ABSTRACT This study investigates the response of the subtropical gyre circulation in the North Pacific Ocean to quadrupled CO2 using the Community Earth System Model, version 1 (CESM1). In particular, an overriding technique is applied to isolate and quantify the effects of wind stress and thermal warming caused by CO2 emissions. Results show that, in response to the increase in CO2, the total mass transport in the subtropical gyre is reduced by approximately 11%. This reduction results mainly from negative anomalies of the wind stress curl over the subtropical region, with a smaller contribution from the thermal warming effect. Furthermore, a detailed analysis finds that the change in the subtropical gyre is baroclinic in nature [i.e., the gyre appears to be spin-up in the upper ocean (above 300 m) but spin-down in the lower thermocline (from 300 to 1500 m)]. This reversal between the upper ocean and lower thermocline is a result of the thermal warming effect, which intensifies ocean stratification, hindering the transfer of momentum from the upper layers to the lower layers and leading to an acceleration of the gyre in the upper ocean but a deceleration in the lower thermocline. Another feature of the response of the subtropical gyre to quadrupled CO2 is the respective poleward and equatorward movements of its northern and southern boundaries, which is a result of the change in the zero wind stress curl lines.

中文翻译：

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北太平洋副热带环流对二氧化碳四倍增的响应

摘要 本研究使用社区地球系统模型第 1 版 (CESM1) 调查了北太平洋亚热带环流对四倍 CO2 的响应。特别是，应用了一种压倒一切的技术来隔离和量化由二氧化碳排放引起的风应力和热变暖的影响。结果表明，随着二氧化碳的增加，亚热带环流中的总质量传输减少了大约 11%。这种减少主要是由于亚热带地区风应力卷曲的负异常造成的，热增暖效应的贡献较小。此外，详细分析发现，副热带环流的变化本质上是斜压的[即，环流似乎在海洋上部（300 m 以上）自旋向上，但在温跃层下部（300 至 1500 m）自旋向下]。上层海洋和下层温跃层之间的这种逆转是热变暖效应的结果，它加剧了海洋分层，阻碍了动量从上层向下层的转移，导致上层海洋的环流加速，但在较低的温跃层减速。副热带环流对四倍 CO2 响应的另一个特征是其南北边界分别向极地和赤道移动，这是零风应力旋度线变化的结果。阻碍动量从上层转移到下层，导致上层海洋的环流加速，但下层温跃层减速。副热带环流对四倍 CO2 响应的另一个特征是其南北边界分别向极地和赤道移动，这是零风应力旋度线变化的结果。阻碍动量从上层转移到下层，导致上层海洋的环流加速，但下层温跃层减速。副热带环流对四倍 CO2 响应的另一个特征是其南北边界分别向极地和赤道移动，这是零风应力旋度线变化的结果。