Thermomechanically coupled modelling for land-terminating glaciers: a comparison of two-dimensional, first-order and three-dimensional, full-Stokes approaches
Thermomechanically coupled modelling for land-terminating glaciers: a comparison of two-dimensional, first-order and three-dimensional, full-Stokes approaches
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DOI：
10.3189/2015jog14j220
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发表时间：
2015
影响因子：
3.4
通讯作者：
Tong Zhang;L. Ju;W. Leng;S. Price;M. Gunzburger
中科院分区：
文献类型：
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作者：
Tong Zhang;L. Ju;W. Leng;S. Price;M. Gunzburger
对于许多地区，冰川不可达性导致稀疏的几何数据集用作模型初始条件（例如，仅沿沿着中心流线）。在这些情况下，二维（2-D）流线模型经常被用来研究冰川动力学。在这里，我们系统地调查的适用性的2-D，一阶斯托克斯近似流线模型（FLM），修改形状因子，模拟陆地终止冰川的3-D，“全”斯托克斯冰流模型（FSM）进行比较。基于稳态和瞬态，热力学解耦和耦合的计算实验，我们探讨了FLM和FSM冰的几何形状，温度和前向模型积分时间的敏感性。我们发现，相比FSM，FLM一般产生较慢的水平速度，由于FLM固有的简化和形状因子的低估。对于多温冰川，温带冰区，或当基底滑动是重要的，我们发现使用FLM与FSM的模拟结果之间的显着差异。随着时间的推移，最初FLM和FSM之间的小差异变得更大，特别是在冷/温带冰过渡表面附近。长时间的积分进一步增加了两个模型之间的小的初始差异。我们的结论是，FLM应谨慎应用时，在气候变暖或长时间的冰川变化建模。
For many regions, glacier inaccessibility results in sparse geometric datasets for use as model initial conditions (e.g. along the central flowline only). In these cases, two-dimensional (2-D) flowline models are often used to study glacier dynamics. Here we systematically investigate the applicability of a 2-D, first-order Stokes approximation flowline model (FLM), modified by shape factors, for the simulation of land-terminating glaciers by comparing it with a 3-D, ‘full’-Stokes ice-flow model (FSM). Based on steady-state and transient, thermomechanically uncoupled and coupled computational experiments, we explore the sensitivities of the FLM and FSM to ice geometry, temperature and forward model integration time. We find that, compared to the FSM, the FLM generally produces slower horizontal velocities, due to simplifications inherent to the FLM and to the underestimation of the shape factor. For polythermal glaciers, those with temperate ice zones, or when basal sliding is important, we find significant differences between simulation results when using the FLM versus the FSM. Over time, initially small differences between the FLM and FSM become much larger, particularly near cold/temperate ice transition surfaces. Long time integrations further increase small initial differences between the two models. We conclude that the FLM should be applied with caution when modelling glacier changes under a warming climate or over long periods of time.