Stable isotope constraints on the transport of water to the Andes between 22° and 26°S during the last glacial cycle
Stable isotope constraints on the transport of water to the Andes between 22° and 26°S during the last glacial cycle
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DOI：
10.1016/s0031-0182(03)00283-9
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发表时间：
2003-05-15
影响因子：
3
通讯作者：
Alonso, RL
中科院分区：
文献类型：
--
作者：
Godfrey, LV;Jordan, TE;Alonso, RL
安第斯山脉大部分地区南纬 22 度至 26 度之间的现代气候非常干燥。来自干涸湖床的年代沉积物岩心含有盐沉积物（盐沼），其中含有岩盐结构，表明在以前、较小的气候条件下，盐湖存在于 Salar de Hombre Muerto（阿根廷西北部，安第斯高原）和 Salar de Atacama（智利北部，安第斯山脉西侧）。古气候条件是根据湖相石盐流体包裹体中的古咸湖水的稳定同位素组成重建的。应用同位素稳态模型来估计古湖泊流入（大气）水和古大气水蒸气的同位素组成。这两个撒拉族的气候记录不同。阿塔卡马盐湖的形成时间与东北高原上的湖水位高位相似，最深的湖泊出现在 24 至 19.8 ka 之间。阿塔卡马和安第斯山脉中部的现代大气水源目前是通过亚马逊盆地的热带大西洋，稳定同位素证据表明阿塔卡马古湖泊的水源相同。相比之下，在东南部的 Hombre Muerto，自 45 ka 以来，间歇性占据盐湖的湖泊逐渐变小。今天的水同位素组成反映了通过蒸发冷凝的大气再循环，就像在 24 到 20ka 之间那样，而输送到早期湖泊的水并不表明显着的同位素再循环。利用现代大气/海洋环流和强迫机制的知识，我们假设这些安第斯地区的水分输送变化与赤道和南大西洋大气和海洋表面环流直接相关。 (C) 2003 Elsevier Science B.V. 保留所有权利。
The modern climate over much of the Andes between 22degrees and 26degreesS is very dry. Dated sediment cores from desiccated lake beds contain saline deposits (salars) that have halite fabrics that indicate during previous, less and climates saline lakes existed at Salar de Hombre Muerto (northwest Argentina, Andean plateau) and Salar de Atacama (northern Chile, west flank of Andes). Paleoclimate conditions are reconstructed from the stable isotope composition of paleo-saline lake waters trapped in fluid inclusions in lacustrine halite. Models of isotopic steady state are applied to estimate the isotopic composition of inflow (meteoric) water to the paleo-lake and paleo-atmospheric water vapor. The two salars' climate records differ. The timing of Atacama saline lakes is similar to lake level highstands on the Altiplano to the northeast with the deepest lake occurring between 24 and 19.8 ka. The modern meteoric water source for Atacama and the Central Andes is currently the tropical Atlantic, via the Amazon Basin, and stable isotopic evidence indicates the same source of water for the paleo-lakes in the Atacama. In contrast, to the southeast, at Hombre Muerto, the lakes that intermittently occupied the salar became progressively smaller since 45 ka. Water isotope composition today reflects atmospheric recycling by evaporation-condensation, as it did between 24 and 20 ka, whereas water transported to the earlier lakes does not indicate significant isotopic recycling. Using knowledge of modern-day atmosphere/oceanic circulation and forcing mechanisms, we hypothesize that the shifts in moisture transport to these Andean sites are directly tied to equatorial and South Atlantic atmospheric and oceanic surface circulation. (C) 2003 Elsevier Science B.V. All rights reserved.