SICOPOLIS-AD v1: an open-source adjoint modeling framework for ice sheet simulation enabled by the algorithmic differentiation tool OpenAD
SICOPOLIS-AD v1: an open-source adjoint modeling framework for ice sheet simulation enabled by the algorithmic differentiation tool OpenAD
复制标题
DOI：
10.5194/gmd-13-1845-2020
复制
发表时间：
2020-04
影响因子：
5.1
通讯作者：
Liz C. Logan;S. Narayanan;R. Greve;P. Heimbach
中科院分区：
文献类型：
--
作者：
Liz C. Logan;S. Narayanan;R. Greve;P. Heimbach
抽象的。我们介绍了冰盖模型SICOPOLIS的一种新功能，该功能通过使用开源算法微分(AD)工具OpenAD通过源代码转换来实现灵活的伴随代码生成。伴随代码可以有效地计算标量值目标函数或兴趣量(QOI)对一系列重要的、通常在空间上变化的和不确定的模型输入变量的敏感度，包括初始和边界条件以及模型参数。与以前关于SICOPOLIS伴随代码生成的工作相比，我们的工作取得了几个重要进展：(I)它嵌入到SICOPOLIS储存库的最新主干中--进行了1.5年的代码开发和改进--并随时可供更广泛的社区使用；(Ii)所使用的AD工具OpenAD是一个开源工具；(Iii)所开发的伴随代码既适用于格陵兰，也适用于南极洲，包括浮冰和浮冰，具有广泛的热力学表示选择。需要执行许多代码重构步骤。它们将在附录中详细讨论，因为它们提供了将AD应用于整个遗留代码的经验教训。作为一个应用实例，我们考察了南极冰盖总体积对初始冰厚度、南半球夏季降水以及整个冰盖的基温和表面温度变化的敏感性。对南极浮冰架的模拟表明，经过100多年的模拟，总冰盖体积对初始冰层厚度和降水的敏感性几乎一致为正，而对地表温度和基温的敏感性几乎一致为负。在从莫德女王到玛丽女王岛的漂浮冰架上，对南半球夏季降水的敏感性最大。对初始冰层厚度最敏感的是南极洲周围的出口冰川。总冰盖体积对表面温度和基础温度敏感性的比较表明，浮冰架的表面温度敏感性普遍较高，而浮冰架和出口冰川的接地线上的基础温度敏感性最高。东极洲均匀扰动区域表明，在这里测试的四个控制变量中，总冰盖体积对SICOPOLIS公式中的南半球夏季降水变化最敏感。对伴随灵敏度和有限差分导出灵敏度的比较显示出很好的一致性，从而使人们相信AD工具正在生成正确的伴随代码。新的建模基础设施在开发主干下的http://www.sicopolis.net(上次访问：2020年4月2日)上免费提供。
Abstract. We present a new capability of the ice sheet model SICOPOLIS that enables flexible adjoint code generation via source transformation using the open-source algorithmic differentiation (AD) tool OpenAD. The adjoint code enables efficient calculation of the sensitivities of a scalar-valued objective function or quantity of interest (QoI) to a range of important, often spatially varying and uncertain model input variables, including initial and boundary conditions, as well as model parameters. Compared to earlier work on the adjoint code generation of SICOPOLIS, our work makes several important advances: (i) it is embedded within the up-to-date trunk of the SICOPOLIS repository – accounting for 1.5 decades of code development and improvements – and is readily available to the wider community; (ii) the AD tool used, OpenAD, is an open-source tool; (iii) the adjoint code developed is applicable to both Greenland and Antarctica, including grounded ice as well as floating ice shelves, with an extended choice of thermodynamical representations. A number of code refactorization steps were required. They are discussed in detail in an Appendix as they hold lessons for the application of AD to legacy codes at large. As an example application, we examine the sensitivity of the total Antarctic Ice Sheet volume to changes in initial ice thickness, austral summer precipitation, and basal and surface temperatures across the ice sheet. Simulations of Antarctica with floating ice shelves show that over 100 years of simulation the sensitivity of total ice sheet volume to the initial ice thickness and precipitation is almost uniformly positive, while the sensitivities to surface and basal temperature are almost uniformly negative. Sensitivity to austral summer precipitation is largest on floating ice shelves from Queen Maud to Queen Mary Land. The largest sensitivity to initial ice thickness is at outlet glaciers around Antarctica. Comparison between total ice sheet volume sensitivities to surface and basal temperature shows that surface temperature sensitivities are higher broadly across the floating ice shelves, while basal temperature sensitivities are highest at the grounding lines of floating ice shelves and outlet glaciers. A uniformly perturbed region of East Antarctica reveals that, among the four control variables tested here, total ice sheet volume is the most sensitive to variations in austral summer precipitation as formulated in SICOPOLIS. Comparison between adjoint- and finite-difference-derived sensitivities shows good agreement, lending confidence that the AD tool is producing correct adjoint code. The new modeling infrastructure is freely available at http://www.sicopolis.net (last access: 2 April 2020) under the development trunk.