Parameterising the grounding line in flow-line ice sheet models
Parameterising the grounding line in flow-line ice sheet models
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DOI：
10.5194/tc-4-605-2010
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发表时间：
2010-12
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影响因子：
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通讯作者：
R. Gladstone;A. Payne;S. Cornford
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文献类型：
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作者：
R. Gladstone;A. Payne;S. Cornford
摘要。对海洋冰盖行为进行符合实际的预测要求模型能够稳健地模拟接地线迁移。固定网格冰盖模型已被证明会表现出不一致的情况，因此其接地线迁移是不可靠的，除非在全冰盖模拟中尚未能达到的非常高的分辨率下。在本研究中，我们提出了几种不同的接地线参数化方法。这些方法的区别在于从最后一个接地网格点到第一个漂浮网格点的冰厚度剖面的选择，以及该剖面如何影响重力驱动应力和基底阻力。我们证明，最明显的厚度参数化选择，即从最后一个接地网格点到第一个漂浮网格点进行线性插值，并不是最有效的。我们表明，使用接地线参数化可极大地提高性能，并且选择一个更好的接地线参数化方法而非较简单的方法，能够在准确性和自洽行为方面带来进一步的改进，其效果相当于将网格分辨率提高两倍（即网格点数翻倍）。这里提出的接地线参数化方法并不能完全解决接地线问题，然而它降低了所需的分辨率。这些参数化是在一维“陆架流”流线模型的背景下提出的，但可扩展以应对多于一维的情况以及其他模型公式。
Abstract. Realistic predictions of the behaviour of marine ice sheets require that models are able to robustly simulate grounding line migration. Fixed-grid ice sheet models have been shown to exhibit inconsistent and hence unreliable grounding line migration, except at very high resolution not yet achievable in whole ice sheet simulations. In this study we present several different approaches to parameterising the grounding line. These are distinguished by choices regarding the ice thickness profile from the last grounded to the first floating grid point, and how this profile impacts the gravitational driving stress and basal drag. We demonstrate that the most obvious choice of thickness parameterisation, linear interpolation from the last grounded to the first floating grid point, is not the most effective. We show that use of a grounding line parameterisation greatly improves performance, and that choice of a better grounding line parameterisation over a simpler one can bring further improvements, in terms of both accuracy and self consistent behaviour, comparable to increasing the grid resolution by factor two (i.e. doubling the number of grid points). The approach presented here to parameterising the grounding line does not completely solve the grounding line problem, however it reduces the resolution required. The parameterisations are presented in the context of a one dimensional "shelfy-stream" flow-line model, but could be extended to cope with more than one dimension and other model formulations.