ABSTRACT

Past interglacials offer us insights into the response of climate and ecosystems extremes beyond those experienced within the Holocene. While not perfect analogs for projected climate change, interglacials such as Marine isotope stage 5e (MIS 5e) offer us the best empirical insights available for probably warmer and drier conditions. Consequently, a substantial international effort is being made to capture the MIS 5e from Greenland and there is broad interest in acquiring highly-resolved records from all latitudes. Beyond simply wanting to know interglacial conditions, the paleoclimatic community is particularly interested in the transitions into and out of interglacial conditions, i.e. Termination II and Inception I. This project provides centennial-scale multiproxy analyses for Termination II, and MIS 5e and d (135-106 ka) from three recently collected sediment cores from Mexico, Guatemala, and Panama. These records form the first detailed terrestrial archive of climate and vegetation change for MIS 5e from the Neotropics.
The analyses include XRF, core color, and fossil pollen, charcoal and diatom analyses. A chronology for each site is established through a combination of tephrachronology and U-series dating. Preliminary U-series dates from the Panamanian core confirms almost 5 m of deposition between ages of 130 and 115 ka. The other records appear to have similar or faster rates of deposition. Bayesian statistics are used to create transfer functions for temperature, precipitation, and number of dry days per year. These data are used to test hypotheses relating to the past migration of the inter-tropical convergence zone, varying strength of the meridional overturning circulation, the presence of quasi-cyclic climatic rhythms, and the variability of MIS 5e relative to the Holocene. This provides the first regional estimate of whether the past interglacial was a time of forest or scrubland expansion in Central America, a finding that is of critical importance to modeling past and future carbon storage.
This data provides important benchmarks against which paleoclimate models can be tested. Currently, no detailed terrestrial data are available for MIS 5e from Central America or Mexico. This data is of significance to those engaged in planning for a warmer world, whether for agriculture, forestry or conservation. The provision of highly resolved climate records from Central America allows hypotheses generated in other records to be tested.
This data is also of significance to ecologists studying modern forest dynamics and to evolutionary biologists investigating the origins of tropical diversity. Providing well-resolved chronologies for these cores encourages other workers using different proxies to work on them.
This research leads to a significant number of new collaborations in Mexico, the USA, Germany, Costa Rica, and the UK. During this project two undergraduates are trained each year, and REU and RET personnel are encouraged to publish their results. One Ph.D. student and one post-doc are supported. A female MS student in Costa Rica is engaged in the project without charge to NSF.

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