Subseasonal variability of tropical Indian Ocean sea surface temperature is thought to influence the active-break cycle of the Asian monsoon. There are several open questions related to the role of surface fluxes, large-scale ocean circulation and subsurface ocean processes in the subseasonal variability of upper ocean temperature. We present a unified study of the subseasonal (2-90 day) variability of surface heat flux and upper ocean temperature and salinity throughout the tropical Indian Ocean in all seasons. We focus on the relation between surface fluxes and ocean response using a new satellitebased daily heat flux. The role of ocean processes (advection, entrainment and mixing) in determining SST variability is diagnosed from the daily satellite SST. Before the onset of the summer monsoon, sea surface temperature (SST) of the north Indian Ocean warms to 30-32oC. Climatological mean mixed layer depth in spring (March-May) is 10-20 m, and net surface heat flux (Qnet) is 80-100 Wm 2 into the ocean. It has been suggested that observed spring SST warming is small mainly due to (a) penetrative flux of solar radiation through the base of the mixed layer (Qpen), (b) advective cooling by upper ocean currents and (c) entrainment of sub-mixed layer cool water. We estimate the role of the first two processes in SST evolution from a two-week ARMEX experiment in April-May 2005 in the the southeastern Arabian Sea. The upper ocean is stratified by salinity and temperature, and mixed layer depth is shallow (6 to 12 m). Current speed at 2 m depth is high even under light winds. Currents within the mixed layer are quite distinct from those at 25 m. On subseasonal scales, SST warming is followed by rapid cooling. The cooling occurs although the ocean gains heat at the surface - Qnet is about 105 Wm 2 in the warming phase, and 25 Wm 2 in the cooling phase; penetrative loss Qpen, is 80 Wm 2 and 70 Wm 2. In the warming phase, SST rises mainly due to heat absorbed within the mixed layer, i.e. Qnet minus Qpen; Qpen, reduces the rate of SST warming by a factor of three. In the second phase, SST cools rapidly because (a) Qpen, is larger than Qnet, and (b) advective cooling is _85 Wm 2. A calculation using time-averaged heat fluxes and mixed layer depth suggests that diurnal variability of fluxes and upper ocean stratification tends to warm SST on subseasonal time scale. Buoy and satellite data suggest that a typical premonsoon intraseasonal SST cooling event occurs under clear skies and weak winds, when the ocean is gaining heat. In this respect, premonsoon SST cooling in the north Indian ocean is different from that due to MJO or monsoon ISO. As a follow-up to ARMEX, we use a short dataset from a field campaign in the premonsoon north Bay of Bengal to study diurnal variability of SST. In addition to the standard meteorological and hydrographic parameters measured from shipborne instruments and buoy sensors, we obtained a two-hourly record of subsurface sunlight profiles. Heat fluxes are seen to drive the SST warming during the day while both advection and entrainment/mixing are important during the night. The simple heat balance based on heat flux shows that it drives the diurnal cycle of SST, though ocean processes contribute towards night time cooling; this has been confirmed using the Price-Weller-Pinkel mixing model forced by heat flux and wind stress. A similar analysis for mixed layer salinity revealed that the salt balance in the region is dominated by advection rather than freshwater flux or entrainment/mixing. Buoy and satellite data show pronounced subseasonal oscillations of sea surface temperature (SST) in the summertime north Indian Ocean. The SST oscillations are forced mainly by surface heat flux associated with the active-break cycle of the south Asian summer monsoon. The input of freshwater (FW) from summer rain and rivers to the Bay is large, but not much is known about subseasonal salinity variability. We use 2002-2007 observations from Argo floats with 5-day repeat cycle to study the subseasonal response of temperature and salinity to surface heat and freshwater flux in the central Bay of Bengal and central Arabian Sea. Estimates of surface heat and freshwater flux are based on daily satellite data sampled along the float trajectory. We find that intraseasonal variability (ISV) of mixed layer temperature is mainly a response to net surface heat flux minus penetrative radiation during the summer monsoon season. In winter and spring, however, temperature variability appears to be mainly due to ocean processes rather than local heat flux. Variability of mixed layer freshwater content is generally independent of local surface flux (precipitation minus evaporation) in all seasons. There are occasions when intense monsoon rainfall leads to local freshening, but these are rare. The large subseasonal fluctuations observed in FW appear to be due to advection, suggesting that freshwater from rivers and rain moves in eddies or filaments. We have developed a new daily satellite-based heat flux dataset for the tropical Indian Ocean (30oE 120oE; 30oS 30oN); satellite data include surface air temperature and relative humidity from the Atmospheric Infrared Sounder (AIRS). On the seasonal scale (> 90 days) the flux compares reasonably well with climatologies and other daily data. On the subseasonal scale, our flux product has realistic behaviour relative to buoy data at validation sites. An important result is that ocean processes (advection, entrainment/detrainment, mixing at the base of