Assessing El Nino Southern Oscillation variability during the past millennium
Assessing El Nino Southern Oscillation variability during the past millennium
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DOI：
10.1029/2011pa002139
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发表时间：
2011-09-15
期刊：
影响因子：
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通讯作者：
Hammond, D. E.
中科院分区：
文献类型：
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作者：
Khider, D.;Stott, L. D.;Hammond, D. E.
我们重建了跨越中世纪气候异常（MCA，公元 800-1300 年）和小冰河时期（LIA，公元 1500-1850 年）的厄尔尼诺南方涛动 (ENSO) 变化。 ENSO 的变化是通过比较温跃层浮游有孔虫 Pulleniatina obliquiloculata 个体样本的 Delta O-18 值的分布和对称性来估计的，这些样本是从西热带太平洋暖池边缘的苏拉威西海沉积物岩心的离散时间范围中提取的。各个 delta O-18 值的分布被解释为 ENSO 两个阶段强度的度量，而 delta O-18 分布的对称性用于评估 El Ni o 和 La Ni a 事件的相对强度/频率。与之前的研究相比，我们使用稳健且具有抵抗力的统计数据来量化 delta O-18 分布的扩散和对称性；这种方法的动机是样本量相对较小且存在异常值。此外，我们使用伪代理方法来研究不同古环境因素对 Delta O-18 分布统计的影响，这可能会使古 ENSO 重建产生偏差。我们发现北半球 MCA 或 LIA 期间 ENSO 的震级/强度没有系统性差异。然而，我们的结果表明，MCA 期间的 ENSO 偏向于比 El Ni o 更强/更频繁的 La Ni a，这一观察结果与北美西部地区记录的中世纪特大干旱一致。
We present a reconstruction of El Nino Southern Oscillation (ENSO) variability spanning the Medieval Climate Anomaly (MCA, A. D. 800-1300) and the Little Ice Age (LIA, A. D. 1500-1850). Changes in ENSO are estimated by comparing the spread and symmetry of delta O-18 values of individual specimens of the thermocline-dwelling planktonic foraminifer Pulleniatina obliquiloculata extracted from discrete time horizons of a sediment core collected in the Sulawesi Sea, at the edge of the western tropical Pacific warm pool. The spread of individual delta O-18 values is interpreted to be a measure of the strength of both phases of ENSO while the symmetry of the delta O-18 distributions is used to evaluate the relative strength/ frequency of El Ni o and La Ni a events. In contrast to previous studies, we use robust and resistant statistics to quantify the spread and symmetry of the delta O-18 distributions; an approach motivated by the relatively small sample size and the presence of outliers. Furthermore, we use a pseudo-proxy approach to investigate the effects of the different paleo-environmental factors on the statistics of the delta O-18 distributions, which could bias the paleo-ENSO reconstruction. We find no systematic difference in the magnitude/strength of ENSO during the Northern Hemisphere MCA or LIA. However, our results suggest that ENSO during the MCA was skewed toward stronger/more frequent La Ni a than El Ni o, an observation consistent with the medieval megadroughts documented from sites in western North America.