Late Quaternary Climate Evolution of the Pacific Ocean(II)

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簡歷

基本資料

Project title

Code/計畫編號

MOST107-2116-M019-003

Translated Name/計畫中文名

晚第四紀太平洋氣候演化研究(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=12678158

Year

2018

Start date/計畫起

01-08-2018

Expected Completion/計畫迄

31-07-2019

Bugetid/研究經費

2155千元

ResearchField/研究領域

地球科學

晚第四紀南北半球高緯與熱帶海域氣候變化雖大致上表現出相同的軌道與千年時間尺度變化型態，但在變化的時間點與變化速率上有特徵性的差異。熱帶海域藉由海盆空間尺度環流與季風，及間熱帶輻合帶的南北遷移，往高緯輸送熱量與水氣以平衡高低緯與南北半球的氣候平衡，雖然可以解釋大部分的南北半球與熱帶氣候在軌道與千年時間尺度上的主要變化特徵，但無法充份解釋南北半球與熱帶氣候在在變化的時間點與變化速率的主要差異。某些假說認為南冰洋的快速氣候反應可經由東赤道太平洋，太平洋北赤道流分叉並以印度太平洋穿越流進入東印度洋，並以黑潮進入熱帶西太平洋與東海，將南半球高緯氣候變化的影響從南半球帶入北半球，形成一有效的”海洋隧道”與半球間與高低緯氣候連繫機制。本研究規畫對太平洋側之南大洋、東赤道太平洋、東印度洋、西菲律賓海與東海已取得的高沉積速率與高解析度採樣岩心，分析有機生物標幟物異戊二烯為單元所組成的甘油二甲基甘油四醚酯（TEX86）的次表層水/中層水溫度，作為指示海洋熱含量變化的代用指標；此外，另將以可見光-近紅外光光譜（VNIR RDS）所反映的特徵超微量黏土礦物組成，作為追蹤海流流徑與強度變化的代用指標。本研究除應用上述兩種創新型古海洋代用指標並配合現代海域分層海水採樣航次進行驗證外，並將輔以碳氧穩定素、碳酸鹽、蛋白石、總有機碳含量等背景古海洋資料與密集加速器碳14定年控制，重建上述海域的晚第四紀古氣候時間序列紀錄並分析在主要變化週期的相干性與相位關係，以期深入瞭解太平洋南北半球與熱帶海域在軌道（歲差與半歲差週期）與千年時間尺度的時序關係，與變化的時間點與變化速率的差異及其控制機制。本研究有助鑑識出重要的氣候控制作用並提出新的假說供後續研究檢驗，並從而能了解長期自然氣候變化的規律及可能對人類社會的潛在衝擊。 Past glacial to interglacial and millennial-scale climate changes in the late Quaternary have been found as expressing a dominant but nearly similar pattern in the high-latitude Northern Hemisphere (NH) and Southern Hemisphere (SH), though characteristic subtle different timing and rate of changes have been also observed extensively. More importantly, late Quaternary tropical ocean and climate that are strongly impacted by monsoonal winds and Intertropical Convergence Zone (ITCZ) migrations appear to be interacted with effects from both NH and SH. In principle, exchange of energy and mass between the high and low latitude ocean and the atmosphere is an essential component for driving the inter-hemispheric climate changes, though the processes fail to explain the different timing and rate of changes in the responses of both NH and SH climates. Few hypotheses exist for explaining the interhemispheric linkage and differences in timing and rate of changes, such as that a hypothetical response to orbital forcing (obliquity, precession) in the southern subtropical ocean or in the Southern Ocean propagates intermediate to subsurface water signals by passing the Eastern Equatorial Pacific (EEP) and bifurcates further into the Indo-Pacific Oceans by throughflow or Kuroshio (an “Oceanic Tunnel”). Here we compile a suite of high quality cores from the Pacific sector of the Southern Ocean, EEP, Eastern Indian Ocean, Western Philippine Sea, and East China Sea (ECS), and propose to generate a novel subsurface temperature organic biomarker TEX86 and VNIR Reflectance Derivative Spectroscopy (RDS) signatures that are useful for detecting and changes in Ocean Heat Content (OHT) and for indicating the changes in the path and strength of currents, respectively, to observed climate linkages between NH and SH and tropical oceans and any possible links of cross-equatorial transport of heat and moisture. This project focuses on precise age dating on key paleoclimatic time series, and based on which, to identify important processes and propose or refine hypothesis of controlling mechanism responsible for the inter-hemispheric climate linkage in the Pacific. The expected achievements of these studies are to (1) reconstruct the paleoclimatic variability in the late Quaternary based on existing and new marine sediment cores by generating novel, subsurface or intermediate water temperature dependent proxies of organic biomarker TEX86, and current path and strength-indicative color RDS proxies of clay mineral assemblages (such as smectite), along with other conventional paleoceanographic proxies of stable isotope (13CB-P, 18OB-P, organic carbon, carbonate, and opal etc.), (2) compare time series data regionally on time and frequency domain by the uses of cross-spectral analysis with a focus on the coherency and phasing relationships of precession, semi-precession, and millennial cycles to identify any possible linkage of inter-hemispheres and of high- and low-latitudes, (3) place the paleoclimatic records into a global perspective and test new hypotheses concerning the roles the external and internal forcing that have controlled the variability, which further our understanding on what lessons are to be learned from the paleoceanographic records about climate and ocean dynamics for the early 21st century, with potential impacts on humanity.

Keyword(s)

古海洋學
古氣候學
太平洋
晚第四紀
Paleoceanography
Paleoclimate
Pacific Ocean
Late Quaternary

DSpace CRIS

Late Quaternary Climate Evolution of the Pacific Ocean(II)

基本資料

Description