青藏高原各拉丹冬冰芯记录的季节气温变化

Seasonal Air Temperature Variations Retrieved from a Geladaindong Ice Core,Tibetan Plateau

2005年10-11月中美联合考察队在各拉丹冬峰北部果曲冰川平坦的粒雪盆(33o34'37.8"N,91o10'35.3"E,5720m a.s.l.)钻取了一支冰芯,通过对该冰芯进行多参数定年,恢复了青藏高原中部各拉丹冬地区近70年来降水中δ18O的变化历史。根据冰芯中季风期和非季风期δ18O值与临近气象台站气温的正相关性,重建了该地区70年来的春季和夏季的气温变化。结果表明,各拉丹冬冰芯中δ18O记录的春季和夏季升温趋势非常明显;根据回归分析,冰芯中非季风期的δ18O每增大(或减小)1‰相当于春季气温升高(或降低)1.3oC;季风期的δ18O每增大(或减小)1‰相当于夏季气温升高(或降低)0.4oC;各拉丹冬冰芯中δ18O记录恢复的春季和夏季气温与北半球春季和夏季的气温变化具有一致的趋势,但各拉丹冬地区的增温幅度比北半球要大,同时春季的增温幅度也高于夏季。

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 （33°34′37.8＂N, 91°10′35.3＂E, 5720 m a.s.1.） on Mt. Geladaindong （the source region of the Yangtze River） during October and November, 2005. Based on the seasonality of δ18Orecords and the significant positive relationships 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 δ18Ovalues 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.