Paleoclimate reconstruction in northern vietnam in the duration 3 5 5ka using δ18o and δ13c in a stalagmite in nam son cave, hoa binh province

VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY NGUYEN THI QUE PALEOCLIMATE RECONSTRUCTION IN NORTHERN VIETNAM IN THE DURATION 3.5-5KA USING δ18O AND δ13C IN A STALAGMITE IN NAM SON CAVE, HOA BINH PROVINCE MASTER’S THESIS VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY NGUYEN THI QUE NGUYEN THI QUE PALEOCLIMATE RECONSTRUCTION IN NORTHERN VIETNAM IN THE DURATION 3.5-5KA USING δ18O AND δ13C IN A STALAGMITE IN NAM SON CAVE, HOA BINH PROVINCE MAJOR: CLIMATE CHANGE AND DEVELOPMENT CODE: 8900201.02QTD RESEARCH SUPERVISOR Dr Nguyen Thuy Duong Hanoi, 2022 PLEDGE In writing this master’s thesis, I have read and understood the plagiarism violations I pledge with personal honor that this research result is my own and does not violate the Regulation on prevention of plagiarism in academic and scientific research activities at VNU Vietnam Japan University (Issued together with Decision No 700/QD-ĐHVN dated 30/9/2021 by the Rector of Vietnam Japan University) I assure that this thesis is the result of my own research and has not been published The use of other research’s results and other documents must comply with regulations The citations and references to documents, books, research papers, and websites must be in the list of references of the thesis I am aware that not documenting source material or not citing clearly, correctly, and completely constitutes plagiarism Author of the thesis Nguyen Thi Que i ACKNOWLEDGMENTS Firstly, I would like to express my gratitude to my supervisor, Dr Nguyen Thuy Duong, working in Vietnam Japan University, Vietnam National University in Hanoi, for her guidance and suggestions to complete this thesis More than anything, she gave me a chance to access the new aspects in science of geology and climate change, which was very new to me I also appreciate her take care and guidance during field trips Secondly, I would like to thank to Ms An Thi Thuy, working at Vietnam national museum of nature, Vietnam academy of science and technology for her explanation about U/Th dating method and result, Dr György Czuppon, working at the Institute for Geological and Geochemical Research, RCEAS, ELKH, Budapest, Hungary, for his explanation about the method of 13 C, 18 O stable isotope analyzing and instruction in StalAge model Thirdly, I would like to thank to Dr Nguyen Tai Tue, Vietnam National University in Hanoi, for your additional classes for stable isotopes and using stable isotopes on studying in geology and climate change I also thank The Vietnam National University, Hanoi research project (Grant number QG.20.11, PI Thái Nguyễn-Đình: “Holocene paleoclimate recorded from lake sediment in the south of Central Highlands”) for supported document, approach methods for the thesis completion Finally, I would like to thank all friends and family for their encourage and support during research’s duration TABLE OF CONTENTS Page PLEDGE ACKNOWLEDGMENTS LIST OF TABLES i LIST OF FIGURES ii LIST OF ABBREVIATIONS iii CHAPTER INTRODUCTION 1.1 The necessity of the research .1 1.2 The research questions and hypotheses .3 1.3 Research objectives and tasks .3 1.4 The scope of the research 1.5 Research conceptual framework 1.6 Matrix of learning outcomes for the master’s thesis 1.7 Literature review 1.7.1 Overview on paleoclimate events in the Holocene 1.7.2 Overview on paleoclimate studies using speleothems in Asia and Vietnam 1.7.3 Overview on speleothem sampling and precipitation monitoring for stable isotope interpretation 11 1.8 Study area 14 CHAPTER MATERIALS AND METHODOLOGY 17 2.1 Materials 17 2.2 Background of the methodology .18 2.2.1 Some principles concept 18 2.2.2 Hendy Test for evaluating the presence of isotopic equilibrium 21 2.2.3 Age determination by U-Th method 22 2.2.4 Determination of δ13C and δ18O composition of carbonates 23 2.2.5 Determination of δD and δ18O compositions of water 24 2.3 Methods .24 2.3.1 Field and monitoring methods 24 2.3.2 Data analysis 28 CHAPTER RESULTS AND DISCUSSIONS 30 3.1 Test of stable isotope equilibrium .30 3.2 The Age model 32 3.3 δ18O and δ13C values in the NS4 stalagmite 35 3.4 