Report for the scientific sojourn at the Institute of mineralogy and geochemistry of the University of Lausanne, Swiss, from 2007 to 2009. 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. To clarify the role of southern tropical regions in global climate change at submillennial scale, we have studied the distribution and the carbon isotopic composition of marine and terrestrial biomarkers at low resolution in a marine sediment 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. The observed distributions of terrestrial biomarkers (C23-C33 n-alkanes and C20-C32 n-alkan-1-ols) are typical of higher plant lipids that arrive to the ocean by aeolian transport. In both cores, the most abundant homologues are the C31 alkane and the C28 or C32 alkan-1-ol. During glacial periods, the C32 alkan-1-ol is the most important homologue, suggesting an expansion of C4 tropical plants associated to arid conditions. The carbon isotope composition of these lipids allows distinguishing between the different photosynthetic pathways and corroborates the possible origin of these lipids.

Durant lfultima decada, la comunitat cientifica ha reconegut que les zones tropicals juguen un paper clau en els processos dinamics que controlen el canvi climatic global, probablement com a desencadenant dels canvis succeits en altes latituds. A mes a mes, els sediments dels oceans tropicals, en trobar-se fora de lfimpacte directe de les plaques de gel continentals creades a durant les glaciacions, proporcionen un registre continu de les variacions climatiques del planeta. Malgrat tot, encara hi ha moltes incognites sobre el paper especific de les zones tropicals, especialment pel que fa a les variacions brusques suborbitals, degut als pocs registres dfalta resolucio estudiats en aquestes arees que abastin varis cicles glacial/interglacial. A mes a mes, els registres de gel de lfAntartida i reconstruccions de temperatures superficials de mar en testimonis de sediment mari de lfhemisferi sud mostren unes variacions molt diferents i amb cert desfasament temporal a les ja ben conegudes de lfhemisferi nord (tal com els episodis Dansgaard-Oeschger i els esdeveniments Heinrich). Lfestudi a alta resolucio de dos testimonis de sediment mari de lfOcea Indic, un situat a la zona tropical i un altre a la sub-antartica emprant biomarcadors combinats a alta resolucio (com per exemple, alquenones C37, n-alcans C25-31, n-alcan-1-ols C22-28 i ƒÂ13Clipids) permetra ajudar a clarificar el paper de les zones tropicals de lfhemisferi sud en el control del clima a escala milElenaria.