Climate response to low warming scenarios that meet 2015 Paris Agreement is distinct from that to the medium/high-emissions scenarios analyzed in previous studies. The present study investigates changes in the North Pacific subtropical gyre and the underlying mechanisms under 1.5 °C low warming scenario by 11-member ensemble simulations from the Community Earth System Model. Specifically, atmospheric CO₂ concentration peaks in 2036 and then decreases, with global mean surface temperature (GMST) first increasing and then stabilizing after 2045. The changes of the lower thermocline depth are consistently weaker in the subtropics than in the tropics or high latitudes through 2100. During GMST increasing stage, the subtropical circulation strengthens in the upper 1000 m north of 30° N as a result of the enhanced wind stress. When GMST stabilizes, the subtropical circulation strengthens in the surface layer (0–150 m) and the main thermocline (150–600 m) but displays insignificant change in the intermediate layer (600–1000 m). Wind and stratification changes are both important in driving the North Pacific subtropical gyre changes, because sea surface warming is much weaker in the low warming scenario than that in the medium/high-emissions scenarios. In addition, as the surface wind change displays substantial natural variability and is strongly model-dependent, it dominates the differences in projected subtropical circulation changes across models. This study highlights the importance of wind changes in projections of the subtropical circulation changes under low warming scenarios.

符合2015年《巴黎协定》的低变暖情景对气候的响应不同于先前研究中分析的中/高排放情景。本研究通过社区地球系统模型的11人整体模拟研究了1.5°C低温变暖情况下北太平洋亚热带回旋的变化及其潜在机理。具体而言，大气CO ₂浓度在2036年达到峰值，然后下降，全球平均表面温度（GMST）首先升高，然后在2045年之后趋于稳定。直到2100年，亚热带的低跃层深度的变化始终比热带或高纬度弱。在这一阶段，由于风应力的增加，亚热带环流在30°N以北1000 m的上部增强。当GMST稳定后，副热带环流在表层（0–150 m）和主温跃层（150–600 m）处增强，但在中间层（600–1000 m）中显示出很小的变化。风和分层的变化对于推动北太平洋亚热带回旋的变化都非常重要，因为低变暖情景中的海面变暖远弱于中/高排放情景。此外，由于地表风的变化显示出很大的自然变异性，并且强烈依赖于模型，因此它主导了整个模型中预计的亚热带环流变化的差异。这项研究突出了在低变暖情况下，风向变化对亚热带环流变化预测的重要性。