Reciprocal bias compensation and ensuing uncertainties in model-based climate projections: pelagic biogeochemistry versus ocean mixing
Reciprocal bias compensation and ensuing uncertainties in model-based climate projections: pelagic biogeochemistry versus ocean mixing
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DOI：
10.5194/bg-16-1865-2019
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发表时间：
2019-05-06
期刊：
影响因子：
4.9
通讯作者：
Dietze, Heiner
中科院分区：
文献类型：
--
作者：
Loeptien, Ulrike;Dietze, Heiner
人为排放的温室气体（如CO2和N2O）影响地球系统，进而调节大气中温室气体的浓度。潜在的反馈机制很复杂，有时甚至违反直觉。所谓的地球系统模型最近已经成熟为标准工具，以评估在变暖的世界中这些反馈机制。这些模型的应用范围从针对基本过程的理解到地球工程方案的评估。所有这些应用的一个普遍问题是需要根据观测数据（例如，营养场）估计知之甚少的模型参数，特别是生物地球化学成分的模型参数。在本研究中，我们用一个地球系统模型说明，通过这种方法，物理海洋环流模式组件中的偏差和其他模式缺陷可以相互补偿远洋生物地球化学模式组件中的偏差（反之亦然）。我们提出了两种模型配置，当受历史边界条件驱动时，它们具有非常相似的稳态（基于特别措施），尽管它们具有海洋混合和生物地球化学循环的本质不同的配置（参数集）。当预测到未来时，模型响应之间的相似性就中断了。随着地球变暖，海洋总碳含量和亚氧体积的变化等指标在不同的模式配置中出现了分歧。我们的研究结果重申，推进对海洋混合过程的理解将减少未来海洋生物地球化学循环预测的不确定性。关于后者，我们建议对海洋生物地球化学循环的深入了解可以用于海洋环流模块的改进。
Anthropogenic emissions of greenhouse gases such as CO2 and N2O impinge on the Earth system, which in turn modulates atmospheric greenhouse gas concentrations. The underlying feedback mechanisms are complex and, at times, counterintuitive. So-called Earth system models have recently matured to standard tools tailored to assess these feedback mechanisms in a warming world. Applications for these models range from being targeted at basic process understanding to the assessment of geo-engineering options. A problem endemic to all these applications is the need to estimate poorly known model parameters, specifically for the biogeochemical component, based on observational data (e.g., nutrient fields). In the present study, we illustrate with an Earth system model that through such an approach biases and other model deficiencies in the physical ocean circulation model component can reciprocally compensate for biases in the pelagic biogeochemical model component (and vice versa). We present two model configurations that share a remarkably similar steady state (based on ad hoc measures) when driven by historical boundary conditions, even though they feature substantially different configurations (parameter sets) of ocean mixing and biogeochemical cycling. When projected into the future the similarity between the model responses breaks. Metrics such as changes in total oceanic carbon content and suboxic volume diverge between the model configurations as the Earth warms. Our results reiterate that advancing the understanding of oceanic mixing processes will reduce the uncertainty of future projections of oceanic biogeochemical cycles. Related to the latter, we suggest that an advanced understanding of oceanic biogeochemical cycles can be used for advancements in ocean circulation modules.