Sources of water vapor and their effects on water isotopes in precipitation in the Indian monsoon region: a model-based assessment

Identifying the sources of water vapor is important in understanding the role of monsoonal circulation in the delta O-18 values, to aid in monsoon reconstructions. Here, using an isotope-enabled Earth system model, we estimate the contributions of oceanic and terrestrial water vapor sources to two major precipitation seasons in India-the Southwest monsoon and the Northeast monsoon, and their effects on the delta O-18 in precipitation (delta O-18(p)).

We find that the two monsoon seasons have different dominant sources of water vapor because of the reversal in atmospheric circulation. While Indian Ocean regions, Arabian Sea, and recycling are the major sources of the Southwest monsoon precipitation, North Pacific Ocean and recycling are two crucial sources of Northeast monsoon precipitation. The delta O-18(p) of the Southwest monsoon precipitation is determined by contributions from the Indian Ocean sources and recycling.