The global climate during the Last Glacial was marked by abrupt climate change (EPICA Community Members, 2006). Cyclic to quasicyclic phenomena that characterized the North Atlantic seem to have spread over the globe through disruptions of the oceanic currents (Peterson et al. 2000). Greenland warm stadials-cold interstadials and Heinrich Events were the main modes of variation. These changes are of especial interest as they may parallel modern climate change in terms of its rapidity and relative magnitude. High-resolution continental records spanning the Last Glacial are needed to assess the effects of these global processes on tropical ecosystems. In this study, we present the first robustly-dated multiproxy paleoecological record from continental Central America (Hodell et al. 2008). The sediments of Lake Petén-Itzá, Guatemala, provide insights into the history of the vegetation and climate of the Central American lowlands during the last 85,000 years.
Results/Conclusions
Pollen data suggests that the forest composition underwent drastic changes associated with the North Atlantic Cycles. During Greenland warm interstadials the vegetation consisted of a cold moist assemblage dominated by Quercus, Ambrosia, Myrica, Myrsine, and Alnus. Conversely, Heinrich Events caused an almost complete replacement of this association by xerophitic shrublands dominated by Acacia, Celtis, Dodonaea and Poaceae. During Greenland cold interstadials that were not associated with Heinrich Events, a mixture between these two forest types was evident. Changes in moisture availability that were inferred from magnetic susceptibility (Hodell et a. 2008) were more finally resolved by multivariate ordination of the pollen data. Fire-associated Pinus forests were prevalent during periods when peaks of seasonal insolation difference occurred, overriding the signal from the North Atlantic. The vegetation of the tropical Central American lowlands is responsive to global climatic phenomena. The composition and structure of the vegetation communities shows sensitivity to high-latitude climatic processes that take place at centennial to millennial scales. Understanding the temporal and spatial nature of these relationships could shed light on the processes and patterns of modern climate change.
