Links between tropical Pacific seasonal, interannual and orbital variability during the Holocene
Links between tropical Pacific seasonal, interannual and orbital variability during the Holocene
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DOI：
10.1038/ngeo2608
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发表时间：
2016-02-01
影响因子：
18.3
通讯作者：
Tudhope, A.
中科院分区：
文献类型：
--
作者：
Emile-Geay, J.;Cobb, K. M.;Tudhope, A.
厄尔尼诺/南方涛动(ENSO)是气候年际变化的主要模式。然而，目前还不清楚ENSO如何对外部强迫做出反应，特别是在全新世期间由轨道引起的季节性周期幅度的变化。在这里，我们提出了一个热带太平洋的季节和年际表面条件的重建网络的高分辨率珊瑚和软体动物记录，跨越离散的时间间隔的全新世。我们在2年到7年的ENSO波段中发现了几个与赤道太阳活动的轨道变化不同的减小方差的间隔，在5000年到3000年之前，的减少是显著的。我们将重建的ENSO方差和季节周期与包括轨道强迫的9个气候模式模拟的结果进行了比较，发现这些模式没有捕捉到ENSO变化的时间或幅度，也没有观测到中全新世季节性的增加，而且在我们的重建中没有发现季节周期的幅度与与ENSO相关的海表面温度变化之间的模拟逆关系。我们的结论是，热带太平洋气候是高度多变的，并受到千年尺度静止期的影响。这些周期与轨道强迫没有简单的联系，而且不能被当前一代模型充分模拟。
The El Nino/Southern Oscillation (ENSO) is the leading mode of interannual climate variability. However, it is unclear how ENSO has responded to external forcing, particularly orbitally induced changes in the amplitude of the seasonal cycle during the Holocene. Here we present a reconstruction of seasonal and interannual surface conditions in the tropical Pacific Ocean from a network of high-resolution coral and mollusc records that span discrete intervals of the Holocene. We identify several intervals of reduced variance in the 2 to 7 yr ENSO band that are not in phase with orbital changes in equatorial insolation, with a notable 64% reduction between 5,000 and 3,000 years ago. We compare the reconstructed ENSO variance and seasonal cycle with that simulated by nine climate models that include orbital forcing, and find that the models do not capture the timing or amplitude of ENSO variability, nor the mid-Holocene increase in seasonality seen in the observations; moreover, a simulated inverse relationship between the amplitude of the seasonal cycle and ENSO-related variance in sea surface temperatures is not found in our reconstructions. We conclude that the tropical Pacific climate is highly variable and subject to millennial scale quiescent periods. These periods harbour no simple link to orbital forcing, and are not adequately simulated by the current generation of models.