No description available.

This thesis investigates how variations in the oxygen isotopic composition of lake waters in northern Fennoscandia are recorded in lake sediment archives, especially diatoms, and how these variations can be used to infer past changes in climate and atmospheric circulation. Results from analyses of the oxygen isotopic composition of lake water samples (δ18Olakew) collected between 2001 and 2006 show that δ18O of northern Fennoscandian lakes is mainly controlled by the isotopic composition of the precipitation (δ18Op). Changes in local δ18Op depend on variations in ambient air temperature and changes in atmospheric circulation that lead to changes in moisture source, vapour transport efficiency, or winter to summer precipitation distribution. This study demonstrates that the amount of isotopic variation in lake water δ18O is determined by a combination of the original δ18Olakew, the amount and timing of the snowmelt, the amount of seasonally specific precipitation and groundwater, any evaporation effects, and lake water residence time. The fact that the same isotope shifts have been detected in various δ18Olakew proxies, derived from hydrologically different lakes, suggests that these records reflect regional atmospheric circulation changes. The results indicate that diatom biogenic silica isotope (δ18Odiatom) records can provide important information about changes in atmospheric circulation that can help explain temperature and precipitation changes during the Holocene. The reconstructed long-term Holocene decreasing δ18Op trend was likely forced by a shift from strong zonal westerly airflow (relatively high δ18Op) in the early Holocene to a more meridional flow pattern (relatively low δ18Op). The large δ18Olakew depletion recorded in the δ18O records around ca. 500 cal yr BP (AD 1450) may be due to a shift to more intense meridional airflow over northern Fennoscandia resulting in an increasing proportion of winter precipitation from the north or southeast. This climate shift probably marks the onset of the so-called Little Ice Age in this region. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: In press. Paper 2: Submitted. Paper 5: In progress.

La mangrove de Guyane est caractérisée par un dynamisme spatial exceptionnel. Ce caractère découle de processus hydro-sédimentaires côtiers très intenses. Les objectifs de la thèse ont été de : (1) quantifier la dynamique spatiale de l'écosystème mangrove à l'échelle régionale et multi-décennale par l'analyse de données d'archives issues de la télédétection ; (2) tester l'hypothèse selon laquelle le climat océanique serait à l'origine de cette dynamique en évaluant les corrélations avec des séries temporelles de données atmosphériques et d'états de surface de l'océan ; (3) quantifier les conséquences de cette dynamique spatiale sur le stockage du carbone en mangrove. Les résultats ont montré qu'environ 15 000 ha de mangrove fluctuent à l'échelle multi-décennale en opposition avec les phases de l'Oscillation Nord Atlantique (NAO), principal mode de variabilité atmosphérique en Atlantique Nord. Le lien est opéré par l'intermédiaire des vagues océaniques dont l'énergie est modulée par les phases de la NAO. L'étude suggère que la diminution des surfaces de mangrove est la conséquence de périodes où les vagues sont puissantes (phase NAO+), ce qui favorise l'érosion côtière, la remise en suspension des sédiments et leur transport le long de la côte. Au contraire, les périodes où les vagues sont faibles (phase NAO-) favorisent le dépôt des sédiments, ce qui est à l'origine de l'expansion des surfaces de mangrove. Les résultats montrent que l'alternance entre des périodes d'expansion et de retrait génère une mosaïque d'âges de mangrove qui détermine la capacité de stockage du carbone par l'écosystème. A partir de ce dernier résultat, l'étude suggère qu'au cours du temps la mangrove puisse alternativement passer d'une fonction de puis à celle de source de carbone pour l'océan côtier et l'atmosphère. / Mangroves in French Guiana are characterized by their spatial dynamism. This specificity is the result of intense coastal sedimentary processes. The goals of this study are to: (1) quantify mangrove spatial dynamics on a regional level and a multi-decadal timescale using archives of remote sensing images; (2) test the hypothesis of the role played by the atmosphere using correlations with time series of atmospheric and ocean surface reanalysis datasets; (3) quantify consequence of this spatial dynamism on coastal carbon storage. Results showed that approximatively 15 000 ha of mangroves fluctuate on a multi-decadal timescale in opposition to the North Atlantic Oscillation (NAO) phases, the main mode of atmospheric multi-decadal variability in the North Atlantic. This relation is operated by ocean waves whose energy is modulated by NAO phases. The study suggests that, on the one hand, decrease of mangrove surface areas is due to periods of high wave energy (NAO+) which favour coastal erosion and mangrove retreat, sediment resuspension and transport. On the other hand, the study suggests that periods of low wave energy (NAO-) favour sediment deposition on the coast and is at the origin of mangrove surface area expansion. Results also showed that alternation between phases of retreat and expansion generates the demographic structure of mangrove ages, which determines the mangrove carbon storage capacity. The study finally suggests that through time mangrove can switch from a source to a sink of carbon, and vice and versa, for the ocean and the atmosphere.

