TOWARD SEASONAL CLIMATE RECONSTRUCTIONS USING TROPICAL ISOTOPE DENDROCLIMATOLOGY

In temperate latitudes, extensive networks of tree ring width and density time series provide high-resolution proxy records of past climate state and variability. Relatively few such chronologies have been developed in tropical regions because many tropical tree species fail to develop reliable annual and climatically-interpretable ring patterns. Alternatively, intra-annual resolution oxygen isotope measurements can be used for chronological control and paleoclimate reconstruction. Annual isotope cycles have now been observed in Africa, Australasia, and the Americas, and anomalous seasonal values ascribed to variations in local climate. As illustration, we have developed a century-long monthly-resolved oxygen isotope chronology from the mountains of Costa Rica. We use it here to reconstruct local dry season wind and wet season precipitation since 1900. We identify a mid-century period of stronger dry season wind-driven moisture advection and reduced wet season rainfall which is consistent with the very limited instrumental records. We discuss these results in the context of possible wind-forced variability in the Costa Rica Dome and mid-summer Mesoamerican drought.