2023-01-012024-05-18https://scholars.lib.ntu.edu.tw/handle/123456789/700133海洋近100年來的流動與循環，可以利用在1950年代於太平洋赤道區域進行的核子試爆所產生的大量人造核種（如鈾-236與碳-14），隨著海流傳送到其他海域的時間與豐度變化來追蹤。本研究團隊在上一期的深耕計畫補助下，發展了一套於臺大分析超低豐度鈾-236的方法。應用在重建南灣珊瑚岩芯中的鈾-236豐度變動，加上配合碳-14豐度變化來探討赤道太平洋海流的傳送速度與黑潮水侵入北呂宋海峽的幅度與頻率。接續過去的研究成果，我們將會重建從1950年來蘭嶼、菲律賓西部海域以及位於北赤道洋流上的三根珊瑚岩心中化學示蹤劑的記錄，探討北赤道洋流與黑潮的淨流速與變動情形。 The surface ocean circulations in the recent decade can be studied with anthropogenic nuclear-test-derived chemical tracers, including 236U and 14C. With the support from the Phase-1 fund, our group is the first to combine the two distinct tracers in the reconstruction of the paleo ocean current. Our results confirm that the 236U is a much more sensitive ocean tracer than the 14C and can provide a comprehensive view of the ocean seawater transportation and mixing in the Pacific Ocean. To explore the upstream of the Kuroshio, including the North Equatorial Current (NEC), we aim to apply the developed 236U and 14C tracer techniques on three new coral cores. These currents bring heat and support the biomes (fisheries) along the Philippines, Taiwan, and Japan. Understanding their past and modern variations is extremely important to the ecology and economy. The 236U and 14C tracers are in very low abundance. Analytical power becomes crucial to using chemical ocean tracers for circulation study. Only a few labs are capable of such challenging analyses. At NTU, we have the instrument and technique available to determine atomic 236U/238U ratios in samples with only femtograms of 236U using a secondary electron multiplier (SEM) on a multi-collector high-resolution inductively coupled plasma mass spectrometer (MC-ICPMS) (Lin et al., 2021). We will continue our collaboration with the University of Tokyo for the 14C analysis using an accelerator mass spectrometry (AMS). Lin, H.-T., Chiang, H.-W., Yu, T.-L., Christl, M., Liu, J., DeLong, K. and Shen, C.-C. (2021) 236U/238U Analysis of Femtograms of 236U by MC-ICPMS. Anal. Chem. 93, 8442−8449.鈾-236; 碳-14; 珊瑚; 海水循環; 化學示蹤劑;236U; 14C; coral; ocean circulation; chemical tracers