The West Antarctic Ice Sheet, along with the East Antarctic Ice Sheet and Greenland, is one of the three great ice sheets of the world. Of the three, the West Antarctic Ice Sheet is believed to be the most unstable, because much of its base rests on rock that is below sea level. It’s thought that this fact makes it vulnerable to melting and relatively rapid disintegration.
A vast amount of research has investigated the implications of the West Antarctic Ice Sheet collapsing. All these studies have indicated that sea levels would rise by about five- or six-metres. However, a recent study in the journal Science has calculated that these estimates are far too large, even on a 1,000-year timescale.
According to the study, the melting of the ice sheet would raise global average sea level by about 3.3 metres. The study found parts of the ice sheet are more stable than previously thought and so would probably not slip into the sea even in a warmer world.
The study found the melting of the West Antarctic Ice Sheet would change the focus of the planet's gravitational field and sea levels would rise disproportionately more around North America than elsewhere. This would be because the loss of so much mass from the southern hemisphere would effectively make the pull of gravity stronger in the northern hemisphere, affecting the spin of the Earth and causing sea levels to rise higher especially around the North American continent and in the Indian Ocean.
Increases of 25 per cent more than the global average on the East and West coasts of North America would cause catastrophic flooding in cities such as New York, Vancouver, and San Francisco.
However, it’s not known how long it will take for the ice sheet to disappear, if global temperatures continue to rise. Many scientists believe this would take at least 500 or even 1,000 years.