The European Space Agency's CryoSat orbiter is giving us a look at how melting ice in Greenland is impacting rising sea levels.  The largest island (at least in the Northern Hemisphere) has lost around one trillion tons of ice between 2011 and 2014.

Greenland's melt from each of those four years contributed three quarters of a millimeter to global sea-levels.  That rate is double the average of the preceding two decades.

The information comes from a new study published in the journal Geophysical Research Letter.  It combines satellite data with a regional climate model to map changes in Greenland ice-sheet mass and show the most detailed recent picture of ice loss from Greenland.  CryoSat carries a radar altimeter that can measure the surface height variation of ice in fine detail, allowing scientists to record changes in its volume with unprecedented accuracy.

"CryoSat's radar really brings into focus our view of the ice sheet, revealing which glaciers are exhibiting the greatest signs of change," says lead author Dr. Mal McMillan from the UK Center for Polar Observation and Modelling at the University of Leeds.  "This helps us to study Greenland's individual outlet glaciers, which in turn allows us to better understand the contribution they have made to global sea-level rise," he added.

The European CryoSat measurement of Greenland ice losses is in close agreement with those computed from NASA's GRACE mission.