The sensitivity of East African rift lakes to climate fluctuations
The sensitivity of East African rift lakes to climate fluctuations
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DOI：
10.1007/s10933-010-9442-4
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发表时间：
2010-08-01
影响因子：
2.1
通讯作者：
Olago, Daniel O.
中科院分区：
文献类型：
--
作者：
Olaka, Lydia A.;Odada, Eric O.;Olago, Daniel O.
古海岸线序列和裂谷湖沉积物被用来重建东非过去的气候变化。这些记录东非大裂谷水文变化的记录器显示，在过去的两万年里，湖泊水位发生了数十至数百米的极端变化。另一方面，湖泊平衡和气候模拟结果表明，在这段时间内，降水蒸发平衡的变化相对温和。是什么导致了这样的差距？我们调查了湖泊流域的物理特征和水文，以解决这一差异。本研究使用了东非裂谷系（EARS）东部分支的9个封闭盆地湖泊，Ziway-Shalla、Awassa、Turkana、Suguta、Baringo-Bogoria、Nakuru-Elmenteita、Naivasha、Magadi-Natron、马尼亚拉和开放盆地湖泊维多利亚。我们创建了一个湖泊气候响应的分类方案的基础上，地形（高度积分）和气候（干旱指数）的经验措施。参考全新世早期的湖泊水位，我们发现，在埃塞俄比亚和肯尼亚圆顶的顶部的湖泊是最敏感的记录区域气候变化。在地堑形盆地中，其高度值介于0.23-0.29之间，其干旱指数高于1（潮湿）。在这10个湖泊中，EARS的3个湖泊是敏感湖泊：肯尼亚裂谷的Naivasha（HI = 0.23，AI = 1.20），埃塞俄比亚主裂谷的Awassa（HI = 0.23，AI = 1.03）和Ziway-Shalla（HI = 0.23，AI = 1.33）。苏加塔湖（HI = 0.29，AI = 0.43）和纳库鲁-埃尔门泰塔湖（HI = 0.30，AI = 0.85）对当地气候变化最为敏感。虽然今天相对较浅，略呈碱性，但在过去的20，000年里，它们的波动幅度是现代水深的4到10倍。五个研究湖泊是盘形的，在同一时期经历了较低的湖平面变化幅度。了解这些湖泊的敏感性对于确定区域尺度事件或趋势的时间或同步性以及预测全球气候变化后的未来水文变化至关重要。
Sequences of paleo-shorelines and the deposits of rift lakes are used to reconstruct past climate changes in East Africa. These recorders of hydrological changes in the Rift Valley indicate extreme lake-level variations on the order of tens to hundreds of meters during the last 20,000 years. Lake-balance and climate modeling results, on the other hand, suggest relatively moderate changes in the precipitation-evaporation balance during that time interval. What could cause such a disparity? We investigated the physical characteristics and hydrology of lake basins to resolve this difference. Nine closed-basin lakes, Ziway-Shalla, Awassa, Turkana, Suguta, Baringo-Bogoria, Nakuru-Elmenteita, Naivasha, Magadi-Natron, Manyara, and open-basin Lake Victoria in the eastern branch of the East African Rift System (EARS) were used for this study. We created a classification scheme of lake response to climate based on empirical measures of topography (hypsometric integral) and climate (aridity index). With reference to early Holocene lake levels, we found that lakes in the crest of the Ethiopian and Kenyan domes were most sensitive to recording regional climatic shifts. Their hypsometric values fall between 0.23-0.29, in a graben-shaped basin, and their aridity index is above unity (humid). Of the ten lakes, three lakes in the EARS are sensitive lakes: Naivasha (HI = 0.23, AI = 1.20) in the Kenya Rift, Awassa (HI = 0.23, AI = 1.03) and Ziway-Shalla (HI = 0.23, AI = 1.33) in the Main Ethiopian Rift (Main Ethiopian Rift). Two lakes have the graben shape, but lower aridity indices, and thus Lakes Suguta (HI = 0.29, AI = 0.43) and Nakuru-Elmenteita (HI = 0.30, AI = 0.85) are most sensitive to local climate changes. Though relatively shallow and slightly alkaline today, they fluctuated by four to ten times the modern water depth during the last 20,000 years. Five of the study lakes are pan-shaped and experienced lower magnitudes of lake level change during the same time period. Understanding the sensitivity of these lakes is critical in establishing the timing or synchronicity of regional-scale events or trends and predicting future hydrological variations in the wake of global climate changes.