Reconstrucción paleoclimática de los últimos 420 años en el Estrecho de Sicilia

Trabajo final presentado por Sara Cobacho Jiménez para el Máster en Oceanografía y Gestión del Medio Marino de la Universitat de Barcelona (UB) y la Universitat Politècnica de Catalunya (UPC), realizado bajo la dirección del Dr. Carles Pelejero Bou y de la Dra. Eva Calvo Costa del Institut de Ciències del Mar (ICM-CSIC).-- 33 pages, 10 figures, 1 tableThe Mediterranean Sea is a semiclosed basin connected to the Atlantic Ocean through the Strait of Gibraltar. It is composed of two main basins, west and east, which are connected through the Strait of Sicily. Climatic variability of this region is closely related to Atlantic Ocean changes, with a specific pattern of surface seawater temperature and salinity progressively increasing from west to east. Several studies have used molecular biomarkers in paleoceanographic reconstructions in the Mediterranean Sea but, there are not yet publications with sea surface temperature (SST) reconstructions from the UK’37 index derived from long chain alkenones in the Strait of Sicily on glacial – interglacial time-scales. In this MSc. thesis, UK’37 index derived temperatures and a range of molecular biomarkers have been analyzed to reconstruct past SSTs, continental inputs and primary productivity over the last 420 kyr, and comparisons with records from the Alboran Sea and Gulf of Lions have been made. Our record, which thus covers from nearly MIS 12 to MIS 1, shows the typical glacial/interglacial SST oscillations, with values comparable to those reconstructed in the Alboran Sea and the Gulf of Lions, but with slightly higher absolute values which agree with the progressive warming that surface waters experience during the movement from the Strait of Gibraltar, through the African Margin until the Central Mediterranean. Regarding the terrigenous markers, the record of n-alcohols is better for interpretations than that of the n-alkanes, since those seem to exhibit strong influence or contamination from reworked materials. Alcohol concentrations oscillate in a very similar way to brasicasterol, indicating a possible linkage between continental inputs, rich in Fe and Si, and diatoms productivity through enhanced fertilization. Alkenone concentrations display maximum values at periods different to those of brasicasterol, so both algae seem to have proliferated at different periods of time. During times with important continental inputs and water stratification diatoms seem to expand. Instead, coccolithophores productivity seems to be enhanced more during glacial – interglacial transitions. Interestingly, some of the peaks in the marine markers match the timing of sapropels. Sapropel 10, for example, matches the highest peak in the alkenone profile. Other younger sapropels match instead brasicasterol peaks, indicating that the peculiar marine conditions during sapropels were manifested in the Central Mediterranean in the form of high production but with different populations of phytoplankton, with an alternance between coccolitophores and diatomsPeer Reviewe