Hydrogen isotope ratios (²H/¹H or δ²H) were measured in lipid biomarkers from algal, plant and microbial sources in sediment cores from a lake and a peat bog on the small, sparsely-inhabited Washington Island (4°43′N, 160°25′W) to assess central equatorial Pacific hydroclimate conditions during the last millennium. High δ²H values in lipids from a variety of biological sources indicate that the driest period of the last millennium occurred ∼1450–1600 CE, during the first half of the Little Ice Age (LIA; 1450–1850 CE). An Intertropical Convergence Zone (ITCZ) located south of its modern position, less frequent and/or weaker El Niño events, and/or a La Niña-like mean state in the tropical Pacific are potential causes for this drying at Washington Island. From ∼1600 to 1650 CE, an abrupt transition to modern-like low δ²H values in phytoplankton, plant, and microbial lipids occurred, signaling the establishment of a high-rainfall regime similar to that observed today. This transition coincided with increased ENSO variability, an excess of central-Pacific relative to eastern-Pacific El Niños, and a decline in the zonal SST gradient across the tropical Pacific, reflecting an El Niño-like mean state. The Medieval Warm Period (MWP; 900–1250 CE) was characterized by high δ²H values in lipids from phytoplankton (dinosterol, dinostanol), bacteria (hop-21-ene), and vascular plants (sitostanol), and by extension a drier climate relative to the modern lake. An increasing δ²H trend through the MWP in lipids from all sources implies drying as Northern Hemisphere temperatures declined from the early to the late MWP. This drying is hypothesized to have been driven by extensive volcanism in northern, southern, and tropical latitudes, all of which tend to cause zonal mean drying at the latitude of WI (5°N). Finally, the transition period between the LIA and MWP ∼1250–1450 CE was characterized by declining δ²H values of plant and microbial lipids in peat sediments, indicating a trend toward wetter conditions; in the absence of known internal or external climate forcings, this may have been a regional or local event. This study demonstrates that the application of compound-specific δ²H measurements of lipids from multiple biological sources and in multiple sedimentary archives from a single location can yield hydroclimate reconstructions with higher confidence than those based on single lipids. Such reconstructions are particularly important in the vast tropical Pacific, where few hydroclimate records exist.

氢同位素比（² H / ¹ H或δ ² H）在从藻类，植物和来自湖沉积物核微生物来源并在很小，稀疏居住华盛顿岛（4°43'一泥炭沼泽脂质的生物标志物测定N，160°25′W）以评估上个千年中赤道太平洋中部的气候条件。高的△ ²来自各种生物来源的脂质中的H值表明，在小冰河时代的前半段（LIA； 1450-1850 CE），最近一个千年的最干旱时期发生在1450–1600 CE。位于现代位置以南的热带气旋收敛区（ITCZ），较少发生的厄尔尼诺事件和/或较弱的厄尔尼诺事件，和/或热带太平洋地区的类似拉尼娜现象的平均状态，可能是导致华盛顿岛干旱的原因。从~1600 1650 CE，突然过渡到现代，如低δ ²浮游植物，植物和微生物脂质中的H值出现，表明建立了类似于今天观察到的高降雨制度。这一转变与ENSO变异性增加，中太平洋相对于东太平洋厄尔尼诺现象的过量以及热带太平洋整个太平洋纬向SST梯度的下降相吻合，反映出类似厄尔尼诺现象的平均状态。中世纪暖期（MWP; 900-1250 CE）的特点是高δ ²在脂质ħ值从浮游植物（dinosterol，dinostanol），细菌（跳-21烯），和维管植物（谷甾烷醇），以及由扩展相对于现代湖泊而言，气候更干燥。越来越δ ²来自所有来源的脂质中MWP的H趋势表明，随着北半球温度从MWP的早期到晚期下降，干燥。据推测，这种干燥是由北部，南部和热带纬度地区广泛的火山活动驱动的，所有这些都倾向于引起威斯康星州纬度（5°N）的纬向平均干燥。最后，LIA和MWP ~1250-1450 CE之间的过渡时期的特点是下降δ ^2个植物和微生物的脂质在泥炭沉积物h的值，表明朝向湿润条件的趋势; 在没有已知内部或外部气候强迫的情况下，这可能是区域性事件或地方性事件。这项研究表明，复合具体的应用δ ²比起基于单一脂质的脂类，对来自多个生物来源和多个沉积物档案中单个部位的脂质进行的H值测量可以产生更高的可信度的水文气候重建。这种重建在广阔的热带太平洋上尤其重要，那里几乎没有水文气候记录。