Relationships between lake-level changes and water and salt budgets in the Dead Sea during extreme aridities in the Eastern Mediterranean
Relationships between lake-level changes and water and salt budgets in the Dead Sea during extreme aridities in the Eastern Mediterranean
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东地中海极端干旱期间死海湖水位变化与水盐预算之间的关系
DOI：
10.1016/j.epsl.2017.01.043
复制
发表时间：
2017
影响因子：
5.3
通讯作者：
Lazar, Boaz
中科院分区：
文献类型：
--
作者：
Kiro, Yael;Goldstein, Steven L.;Garcia-Veigas, Javier;Levy, Elan;Kushnir, Yochanan;Stein, Mordechai;Lazar, Boaz
死海深钻项目岩芯发现的厚岩盐间隔显示了地中海东部在过去三次间冰期期间严重干旱气候条件的证据。特别是，对应于末次间冰期（海洋同位素阶段5e或MIS 5e）峰值的岩心间隔在85米的岩心长度上含有约30米的盐，使其成为该地区第四纪晚期已知最干旱的时期。这项研究重建死海湖的水平在盐沉积的间隔，根据水和盐的预算来自死海卤水的组成和盐的量在核心。现代的水盐收支表明，岩盐只在湖平面下降时沉淀，而溶解的Na+和Cl−则在较湿润的时段积累。根据死海孔隙沃茨和岩盐流体包裹体的组成，我们估计每下降1米，就有12-16厘米的岩盐沉淀。在石盐沉淀期间，湖中的Mg 2+浓度增加，Na+/Cl−比率降低。我们的计算表明，在MIS 5e和全新世期间，主要的湖平面从海平面以下320和310米（mbsl）的湖平面下降到490和480 mbsl的湖平面，分别为170米。这些湖泊的水位远低于典型的间冰期湖泊的400 mbsl。这些湖平面的下降是由于平均淡水径流量大幅减少，减少到现代值（1964年以前，在主要的淡水分流之前）的40%左右，反映了严重的干旱，在此期间，耶路撒冷的年降水量低于350毫米/年，而今天为600毫米/年。然而，即使在盐的间隔，在盐岩相的变化和发生的交替时期的岩盐和碎屑在死海核心地层反映我们估计的平均值周围的干燥和潮湿的条件之间的波动。石盐间隔包括石盐丰富和贫乏的时期，表明（基于沉积速率）严重干旱的条件下，水的可用性低至今天的20%，持续了几十年至几个世纪，并随着更潮湿的条件波动，跨越几个世纪到几千年，当水的可用性是今天的50%-100%。这些结论对未来几十年具有潜在的影响，因为气候模型预测该地区将出现更大的干旱。
Thick halite intervals recovered by the Dead Sea Deep Drilling Project cores show evidence for severely arid climatic conditions in the eastern Mediterranean during the last three interglacials. In particular, the core interval corresponding to the peak of the last interglacial (Marine Isotope Stage 5e or MIS 5e) contains ∼30 m of salt over 85 m of core length, making this the driest known period in that region during the late Quaternary. This study reconstructs Dead Sea lake levels during the salt deposition intervals, based on water and salt budgets derived from the Dead Sea brine composition and the amount of salt in the core. Modern water and salt budgets indicate that halite precipitates only during declining lake levels, while the amount of dissolved Na+and Cl−accumulates during wetter intervals. Based on the compositions of Dead Sea brines from pore waters and halite fluid inclusions, we estimate that ∼12–16 cm of halite precipitated per meter of lake-level drop. During periods of halite precipitation, the Mg2+concentration increases and the Na+/Cl−ratio decreases in the lake. Our calculations indicate major lake-level drops of ∼170 m from lake levels of 320 and 310 m below sea level (mbsl) down to lake levels of ∼490 and ∼480 mbsl, during MIS 5e and the Holocene, respectively. These lake levels are much lower than typical interglacial lake levels of around 400 mbsl. These lake-level drops occurred as a result of major decreases in average fresh water runoff, to ∼40% of the modern value (pre-1964, before major fresh water diversions), reflecting severe droughts during which annual precipitation in Jerusalem was lower than 350 mm/y, compared to ∼600 mm/y today. Nevertheless, even during salt intervals, the changes in halite facies and the occurrence of alternating periods of halite and detritus in the Dead Sea core stratigraphy reflect fluctuations between drier and wetter conditions around our estimated average. The halite intervals include periods that are richer and poorer in halite, indicating (based on the sedimentation rate) that severe dry conditions with water availability as low as ∼20% of the present day, continued for periods of decades to centuries, and fluctuated with wetter conditions that spanned centuries to millennia when water availability was ∼50–100% of the present day. These conclusions have potential implications for the coming decades, as climate models predict greater aridity in the region.
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