The Antarctic ice sheet is losing approximately 159 billion tons of ice every year, twice as much as previously believe.

A team of scientists from the UK Centre for Polar Observation and Modelling, led by researchers at the University of Leeds, made the discovery after three years of observations, according to a press release issued by the university.

Researchers made the discovery by using measurements collected by the European Space Agency's CryoSat-2 satellite mission.

The satellite carries an altimeter specially designed to survey essentially the entire Antarctic continent, reaching within 215 kilometres of the South Pole.

Thanks to the satellite, the researchers were able to make the first complete assessment of Antarctic ice sheet elevation change.

Problem areas like the rugged terrain of Antarctic Peninsula can also now be surveyed.

"On average West Antarctica lost 134 gigatonnes of ice, East Antarctica three gigatonnes, and the Antarctic Peninsula 23 gigatonnes in each year between 2010 and 2013 - a total loss of 159 gigatonnes each year," according to the release.

Ice thinning has been discovered in areas that were poorly surveyed by past satellite altimeter missions in West Antarctica.

The average rate of ice thinning in West Antarctica has increased as well, and this sector is now losing approximately one third (31%) as much ice each year than it did during the five year period before CryoSat-2 was launched, according to the release.

"Thanks to its novel instrument design and to its near-polar orbit, CryoSat allows us to survey coastal and high-latitude regions of Antarctica that were beyond the capability of past altimeter missions, and it seems that these regions are crucial for determining the overall imbalance," Professor Andrew Shepherd, also of the University of Leeds, who led the study, according to the release.

This sector of Antarctica is known as the most vulnerable to changes in climate. According to recent assessments, its glaciers could have passed "a point of irreversible retreat," according to the release.

"Although we are fortunate to now have, in CryoSat-2, a routine capability to monitor the polar ice sheets, the increased thinning we have detected in West Antarctica is a worrying development. It adds concrete evidence that dramatic changes are underway in this part of our planet, which has enough ice to raise global sea levels by more than a meter. The challenge is to use this evidence to test and improve the predictive skill of climate models," said Shepherd.

CyoSat launched in 2010 according to the release. It carries a radar altimeter that is able to "see" through clouds and in the dark. This provides continuous measurements over locations like Antarctica that are known to have long periods of darkness or bad weather.

The radar is capable of measuring the surface height variation of ice in fine detail, which allows scientists to document changes in its volume with "unprecedented accuracy," according to the release.

"The increasing contribution of Antarctica to sea-level rise is a global issue, and we need to use every technique available to understand where and how much ice is being lost. Through some very clever technical improvements, McMillan and his colleagues have produced the best maps of Antarctic ice-loss we have ever had," said Professor David Vaughan of the British Antarctic Survey, according to the release. "Prediction of the rate of future global sea-level rise must be begin with a thorough understanding of current changes in the ice sheets - this study puts us exactly where we need to be."

Research was published in the journal Geophysical Research Letters.

Professor Vaughan and Dr. Joughin were not involved in the study.

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