The West Antarctic and Greenland Ice Sheets are vulnerable to even small amounts of global warming. The East Antarctic Ice Sheet, on the other hand, appears more stable. This is fortunate, because East Antarctica holds three-quarters of Earth's ice. Its melting would leave the planet unrecognizable. Although there is little danger of this happening soon, new research suggests a 2ºC (3.6ºF) rise in global temperatures could melt more than a million square kilometers (386,000 square miles) of ice if the temperatures are sustained long enough.
The East Antarctic Ice Sheet (EAIS) is built on a different scale from the rest of the world's frozen water. “Complete melting of the marine-based West Antarctic Ice Sheet (WAIS) would contribute 3-5 meters [10-16 feet] to global mean sea level, whereas the EAIS contains a sea level equivalent of approximately 53 meters [170 feet],” a paper in Nature notes. It's the difference between saving many coastal cities, albeit behind sea walls, and most of the world's population losing their homes.
Numerous studies have found that the WAIS is already melting, and may largely disappear if the oceans around Antarctica warm modestly (although some others offer unexpected hope). But the fate of the EAIS is much less clear. The paper is a result of an investigation of the floor of the Southern Ocean. The ratio of neodymium isotopes in sedimentary layers indicates rates of erosion from nearby landmasses, which in turn reveal if the ice was stable or contracting at the time.
Co-author Dr Kevin Welsh of the University of Queensland reports substantial changes can be detected in the Wilkes Subglacial Basin, a subsection of the EAIS that lies below sea level. “We found that the most extreme changes in the ice sheet occurred during two interglacial periods 125,000 and 400,000 years ago, when global sea levels were several meters higher than they are today,” Welsh said in a statement.
Temperatures in these eras were only around 2ºC (3.6ºF) warmer than pre-industrial levels. If, as seems likely, the world fails to meet the Paris agreement goals by even a small amount, things will soon be at least this warm again.
Welsh told IFLScience this study lacked the “temporal resolution” to tell what would happen to East Antarctica if global temperatures match those in previous interglacials, but does so for briefer times while we find ways to cool the Earth again. Similarly, Welsh said that “other parts of East Antarctica remain to be assessed,” and was reluctant to draw conclusions as to what past melting of Wilkes Land says about the rest of the EAIS, particularly those areas above sea level. However, with Wilkes holding more than half WAIS's ice, it could do plenty of damage on its own.