A Twentieth Century Major Soluble Ion Record of Dust and Anthropogenic Pollutants from Inilchek Glacier, Tien Shan

Using a high-resolution (~18 samples/year) major soluble ion record (Na+, K+, Mg2+, Ca2+, Cl-, NO3- and SO42-) covering the period 1908-1995 AD from the Inilchek Glacier, Tien Shan, Kyrgyzstan we provide a detailed climate and environmental proxy record for the region. Chemical concentrations, empirical orthogonal function analyses and non-crustal excess calculations are used to identify natural and potential anthropogenic depositional trends. Dominant dust proxy species (i.e. Ca2+) reveal highest concentrations during the 1950s-1970s, with declining decadal trends through the end of the record. These trends likely reflect decreases in central Asian dust storm activity post-1950, which has been associated with coupled atmospheric circulation variability and anthropogenic activities. Comparison between Ca2+ and ERA-interim (1979-1995) climate reanalysis data indicates a strong relationship to spring (March, April and May) geopotential height patterns in northwest China and southern Siberia associated with the Siberian High. Non-crustal contribution (excess) estimates of NO3-, K+, SO42-, and Cl- concentrations suggest discernable anthropogenic inputs began between the 1950s-1970s, increased into the mid/late1980s and declined in the 1990s. Excess trends coincide with Former Soviet Union (FSU) consumption, production and emission of fossil fuels and fertilizers, reflecting the rapid growth of agriculture and industry, as well as economic declines in the mid-late 1980s/early 1990s. Excess-Cl- trends reflect timings that coincide with the construction of the Pavlodar Chemical Plant and the military production of Cl2 in Kazakhstan. NOAA HYSPLIT back-trajectory frequency analysis suggests eastern Uzbekistan (e.g. Fergana Valley), Kyrgyzstan and southern Kazakhstan as the primary pollutant sources to the study region.