Wisconsin/W�rm glacial stage ice in the subtropical dunde ice cap, China

Abstract

The insoluble microparticle concentrations and size distributions and oxygen isotope abundances (δ18 0) in two 1-meter ice cores from the margin of the Dunde ice cap (38° 06 'N; 96° 24 'E; 5325 masl) drilled in 1986 and three ice cores drilled to bedrock at the summit of the ice cap in 1987 suggest the presence of Wisconsin/Wurm Glacial Stage (LWGS) ice in the subtropics. A Sino-American research group recovered three ice cores 136, 138 and 139 m in length from the summit of the Dunde ice cap in the Qilian Shan which are providing long, high temporal resolution climatic and environmental records for the NE section of the Tibetan Highlands. Particulate concentrations, conductivity and δ18 0 are the ice core constituents best established as indicators of the glacial/interglacial transition. The analyses of two shallow cores from the margin reveal a 14-fold increase in particulate concentration which is correlative with a 1% to 5% decrease (more negative) in δ18 0. The lower 10 to 13 m of three ice cores drilled to bedrock at the summit contain a ten-fold increase in dust (both soluble and insoluble) and a 1.2% decrease in oxygen isotopes. Additionally, the morphological properties of the particles in the LWGS ice are identical to those of the thick, extensive loess deposits of central china which accumulated during the cold, dry glacial stages of the Pleistocene. When the climatic and environmental records are fully extracted from the three deep cores they will provide a very detailed record of variations in particulates (soluble and insoluble), stable isotopes, net balance, pollen and perhaps atmospheric gases of CO2 and methane through the Holocene into the last glacial in the subtropics on the climatically important Tibetan Plateau.