Permanent El Niño during the Pliocene warm period not supported by coral evidence
Permanent El Niño during the Pliocene warm period not supported by coral evidence
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DOI：
10.1038/nature09777
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发表时间：
2011-03
期刊：
影响因子：
64.8
通讯作者：
Tsuyoshi Watanabe;A. Suzuki;S. Minobe;Tatsunori Kawashima;K. Kameo;K. Minoshima;Y. M. Aguilar;Ryoji Wani;H. Kawahata;K. Sowa;T. Nagai;T. Kase
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文献类型：
--
作者：
Tsuyoshi Watanabe;A. Suzuki;S. Minobe;Tatsunori Kawashima;K. Kameo;K. Minoshima;Y. M. Aguilar;Ryoji Wani;H. Kawahata;K. Sowa;T. Nagai;T. Kase
上新世暖期(PWP；300-500万年前)的厄尔尼诺/南方涛动(ENSO)系统可能以一种永久的厄尔尼诺状态存在，赤道太平洋的纬向海表温度(SST)梯度急剧降低。这表明，在PWP期间，当全球平均气温和大气二氧化碳浓度与预测的近期气候变化相似时，ENSO变异性--以及相关的全球气候遥相关--可能与今天截然不同。然而，由于缺乏关于关键低纬地区SST季节和年际变化的观测证据，PWP的这一基本气候特征仍然存在争议。我们在这里表明，在压水堆期间不存在永久性的厄尔尼诺现象。我们对δ18O海温和盐度指标的频谱分析，提取自菲律宾两个35年的月分辨率PWPPoritGuard，揭示了类似于目前ENSO变化的变化。尽管我们的化石珊瑚不能直接与现代ENSO记录进行比较，但有两条证据表明，菲律宾珊瑚是合适的ENSO替代品。首先，来自附近活体护航的δ18O异常与现代记录的ENSO变率相关。第二，化石珊瑚中的负δ18O事件与厄尔尼诺事件期间活珊瑚中δ18O的下降非常相似。先前提倡永久厄尔尼诺状态的研究可能受到许多SST代理的粗略分辨率的限制，而我们基于珊瑚的分析确定了坚定地解决ENSO结构所需的时间尺度上的气候变异性。
The El Niño/Southern Oscillation (ENSO) system during the Pliocene warm period (PWP; 3–5 million years ago) may have existed in a permanent El Niño state with a sharply reduced zonal sea surface temperature (SST) gradient in the equatorial Pacific Ocean. This suggests that during the PWP, when global mean temperatures and atmospheric carbon dioxide concentrations were similar to those projected for near-term climate change, ENSO variability—and related global climate teleconnections—could have been radically different from that today. Yet, owing to a lack of observational evidence on seasonal and interannual SST variability from crucial low-latitude sites, this fundamental climate characteristic of the PWP remains controversial,,,,,,,,. Here we show that permanent El Niño conditions did not exist during the PWP. Our spectral analysis of the δ18O SST and salinity proxy, extracted from two 35-year, monthly resolved PWPPoritescorals in the Philippines, reveals variability that is similar to present ENSO variation. Although our fossil corals cannot be directly compared with modern ENSO records, two lines of evidence suggest that Philippine corals are appropriate ENSO proxies. First, δ18O anomalies from a nearby livePoritescoral are correlated with modern records of ENSO variability. Second, negative-δ18O events in the fossil corals closely resemble the decreases in δ18O seen in the live coral during El Niño events. Prior research advocating a permanent El Niño state may have been limited by the coarse resolution of many SST proxies, whereas our coral-based analysis identifies climate variability at the temporal scale required to resolve ENSO structure firmly.