Oxygen isotopic and soluble ionic composition of a shallow firn core, Inilchek glacier, central Tien Shan

Oxygen isotopic and soluble ionic measurements made on snow-pit (2 in depth) and firn-core (12.4 m depth samples recovered from the accumulation zone 5100 m) of Inilchek glacier 43degrees N, 79degrees E) provide information on recent (1992-98) climatic and environmental conditions in the central Tien Shan region of central Asia. The combined 14.4 m snow-pit/firn-core profile lies within the firn zone, arid contains only one observed melt feature (10 m temperature = - 12 degreesC), Although some post-depositional attenuation of the sub-seasonal delta(18)O record is possible, annual cycles are apparent throughout the isotope profile. We therefore use the preserved delta(18)O record to establish a depth/age scale for the core. Mean delta(18)O values for the entire core and for summer periods are consistent with delta(18)O/temperature observations, and suggest the delta(18)O record provides a means to reconstruct past changes in summer surface temperature at the site. Major-ion (Na+, K+, Mg2+, Ca2+, NH4+, Cl-, NO3-, SO42-) data from the core demonstrate the dominant influence of dust deposition on the soluble chemistry at the site, arid indicate significant interannual variability in atmospheric-dust loading during the 1900s. Anthropogenic impacts oil NH4+ concentrations are observed at the site, and suggest a summer increase in atmospheric NH4+ that may be related to regional agricultural (nitrogen-rich fertilizer use activities.