IODP Exp 346: Onset and evolution of millennial-scale variability of the Asian monsoon (sailing participation)

亚洲季风是地球上对流最活跃的大气环流系统，其季节性降雨影响着世界上约一半的人口。现代季风降雨的时间和分布有相对较好的记录，但过去亚洲季风变化的时空模式限制较少。最近的证据表明，东亚和印度的夏季风与丹斯加德-奥斯格赫(D-O)循环有很大的不同。这些循环具有全球共鸣，因为它们似乎通过大气、海洋、圆圈和生物圈之间的复杂相互作用在南北半球之间耦合。在典型的D-O循环中，北大西洋的缓慢降温突然终止，因为快速变暖以千年尺度的步调反复出现。收集地球在D-O循环期间气候响应的全面图景，对于了解突如其来的变暖事件是如何被放大并通过气候系统传播至关重要。归根结底，这一点很重要，因为北部高纬度地区D-O循环期间的气温上升速度与未来几十年预计的变暖速度相当。喜马拉雅和青藏高原(HTP)是地球上地形最壮观的地貌之一，在决定亚洲季风强度方面发挥着关键作用。此外，HTP的大小形成了阻碍低层西风急流环流(WJC)的障碍。地质记录表明，青藏高原从大约50年前开始抬升，大陆干旱加剧，晚新生代降温，亚洲夏季风和冬季风增强，甚至可能导致大气二氧化碳的风化和减少。此外，有人认为，约3.6 Ma HTP的重新抬升和伸展是D-O型气候变率开始的触发因素。季风变化和D-O循环之间的一致性被认为是上更新世HTP重新抬升的结果，产生了两种离散的WSC模式。这两种大气环流模式的出现也为北大西洋记录的D-O事件提供了一种潜在的遥相关。综合大洋钻探计划探险346计划对从日本海到东中国海北部的7个宽纬度范围的站点进行取心和记录，以检验上更新世HTP的抬升以及随后出现的两个离散的WJC模式，导致东亚夏季风和冬季风千年尺度变率放大的假说。IODP 346旨在恢复将提供以下地质证据的岩芯：(1)监测WJC、EASM、EAWM和对马暖流的过去行为；(2)重建亚极锋和冰筏碎片的行为；(3)了解日本海的通风历史及其与通过对马海峡流入淡水和冬季冷却的联系。

The Asian monsoon is the most convectively active atmospheric circulation system on Earth, and its seasonal rains impact about half the world's people. The timing and distribution of modern monsoon rainfall is relatively well documented, but past spatio-temporal patterns of changes in the Asian monsoon are poorly constrained. Recent evidence suggests the East Asian and Indian summer monsoons have varied significantly in concert with Dansgaard-Oescgher (D-O) cycles. These cycles have global resonance as they appear to be coupled between northern and southern hemispheres via complex interactions between the atmosphere, ocean, cyrosphere and biosphere. During a typical D-O cycle, slow cooling in the North Atlantic is terminated abruptly by rapid warming that recurs at a millennial-scale pacing. Assembling a comprehensive picture of Earth's climate response during D-O cycles is essential to understanding how abrupt warming events are amplified and propagated through the climate system. Ultimately this is important because the rate of temperature increase during a D-O cycle in northern high latitudes is comparable to rates of warming projected for the coming decades. The Himalaya and Tibetan Plateau (HTP), one of the most topographically imposing features on Earth, plays a key role in determining the strength of the Asian monsoon. In addition, the size of the HTP forms an obstacle that blocks low-level Westerly Jet circulation (WJC). Geological records have implicated the uplift of the Tibetan Plateau, starting c. 50 Myr ago, in enhanced continental aridity, late Cenozoic cooling, intensification of the Asian summer and winter monsoon, and even perhaps causing increased weathering and drawdown of atmospheric CO2. Furthermore, it has been proposed that the renewed uplift and extension of the HTP at c. 3.6 Ma acted as a trigger for the onset of D-O-type climatic variability. The coherence between monsoon variability and D-O cycles is therefore thought to be a consequence of renewed HTP uplift during the Plio-Pleistocene, creating two discrete modes of WSC. The emergence of these two modes of atmospheric circulation also provides a potential teleconnection to D-O events documented in the North Atlantic. Integrated Ocean Drilling Program (IODP) expedition 346 proposes to core and log seven sites covering a wide latitudinal range from the Japan Sea to the northern East China Sea to test the hypothesis that Plio-Pleistocene uplift of the HTP, and the consequent emergence of two discrete modes of WJC, caused the amplification of millennial-scale variability in the East Asian summer (EASM) and winter (EAWM) monsoons. IODP 346 aims to recover cores that will provide the geological evidence that (1) monitors past behaviours in the WJC, EASM, EAWM and the Tsushima Warm Current; (2) reconstructs the behaviour of the sub-Polar Front and ice-rafted debris, and (3) understands the ventilation history of the Japan Sea and its link to the influx of freshwater through the Tsushima Strait and winter cooling.