What happened at the end of the mid-Pleistocene transition in the Southern Hemisphere? Insights from western Tasmania, Australia

The current southward shift in the southern westerlies that is stripping southern Australia of rainfall is unprecedented over the past 12 kyrs years at least, and is due to the effects of both the anthropogenic hole in the ozone layer and greenhouse gas-driven global warming. Predictions of future climate suggest the Earth is moving in to a “super-interglacial” (peak warming) because of anthropogenic greenhouse gas release. “Super-interglacials”, which are warmer than today, are uncommon in the geological record. A recent increase in the frequency of these peak warming events since ca. 450 ka (the end of the mid-Pleistocene transition; MPT) is associated with a 7° latitude southward shift of the southern westerlies and an increase in atmospheric CO2 that warmed the atmosphere - a stark similarity to current trends. Here, we present multi-proxy analyses of two closely spaced (<50 km) sediment cores that comprise a complete sequence from the mid-Pleistocene to the present from western Tasmania, Australia - in the mid-latitudes of the Southern Hemisphere. Lake Selina is a modern-day lake with a continuous ca. 230 kyr sediment sequence, while Darwin Crater is a palaeo-lake within a meteorite impact crater that formed at ca. 816 ka and which completely in-filled during MIS5 (ca. 120 ka). We report on petrophysical whole core logging, lithological core description, spectrophotometry, grain size, natural gamma ray, paleo- and rock-magnetism, loss-on-ignition, pollen analyses and micro-XRF geochemisrty. The composite record is unique in the Australian sector of the Southern Hemisphere and we discuss the data in the context of the global and regional changes that occurred at the end of MPT, paying particular attention to impact of the shift toward warmer super-interglacials, the large-scale southward shift of the southern westerlies and higher atmospheric CO2 content that occurred at ca. 450 ka (MIS11 to present).

Keywords

Pleistocene Epoch, Southern Hemisphere, Australia, Rain, Winds, Tasmania, Ozone layer, Greenhouse gases, Greenhouse effect

Citation

Fletcher, M.-S., Lisé-Pronovost, L., Mallett, T., Mariani, M., Cooley, S., May, J.-H., Gadd, P., Herroes, A., Blaauw, M., Heijnis, H., Hodgson, D., & Pedro, J. (2019). What happened at the end of the mid-Pleistocene transition in the Southern Hemisphere? Insights from western Tasmania, Australia. Poster presented to the 20th INQUA Congress, 25th - 31st July 2019, Dublin, Ireland, (P-4494). Retrieved from: https://virtual.oxfordabstracts.com/#/event/public/574/submission/1834