冰川物质平衡线的估算方法

The Methods for Estimating the Equilibrium Line Altitudes of a Glacier

冰川物质平衡线高度(ELA)与气候变化,特别是与气温和降水的变化关系密切,是重建古气候和反映冰川积累和消融变化的重要代用指标.直接观测方法可以获得较为精准的ELA,但不能大范围展开.因此,ELA的间接估算方法,如赫斯法(Hess)、积累区面积比率法(AAR)、面积–高程平衡率法(AABR)、末端至冰斗后壁比率法(THAR)、终碛到最高峰高差比率法(TSAM)、侧碛最大高度法(MELM)、冰斗底部高程法(CF)、冰川作用阈值法(GT)等,得到了广泛的发展与应用.然而,由于受到雪崩或风吹雪补给、表碛覆盖、冰川类型和形态等因素的影响,单一使用某种方法易受到算法本身的限制,误差较大,需综合考虑各种算法的适用性和选取参数的差异,以提高计算的精度,同时也要考虑到后期构造抬升等的影响.

There is a very close connection between the equilibrium line altitude(ELA) and the local climate,particularly solid precipitation and air temperatures.Fluctuations in the ELA therefore provide a pronounced indicator of glacier response to climate change,and help to reconstruct the former climates and to predicate the future glacier behavior.For the glaciers at present,direct observation of glacier mass balance over several years is an ideal method to obtain accurate ELA.However,for a greater range,other estimating methods have to employed,e.g.,accumulation area ratio(AAR),area altitude balance ratio(AABR),toe-to-headwall altitude ratio(THAR),terminal to summit altitude method(TSAM),maximum elevation of lateral moraines(MELM),cirque-floor altitudes(CF) and glaciation threshold(GT).Due to the combined influence of avalanches and snow drift,debris cover and topographic effects(glacier morphologies and styles),the ELAs of a glacier estimated with various methods may have discrepancies of several hundred meters.It is necessary to employ multiple methods,together with an appraisal of their reliability.Furthermore,the tectonic uplift should be considered as well.