| Summary: | 학위논문 (석사)-- 서울대학교 대학원 : 자연과학대학 지구환경과학부, 2018. 2. 안진호. Atmospheric nitrous oxide (N2O) is an important long-lived greenhouse gas and effective stratospheric ozone destroyer. Despite its essential roles in climate, the control mechanisms of atmospheric N2O remains poorly understood. In order to reconstruct atmospheric N2O during pre-industrial era, I precisely analyzed ice core samples from NEEM site in North Greenland and Styx Glacier in East Antarctica. The N2O records cover the last two millennia with a precision better than 1.9 ppb and averaged temporal resolution of ~10 years, sufficient to constrain centennial-scale variations. The N2O records from Styx and NEEM ice commonly show distinctive centennial-scale variations. The timings of rapid N2O changes are coincident each other. The rates of rapid N2O changes are comparable to current ones which is strongly affected by anthropogenic sources. These findings suggest that there was significant natural and/or anthropogenic variability of atmospheric N2O during pre-industrial era. In these centennial-scale N2O variation, the portion of oceanic source changes seemed to be more significant than terrestrial sources, although temperature and precipitation changes in the terrestrial regions also seemed relevant with short-term N2O change in part. The negative correlation with sea surface temperature near Peruvian margin and productivity and denitrification reconstruction data suggests enhanced oceanic N2O flux during the La Niña-like state, and possibly, the solar activity changes contributed to the centennial N2O variation as an ultimate cause. 1. Introduction 1 1.1. Sources and sinks of atmospheric nitrous oxide (N2O) 1 1.2. Previous ice core studies 4 1.3. Objectives 6 2. Materials and Methods 8 2.1. Sample materials 12 2.1.1. Styx Glacier ice 12 2.1.2. NEEM ice 13 2.2. Air extraction from ice 14 2.3. Concentration measurement procedure 16 2.4. Optimization of gas chromatograph 18 2.5. Correction for retrapped air 22 2.6. Blank correction 25 2.7. Method validation and implications for future research 26 3. Results 28 3.1. N2O concentration during the past two millennia 28 3.2. Changes of N2O flux 30 3.3. Wavelet transform and spectral analysis 31 4. Discussion 32 4.1. Centennial N2O variations and solar irradiance change 32 4.2. Terrestrial source variations 33 4.2.1. Soil moisture content 34 4.2.2. Soil temperature 36 4.3. Oceanic source variations 36 5. Conclusion 39 References 41 List of Tables 54 List of Figures 59 Appendix 75 Abstract (In Korean) 82 Master
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