Abstract Constraining past variability in ocean conditions in the Western Pacific Warm Pool (WPWP) and examining how it has been influenced by the El-Nino Southern Oscillation (ENSO) is critical to predicting how these systems may change in the future. To characterize the spatiotemporal variability of the WPWP and ENSO during the past three decades, we analyzed climate proxies using coral cores sampled from Porites spp. from Kosrae Island (KOS) and Woleai Atoll (WOL) in the Federated States of Micronesia. Coral skeleton samples drilled along the major growth axis were analyzed for oxygen isotopes (δ18Oc) and trace element ratios (Sr/Ca), used to reconstruct sea surface salinity and temperature (SSS and SST). Pseudocoral δ18O time series (δ18Opseudo) were calculated from gridded instrumental observations and compared to δ18Oc, followed by fine-tuning using coral Sr/Ca and gridded SST, to produce age models for each coral. The thermal component of δ18Oc was removed using Sr/Ca for SST, to derive δ18O of seawater (δ18Osw), a proxy for SSS. The Sr/Ca, and δ18Osw records were compared to instrumental SST and SSS to test their fidelity as regional climate recorders. We found both sites display significant Sr/Ca-SST calibrations at monthly and interannual (dry season, wet season, mean annual) timescales. At each site, δ18Osw also exhibited significant calibrations to SSS across the same timescales. The difference between normalized dry season SST (Sr/Ca) anomalies from KOS and WOL generates a zonal SST gradient (KOSWOLSST), capturing the east-west WPWP migration observed during ENSO events. Similarly, the average of normalized dry season δ18Osw anomalies from both sites produces an SSS index (KOSWOLSSS) reflecting the regional hydrological changes. Both proxy indices, KOSWOLSST and KOSWOLSSS, are significantly correlated to regional ENSO indices. These calibration results highlight the potential for extending the climate record, revealing spatial hydrological gradients within the WPWP and ENSO variability back to the end of the Little Ice Age.

中文翻译：

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基于珊瑚的代理校准限制了西太平洋暖池中 ENSO 驱动的海面温度和盐度梯度

摘要 限制西太平洋暖池 (WPWP) 过去海洋条件的变化并研究它如何受到厄尔尼诺南方涛动 (ENSO) 的影响，对于预测这些系统在未来可能如何变化至关重要。为了描述过去 30 年中 WPWP 和 ENSO 的时空变异性，我们使用从 Porites spp 采样的珊瑚核分析了气候代理。来自密克罗尼西亚联邦的科斯雷岛 (KOS) 和沃莱艾环礁 (WOL)。对沿主要生长轴钻孔的珊瑚骨架样品进行氧同位素 (δ18Oc) 和微量元素比 (Sr/Ca) 分析，用于重建海面盐度和温度（SSS 和 SST）。伪光 δ18O 时间序列 (δ18Opseudo) 由网格仪器观测计算得出，并与 δ18Oc 进行比较，然后使用珊瑚 Sr/Ca 和网格 SST 进行微调，以生成每个珊瑚的年龄模型。对于 SST，使用 Sr/Ca 去除 δ18Oc 的热成分，以推导出海水的 δ18O (δ18Osw)，这是 SSS 的代表。将 Sr/Ca 和 δ18Osw 记录与仪器 SST 和 SSS 进行比较，以测试它们作为区域气候记录器的保真度。我们发现两个站点在月度和年际（旱季、雨季、年平均）时间尺度上都显示出显着的 Sr/Ca-SST 校准。在每个站点，δ18Osw 在相同的时间尺度上也表现出对 SSS 的显着校准。来自 KOS 和 WOL 的标准化旱季 SST (Sr/Ca) 异常之间的差异产生了纬向 SST 梯度 (KOSWOLSST)，捕获了在 ENSO 事件期间观察到的东西向 WPWP 迁移。相似地，来自两个站点的标准化旱季 δ18Osw 异常的平均值产生反映区域水文变化的 SSS 指数 (KOSWOLSSS)。KOSWOLSST 和 KOSWOLSSS 这两个代理指数都与区域 ENSO 指数显着相关。这些校准结果突出了扩展气候记录的潜力，揭示了 WPWP 内的空间水文梯度和 ENSO 变率回到小冰河时代末期。