AT PRESENT THE GREENLAND ICE SHEET IS UNDERGOING RAPID CHANGES LOSING MASS TO THE OCEAN AT AN INCREASING RATE. VARIOUS TECHNIQUES HAVE BEEN USED TO DOCUMENT THESE CHANGES INCLUDING RADAR/LASER ALTIMETRY TIME-VARIABLE GRAVITY AND MASS BUDGET COMBINING ICE DISCHARGE WITH SURFACE MASS BALANCE (SMB) RECONSTRUCTIONS FROM REGIONAL ATMOSPHERIC CLIMATE MODELS (RCM). THIS PROPOSAL ADDRESSES THE LARGEST REMAINING UNCERTAINTY IN ICE SHEET MASS BALANCE WHICH IS THE RUNOFF PRODUCTION FROM SURFACE MELT. WHILE SNOWFALL ACCUMULATION FROM RCM AND MERRA2/GEOS-5 GLOBAL CLIMATE MODEL (GCM) HAS BEEN EVALUATED IN DETAIL FROM A NETWORK OF AUTOMATED WEATHER STATIONS (AWS) SNOW PIT AND ICE CORE DATA RUNOFF IS KNOWN WITH A DEFAULT UNCERTAINTY OF 20% DUE TO A LACK OF IN-SITU DATA FOR EVALUATION. AS RUNOFF WILL REMAIN A DOMINANT COMPONENT OF THE MASS LOSS FOR DECADES TO CENTURIES TO COME IT IS IMPERATIVE TO BETTER QUANTIFY ITS UNCERTAINTY AND DOCUMENT THE RCM/GCM ABILITY TO MODEL IT.