Continuous Holocene Streamflow Rise and ENSO Linked Floods in the Upper Reaches of Yarlung Tsangpo

Understanding the long-term streamflow variability of the Yarlung Tsangpo (called the Brahmaputra River in downstream) is critical for water resources management due to its provision of freshwater for millions of people and its flood risk. However, previous streamflow reconstructions, based on dendrochronology and palaeo-flood sediments, are either discontinuous or cover only a few hundred years. Here, we provide a continuous palaeolimnological record of the streamflow of the Yarlung Tsangpo upstream. Our results reveal an unexpected streamflow rise after 6,000 years ago, indicating the Westerlies and glacier meltwater replaced Indian Summer Monsoon as the dominant driver of runoff. Furthermore, the relatively frequent palaeo-flood events during the early and late Holocene may be attributed to El Niño-Southern Oscillation (ENSO) variance. These findings suggest the future occurrence of unsustainable streamflow and an increased flooding risk, as a result of weakening Westerlies, reduced glaciers, and strengthened ENSO activity under climatic warming.