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

Abstract

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 +, NH 4 +, K +, Mg 2+, Ca 2+, Cl −, SO 4 2 − and NO 3 −) and stable oxygen isotope ratios ( δ 18O). The ion chemistry of the upper 14.5 m, covering the last 55 years, is characterized by mineral dust (HCO 3 −, Ca 2+, SO 4 2 −, Na +, Cl − and K +), anthropogenic species (SO 4 2 −, NH 4 + and NO 3 −) and soil and biogenic emissions (NO 3 − and NH 4 +). Ca 2+ 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 HCO 3 − 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 SO 4 2 −, NH 4 + and NO 3 −) in Tanggula ice core are much higher due to pronounced regional crustal aerosol inputs. Increasing SO 4 2 − concentrations in the most recent 50 years are attributed to anthropogenic contributions; but mineral dust is still the major sources for SO 4 2 − in the central Qinghai-Tibetan Plateau. The notable relationship between increasing Northern Hemisphere temperature and NO 3 − and NH 4 + concentrations suggests that recent temperature increase in Qinghai-Tibetan Plateau may be enhancing biological activity and associated NO 3 − and NH 4 + emissions from the regional terrestrial ecosystems.