THE GREENLAND ICE SHEET (GRIS) HAS BEEN EXPERIENCING INCREASING MASS LOSS VIA SURFACE MELT AND DYNAMIC THINNING OVER THE PAST DECADES WHICH HAS LED TO AN INCREASE IN SEA LEVEL. MASS BALANCE ON THE GRIS IS THE DIFFERENCE BETWEEN ACCUMULATION (MASS GAIN) AND ABLATION (MASS LOSS) PROCESSES. AN IMPORTANT FACTOR OF MASS BALANCE IS THE AMOUNT OF SUBSURFACE MELTWATER HIDDEN WITHIN THE ICE SHEET. THIS MELTWATER CAN EITHER BE STORED PERENNIALLY IN FIRN AQUIFERS OR BURIED LAKES BUFFERING SEA LEVEL OR BE DRAINED QUICKLY BY THE HYDROLOGIC NETWORK LEADING TO MORE IMMEDIATE SEA LEVEL CHANGE. ICESAT AND OPERATION ICEBRIDGE (OIB) ALTIMETRY OIB RADAR DATA FIELD MEASUREMENTS AND MODELING ANALYSIS WILL BE UTILIZED TO DETERMINE IF A CONNECTION EXISTS BETWEEN THE PRESENCE OF SUB-SURFACE WATER FROM 2003-2017 IN THE GRIS AND CHANGES IN SURFACE HEIGHT OVER TIME DUE TO CHANGES IN COMPACTION RATE FROM DENSIFICATION OR DRAINAGE. WE WOULD EXPECT A DECREASE IN SURFACE HEIGHT BECAUSE THE PRESENCE OF SUBSURFACE WATER WILL ACCELERATE THE DENSIFICATION RATE AND IN TURN INCREASE COMPACTION. IF A UNIQUE SIGNAL IS FOUND RELATING THE SURFACE HEIGHT AND COMPACTION WE CAN INVESTIGATE PAST PRESENT AND FUTURE AREAS OF FIRN AQUIFERS. THIS RESEARCH WILL EXPLORE THE EXTENT AND EFFECTS OF SUBSURFACE WATER FOR A BETTER UNDERSTANDING OF THE OVERALL MASS BALANCE AND STABILITY OF THE GRIS IN A RAPIDLY CHANGING CLIMATE.