O Homem é parte integrante do sistema Ambiental. O ambiente cria impactos Nele e por sua vez ele também pode provocar impactos no Ambiente. O objetivo da tese foi identificar qual a intensidade e freqüência do impacto que a poluição atmosférica e a variabilidade das variáveis meteorológicas na saúde da população da Área Metropolitana do Porto (Portugal), através de um estudo epidemiológico ecológico. Escolheu-se o período de 2002 a 2005 para estudar um conjunto de cidades que contam com espaços urbanos, suburbanos e industriais mesclados, perto do litoral Atlântico com clima Mediterrânico. Usando como métodos a análise descritiva e multivariada (ACP), de correlação e regressão múltipla (RM), assim como índices de conforto térmico (ID, H, Te e Tev), trabalharam-se dados de admissões hospitalares (4 hospitais públicos) de doenças cardiovasculares (DCV) (401-405, Hipertensão; 410-414, DCV Isquêmica, 426-428, Insuficiência Cardíaca) e respiratórias (490-496, Asma/Bronquite; 500-507, Pneumoconioses), informações meteorológicas do Instituto de Meteorologia de Portugal (Temperatura, Umidade, Precipitação e Pressão) e valores diários e mensais do índice de Oscilação do Atlântico Norte (OAN), da NOAA, assim como, saídas de normais de pressão e médias de velocidade de vento do modelo NOAA e de 10 estações fixas de qualidade do ar pertencentes à Agencia Portuguesa do Ambiente (O3; NO2, NO, CO, SO2, PM10, PM2,5). Identificaram-se alguns períodos de temperaturas elevadas (38°C) durante o verão e inversões térmicas durante o inverno (2004/05), as quais criaram situações de estresse térmico por calor e muito frio (dos 1461 mais de 930 dias -24°C< TEv tmin Urmáx vmáx < 0°C), por um lado, e aumento da poluição, por outro. Esse aumento da poluição contribuiu para se observar maior número de casos por doenças respiratórias por Asma/bronquite (lag 3 dias durante inverno 2004/05 correlação com PM2,5=0,33), doenças Cardíacas Hipertensivas (regressão multivariada para Primavera, para PM10 com Beta=0,80, R2ajustado=0,076), e Insuficiências Cardíacas (regressão para Outono NO2 Beta = 0,42 com R2ajustado= 0,060). Encontrou-se também relação significativa e forte entre a variabilidade da Oscilação do Atlântico Norte (OAN) e de alguns poluentes durante o inverno (ex: correlação PM10=0,71, em 2003; PM2,5= 0,91, em 2005; SO2=0,45, em 2004). Uma importante conclusão, também sugerida por outros autores, é que as mudanças climáticas podem modificar a intensidade e regularidade da OAN, afetando assim a circulação atmosférica o que terá impacto direto na dispersão dos poluentes em pequena escala e conseqüentemente irá influenciar a saúde publica. / Humans are part of environmental system. Environment impacts on Humans and we so can impact on earth ecosystems. The thesis aims identify the intensity and frequency of air pollution and meteorological impact on Porto Metropolitan Area (PMA) public health, although a ecological epidemiological study. The 2002- 2005 period was select to study climatologically Mediterranean seaside cities with typical urban, suburban and industrial mixed spaces. The statistical methods used were: descriptive and multivariate (ACP) analyze, correlation and multiple regression, as well as, discomfort indices (ID, Te, Tev, H). Data set from 3 different institutions was analyzed: admission from 4 public hospitals referent to heart (401-405, Hypertension; 410-414, Ischemic cardiac, 426-428, Heart Insufficiency) and respiratory diseases (490-496, Asthma/Bronchitis; 500-507, Pneumoconioses), meteorological information from Meteorological Institute of Portugal.(Temperature, Humidity, Precipitation, Wind speed, Pressure) and daily and monthly North Atlantic Oscillation index values, from NOAA, as well as, pressure daily normal and wind velocity daily mean NOAA model output and from 10 fixed air quality stations (Environmental Portuguese Agency) the pollutants (O3; NO2, NO, CO, SO2, PM10, PM2,5) time series. Some high temperature (38°C) periods was identified during summertime and thermal inversions in the wintertime (2004 and 2005), which provoked stress for heat and cold (from 1461 days, 930 days the thermal sensation was -24°C< TEv tmin Urmáx vmáx < 0°C), and pollution increase. The air pollution increased the hospital admissions for respiratory diseases special Asthma/bronquitis (lag 3 days during 2004/05 Winter correlation PM2.5= 0.33), Cardiac Hypertension (Spring multivariate regression Beta= 0.80, R2ajusted= 0.076), and Heart insufficiency (Autumn multivariate regression NO2 Beta = 0.42 with R2ajustaded= 0.060). Significant and strong association was found between North Atlantic Oscillation (NAO) and some pollutants during Wintertime (eg.: correlation PM10=0.71, 2003; PM2.5=0.91, 2005; SO2=0.45, 2004). ). It is important to notice that some studies have already suggested that climate change can modify the intensity and regularity of the NAO, affecting the atmospheric general circulation and it could have a direct impact on pollutants dispersion in small scale and on public health.