δ18O variation in rainwater and relationship to Precipitation in Northern Vietnam 36 3.5 δ18O and δ13C value in rainwater, drip water and carbonate in Nam Son cave.39 3.6 Paleoclimate change in the duration 3.5-5ka in the northern Vietnam .40 CHAPTER CONCLUSION AND RECOMMENDATIONS 43 4.1 Conclusion 43 4.2 Recommendations .43 REFERENCES 45 APPENDIX 52 LIST OF TABLES Page Table 1.1 Research question and hypothesis of the study Table 1.2 Objectives and tasks of the study Table 1.3 Matrix of learning outcomes for the master’s thesis Table 2.1 Specifications of Portable CO2 Analyzer - model 77535 AZ 25 Table 2.2 Technical data of Drop counter Stalagmate 26 Table 3.1 Checking results of climate parameters 31 Table 3.2 230Th results of stalagmite NS4 from Nam Son cave (2021) 34 Table 3.3 Isotopic composition in drip water and rainwater in Nam Son cave 39 Table 3.4 Isotopic composition in fresh carbonate in Nam Son cave 40 i LIST OF FIGURES Page Figure 1.1 Research conceptual framework .6 Figure 1.2 Location map of studied caves and monsoon activities in China 11 Figure 1.3 Location of Nam Son cave .14 Figure 1.4 A sketch on Nam Son Cave structure .15 Figure 1.5 Outside of Nam Son Cave 16 Figure 1.6 Climate parameters in Mai Chau District, Hoa Binh Province 16 Figure 2.1 Sample for U-Th dating analysis 17 Figure 2.2 Sample NS4 17 Figure 2.3 Principle of U/Th dating method 22 Figure 2.4 A Thermo Finnigan Delta Plus XP mass spectrometer 25 Figure 2.5 Portable CO2 Analyzer 25 Figure 2.6 Drip counter Stalagmate 27 Figure 2.7 Checking the calcite deposition 27 Figure 2.8 Setting up for monitoring in Nam Son cave 28 Figure 3.1 Inside the Nam Son Cave .31 Figure 3.2 Polished section (left) and age model (right) of stalagmite NS4 33 Figure 3.3 Cross-plot of Age versus depth in stages 35 Figure 3.4 Result of δ18O and δ13C analysis and correlation 36 Figure 3.5 Location of Hanoi and Son La meteorological stations 37 Figure 3.6 Wind Frequency and Direction Rose in Hanoi and Hoa Binh .37 Figure 3.7 Precipitation, Temperature and δ18O value in Hanoi station 38 Figure 3.8 Result of checking correlation of variables in Hanoi station 38 Figure 3.9 Places of collecting cacbonate samples in Nam Son cave .41 ii LIST OF ABBREVIATIONS AR6 Sixth Assessment Report ASL Above Sea Level ASM Asian Summer Monsoon COP Conference of the Parties EIMF European Institute of Management and Finance GNIP Global Network of Isotopes in Precipitation IAEA International Atomic Energy Agency IPCC Intergovernmental Panel on Climate Change IRMS Isotope ratio mass spectrometer IUGS The International Union of Geological Sciences NOAA National Oceanic and Atmospheric Administration PLO Program Learning Outcome SSP Shared Socio-econimic Pathways iii CHAPTER INTRODUCTION 1.1 The necessity of the research Paleoclimatology, a term for the study of the past climates, just has been expanding in the scientific field in recent decades while systematic weather observations began in the late 1800s (Elias, 2021; Peterson, 2021), greatly aided our understanding of current and future climate by understanding of the controls and causes of past climatic variations (Mock, 2013) Paleoclimate data can also test the accuracy of current circulation models The contribution of paleoclimatic studies is important for human life because the climate has undenied effects on human activities through agriculture, biological system, and environmental quality This research’s results became more essential in the condition of high-warming stories today when the current level of atmospheric carbon dioxide is the highest in human history As NOAA’s measurements, the globally averaged annual mean CO2 concentration reached 409.9 ± 0.4 ppm in 2019 and reached 417.81 ppm in February 2022 (NOAA, 2022) In 2021, IPCC stated that in all scenarios assessed in AR6 (except SSP5-8.5), the 1.5oC threshold crosses in the early 2030s (IPCC, 2021) COP26 in 2021 again emphasized the value of research and responses related to global climate changes Located in the Indochinese peninsula, Vietnam is one of the countries which are strongly affected by climate change Lately, research on adaptation and mitigation has been attracting a great deal of funding in both economic and technical