Greenland ice mass budget
Researchers           Mass Change     Method      Time Span
                                     (GT/year)
Krabill et al. 2000              -47      Aircraft Surveys 1994-1999
Velicogna et al. 2006  -200 to -260      GRACE      2002-2006
Luthcke et al. 2007*    -145 to -175      GRACE     2003-2006
Zwally et al. 2007*       -80 to -100        ICESat      2003-2005

GRACE is a gravity recovery mission
ICESat is a lidar topographymission

NASA website on Greenland ice sheet

A great deal of effort is going into estimating how the Greenland ice sheet is changing
100 GT/yr ~ 0.3 mm/yr sea level rise