Isotope Dendroclimatology in Tropical Asia

Harvard University, Cambridge MA

Investigators

Abstract

This award supports research to examine the interplay of tropical oceans and global-scale atmospheric circulation processes at seasonal to inter-annual time scales using isotope dendroclimatolgy, a novel and evolving investigative tool for extracting stable isotope measurements from tree cellulose. Specifically, the researcher and his colleagues will develop annually resolved proxy estimates of rainfall variability from tropical Asia for the past several centuries using isotope dendroclimatology. The data will be used to examine relationships between regional rainfall patterns (including drought cycles) and broader patterns of climate variability such as the El Nino Southern Oscillation (ENSO), the Asian monsoon, and Pacific decadal variability). The investigator and his colleagues have demonstrated the potential of this new approach using trees from Costa Rica, Indonesia, and Thailand and now will expand this research to samples collected by several different research teams working in tropical forests throughout Asia. The researcher and his colleagues will focus their efforts on the monsoons of Southeast Asia and ENSO to better understand the natural patterns of climate variability in the tropics at seasonal, inter-annual, and decadal scales thereby improving the scientific community's abilities to predict the effects of climate variability on human society and natural ecosystems. The field of paleoclimatology owes many of its recent strides in knowledge to data derived from tree rings. However, the field of tree ring research has been primarily limited to collecting data from the mid to high latitudes because in these regions, trees develop growth banding due to differences in temperature and precipitation as a result of seasonality. In general for the tropical regions, seasonality is broadly described as relatively wet and dry. Such environmental factors have conspired with botanical evolution over time to create a situation in which the trees do not readily give up the climate information they may possess using the traditional visual methods of growth analyses because not all tropical trees create obvious growth bands. This has created something of a problem for paleoclimatolgists because the Tropics cover a significant area of the Earth yet the climate data they possess has barely been tapped because trees have not been available as a data archive. This research holds the promise of opening up that archive to quantitative analysis.