the mixed layer) cool the tropical Indian Ocean SST by 8oC over the year. The largest contribution of ocean processes (_20oC SST cooling over the year) is in the western equatorial Indian Ocean. Ocean processes generally cool the upper ocean in all seasons and all regions, except in boreal winter, when they warm the north Indian Ocean. This is likely due to entrainment of warm sub-mixed layer water in regions of inversions. On subseasonal (2-90 days) scales, the contribution of air temperature and humidity to latent heat flux is roughly equal to the contribution from wind speed variability: Another interesting finding is that the contribution of air temperature and humidity increases away from the equator. One of the most important contributions of this thesis is the demonstration that tropical Indian Ocean SST has a coherent response to intraseasonal changes in heat flux associated with organised convection in the summer hemisphere. SST responds to flux in (i) the northeast Indian Ocean during May-October and (ii) the 15oS-5oN region during November-April. In the winter hemisphere and in regions with no organised convection, it is ocean processes and not fluxes which drive the subseasonal changes in SST. This result suggests that SST ISV feeds back to organise and sustain organised convection in the tropical atmosphere.

Decades of research have fostered a greater understanding of the environmental controls that drive tropical cyclone (TC) intensity change, yet the community has achieved only small improvements in intensity forecasting. Numerous environmental factors impact TC intensity, such as vertical wind shear and sea surface temperatures (SSTs), but little research has focused on establishing if SST change under the TC, or SST gradients, influence these intensity changes. This study investigated three methods to compute SST gradients. The first method calculated the SST change within fixed distances along the track. In the second and third methods, the SST was calculated over the distance traversed by the TC in two separate six-hour periods. By examining 455 24-hour weakening episodes in the eastern North Pacific, this study revealed that the first SST gradient method explained the highest 24-hour weakening variance for TCs located within SSTs at or lower than 26.5 degrees C.

No description available.

Around Sri Lanka and to the south of India sea surface temperatures (SST) are cooler compared to the surrounding region during summer monsoon. This region where SSTs are relatively cooler is known as the cold pool. Owing to its possible impact on monsoon variability, some studies have been carried out to understand the evolution of cold pool SST during this period. These studies suggest, coastal upwelling along southern coast of Sri Lanka and eastward advection of cooler water contributes to the decrease in SST during summer monsoon. However, the processes leading to the formation of cold pool, still, remain unknown. In this study, we have investigated the mechanism responsible for the formation and maintenance of southern Bay of Bengal (BOB) cold pool using high resolution satellite data, model simulations and in-situ observations for the year 2009. Our study reveals formation of cold pool is dominated by atmospheric processes, whereas oceanic processes dominate its maintenance. Cooling of SSTs during premonsoon and onset phase acts as a prerequisites for the formation of cold pool, which are linked to the reduction in Net Heat flux (NHFX) during theses periods. The changes in NHFX during premonsoon and onset phase are dominated by reduction in Short-wave (SW) radiation associated with strong convective activity over cold pool. Convective activity over the cold pool are associated with the northward movement of Maximum Cloud Zone (MCZ) that forms over Equatorial Indian Ocean (EIO) during these periods. SST within the cold pool after the steady increase during February-April months, cools first during premonsoon rain event and then during monsoon onset. Analysis of high resolution satellite data for the period 2003-2009 suggest that, these sequence of events occurs with minor amount of inter-annual variability. Lead-lag correlation also made it clear that SST response in 5 days to the corresponding variation in atmospheric processes. SST within the cold pool shows several intraseasonal cooling events during the summer mon-soon. Considering that rainfall above the cold pool is very low during the summer monsoon, these cooling events occurring within the summer should be necessary for maintaining the cold pool. The seasonal evolution of SST shows that it continues to decrease till the end of the summer monsoon. In-situ data collected during CTCZ field program in 2009, at two time series locations (TSL) and model simulations were used to determine the processes responsible for such cooling events. To estimate the contribution from advection to the observed SST tendency at fixed location, a measurement stratergy called ‘opertaion advection’ was used in this study. This stratergy involves measurement of oceanographic parameters along four edges from TSL directod along North, South, East and West for estimation of horizontal temperature gradients. Our results from SST cooling events captured by CTD at two fixed locations suggests that horizontal advection and entrainment dominate the SST evolution. Model temperature equation evaluated near the TSLs are convinient with the observations and suggest that atmospheric forcing is not responsible for intraseasonal cooling events.

