Southern Hemisphere pacing of global climate during the Late Pleistocene

During the Late Pleistocene, similar trends in Northern Hemisphere insolation intensity and Southern Hemisphere climate proxies has led to the conclusion that northern insolation paces southern climate [1]. However, expansion of mid-latitude Southern Hemisphere glaciers predate Northern Hemisphere ice sheets by several thousand years [2], suggesting sensitivity to local forcing factors [3]. 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 [4]. These records provide a reconstruction of the western margin of the Patagonian Ice Sheet (PIS) over the last ~86 thousand years.

We find that PIS advances and retreats predate Northern Hemisphere ice sheets by up to six thousand years, similar to estimates from New Zealand glaciers [2]. Glacial maxima coincide with obliquity minima and precession maxima and therefore shorter southern summers [5]. This would have led to expansion of Antarctic sea-ice [3] and changes in the position and strength of the Southern Hemisphere Westerly Winds [6] resulting in cooling and glacial expansion over Patagonia. As southern summers lengthened, this trend reversed, leading to abrupt termination of southern mid-latitude glaciers (this study), CO2 release from the Southern Ocean [7] and heat flux to the North Atlantic [8], with the latter representing a southern "trigger" for northern deglaciation. Finally, superimposed on this long-term trend are shorter, millennial-scale, expansions of the PIS that coincide with Antarctic Isotope Maxima suggesting an atmospheric teleconnection between Patagonian cooling and Northern Hemisphere warming (Dansgaard-Oeschger events).

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