Long-term hydroclimate variability at low latitudes exerts a strong influence on global climate, yet its timing and mechanisms are poorly documented for the central Pacific region. Here we present the molecular and hydrogen isotopic compositions of long-chain n-alkanes in a montane wetland deposit at Mount Kaʻala on the Island of Oʻahu, Hawaiʻi, which document hydrological conditions and related vegetation changes over the late Pleistocene and the Holocene. To aid the interpretation of fossil n-alkanes, we also determine chain-length distributions of the most common bog plants growing locally. Organic matter accumulation started around 45 ka BP, one of the oldest reported dates for peat-forming wetland ecosystems in Hawaiʻi. Sedimentary n-alkane distributions suggest vegetation shifts driven by changes in rainfall regime, especially with enhanced abundances of shorter chain length homologues during wet periods. Depleted values of n-alkane δ²H dated to ca 45–40, 24–22.5, 19–16.5, and 10–6 ka BP generally coincide with faster carbon accumulation rates, and may indicate enhanced winter cyclonic storm precipitation, as suggested by modern rainwater isotope data. For the Late Pleistocene, the consistency in timing and direction of hydroclimate variability at Kaʻala, dynamics of the Mauna Kea ice cap, precipitation in the Cariaco basin, and East Asian monsoon intensity suggest that southward shifts in the mean position of the ITCZ contributed to a greater frequency of extratropical cyclonic storms, increasing precipitation at leeward and high-elevation sites. During the Holocene, the ITCZ-hydroclimate linkage at Kaʻala is inverted, consistent with a Pacific dominated by ENSO variability.

低纬度地区的长期水文气候变化对全球气候影响很大，但太平洋中部地区的时间和机制却鲜有记载。在这里，我们介绍了夏威夷瓦胡岛卡阿拉山的山地湿地沉积物中长链正构烷烃的分子和氢同位素组成，这些文献记录了晚更新世和全新世的水文条件和相关的植被变化。为了帮助解释化石正构烷烃，我们还确定了本地生长的最常见沼泽植物的链长分布。有机质积累始于约45 ka BP，这是夏威夷形成泥炭的湿地生态系统最古老的报道日期之一。沉积ñ烷烃的分布表明，降雨条件的变化驱动了植被的转移，特别是在潮湿时期，较短链长的同系物的丰度提高了。的贫化值Ñ烷烃δ ²如现代雨水同位素数据所示，H值大约为45–40、24–22.5、19–16.5和10–6 ka BP，通常与更快的碳积累速率相吻合，并且可能表明冬季气旋风暴降水增加。对于晚更新世而言，Kaʻala的水文气候变化的时间和方向，Mauna Kea冰帽的动力学，Cariaco盆地的降水以及东亚季风强度的一致性表明，ITCZ的平均位置向南偏移有助于温带气旋风暴的频率增加，背风和高海拔站点的降水增加。全新世期间，Kaala的ITCZ-水气候链接被反转，这与ENSO变异主导的太平洋一致。