Subtropical modulation of the equatorial undercurrent: a mechanism of Pacific variability
Subtropical modulation of the equatorial undercurrent: a mechanism of Pacific variability
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赤道暗流的副热带调制：太平洋变率的机制
DOI：
10.1007/s00382-020-05568-w
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发表时间：
2021
期刊：
影响因子：
4.6
通讯作者：
D. Schrag
中科院分区：
文献类型：
--
作者：
L. Kuntz;D. Schrag
结合Argo和TAO浮标阵列的数据，我们提出了太平洋变化的新观测结果。Argo剖面揭示了2010年南太平洋通风性温跃层下层厚度异常的发育。2017年的数据显示，这种异常以斜压波的形式向西向赤道传播。理论认为，当赤道暗流到达赤道时，这一波将降低其速度，使赤道太平洋变成温暖的状态。这一观点得到了TAO阵列观测结果的支持，这些观测结果表明，在2000年前后，EUC强度发生了年代际变化，而放射性碳珊瑚测量结果表明，在20世纪70年代也发生了类似的变化，两者都与太平洋年代际变率的阶段变化相一致。通过在温跃层中增强垂直分辨率的模式模拟，我们证实了副热带南太平洋温跃层与EUC之间的联系，这种联系也体现在东太平洋海面温度上。我们将这些结果结合起来，假设一种机制可以解释在太平洋观测到的一些年代际变化。这种机制依赖于从东南太平洋到赤道太平洋的通风性温跃层结构中的异常传播，从而调节EUC的强度。赤道太平洋和东南太平洋之间的大气遥相关周期性地逆转了温跃层厚度的异常，从而增强了这个循环。如果正确，我们的假设预测，当开尔文波到达赤道，温跃层调整减缓EUC时，赤道太平洋将恢复到温暖状态。
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.