NOAA/WDS Paleoclimatology - Frappier et al. 2002 Belize Stalagmite Carbon Isotope Data

The El Nino/Southern Oscillation (ENSO) system is a prominent component of interannual climate variability, and the Southern Oscillation Index (SOI) is a primary measure of the state of the ENSO system. Here, we present evidence that ENSO-related changes in the terrestrial carbon cycle can be recorded by stalagmites, thus providing a proxy for past El Nino events. Our analysis of a stalagmite from Belize reveals a strong correlation between the SOI and carbon isotope ratios (d13C values), even though the site experiences no discernible local weather effects that are correlated with the SOI. d13C values of this stalagmite must reflect changes in the overlying rainforest ecosystem's carbon budget that are sensitive to subtle modifications of local weather related to ENSO.