Oxygen isotopic and soluble ionic composition of a shallow firn core, Inilchek glacier, central Tien Shan
Abstract:Oxygen isotopic and soluble ionic measurements made on snow-pit (2 m depth) and firn-core (12.4 m depth) samples recovered from the accumulation zone (5100 m) of Inilchek glacier (43°:N, 79°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, and contains only one observed melt feature (10 m temperature = -12°C). Although some post-depositional attenuation of the sub-seasonal 18O record is possible, annual cycles are apparent throughout the isotope profile. We therefore use the preserved 18O record to establish a depth/age scale for the core. Mean 18O values for the entire core and for summer periods are consistent with 18O/tem- perature observations, and suggest the 18O record provides a means to reconstruct past changes in summer surface temperature at the site. Major-ion (Na+, K+, Mg2+, Ca 2+, NH4+, Cl-, NO3=, SO42-) data from the core demonstrate the dominant influence of dust deposition on the soluble chemistry at the site, and indicate significant interannual variabil- ity in atmospheric-dust loading during the1990s. Anthropogenic impacts on NH4 +concen- trations 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.
Document Type: Research Article
Publication date: December 1, 2001
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