Orbital and millennial-scale forcing of the Patagonian Ice Sheet throughout the Last Glacial Cycle

During the Last Glacial Maximum (23,000 to 19,000 years ago), the Patagonian Ice Sheet covered the central chain of the Andes between 38 °S and 55 °S. The paleoclimatic evidence from Patagonia and New Zealand suggests that the maximum glacier expansion of the Southern Hemisphere mid-latitudes was desynchronized with the Northern Hemisphere glacial history. Here we present numerical simulations of the Patagonian ice sheet throughout the Last Glacial Cycle. Our analysis suggests that the Patagonian ice sheet had two main periods of advance, during the Marine Isotope Stage 4 and late Marine Isotope Stage 3, experiencing inter-millennial scale variability. We show that the Patagonian Ice Sheet long-term evolution can be attributed to changes in the integrated summer insolation, which combines the summer duration and insolation intensity and has an obliquity-like periodicity. We further suggest that this metric also modulated the behaviour of glaciers over the entire Southern Hemisphere mid-latitudes.