IMAGES II-IMPRESS: SST and SSS Variations in the Northern South China Sea over the Last 2000 Years (II)

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Project title

Code/計畫編號

MOST104-2611-M019-016

Translated Name/計畫中文名

IMAGES II-IMPRESS：南海北部近兩千年來的海表溫鹽變化(Ⅱ)

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=11574355

Year

2015

Start date/計畫起

01-08-2015

Expected Completion/計畫迄

01-07-2016

Bugetid/研究經費

1408千元

ResearchField/研究領域

海洋科學

"東亞與台灣是人口密集的區域，其氣候主要是受到亞洲季風（AM）的影響。然而目前我們對亞洲季風氣候對全球氣候變遷和漸增的人類活動衝擊的反應仍不瞭解，對亞洲季風的長期自然變化的控制因素了解仍很有限。印度太平洋的海水表面溫度及水文（如鹽度等）的改變，在過去研究中被認為係對季風強度有直接的影響，然而最近較新的研究結果發現在過去2000 年以來，印度太平洋地區和東亞地區的海水表面溫度與水文變化呈現出相反的變化。有鑑於此，赤道西太平洋與南海過去2000 年以來的水文及溫度的變化有需要更廣的空間分布與高解析度的古氣候重建，使我們對已提出的長期季風動力變化機制可做再評估。本計畫將使用2012 年德國太陽號於南海北部陸棚區航次取得的沉積物岩心，重建南海過去2000 年以來高解析度（約5-10 年）的海表溫及海表鹽度變化。海表鹽度的估測係利用浮游有孔蟲氧同位素扣除掉海表溫度的影響後建立；而海表溫度的估測將利用烯酮類不飽和指標（UK’ 37）及四醚膜類酯物指標（TEX86）等兩種代用指標。本研究預期結果將可解決下列幾個重要科學問題：如過去2000 年來南海北部海表溫改變的輻度、海表鹽度變化如何反應區域氣候（如溫度等）；區域海表鹽度的改變是否有空間上的不同；南海北部海表鹽度的改變與印度太平洋地區或亞洲季風區域的變化有何與為何不同等。本研究將建立過去2000 年印度太平洋與東亞地區水文的空間與時間變化型態並探討其機制。" "The East Asia including Taiwan is a very densely populated region. The climate in this region is mainly influenced by the Asian monsoon (AM). Currently, how the regional climate will respond to changing global climate and increasing human activities still remains largely elusive. Indeed, our understanding of natural variability of AM is still limited. It is widely believed that changes in the sea surface temperature (SST) and hydrologic conditions (i.e. SSS) in the Indo-Pacific region would directly influence the monsoon intensity. However, new studies find that hydrological changes in the Indo-Pacific region are opposite to those in East Asia over the last 2000 years, which poses a serious challenge to the long-time conventional view. Currently, hydrological and temperature changes in the tropical Western Pacific over the last 2000 years are still poorly understood, large due to the lack of spatially-distributed, high-resolution paleoclimatic reconstructions from this region, especially in the South China Sea (SCS). This hinders our ability to assess/re-assess the proposed mechanisms of monsoon dynamics. Here, I propose to reconstruct ~2000-year-long, high-resolution (5-10 years) SST and SSS changes in the SCS. I will use sediment cores, spreading between 23°N and 5°N in northern SCS shelves, which had been already retrieved with success during the 2012 SONNE cruise. SSS reconstructions will be based on SST proxies alkenone unsaturation index (UK’ 37) and tetraether index TEX86 SSTs that could be subtracted from oxygen isotopes of planktonic foraminifers. Quantitative SST changes will be reconstructed using the two SST proxies UK’ 37 and/or TEX86. Key issues we will address are: What is the amplitude of surface temperature changes in the northern SCS over the last 2000 years? How did local salinity changes respond to climatic changes (i.e. temperature)? Were salinity changes in these locations spatially different? Did salinity changes in the northern South China Sea follow the changes in the Indo-Pacific region or the AM region? Can we assemble a big picture of how hydrological changes occurred in the regions between East Asia and Indo-Pacific over the last 2000 years?"

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IMAGES II-IMPRESS: SST and SSS Variations in the Northern South China Sea over the Last 2000 Years (II)

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