Tropical Climate Dynamics – Insights from the Cariaco Basin and Mexican lakes: GFZ

Tropical Climate Dynamics – Insights from the Cariaco Basin and Mexican lakes

All lacustrine localities in Mexico are of volcanic origin (maar type). Sediment cores that cover the past ca. 5000 years are examined in part. The study of the Valle-de-Santiago lakes has an additional important aspect as they are threatened with de... — All lacustrine localities in Mexico are of volcanic origin (maar type). Sediment cores that cover the past ca. 5000 years are examined in part. The study of the Valle-de-Santiago lakes has an additional important aspect as they are threatened with desiccation. *(GFZ)*

Geographic and climatic setting of the study sites within the precipitation regime for January and July; GPCP Monthly Mean Precipitation Rate [mm/day] Average 1983-2003;

The reconstruction of tropical climate and ITCZ dynamics on a high-frequency scale (El-Niño-Southern Oscillation - ENSO, North Atlantic Oscillation - NAO) is pivotal to understand the role of the Tropics in global climate change. Our sediment-core locations sit along a transect from the Cariaco Basin (off N Venezuela) across East and Central Mexico to the Pacific coast, an area ideal for the study of seasonal change of the ITCZ position that predominantly determines the hydrological cycle and rainfall distribution in Mesoamerica.

From those laminated sequences, we obtain data in ultra-high time resolution applying µXRF-element scanning 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. Stable isotope analyses of carbonates (laminae and ostracods) and geochemistry of organic matter supplement those series. 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 10000 yr (the Mexican lakes). We will discuss our paleoclimate data in light of the societal development in the region of the Trans-Mexican Volcanic Belt and Yucatan.

With this approach we seek to answer the following questions:

What was the history of mean-state, frequency, and amplitude of El Nino Southern Oscillation in the region during climatic extremes (e.g. transitions from the last glacial to the Holocene thermal maximum; and from the "Medieval Warm Period" to the "Little Ice Age")?

How did Atlantic/Pacific ITCZ migrate in position over the past 1000 years? What drove the ITCZ (low vs. high latitude forcing) during the past Glacial/Interglacial cycle?

Can millennial- to sub-decadal-scale climate signals be correlated with similar records in Central and South America?

What has been the impact of climate on the societal development and vice versa in north Central Mexico and Yucatan during the past 1000 years?

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