This paper presents a new high-resolution oxygen isotope (δ¹⁸O) time series from the Qiangtang (QT) No. 1 ice core on the central Tibetan Plateau, spanning 335 years (1677–2011 CE). Using variational mode decomposition (VMD) to separate the El Niño Southern Oscillation (ENSO) mode, the study identifies strong signals of the Pacific Decadal Oscillation (PDO) with periods of 25–35 years and 50–70 years. The 50–70-year periodicity is dominant before 1900 CE, while the 25–35-year periodicity becomes more prominent afterward. The increasing frequency of El Niño events is linked to the recent increase in ice core δ¹⁸O.

Shijie Li, Lide Tian, Zhongyin Cai, Di Wang, Lili Shao, Xiaoyi Yang, Shangjie Wang, Feng Liu, Pengbin Liang