The temperature range of Earth's open‐ocean waters is roughly 0–30°C, yet our understanding of the seawater carbon dioxide (CO2) system is largely derived from analyses conducted within a narrow temperature range (e.g., laboratory temperature of 20°C or 25°C). Herein, we address two aspects of open‐ocean CO2‐system measurements and modeling: (1) a highly precise spectrophotometric technique is used to determine bicarbonate dissociation constants (K2) in seawater at temperatures as low as 3°C and (2) a cruise dataset uniquely including total scale pH measurements at two temperatures is used for CO2‐system internal consistency comparisons at 12°C and 25°C. Our pK2 parameterization (where pK = −log K) is applicable for broad ranges of salinity (20 ≤ SP ≤ 40) and temperature (3°C ≤ t ≤ 35°C). Our CO2‐system internal consistency evaluation (comparison of measured and calculated CO2‐system parameters) utilized data obtained during NOAA's 2021 West Coast Ocean Acidification Cruise: total alkalinity (TA), total dissolved inorganic carbon (DIC), pH measured at 25°C, and pH measured at 12°C (n = 265). Results demonstrate that, relative to calculations utilizing the TA, DIC pair, agreement between measured and calculated parameters is improved when either TA or DIC is paired with pH measurements at either temperature. Calculations of CO2 fugacity (fCO2) and aragonite saturation state (Ωar) using pH measurements made at 25°C or 12°C (paired with either TA or DIC) are statistically indistinguishable. Results also suggest that the temperature dependence of current CO2‐system dissociation constants need further refinement.

中文翻译：

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分光光度法得出的海水 CO2 系统评估：使用 pH 值进行参数计算不需要在标准温度下进行测量


地球公海水域的温度范围大约为 0–30°C，但我们对海水二氧化碳 (CO2) 系统的了解很大程度上来自于在狭窄温度范围内进行的分析（例如，实验室温度 20°C 或25°C）。在此，我们讨论了公海二氧化碳系统测量和建模的两个方面：(1) 使用高精度分光光度技术来确定温度低至 3°C 的海水中的碳酸氢盐解离常数 (K2)，以及 (2) Cruise 数据集独特地包括两个温度下的总规模 pH 测量值，用于 12°C 和 25°C 下的 CO2 系统内部一致性比较。我们的 pK2 参数化（其中 pK = −log K）适用于广泛的盐度 (20 ≤ SP ≤ 40) 和温度 (3°C ≤ t ≤ 35°C) 范围。我们的二氧化碳系统内部一致性评估（测量和计算的二氧化碳系统参数的比较）利用了 NOAA 2021 年西海岸海洋酸化巡航期间获得的数据：总碱度 (TA)、总溶解无机碳 (DIC)、25°C 下测量的 pH 值，并在 12°C 下测量 pH (n = 265)。结果表明，相对于使用 TA、DIC 对的计算，当 TA 或 DIC 与任一温度下的 pH 测量配对时，测量参数和计算参数之间的一致性得到改善。使用 25°C 或 12°C（与 TA 或 DIC 配对）进行的 pH 测量计算 CO2 逸度 (fCO2) 和文石饱和态 (Ωar) 在统计上是无法区分的。结果还表明，当前 CO2 系统解离常数的温度依赖性需要进一步完善。