Monsoonal activity and paleoclimate evolution in the NW-Pacific over the past 4 Ma

近4 Ma西北太平洋季风活动与古气候演变

• 批准号: 467601169
• 负责人: Professor Dr. Lorenz Schwark
• 金额: --
• 依托单位: Arbeitsgruppe Organische Geochemie
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/467601169?language=en
• 关键词: Monsoonal; activity; paleoclimate; evolution; NW

The North Pacific constitutes a critical element in global climate evolution via glaciation-modulated heat transport within the North Pacific Gyre, regulation of latitudinal and meridional temperature exchange and by driving global wind systems. The western boundary current, the Kuroshio is crucial in water transport, the Asian Monsoons and westerly Jetstream are essential for air mass transport regulating Pacific climate. The last 4 Ma (Million yeasrs) of Pacific climate evolution with the Mid Pleistocene Warm Period (MPWP), the onset of Northern Hemisphere Glaciation (NHG), the Mid-Pleistocene Transition (MPT) and the Mid-Brunhes Event include dramatic phases of climate reorganization. In the equatorial belt and the Eastern Pacific, the climate evolution is studied well, whereas in the NW-Philippine Sea, which is strongly influenced by the Kuroshio and the strength of Asian wind systems, a long-term paleoclimate record is still missing. Sediment cores drilled at site U1437 provide a continuous and well dated record over 4 Ma, for which in previous projects we generated a substantial amount of data though the temporal resolution remains very unsatisfactorily between 1 and 3 Ma. Our studies covering the past 1 Ma were based on molecular proxies (TEX86, UK‘37) for sea surface temperature reconstruction and for the first time in the Pacific on molecular tracers for Asian dust influx using plant wax lipids. The temporal resolution of the existing record does not permit a reconstruction of the critical climate phases of the MPWP, the NHG, and the MPT. For this purpose, 150 additional samples have to be studied to complement the existing data set at a resolution of 10 to 20 ka, which will cover the 40 ka frequency band of orbital rhythmicity. The unique study on dust-associated wax lipid study in the Pacific requires an extension for improved recognition of source regions and wind trajectories that may be facilitated by compound specific isotope analysis of lipids. In combination with structural composition of lipids and continuous records of trace element influx achieved by XRF-Scanning, provenance studies and wind system reconstruction over 4 Ma can be achieved. We will address the emerging topic of discrimination between Asian monsoonal wind systems and the Westerly Jetstream as major dust transport agents in the Pacific. For the past 1 Ma we postulate a latitudinal fluctuation in the ITCZ and the dominant westerly wind system at site U1437, which based on the study of a single location is difficult to prove. For selected neighboring sites ODP 1208 and DSDP 296, where excellent chronologies are available, we will study samples from selected high wind intensity intervals to obtain a regional pattern of latitudinal wind shifts.A completion of the existing preliminary data set at site U1437 will facilitate and close a large gap in West Pacific paleoclimate reconstruction for teh past 4 Ma.

北太平洋通过北太平洋环流内冰川调节的热传输、纬度和经向温度交换的调节以及驱动全球风系统，构成了全球气候演变的关键要素。西边界流、黑潮对于水运至关重要，亚洲季风和西风急流对于调节太平洋气候的气团运输至关重要。太平洋气候演变的最后 4 Ma（百万年），包括中更新世暖期 (MPWP)、北半球冰川期 (NHG) 的开始、中更新世转变 (MPT) 和中布伦赫斯事件，包括气候重组的戏剧性阶段。在赤道带和东太平洋，气候演化研究得很好，而在西北-菲律宾海，受黑潮和亚洲风系统强度的强烈影响，仍然缺乏长期的古气候记录。在 U1437 地点钻探的沉积物岩心提供了超过 4 Ma 的连续且过时的记录，在之前的项目中，我们为此生成了大量数据，尽管时间分辨率在 1 到 3 Ma 之间仍然非常不令人满意。我们涵盖过去 1 Ma 的研究基于用于海面温度重建的分子代理（TEX86、UK‘37），并首次在太平洋使用植物蜡脂对亚洲沙尘流入的分子示踪剂进行了研究。现有记录的时间分辨率不允许重建 MPWP、NHG 和 MPT 的关键气候阶段。为此，必须研究150个额外样本，以补充现有分辨率为10至20 ka的数据集，这将覆盖轨道节律性的40 ka频段。太平洋地区与灰尘相关的蜡脂研究的独特研究需要扩展，以提高对源区和风轨迹的识别，这可以通过脂类的化合物特异性同位素分析来促进。结合脂质的结构组成和 XRF 扫描实现的微量元素流入的连续记录，可以实现起源研究和超过 4 Ma 的风系统重建。我们将讨论亚洲季风系统和西风急流作为太平洋主要沙尘输送媒介之间的歧视这一新出现的话题。对于过去的1Ma，我们假设ITCZ和U1437站点的主导西风系统存在纬度波动，但基于单个位置的研究很难证明这一点。对于选定的邻近站点 ODP 1208 和 DSDP 296，这些站点可以提供出色的年表，我们将研究选定的高风强度间隔的样本，以获得纬向风移的区域模式。完成站点 U1437 现有的初步数据集将有助于并缩小过去 4 Ma 西太平洋古气候重建的巨大差距。