NOAA/WDS Paleoclimatology - Mawmluh Cave, India 135-100ka Speleothem Isotope and Trace Element Data

To date Indian Summer Monsoon (ISM) dynamics have been assessed by changes in stalagmite d18O. However, stalagmite d18O is influenced by multiple environmental factors (e.g. atmospheric moisture transport, rainfall amount at the study site, ISM seasonality), precluding simple and clear reconstructions of rainfall amount or variability. This study aims to disentangle these environmental factors by combining d18O, d44Ca and elemental data from a stalagmite covering Termination II and the last interglacial from Mawmluh Cave, NE India, to produce a semi-quantitative reconstruction of past ISM rainfall. We interpret d18O as a mixed signal of rainfall source dynamics and rainfall amount, and coupled d44Ca and X/Ca ratios as indicators of local infiltration rate and prior calcite precipitation in the karst zone. The wettest conditions in our studied interval (135 and 100 kyrs BP (BP = before present, with the present being 1950 CE)) occurred during MIS-5e. Our multi-proxy dataset suggests a likely change in seasonal distribution of MIS-5e rainfall compared to the Holocene; the wet season was longer with higher-than-modern dry season rainfall. Using the last interglacial as an analogue for future anthropogenic warming, our data suggest a more erratic ISM behavior in a warmer world.