fields, from not only the Vietnam government but also from developed countries and global organizations In parallel, the study of the paleoclimate proved its importance in resulting in the climate change impacts and limitations Some climate events were recorded globally with different expressions in each specific area Until now, the paleoclimate studies in Vietnam have been quite small compared to the world However, multiarchives such as Based on the analysis result in Hanoi station and the resemblance between Hanoi and Hoa Binh province, we can state for the same dependence of δ18O value in rainwater on precipitation amount in Hoa Binh Province at high confidence 3.5 δ18O and δ13C value in rainwater, drip water and carbonate in Nam Son cave The drip water monitoring inside the cave was started in March, 2022 At the 1st place in 3rd chamber, the amount of drip water in March was very little, not enough to collect samples for isotope analysis Average rainfall in March at Mai Chau station is around 22mm (Fig 1.6) In addition, the weather this year is different from previous years, the rainy season came later, so the rainfall in March may be less than 22mm When we collected the drip sample in the cave in April, we got a larger amount of drip that is consistent with the increased rainfall in April Rainfall in May was increased sharply, we also got a lot of dripwater inside the cave It explained that rainwater is seeped through the rock layers and quickly enters the cave and can compare the value of δ18O monthly in rainwater and dripwater to examine the relationship between these two values The results of initial analysis of isotopic composition in drip water and rainwater collected in May 2022 (Table 3.3.) show that δ18O is depleted in drip water to -9.31‰ SMOW, while the value in rain water is -1.99‰ SMOW Table 3.3 Isotopic composition in drip water and rainwater in Nam Son cave Analyzing samples of fresh carbonates collected on 16 May 2022 shows that the δ18O values in calcite precipitates increased to +19.94‰ and +23.47‰ SMOW (Table 3.4) In this case, oxygen isotopic fractionation is from 29 ~ 33‰ between calcite and water (temperature in 2nd chamber is ~20oC) δ18O value in fresh carbonate samples are -10.64‰ 39 and -7.22‰ VPDB, in the range of values in NS4 δ13C values in fresh carbonate samples are -12.79‰ and -4.12‰ VPDB, out of the range in NS4 Table 3.4 Isotopic composition in fresh carbonate in Nam Son cave Samples Site 2nd Nam VN-11 Chamber Son 2nd Cave VN-6 Chamber δ13C (‰ VPDB) δ18O (‰ VPDB) δ18O (‰ SMOW) XRD results -12.79 -10.64 +19.94 calcite -4.12 -7.22 +23.47 calcite The comparison of δ13C and δ18O value in carbonate samples and NS4, together with the corresponding values in rainwater and drip water are necessary for interpretation paleoclimate parameters However, up to now, the sample quantity has been too small for any conclusion The further observation and analysis must be carried out through a longer period 3.6 Paleoclimate change in the duration 3.5-5ka in the northern Vietnam 3.6.1 Records of 4.2 ka It is a pity that due to hiatus from 4.5ka to 4.1ka, no carbonate was formed However, the hiatus in this period may reflect a change in climate conditions The hiatus could be explained by assumptions: no water for deposition chemical reaction, or too much water with high speed of dripping so that deposition chemical reaction could not form We placed glass plates under water droplets with different drip rates to examine the rate of carbonate precipitation at those locations (Fig 3.9) The checking results from Mar to May 2022 showed that stalagmites under fast dripping water droplets are usually very clean while stalagmites under non-drip locations are usually dark in color The changing from white color to dark color marks for the hiatus in stalagmite formation process It is similar with sample in study of Lewis et al., (2011) The relationship between the growth rate of stalagmite and coloration was studied as an initial exploration by Campa-Bousoño et al., (2021) In fact, the color of stalagmite is determined by mineral content and acids produced from surface vegetation In case of plentiful and high-speed 40 drip water, these matters will be washed away so be unlikely