Antartica is melting away

Sea levels may rise rapidly because of the melting Antartic ice sheet. Scientists discovered that the Antartic ice sheet has thinned significantly over the past 4 years instead of increasing in size. From Times Online:

The findings, from the satellites of the Gravity Recovery and Climate Experiment (Grace) begun in 2002, are a concern because the ice sheet would increase sea levels by as much as 45m (150ft) were it all released. The West Antarctic ice sheet, where the bulk of the melting is taking place, holds water that would raise the sea level by more than 6m (20ft). The East Antarctic sheet, which is eight times larger, appears to be more stable...

It found that the volume of ice being lost from the ice sheet, which is up to 2,000m thick, is raising global sea levels by 0.4mm a year. Melting ice from Greenland is contributing another 0.5mm to sea level rise.