The instabilities in Antarctica's east ice sheet have been mapped out in a study, with scientists warning rapid sea level rise could occur if the sheet melts.
East Antarctica's Totten Glacier was examined in the airborne survey, which looked at how the ice sheet had advanced and retreated in the past based on glacial erosion patterns.
Two unstable zones were uncovered and linked to a massive retreat of the ice sheet in the past.
The two zones are prone to rapid collapse, Australian lead author Dr Alan Aitken says.
And rising carbon dioxide levels and global temperatures are already believed to have influenced the retreat of Antarctic ice shelves.
"These changes may spread deep inland in the decades to come, perhaps triggering the instabilities identified in this study," Dr Aitken says.
He warns a melt could lead to a rapid rise in sea level of at least two metres.
"There is a significant risk of this occurring unless global temperatures are kept within a few degrees of present."
The problem of rising sea levels could be worse than that though -- because it's so unstable, it's not known exactly how much of a rise Totten Glacier influences.
"The influence of Totten Glacier on past sea level is clearly notable, but for any particular warm period it is also highly uncertain, because the system is subject to progressive instability."
The full study was published in the prestigious journal Nature on Thursday.