从末次冰盛期冰川规模探讨当时的气候环境——以乌鲁木齐河源区末次冰盛期冰川为例

Investigation of Climatic Conditions by the Glacier Extension in the Last Glacier Maximum

根据乌鲁木齐河源区末次冰盛期形成的保存完好的古冰川遗迹和现代气候条件下冰川物质平衡与气候的关系，用冰川动力学方法估算出冰川达到末次冰盛期规模时的气候条件。依据末次冰盛期冰川面积，结合冰川平衡线高度和冰川体积综合分析，乌鲁木齐河源区末次冰盛期的夏季气温应比现代低４．８℃左右，降水约只有现代的３０％。但目前其它古气候方法的研究结果表明，末次冰盛期的夏季气温比现代低５．６℃左右，两者相差０．８℃，其原因可能主要是冰川动力学方法未考虑构造抬升对气温的影响，据此推测，乌鲁木齐河源区末次冰盛期至今的构造上升量约为１３０ｍ。

This paper presents the estimated climatic scenarios in the Last Glacial Maximum(LGM) using glacier dynamics method, based on glacial vestiges well preserved in the head water of the Urumqi River and the relationship between glacier mass balance and climate in the contemporary climatic scenarios. Based on calculations of glacier areas in the LGM, it is estimated that preciptation in the LGM was less than contemporary one if summer air temperature was1.6℃ lower than that at present. If 4℃ lower, precipitation in the LGM was less than half of current . By combining of the ELA and glacier volume in the LGM, it is determined that sumer air temperature in the head water of the Urumqi River in the LGM was 4.8℃ lower than the contemporary temperature and the precipitation in that time approximately accounted for 30% of the contemporary one. However, other paleoclimatic studiesdemonstrate that the temperature in the LGM was 5.6℃ lower than that at present. The difference, 0.8℃, is attributed to that ground surface uplift was not figured by the glacier dynamics method. As a result,it is estimated that ground surface uplift reached 130 m since the LGM in the head water of the Urumqi River. It is consistent with the result of 120～140 m obtained from the depth of the valley downcut in the Urumqi River.