Two annual cycles of the Pacific cold tongue under orbital precession
Two annual cycles of the Pacific cold tongue under orbital precession
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DOI：
10.1038/s41586-022-05240-9
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发表时间：
2022-11
期刊：
影响因子：
64.8
通讯作者：
J. Chiang;A. Atwood;D. Vimont;Paul A Nicknish;W. Roberts;C. Tabor;A. Broccoli
中科院分区：
文献类型：
--
作者：
J. Chiang;A. Atwood;D. Vimont;Paul A Nicknish;W. Roberts;C. Tabor;A. Broccoli
太平洋冷舌海表温度的年周期被认为是由地球的轴向倾斜，-（倾斜效应）驱动的，因此它的相位相对于日历应该是固定的。然而，在几个地球系统模型中，它的相位和振幅在不同的轨道岁差配置下变化剧烈且一致。在这里，我们表明，冷舌具有另一个年周期驱动的地球-太阳距离的变化（距离效应）从轨道偏心率。由于这两个周期具有略微不同的周期性，它们的干扰导致了岁差周期内净季节性的复杂演变。距离效应的振幅随偏心率线性增加，并且与过去百万年中最大偏心率值（约为0.05）的倾斜效应的振幅相当。机械上，冷舌上的距离效应是通过季节性的纵向移动的步行者环流和随后的年度风强迫热带太平洋动力海洋-大气系统。这一发现要求重新评估目前对太平洋冷舌年周期的理解，并重新评估热带太平洋古气候记录的年周期阶段变化。
The Pacific cold tongue annual cycle in sea surface temperature is presumed to be driven by Earth’s axial tilt, , , –(tilt effect), and thus its phasing should be fixed relative to the calendar. However, its phase and amplitude change dramatically and consistently under various configurations of orbital precession in several Earth System models. Here, we show that the cold tongue possesses another annual cycle driven by the variation in Earth–Sun distance (distance effect) from orbital eccentricity. As the two cycles possess slightly different periodicities, their interference results in a complex evolution of the net seasonality over a precession cycle. The amplitude from the distance effect increases linearly with eccentricity and is comparable to the amplitude from the tilt effect for the largest eccentricity values over the last million years (evalue approximately 0.05). Mechanistically, the distance effect on the cold tongue arises through a seasonal longitudinal shift in the Walker circulation and subsequent annual wind forcing on the tropical Pacific dynamic ocean–atmosphere system. The finding calls for reassessment of current understanding of the Pacific cold tongue annual cycle and re-evaluation of tropical Pacific palaeoclimate records for annual cycle phase changes.