本文選題：亞馬遜沖積扇海域 + 快速氣候變化��； 參考：《中國科學(xué)院研究生院(海洋研究所)》2015年碩士論文

【摘要】：亞馬遜盆地是世界最大的陸地大氣對流中心,以及熱帶地區(qū)熱量來源的主要區(qū)域,亞馬遜盆地對流降雨在向高緯地區(qū)輸送熱量過程中起了關(guān)鍵作用,調(diào)控著全球環(huán)境氣候變化,成為古氣候與古環(huán)境研究的熱點(diǎn)地區(qū)。亞馬遜沖積扇海域處于西熱帶大西洋水團(tuán)影響之下,該水團(tuán)對大洋動力過程和洋內(nèi)熱量轉(zhuǎn)移相當(dāng)重要,亞馬遜流域淡水輸入的變化不僅對該水團(tuán)的特征有重要影響,更控制著大西洋跨赤道環(huán)流-北巴西沿岸流的變異,從而調(diào)節(jié)著全球溫鹽環(huán)流。ODP942站毗鄰亞馬遜河口,得益于亞馬遜河大量沉積物的輸入,其巖芯樣品是區(qū)域氣候和海洋環(huán)境高分辨率重建的良好材料。本文利用亞馬遜沖積扇海域ODP942站位海洋沉積巖芯中浮游有孔蟲Globigerinoides ruber殼體氧同位素(δ18O)、Mg/Ca比值以及Ba/Ca比值記錄重建了4萬年以來亞馬遜盆地千年尺度的水文氣候變化,討論了其環(huán)境變遷與ITCZ位置遷移和大洋溫鹽環(huán)流之間的關(guān)系。研究表明表層海水溶解Ba濃度與表層海水鹽度(SSS)之間存在顯著的負(fù)相關(guān)關(guān)系(R2=0.95),依據(jù)亞馬遜河口區(qū)域現(xiàn)代海水Ba與SSS的相關(guān)關(guān)系以及Ba在海水和有孔蟲殼體之間的分配比例建立了一個區(qū)域浮游有孔蟲Ba/Ca比值與SSS的回歸公式:SSS=-6.2005*Ba/Ca foram+40.724(R2=0.98)。根據(jù)942站位G.ruber(White)和G.sacculifer殼體Ba/Ca測試值計算的近4100 a B.P.來的SSS變化顯示:與G.sacculifer相比,利用G.ruber(White)Ba/Ca比值估計的SSS變化與熱帶南美石筍δ18O指示的降水記錄有良好的可比性,G.ruber(White)Ba/Ca比值是亞馬遜沖積扇海域SSS良好的替代指標(biāo),為進(jìn)一步通過G.ruber(White)殼體Ba/Ca比值恢復(fù)區(qū)域淡水輸入及降水變化奠定了基礎(chǔ)。亞馬遜沖積扇海域有孔蟲殼體氧同位素記錄了4萬年以來北半球高緯地區(qū)的快速氣候變化事件,分別為Heinrich事件的H1-H4、Dansgaard-Oeschger(D-O)旋回1-8及Younger Dryas(YD)事件,Heinrich及YD冷事件期間,G.ruber殼體δ18O值變大;D-O暖期,δ18O值變小。通過有孔蟲殼體Mg/Ca比值重建的表層海水溫度(SST)對北半球高緯地區(qū)快速氣候變化響應(yīng)較弱,但是與南極冰芯記錄的古氣候變化趨勢較為一致,尤其是顯示出末次冰消期以來表層海水溫度的持續(xù)增加。通過海水氧同位素值(δ18Osw)記錄的表層海水鹽度顯示在Heinrich事件H1-H3及YD事件期間SSS較高。SST變化趨勢顯示亞馬遜沖積扇海域表層海水溫度變化與南極氣候變化更為密切,說明了亞馬遜沖積扇海域記錄的千年尺度的快速氣候變化事件主要反映在降雨模式的變化。Heinrich、YD事件期間,大西洋經(jīng)向翻轉(zhuǎn)環(huán)流(AMOC)減弱,氣候變冷,ITCZ向南移動,使亞馬遜沖積扇海域降雨減少。通過對比,亞馬遜沖積扇海域降雨模式變化與深部熱帶大西洋變化同步,說明了熱帶地區(qū)降雨模式變化與大洋溫鹽環(huán)流的改組之間的聯(lián)系,北大西洋表層海水溫度變化、北大西洋經(jīng)向溫度梯度變化及ITCZ的南北遷移,使得該區(qū)域降雨模式發(fā)生改變。
[Abstract]:Amazon basin is the largest terrestrial convection center in the world and the main area of heat sources in the tropical region. The Amazon basin has played a key role in transporting heat from the high latitude area in the Amazon basin. It regulates the global environmental climate change and becomes a hot spot in the study of paleoclimate and paleoenvironment. Under the influence of the the Atlantic water mass in the Western tropics, the water mass is very important to the ocean dynamic process and the intra ocean heat transfer. The change of the freshwater input in the Amazon basin not only has an important influence on the characteristics of the water mass, but also controls the variation of the cross equatorial circulation in the north of the Atlantic and the northern Brazil coastal flow, thus regulating the adjacent.ODP942 station adjacent to the global temperature and salt circulation. The Amazon estuary, benefited from the input of a large amount of sediment in the Amazon River, is a good material for high resolution reconstruction of regional climate and marine environment. This paper uses the oxygen isotope of planktonic foraminifera Globigerinoides ruber (delta), Mg/Ca ratio and Ba/Ca ratio in the marine sedimentary core of the Amazon alluvial fan ODP942. The value records rebuilt the hydrological climate changes of the Millennium scale in the Amazon basin for 40 thousand years, and discussed the relationship between the environmental changes and the ITCZ position migration and the ocean temperature and salt