Projections of glacier peak water and its timing in the Sanjiangyuan on the Tibet Plateau

The Sanjiangyuan, located on the Tibetan Plateau, is the headwater of the three large Asia Rivers- the Yangtze, Yellow and Lancang (upper Mekong) Rivers. Mountain glacier melt runoff, an important buffer against drought, is enhancing with climate warming. Projection of glacier (especially small glaciers) runoff change is imperative for adapting to climate change and mitigating relevant risks. We aim to provide an up-to-date knowledge of the glacier area and runoff change for 2016–2099 in the Sanjiangyuan. Projections based on CMIP6 archive show that 1) glacier area in the Sanjiangyuan for the four SSPs will shrink by 36 ± 12 % (SSP1–2.6), 42 ± 20 % (SSP2–4.5), 49 ± 19 % (SSP3–7.0) and 61 ± 15 % (SSP5–8.5) by the end of the 21st century. Small glacier dominated Lancang River basin is more sensitive to climate change than large glacier abundant Yangtze River basin and Yellow River basin. The Lancang River basin is projected to experience the greatest relative glacier area shrinkage, 10 % of glacier area and 55 % of glacier number will disappear for SSP5–8.5; 2) annual glacier runoff in the Yangtze River and Yellow River will reach peak water around 2080 under SSP3–7.0, while the Lancang River is already in or near peak water timing for all SSPs. Higher emission scenario tends to yield later peak water timing due to the changes in snow melt.