Science 323, 753 (2009)

Credit: KAZMANIAC/ISTOCKPHOTO.COM

The break-up of the West Antarctic Ice Sheet could cause a disproportionate amount of sea level rise along coastlines in North America and the Indian Ocean. Typical analyses suggest that if the ice sheet melted, it would raise average global sea level by five metres — but this may understate the impacts on some regions, according to a new study.

Jerry Mitrovica of the University of Toronto and colleagues used a technique called sea level fingerprinting to assess the potential impacts of a catastrophic loss of the ice covering West Antarctica. This technique, most commonly used to pinpoint the source of major flooding in the past, works on the principle that massive ice sheets, such as those covering Antarctica, exert a gravitational pull on seawater. When the ice is gone, so is the attraction; consequently, seawater begins to migrate away from the site of the former ice sheet.

If the ice sheet melted completely, the resulting changes in gravitational shift, in uplift of the region and in the Earth's rotation could cause an additional 1.3 metres of flooding in North American cities such as Washington DC. However, concurrent ice loss in Greenland and East Antarctica could further alter these patterns of changing sea level.