Carbon 14 Dating of Benthic Foraminifera and Intermediate to Deep Water Circulation in the Western Pacific

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Project title

Code/計畫編號

NSC97-2611-M019-001

Translated Name/計畫中文名

西太平洋底棲有孔蟲碳十四定年與中深層水循環

Project Coordinator/計畫主持人

Min-Te Chen

Funding Organization/主管機關

National Science and Technology Council

Department/Unit

Institute of Earth Sciences

Website

https://www.grb.gov.tw/search/planDetail?id=1677606

Year

2008

Start date/計畫起

01-08-2008

Expected Completion/計畫迄

01-07-2009

Bugetid/研究經費

2224千元

ResearchField/研究領域

海洋科學

"冰期時的大氣二氧化碳濃度顯著的低於間冰期，然而控制冰期與間冰期二氧化碳濃度變化的機制到目前為止仍未能充份了解。冰期時大氣二氧化碳濃度偏低的可能控制因素之一可能為通氣率低的深層水儲存了較多的碳，成為冰期大氣二氧化碳的”匯”，然而這方面的古海洋證據目前並不夠充份。本研究嘗試分析位於西太平洋中深層水深度的沖繩海槽、南海、與靠近巴布亞南邊緣海與所羅門海的赤道太平洋岩心，測量同岩心深度標本中的浮游與底棲有孔蟲的加速器碳十四年代並比較其差異，並藉由這定年資料重建西太平洋中深層水最近四萬年來的循環變化史。初步研究結果顯示沖繩海槽的表層水與中深層水的加速器碳十四年代差異在最近四萬年有顯著的變化，暗示這地區的中深層水可能是影響冰期與間冰期大氣二氧化碳濃度變化的”源”與”匯”之一。由於西太平洋盛行的季風系統，相當程度的決定了本地區冰期與間冰期的降雨量強度與分布，與表層水的鹽度與中深層水湧升流強度，本研究亦將利用浮游有孔蟲氧同位素與沉積物有機生物指標方法，估測海水表面鹽度與區域降雨量的變化，以進一步了解海水表面鹽度或密度變化是否為控制西太平洋中深層水在過去冰期與間冰期通氣率變化的重要因素。" "Atmospheric carbon dioxide concentrations were significantly lower during glacial periods than during interglacial periods, but the mechanisms responsible for this difference remain uncertain. The difference could be explained by greater carbon storage in a poorly ventilated deep ocean during glacial periods, but direct evidence regarding the ventilation and respired carbon content of the glacial deep ocean is sparse. Sediment cores collected from intermediate to deep water depths of the Okinawa Trough, South China Sea, and equatorial Pacific near southern Papua margins and Solomon Seas are proposed to be studied using coexisting planktic and benthic foraminifer AMS 14C measurements to reconstruct the history of intermediate to deep water depth circulation in the western Pacific of the past 40 kyr. The initial analysis from one Okinawa Trough core indicates significant variations of AMS 14C age differences between surface and intermediate to deep waters over the past 40 kyr, suggesting that this water mass is possibly a candidate of carbon source and sink that may affect atmospheric pCO2 in the past glacial to interglacial periods. As the western Pacific climate is more dominated by monsoon wind patterns that determine the intensity and distribution of regional precipitations, that in turn control the sea surface salinity (SSS) and also the strength of intermediate water upwelling in the sea, the proposed research here aims also SSS and regional rainfall reconstructions from the cores by planktic foraminifer isotope and organic biomarker methods, for better assessing how sea surface salinity or density may have played a role in ventilation changes in western Pacific intermediate to deep water during the past glacial and interglacial periods."

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Carbon 14 Dating of Benthic Foraminifera and Intermediate to Deep Water Circulation in the Western Pacific

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