Climatic evolution of eastern South America during the last deglaciation: a paleoceanographic approach

Para dar suporte ao atual debate sobre as consequências climáticas da liberação antropogênica de CO2 na atmosfera, o refinamento do conhecimento sobre mudanças climáticas e oceanográficas no passado é necessário. A Circulação de Revolvimento Meridional do Atlântico (CRMA) tem papel fundamental na oceanografia e clima das áreas sob influência do Oceano Atlântico, controlando diretamente a estratificação e distribuição de massas d\'água, a quantidade de calor transportada pelo oceano e os ciclo e armazenamento de compostos químicos, como o CO2 em mar profundo. A formação e circulação da Água Intermediária Antártica (AIA), envolvida no transporte de calor e sal para o giro subtropical do Hemisfério Sul e nas teleconexões climáticas entre altas e baixas latitudes, é componente importante do ramo superior da CRMA. A reconstrução de propriedades de massas de água intermediárias é, portanto, importante para a compreensão dos sistemas de retroalimentação entre oceano-clima. No entanto, informações quanto a evolução da AIA continuam limitadas. Oscilações da CRMA e consequentes mudanças na distribuição de calor tem implicações importantes para o clima Sul Americano, influenciando a disponibilidade de umidade para o Sistema de Monções Sul Americano (SMSA), via temperatura da superfície marinha e posicionamento da Zona de Convergência Intertropical. Neste trabalho nós reconstruímos a assinatura isotópica da AIA durante os estágios isotópicos marinhos 2 e 3 (41-12 cal ka AP) usando isótopos de carbono e oxigênio de foraminíferos bentônicos (gêneros Cibicidoides e Uvigerina) de um testemunho de sedimentos marinhos datados por radiocarbono (1100 m de profundidade e a 20°S na costa do Brasil). Concluímos que propriedades físicas e químicas da AIA mudaram durante os estadiais Heinrich 3 e 4, provavelmente como consequência de enfraquecimento da CRMA durante estes períodos. Também reconstruímos as condições continentais do leste brasileiro entre o último máximo glacial e a deglaciação (23-12 cal ka AP) baseadas em razões Ti/Ca de nosso testemunho de sedimentos marinhos como indicadoras de aporte terrígeno do Rio Doce. A maior parte da chuva que cai na Bacia do Rio Doce está relacionada a atividade do SMAS. Nosso registro de Ti/Ca em conjunto com \'\'delta\' POT.18\'O de espeleotemas da Caverna Lapa Sem Fim, também no leste do Brasil, sugere diminuição marcante da chuva durante o interestadial Bølling-Allerød, provavelmente relacionada a enfraquecimento do SMAS. Ademais comparamos as razões de Ti/Ca com dados de saída da rodada SYNTRACE do modelo climático CCSM3 com forçantes transientes para a última deglaciação. Os registros geoquímicos e a saída do modelo mostram resultados consistentes entre si e sugerem que o leste da América do Sul passou pelo seu período mais seco de toda a última deglaciação durante o interestadial Bølling-Allerød, provavelmente relacionado ao enfraquecimento do SMAS.

Gas production during the pyrolysis and gasification of biological and physico-chemical sludges from oil refinery

Pyrolysis and gasification of two different sludges coming from a Spanish refinery have been performed at different experimental conditions. A physico-chemical (PC) and a biological (BIO) sludge have been studied. Runs at different heating rates (approx. 4 and 10 K/s) and with different contact time between gases and decomposed sludge have been performed. In general, the ratio H2/CO is higher in pyrolytic runs. The highest ratio is obtained in the pyrolysis at low heating rate and parallel flow, using both sludges. The maximum emission of CO, i.e. the worst combustion conditions, is given in the runs where contact time is minimized and at high heating rates.

Missing Rings in Pinus halepensis – The Missing Link to Relate the Tree-Ring Record to Extreme Climatic Events

Climate predictions for the Mediterranean Basin include increased temperatures, decreased precipitation, and increased frequency of extreme climatic events (ECE). These conditions are associated with decreased tree growth and increased vulnerability to pests and diseases. The anatomy of tree rings responds to these environmental conditions. Quantitatively, the width of a tree ring is largely determined by the rate and duration of cell division by the vascular cambium. In the Mediterranean climate, this division may occur throughout almost the entire year. Alternatively, cell division may cease during relatively cool and dry winters, only to resume in the same calendar year with milder temperatures and increased availability of water. Under particularly adverse conditions, no xylem may be produced in parts of the stem, resulting in a missing ring (MR). A dendrochronological network of Pinus halepensis was used to determine the relationship of MR to ECE. The network consisted of 113 sites, 1,509 trees, 2,593 cores, and 225,428 tree rings throughout the distribution range of the species. A total of 4,150 MR were identified. Binomial logistic regression analysis determined that MR frequency increased with increased cambial age. Spatial analysis indicated that the geographic areas of south-eastern Spain and northern Algeria contained the greatest frequency of MR. Dendroclimatic regression analysis indicated a non-linear relationship of MR to total monthly precipitation and mean temperature. MR are strongly associated with the combination of monthly mean temperature from previous October till current February and total precipitation from previous September till current May. They are likely to occur with total precipitation lower than 50 mm and temperatures higher than 5°C. This conclusion is global and can be applied to every site across the distribution area. Rather than simply being a complication for dendrochronology, MR formation is a fundamental response of trees to adverse environmental conditions. The demonstrated relationship of MR formation to ECE across this dendrochronological network in the Mediterranean basin shows the potential of MR analysis to reconstruct the history of past climatic extremes and to predict future forest dynamics in a changing climate.

The climatic changes of later geological times : a discussion based on observations made in the Cordilleras of North America / by J. D. Whitney.

v.7:no.2 (1882)

Mineral-magnetic record of Late Quaternary climatic changes in a high Alpine lake

The magnetic properties of a sediment core from a high altitude lake in the Swiss Alps were compared with palynological and geochemical data to link climatic and mineral magnetic variations. According to pollen data, the sediments extend from the present to the Younger Dryas, i.e., they cover more than 10,000 years of environmental change in the Alps. The major change in magnetic properties corresponds to the climatic warming of the early Holocene. High-coercivity magnetic minerals that characterize the Late Glacial period almost disappeared during the Holocene and the concentration of ferrimagnetic minerals increased sharply. The contribution of superparamagnetic grains also decreased in the Holocene sediments. Similar variations in {SP} content and coercivity, of smaller magnitude, are found in the Holocene and are interpreted to represent minor climatic variations. Comparison with the historical record of the last 1000 years confirms this interpretation. The magnetic mineralogy, the superparamagnetic contents, and the {IRM} intensity in the coarse-grained, Late Glacial sediments are similar to those measured in the catchment bedrock. This indicates a detrital origin. The different properties and the higher concentration of magnetic minerals in the Holocene sediments are due to authigenic phases. Magnetic properties provide a high resolution record of climatic change. They are sensitive even to small variations that are not recorded in the pollen or {LOI} data. Magnetic parameters show fine-scale variation and constitute a valuable supplement to conventional climatic indicators.

Selected bibliography of physico-chemical properties in liquid ammonia and related solvents /

Mode of access: Internet.

Climatic guide for Baltimore, Maryland /

Chiefly tables.

Climatic guide for Seattle, Washington and adjacent Puget Sound area /

Chiefly tables.

Climatic guide for Houston-Galveston, Texas area.

Mode of access: Internet.