Variability of atmospheric dust loading over the central Tibetan Plateau based on ice core glaciochemistry

摘要

A Mt. Geladaindong (GL) ice core was recovered from the central Tibetan Plateau (TP) spanning the period 1940-2005 AD. High-resolution major ion (Na~+, K~+, Ca~(2+), Mg~(2+), Cl~-, SO_4~(2-), NO_3~-) time-series are used to investigate variations in atmospheric dust loading through time. The crustal source ions vary seasonally with peaks in dust concentrations occurring during the winter and spring which are consistent with atmospheric dust observations at local meteorological stations. However, both similarities and dissimilarities are displayed between the decadal variation of atmospheric dust in the GL core and dust observation records from meteorological stations, which can be attributed to local environmental effects at the stations. This paper compares the 1980s and 1970s as case periods for low and high atmospheric dust loading, respectively, two periods reflecting shifts in spring atmospheric circulation (a weakening of zonal and meridional winds) from the 1970s (a period of enhanced dust aerosol transportation to central TP) to the 1980s (a period of diminished dust aerosol transportation to central TP), especially a significant decrease of meridional wind speeds in the 1980s. GL ice core dust proxies (Ca~(2+) and K~+) are correlated with Total Ozone Mapping Spectrometer (TOMS) Aerosol Index (AI) data in spring over the TP and in the northwestern China (especially for K~+). Thus variability of crustal ions in central TP ice core provides a proxy for reconstructing a history of atmospheric dust loading not only on the TP, but also in northwestern China.