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首页> 外文期刊>Research in Geophysics >Inversion for basal friction coefficients with a two-dimensional flow line model using Tikhonov regularization
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Inversion for basal friction coefficients with a two-dimensional flow line model using Tikhonov regularization

机译：使用Tikhonov正则化的二维流线模型反演基础摩擦系数

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We present results of basal friction coefficient inversion. The inversion was performed by a 2D flow line model for one of the four fast flowing ice streams on the southern side of the Academy of Sciences Ice Cap in the Komsomolets Island, Severnaya Zemlya archipelago. The input data for the performance of both the forward and the inverse problems included synthetic aperture radar interferometry ice surface velocities, ice surface elevations and ice thicknesses obtained by airborne measurements (all were taken from Dowdeswell et al. , 2002). Numerical experiments with: i) different sea level shifts; and ii) randomly perturbed friction coefficient have been carried out in the forward problem. The impact of sea level changes on vertical distribution of horizontal velocity and on shear stress distribution near the ice front has been investigated in experiments with different sea level shifts. The experiments with randomly perturbed friction coefficient have revealed that the modeled surface velocity is weakly sensitive to the perturbations and, therefore, the inverse problem should be considered ill posed. To mitigate ill posedness of the inverse problem, Tikhonov’s regularization was applied. The regularization parameter was determined from the relation of the discrepancy between observed and modeled velocities to the regularization parameter. The inversion was performed for both linear and non-linear sliding laws. The inverted spatial distributions of the basal friction coefficient are similar for both sliding laws. The similarity between these inverted distributions suggests that the changes in the friction coefficient are accompanied by appropriate water content variations at the glacier base.
机译：我们提出基础摩擦系数反演的结果。反演是通过2D流线模型对位于Severnaya Zemlya群岛Komsomolets岛科学院冰盖南侧的四条快速流动冰流之一进行的。正向和反向问题性能的输入数据包括合成孔径雷达干涉测量法的冰面速度，冰面高度和通过机载测量获得的冰厚（均取自Dowdeswell等，2002）。数值实验：i）不同的海平面变化; ii）在正向问题中进行了随机扰动的摩擦系数。在不同海平面位移的实验中，已经研究了海平面变化对水平速度的垂直分布以及对冰面附近切应力分布的影响。随机扰动摩擦系数的实验表明，建模的表面速度对扰动不敏感，因此，应将反问题视为不适。为了减轻反问题的不适性，应用了Tikhonov的正则化方法。根据观察到的速度和建模速度之间的差异与正则化参数的关系确定正则化参数。对线性和非线性滑动定律都执行了反演。对于两个滑动定律，基础摩擦系数的倒置空间分布都相似。这些反演分布之间的相似性表明，摩擦系数的变化伴随着冰川底部适当的含水量变化。

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