Continuous 1.3-million-year record of East African hydroclimate, and implications for patterns of evolution and biodiversity
Continuous 1.3-million-year record of East African hydroclimate, and implications for patterns of evolution and biodiversity
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DOI：
10.1073/pnas.1512864112
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发表时间：
2015-12-22
影响因子：
11.1
通讯作者：
Blome, Margaret W.
中科院分区：
文献类型：
--
作者：
Lyons, Robert P.;Scholz, Christopher A.;Blome, Margaret W.
热带地区的水分输送对全球能量收支是一个关键过程，并且在地质时间尺度上，显著影响了大陆地貌、迁徙路径和生物进化。在此，我们展示了一份独一无二的、连续的130万年的大陆水气候和湖面变化记录，该记录来自东非马拉维湖（南纬9 - 15度）的钻孔岩芯数据。在第四纪期间，我们观察到有效水分发生了巨大变化，导致世界上最大的湖泊之一以及最多样化的淡水生态系统发生了大规模变化。结果显示，在晚第四纪期间有24次湖面下降超过200米的证据，包括15次低水位期，当时水位比现代低400多米。在中更新世转型期（MPT）观察到一个显著变化，这与远场气候强迫一致，它将大约80万年前前后差异巨大的水气候状况区分开来。在80万年前之前，湖面较低，表明气候比现在干燥，且水位变化频繁。在中更新世转型期之后，高振幅的湖面变化主导了记录。从80万年前到10万年前，一个深邃且常常漫溢的湖泊占据了盆地，表明气候较为湿润，但这些高水位期被长时间的极端干旱所打断。在高偏心率时期观察到高湖面水位期。极端的水气候变异性对马拉维湖特有的丽鱼科鱼类种群产生了深远影响；地理上广泛的栖息地重构提供了新的生态机遇，使新的种群能够迅速分化为不同的物种。
The transport of moisture in the tropics is a critical process for the global energy budget and on geologic timescales, has markedly influenced continental landscapes, migratory pathways, and biological evolution. Here we present a continuous, first-of-its-kind 1.3-My record of continental hydroclimate and lake-level variability derived from drill core data from Lake Malawi, East Africa (9-15 degrees S). Over the Quaternary, we observe dramatic shifts in effective moisture, resulting in large-scale changes in one of the world's largest lakes and most diverse freshwater ecosystems. Results show evidence for 24 lake level drops of more than 200 m during the Late Quaternary, including 15 lowstands when water levels were more than 400 m lower than modern. A dramatic shift is observed at the Mid-Pleistocene Transition (MPT), consistent with far-field climate forcing, which separates vastly different hydroclimate regimes before and after similar to 800,000 years ago. Before 800 ka, lake levels were lower, indicating a climate drier than today, and water levels changed frequently. Following the MPT high-amplitude lake level variations dominate the record. From 800 to 100 ka, a deep, often overfilled lake occupied the basin, indicating a wetter climate, but these highstands were interrupted by prolonged intervals of extreme drought. Periods of high lake level are observed during times of high eccentricity. The extreme hydroclimate variability exerted a profound influence on the Lake Malawi endemic cichlid fish species flock; the geographically extensive habitat reconfiguration provided novel ecological opportunities, enabling new populations to differentiate rapidly to distinct species.