Meridional Shifts of the Southern Hemisphere Westerlies During the Early Cenozoic

• Published in: Geophysical Research Letters
• Main Authors: Chen, Hongjin, Xu, Zhaokai, Bayon, Germain, Fan, Qingchao, von Strandmann, Philip A. E. Pogge, Wang, Wei, Sun, Tianqi, Li, Tiegang
• Format: Report
• Language: English
• Published: AMER GEOPHYSICAL UNION 2024
• Subjects: early Cenozoic; IODP expedition 369; Mentelle Basin; Southern Hemisphere westerlies; chemical weathering; Geology; Geosciences; Multidisciplinary; ND ISOTOPIC COMPOSITION; HOLOCENE CHANGES; LATE PALEOCENE; SEA-LEVEL; EOCENE; OCEAN; HF; RECORD; TEMPERATURE; CLIMATE; Antarc*; Antarctic; Ice Sheet
• Online Access: http://ir.qdio.ac.cn/handle/337002/186335; http://ir.qdio.ac.cn/handle/337002/186336; https://doi.org/10.1029/2024GL110182

Despite the crucial role of the Southern Hemisphere (SH) westerlies in modulating modern and past climate evolution, little is known about their behavior and possible forcing mechanisms during the early Cenozoic. We probe changes in the hydroclimate of southwest Australia during 62-51 Ma, based on sedimentary proxy records from the International Ocean Discovery Program Site U1514 in the Mentelle Basin. Our results reveal a transition from a less humid climate to wetter conditions at mid-high latitudes starting from the early Eocene, which suggests poleward migration of the SH westerlies. This long-term trend is punctuated by short-lived events of aridification during the Mid-Paleocene Biotic Event and wetter intervals during the Paleocene-Eocene Thermal Maximum, indicating additional short-term meridional shifting of the westerlies. We propose that the evolution of SH westerlies was driven by the equator-to-pole temperature gradient regulated by global warming and ephemeral growth of the Antarctic ice sheet. The Southern Hemisphere (SH) westerlies, which are the dominant atmospheric circulation patterns in the middle latitudes, play a key role in regulating global and regional climate. Currently, the knowledge of past changes in SH westerlies relies mainly on the late Quaternary. Its dynamics over longer timescales, especially under early Cenozoic greenhouse climate states, remain poorly understood. The Mentelle Basin off southwest Australia was located at a more southerly location than at the present day, and was potentially under the influence of SH westerlies. To examine the long-term hydroclimate changes in southwest Australia during the mid-late Paleocene to the early Eocene (62-51 Ma), we measured neodymium and hafnium isotopic compositions of fine-grained detrital sediments from a borehole (IODP Site U1514) drilled in the Mentelle Basin, in addition to clay mineralogy, and elemental abundances. Our results suggest a gradual wetting of southwest Australia since the early Eocene, which we relate to the ...