to accumulate on the surface of stalagmites Therefore, from the color of NS4 stalagmites around the discontinuity, we supposed the first hypothesis of no water for deposition Possibly due to drier climatic conditions, the droplet rate of stalagmite-forming water gradually decreased and ceased, leading to a discontinuity of carbonate precipitation over a period of 4.5-4.1 ka BP Figure 3.9 Places of collecting cacbonate samples in Nam Son cave A, B Stalagmite under rapid droplets C Stalagmite under slow droplets 3.6.2 Other paleoclimate events From 5.0 ka to 4.7 ka – the periods of higher growth rate correspond to the periods of lower δ13C and δ18O The lower δ18O in stalagmite may indicate a duration of more summer monsoon precipitation, and higher temperature The interpretation is supported by analysis of stable isotope data set in rainwater in Hanoi station The fluctuation of rainfall and δ18O value in rain water in years showed that when rainfall strongly increases, the δ18O value in rain water decreases (Fig 3.9) The lower value of δ13C indicated the more density of vegetation, as the result of higher temperature and precipitation in this period (proved by Lechleitner et al., (2021)) Besides, the higher summer monsoon precipitation was also recorded in other studies in neighborhood’s area Wang et al., (2005) reported a decrease of δ18O value which was considered as the effect of strengthen monsoon and higher precipitation in the duration 41 of 4.9ka - 4.45ka, based on data from a stalagmite in Dongge cave The δ18O value in stalagmite in Dongge cave was deeply decreased (~ -8.4‰), suggested a wet period Zhang et al., (2018), studied on the stalagmite SN17 in Shennong Cave, suggested the same results of wet condition with a drier trend from 5.0 ka to 4.7ka BP These studies above was implemented in Sourthern China, where the climate is also influenced mainly by Asian monsoon At around 4.7ka BP, the value of δ13C in stalagmite NS4 sharply decreased, while δ18O value also decreased at lower speed and smaller amplitude The difference in variation of δ18O and δ13C values may be caused by the stronger impact of changing in temperature Supported by study of Fohlmeister et al., (2020), the δ13C values in stalagmite is decreasing stated a warmer period The δ18O value decreased suggested a strengthen monsoon rainfall This 4.7ka event was also recorded at medium confidence in research of H Zhang et al., (2018), when δ18O and δ13C values in sample SN17 also lightly decreased After a hiatus period, δ18O values appeared with relatively high value during 4000s year BP and 3800s year BP, suggested an around 200 years duration of drier condition with weakening monsoon rainfall About temperature, the higher value of δ13C may suggest a colder condition The result of age determination on the top of NS4 is abnormal as mentioned in article 3.2, the interpretation about paleoclimate in 4.0-3.8ka BP based on isotope data in stalagmite NS4 is at medium-low confidence However, the hypothesis of drier condition within this period also was supported in study of Wang et al., (2005), as the δ18O value from stalagmite in Dongge cave reached the peak of -7.4‰ From 3.8ka to 3.5ka BP, due to no value of δ18O and δ13C and abnormal in age determination, we will skip the interpretation for paleoclimate in northern Vietnam in this duration 42 CHAPTER CONCLUSION AND RECOMMENDATIONS 4.1 Conclusion This thesis focused on using the δ18O and δ13C values in stalagmite NS4 in Nam Son cave, Hoa Binh province to reconstruct climate and evironment changes in period of 5.0-3.5ka BP in the northern Vietnam Climate intervals in chronological order are wet and warm (5.0-4.7ka), very wet and warm (4.7ka), proposal of dry (4.5-4.1ka), and drier (4.0-3.8ka) Wet climate also referred to the increase in rainfall with the stronger ASM intensity The research results were supported by other studies in neighborhood’s areas of Southern China Related to the 1st research question about the record of 4.2ka cooling event, in fact, sample NS4 has no formation data before and after 4.2ka BP, therefore, the recognition is limited at the assumption of a dry period in Northern Vietnam δ18O values in precipitation variates inversely with