The North Atlantic Oscillation (NAO) is one of the main components of atmospheric circulation variability within the middle and high latitudes of the Northern Hemisphere and largely affects winter weather in northeastern United States. This study examined the most recent decadal trend of the NAO as well as its influence on snowfall totals and storm track variability in the northeast U.S. over the previous 50-year period. Previous research has indicated greater snowfall totals in the Northeast during NAO negative phases due to repeated polar outbreaks. Nonetheless, past research has also shown connections between the NAO positive phase and active winter seasons in this region. This study provides insight on how both positive and negative NAO phases can produce significant snowfall in the Northeast. Statistical and graphical analysis were completed to assess the relationship between the NAO and seasonal snowfall (NDJFM) from 1961-2010 for stations within the Northeast (Virginia to Maine). In addition, two case studies of recent winter events with differing NAO phases were evaluated to provide insight on how both NAO phases can produce significant snowfall in the Northeast. The statistical analysis revealed inverse relationships between the NAO negative phase and seasonal snowfall. The composite analysis indicated an average positive NAO pattern from 1961-2010, yet the NAO negative years produced higher frequency of snowfall in the Northeast. The case studies highlighted variations in storm track and snowfall distribution of the two winter events in differing phases. This study shows that snowfall can occur in particular regions of the Northeast regardless of the NAO phase which has important implications for forecasters. This research also provides the necessary information to complete the most recent decadal trend of the NAO and determine its average pattern. The update of this record will assist climatologists and weather forecasters in predicting future northeast U.S. winter storms. / Department of Geography

Four continuous high-resolution peat records for the Holocene have been reconstructed across a ~300km transect from Shebster in Caithness to Yell in the Shetland Isles. These records describe the nature and extent of North Atlantic climate changes inferred from indicators of storminess and minerogenic aeolian dust, and are supported by radiogenic isotope analysis, tephrochronology and radiocarbon dating. The environmental changes at all four sites displays a significant degree of synchrony in response to changes in the position of the polar front jet (PFJ) stream and the phase of the North Atlantic Oscillation (NAO). Bromine concentrations in the peat, derived from sea spray, are used to reconstruct storm frequency and storm intensity, and mire surface wetness is used as an indicator of longer-term climate shifts. The results suggest a strong link between positive phases of the NAO and storminess. Subtle differences between the bromine concentrations and the mire surface wetness suggest that high intensity but perhaps less frequent periods of storminess are not necessarily associated with a wetter climate. Atmospheric minerogenic dust concentrations are used to reconstruct large-scale climate changes across the wider North Atlantic region. The results suggest a sympathy between dust activity and periods of glacial advance and a negative index of the NAO. Radiogenic isotope analysis suggests that the smallest particles may originate from Iceland.

