Contrasting Common Era climate and hydrology sensitivities from paired lake sediment dinosterol hydrogen isotope records in the South Pacific Convergence Zone
Contrasting Common Era climate and hydrology sensitivities from paired lake sediment dinosterol hydrogen isotope records in the South Pacific Convergence Zone
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DOI：
10.1016/j.quascirev.2022.107421
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发表时间：
2022-04
影响因子：
4
通讯作者：
A. Maloney;J. Richey;D. Nelson;Samantha Hing;D. Sear;J. Hassall;P. Langdon;Ursula Sichrowsky;R. Schabetsberger;A. Malau;J. Meyer;I. Croudace;J. Sachs
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作者：
A. Maloney;J. Richey;D. Nelson;Samantha Hing;D. Sear;J. Hassall;P. Langdon;Ursula Sichrowsky;R. Schabetsberger;A. Malau;J. Meyer;I. Croudace;J. Sachs
乌韦亚岛（沃利斯和富图纳群岛）的水文气候受南太平洋辐合带（SPCZ）的降雨控制，SPCZ是南半球最大的降水特征。为了扩展短期观测降水记录，测量了Uvea上两个火山口湖沉积物岩心中藻脂生物标志物甲藻甾醇（δ 2 H甲藻甾醇）的氢同位素组成。现代湖泊在形态和化学上有所不同，但都含有淡水的透光区，支持浮游植物群落，包括产生甲藻甾醇的甲藻，并经历相同的气候条件。δ 2 H地甾醇值跟踪湖水同位素比值，在热带地区最终受降水量和蒸发富集的控制。然而，在88米深的Lac Lalolalo中，δ 2 H地甾醇的沉积值从公元988年左右的−227‰稳步下降到现代的−303‰，这表明该湖泊从活火山环境到现在的系统的演变强烈影响了δ 2 H地甾醇值。虽然目前的水文和水的同位素系统学现在可能反映在这个湖的降水和蒸发，这些过程之间的相互作用和盆地形态，地球化学和水文大的变化阻碍了从Lac Lalolalo的沉积δ 2 Hdinosterol记录的气候信号的恢复。这项工作强调了站点复制和使用补充气候重建工具的重要性，特别是当使用可能对一个以上的环境参数敏感的分子代理时。与它的邻居相反，23米深的拉努塔瓦克湖的重复δ 2氢甾醇记录在−277‰和−297‰之间变化，表明在中世纪气候异常（MCA，950-1250 CE）时期的条件稍微干燥。与Upolu（萨摩亚）和Efate（瓦努阿图）公布的记录相比，Lac Lanutavake中的δ 2 H二甾醇信号减弱，表明Uvea的位置对距离SPCZ中心轴较远的站点的降水变化不敏感。成岩径流代理与δ 2 Hdinosterol相结合，支持对Uvea、Upolu和Efate相对干燥MCA的解释，这可能是由于降水强度较低、收缩或更具区域性的SPCZ。
Hydroclimate on ‘Uvea (Wallis et Futuna) is controlled by rainfall associated with the South Pacific Convergence Zone (SPCZ), the southern hemisphere's largest precipitation feature. To extend the short observational precipitation record, the hydrogen isotopic composition of the algal lipid biomarker dinosterol (δ2Hdinosterol) was measured in sediment cores from two volcanic crater lakes on ‘Uvea. The modern lakes differ morphologically and chemically but both contain freshwater within the photic zone, support phytoplankton communities inclusive of dinosterol-producing dinoflagellates, and experience identical climate conditions. δ2Hdinosterolvalues track lake water isotope ratios, ultimately controlled in the tropics by precipitation amount and evaporative enrichment. However, in 88-m-deep Lac Lalolalo a steadily decreasing trend in sedimentary δ2Hdinosterolvalues from −227‰ around year 988 CE to modern values as low as −303‰, suggests this lake's evolution from an active volcanic setting to the present system strongly influenced δ2Hdinosterolvalues. Although current hydrology and water isotope systematics may now reflect precipitation and evaporation in this lake, the interaction between these processes and large changes in basin morphology, geochemistry, and hydrology obstruct the recovery of a climate signal from Lac Lalolalo's sedimentary δ2Hdinosterolrecords. This work emphasizes the importance of site replication and the use of complementary climate reconstruction tools, especially when using molecular proxies that may be sensitive to more than one environmental parameter. Contrary to its neighbor, duplicate δ2Hdinosterolrecords from 23-m-deep Lac Lanutavake varied between −277‰ and −297‰ and indicate slightly drier conditions during the time-period known as the Medieval Climate Anomaly (MCA, 950–1250 CE). The δ2Hdinosterolsignal in Lac Lanutavake was muted compared to published records from ‘Upolu (Samoa) and Efate (Vanuatu) indicating that ‘Uvea's location is not as sensitive to precipitation variability at sites farther from the SPCZ central axis. Lithogenic runoff proxies combined with δ2Hdinosterolsupport the interpretation of a relatively dry MCA on ‘Uvea, ‘Upolu, and Efate, potentially due to less intense precipitation, a contracted, or a more zonally oriented SPCZ.