| Summary: | 碩士 === 國立臺灣海洋大學 === 應用地球物理研究所 === 92 === Abstract
High-resolution records of planktic foraminifer, sea surface temperature (SST) and sea surface salinity (SSS) from an IMAGES core MD972146 (20°07.019N, 117°23.08E, water depth 1720m) provide information on centennial to millennial-scale paleoceanographic variations during the Holocene in the Northern South China Sea (SCS). This study was conducted based on census counting of planktic foraminnifer fauna assemblages of core MD972146. The fauna assemblages are dominated by seven species which constitute over 84.5% of total planktic foraminifer fauna compositions. These seven species are G. glutinata, N. dutertrei, P. obliquiloculata, G. calida, G. bulloids, G. ruber, and G. sacculifer. For estimating SST based on the fauna variations, this study used a 694 western Pacific coretop planktic foraminifer fauna data and applied the Modern Analogue Technique (MAT) and Revised Analog Method (RAM) to reconstruct the warm/cold season as well as annual average SST and SSS of MD972146. By comparing the estimation uncertainties of the MAT and RAM SSTs, the RAM shows better performance in estimating the SSTs than the MAT. This result suggests that the RAM could be a more useful tool in estimating western Pacific SST based on fauna records. The study results show that the centennial to millennial-scale Holocene SST and SSS records from MD972146 appear to be well-correlated to that of cosmic nuclide production rate of 10Be measured in GISP 2 ice core and that of 14C measured from tree-ring records, which are both interpreted to reflect variations in solar activities in the Holocene. This study also compares the MD972146 SST and SSS with a stalagmite oxygen isotope record from Dongge Cave. This study found that during the North Atlantic cold events in the Holocene, the northern SCS kept slightly colder (or stable) and wet climate. This climatic teleconnection patterns are similar to the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO) that are discovered in modern climate studies. The MD972146 Holocene SST record also presents evidence that correspond to Little Ice Age (LIA), Medieval Warm Period (MWP), and some Chinese historical climate events. Through a comparison of Uk37 SST and SSS derived from a SONNE core 17940 and those recorded in MD972146, this new study demonstrates that the record reconstructed provides more reliable Holocene sea surface hydrographic condition variations in the northern SCS. As the SCS climate was only slightly colder (or stable) and wet during the cold episodes of North Atlantic, this study suggests that global thermohaline circulation changes might play important roles in modulating global climate on the time scales during the Holocene.
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