O objetivo deste estudo foi analisar a variabilidade climática espectral da temperatura da superfície do mar, TSM, global associada a oscilações de 1-12 meses, 1-2 anos, 2-4 anos, 4-8 anos e 8-12 anos, entre1854 e 2014, e, as possíveis relações com a variabilidade climática na América do Sul. A análise espectral da TSM foi obtida com a aplicação da técnica de ondeletas a dados mensais. Em termos globais, as bacias tropicais do Pacífico Norte e Sul apresentam os sinais mais intensos da variância de TSM, em todas as faixas espectrais consideradas, e, portanto, valores mais próximos da média global para os trópicos, indicando a importância do oceano Pacífico no clima global. Nesta ordem, as bacias do Pacífico Sul, Pacífico Norte, Atlântico Norte, Indico e Atlântico Sul apresentam valores decrescente de variância da TSM. A análise da tendência linear ao longo do período considerado mostra que, globalmente, fenômenos tropicais com oscilações nas escalas de frequências mais altas, 1-12 meses, 1-2 anos e 2-4 anos, têm apresentado decréscimo de energia e que fenômenos com oscilações nas escalas de frequências mais baixas, 4-8 e 8-12 anos, têm apresentado aumento de energia, o que sugere a troca de energia entre fenômenos de alta e baixa frequência . As oscilações de 2-4 anos e de 4-8 anos na região equatorial do Pacífico são as que apresentam os maiores valores de energia, em especial nas regiões de Ninõ1+2, Niño3, Niño3.4 e Niño4. Os resultados permitem verificar que eventos fortes de El Niño sempre estiveram associados a sinais intensos da variância de TSM nas faixas espectrais de 2-4 anos e 4-8 anos e que os eventos mais fracos de El Niño estiveram associados à faixa de oscilações mais rápidas, 1-2 anos. O início do aumento do valor da variância de TSM para oscilações de 2-4 anos e 4-8 anos na região equatorial do Pacífico apresenta, em todos os casos, antecedência significativa em relação à ocorrência de um evento de El Niño forte, indicando a possibilidade de usar este sinal como preditor da ocorrência de eventos quentes de ENOS. A associação entre a variabilidade da variância espectral de TSM e a variabilidade climática na América do Sul foi verificada com base nos dados precipitação do GPCC, dados de vento das reanálises I e II do NCEP-NCAR e da reanálise do JRA-55. A análise de ondeletas da TSM tropical para a faixa de oscilações de 4-8 anos possibilitou a divisão do período todo em fases distintas: fases positivas, 1948 a 1960 e 1982 a 2003 e fases negativas, 1961 a 1981 e 2004 a 2014. Observou-se que as fases positivas e negativas apresentam um padrão bipolar da precipitação entre as regiões nordeste e sudeste da América do Sul, o que está associado a anomalias contrárias da circulação atmosférica em altos e baixos níveis sobre a região central do continente, constituindo um resultado inédito na área de climatologia. As fases positivas da variância de TSM para oscilações de 4-8 anos estão associadas a anomalias negativas e positivas de precipitação, respectivamente, sobre as regiões nordeste e sudeste da América do Sul enquanto que as fases negativas estão associadas a padrões contrários. O padrão do 4º modo da Análise de Componentes Principais aplicada aos dados de vento em 200 hPa contribui para explicar fisicamente o padrão bipolar da precipitação observado no setor leste do continente na escala decadal, por meio da propagação de ondas de baixa frequência entre o Pacífico Sul e a América do Sul. / The aim of this study is to analyze the global SST spectral climate variability for 1-12 month, 1-2 year, 2-4 year, 4-8 year, and 8-12 year oscillations, in the period from 1854 to 2014, and the possible relations with the climatic variability in South America. The spectral analysis of SST was obtained with the application of the wavelet technique to the monthly data. In global terms, the North and South Pacific basins show the most intense signs of SST variance in all the spectral ranges considered, and therefore, values closer to the global average, indicating the importance of the Pacific Ocean in the global climate. Then, in order of importance, come the basins of the South Pacific, the North Pacific, the North Atlantic, the Indian Ocean and the South Atlantic. The analysis of the linear trend throughout the period considered shows that globally within the tropical range, phenomena