Climate change will affect both the mean state and seasonality of marine physical and biogeochemical properties, with important implications for the oceanic sink of atmospheric CO₂. Here, we investigate the seasonal cycle of the air‐sea exchange of CO₂ and pCO_2,sw (surface seawater pCO₂) and their long term changes using the CMIP6 submission of the NASA‐GISS modelE (GISS‐E2.1‐G). In comparison to the CMIP5 submission (GISS‐E2‐R), we find that on the global scale, the seasonal cycles of the CO₂ flux and NPP have improved, while the seasonal cycles of dissolved inorganic carbon (DIC), alkalinity, and macronutrients have deteriorated. Moreover, for all ocean biogeochemistry fields, changes in skill between E2.1‐G and E2‐R display large regional variability. For E2.1‐G, we find similar modeled and observed CO₂ flux seasonal cycles in the subtropical gyres, where seasonal anomalies of pCO_2,sw and the flux are temperature‐driven, and the Southern Ocean, where anomalies are DIC‐driven. Biases in these seasonal cycles are largest in the subpolar and equatorial regions, driven by a combination of biases in temperature, DIC, alkalinity, and wind speed. When comparing the historical simulation to a simulation with an idealized increase in atmospheric pCO₂, we find that the seasonal amplitudes of the CO₂ flux and pCO_2,sw generally increase. These changes are produced by increases in the sensitivity of pCO_2,sw to its respective drivers. These findings are consistent with the notion that the seasonality of pCO_2,sw is expected to increase due to the increase of atmospheric pCO₂, with changes in the seasonality of temperature, DIC, and alkalinity having secondary influences.

中文翻译：

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NASA‐GISS模型CMIP6提交中海气CO2通量季节性的驱动因素及其长期变化

气候变化将影响海洋物理和生物地球化学特性的平均状态和季节性，这对大气中CO ₂的海洋吸收具有重要意义。在这里，我们使用NASA‐GISS modelE（GISS‐E2.1‐G）的CMIP6提交文件，调查了CO ₂和pCO _2，sw（地表海水pCO ₂）的海-气交换的季节性周期及其长期变化。 ）。与CMIP5提交文件（GISS-E2-R）相比，我们发现在全球范围内，CO ₂的季节性周期通量和NPP有所改善，而溶解的无机碳（DIC），碱度和大量营养素的季节性循环却恶化了。此外，对于所有海洋生物地球化学领域，E2.1-G和E2-R之间的技能变化都显示出较大的区域差异。对于E2.1-G，我们在亚热带回旋中发现了相似的模拟和观测到的CO ₂通量季节周期，其中pCO _2，sw和通量的季节异常是温度驱动的，而南大洋中DIC驱动异常的南部海洋。在温度，DIC，碱度和风速的偏差共同作用下，这些季节性周期中的偏差在亚极和赤道地区最大。将历史模拟与理想pCO ₂增加的模拟进行比较时中，我们发现，对CO的季节性振幅₂通量和的pCO _2，SW通常增加。这些变化是由于pCO _{2 sw}对相应驱动器的敏感性增加而产生的。这些发现与概念，即PCO的季节性一致_2，SW预计将增加由于大气的pCO的增加₂，在温度，DIC，以及具有次级影响碱度的季节性变化。