| Summary: | Tese de mestrado, Geologia (Estratigrafia, Sedimentologia e Paleontologia) Universidade de Lisboa, Faculdade de Ciências, 2021 Located between the temperate and arid climate of Europe and North Africa, Iberia is a key location to study the past climatic dynamics, such as the variations in the North Atlantic Oscillation (NAO) which predominantly control the Iberian hydroclimate. This study focuses on the leaf wax n-alkanes signal (distribution and compound-specific isotopic signal) of Lake Peixão sedimentary record, which allowed for the first time a high resolution (decadal-scale) climate reconstruction of the last 2000 years in Serra da Estrela (Portugal). Our data shows that the n-alkane signal is dominated by odd long-chain compounds derived from higher plants of the watershed, with the C31 being the preferentially produced compound in the whole record. This pristine record shows that the variance of n-alkane concentration in the sediments has a remarkable teleconnection between solar variability and NAO. The inferred climate reconstruction based on the n-alkane signal shows a relatively stable lake ecosystem under dry conditions during the Roman Period (0 – 500 AD), where is assumed a predominant positive NAO phase and Grand solar maxima. From Dark Ages until Medieval Climatic Anomaly (500 – 1300 AD) the climate was generally milder and wetter, with the second period being particularly unstable under an inferred nonstationary behavior of the NAO. The Little Ice Age (1350 – 1850 AD) registered a first phase of cold and wet conditions and a second particularly cold (centered at 1700 AD) under a predominant negative NAO phase, Grand solar minima, and a strong influence of the polar front. These conditions abruptly changed at ca. 1880 AD, with the climate turning to the current warm and dry conditions, under stronger seasonality, and indications of anthropogenic footprint and possible lake eutrophication. This work reinforced the sensitive nature of the alpine ecosystems and contributed to the spatial coverage ...
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