Multi-year La Niña events cause prolonged climate disruptions worldwide, but a systematic understanding of the underlying mechanisms is not yet established. Here we show using observations and models from the sixth phase of Coupled Model Intercomparison Project that a greater frequency of consecutive La Niña events is tied to the upper equatorial Pacific Ocean when it favors more rapid heat discharge. The propensity for heat discharge is underscored by negative skewness in upper-ocean heat content, underpinned by southward tropical Pacific wind shift during austral summer. Models with stronger westerly anomalies south of the equator simulate steeper east-to-west upward tilt of the thermocline that is favorable for a greater discharge rate. This highlights the crucial role of the southward wind shift in the nonlinear system of the El Niño-Southern Oscillation. The large inter-model spread in multi-year La Niña processes underscores the need in constraining models for reliable climate prediction and projection.

多年的拉尼娜事件在全球范围内造成了长期的气候破坏，但对其潜在机制的系统了解尚未建立。在这里，我们使用耦合模型比对项目第六阶段的观测和模型表明，连续拉尼娜事件的较高频率与赤道上太平洋有关，因为它有利于更快速的热量排放。上层海洋热含量的负偏度强调了热量排放的倾向，而南半球夏季期间热带太平洋南移的风向则强化了这一趋势。赤道以南西风异常较强的模型模拟了温跃层自东向西向上倾斜的更陡峭，这有利于更大的排放率。这凸显了南向风移在厄尔尼诺-南方涛动非线性系统中的关键作用。多年拉尼娜过程中模型间的巨大传播强调了约束模型以实现可靠的气候预测和预测的必要性。