[U-03] Advanced understanding of Quaternary and Anthropocene hydroclimate changes in East Asia

[U03-09] Orbital forcing paced Patagonian Ice Sheet extent and southern climate during the Last Glacial Period

★Invited Papers

*Adam David Sproson¹、Yusuke Yokoyama²、Yosuke Miyairi²、Takahiro Aze²、Vincent J. Clementi³、Hailey Riechelson³、Samantha C. Bova⁴、Yair Rosenthal^3,5、Laurel B. Childress⁶ (1.Biogeochemistry Research Center, Japan Agency for Marine-Earth Science and Technology、2.Atmosphere and Ocean Research Institute, The University of Tokyo、3.Department of Marine and Coastal Sciences, Rutgers University、4.Department of Geological Sciences, San Diego State University、5.Department of Earth and Planetary Sciences, Rutgers University、6.International Ocean Discovery Program, Texas A&M University)

キーワード：Beryllium isotopes, Patagonian Ice Sheet, Southern Hemisphere climate, Last Glacial Period

During the late Quaternary, similar trends in Southern Hemisphere climate proxies and Northern Hemisphere insolation intensity has led to the conclusion that northern insolation paces southern climate [1]. However, expansion of Northern Hemisphere ice sheets during the Last Glacial Maximum occurred several thousand years after mid-latitude Southern Hemisphere glaciers [2, 3], indicating sensitivity of southern climate to local forcing factors [4]. Reconstructing the history of southern mid-latitude ice sheets can therefore elucidate global climate forcing. Here, we present reactive beryllium isotope (¹⁰Be/⁹Be) measurements of marine sediments collected from the south Chilean margin during the D/V JOIDES Resolution Expedition 379T [5].These records provide a reconstruction of the western margin of the Patagonian Ice Sheet over the ~86 thousand years.

We find that Patagonian Ice Sheet glacial advances and retreats predate Northern Hemisphere ice sheets by up to six thousand years, similar to estimates for New Zealand glaciers [2]. Glacial maxima coincide with precession maxima and obliquity minima and consequently, shorter southern summers [6]. This would have led to expansion of Antarctic sea-ice [4] and changes in the position and strength of the Southern Hemisphere Westerly Winds [7] resulting in cooling and rapid glacial expansion over Patagonia within one thousand years (this study). As southern summers lengthened, this trend reversed, leading to the gradual retreat of southern mid-latitude glaciers for three thousand years (this study), CO₂ release from the Southern Ocean [8] and heat flux to the North Atlantic [9]. The latter mechanism provided a southern “trigger” for Northern Hemisphere deglaciation.

[1] J. Imbrie et al. Paleoceanography 7, 701-738 (1992). [2] M. J. Vandergoes et al. Nature 436, 242-245 (2005). [3] B.J. Davies BJ et al. Earth-Science Reviews 204, 103152 (2020). [4] C. Fogwill et al. Scientific Reports 5, 1-10 (2015). [5] C. Li et al. Geochemistry, Geophysics, Geosystems, e2022GC010350 (2022). [6] P. Huybers & G. Denton. Nature Geoscience 1, 787-792 (2008). [7] F. Lamy et al. PNAS 116, 23455-23460 (2019). [8] R. Anderson et al. Science 323, 1443-1448 (2009). [9] G. Knorr & G. Lohmann. Nature 424, 532-536 (2003).