The Mechanisms of Hydrographic Changes Linking with Mega-Droughts and Floods in the Western Pacific Marginal Seas and East Asia of the Common Era (III)

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Project title

Code/計畫編號

MOST109-2611-M019-011

Translated Name/計畫中文名

西太平洋邊緣海近兩千年來的水文與東亞大洪旱變化的連繫與機制(Ⅲ)

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=13535087

Year

2020

Start date/計畫起

01-08-2020

Expected Completion/計畫迄

30-10-2021

Bugetid/研究經費

782千元

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。本計畫為延續型計畫，將繼續研究西太平洋邊緣海–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年至早全新世曾發生的千年至年代際全球氣候變化事件–小冰期（約西元1300-1900年）與中世紀大暖期（約西元1000-1300年）等在西太平洋邊緣海所表現的海表水文、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年至早全新世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沉積物粒徑與生物有機標幟物通量估測。本計畫前期研究已完成閩浙/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與長江流域降雨量的關聯；並完成南海高解析度海表溫重建與太陽亮度與火山噴發活動的連繫，顯示本區域在近2000年至早全新世氣候變化的複雜性與區域重建的必要性。本計畫（2020-2021）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鹽紀錄，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年以來至早全新世西太平洋與東亞的區域水文與洪旱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 an 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 time-scale climate changes, which have happened quasi-periodically in the past 2000 years to the early Holocene. Here I based on previous results, continue to study an unique natural climate archives 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 western Pacific marginal seas (Indo-Pacific Warm Pool, South China Sea, Min-Zhe and East China Sea). The centennial to multi-decadal climate reconstructions proposed here include sea surface temperature (SST), salinity (SSS), and terrestrial grain size and flux input from nearby large rivers which indicate changes in land precipitation and convection/monsoon changes in response to the events. The climate reconstructions of the past 2000 years back to early Holocene will provide important constraint on further understanding climate evolution beyond this century. 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. The SST proxies UK’37 and/or TEX86 that are already well-established and continuously improved and verified by more sea-going observations and sample collections. With these we are able to do more regional syntheses on marine records sensitive to terrestrial and oceanic climate, and aims to better developing a more spatial coverage of climatic reconstruction at centennial to multi-decadal time scales. Indications such as the linkages between the subsurface ocean temperature in Min-Zhe coastal zone and land precipitation on Yangtze River drainage, and between the SSTs in the South China Sea and MWP, LIA, and changes in the total solar irradiance and volcanic eruptions have been addressed in my previous studies. Key issues remain to solve 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 in East Asia and Indo-Pacific over the last 2000 years and their linkages with changes in total solar irradiance and volcanic eruptions?

Keyword(s)

古海洋學
古氣候學
西太平洋
水文學
全新世
Paleoceanography
Paleoclimate
Western Pacific
Hydrography
Holocene

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The Mechanisms of Hydrographic Changes Linking with Mega-Droughts and Floods in the Western Pacific Marginal Seas and East Asia of the Common Era (III)

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