New research involving Curtin University suggests the Southern Hemisphere began to shake off the last ice age independent of the Northern Hemisphere.
Published in Nature, co-author Dr Ross Edwards of Curtin’s Department of Imaging and Applied Physics was part of the team that analysed the 3405-metre ice core out of the West Antarctic Ice Sheet (WAIS) as part of the WAIS Divide Project to reconstruct the climate history of West Antarctica.
The team were able to determine that warming in West Antarctica occurred earlier than previously thought, pointing to a different sequence in the shift from an ice age world to the current warm period.
Dr Edwards said precise dating of the ice core was fundamental to the study and meant the record could be compared to the Northern Hemisphere during the deglaciation. This comparison has given vital clues to the processes underlying major climate shifts and lays to rest questions regarding leads and lags between Northern and Southern deglacial warming.
“Many reports before now have suggested the Northern Hemisphere warmed first and the Southern Hemisphere followed as a direct consequence, due to changes in the Earth’s orbit and reflectivity and topography of the northern ice sheets,” Dr Edwards said.
“The new study suggests that changes in the Southern Hemisphere were responsible for the timing of the ice core record. In other words, feedback processes in the Southern Hemisphere initiated the warming rather than feedback processes in the north.”
Dr Edwards said knowing how these changes occurred was fundamental to predicting future shifts in a warming world and how fast they would occur.
His role in the project was to analyse the top 577 metres of the ice core at 1 cm resolution, using a continuous ice core melter chemical analysis system.
The heart of the analytical system vaporised water from the ice core and smashed it into atoms – the atoms were then ionised and weighed to determine elemental impurities.
“Black carbon content was also analysed to gather seasonal data due to smoke, which is typically highest during September and October reflecting the Southern Hemisphere’s dry-season fires”, Dr Edwards said.
“The WAIS is the Earth’s memory – we melt the ice and revive those memories of the past atmosphere from thousands of years ago. We learn how it evolved and how it will evolve into the future.
“West Antarctic ice core records are vital to understanding Australia’s climate history, particularly because West Antarctica is exposed to the Pacific Ocean, allowing it to record important modes of climate variability”.