with oscillations in the scales of higher frequencies, 1-12 months, 1-2 years, and 2-4 years, have decreased energy and that phenomena with oscillations at lower frequency scales, 4-8 and 8-12 years, have presented increased energy through the course of time, suggesting energy exchange between high frequency phenomena and low frequency phenomena. The 2-4 year and 4-8 year oscillations in the equatorial Pacific region are those with the highest energy values, especially in the Nin1 + 2, Niño3, Niño3.4 and Niño4 regions. It is also possible to verify that strong El Niño events have always been associated with intense SST variance signals in the 2-4 year and 4-8 year spectral bands, and the weaker El Niño events were associated with the 1-2 year spectral bands. The beginning of the increase in the SST variance value for 2-4 year and 4-8 year oscillations in the equatorial region of the Pacific presents, in all cases, significant antecedence in relation to the occurrence of a strong El Niño event, indicating the possibility of using this signal as a predictor of the occurrence of hot ENSO events. The association between SST spectral variance variability and climatic variability in South America was verified based on GPCC precipitation data and wind data from NCEP-NCAR I and II reanalyses and of the JRA-55 reanalysis. The analysis of tropical SST wavelets for the 4-8 year oscillation range allowed the division of the whole period into distinct phases: positive phases, 1948 to 1960 and 1982 to 2003; and negative phases, 1961 to 1981 and 2004 to 2014. It was observed that positive and negative phases present a bipolar precipitation pattern between the Northeast and Southeast regions of the AS, which is associated with anomalies of atmospheric circulation at high and low levels over the central region of the continent, which is an unprecedented result area of climatology. The positive phases of the SST variance for 4-8 year oscillations are associated with negative and positive precipitation anomalies respectively over the northeast and southeast regions of South America while the negative phases are associated with contrary precipitation patterns. The 4th mode pattern of the Principal Component Analysis applied to wind data at 200 hPa contributes to physically explaining the bipolar pattern of precipitation observed in the eastern sector of the continent on the decadal scale by propagating low frequency waves between the South Pacific and South America.

Esta pesquisa tem como objetivo avaliar a relação existente entre o comportamento anual dos oceanos e o da vazão na Bacia do Rio São Francisco, Brasil, para o período de 1968 a 2004. Foram construídos modelos de regressão linear múltipla para simular o valor da vazão anual em Ponte da Taquara, Alto São Francisco, com base em índices climáticos e no valor médio da Temperatura da Superfície do Mar (TSM) em áreas específicas dos oceanos Pacífico e Atlântico. Os índices climáticos considerados foram a Oscilação Decadal do Pacífico (ODP), Indice de Oscilação Sul (IOS) e anomalias de TSM nas regiões de Niño. Os padrões oceânicos de correlação linear entre a TSM do Pacífico e a vazão dos postos do Alto São Francisco e o Médio São Francisco, indicam valores positivos em toda a costa oeste da América do Norte e do Sul e região equatorial e fortes sinais negativos na costa leste da Ásia e Austrália. Este padrão é bastante semelhante ao padrão espacial do primeiro modo obtido pela aplicação de análise multivariada à TSM no Oceano Pacífico, que é associado à Oscilação Multidecadal do Pacífico. A consideração de defasagem mensal no cálculo do coeficiente de correlação linear entre os valores de vazão e TSM indicam que a TSM dos meses mais próximos ao da vazão têm maior potencial para serem considerados como seus preditores. Observa-se a diminuição da correlação linear entre TSM do Pacífico e a vazão dos postos do Médio e Baixo São Francisco em relação aos postos do Alto São Francisco. O que sugere que o Oceano Pacífico apresenta maior influência na variabilidade da vazão nos postos localizados mais ao sul da Bacia do São Francisco. Por outro lado, observa-se o aumento dos valores do coeficiente de correlação linear no Atlântico Sul principalmente para a vazão dos postos do Médio e Sub-Médio, indicando possivelmente a maior influência do Oceano Atlântico