Earth Observatory of Singapore, Nanyang Technological University, 639798 Singapore.
Asian School of the Environment, Nanyang Technological University, 639798 Singapore.
Nature. 2017 Jan 11;541(7636):204-207. doi: 10.1038/nature20787.
Reconstructing the history of tropical hydroclimates has been difficult, particularly for the Amazon basin-one of Earth's major centres of deep atmospheric convection. For example, whether the Amazon basin was substantially drier or remained wet during glacial times has been controversial, largely because most study sites have been located on the periphery of the basin, and because interpretations can be complicated by sediment preservation, uncertainties in chronology, and topographical setting. Here we show that rainfall in the basin responds closely to changes in glacial boundary conditions in terms of temperature and atmospheric concentrations of carbon dioxide. Our results are based on a decadally resolved, uranium/thorium-dated, oxygen isotopic record for much of the past 45,000 years, obtained using speleothems from Paraíso Cave in eastern Amazonia; we interpret the record as being broadly related to precipitation. Relative to modern levels, precipitation in the region was about 58% during the Last Glacial Maximum (around 21,000 years ago) and 142% during the mid-Holocene epoch (about 6,000 years ago). We find that, as compared with cave records from the western edge of the lowlands, the Amazon was widely drier during the last glacial period, with much less recycling of water and probably reduced plant transpiration, although the rainforest persisted throughout this time.
重建热带水文气候的历史一直很困难，特别是对亚马逊盆地——地球主要的深层大气对流中心之一。例如，在冰川时期，亚马逊盆地是否明显更干燥或保持湿润一直存在争议，主要原因是大多数研究地点都位于盆地的边缘，而且由于沉积物的保存、年代测定的不确定性和地形设置，解释可能会变得复杂。在这里，我们表明，根据温度和大气二氧化碳浓度的冰川边界条件的变化，盆地的降雨量会密切响应。我们的研究结果基于过去 45000 年中，来自亚马逊东部帕拉伊索洞穴的钟乳石获得的一个分辨率为十年、铀/钍定年、氧同位素记录；我们将该记录解释为与降水有广泛的关系。与现代水平相比，该地区的降水量在末次冰盛期（约 21000 年前）时约为 58%，在全新世中期（约 6000 年前）时约为 142%。我们发现，与低地西部洞穴记录相比，在末次冰期，亚马逊地区普遍更干燥，水的再循环较少，植物蒸腾作用可能减少，尽管雨林在整个时期都存在。
