Calibration of key temperature-dependent ocean microbial processes in the cGENIE.muffin Earth system model
Calibration of key temperature-dependent ocean microbial processes in the cGENIE.muffin Earth system model
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DOI：
10.5194/gmd-2019-344
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发表时间：
2020-02
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影响因子：
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通讯作者：
K. Crichton;Jamie D. Wilson;A. Ridgwell;P. Pearson
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作者：
K. Crichton;Jamie D. Wilson;A. Ridgwell;P. Pearson
抽象的。温度是海洋碳循环中的一个主要参数，对各种固体和溶解反应物和底物的生物转化速度起着关键的控制作用。尽管在海洋碳循环数值模型的构建中，温度一直被认为是海洋表面有机物质生产和输出的关键参数，但在海洋内部却很少考虑到温度。在那里，细菌(主要)将下沉的颗粒有机物转化为其溶解成分，从而消耗溶解氧(和/或其他电子受体，如硫酸盐)并释放营养物质，然后这些营养物质可用于运输回表面。在这里，我们提出并校准了cGENIE.muffin地球系统模型中更完整的海洋碳循环随温度变化的表示，该模型旨在用于过去和未来的气候应用。在这方面，我们结合了依赖温度的有机物下沉再矿化计划和生物出口生产计划，该计划还包括对表层水域养分吸收(因此浮游植物生长)的温度依赖限制。通过参数集合，我们通过统计对比营养物质、氧气和海洋中溶解无机碳的稳定碳同位素特征(δ13C)的投影场与现代观测，联合校准了这两个参数。我们发现，就目前而言，与现有的cGENIE.muffin的调谐非温度依赖版本相比，温度依赖版本显示出与数据一样好或更好的拟合。增加依赖温度的再矿化的主要影响是在较温暖的水域推动更高的再矿化速率，从而使营养物质更快地返回那里的表面--刺激有机物质的产生。因此，与标准模型相比，在中低纬度较温暖的水域，80米以下输出的有机质更多。相反，在高纬度地区，由于原位再矿化速度较慢，较低的水温降低了向地表供应养分的速度。我们还通过分析一系列历史的瞬变实验，评估了包括一组更完整的依赖于温度的参数化的影响。我们发现，从工业化前到现在，随着模拟的气温上升0.9°C和海洋变暖0.12°C(表层水域0.6°C，深海0.02°C)，80米处的POC出口仅减少0.3%。相比之下，在没有假定的依赖温度的生物过程的情况下，由于海洋分层和对地表营养物质供应的减少，全球80米处的POC出口在工业化前和现在之间下降了2.9%。这表明，在变暖的条件下，增加营养物质的循环，抵消了在变暖的世界中层化导致的表面营养限制的一部分，然后更少的碳(和营养物质)进入内部和深海。CGENIE.muffin地球系统模型的这一扩展为其提供了额外的能力，以解决过去和未来变暖世界中的海洋碳循环问题。
Abstract. Temperature is a master parameter in the marine carbon cycle, exerting a critical control on the rate of biological transformation of a variety of solid and dissolved reactants and substrates. Although in the construction of numerical models of marine carbon cycling, temperature has been long-recognised as a key parameter in the production and export of organic matter at the ocean surface, it is much less commonly taken into account in the ocean interior. There, bacteria (primarily) transform sinking particulate organic matter into its dissolved constituents and thereby consume dissolved oxygen (and/or other electron acceptors such as sulphate) and release nutrients, which are then available for transport back to the surface. Here we present and calibrate a more complete temperature-dependent representation of marine carbon cycling in the cGENIE.muffin Earth system model, intended for both past and future climate applications. In this, we combine a temperature-dependent remineralisation scheme for sinking organic matter with a biological export production scheme that also includes a temperature-dependent limitation on nutrient uptake in surface waters (and hence phytoplankton growth). Via a parameter ensemble, we jointly calibrate the two parameterisations by statistically contrasting model projected fields of nutrients, oxygen, and the stable carbon isotopic signature (δ13C) of dissolved inorganic carbon in the ocean, with modern observations. We find that for the present-day, the temperature-dependent version shows as-good-as or better fit to data than the existing tuned non-temperature dependent version of the cGENIE.muffin. The main impact of adding temperature-dependent remineralisation is in driving higher rates of remineralisation in warmer waters and hence a more rapid return of nutrients to the surface there – stimulating organic matter production. As a result, more organic matter is exported below 80 m in mid and low latitude warmer waters as compared to the standard model. Conversely, at higher latitudes, colder water temperature reduces the rate of nutrient supply to the surface as a result of slower in-situ rates of remineralisation. We also assess the implications of including a more complete set of temperature-dependent parameterisations by analysing a series of historical transient experiments. We find that between the pre-industrial and the present day, in response to a simulated air temperature increase of 0.9 °C and ocean warming of 0.12 °C (0.6 °C in surface waters and 0.02 °C in deep waters), a reduction in POC export at 80 m of just 0.3 % occurs. In contrast, with no assumed temperature-dependent biological processes, global POC export at 80 m falls by 2.9 % between the pre-industrial and present day as a consequence of ocean stratification and reduced nutrient supply to the surface. This suggests that increased nutrient recycling in warmer conditions offsets some of the stratification-induced surface nutrient limitation in a warmer world, and that less carbon (and nutrients) then reaches the inner and deep ocean. This extension to the cGENIE.muffin Earth system model provides it with additional capabilities in addressing marine carbon cycling in warmer past and future worlds.