circulation. The study shows that there is a significant negative correlation between the dissolved Ba concentration in the surface sea water and the salinity of the surface sea water (SSS), which is based on the Amazon estuary area. The correlation between Ba and SSS in modern sea water and the distribution ratio of Ba between sea water and foraminifera shell set up a regression formula for the Ba/Ca ratio of planktonic foraminifera and SSS: SSS=-6.2005*Ba/Ca foram+40.724 (R2=0.98). According to the 942 stations G.ruber (White) and G.sacculifer shell Ba/Ca test values Compared with G.sacculifer, the SSS changes estimated by the G.ruber (White) Ba/Ca ratio have a good comparability with the precipitation records indicated by tropical South American stalagmite Delta 18O. The G.ruber (White) Ba/Ca ratio is a good substitute for SSS in the Amazon alluvial fan sea area, and is to further restore the region fresh water transport through the G.ruber (White) shell ratio. The oxygen isotope of the foraminifera shell in the Amazon alluvial fan area has recorded the rapid climate change events in the high latitude region of the northern hemisphere for 40 thousand years, respectively, for the H1-H4, Dansgaard-Oeschger (D-O) cycle 1-8 and Younger Dryas (YD) events of the Heinrich event, the 18O value of the G.ruber shell Delta during the Heinrich and YD cold events. In the warm period of D-O, the value of delta 18O becomes smaller. The surface seawater temperature (SST) rebuilt by the Mg/Ca ratio of the foraminifera shell is weak in response to the rapid climate change in the high latitude region of the northern hemisphere, but the trend of palaeoclimate change recorded in the Antarctic ice core is more consistent, especially in the surface sea surface temperature increasing since the last glacial period. The salinity of the surface sea water recorded by the oxygen isotope value (delta 18Osw) shows that the higher.SST trend of SSS during the events of the Heinrich event H1-H3 and YD shows that the temperature changes in the surface water temperature of the Amazon alluvial fan are more closely related to the changes in the Antarctic climate, which indicates that the rapid climate change events of the Millennium scale recorded in the Amazon alluvial fan are the main events. It is reflected in the variation of the rainfall pattern.Heinrich, the YD event, the the Atlantic meridional circulation (AMOC) weakened, the climate became cold, and the ITCZ moved southward to reduce the rainfall in the Amazon alluvial fan. By contrast, the rainfall patterns in the Amazon alluvial fan were synchronized with the changes in the deep tropical the Atlantic, indicating the variation of rainfall patterns in the tropics and the changes in the rainfall patterns in the tropical regions. The relationship between the change of the ocean temperature and salt circulation, the change of surface sea temperature in the North Atlantic, the change of the North Atlantic meridional temperature gradient and the migration of the north and south of ITCZ make the rainfall pattern change in this region.
【學(xué)位授予單位】：中國科學(xué)院研究生院(海洋研究所)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P532

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