碩士 / 國立臺灣海洋大學 / 應用地球科學研究所 / 105 / Sea surface temperature (SST) records from the subarctic Northwestern (NW) Pacific are ideal for reconstructing regional paleoceanographic changes sensitive to global climate change. In this study, used a core LV 63-41-2 (52.56˚ N, 160.00˚ E; water depth 1924 m) retrieved from a high sedimentation site, in which the interactions of the Bering Sea and the warm water mass from the NW Pacific are highly dynamic. I analyzed the alkenone of coccolithophorids secreted and preserved in the sediments of the core. Our results indicate that the alkenone concentrations are low prior to 16~27 ka BP, suggesting low productivity of coccolithophorids during the last glacial. High glacial C37:4 alkenone concentrations in the core imply large amount of fresh water influencing the surface water of the NW Pacific with a reaching to the Site LV 63-41-2. This study inferred that the low salinity water may be formed from the ice-melting water on site and/or brought by the surface current from the Bering Sea, and is efficient in producing strong water stratification condition. The stratification weakens vertical mixing of the upper water column, that in turn decreases the nutrients upwelled from deep to the surface therefores causes low productivity of coccolithophorids. The LV 63-41-2 alkenone-SST shows a gradual increase, associated with high C37:4 alkenone concentrations during the early Bølling-Allerød (B/A) period. It implies a weakened stratification and much stronger nutrient upwelling than the glacial. The late B/A period is characterized by an abrupt warming with possibly more melting sea ices in the Bering Sea and the coast near the Kamchatka Peninsula. The large amount of fresh water lens formed during the ice melting might have ceased vertical mixing and upwelling in the upper water column as evidenced by a decline of biological productivity of both calcerous and soliceous organism during late B/A. Based on the age model of LV 63-41-2, this study suggests an early warming and low productivity in the NW Pacific that is coincident with a rapid cooling in most of the Northern Hemisphere high latitudes during the Younger Dryas.
| Identifer | oai:union.ndltd.org:TW/105NTOU5135002 |
| Date | January 2016 |
| Creators | Liao, Chia-Ju, 廖佳汝 |
| Contributors | Chen, Min-Te, 陳明德 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 39 |
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