Optimal initial conditions for coupling ice sheet models to Earth system models
Optimal initial conditions for coupling ice sheet models to Earth system models
复制标题
将冰盖模型与地球系统模型耦合的最佳初始条件
DOI：
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复制
发表时间：
2014
期刊：
影响因子：
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通讯作者：
G. Stadler
中科院分区：
文献类型：
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作者：
M. Perego;S. Price;G. Stadler
我们解决复杂的耦合动态冰盖模式（ISM）和强迫从地球系统模式（ESM），这是因为未知的ISM初始条件。除非在ISM初始化过程中明确说明，否则冰盖与ESM的表面质量平衡作用力远未达到热力学平衡。当耦合到ESM强迫时，结果是冰的几何形状和其他状态变量中的冲击和非物理的和不期望的瞬变。热力学平衡的假设下，我们提出了一种方法来寻找ISM初始条件，其特征在于优化的基础滑动系数和基础地形领域的平衡最适合的表面速度和基础地形观测对非物理瞬变的最小化时，耦合到表面质量平衡强迫。拟牛顿法用于求解由此产生的大规模偏微分方程约束优化问题，其中相对于参数场的成本函数梯度使用伴随计算。在研究了我们的方法在合成测试问题上的性能后，我们将该方法应用于格陵兰冰盖模型的最佳初始条件。我们的研究结果表明，在基础地形的不确定性的存在下，冰的厚度也应该被视为一个优化变量。虽然这里的重点是ISM和ESM导出的表面质量平衡之间的耦合，但该方法很容易扩展到包括通过海底融化率从海洋模型强迫的最佳耦合。
We address complications in the coupling of a dynamic ice sheet model (ISM) and forcing from an Earth system model (ESM), which arise because of the unknown ISM initial conditions. Unless explicitly accounted for during ISM initialization, the ice sheet is far from thermomechanical equilibrium with the surface mass balance forcing from the ESM. Upon coupling to ESM forcing, the result is a shock and unphysical and undesirable transients in ice geometry and other state variables. Under the assumption of thermomechanical equilibrium, we present an approach for finding ISM initial conditions—characterized by optimization of the basal sliding coefficient and basal topography fields—that balance a best fit to surface velocity and basal topography observations against the minimization of unphysical transients when coupling to surface mass balance forcing. A quasi‐Newton method is used to solve the resulting large‐scale, partial differential equation‐constrained optimization problem, where the cost function gradients with respect to the parameter fields are computed using adjoints. After studying properties of our approach on a synthetic test problem, we apply the method toward obtaining optimal initial conditions for a model of the Greenland ice sheet. Our results show that, in the presence of uncertainties in the basal topography, ice thickness should also be treated as an optimization variable. While the focus here is on the coupling between an ISM and ESM‐derived surface mass balance, the method is easily extended to include optimal coupling to forcing from an ocean model through submarine melt rates.
影响因子：
5.2
作者：
Bamber, J. L.;Griggs, J. A.;Steinhage, D.
通讯作者：
Steinhage, D.