Evaluating the potential of early Pliocene mollusc shells from Peru as El Nino records - permanent "El-Nino-like" state or interannual El Nino variability

厄尔尼诺Niño-Southern涛动（ENSO）与未来长期全球变暖之间的相互作用是不确定的。一些模型将过去和未来的温室气候与东太平洋温跃层的变浅以及东太平洋向永久“厄尔尼诺”状态的转变联系起来。这与其他表明ENSO系统在“温室”条件下变化不大的模型形成鲜明对比。上新世早期以全球变暖时间延长为特征，为这些相互矛盾的理论提供了一个很好的试验场。由于ENSO事件与年周期紧密耦合，因此必须使用具有季节分辨率的古气候档案来解决单个ENSO事件。软体动物壳的稳定氧同位素可以提供上新世早期ENSO事件的第一个代用记录。我们将评估不同软体动物物种的潜力，从几个上新世暴露在秘鲁沿海，作为气候档案。一系列的分析方法（扫描电子显微镜，x射线衍射，阴极发光）将被应用于开发一个筛选程序的成岩修饰。将选择未成岩改变的软体动物壳进行季节温度变化的稳定同位素分析。

The interaction between the El Niño-Southern Oscillation (ENSO) and long-term future global warming is uncertain. Some models link past and future ¿hothouse¿ climates to a shallowing of the east Pacific thermocline and a shift towards a permanent ¿El Nino-like state¿ in the east Pacific. This is in contrast to other models indicating little change in the ENSO system under ¿hothouse¿ conditions. The early Pliocene, characterized by prolonged global warmth, provides a good testing ground for these conflictive theories. Since ENSO events are tightly coupled to the annual cycle it is essential to use paleoclimate-archives with seasonal resolution to resolve individual ENSO events. The stable oxygen isotopes of mollusc shells could provide the first proxy-record for ENSO events during the early Pliocene. We will evaluate the potential of different mollusc species, from several Pliocene exposures in coastal Peru, as climate archives. A range of analytical methods (scanning electron microscopy, X-ray diffraction, cathodoluminescence) will be applied to develop a screening procedure for diagenetic modifications. Diagenetically unaltered mollusc shells will be selected for stable isotope analysis of seasonal temperature variability.