Combining data from Argo and the TAO buoy array we present new observations of variability in the Pacific Ocean. Argo profiles reveal the development of a thickness anomaly in the lower levels of the ventilated thermocline of the South Pacific in 2010. Data through 2017 show this anomaly propagating as a baroclinic wave westward and towards the equator. Theory suggests that this wave will reduce the velocity of the equatorial undercurrent (EUC) when it reaches the equator, transitioning the equatorial Pacific to a warm state. This is supported by TAO array observations that show a past decadal shift in EUC strength around 2000, as well as radiocarbon coral measurements which suggest a similar change in the 1970s, both of which align with phase changes in Pacific decadal variability. Using model simulations with enhanced vertical resolution in the thermocline, we affirm this link between the subtropical south Pacific thermocline and the EUC, which also manifests in eastern Pacific sea surface temperatures. We combine these results to hypothesize a mechanism that may explain some of the decadal variability observed in the Pacific. This mechanism relies on the propagation of anomalies in the structure of the ventilated thermocline from the southeastern Pacific to the equatorial Pacific, modulating the strength of the EUC. The cycle is enhanced by atmospheric teleconnections between the equatorial Pacific and the southeast Pacific that periodically reverse the anomaly in thermocline thickness. If correct, our hypothesis predicts a return to a warm state of the equatorial Pacific when the Kelvin wave reaches the equator and the thermocline adjustment slows the EUC.

结合来自Argo和TAO浮标阵列的数据，我们提出了太平洋变化的新观察。Argo剖面揭示了2010年南太平洋通风的高温跃层下层厚度异常的发展。到2017年的数据显示，该异常以斜压波向西和向赤道传播。理论表明，该波将在到达赤道时降低赤道暗流（EUC）的速度，从而将赤道太平洋转变为温暖状态。TAO阵列观测结果支持了这一点，该观测结果显示了2000年前后EUC强度过去十年的变化，以及放射性碳珊瑚的测量结果表明1970年代也发生了类似的变化，这两者均与太平洋年代际变化的相位变化一致。使用在热跃层中具有增强的垂直分辨率的模型模拟，我们确认了亚热带南太平洋热跃层与EUC之间的这种联系，这也体现在东太平洋海表温度上。我们结合这些结果来假设一种机制，可以解释太平洋地区观测到的年代际变化。这种机制依赖于从东南太平洋到赤道太平洋的通风的温跃层结构中异常的传播，从而调节了EUC的强度。赤道太平洋和东南太平洋之间的大气遥相关会周期性地逆转热跃层厚度的异常，从而加剧了这一循环。如果正确的话