JpGU-AGU Joint Meeting 2020

講演情報

[E] 口頭発表

セッション記号 M (領域外・複数領域) » M-IS ジョイント

[M-IS08] 古気候・古海洋変動

コンビーナ:岡崎 裕典(九州大学大学院理学研究院地球惑星科学部門)、Benoit Thibodeau(University of Hong Kong)、山本 彬友(国立研究開発法人 海洋研究開発機構)、長谷川 精(高知大学理工学部)

[MIS08-05] Reconstruction of paleoclimatic signals from groundwater in large aquifers-a case study in Leizhou peninsula, Southern China

*Shaoheng Li1Jianyao Chen1Dioni Cendon2Florian Freundt3Zongyu Chen4Guomin Yang5Shuang Xiao2 (1.School of Geography and Planning, Sun Yat-sen University, Guangzhou, China、2.Australian Nuclear Science and Technology Organisation, Kirrawee, Australia、3.Institute of Environmental Physics, Heidelberg University, Im Neuenheimer Feld 229, 69120 Heidelberg, Germany、4.Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences, Shijiazhuang, China、5.Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, China)

キーワード:Paleoclimate reconstruction, Groundwater , Multiple tracers, Noble gases, Stable isotopes

The past is the key to the future, Knowledge of the paleoclimate is essential to understand the present climate and project potential future climate scenarios. Groundwater in aquifers, though as a low time-resolution archive, can provide valuable information regarding past climate change. In this study, 13 deep monitoring wells were chosen for water sampling during our first fieldwork in Leizhou peninsula, a (sub)tropical area in southern China. Multiple tracers (3H, 4He, 14C, 81Kr, 85Kr) were applied for accurate groundwater dating and the concentration of noble gases dissolved in groundwater was measured for paleotemperature reconstruction. Stable isotopes (2H, 13C, 18O), major ions and other geochemical properties were also analyzed for these samples. According to the preliminary results, most groundwater samples’ age is located in the dating range of 14C and shows a relatively continuous record through the past 30,000 years. A possible recharge gap during LGM (Last Glacial Maximum) is identified and may indicate a quite cold and dry environment during this period in Leizhou peninsula. Paleotemperature revealed by the physically-based NGT (Noble Gas Thermometer) method shows that at least an environment temperature difference of 3.4 ℃ exists between the cold period and the present. A detailed comparison between NGTs, excess air (represented by ΔNe) and 18O indicates that the major controlling factor of stable isotopes (2H and 18O) in local groundwater might be the amount of precipitation rather than temperature, therefore the signals of 18O in groundwater can be interpreted as the change of moisture. Together with the NGTs, it is possible to reconstruct the paleoclimate information (including the climate state of warm/cold and wet/dry) through the groundwater archive in this study area. In addition, the groundwater dating results and recharge history revealed by this study can assist in local groundwater resource management and exploitation.