Irrawaddy River experienced more frequent hydrological drought events with global warming: Evidence from a 400-year tree ring oxygen isotope record

Abstract

Global temperature fluctuations have significantly impacted regional hydrological cycles. The Irrawaddy River (IR) is the largest river in Myanmar and has an important influence on socioeconomic conditions within its watershed and beyond. However, potential changes to the IR’s hydrological extremes under a future warming climate remain poorly understood. We reconstructed a 400-yr May–July streamflow time series for the IR using tree-ring cellulose oxygen isotopes (δ18O) and compared the variations of the hydrological extremes before and after the onset of global warming. The streamflow reconstruction shows that the IR experienced 65 extreme flood events and 67 extreme drought events during 1617–2017, with 58 extreme drought events occurred after 1850. Extreme drought events in this region have gradually increased and the frequency of extreme droughts has increased significantly since the 1850s. The occurrence of drought events in the last few decades has exceeded the natural variability. Especially, the persistent drought conditions during 2000–2017 are unprecedented compared with the record of the last 400 yr. This increase in drought events is significantly linked to the weakening of the ISM and increasing temperatures, hence the IR may experience more extreme drought events in the future under global warming.