Hydrological changes in the African tropics since the Last Glacial Maximum
Hydrological changes in the African tropics since the Last Glacial Maximum
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DOI：
10.1016/s0277-3791(99)00061-x
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发表时间：
2000-01-01
影响因子：
4
通讯作者：
Gasse, F
中科院分区：
文献类型：
--
作者：
Gasse, F
本文回顾了非洲热带和亚热带地区的古水文数据，包括湖泊、地下水和洞穴记录，以显示两个半球的环境和气候是如何相互关联的。虽然轨道引起的季风强度变化占热带非洲长期气候变化的很大一部分，但晚更新世-全新世水文波动似乎是一系列突发事件，反映了轨道强迫、大气、海洋和陆地表面条件之间复杂的相互作用。在末次盛冰期（23-18 ka BP），大多数记录表明，两个半球普遍存在干燥条件，与较低的热带陆地和海洋表面温度有关。这与使用海洋-大气耦合模式的模拟结果一致，该模式预测了热带非洲的降温和夏季降水减少；那时的全球水文循环比今天要弱，当时极地大冰原和海冰的范围是地球气候的一个重要强迫因素。冰期-间冰期气候变化开始较早：约17-16 ka BP的第一个湿润/变暖阶段发生在南极洲气温快速上升的时期。其次，在15-14.5 ka BP和11.5-11 ka BP前后，赤道和北非发生了两次剧烈的干湿转变。两者都被认为与格陵兰岛的主要变暖事件相匹配，并与海洋热盐环流向现代模式的转变相一致。然而，15 ka BP之后的部分气候信号似乎也与南极气候有关。在全新世期间，与高纬度地区的气候变化相比，非洲也经历了剧烈的快速水文波动。特别是在8.4-8 ka和4.2-4 ka BP前后，北方季风域发生了主要的干旱期。与世界其他地区的比较表明，这些事件具有世界性的分布，但有不同的区域表现。在没有大型极地冰盖的情况下，热带大陆水文循环的变化可能对全球气候系统产生重大影响。在这里收集的气候信息可以确定地理和方法上的差距，并提出一些有待解决的科学问题，以便更好地了解热带地区如何对主要气候强迫因子的变化作出反应，以及它们如何影响全球气候。1999爱思唯尔科学有限公司版权所有。
Paleohydrological data from the African tropics and subtropics, including lake, groundwater and speleothem records, are reviewed to show how environments and climates from both hemispheres are inter-related. Although orbitally induced changes in the monsoon strength account for a large part of long-term climatic changes in tropical Africa, the Late Pleistocene-Holocene hydrological fluctuations rather appear to have been a series of abrupt events that reflect complex interactions between, orbital forcing, atmosphere, ocean and land surface conditions. During the Last Glacial Maximum (23-18 ka BP), most records indicate that generally dry conditions have prevailed in both hemispheres, associated with lower tropical land- and sea-surface temperatures. This agrees with simulations using coupled ocean-atmosphere models, which predict cooling and reduced summer precipitation in tropical Africa; the global hydrological cycle was weaker than today when the extent of large polar ice-sheets and sea-ice was a prominent forcing factor of the Earth's climate. Glacial-interglacial climatic changes started early: a first wetting/warming phase at ca. 17-16 ka BP took place during a period of rapid temperature increase in Antarctica. Next, two drastic arid-humid transitions in equatorial and northern Africa occurred around 15-14.5 ka BP and 11.5-11 ka BP. Both are thought to match the major Greenland warming events, in concert with the switching of the oceanic thermohaline circulation to modern mode. However, part of the climatic signal after 15 ka BP also seems related to the Antarctica climate. During the Holocene, Africa has also experienced rapid hydrological fluctuations of dramatic magnitude compared to the climatic changes at high latitudes. In particular, major dry spells occurred around 8.4-8 ka and 4.2-4 ka BP in the northern monsoon domain. Comparison with other parts of the world indicates that these events have a worldwide distribution but different regional expressions. In the absence of large polar ice sheets, changes in the continental hydrological cycles in the tropics may have a significant impact on the global climate system. Climate information gathered here allows to identify geographical and methodological gaps, and raise some scientific questions that remain to be solved to better understand how the tropics respond to changes in major climate-forcing factors, and how they influence climate globally. (C) 1999 Elsevier Science Ltd. All rights reserved.