Understanding the natural variability of pH and aragonite saturation state (Ω_arag) is important for assessing ocean acidification (OA) impacts especially in the coastal ocean since anthropogenic CO₂ increase‐induced OA is often superimposed by their natural variability. Here, we report the seasonal variability of sea surface pH and Ω_arag from spring to summer in the Jiaozhou Bay (JZB) and compare their controls based on two cruises conducted in April and August 2018. Results show that sea surface pH on the NBS scale slightly increases from 8.10 ± 0.05 in spring to 8.13 ± 0.04 in summer, whereas surface Ω_arag substantially increases from 2.05 ± 0.18 in spring to 3.34 ± 0.25 in summer. The difference in pH and Ω_arag seasonal increase is related to the contrasting temperature effects on them, which can be divided into the first temperature effect associated with acid‐base equilibrium of the CO₂ system and the second temperature effect associated with CO₂ solubility‐driven air‐sea exchange. The two temperature effects have opposite influences on pH, canceling each other and causing a relatively small seasonal variability of pH, while they have consistent influences on Ω_arag, reinforcing each other and causing a relatively large variability of Ω_arag. Also, through both qualitative analyses and a 1‐D model, we identify the processes controlling the seasonal variability of pH and Ω_arag. We find air‐sea exchange dominates the seasonal variability of pH and Ω_arag in nearshore areas, while biological production is the most important in the central part of the JZB.

中文翻译：

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北部大温带海湾中控制海面pH和文石饱和状态的过程：对比温度效应

了解pH和文石饱和状态（_Ωarag）的自然变异性对于评估海洋酸化（OA）的影响非常重要，尤其是在沿海海洋中，因为人为CO ₂增加导致的OA通常被其自然变异性叠加。在这里，我们报告了胶州湾（JZB）从春季到夏季海面pH和Ω_阿拉格的季节性变化，并基于2018年4月和2018年8月进行的两次航行比较了它们的控制。结果显示，NBS规模的海面pH从春季的8.10±0.05略微增加到夏季的8.13±0.04，而表面Ω_摩擦系数从春季的2.05±0.18显着增加到夏季的3.34±0.25。pH和Ω电阻的_差异季节性增加与对它们的反差温度效应有关，可分为与CO ₂系统酸碱平衡有关的第一温度效应和与CO ₂溶解度驱动的海气交换有关的第二温度效应。两种温度效应对pH有相反的影响，彼此抵消并导致相对较小的pH季节变化，而它们对Ω_阿拉格具有一致的影响，彼此增强并导致_Ωarag相对较大的变化。此外，通过定性分析和一维模型，我们确定了控制pH和_Ωarag季节性变化的_过程。。我们发现，在近海地区，海-气交换主导着pH和Ω_耕作的季节变化，而生物生产在JZB的中部最为重要。