na vazão de postos localizados mais a nordeste da bacia hidrográfica considerada. O padrão oceânico indicado pelos valores de correlação linear entre a TSM e os postos do Sub- Médio São Francisco indica a presença de um dipolo meridional, com anomalias negativas e positivas na bacia do Atlântico Sul tropical e subtropical. O IOS e ODP apresentam maior valor de correlação para a vazão observada no Alto e Médio São Francisco. As regiões selecionadas nos oceanos Pacífico, Atlântico e Índico e os índices Niño1+2, Niño 3 e Niño 4 para a construção do modelo linear para a simulação da vazão anual suavizada explicam 96% da variância total da vazão. No caso da vazão sem suavização as variáveis selecionadas pelo modelo elaborado explicam 52% da variância total. O padrão atmosférico anômalo associado aos dois primeiros subperíodos da vazão em Ponte da Taquara, de 1968 a 1978 e de 1979 a 1988, caracterizados em média por anomalias negativas e positivas, respectivamente, apresenta condições atmosféricas específicas às anomalias observadas da vazão. Em geral, anomalias negativas (positivas) de vazão em Ponte da Taquara são acompanhadas por ODP negativa, com anomalias negativas (positivas) de TSM no Pacífico Equatorial. / This research concerned to propose a valuation about the relationship between annual oceanic behavior and river outflow at São Francisco Hydrographic Basin, in Brazil, for the period from 1968 to 2004. Linear model based on multiple regression were built for annual river outflow at Ponte da Taquara, located at High São Francisco sub-basin. Climatic indexes and Sea Surface Temperature (SST) averages for selected areas over Pacific and Atlantic oceans were taken as independent variables in the modeling. Pacific Decadal Oscillation (PDO), Southern Oscillation Index (SOI) and SST anomalies at the Niño regions were also considered as independent variables in the modeling. The specific oceanic areas were selected through linear correlation calculation between river outflow at High São Francisco and SST. Oceanic patter represented by linear correlation between Pacific SST and river outflow at High São Francisco and Medium São Francisco shows positive values throughout the west coast of North and South America and the equatorial areas and, high negative values at oceanic areas to the east of Asia and Australia. This patter is quite similar to that obtained as the first mode of multivariate analysis applied over Pacific basin, and is related to the PDO. The consideration of temporal lag between SST river outflow monthly values showed that the smaller interval provide the best linear correlation. Linear correlation patter over Pacific is more significant for river outflow observed at the southern area of São Francisco Basin in relation to those located at northern areas. This aspect suggests that Pacific Ocean plays a more significant role to determination of river outflow observed at the south of the hydrographic basin. On the other hand, linear correlation values are greater at South Atlantic when river outflow for Sub-Medium São Francisco is considered. This result suggests that South Atlantic Ocean can play a greater role for the determination for climatic variability for river outflow observed at northern areas of São Francisco Basin. The oceanic correlation pattern for South Atlantic Ocean also shows a dipole mode, between tropical and subtropical latitudes, for fluvial stations located at the northern areas of the hydrographic basin. SOI and PDO present greater correlation values for river outflow observed at High and Medium São Francisco Basin. Ocean Pacific, Atlantic and Indian and the indexes Niño1+2, Niño 3 e Niño 4 variables, selected for the linear model elaboration to river outflow simulation, explain 96% of the total variance. In the case of not smoothed data, the variance explained by the linear model is equal to 52%. The atmospheric averaged patterns for the considered two first subperiods, from 1968 to 1978 and from 1979 to 1988, that are characterized by negative and positive river outflow anomalies at High São Francisco, present atmospheric conditions closely related to the observed river outflow anomalies. In general, river outflow negative (positive) anomalies at High São Francisco are related to negative PDO and SST negative anomalies (positive) at equatorial Pacific.

