Major ions composition records from a shallow ice core on Mt. Tanggula in the central Qinghai-Tibetan Plateau

A 32.4 m shallow ice core was recovered from a site at 5743 m above sea level on the Mt. Tanggula in the central Qinghai-Tibetan Plateau in August 2005. A total of 630 samples were analyzed for major ions (Na+, NH4+, K+, Mg2+, Ca2+, Cl−, SO42− and NO3−) and stable oxygen isotope ratios (δ18O). The ion chemistry of the upper 14.5 m, covering the last 55 years, is characterized by mineral dust (HCO3−, Ca2+, SO42−, Na+, Cl− and K+), anthropogenic species (SO42−, NH4+ and NO3−) and soil and biogenic emissions (NO3− and NH4+). Ca2+ is the dominant cation in the core with a medium value of 33.5 μeq L−1, accounting for 64.5% of the total cations, and HCO3− is the predominant anion, accounting for 80.2% of the total anions. Compared with ice core records from Altai and Himalayas, at the northern and southern margin of the Qinghai-Tibetan Plateau, respectively, major ion concentrations (except SO42−, NH4+ and NO3−) in Tanggula ice core are much higher due to pronounced regional crustal aerosol inputs. Increasing SO42− concentrations in the most recent 50 years are attributed to anthropogenic contributions; but mineral dust is still the major sources for SO42− in the central Qinghai-Tibetan Plateau. The notable relationship between increasing Northern Hemisphere temperature and NO3− and NH4+ concentrations suggests that recent temperature increase in Qinghai-Tibetan Plateau may be enhancing biological activity and associated NO3− and NH4+ emissions from the regional terrestrial ecosystems.