基于分形的冰塔林形态模拟初探

Study of the Modeling of Seracs Landform Based on Fractal Theory

冰塔林在低纬度高海拔地区的大型冰川上发育广泛,如何评估其对冰川总体积的贡献意义显著.对冰塔林的形态特征进行了初步探讨,结果表明:东绒布冰川冰塔林呈现出分形特点,其盒维数在1.3～1.9之间,无标度区间约为40～160m.通过构建冰塔林消融模型,认为冰塔林区域的整体消融率(约50%)不依赖于其地形参数的变化;估计珠峰东绒布冰川冰塔林体积对冰川总体积的贡献率约为3.7%,可以忽略.

Seracs developing on some large glaciers can be a problem of how to calculate a convincing total ice volume.However,estimation of seracs＇ contribution requires knowledge of seracs＇ landform.It is found that seracs on the East Rongbuk Glacier exhibit fractal characteristics with the box dimension varying from 1.3 to 1.9 and the dimensionless interzone about 40～160 m.The upstream of the seracs zone has a larger fractal dimension than that of downstream zone,indicating that ice seracs will lose its complexity while being developed.A random mid-point displacement method is applied to model ice seracs＇ form.Through constructing a seracs＇ ablation model,the ablation ratio of a serac body can be calculated,and it is demonstrated that the overall ablation ratio in the seracs zone approaches to 50% and is independent on landform parameters.As a result,the ice volume of seracs can be estimated within few landform parameters（e.g.the length of ice seracs＇ zone and the height of ice seracs）.The contribution of ice seracs to the total glacier-ice volume of the East Rongbuk Glacier is ～3.7%,which can be neglected.