O Homem é parte integrante do sistema Ambiental. O ambiente cria impactos Nele e por sua vez ele também pode provocar impactos no Ambiente. O objetivo da tese foi identificar qual a intensidade e freqüência do impacto que a poluição atmosférica e a variabilidade das variáveis meteorológicas na saúde da população da Área Metropolitana do Porto (Portugal), através de um estudo epidemiológico ecológico. Escolheu-se o período de 2002 a 2005 para estudar um conjunto de cidades que contam com espaços urbanos, suburbanos e industriais mesclados, perto do litoral Atlântico com clima Mediterrânico. Usando como métodos a análise descritiva e multivariada (ACP), de correlação e regressão múltipla (RM), assim como índices de conforto térmico (ID, H, Te e Tev), trabalharam-se dados de admissões hospitalares (4 hospitais públicos) de doenças cardiovasculares (DCV) (401-405, Hipertensão; 410-414, DCV Isquêmica, 426-428, Insuficiência Cardíaca) e respiratórias (490-496, Asma/Bronquite; 500-507, Pneumoconioses), informações meteorológicas do Instituto de Meteorologia de Portugal (Temperatura, Umidade, Precipitação e Pressão) e valores diários e mensais do índice de Oscilação do Atlântico Norte (OAN), da NOAA, assim como, saídas de normais de pressão e médias de velocidade de vento do modelo NOAA e de 10 estações fixas de qualidade do ar pertencentes à Agencia Portuguesa do Ambiente (O3; NO2, NO, CO, SO2, PM10, PM2,5). Identificaram-se alguns períodos de temperaturas elevadas (38°C) durante o verão e inversões térmicas durante o inverno (2004/05), as quais criaram situações de estresse térmico por calor e muito frio (dos 1461 mais de 930 dias -24°C< TEv tmin Urmáx vmáx < 0°C), por um lado, e aumento da poluição, por outro. Esse aumento da poluição contribuiu para se observar maior número de casos por doenças respiratórias por Asma/bronquite (lag 3 dias durante inverno 2004/05 correlação com PM2,5=0,33), doenças Cardíacas Hipertensivas (regressão multivariada para Primavera, para PM10 com Beta=0,80, R2ajustado=0,076), e Insuficiências Cardíacas (regressão para Outono NO2 Beta = 0,42 com R2ajustado= 0,060). Encontrou-se também relação significativa e forte entre a variabilidade da Oscilação do Atlântico Norte (OAN) e de alguns poluentes durante o inverno (ex: correlação PM10=0,71, em 2003; PM2,5= 0,91, em 2005; SO2=0,45, em 2004). Uma importante conclusão, também sugerida por outros autores, é que as mudanças climáticas podem modificar a intensidade e regularidade da OAN, afetando assim a circulação atmosférica o que terá impacto direto na dispersão dos poluentes em pequena escala e conseqüentemente irá influenciar a saúde publica. / Humans are part of environmental system. Environment impacts on Humans and we so can impact on earth ecosystems. The thesis aims identify the intensity and frequency of air pollution and meteorological impact on Porto Metropolitan Area (PMA) public health, although a ecological epidemiological study. The 2002- 2005 period was select to study climatologically Mediterranean seaside cities with typical urban, suburban and industrial mixed spaces. The statistical methods used were: descriptive and multivariate (ACP) analyze, correlation and multiple regression, as well as, discomfort indices (ID, Te, Tev, H). Data set from 3 different institutions was analyzed: admission from 4 public hospitals referent to heart (401-405, Hypertension; 410-414, Ischemic cardiac, 426-428, Heart Insufficiency) and respiratory diseases (490-496, Asthma/Bronchitis; 500-507, Pneumoconioses), meteorological information from Meteorological Institute of Portugal.(Temperature, Humidity, Precipitation, Wind speed, Pressure) and daily and monthly North Atlantic Oscillation index values, from NOAA, as well as, pressure daily normal and wind velocity daily mean NOAA model output and from 10 fixed air quality stations (Environmental Portuguese Agency) the pollutants (O3; NO2, NO, CO, SO2, PM10, PM2,5) time series. Some high temperature (38°C) periods was identified during summertime and thermal inversions in the wintertime (2004 and 2005), which provoked stress for heat and cold (from 1461 days, 930 days the thermal sensation was -24°C< TEv tmin Urmáx vmáx < 0°C), and pollution increase. The air pollution increased the hospital admissions for respiratory diseases special Asthma/bronquitis (lag 3 days during 2004/05 Winter correlation PM2.5= 0.33), Cardiac Hypertension (Spring multivariate regression Beta= 0.80, R2ajusted= 0.076), and Heart insufficiency (Autumn multivariate regression NO2 Beta = 0.42 with R2ajustaded= 0.060). Significant and strong association was found between North Atlantic Oscillation (NAO) and some pollutants during Wintertime (eg.: correlation PM10=0.71, 2003; PM2.5=0.91, 2005; SO2=0.45, 2004). ). It is important to notice that some studies have already suggested that climate change can modify the intensity and regularity of the NAO, affecting the atmospheric general circulation and it could have a direct impact on pollutants dispersion in small scale and on public health.

