The Application of Organic Biomarkers to Reconstruct Ocean Temperature Changes in the Northeastern South China Sea over the Past 50,000 years (Western Pacific Core-Tops and MD103264)

• Main Authors: Li, Yi-Xian, 李奕賢
• Other Authors: Chen, Min-Te
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/mehms3

碩士 === 國立臺灣海洋大學 === 地球科學研究所 === 106 === The ocean surface current and climate changes in the South China Sea (SCS) are driven seasonally by East Asia Monsoon (EAM). Previous studies on Gulang loess profile have identified strong climate linkage at millennium-scale as documented in Greenland ice core and North Atlantic sediment records with the EAM. In this study, I used GDGTs produced by Thaumarchaeota to reconstruct ocean temperature variations of the past 50,000 years based on core MD103264 (21.54°N, 119.3°E, 2820m water depth) retrieved in the Marion Dufresne cruise for the northeastern SCS in year 2010. Furthermore, I also compiled 90 sediment core-tops data of Glycerol Dialkyl Glycerol Tetraethers (GDGTs) collected from the SCS, East China Sea (ECS) and Yellow Sea (YS), to assess the potential environmental factors that influence TEX86 index in the western Pacific. A redundancy analysis using the fractional abundance of four isoGDGTs, which are used for the TEX86 sea surface temperature (SST) proxy, indicates that the mean annual ocean temperature, water depth, and terrestrial input are main factors affecting the temperature reconstruction with the uses of TEX86 index. A multivariate regression analysis has been used to evaluate quantitatively how water depth and BIT index would bias TEX86-based temperature estimation. Comparing the MD103264 SSTs to Gulang mean grain size, a winter EAM strength proxy, indicated that ~1-3℃ decreases of TEXH86-estimated SSTs link to Heinrich event cooling, indicating abrupt increases in winter EAM strength. By calculating the differences between the MD103264 Uk’37-SST and TEXH86-T30-125 m, this result shows millennial-scale oscillations but relatively more stratified surface water during Marine Isotope Stage (MIS) 3, suggesting weaker winter EAM, and/or stronger summer EAM, or other factors.