Data_Sheet_1_Assessment of the Skill of Coupled Physical–Biogeochemical Models in the NW Mediterranean.docx

Numerical modeling is a key tool to complement the current physical and biogeochemical observational datasets. It is essential for understanding the role of oceanographic processes on marine food webs and producing climate change projections of variables affecting key ecosystem functions. In this work, we evaluate the horizontal and vertical patterns of four state-of-the-art coupled physical–biogeochemical models, three of them already published. Two of the models include data assimilation, physical and/or biological, and two do not. Simulations are compared to the most exhaustive dataset of in situ observations in the North Western Mediterranean, built ad hoc for this work, comprising gliders and conventional CTD surveys and complemented with satellite observations. The analyses are performed both in the whole domain and in four subregions (Catalan Shelf, Ebro Delta, Mallorca Channel, and Ibiza Channel), characterized by a priori divergent primary production dynamics and driving mechanisms. Overall, existing models offer a reasonable representation of physical processes including stratification, surface temperature, and surface currents, but it is shown that relatively small differences among them can lead to large differences in the response of biogeochemical variables. Our results show that all models are able to reproduce the main seasonal patterns of primary production both at the upper layer and at the deep chlorophyll maximum (DCM), as well as the differential behavior of the four subregions. However, there are significant discrepancies in the local variability of the intensity of the winter mixing, phytoplankton blooms, or the intensity and depth of the DCM. All model runs show markedly contrasting patterns of interannual phytoplankton biomass in all four subregions. This lack of robustness should dissuade end users from using them to fill gaps in time series observations without assessing their appropriateness. Finally, we discuss the usability of these models for different applications in marine ecology, including fishery oceanography.

数值模拟是补充现有物理和生物地球化学观测数据集的关键工具。对于理解海洋学过程对海洋食物网的作用以及产生影响关键生态系统功能的气候变化预测，至关重要。在本研究中，我们评估了四种最先进的耦合物理-生物地球化学模型的水平与垂直模式，其中三种已经发表。其中两种模型包括物理和/或生物数据同化，而另外两种则没有。模拟结果与为本研究专门构建的、包含无人机和传统CTD调查的最详尽的西北地中海现场观测数据集进行了比较，并辅以卫星观测。分析既在整个领域进行，也在四个子区域（加泰罗尼亚大陆架、埃布罗三角洲、马略卡海峡和伊维萨海峡）进行，这些子区域具有先验的不同的初级生产动态和驱动机制。总体而言，现有模型对包括层结、表面温度和表面流在内的物理过程提供了合理的表征，但研究表明，它们之间相对较小的差异可能导致生物地球化学变量响应的显著差异。我们的结果显示，所有模型都能够再现上层和深层叶绿素最大值（DCM）处的主要季节性初级生产模式，以及四个子区域的差异性行为。然而，在冬季混合强度、浮游植物爆发或DCM强度和深度的地方变率方面存在显著差异。所有模型运行均显示出四个子区域中浮游植物生物量的年际变化模式的显著对比。这种缺乏稳健性的特点应劝阻最终用户在没有评估其适用性的情况下使用它们来填补时间序列观测中的空白。最后，我们讨论了这些模型在海洋生态学不同应用中的可用性，包括渔业海洋学。