Climatic evolution in Australia spanning human occupancy over the last 55,000 years

Following on from Marine Isotopic Stage 4 that saw, over the period of 71-59 ka BP, a significant sea level drop (~100 m), low sea-surface temperatures and dry as well as glacial conditions on land, Australia registered wet conditions again, but eventually progressively entered into a glacial phase. By then, humans had arrived on this large continent and a bit later the megafauna progressively became extinct. During those last 55 millennia, Australia and its surrounding seas went through significant and critical climatic changes. This presentation aims at describing in detail those events, based principally on the high-resolution record of two marine cores located offshore the southern Australian margin, and that are then compared with known events on land.

Particular interest is placed on the period that spans the Local Last Glacial Maximum (LLGM), the extent of which thus far had been poorly defined in the Australian region. Emphasis is placed on the period spanning the 34 to 14 ka period to demonstrate that the LGM was not always extremely dry and cold, that people were able to live in inland Australia as water existed in places, despite generally cold conditions. I will estimate using a series of ten maps - at 2 ka intervals over the 34-14 ka period - the waxing and waning of oceanic fronts such as the Subtropical and Subantarctic Fronts, link sea-surface temperatures (SST) with periods of glacial extension in the Australian Alps and Tasmania, as well as the South Island of New Zealand, and the extent of the Leeuwin Current down to south of Australia, the latter current being a direct heat export of the Indo Pacific Warm Pool north of Australia. For this I will use a number of proxies obtained form the 2 cores. I intend also discussing a major event that occurred a bit after 50 ka that saw significant and rapid temperature changes at sea.