Effects of Langmuir Turbulence on Upper Ocean Carbonate Chemistry
Effects of Langmuir Turbulence on Upper Ocean Carbonate Chemistry
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DOI：
10.1029/2018ms001486
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发表时间：
2017-06
影响因子：
6.8
通讯作者：
K. M. Smith;P. Hamlington;Kyle E. Niemeyer;B. Fox‐Kemper;N. Lovenduski
中科院分区：
文献类型：
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作者：
K. M. Smith;P. Hamlington;Kyle E. Niemeyer;B. Fox‐Kemper;N. Lovenduski
利用大涡模拟研究了波浪驱动的朗缪尔湍流对二氧化碳（CO2）海气通量的影响，该模拟以小尺度海洋混合层中碳酸盐化学的活跃反应为特点。使用三种类型的碳酸盐化学检查朗缪尔湍流的四种强度：时间依赖性化学、瞬时平衡化学和无反应。时间相关模型是通过使用计算奇异扰动分析减少详细的八种化学机制而获得的，从而产生氢离子（H+）的准稳态近似；即固定pH值。然后，使用对微分方程的刚性系统具有鲁棒性的龙格-库塔-切比雪夫方案，在平流求解之前和之后的两个半时间步骤中对简化机制进行积分。模拟表明，随着朗缪尔湍流强度的增加，近地表层的快速翻转增强了二氧化碳通量，这与时间依赖性反应的二氧化碳去除率相媲美。与更现实的时间相关模型相比，平衡化学模型和非反应模型分别将更多和更少的碳带入海洋。这些结果对忽略朗缪尔湍流或使用平衡而不是依赖时间的化学机制的地球系统模型具有影响。
Effects of wave‐driven Langmuir turbulence on the air‐sea flux of carbon dioxide (CO2) are examined using large eddy simulations featuring actively reacting carbonate chemistry in the ocean mixed layer at small scales. Four strengths of Langmuir turbulence are examined with three types of carbonate chemistry: time‐dependent chemistry, instantaneous equilibrium chemistry, and no reactions. The time‐dependent model is obtained by reducing a detailed eight‐species chemical mechanism using computational singular perturbation analysis, resulting in a quasi steady state approximation for hydrogen ion (H+); that is, fixed pH. The reduced mechanism is then integrated in two half‐time steps before and after the advection solve using a Runge‐Kutta‐Chebyshev scheme that is robust for stiff systems of differential equations. The simulations show that as the strength of Langmuir turbulence increases, CO2 fluxes are enhanced by rapid overturning of the near‐surface layer, which rivals the removal rate of CO2 by time‐dependent reactions. Equilibrium chemistry and nonreactive models are found to bring more and less carbon, respectively, into the ocean as compared to the more realistic time‐dependent model. These results have implications for Earth system models that either neglect Langmuir turbulence or use equilibrium, instead of time‐dependent, chemical mechanisms.