Abstract:

A 70-year history of precipitation δ¹⁸O record has been retrieved using an ice core drilled from a plat portion of the firn area in the Guoqu Glacier (33o34′37.8″ N, 91o10′35.3″ E, 5720 m a.s.l.) on Mt. Geladaindong (the source region of Yangtze River) during October and November, 2005. Based on the seasonality of δ¹⁸O records and the significant positive rela-tionships between monsoon/non-monsoon δ¹⁸O values and summer/spring air temperature from the nearby meteorological stations, the history of summer and spring air temperature have been reconstructed for the last 70 years. The results show that both summer and spring air temperature variations present similar trends during the last 70 years. Regression analysis indicates that the slope of the temperature-δ¹⁸O relationship is 1.3℃/‰ for non-monsoon δ¹⁸O values and spring air temperature, and 0.4℃/‰ for monsoon δ¹⁸O values and summer air temperature. Variation of air temperature recorded in the ice core is consistent with that in the Northern Hemisphere (NH), however, the warming trend in the Geladaindong region is more intense than that in the NH, reflecting a higher sensitivity to global warming in the high elevation regions. In addition, warming trend is greater in spring than in summer.

Key words: ice core δ¹⁸O, summer, spring, air temperature variations, Mt. Geladaindong, Tibetan Plateau