Causes and effects of climate variations and rapid hydrological shifts in the northern Neotropics during the last glacial/interglacial cycle

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Sediment records from the two ICDP sites Lake Chalco (central Mexico) and Lake Petén Itzá (northern Guatemala) provide the unique opportunity to study effects and causes of continental climate change in the northern Neotropics. Despite their geographical vicinity, both records indicate significant interregional differences during the last glacial/interglacial cycle, in particular during ~85 to 50 ka BP, the Last Glacial Maximum (LGM) and Heinrich Stadial 1 (HS1). This underscores the key position of both sites in the climate system and therefore, we propose to combine multi-proxy reconstructions with paleoclimate modeling to disentangle the spatiotemporal climatic evolution of the northern Neotropics, a region of utmost importance for global climate dynamics. We will combine bulk-geochemical, biomarker and lipid paleothermometer analyses with paleobioindicators and paleoclimatic simulations over the last glacial/interglacial cycle in order to assess (1) the effects of abrupt climate variation by quantifying the magnitude and rate of ecological changes in aquatic and terrestrial ecosystems (e.g. during HS 6-1) and (2) how shifts (disruptions and recoveries) of the Atlantic Meridional Overturning Circulation (AMOC), or Pacific Ocean Circulation (POC) especially during the deglaciation, cold events and warm periods, affected regional climates and ecosystem structures in the northern Neotropics. We are mainly interested in determining the causes and mechanisms behind climate variations and rapid hydrological shifts in the northern Neotropics. For this, the proxy-based reconstruction of past climate variability from the Lake Petén Itzá and the Lake Chalco records will be compared with those of strategically selected continental and marine records in order to put our results in a transregional context. Potential climate forcing mechanisms will finally be tested by high-resolution paleoclimate simulations using the Community Earth System Model (CESM 1) for periods that show contrasting climatic conditions among records. Overall, this project will contribute to a significantly enhanced understanding of the role and timing of the Atlantic and the Pacific Ocean circulation in modulating northern neotropical climate over the last 135 ka as well as in determining how fast past ecosystems at both ICDP sites responded to and recovered from these imposed hydrological changes. This will be essential to better understand how the sensible ecosystems of the neotropics will react and adapt to the expected dryer and warmer climate in the future.