Lake water isotope variation linked with the in-lake water cycle of the alpine Bangong Co, arid western Tibetan Plateau
Lake water isotope variation linked with the in-lake water cycle of the alpine Bangong Co, arid western Tibetan Plateau
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青藏高原西部干旱区高山班公错湖水同位素变化与湖内水循环的关系
DOI：
10.1657/aaar0015-028
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发表时间：
2016
影响因子：
2
通讯作者：
Qu Dongmei
中科院分区：
文献类型：
--
作者：
Wen Rong;Tian Lide;Liu Fengjing;Qu Dongmei
水同位素在青藏高原西部干旱地区高山湖泊水量平衡和水文循环研究中具有重要作用。这些来自保存完好的沉积物的同位素记录被认为反映了气候和环境的变化。利用青藏高原西部干旱区班公湖（LBG）降水、河水、地下水和湖水的δ 18 O和δD资料，结合当地气象观测资料，研究表明，由于湖水蒸发，班公湖的δ 18 O比当地降水的δ 18 O富集10‰以上。湖水δ 18 O和δD - 8 * δ 18 O的空间变化明显，从东到西，δ 18 O和δD - 8 * δ 18 O的变化范围分别为-4.9‰ ~+0.9‰和-13.22‰ ~-30.85‰。Craig-Gordon模型的模拟结果表明，高山内陆湖水中的同位素在很大程度上受当地相对湿度的控制。利用改进的部分混合同位素分馏模型，我们重建的蒸发/流入（E/I）比的空间变化从东到西的湖泊。定量估算结果表明，东、西两个湖区湖水的E/I值分别为0.73 ± 0.83和0.90 ± 0.93。我们还发现，通过假设环境蒸汽同位素的动力学分馏的充分发展，我们的模拟结果匹配观测到的空间变化的δ 18 O和d-过剩，证实了强烈的内陆蒸发富集在北方的高原部分。该研究将有助于加深对青藏高原湖泊内陆水运动的认识，也将有助于加深对湖泊沉积物同位素记录的认识。
ABSTRACT Water isotopes play an important role in the study of the alpine lake water budget and the hydrological cycle in the arid, far western Tibetan Plateau. These isotope records, derived from well-preserved sediments, are believed to reflect climatic and environmental changes. Using two years of δ18O and δD data from precipitation, river water, underground water, and lake water at the long alpine lake Bangong (LBG), together with local meteorological observations in the arid western Tibetan Plateau, this study reveals that the δ18O in the lake is over 10‰ more enriched than that in the local precipitation due to evaporation of the lake water. Spatial changes in both the lake water δ18O and d-excess (= δD - 8 * δ18O) are apparent, ranging from ∼-4.9‰ to +0.9‰ for δ18O, and -13.22‰ to -30.85‰ for d-excess, respectively, from east to west of the lakes. Simulation with the Craig-Gordon model shows that the isotopes in alpine inland lake water are controlled to a great extent by local relative humidity. Using a modified partly mixed isotope fractionation model, we rebuilt the spatial change of the evaporation/inflow (E/I) ratios from east to west of the lake. A quantitative estimation shows that the E/I ratio of the lake water increases from 0.73∼0.83 in the eastern part and 0.90∼0.93 in the western part of LBG. We also found that by assuming a full development of kinetic fractionation of the environmental vapor isotopes, our simulation result matched the observed spatial change for both δ18O and d-excess, confirming the strong inland evaporation enrichment in the northern part of the plateau. This research may increase our understanding of inland water movement in the alpine Tibetan lakes, and also will improve our understanding of the lake sediment isotope record.