Ice Core Records of Recent Climatic Variability: Grigoriev

Ice cores, 16.5 and 20-meters in length, were recovered under the auspices of a cooperative USSR US glaciological research program on the Grigoriev and It-Tish ice caps in the Tien Shan, Central Asia. These have been analyzed for microparticle concentrations and size distributions, stable isotopic ratios (o18Q and 80), selected chemical species, and Beta radioactivity. The 1)18Q records reveal an enrichment of -1%0 during the last 50 years, suggesting warmer temperatures. Concurrently, surface air temperatures at the meteorological station Tien Shan (elevation 3614 m) have increased -0.5°C. Temperatures at 20-m depth in the Grigoriev ice cap have increased 2.2'C from -4.2°C in 1962, to -2'C in 1990. This regional warming is consistent with current global climate model projections for Central Asia under doubled atmospheric C02 concentration simulations. Finally, initial measurements of dust concentrations, o 18Q, and oD from the nearby It-Tish ice cap margin strongly suggest the presence of glacial/interglacial stage ice near the bottom. Collectively, these data indicate that these high elevation, low latitude ice caps in Central Asia contain very long paleoenvironmental histories, which soon· might be lost if the current warming trend continues in this region.