Cave Monitoring in the Monsoon Region of China and Its Paleoclimatic Implications
Publication Date: 2024/12/01
Publication Volume: Journal of Cave and Karst Science 86 #
Publication Keywords: Cave monitoring, Monsoon Region of China (MRC), Stalagmite paleoclimate studies,
ABSTRACT:
Cave monitoring is essential for accurately interpreting the significance of proxies in stalagmite records. Here, we have compiled published monitoring data from 14 caves in the monsoon region of China (MRC), including cave air temperature (Tin), cave air relative humidity (RH), cave air CO2 concentration (PCO2), multiple proxies (δ18O, δ13C, Trace element (TE)/Ca) in drip water and associated modern calcite, to serve as a reference for the stalagmite paleoclimate studies. The seasonal variations in these monitoring parameters were demonstrated through a carefully selected 24-month observation period at the cave sites. The seasonal variations in Tin, RH, and cave air PCO2 mainly depended on the local climate conditions and the degree of cave ventilation or tourist activities. Furthermore, the type and degree of ventilation were regulated by the site-specific karst structure system, such as the size of fractures, fissures, entrances and their relative altitude. The spatial-temporal variations observed in the behavior of δ18O, δ13C and TE/Ca in drip water and modern calcite can be attributed to the unique processes and environment prevailing within each cave. These in-cave processes and environment, including prior calcite precipitation (PCP), incongruent calcite dissolution (ICD), water-rock interaction (WRI), evaporation, drip rates, and calcite growth rates, are intricately related to the surface climate or hydrological conditions. Before applying geochemical proxies in stalagmites to paleoclimatic reconstruction, it is essential to ascertain the response mechanism of these geochemical proxies to those in-cave processes and surface climate or hydrological conditions, in addition to the replication test. More comprehensive cave monitoring studies with systematic design and longer durations are necessary for improving interpretations of proxies preserved in stalagmites.
SIMPLE LANGUAGE SUMMARY:
Scientists are studying caves in the Monsoon Region of China to learn about the Earth's climate history. Inside caves, formations like stalagmites hold clues about past weather patterns, such as rainfall and temperature, over thousands of years. These clues come from special markers, like oxygen and carbon isotopes, in the water and minerals in the caves. The researchers looked at data from 14 caves to understand how things like air temperature, humidity, and carbon dioxide inside the caves change with the seasons. They also studied how water dripping into the caves interacts with the rocks and air to form stalagmites. These processes can show how outside weather, like heavy rain or drought, affects the caves. The scientists found that the conditions inside caves, such as airflow and water movement, are very important for interpreting the climate clues in stalagmites. By studying these caves carefully, they hope to better understand how the climate has changed over time and how it might change in the future.
REFERENCES:
Baldini, J.U.L., McDermott, F., Fairchild, I.J., 2008, Spatial variability in cave drip water hydrochemistry: Implications for stalagmite paleoclimate records: Chemical Geology, v. 235, no. 3–4, p. 390–404.
Baker, A., Hellstrom, J., Kelly, B.F., Mariethoz, G., Trouet, V., 2019, A composite annual-resolution stalagmite record of North Atlantic climate over the last three millennia: Scientific Reports, v. 9, p. 1–10.
Cai, Y., Zhang, H., Tan, L., Cheng, H., An, Z., Edwards, R.L., Wang, X., 2021, A high-resolution speleothem record of the 8.2 ka event from central China: Earth and Planetary Science Letters, v. 570, p. 117061.
Cheng, H., Sinha, A., Wang, X., Cruz, F.W., Edwards, R.L., 2019, The global paleomonsoon as seen through speleothem records from Asia and the Americas: Climate Dynamics, v. 52, p. 619–659.
Duan, W., Ruan, J., Zhao, C., Zhou, F., Shen, Z., He, Y., 2016, δ18O composition in drip water and modern calcite from Furong Cave, southwestern China: Chemical Geology, v. 430, p. 11–22.
Fairchild, I.J., Baker, A., 2012, Speleothem Science: From Process to Past Environments: Wiley-Blackwell, Oxford, UK, 416 p.
Fairchild, I.J., Smith, C.L., Baker, A., Fuller, L., Spotl, C., Mattey, D., McDermott, F., E.I.M.F., 2006, Modification and preservation of environmental signals in speleothems: Earth-Science Reviews, v. 75, p. 105–153.
Frisia, S., 2015, Microstratigraphic logging of calcite fabrics in speleothems as tool for palaeoclimate studies: International Journal of Speleology, v. 44, no. 1, p. 1–16.
Li, H., Feng, W., Ma, Y., 2021, Seasonal variations in cave air pCO2 and drip water δ18O values at Jiguan Cave, central China: Implications for paleoclimate reconstruction: Quaternary Science Reviews, v. 269, p. 107138.
Wang, Y.J., Cheng, H., Edwards, R.L., Kong, X.G., Shao, X.H., Chen, S.T., Wu, J.Y., 2008, Millennial- and orbital-scale changes in the East Asian monsoon over the past 224,000 years: Nature, v. 451, p. 1090–1093.
