The oceanic surface pressure of CO2 (pCO2) is an essential parameter for understanding the global and regional carbon cycle and the oceanic carbon uptake capacity. We constructed a three-dimensional physical-biogeochemical model with a high resolution of 1/30° for the South China Sea (SCS) to compensate for the limited temporal coverage and limited spatial resolution of the observations and numerical models. The model simulated oceanic surface pCO2 from 1992 to 2021, and the empirical orthogonal function analysis (EOF) of the model results is conducted for a better understanding of the seasonal and interannual variations of oceanic surface pCO2 in this region. The model results showed that the SCS serves as an atmospheric CO2 source from March to October and a sink from November to February, with a domain-averaged climatological oceanic surface pCO2 value that varies between 357 and 408 μatm, and the temporal variation was positively correlated with the variation of sea surface temperature (SST). The majority of the SCS showed a long-term increasing trend for oceanic surface pCO2 with a value of (1.19±0.60) μatm/a, which is in response to the continuously rising atmospheric CO2 concentration. The first EOF mode is positively correlated with the Niño 3 index with a correlation coefficient of 0.51 when the Niño 3 leads 5 months, and the second EOF mode is correlated with the PDO index when the PDO leads 7 months, which suggests an influence of climate variability on the carbonate system. Moreover, it was found that the long-term trend rate of oceanic surface pCO2 was mainly controlled by total CO2 (TCO2) through the decomposition of influence factors, and SST variation took a dominant role in seasonal variations of pCO2. With rapid global warming and continuous release of CO2, the carbonate system in the SCS may change leading to calcite and aragonite saturation.

中文翻译：

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基于三维高分辨率生物地球化学模型的南海海面pCO2控制因素分析

CO 的海洋表面压力2个(p一氧化碳2个) 是了解全球和区域碳循环以及海洋碳吸收能力的重要参数。我们为南海 (SCS) 构建了一个分辨率为 1/30° 的三维物理-生物地球化学模型，以弥补观测和数值模型的有限时间覆盖和有限空间分辨率。该模型模拟海洋表面p一氧化碳2个从1992年到2021年，并对模型结果进行经验正交函数分析（EOF），以更好地了解海洋表面的季节和年际变化p一氧化碳2个在这个地区。模型结果表明，SCS 作为大气 CO2个3 月至 10 月的源和 11 月至 2 月的汇，具有域平均气候海洋表面p一氧化碳2个值在 357 和 408 μatm 之间变化，时间变化与海面温度（SST）的变化呈正相关。南海绝大部分海面呈长期增加趋势p一氧化碳2个值为（1.19±0.60）μatm/a，响应大气中CO持续升高2个专注。第一种EOF模态与Niño 3指数正相关，当Niño 3超前5个月时，相关系数为0.51；当PDO超前7个月时，第二种EOF模态与PDO指数相关，表明气候的影响碳酸盐系统的变异性。此外，还发现海洋表面的长期趋势率p一氧化碳2个主要受控于总CO2个（总拥有成本2个)通过影响因素的分解，SST变化在季节变化中起主导作用p一氧化碳2个. 随着全球迅速变暖和CO的不断释放2个，南海的碳酸盐系统可能发生变化，导致方解石和文石饱和。