Sst and Sss Variability and Their Control Mechanisms over the Past 2000 Years in the Western Pacific Marginal Seas (Ii)

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Project title

Code/計畫編號

MOST106-2611-M019-013

Translated Name/計畫中文名

西太平洋邊緣海近兩千年來的海表溫鹽變化與機制 (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=12229434

Year

2017

Start date/計畫起

01-08-2017

Expected Completion/計畫迄

01-07-2018

Bugetid/研究經費

1126千元

ResearchField/研究領域

海洋科學

"分辨自然調控與人為活動所造成的氣候變化的幅度與頻率為瞭解本世紀末與未來數百年氣候變化的重要基礎。本世紀末之前大氣溫室氣體濃度的快速增加及其產生的溫室效應，勢必帶來冰原快速融化與海水體積的熱膨脹，隨之造成的後果是全球海水面的快速上升與極端氣候的加劇，將對全球與區域的人類生活環境造成衝擊。有鑑於此，自然與人為活動影響情況下的百年至年代際氣候變化的幅度與頻率為預測與提前因應與適應本世紀末及之後環境變遷的重要基礎資訊。本計畫將利用西太平洋邊緣海–東海、閩浙沿岸、南海、印度太平洋暖池區等高沉積速率（>2-3 公分/年）的大陸棚區泥質沉積物岩心，針對過去2000 年曾發生的全球氣候變化事件–小冰期（約西元1300-1900 年）與中世紀大暖期（約西元1000-1300 年）在西太平洋邊緣海所表現或反應的海表水文、海表溫鹽度、陸地降雨量變化進行古氣候重建，以評估在西太平洋區域過去2000 年百年至年代際氣候變化的動力與機制。本計畫將進行海表溫鹽度的估測–利用浮游有孔蟲氧同位素扣除掉海表溫度的影響後估測鹽度；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）等兩種在本人實驗室已完善建立的代用指標；鄰近陸地降雨量變化將利用沉積物岩心的陸源物質通量估測。本計畫第一年（2016-2017）已完成閩浙/東海陸棚岩心的海表溫重建並發展創新連續疊加誤差分析以量化表現重建海表溫的誤差，並比較區域海域與亞洲季風在同時段的變化。本計畫第二年（2017-2018）將延伸對比東海北部陸棚泥質區、南海/印度太平洋暖池區的海表溫紀錄。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 年在小冰期與中世紀大暖期在西太平洋邊緣海的海表溫改變的輻度與時間點是否與西太平洋開放性海域或全球有所不同？本區域的海表鹽度變化如何反應全球的小冰期與中世紀大暖期氣候事件？本區域海表溫鹽度與次表層水（~150m）溫度的改變在這些氣候事件上是否有不同的空間分布？本研究以海洋沉積物岩心為基礎重建過去2000 年以來西太平洋與東亞的區域水文的空間與時間變化型態並探討其機制。" "How to estimate the the impacts associated with drastic future climate change beyond this century under significant anthropogenic impacts is important issue to geo-science and ocean science community from regionally to globally. The issue is important as the seemingly accelerated increases of greenhouse gases in the atmosphere may bring rapid melting of ice sheets and thermal expansion of sea water which would accelerate the rate of global sea level. The rapid sea level rise will also exaggerate the climate impacts associated extreme climate variability. Understanding the rate of climate change requires deep understanding on natural centennial – multi-decadal climate changes, which have happened quasi-periodically in the past 2000 years. Here I propose to take advantage of a unique natural window for probing the past centennial to possibly multi-decadal climatic events, the Little Ice Age (LIA, ~1300-1900AD) and Medieval Warm Period (MWP, AD1000-1300) by the uses of ultra-high sedimentation rate (>2-3cm/yr) mud shelf sedimentary cores from the East China Sea (ECS), Min-Zhe (MZ), and South China Sea (SCS). The centennial to multi-decadal climate reconstructions proposed here include sea surface temperature (SST), salinity (SSS), and terrestrial flux input from nearby large rivers which indicate land precipitation and circulation changes in response to the events in the western Pacific marginal seas. All records will be subjected to high-resolution AMS 14C and Th/U dated to give precise chronology with known uncertainties. All the climate reconstructions for the western Pacific marginal seas of the past 2000 years will provide important constraint on further understanding climate evolution beyond this century and beyond. The 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 that are already well-established in my lab. The 1st year project (2016-2017) has accomplished multiple proxies of SST analysis based on a high sedimentation rate core taken from Min-Zhe/ECS shelf and based on that, we have developed a novel approach of continuous superposition error (CSE) analysis to better quantify the possible uncertainty of the SST records through time that constraint our interpretation. We have also done regional syntheses on marine SST records in the western Pacific with a comparison to Asian Monsoon records from both terrestrial and oceanic setting. The 2nd year (2017-2018) objectives will be placed to analyzing Northern ECS shelf mud drifts, and SCS/Indo-Pacific warm pool cores for developing a more spatial coverage of SST reconstruction. Key issues we will address are: What is the amplitude and timing of surface temperature and salinity changes during the LIA and MWP in the western Pacific marginal seas during 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 temperature at subsurface depth (~150m) have behaved differently from the surface? Did salinity changes in the western Pacific marginal seas follow the changes in the Indo-Pacific open oceans? 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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Sst and Sss Variability and Their Control Mechanisms over the Past 2000 Years in the Western Pacific Marginal Seas (Ii)

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