Ice core δ18O evidence for climatic transition since 1990s on East Rongbuk Glacier

Ice core stable water isotope (δ 18 O) records serve as reliable proxies for temperature on long timescales in both polar and tropical high-elevation regions. However, the climatic implications of ice core δ 18 O over the monsoon-influenced southern Tibetan Plateau remain poorly understood. Here, we establish the East Rongbuk (ERB) ice core chronology spanning 1952–2021 for the central Himalaya through cross-dating of δ 18 O records from five ERB ice cores. The results show that the ERB ice core δ 18 O decreased significantly during the 1980s, increased markedly in the 1990s, and exhibited a hiatus in the early 21st century. Since the 1990s, the ERB ice core δ 18 O record has exhibited strong coherence with records from the northwestern Tibetan Plateau and other Himalayan ice cores. This coherence likely reflects the coupled weakening of the monsoon and westerly circulations, such that ERB δ 18 O primarily captures a coherent large-scale climatic signal, including pronounced 1990s warming and the early 21st-century warming hiatus, which is also evident in tree-ring records that capture cold-season temperature variability. Therefore, ERB ice core δ 18 O during 1990–2021 can be interpreted as a reliable proxy for air temperature on the northern slope of the central Himalaya under a weakened monsoon circulation regime. These results highlight the coupled influence of the monsoon and westerly circulations on the high-elevation climate of the Himalaya.