2021-01-012024-05-18https://scholars.lib.ntu.edu.tw/handle/123456789/701037摘要：平衡氣候敏感度被定義為大氣二氧化碳濃度倍增時全球平均增溫的程度，而(強韌的)估計熱帶地區上次冰盛期地表冷卻是約制平衡氣候敏感度的要件。然而，儘管熱帶地區的海洋上層在上次冰盛期冷卻的重建對了解氣候變化十分重要，其重建在程度和空間形態上仍有著不確定性。本研究的目標在探討此一議題，將藉由增加上次冰盛期冷卻估計之重建的空間涵蓋度，以及擴充此重建之垂直涵蓋度至海水次表層，尤其海水次表層進行的作用可能影響海表的溫度分佈。本研究估計冷卻的關鍵手段是運用多重指標，包括有孔蟲的鎂鈣比與叢（團簇）同位素、長鏈烯酮類不飽指標UK`37和古菌脂質TEX86等。由於各種指標各有其優缺點，運用多重指標可以讓我們擷取各種指標之強有力的優勢來約制其他指標的不確定性，並且增進對於這些地球化學指標的闡述和機制了解，就結果而言可整體看來產生更為強韌的熱帶地區上次冰盛期冷卻重建。根據更多定量的地球化學指標分析，本研究的最終產物將是現有的上次冰盛期冷卻圖之增強版。不同於過去的冷卻圖只專注於海表，新建立的冷卻圖將包含次表層的冷卻估計，提供不同面向之熱帶海洋上次冰盛期的訊息。終極而言，這個資料庫將有用於證實目前用於推斷未來氣候變化的數值模型。<br> Abstract: A robust estimate of the magnitude of Last Glacial Maximum (LGM) surface cooling in the tropics is key to constrain the equilibrium climate sensitivity, which is defined as the extent of global mean warming following a doubling of atmospheric CO2. However, in spite of its importance for understanding climate change, the reconstruction of tropical LGM cooling in the upper ocean remains uncertain in terms of its magnitude and spatial patterns. The proposed research aims to address these issues by increasing the spatial coverage of reconstructed LGM cooling estimates, as well as extending the vertical coverage of the reconstruction to include shallow subsurface, where the oceanic processes may influence the temperature distribution at the sea surface. A key approach in the proposed research is to generate cooling estimates based on multiple proxies, namely foraminifera-based Mg/Ca and clumped isotope, alkenone-based UK`37, and archaeal tetraether-based TEX86. As all proxies have their own pros and cons, this approach allows us to take advantage of the strengths of proxies to constrain the uncertainty of the others, thereby improving the interpretation and mechanistic understanding of these geochemical proxies, which in turn results in a more robust tropical LGM cooling reconstruction as a whole. The end product of the proposed research will be an improved version of the existing LGM cooling map as it is based on more quantitative geochemical proxies. Unlike previous cooling maps which focus only on the sea surface, this map will also include subsurface cooling estimates, offering another piece of information on the tropical LGM ocean. Ultimately, this database will be useful for validating the current generation of numerical models used to project future climate change.上次冰盛期古溫度重建多重指標長鏈烯酮類不飽指標UK`37有孔蟲鎂鈣比有孔蟲叢同位素古菌脂質TEX86Last Glacial Maximumpaleotemperature reconstructionmultiproxyalkenone unsaturation index UK`37foraminifera Mg/Caforaminifera clumped isotopearchaeal lipid TEX86