THE world's largest frozen water mass, the East Antarctic ice sheet, has been found for the first time to be losing ice at an increased rate.

For years scientists have worried about the smaller West Antarctic ice sheet's net melt, and some recent studies reported that the eastern sheet was growing slightly, due to snowfall.

Now a paper based on satellite measurements shows coastal regions of the East Antarctic, including long stretches of the Australian Antarctic Territory, have been losing ice for the past three years.

Study leader Jianli Chen concluded in the British journal Nature Geoscience: ''As a whole, Antarctica may soon be contributing significantly more to global sea level rise.''

So far the loss of ice from the East Antarctic sheet - although huge in scale at about 57 billion tonnes each year - is tiny in terms of its effect on sea level.

But the amount is not the issue, according to Tony Press, the director of the Antarctic Climate and Ecosystems CRC at the University of Tasmania.

''It's the rate,'' Dr Press said yesterday. ''If the rate is increasing, that's worth keeping a very close eye on.''

Global ice losses now contribute 1.8 millimetres a year to sea level. Growing observations of more losses had led to predictions of an escalating sea level rise of about a metre over the next century, a University of Copenhagen Climate Change Synthesis Report said earlier this year.

This is about double the 2007 predictions of the Intergovernmental Panel on Climate Change.

The accelerated losses in Antarctica were found by Professor Chen's group using NASA satellites.

The complete loss of the eastern sheet would raise the sea level by about 50 metres, according to a briefing for the International Polar Year.

Professor Chen's group studied monthly samples from 2002 to early this year, and confirmed other findings that the West Antarctic ice sheet was losing about 132 billion tonnes of ice a year.

The scientists found no change in the East Antarctic until 2006.