末次盛冰期以来南海深水底流模态演变切换机制及其气候指示意义

Switches of the circulation modes of deepwater currents are in coincidence with global major climate transition and tipping points. The history of circulation modes of deepwater currents in the Pacific Ocean were unclear, which inhibit the understanding of the climate forcing mechanism. The South China Sea is the largest marginal sea in the Western Pacific Ocean, the deepwater of which originates from the intrusion of Pacific deepwater. Exploring the modes and modes transition mechanism of the South China Sea deepwater current, thus, will enhance our understanding of the climate forcing mechanism of Pacific region and even globe. This study will reconstruct multi-dimensions deepwater circulation information, including orientation, intensity and water mass property of three sediment cores retrieved from deepwater mass range of the Northeastern South China Sea by using paleomagnetic methods, XRF high-resolution scanning and Nd isotopic constraints on leaches of the Fe-Mn oxide of sediments. Based on above clues, we could clearly determine the circulation modes of the deepwater current of the South China Sea and their transitional times. Combined with new statistical methods and paleoclimatic modeling (COSMOS), we could further explore the evolutionary processes and transitional mechanism of circulation modes, and its spatial correlation and dynamic coupling with deepwater currents in the Pacific, Antarctic and Atlantic Oceans, determining its relationship with global climate change, extreme climate and climate tipping points. Our research will be greatly important toward a better understanding of the climate forcing mechanism and future climate prediction under global warming scenario.

海洋深水底流模态切换对应全球气候重大转折和临界点。太平洋地区深水底流模态演化不清晰，导致对气候驱动机制认识存在偏颇和争议。南海是西北太平洋最大边缘海，其深水底流源于太平洋深水底流的入侵，研究和揭示其模态和模态间切换机制可深化太平洋甚至全球气候驱动机制认识。本项目拟分析南海东北部陆坡区深水底流分布海域不同深度三个沉积物柱状样磁学性质、高分辨率主微量元素记录、沉积物自生相铁锰氧化物的钕同位素，重建不同深度深水底流强度、方向和水团性质等多维属性，区分和确定深水底流模态和模态切换时间，结合新颖数理统计方法和古气候模拟，确定深水底流模态演化过程和切换机制，揭示南海深水底流模态与太平洋、南大洋和大西洋深水底流模态间的空间相关性、动态耦合性，确定深水底流模态切换与全球气候变化、极端气候和气候临界点之间的联系，为全球气候变暖大背景下气候预测、气候驱动机制研究提供理论依据。

海洋深水底流模态切换对应全球气候重大转折和临界点。太平洋地区深水底流模态演化不清晰，导致对气候驱动机制认识存在偏颇和争议。研究和揭示深水底流模态和模态间切换机制可深化太平洋甚至全球气候驱动机制认识。本项目利用深水底流流经不同深度12KL和Oki02孔位磁学性质、高分辨率主微量元素和UK37SST记录，重建深水底流强度、方向和水团性质等多维属性和北太平洋西边界流强度。随着北太平洋中层水形成的加强，北太平洋中深层的层化相比末次盛冰期加强。海因里希时期强的北太平洋中层水形成，使得中层盐度降低、温度升高这使得中深层之间的层化加强，这个过程将阻碍北太平洋深层与上层海洋的交换，使得海因里希时期太平洋的深部碳与大气更加隔绝。该为全球气候变暖大背景下气候预测、气候驱动机制研究提供理论依据。