Study of the climatic variations in the Indo-Pacific area: role of the low-latitudes in the millennial scale variability

The inter-tropical regions, characterized by high sea surface temperatures and heavy precipitations, are a major source of heat and moisture to the atmosphere and therefore plays an important role in regulating the earth climate. Hence, hydrological variations of the low latitudes would have significant consequences on climate. Marine foraminifera isotopic (δ¹⁸O et δ¹³C) and geochemical (Mg/Ca ratio) records have drawn the evolution of inter-tropical sea surface temperature and salinity during the past abrupt climatic changes of the last climatic cycle. The detailed study of the last 24000 years has shown that the low latitude sea surface temperature variations are synchronous with the high latitude southern hemispheric changes, revealing a narrow correlation with the southern hemisphere. Although sea surface salinity evolution is linked to the Greenland temperature record during millennial climatic changes (Heinrich Events, Bolling Allerod, Younger Dryas). These results demonstrate that changes in tropical evaporation is narrowly associated with ice sheet growth and decay of the northern high latitude. The synchronicity of these variations reveals the occurrence of a tight atmospheric link between these regions. Moreover, intermediate and deep water studies have also exhibited that tropical sea surface salinity increase would have strengthened the deglaciation by increasing deep water convection in the Antarctic circumpolar waters, resulting in a southern initiation of the thermohaline circulation. (author)