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

• Applicant: Professor Dr. Lorenz Schwark
• Subject Area: Geology ; Mineralogy, Petrology and Geochemistry
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 467601169

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.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 527: Bereich Infrastruktur - "International Ocean Discovery Program" (IODP)
• International Connection: Japan
• Cooperation Partner: Professorin Dr. Myriam Kars