A 154 a high-resolution ammonium record from the Rongbuk Glacier, north slope of Mt. Qomolangma (Everest), Tibet–Himal region

An 80.4 m ice core was recovered from a site at 6500 m above sea level on the East Rongbuk Glacier, Mt. Qomolangma (Everest) in August 1998. A total of 1816 samples were analyzed for major ions (Ca2+, Mg2+, Na+, K+, NH4+, SO42−, NO3−, and Cl−) and stable oxygen isotope ratios (δ18O). The core was dated by the seasonal variations along the stable isotopic and major ionic profiles, and the dating was verified by the double β activity peaks corresponding to the annual layers 1963 and 1954, the highest sodium peak corresponding to a major monsoon failure occurred in 1876–1877, and several identified sulfate volcanic signals. The NH4+ level remained fairly constant from 1840s to 1940s, followed by a substantial increase until the end of 1980s, then a slight decrease during the recent decade, which may provide information on change in the regional agriculture activities.