Vários estudos fornecem evidências de que os oceanos Atlântico e Pacífico desempenham papel significativo nas flutuações climáticas que ocorrem no Brasil. O objetivo desta pesquisa é avaliar a relação entre a temperatura da superfície do mar, TSM, dos oceanos Pacífico e Atlântico e a vazão de rios localizados no oeste do estado de São Paulo. Foram analisados 30 anos de dados, de 1979 a 2008. Os dados de vazão foram obtidos da Agência Nacional de Águas, os dados da temperatura da superfície do mar e radiação de onda longa emergente, do CDC/NOAA, e as variáveis climáticas (temperatura mínima, média e máxima, precipitação e umidade relativa) foram obtidos do INMET e referem-se aos dados observados na estação meteorológica da cidade de Presidente Prudente. Os resultados foram obtidos pela estimativa da correlação linear entre as séries mensais de vazão e dos dados climáticos com a temperatura da superfície do mar nos oceanos, com e sem defasagem temporal. Áreas com correlação alta e significativa foram encontradas no oceano Pacífico e Atlântico. Os padrões oceânicos obtidos para os quatro postos de vazão se assemelham entre si, sugerindo que a variabilidade climática dos postos é parecida. O padrão de ferradura no Oceano Pacífico Tropical está presente em todos os casos avaliados, assim como áreas meridionalmente adjacentes com sinais trocados no setor norte do Atlântico Norte. No Oceano Atlântico, as principais áreas de correlações linear foram encontradas no hemisfério sul, indicando valores positivos. As correlações entre a TSM e as variáveis climáticas (temperaturas, umidade relativa, precipitação e ROLE) também apresentaram correlações significativas no Pacífico Tropical, indicando o padrão de ferradura. O modelo estocástico construído para simulação da vazão trimestral, em Presidente Prudente, com base em regressão linear múltipla forneceu um ajuste com explicação da variância igual a 49%. O modelo construído considerando-se as variáveis oceânicas e continentais fornece uma explicação da variância igual a 69%. Tal resultado sugere que seja possível considerar apenas variáveis oceânicas na elaboração de um modelo prognóstico para a vazão trimestral. Os períodos com anomalias positivas de vazão estiveram associados a maior convergência (divergência) do ar em baixos (altos) níveis, à intensificação do movimento vertical ascendente e movimento vertical ascendente intensificado. / Several studies provide evidence that the Atlantic and Pacific oceans play a significant role inclimate fluctuations that occur in Brazil. The objective of this research is to evaluate the relationship between sea surface temperature, SST, on Pacific and Atlantic oceans, and the observed river outflow in the western state of Sao Paulo. We analyzed 30 years of data, from 1979 to 2008. The river outflow data were obtained from the National Water Agency, the data of sea surface temperature and emergent longwave radiation, from the CDC / NOAA, and climatic variables (minimum, mean and maximum temperature, precipitation and relative humidity) were obtained from INMET. The latter refers to observed data in the meteorological station of the city of Presidente Prudente. The results were obtained by estimating the linear correlation between monthly series of river outflow data, climate data and sea surface temperature in the oceans, with and without lag. Areas with high and significant correlations were found in the Pacific and Atlantic oceans. The ocean patterns obtained for the four river outflow stations resemble each other, suggesting that the variability of the climate stations is similar. The pattern of \"horseshoe\" in the Tropical Pacific Ocean is present in all cases investigated, as well as areas meridionally adjacent and presenting opposite signs at the northern of North Atlantic. In the Atlantic Ocean, the main areas of linear correlations were found at the southern hemisphere, indicating positive values. The correlations between SST and climatic variables (precipitation and ROLE) also presented significant correlations values on Tropical Pacific, depicting the horseshoe pattern. The stochastic model built to simulate the quarterly river outflow, in Presidente Prudente, based on multiple linear regression, provided a fit that explained 49% of river outflow variance. The built model considering oceanic and continental variables provides an explanation of 69%. This result suggests that it is possible to consider only oceanic variables in the development of prognostic models for quarterly river outflow atthe region.The periods with positive river outflow anomalies were associated with greater air convergence (divergence) at low (high) levels and intensified upward movement.

