20 August 2014 Last updated at 10:01 ET
By Jonathan Amos Science correspondent, BBC News
The team has produced elevation models for the ice sheets
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A new assessment from Europe’s CryoSat spacecraft shows Greenland to be losing about 375 cu km of ice each year.
Added to the discharges coming from Antarctica, it means Earth’s two big ice sheets are now dumping roughly 500 cu km of ice in the oceans annually.
“The contribution of both ice sheets together to sea level rise has doubled since 2009,” said Angelika Humbert from Germany’s Alfred Wegener Institute.
“To us, that’s an incredible number,” she told BBC News.
In its report to The Cryosphere journal, the AWI team does not actually calculate a sea-level rise equivalent number, but if this volume is considered to be all ice (a small part will be snow) then the contribution is likely to be on the order of just over a millimetre per year.
This is the latest study to use the precision altimetry data being gathered by the European Space Agency’s CryoSat platform.
Cryosat uses a radar instrument to measure the shape of polar ice surfaces
The satellite was launched in 2010 with a sophisticated radar instrument specifically designed to measure the shape of the polar ice sheets.
The AWI group, led by senior researcher Veit Helm, has taken just over two years’ worth of data centred on 2012/2013 to build what are called digital elevation models (DEMs) of Greenland and Antarctica, and to asses their evolution.
These models incorporate a total of 14 million individual height measurements for Greenland and another 200 million for Antarctica.
When compared with similar data-sets assembled by the US space agency’s IceSat mission between 2003 and 2009, the scientists are able then to calculate changes in ice volume beyond just the CryoSat snapshot.
Negative shifts are the result of surface melting and ice discharge; positive trends are the consequence of precipitation – snowfall.
Global Climate Change