Estudio de la variabilidad climatica rapida en el atlantico norte subtropical durante el ultimo periodo glacial a partir de biomarcadores

Resumen

The last glacial abrupt climate episodes, known as Dansgaard/Oeschger (D/O) and Heinrich events (HE), were documented in ice, marine and continental deposits from different world regions, especially in the northern hemisphere. However, the triggering mechanisms and climatic impact of these rapid oscillations are still poorly understood. Most studies were centred in the northern and eastern North Atlantic and adjacent continents, whereas few works have involved western and central regions of subtropical North Atlantic. The aim of this Thesis is the study of the climate variability at millennial time-scale in the subtropical North Atlantic during the last glacial period (Marine Isotope Stage 3), in particular in the latitudinal band 30ºN-40ºN that has been much less studied. For this purpose, two marine cores located in western and central subtropical North Atlantic were analysed and compared with different paleoclimatic records obtained in nearby marine and ice cores. The study is using the organic molecules as source of information. Sea surface temperature records derived from the distribution of the C37 alkenones have been obtained in both studied cores. In addition, odd carbon numbered n-alkanes (C23-C33) and even carbon numbered n-alkan-1-ols (C20-C30) have been determined in the western North Atlantic sediments for the reconstruction of the inputs of continental organic material from North America. Comparison with other paleoclimatic records provided a general vision of the abrupt climatic and oceanographic changes that occurred in the subtropical North Atlantic. This approach has allowed the description of the hydrological changes in western and central regions between 60,000 years before present and the deglaciation. Additionally, changes in wind regime in the western region have been assessed for the period 30,000-60,000 years before present.