But new University of Otago research gave scientists better clues about just how much the ice sheets would respond to climate change.
A chance find of an unstudied Antarctic sediment core led geologist Dr Christian Ohneiser to restudy how often Antarctic ice ages occurred.
The research found that ice ages were much more frequent than previously assumed.
"Until this research, it was common knowledge that over the last million years, global ice volume (which includes Antarctica’s ice sheets) expanded and retreated every 100,000 years.
"However, this research shows they actually advanced and retreated much more often — every 41,000 years — until at least 400,000 years ago."
He said the 6.2-metre sediment core was recovered from the Ross Sea in 2003 and placed in an archive in the United States, but was not studied further.
"I sampled it because I was expecting the core to have a record spanning the last 10,000 or so years.
"I conducted a paleomagnetic analysis on the core, which reconstructs changes in the earth’s magnetic field, and found a magnetic reversal showing it was much older and had a record spanning more than 1million years."
The sedimentary and magnetic mineral indicators enabled Dr Ohneiser to determine how big the Ross Ice Shelf was, and work out the size of the West Antarctic Ice Sheet which fed the shelf.
He said previous understanding of ice age frequencies were based on assumptions and incomplete data sets, but knowledge of them was important as the world faced climate change.
"Antarctica’s ice sheets have the capacity to increase sea-level significantly over the coming centuries.
"Paleoclimate reconstructions can give us clues on how the ice sheets might behave as atmospheric CO2 levels increase.
"Because the response of ice sheets to any change in climate occurs very slowly, reconstructions on past ice sheet behaviour provide constraints on how big or small the ice sheets were and how quickly they have retreated and regrown under different climate conditions.
"These reconstructions provide baseline information on [the] natural behaviour of ice sheets in the past before humans started messing with the atmosphere."