precipitation amount while precipitation is the main source of drip water inside the cave Therefore, δ18O values in the stalagmite NS4 is mainly affected by precipitation In the areas with the activities of monsoon, the monsoon intensity is the main factor affects to precipitation Sample NS4 has age determination from 5.0ka to 3.5ka BP However, abnormal values on the top of stalagmite and hiatus in 4.5-4.1ka BP and 3.8-3.5ka BP lead to the impossibility in paleoclimate reconstruction in these periods Only from 5.0ka to 4.5ka BP, the formation of stalagmites is clearly recorded, making the interpretation of paleoclimate is relatively high confidence 4.2 Recommendations The hiatus in stalagmite NS4’s formation is considered as not enough to provide fully paleoclimate information during 5.0 and 3.5ka BP Therefore, it is necessary to find another stalagmite with the same age in Northern Vietnam to support and complete the original objectives of this thesis 43 Up to now, the result of monitoring has been limited at a month To achieve a better interpretation in this case, the monitoring needs to be implemented continuosly in at least year to verify the relationship between isotope values in rainfall, drip water and carbonate precipitates The variability of these values, when compared with the data in stalagmites, will lead to more accurate conclusions about paleoclimate parameters’ values The changes in paleoclimate in the Northern Vietnam can be used to explain the changes in agriculture activities and habitat as a way human adapted with climate change in the civilization history Application of paleoclimate studies are not only limited at the explanation of the cause of civilization evolution and creature’s extinction, but also supplying data for future climate prediction In the context of increasingly severe climate change since Industrial Revolution because of increasing greenhouse gases concentration in atmosphere and changing in land cover, paleoclimate data is used to improve climate models for more accurate forecasts Northern mountainous area is one 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response for development; identifying, analyzing, assessing and forecasting the issues related to CC and CCR; predicting the developing trend of CC science PLO4: Applying knowledge to solve the problems in CC and CCR: planning and approaching the works in field of CC; proposing the initiatives as well as the researches on CC; implementing the solutions on science, technology, mechanism, policy and finance for CCR and development PLO5: Having skills of cooperation with personal, agencies, organizations domestically and internationally to solve the CC issues, communication in works, projects on CC; and organizing, managing and administrating advanced career development PLO6: Accumulating soft skills to self-directed and adapt to competitive working environment such as English proficiency (at level 4/6 according to English competencies Framework for Vietnam), Japanese communication skills; having skills on time management; using the basic computer skills proficiently; working and researching independently; having skills of research and development; and using technologies creatively in academic and professional fields PLO7: Dynamic, confident, persistent, enthusiastic, and risk-taking and management 52 PLO8: Having social/community’s responsibility and professional morality, especially for the scientific research results; being able to adapt to multicultural environment, ensure the harmony between the stakeholders, CCR and development; having good social morality, assist the vulnerable people to climate change; compliance with the law; discipline at work and positive lifestyle; having good attitude to their career in climate change response for sustainable development PLO9: Having responsibility for researching, creating new knowledge, and offering new ideas on climate change response in different complex situations; adapting and guiding other people and making expert decisions on climate change response; managing research, having high responsibility in learning in order to develop professional knowledge, and creating new ideas in new process; and having good life-long learning capacity 53