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Authors
Abstract(s)
As alterações climáticas e as suas consequências são um dos temas dominantes na atualidade. Uma das consequências mais evidentes do aquecimento global é a
tendência de subida do nível médio do mar (NMM), associada à fusão dos glaciares
nas regiões polares e à expansão térmica da água dos oceanos. Esta tendência tem
vindo a ser estudada desde há várias décadas a nível global, utilizando séries maregráficas longas e, mais recentemente, outros métodos de observação, por exemplo
altimetria por satélite.
O Instituto Hidrográfico (IH) desenvolve trabalhos dedicados ao estudo da
subida do nível médio do mar em colaboração com entidades nacionais e internacionais. Neste trabalho estendem-se os estudos já efetuados, no IH, sobre a subida do
nível do mar utilizando modelos de regressão e modelos de séries temporais. Também
se apresentam as tendências de subida do nível médio do mar, as flutuações devidas
a fatores sazonais, e ainda se efetuam previsões da tendência de subida, através da
análise e processamento de três séries de registos maregráficos. Neste trabalho foram
utilizados registos maregráficos dos portos de Viana do Castelo (compreendidos entre os anos 1984 e 2015), Sines (compreendidos entre os anos 1997 e 2020) e Funchal
(compreendidos entre os anos 2005 e 2020) devido à sua localização e importância.
Os resultados obtidos nesta dissertação, evidenciam acentuadas variações
anuais e semianuais, e a existência de uma subida generalizada do NMM na costa
portuguesa. A série de registos de Viana do Castelo apresenta uma tendência de
subida de 1,97 mm/ano, enquanto que, as séries de Sines e Funchal, apresentam
valores de 4,27 mm/ano e 4,03 mm/ano, respetivamente. Se as condições atuais
forem mantidas, podemos antever que, até ao final do século, o NMM esteja, aproximadamente, 43 cm superior ao atual, no pior dos três cenários analisados.
Climate change and the associated consequences are one of the most dominant themes of our time. One of the most obvious consequences of global warming is the mean sea level rise, associated with melting glaciers in the polar regions and the thermal expansion of ocean water. This trend has been studied for several decades at the global level using long tide gauge series and, more recently, with different observation methods like satellite altimetry. The Portuguese Hidrographic Institute has been developping studies on the sea level rise in collaboration with national and international entities. This work seeks to extend the studies already carried out by the Portuguese Hidrographic Institute on the mean sea level rise, using regression and time series models. Following this, efforts are made to present the rising trend of the mean sea level, the periodic fluctuations due to seasonal factors, and also to make forecasts of the rising trend, through the analysis and processing of three series of tide gauge records. This work used tide gauge records from the ports of Viana do Castelo (data between 1984 and 2015), Sines (data between 1997 and 2020) and Funchal (data between 2005 and 2020) due to their location and importance. The results obtained in this dissertation, show a pronounced annual and semi-annual variations, as well as the existence of a generalized rise in the mean sea level along the Portuguese coast. The series of records from Viana do Castelo present a rising trend of 1,97 mm/year. As for, the series of Sines and Funchal, it, shows significantly higher values, respectively, 4,27 mm/year and 4,03 mm/year. If the predictions made do not change considerably we can expect that by the end of the century, the mean sea level will be, approximately, 43 cm above the present, in the worst of the three scenarios analysed.
Climate change and the associated consequences are one of the most dominant themes of our time. One of the most obvious consequences of global warming is the mean sea level rise, associated with melting glaciers in the polar regions and the thermal expansion of ocean water. This trend has been studied for several decades at the global level using long tide gauge series and, more recently, with different observation methods like satellite altimetry. The Portuguese Hidrographic Institute has been developping studies on the sea level rise in collaboration with national and international entities. This work seeks to extend the studies already carried out by the Portuguese Hidrographic Institute on the mean sea level rise, using regression and time series models. Following this, efforts are made to present the rising trend of the mean sea level, the periodic fluctuations due to seasonal factors, and also to make forecasts of the rising trend, through the analysis and processing of three series of tide gauge records. This work used tide gauge records from the ports of Viana do Castelo (data between 1984 and 2015), Sines (data between 1997 and 2020) and Funchal (data between 2005 and 2020) due to their location and importance. The results obtained in this dissertation, show a pronounced annual and semi-annual variations, as well as the existence of a generalized rise in the mean sea level along the Portuguese coast. The series of records from Viana do Castelo present a rising trend of 1,97 mm/year. As for, the series of Sines and Funchal, it, shows significantly higher values, respectively, 4,27 mm/year and 4,03 mm/year. If the predictions made do not change considerably we can expect that by the end of the century, the mean sea level will be, approximately, 43 cm above the present, in the worst of the three scenarios analysed.
Description
Keywords
modelos de séries temporais nível médio do mar registos maregráficos sazonalidade tendência do nível do mar