南海沉積物收集器有孔虫殼體Mg/Ca 海表溫度方程式校正及Mg/Ca 溫度計之探討

• Main Authors: 游鎮烽, 謝英宗
• Other Authors: 地球科學系
• Format: Report
• Language: Chinese; English
• Published: 2004
• Subjects: 沈積物收集器; 殼體微量元素比; Mg/Ca溫度方程式; 部分溶解效應; Sediment trap; Trace element ratio; Mg/CaSST equation; Partial dissolution; Planktonic foraminifera
• Online Access: http://ir.lib.ncku.edu.tw/handle/987654321/55214; http://ir.lib.ncku.edu.tw/bitstream/987654321/55214/1/2010400503006.pdf

計畫編號:NSC93-2611-M006-002 執行機構:成功大學地球科學系（所） 研究期間:2004-08~2005-07 有孔蟲殼體微量元素比與同位素組成是目前重建古海洋水文特性研究中最重要的環境代用指標。近期國際上更應用單一碳酸鈣殼體Mg/Ca 及δ18O 記錄，估算古海水鹽度變化，以探討冰期-間冰期時所發生的短時間劇烈氣候擺盪（如：Super-ENSO, Heinrich events, D-O events）與氣候變遷之啟動，並研究其影響範圍、機制及時間尺度。殼體微量元素比雖已廣泛應用至古海洋變遷研究，但只有少數相關文獻曾對其與海水物理或化學特性直接進行校正，以驗證其所蘊含的環境意義。本研究初步選擇南海北部沈積物收集器中三種現生浮游性有孔蟲（G. ruber, G. sacculifer, N.dutertrei，分別生活於混合層及斜溫層，大小固定在250-350μm），經過微量元素清洗步驟處理後，以高解析感應耦合電漿質譜儀精確分析殼體微量元素比。初步結果顯示：（1）南海三個優勢浮游種屬之殼體Mg/Ca 比的差異主要反映各種屬棲息深度之不同；（2）有孔蟲殼體Mg/Ca 比與氧同位素值呈現良好的季節性變化，顯示殼體Mg/Ca 比主要受控於溫度效應；（3）南海地區Mg/Ca 溫度方程式為：Mg/Ca = 0.31 exp (0.090*T), r=0.81，冬季時，殼體Mg/Ca 明顯受到溶解效應所影響，可造成約2-3°C 的溫度誤差；而夏季則較不顯著。 Foraminiferal shell chemistry and isotopic composition are important proxies for reconstructing the oceanic hydrological properties in the past. Paired Mg/Ca and δ18O measurements on single foraminiferal species are of great merit in estimating both temperature and δ18O in seawater. Moreover, these results can also be applied for conferring violently climatic oscillation (e.g. super-ENSO, Heinrich events and D-O events) and the trigger of global climate change. However, only a paucity of data is available for the purpose of direct calibration between seawater and foraminiferal shells compositions. Several species (mixed layer- and thermoclinedwelling) of planktonic foraminifera (250-350μm) obtained from sediment traps near the central basin of the SCS were hand picked and cleaned thoroughly for trace element/calcium ratios determination using a HR-ICP-MS. The preliminary results indicate: (1) The differences of average shell Mg/Ca ratios among three dominant planktonic species reflect different water depths of calcification; (2) Strong intra-annual (seasonal) variations were observed both in sediment -trapped Mg/Ca and δ18O, indicating incorporation of Mg into shell is mainly temperature-controlled; (3) Mg/Ca-derived SST equation for all species in the SCS can be described by: Mg/Ca=0.31 exp (0.090*T), r= 0.81, and partial dissolutions at various depths possibly play a significant role to bias Mg/Ca ratios in foraminiferal calcites during winter periods, possibly due to chemical characteristics of local water masses.