Late Pliocene-Pleistocene Antarctic climate variability at orbital and suborbital scale: ice sheet ocean and atmospheric interactions

Continental margin drill core and seismic data indicate that between 3.0 and 2.5 Ma, high-latitude climate cooling drove both the West and East Antarctic Ice Sheets towards their present expanded cold polar state. Ice margins developed permanent marine termini with ice shelves. Direct physical sedimentary records of Antarctic Ice Sheet variability (e.g. ice-rafted debris, proximal glacimarine cycles) and more distal ocean records of sea-ice distribution (e.g. diatom palaeoecology), thermohaline circulation (e.g. sortable silt), ocean temperatures (e.g. δ18O), frontal dynamics and surface circulation (e.g. palaeoecological assemblages and sea-surface temperature (SST) reconstructions) all show a strong covariance with the 41 kyr cycle in Earth's obliquity between 3 and 1 Ma. Glacial periods are characterised by northward expansion of seasonal sea ice, SSTs up to 6°C colder than now, equatorward migration of frontal zones by 5–10° latitude, intensification of zonal westerly winds, invigorated surface circulation (e.g. Antarctic Circumpolar Current) and intensified abyssal currents. These processes lead the δ18O ice volume maximum by 3–7 kyr, at which time Antarctic Ice Sheets were fully extended onto the continental shelf. Antarctic ice volume changes were in part controlled by the effect of Northern Hemisphere glacio-eustasy on its marine margin, and this mechanism accounts for much of the orbital variability of the last 2.6 myr. An enigmatic interval of foraminiferal ooze and coccolith-bearing sediments in Weddell Sea and Prydz Bay sediment cores, together with a bioclastic limestone in the Ross Sea at 1 Ma, imply a significant warming and change in ocean chemistry around the periphery of Antarctica. This event, which occurs within the short normal polarity Jaramillo Subchron in Ross Sea cores, is correlated with warm Marine Isotope Stage 31. The anomalous warming implies an increase of 4–6°C in SST, possible incursion of Subantarctic Surface Waters and depression o