Abstract. Direct comparison between paleo oceanic δ¹³C records and model results facilitates assessing simulated distributions and properties of water masses in the past. To accomplish this, we include a new representation of the stable carbon isotope ¹³C into the HAMburg Ocean Carbon Cycle model (HAMOCC), the ocean biogeochemical component of the Max Planck Institute Earth System Model (MPI-ESM). ¹³C is explicitly resolved for all existing oceanic carbon pools. We account for fractionation during air-sea gas exchange and for biological fractionation ε_p associated with photosynthetic carbon fixation during phytoplankton growth. We examine two ε_p parameterisations of different complexity: ε_p^Popp varies with surface dissolved CO₂ concentration (Popp et al., 1989), while ε_p^Laws additionally depends on local phytoplankton growth rates (Laws et al., 1995). When compared to observations of δ¹³C in dissolved inorganic carbon (DIC), both parameterisations yield similar performance. However, with regard to δ¹³C in particulate organic carbon ε_p^Popp shows a considerably improved performance than ε_p^Laws, because the latter results in a too strong preference for ¹²C. The model also well reproduces the oceanic ¹³C Suess effect, i.e. the intrusion of the isotopically light anthropogenic CO₂ into the ocean, based on comparison to other existing ¹³C models and to observation-based oceanic carbon uptake estimates over the industrial period. We further apply the approach of Eide et al. (2017a), who derived the first global oceanic ¹³C Suess effect estimate based on observations, to our model data that has ample spatial and temporal coverage. With this we are able to analyse in detail the underestimation of ¹³C Suess effect by this approach as it has been noted by Eide et al. (2017a). Based on our model we find underestimations of ¹³C Suess effect at 200 m by 0.24 ‰ in the Indian Ocean, 0.21 ‰ in the North Pacific, 0.26 ‰ in the South Pacific, 0.1 ‰ in the North Atlantic and 0.14 ‰ in the South Atlantic. We attribute the major sources of the underestimation to two assumptions in Eide et al. (2017a)'s approach: a spatially-constant preformed component of δ¹³C_DIC in year 1940 and neglecting ¹³C Suess effect in CFC-12 free water.

中文翻译：

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在马克斯·普朗克研究所地球系统模型的海洋生物地球化学成分中纳入稳定的碳同位素¹³ C

摘要。古海洋δ之间的直接比较¹³ Ç记录和模型结果评估功能有助于模拟分布和过去水团的性质。为了实现这一目标，我们将稳定碳同位素¹³ C的新表示形式引入了汉堡堡海洋碳循环模型（HAMOCC），这是马克斯·普朗克研究所地球系统模型（MPI-ESM）的海洋生物地球化学成分。¹³ C被明确地解决了所有现有的海洋碳库。我们考虑在海气气体交换和生物分馏ε分馏_p浮游植物的生长过程中与光合固碳相关。我们介绍两种ε _p不同复杂的参数化：ε_p^波普与表面溶解的CO变化₂浓度（Popp等人，1989），而ε _p^法律另外取决于本地浮游植物生长速率（Laws等人，1995）。当相比于δ的观察¹³中溶解的无机碳（DIC）C，两参数化得到类似的性能。然而，对于δ ¹³中颗粒有机碳εÇ _p ^Popp的节目比ε相当改进的性能_p^法，因为在太强烈偏好后者结果¹² C.该模型还很好再现海洋¹³C Suess效应，即与其他现有的¹³ C模型进行比较，以及与工业期内基于观测的海洋碳吸收量估计值相比，同位素轻的人为CO ₂进入海洋。我们进一步应用Eide等人的方法。（2017a），他根据观测结果得出了我们的第一个全球大洋¹³ C Suess效应估计值，并将其推导出我们的具有足够时空覆盖范围的模型数据。这样，我们就可以详细分析这种方法对¹³ C Suess效应的低估，正如Eide等人已经指出的那样。（2017a）。根据我们的模型，我们发现低估了¹³C在200 m处的Suess效应在印度洋为0.24‰，在北太平洋为0.21‰，在南太平洋为0.26‰，在北大西洋为0.1‰，在南大西洋为0.14‰。我们将低估的主要来源归因于Eide等人的两个假设。（2017A）的方法：δ的空间上恒定预成型部件¹³ Ç _DIC在1940年和忽视¹³在CFC-12自由水C休斯效果。