Effects of parameter indeterminacy in pelagic biogeochemical modules of Earth System Models on projections into a warming future: The scale of the problem
Effects of parameter indeterminacy in pelagic biogeochemical modules of Earth System Models on projections into a warming future: The scale of the problem
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DOI：
10.1002/2017gb005690
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发表时间：
2017-07-01
影响因子：
5.2
通讯作者：
Dietze, H.
中科院分区：
文献类型：
--
作者：
Loeptien, U.;Dietze, H.
数值地球系统模式是一种通用的工具，用于推断当前的气候条件到变暖的未来，并探索地球工程选择。当前大多数模式的特点是将简单的远洋生物地球化学模式成分嵌入到三维海洋环流模式中。这些生物地球化学模型成分的动力学本质上是由所谓的模型参数控制的，其中大多数是鲜为人知的。本文探讨了在一个完整的三维地球系统模型中通过最小化对噪声观测的不拟合来估计这些参数的可行性。重点是参数的可识别性。在早期研究的基础上，我们说明了确定这些参数的独特估计的问题，这些参数规定了营养和光耗尽条件对自养浮游植物碳同化的限制作用。我们的结果表明，对于典型的模型和评估指标，不存在有意义的“最佳”唯一参数集。我们发现了非常不同的参数集，一方面，它们与我们的（综合）历史观测结果同样一致，而另一方面，它们对气候变暖提出了截然不同的预测。
Numerical Earth System Models are generic tools used to extrapolate present climate conditions into a warming future and to explore geoengineering options. Most of the current-generation models feature a simple pelagic biogeochemical model component that is embedded into a three-dimensional ocean general circulation model. The dynamics of these biogeochemical model components is essentially controlled by so-called model parameters most of which are poorly known. Here we explore the feasibility to estimate these parameters in a full-fledged three-dimensional Earth System Model by minimizing the misfit to noisy observations. The focus is on parameter identifiability. Based on earlier studies, we illustrate problems in determining a unique estimate of those parameters that prescribe the limiting effect of nutrient-and light-depleted conditions on carbon assimilation by autotrophic phytoplankton. Our results showcase that for typical models and evaluation metrics no meaningful "best" unique parameter set exists. We find very different parameter sets which are, on the one hand, equally consistent with our (synthetic) historical observations while, on the other hand, they propose strikingly differing projections into a warming climate.