NOAA/WDS Paleoclimatology - Gempa Bumi Cave, Sulawesi Indonesia d13C, Mg/Ca Data over the last 40ka

Recent research has shown the potential of speleothem d13C to record a range of environmental processes. Here, we report on 230Th-dated stalagmite d13C records for southwest Sulawesi, Indonesia, over the last 40,000 years to investigate the relationship between tropical vegetation productivity and atmospheric methane concentrations. We demonstrate that the Sulawesi stalagmite d13C record is driven by changes in vegetation productivity and soil respiration and explore the link between soil respiration and tropical methane emissions using HadCM3 and the Sheffield Dynamic Global Vegetation Model. The model indicates that changes in soil respiration are primarily driven by changes in temperature and CO2, in line with our interpretation of stalagmite d13C. In turn, modeled methane emissions are driven by soil respiration, providing a mechanism that links methane to stalagmite d13C. This relationship is particularly strong during the last glacial, indicating a key role for the tropics in controlling atmospheric methane when emissions from high-latitude boreal wetlands were suppressed. With further investigation, the link between d13C in stalagmites and tropical methane could provide a low-latitude proxy complementary to polar ice core records to improve our understanding of the glacial-interglacial methane budget.