An 81.2-m-long ice core was drilled in November 2019 at 5862m a.s.l. of Trambau Glacier, Rolwaling region, Nepal Himalaya.For the analysis, ice-core samples were prepared to measure major ion and tritium concentrations in the cold laboratory (-20 degC) at the Institute of Low-Temperature Science, Hokkaido University, Japan. We used a bandsaw to cut the core into 0.05 m sections. To minimize the risk of contamination (e.g., from drilling and transportation), we used a ceramic knife in a positive-pressure environment to shave off the outer surface of each sample. Decontaminated samples (n = 1592) were then packed in clean, sealed polyethylene bags and melted at ambient temperature, after which the resulting water was transferred to polypropylene bottles for storage. Concentrations of major water-soluble ions were quantified using Dionex ICS-1100 and ICS-2100 ion chromatography systems (Thermo Scientific). The measurement precision for each ionic species was 10%; we corrected measurement bias by multiple measurements of the same sample. Tritium concentrations were analyzed by liquid scintillation counting (LSC-LB3; Aloka, Japan) at the National Institute of Polar Research. First, we measured all layers at a coarse resolution (2.5 m intervals, n = 32 samples) by mixing each 1 mL from every 50 samples. To confirm the data at depths at which high tritium concentrations were measured, we made a second measurement for ice layers at depths between 29.77 and 35.11 m (0.25 m intervals, n = 20 samples) by mixing each 10 mL from every 5 samples. This data set contains the concentrations of major ions (Na, Cl, NH4, K, Mg, Ca, NO3, SO4) and tritium concentrations of the ice core.