O trabalho aqui apresentado utiliza dados da fugacidade de CO2 (fCO2) coletados por onze cruzeiros oceanográficos no Oceano Atlântico Sudoeste (OAS) que fazem parte do banco de dados do SOCAT para analisar a variabilidade espacial da fCO2 e as principais variáveis relacionadas a suas variações. Foram utilizados dados do satélite AQUA para se estudar a fCO2 sobre os campos médios mensais de temperatura da superfície do mar (TSM) e concentração de clorofila. Também foram utilizados dados de reanálise para descrever os campos de vento e pressão atmosférica em superfície durante o período de cada cruzeiro. Através dos dados de vento em superfície foram calculados os campos de bombeamento de Ekman. Os resultados demonstram que a principal variável responsável pelas variações da fCO2 foi a TSM (em geral com coeficiente de correlação r>0,8) e que as distintas massas d'água na região apresentam diferentes fCO2, sendo que as massas d'água mais quentes apresentam valores mais elevados que as mais frias. As águas da Pluma do Rio da Prata apresentam uma fCO2 que chega a ser ate 1,5 vezes maior que as outras massas d'água. Descreve-se, pela primeira vez no OAS, a importância de se considerarem os padrões de vento em superfície (através do bombeamento de Ekman) e não somente os valores de TSM e concentração de clorofila para uma melhor análise da fCO2 em relação às massas d'água no OAS. / The work presented here uses CO2 fugacity data (fCO2) collected by eleven oceanographic cruises in the Southwestern Atlantic Ocean (SAO) that are part of the SOCAT database to analyze the spatial variability of the fCO2 and the main variables related to its variations. AQUA satellite data were used to study the fCO2 over the monthly averaged sea surface temperature (SST) and chlorophyll concentration fields. Reanalysis data were also used to describe the wind and surface atmospheric pressure fields during the period of each cruise. Through the surface wind data, the Ekman pumping fields were calculated. The results show that the main variable responsible for fCO2 variations was SST (in general with a correlation coefficient r> 0.8) and that the different water masses in the region present different fCO2, with the warmer water masses presenting higher values than the cold ones. The waters of the La Plata Plume present a fCO2 that is up to 1.5 times higher than the other water masses. It is described for the first time in OAS the importance of considering the surface wind patterns (through Ekman pumping) and not only the values of SST and chlorophyll concentration for a better analysis of fCO2 in relation to the water masses in the OAS.

Climate variability in the North Atlantic has been linked in part to the North Atlantic Oscillation (NAO). The NAO influences marine ecosystems in the northwestern Atlantic and the transport variability of the cold Labrador Current (LC). Understanding historic patterns and predicting future changes in LC transport require long-term and high-resolution climate records that are not available from instrumental data sets. This thesis presents the first century-scale sea surface temperature (SST)reconstructions from the Northwestern Atlantic using Mg/Ca ratios in the long-lived crustose coralline algae Clathromorphum compactum. which is characterized by a high Mg-calcite skeleton exhibiting annual growth increments. Results indicate strong correlations between interannual variations in Mg/Ca ratios and instrumental SST. The 131-year algal Mg/Ca record reveals NAO-type periodicities and evidence of past cold events and warming periods associated with basin-wide ecosystem shifts. Negative correlations between LC volume transport and algal Mg/Ca reflect the cooling influence of the LC on eastern Canadian shelf ecosystems.

Climate variability in the North Atlantic has been linked in part to the North Atlantic Oscillation (NAO). The NAO influences marine ecosystems in the northwestern Atlantic and the transport variability of the cold Labrador Current (LC). Understanding historic patterns and predicting future changes in LC transport require long-term and high-resolution climate records that are not available from instrumental data sets. This thesis presents the first century-scale sea surface temperature (SST)reconstructions from the Northwestern Atlantic using Mg/Ca ratios in the long-lived crustose coralline algae Clathromorphum compactum. which is characterized by a high Mg-calcite skeleton exhibiting annual growth increments. Results indicate strong correlations between interannual variations in Mg/Ca ratios and instrumental SST. The 131-year algal Mg/Ca record reveals NAO-type periodicities and evidence of past cold events and warming periods associated with basin-wide ecosystem shifts. Negative correlations between LC volume transport and algal Mg/Ca reflect the cooling influence of the LC on eastern Canadian shelf ecosystems.