An extended last glacial maximum in the Southern Hemisphere: A contribution to the SHeMax project

Proxy records from across the Southern Hemisphere show significant local to regional scale variability in climatic and environmental conditions during late Marine Isotope Stage 3 and early Marine Isotope Stage 2, prior to the global last glacial maximum (LGM; 26.5–19.0 kyr). Although not necessarily synchronous across the hemisphere, the regional signature of these pre-26.5 kyr ‘events’ suggests greater complexity of events preceding the global LGM in the Southern Hemisphere than in the North. Here we explore climatic and environmental variability across the Southern Hemisphere during two time-slices: 32 ± 1 kyr (representing the period of Southern Hemisphere summer insolation minimum) and 21 ± 1 kyr (representing the period of maximum global ice volume), based on previously published palaeoclimate proxy data. Temperatures were already approaching glacial levels across the Southern Hemisphere at 32 ± 1 kyr and minimum temperatures were attained in many records at ~21 ± 1 kyr. Furthermore, the descent into minimum temperatures occurred later in Antarctica than elsewhere in the Southern Hemisphere. Effective precipitation was more variable, with evidence for both increased and decreased moisture availability across the hemisphere during each time slice. The pattern of effective precipitation indicates that local factors likely played a more significant role in driving moisture availability compared to temperature. Our findings indicate that the onset of full-glacial conditions across the Southern Hemisphere occurred prior to the attainment of global maximum ice volume.