State Key Laboratory of Frozen Soil Engineering, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.
State Key Laboratory of Frozen Soil Engineering, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.
Sci Total Environ. 2020 Aug 10;729:138966. doi: 10.1016/j.scitotenv.2020.138966. Epub 2020 Apr 24.
The stable-isotope data of ground ice from a deep borehole (~46 m) at the Tianshuihai (TSH) lake basin on the northwestern Qinghai-Tibet Plateau (QTP) are presented together with cryolithological information. Remarkable variations in the stable isotope composition of ground ice at depths allow a division of five clearly delineated stages. The remarkable deviations in stable isotopes of ground ice during each stage underline different initial source water and formation processes, indicating considerable fluctuations in paleo-lake conditions and multiple patterns of climatic-induced permafrost evolutions. In combination with the ground ice isotopes for two deep boreholes on the interior QTP, the position of the present permafrost table is found at 2-3 m. Two possible positions of paleo-permafrost tables at depths of 7-8 and 15-16 m are identified based on the ice isotopic composition of wellbores in combination with those from the other two deep boreholes on the interior QTP. The high uniformity in stable isotopic composition of ground ice below the depth of 16 m may have reflected the consistent regional climate transitions and the resultant permafrost evolution on the QTP. This study provides some new insights on the ground ice as an indicator for permafrost evolution on the QTP.
本文呈现了青藏高原西北部天山水湖盆地（TSH）一个深钻孔（约 46 米）的基岩冰稳定同位素数据，并结合了低温岩石学信息。基岩冰稳定同位素组成在深度上的显著变化允许分为五个明显划定的阶段。每个阶段基岩冰稳定同位素的显著偏差强调了初始水源和形成过程的不同，表明古湖泊条件存在相当大的波动和气候引起的多年冻土演化的多种模式。结合青藏高原内部两个深钻孔的基岩冰同位素，发现现今多年冻土上限位于 2-3 米处。根据钻孔冰同位素组成以及青藏高原内部另外两个深钻孔的结果，确定了深度为 7-8 和 15-16 米处古多年冻土上限的两个可能位置。在 16 米以下深度，基岩冰稳定同位素组成的高度均匀性可能反映了青藏高原区域气候的一致转变以及由此产生的多年冻土演化。本研究为多年冻土演化提供了一些关于基岩冰作为指示物的新见解。
