Simulated range of mid-Holocene precipitation changes to extended lakes and wetlands over North Africa
Simulated range of mid-Holocene precipitation changes to extended lakes and wetlands over North Africa
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北非广大湖泊和湿地的全新世中期降水变化模拟范围
DOI：
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发表时间：
2021
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通讯作者：
T. Kleinen
中科院分区：
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作者：
N. Specht;M. Claussen;T. Kleinen
抽象的。大约6000年前，在全新世中期，北非夏季日照的增强导致了季风降水的增加，并导致了今天撒哈拉沙漠湖泊和湿地的广泛扩张。湖泊和湿地的这种扩张在古环境沉积物记录中有记载，但空间上稀疏且往往不连续的沉积物记录只能提供一幅零碎的画面。以前的模拟研究规定，无论是一个小湖泊和湿地范围内的重建或集中在记录的大型湖泊只调查其对全新世中期气候的影响。与这些研究相反，我们研究了中全新世降水变化对小湖泊范围和潜在最大湖泊和湿地范围的可能范围，结果表明，最大湖泊和湿地范围使北非雨带比小湖泊范围向北移动约3 °。植被湿地比同样大的湖泊由于其高表面粗糙度导致更大的降水增加。水分收支分析表明，无论是湖泊和湿地，导致增强内陆水分输送和当地的水分循环到他们的南侧。相比之下，增加的水分平流的哈麦丹风导致北部的湖泊和湿地干燥的反应。这些结果表明，纬度的湖泊和湿地的位置影响了非洲夏季风的北伸。在敏感性实验中，西撒哈拉湖泊和湿地的北方位置大大有助于在最大湖泊和湿地模拟中看到的强烈季风北移。
Abstract. Enhanced summer insolation over North Africa induced a monsoon precipitation increase during the mid-Holocene, about 6000 years ago, and led to a widespread expansion of lakes and wetlands in the present-day Sahara. This expansion of lakes and wetlands is documented in paleoenvironmental sediment records, but the spatially sparse and often discontinuous sediment records provide only a fragmentary picture. Former simulation studies prescribed either a small lake and wetland extent from reconstructions or focused on documented mega-lakes only to investigate their effect on the mid-Holocene climate. In contrast to these studies, we investigate the possible range of mid-Holocene precipitation changes in response to a small lake extent and a potential maximum lake and wetland extent. Results show that the maximum lake and wetland extent shift the North African rain belt about 3 ° farther northward than the small lake extent. Vegetated wetlands cause a larger precipitation increase than the equally-large lakes due to their high surface roughness. A moisture budget analysis reveals that both, lakes and wetlands, cause an enhanced inland moisture transport and local moisture recycling to their southern side. In contrast, increased moisture advection by the Harmattan winds causes a drying response to the north of the lakes and wetlands. These results indicate that the latitudinal position of the lakes and wetlands influences the northward extension of the African summer monsoon. In the sensitivity experiments, the northern position of West Saharan lakes and wetlands substantially contributes to the strong monsoon northward shift seen in the maximum lake and wetland simulations.