Effects of glacial conditions on the circulation and water vapor sources of Indian monsoon precipitation

Climate records suggest a weaker Indian monsoon circulation and drier conditions in the continent during the Last Glacial Maximum (LGM, ~19-23 ka BP). This is mainly due to circulation changes caused by high-latitude ice sheets, tropical and high-latitude SST changes, and lower atmospheric CO2 concentrations compared to pre-industrial (PI). Such changes in boundary conditions and circulation are likely to cause changes in the water vapor sources of monsoon precipitation, with implications for precipitation reconstructions using water isotope proxies. We use the water isotope/water tagging-enabled Community Earth System Model (iCESM) to study the effects of glacial conditions on the sources of water vapor and isotope ratios of precipitation for the Indian monsoon precipitation. We conduct time slice experiments for the PI and the LGM periods following the PMIP4 guidelines. iCESM was successful in identifying the water vapor sources of present-day Indian summer monsoon precipitation, namely the Indian Ocean sources and precipitation recycling. The detailed results of this study will be presented at the meeting.