A variety of anthropomorphic and environmental stresses are threatening the existence of all seven species of sea turtles. There is growing evidence that alterations in surface waters and sediment temperatures are negatively impacting reproductive success of loggerhead sea turtles (Caretta caretta). Fluctuations in water temperature associated with localized climate oscillations heavily alter the food web dynamics of the ocean. Feeding conditions are expected to be a critical factor in determining body mass and productivity for breeding seasons. An increase in regional temperatures could lead to prolonged reduction in food sources, as well as reduced nesting and recruitment. Loggerhead sea turtle nesting data from 1995-2011 werre compared with the average yearly North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO) which are important climatic events impacting the SST in the Atlantic Ocean. Because El Niño Southern Oscillation (ENSO) is a global event, it was proposed that turtles in the Atlantic may follow a similar trend. ENSO was quantified using Oceanic Nino Index (ONI). Analysis of loggerhead sea turtle nest frequencies from the years 1995-2011 in comparison to seasonal climate changes showed a significant inverse relationship between the detrended loggerhead nests and average yearly NAO when lagged two years, suggesting loggerheads may spend years prior breeding obtaining optimum body mass to increase successful reproduction. The detrended nesting data showed a tendency toward higher occurrence of nests during La Niña years while nest frequencies decreased during El Niño year; when the yearly detrended loggerhead nesting data was compared with the average yearly ONI; showing a significant inverse relationship without a lag. This may also suggest a relationship between changes of productivity of the ocean influenced by smaller scale climate changes and loggerhead nest frequencies.

The simultaneous occurrences of several extreme events, known as compound extremes, are often associated with greater impact than univariate extremes. Flooding and windstorms are widespread hazards in Europe which can lead to severe property damage and fatalities. During winter, extreme wind and precipitation often co-occur, since they are associated with a common driver, namely extratropical cyclones. In this project, the occurrences of compound wind and precipitation events in Europe are investigated using the ERA5 reanalysis dataset. The analysis covers the years 1979-2019 with a focus on boreal winter. Areas that experience the highest occurrence of compound wet-windy extremes are the west coast of Norway, the Iberian peninsula, parts of central Europe, and southeast of the Black Sea. A few case studies are discussed with the purpose to give an idea of the magnitude of possible impacts. Further, the relationship between extreme wind and precipitation events and the North Atlantic Oscillation (NAO) is presented. During days with positive NAO, extreme precipitation and wind events occur in the central and northern parts of Europe while the negative phase brings extreme wind and precipitation to the southern parts of Europe. Lastly, a short analysis to discover changes in the occurrences of compound precipitation and wind events for the two periods 1979-1999 and 2000-2019 is performed. The result showed no clear changes. The number of compound extremes does not seem to vary for the two periods. / Olika extrema väderhändelser som sammanfaller orsakar ofta större skada än enskilda extrema händelser på många håll i samhället. Översvämningar och vindstormar är vanligt förekommande i Europa och kan leda till kostsamma skador och dödsfall. Extrema vind-och nederbördshändelser sammanfaller vanligen under vintern eftersom de båda ofta orsakas av Nordatlantiska cykloner, som är vanligast under den årstiden. I detta projekt kartläggs sammanfallande vind- och nederbördshändelser i Europa under vintermånaderna december-februari, med hjälp av ERA5 reanalysdata för åren 1979-2019. Områden med relativt hög förekomst av sammanfallande vind- och nederbördshändelser är Norges västkust, Iberiska halvön, delar av Centraleuropa och östra Turkiet. Några fallstudier kopplade till dessa områden är diskuterade för att ge en uppfattning om konsekvenserna av dessa sammanfallande händelser. Eventuella kopplingar mellan sammanfallande vind- och nederbördshändelser och den Nordatlantiska Oscillationen (NAO) är också undersökt. Under den positiva fasen av NAO sker extrema nederbörd- och vindhändelser i norra och centrala delar av Europa medan den negativa fasen ger extrem vind och nederbörd i de södra delarna av Europa.En kort analys för undersöka om förekomsten av extrema sammanfallande händelser har ändrats genomfördes genom att jämföra andelen sammanfallande händelser under de två perioderna 1979-1999 och 2000-2019. Ingen betydande förändring i andelen sammanfallande händelser mellan dessa perioder hittades.

No description available.