estudo pode ser usado para prever as possíveis respostas do oceano ao presente derretimento acelerado de geleiras e mantos de gelo associado a mudanças climáticas abruptas.

Thesis (M.A.)--Saint Mary's University, 2007. / Includes abstract. Supervisor: John G. Reid. Includes bibliographical references (leaves 633-722).

In the Sergipe-Alagoas Basin, along the northeast coast of Brazil, the lacustrine, middle rift sequence is composed of the Lower Cretaceous Morro do Chaves and Coqueiro Seco Formations. Subsurface analysis permitted recognition and mapping of four principal types of depositional systems that infilled the basin with more than 3,000 meters of clastic-carbonate sediments: Morro do Chaves carbonate platform, Coqueiro Seco fluvial-deltaic, Coqueiro Seco fan delta, and Coqueiro Seco slope systems. The generally poor quality of seismic profiles in this rift sequence precludes conventional seismic stratigraphic approaches. Morro do Chaves lacustrine carbonate platform sediments were deposited on shallow positive areas flanking the principal point sources (rivers), and are composed of massively bedded, high energy limestones. Contemporaneous with shallow-water sedimentation, deepwater euxinic and bituminous lacustrine shales were deposited under starved basin conditions. Sublacustrine canyon excavation attested to the presence of a destructional slope episode. Coqueiro Seco fluvial-deltaic, fan delta, and slope sediments are principally terrigenous. Fluvialdeltaic and fan delta facies display high sand/shale ratios and blocky to massive E-log patterns; slope facies display serrate to digitate E-log patterns and are less sandy. Delta plain channel-fill facies and coarse-grained meanderbelt fluvial facies are dominant in fluvial-deltaic systems, and proximal to medial conglomerates and coarse conglomeratic sandstones are dominant facies in fan delta systems. Slope facies are composed of sublacustrine fans composed of fine-to medium-grained sandstones enveloped by thick, subbituminous shales, and thin, marly, lacustrine limestones. Coqueiro Seco clastic systems prograded across the basin and buried Morro do Chaves carbonate platforms in response to tectonic pulses related to rift development. Cyclic sedimentation occurred in the highly unstable Alagoas Sub-basin where fluvial-deltaic and slope systems are dominant, but fan delta and slope systems in the less complex Rio São Francisco Sub-basin do not exhibit cyclicity. Coqueiro Seco fluvial-deltaic, fan delta and slope sedimentation terminated because of continued basin subsidence and diminishing sediment supply as source areas were leveled. Consequently, the basin became the site of lacustrine shale deposition represented by the Ponta Verde Formation in the Alagoas Sub-basin. The rift sequence is truncated by a pre-Aptian unconformity in the Rio São Francisco Sub-basin. Evaluation of petroleum occurrences in relationship to defined depositional systems permitted recognition of several types of plays characterized by unique structural and stratigraphic relationships exhibited by reservoirs, source beds and structure. The Coqueiro Seco slope play, formed by updip pinchout of turbidite fans, is judged the most promising in the sequence. / text

Previous correlations have been established between the El Nino Southern Oscillation (ENSO) and both the tropical north Atlantic sea-surface temperatures (SSTs) and precipitation anomalies in the southeastern and mid-Atlantic states. Both bivariate and partial correlations are used over a five and six-month lag to assess the relevance the tropical Atlantic SSTs have in eastern United States precipitation patterns. Significant correlations between Pacific SSTs and precipitation were found during winter months which agree with previous literature. The relationship with the Atlantic SSTs was less robust, as some significant values were established over three seasons, excluding winter. Only the spring season showed a partial explanation of the Atlantic SST's role in the precipitation's response to Pacific SSTs. These relationships did not occur during the times when significant correlations were made between Pacific SSTs and precipitation. / Department of Geography