Estudi dels canvis climatics a l'ocea indic tropical i subtartic amb biomarcadors

Resumen

During the last decade, the scientific community has recognized the importance of the tropical regions in the dynamic processes that control the global climate change. These regions are considered probable triggers of the changes observed at higher latitudes. On the other hand, since the marine sediments located in tropical oceans are not under the direct influence of continental ice sheets formed during glacial periods, they provide a continuous record of the climatic variations in the Earth. However, it is not well understood what is the specific role of tropical regions for the climate changes at submillennial scale because of the great lack of studies at high resolution in these areas. In addition, ice core records from Antarctica and sea surface temperature recorded in several marine sediment cores from the Southern Hemisphere, show different climatic patterns and time leads when compared with the well-known variations in the Northern Hemisphere (Heinrich and Dansgaard-Oeschger events). To clarify the role of southern tropical regions in global climate change at submillennial scale, we have studied the distribution of marine and terrestrial biomarkers at high resolution in two marine sediment cores from the Indian Ocean. First, the gravity core MD98-2165 (9º39'S, 118º20'E, 2100 m water depth, 42.3 m long) which was collected in the South-east Indonesian region. This area is characterized by having the highest sea surface temperatures in the West Pacific Warm Pool and a high convective activity, both influencing the distribution of moisture over a large region of the earth's surface. Second, the gravity core MD00-2374 (46º2'S, 96º29'E, 3320 m water depth, 42.46 m long), that was selected as a reference for mid-latitudes in the southern hemisphere and is strategically situated to evaluate the connections with tropical regions and with Antarctica in warm and cold periods, respectively. The observed distributions of terrestrial biomarkers (C23-C33 n-alkan