Fast Spin-Up of Geochemical Tracers in Ocean Circulation and Climate Models
Fast Spin-Up of Geochemical Tracers in Ocean Circulation and Climate Models
复制标题
海洋环流和气候模型中地球化学示踪剂的快速旋转
DOI：
10.1029/2022ms003447
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发表时间：
2023
影响因子：
6.8
通讯作者：
Khatiwala S
中科院分区：
文献类型：
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作者：
Khatiwala S
海洋地球化学示踪剂，如放射性碳、钚和钍同位素以及惰性气体，被广泛用于限制海洋中的一系列物理和地球化学过程。然而，它们在全球海洋环流和气候模式中的常规模拟受到将它们整合到稳定状态的计算费用的阻碍。在这里，引入了一种新的方法来解决这个长期存在的“自旋”问题，以有效地计算季节性强迫模型中这些示踪剂的平衡分布。基于“安德森加速”，一种在20世纪60年代发展起来的用于求解非线性积分方程的序列加速技术，新方法完全是“黑箱”，比传统的直接时间积分提供了显著的加速。此外，它不需要预处理，确保示踪剂守恒，并与基础模型的数值时间步长方案完全一致。因此，它避免了其他方案的一些缺点，例如已经提出来解决这个问题的无矩阵Newton Krylov。专门为批量HPC系统上的海洋和气候模型通常运行的实现进行了描述，并说明了将其应用到各种地球化学示踪剂问题的方法。新方法提供了超过一个数量级的速度，应该使这些示踪剂的模拟更加可行，并使其能够纳入IPCC等气候变化评估。
Ocean geochemical tracers such as radiocarbon, protactinium and thorium isotopes, and noble gases are widely used to constrain a range of physical and biogeochemical processes in the ocean. However, their routine simulation in global ocean circulation and climate models is hindered by the computational expense of integrating them to a steady state. Here, a new approach to this long‐standing “spin‐up” problem is introduced to efficiently compute equilibrium distributions of such tracers in seasonally‐forced models. Based on “Anderson Acceleration,” a sequence acceleration technique developed in the 1960s to solve nonlinear integral equations, the new method is entirely “black box” and offers significant speed‐up over conventional direct time integration. Moreover, it requires no preconditioning, ensures tracer conservation and is fully consistent with the numerical time‐stepping scheme of the underlying model. It thus circumvents some of the drawbacks of other schemes such as matrix‐free Newton Krylov that have been proposed to address this problem. An implementation specifically tailored for the batch HPC systems on which ocean and climate models are typically run is described, and the method illustrated by applying it to a variety of geochemical tracer problems. The new method, which provides speed‐ups by over an order of magnitude, should make simulations of such tracers more feasible and enable their inclusion in climate change assessments such as IPCC.