A marine record of Patagonian ice sheet changes over the past 140 ka

Abstract

Terrestrial glacial records from the Patagonian Andes and New Zealand Alps document quasi-synchronous southern hemisphere-wide glacier advances during the late Quaternary. Although detailed, these records are inherently incomplete. Here, we provide a continuous marine record of Patagonian Ice Sheet (PIS) extent over a complete glacial/interglacial cycle back to the previous glacial (~140 ka). Sediment core MR16-09 PC03, located at 46° S and ~150 km offshore Chile, received high terrestrial sediment input when the PIS advanced westward. We use biomarkers, foraminiferal oxygen isotopes, and major element data for reconstructing terrestrial sediment and freshwater input related to PIS variations. Our sediment record documents four major intervals of general PIS advance, during Marine Isotope Stage (MIS) 6 (135 – 140 ka), late MIS 5 (~85 – 95 ka), MIS 4 (~60 – 70 ka) and late MIS 3 to MIS 2 (~18 – 40 ka). These higher terrigenous input intervals occur during sea-level low stands when the western PIS covered most of the Chilean fjords which today retain glaciofluvial sediments. Superimposed, high amplitude phases of enhanced sediment supply reoccur at millennial time scales and reflect marine-based phases of the PIS with direct sediment discharge to the continental slope. We assign the late MIS 3 to MIS 2 phases and, by inference, also older advances to Antarctic stadials, consistent with the terrestrial record. Concomitantly, we observe enhanced meltwater release and conclude that the temperature-controlled PIS advances during southern hemisphere cold phases were likely reinforced by higher precipitation through enhanced westerly winds at the northwestern margin of the PIS.