Tropical Climate Dynamics during the past Glacial/Interglacial Cycle in (sub)annual resolution (Cariaco Basin and Mexican Lakes)

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The position of the Intertropical Convergence Zone (ITCZ) and the intensity of the Hadley circulation force tropical climate variability in Central America. Our proposed study locations sit within the area of seasonal change of the ITCZ position that determines the hydrological cycle and rainfall distribution in Mesoamerica. They range from the Cariaco Basin (off N Venezuela) across Yucatan and Central Mexico to the Pazific coast. We propose to obtain paleoclimate data from those marine and terrestrial sites located across gradients of precipitation. The reconstruction of tropical climate and ITCZ dynamics on a high-frequency scale (El-Nino-Southern Oscillation - ENSO, North Atlantic Oscillation - NAO) is pivitol to understand the role of the Tropics in global climate change. Therefore, we propose to obtain data in ultra-high time resolution from laminated sequences. We will apply a combination of laminae-based studies, non-destructive, continuous bulk sediment measurements (e.g. uXRF) and varve microfacies analyses. These data, together with radionuclide dates (14-C, 137-Cs, 210-Pb) and tephrochronology, form the basis for a robust, varve-based chronology. Our data has the potential to provide a new history of mean-state, frequency, and amplitude of ENSO, and to disentangle the interplay between high versus low latitude forcing of ITCZ dynamics in the region during the past Glacial/Interglacial cycle (the Cariaco Basin) and focused on the past 1000 yr (the Mexican lakes). We will discuss our paleoclimate data in light of the societal development in west Central Mexico and Yucatan.