THE ANTARCTIC ICE SHEET (AIS) IS AN INTEGRAL COMPONENT OF THE EARTH SYSTEM AT RISK OF UNDERGOING RAPID CHANGE. SOCIETALLY-RELEVANT ESTIMATES OF FUTURE SEA LEVEL RISE MANDATE UNDERSTANDING HOW THE AIS RESPONDS TO NATURAL AND ANTHROPOGENIC FORCING, PARTICULARLY ACROSS ANTARCTICA S CLIMATE-SENSITIVE ICE SHELVES. TO DATE, RESEARCH INVESTIGATING CHANGES TO ICE SHELVES HAS LARGELY FOCUSED ON THE ROLE OF THE OCEAN IN DRIVING SUBMARINE ICE SHELF MELTING. RELATIVELY LITTLE ATTENTION HAS BEEN DIRECTED TOWARDS UNDERSTANDING THE IMPACT OF OCEAN SURFACE VARIABILITY ON THE SURFACE MASS BALANCE (SMB) OF THE AIS AND ICE SHELVES. THIS LACK OF RESEARCH IS DESPITE THE CENTRAL ROLE SMB PLAYS IN TOTAL AIS MASS BALANCE, AND EMERGING (BUT STILL POORLY CONSTRAINED) LINES OF EVIDENCE POINTING TO THE POTENTIAL IMPORTANCE OF THE OCEAN SURFACE IN IMPACTING ICE SHEET SMB. GIVEN GROWING CONCERN OVER THE FUTURE OF THE AIS CENTERING ON THE BUTTRESSING ROLE OF ICE SHELVES, A BETTER UNDERSTANDING OF THE CURRENT STATE OF ICE SHELF/SHEET SMB, AS WELL AS THE MECHANISMS IN THE ICE-OCEAN-ATMOSPHERE SYSTEM IMPACTING ICE SHELF/SHEET SMB ARE PARAMOUNT. MOTIVATED BY THESE KNOWLEDGE GAPS THAT INTRODUCE UNCERTAINTY IN ESTIMATES OF 21ST CENTURY SEA LEVEL RISE, WE PROPOSE A 3-YEAR RESEARCH PROJECT THAT WILL COMBINE STATE-OF-THE-ART MEASUREMENTS DERIVED FROM EARTH-OBSERVING SATELLITES WITH NEW, HIGH-RESOLUTION REGIONAL CLIMATE MODEL EXPERIMENTS TO: (1) CONSTRAIN AIS SMB PROCESSES, INCLUDING THE MOST DETAILED OBSERVATIONS OF ANTARCTIC SURFACE MELTING TO DATE; (2) QUANTIFY THE IMPORTANCE OF ANTARCTIC SEA ICE AND OCEAN SURFACE VARIABILITY ON AIS SMB; AND (3) DEVELOP AND IMPROVE SIMULATIONS OF THE COUPLED ANTARCTIC ICE-OCEAN-ATMOSPHERE SYSTEM. SPECIFICALLY, WE WILL DEVELOP A NEW MULTI-DECADAL (1978 PRESENT), NEAR-DAILY, HIGH SPATIAL RESOLUTION (3.125 6.25 KM), SURFACE MELT DATASET DERIVED USING A NOVEL ALBEDO-INCORPORATING MELT DETECTION SCHEME. THIS APPROACH WILL BE APPLIED TO A NEWLY-RELEASED MEASURES ENHANCED-RESOLUTION PASSIVE MICROWAVE SATELLITE DATASET. WE WILL ALSO FOCUS ON UNDERSTANDING HOW VARIABILITY IN THE OCEAN SURFACE SURROUNDING ANTARCTICA (NAMELY SEA ICE AND SEA SURFACE TEMPERATURE) IMPACTS THE AVAILABILITY OF HEAT, ENERGY, AND MOISTURE, AND IN TURN, HOW THIS IMPACTS THE SMB OF COASTAL ICE SHELVES. TO ACCOMPLISH THIS TASK, WE WILL UTILIZE A SUITE OF COMPLEMENTARY ATMOSPHERIC REMOTE SENSING PRODUCTS, AUGMENTED BY A DYNAMIC DOWNSCALING OF NASA S MERRA-2 REANALYSIS AND KEY IN SITU VALIDATION SITES. TO MORE FULLY QUANTIFY THE PHYSICAL MECHANISMS UNDERLYING COVARIABILITY IN THE SEA ICE-OCEAN-ICE SHEET SYSTEM, WE PROPOSE A SUITE OF NEW, HIGH-RESOLUTION REGIONAL CLIMATE MODEL EXPERIMENTS, WHICH WILL BE PERFORMED AT NO COMPUTATIONAL COST TO THIS PROJECT. OUR FIRST EXPERIMENT IS FORCED BY THE MERRA-2 REANALYSIS AND WILL PROVIDE IMPORTANT CONTEXT FOR OUR SATELLITE OBSERVATIONS. NEXT, THREE, THIRTY-YEAR SIMULATIONS WHERE ONLY SEA ICE IS ALTERED (IN LOW, NEAR-OBSERVED, AND HIGH SEA ICE STATES) WILL ISOLATE THE SMB RESPONSE TO OCEAN SURFACE VARIABILITY. THIS SYNTHESIS OF STATE-OF-THE-ART OBSERVATIONS AND REGIONAL CLIMATE MODELING WILL IDENTIFY CRITICAL ANTARCTIC ICE-OCEAN-ATMOSPHERE CONNECTIONS AND CONSTRAIN PROJECTIONS OF FUTURE ANTARCTIC CHANGE. THIS PROPOSAL SUPPORTS THREE EARLY CAREER SCIENTISTS, A RESEARCH ASSOCIATE, TWO PHD STUDENTS WHO WILL PLAY CENTRAL ROLES IN ICE SHEET REMOTE SENSING AND CLIMATE MODELING, AND UNDERGRADUATE STUDENTS WHO WILL GAIN HANDS-ON EXPERIENCE ANALYZING POLAR CLIMATE DATA. THE PROPOSED PROJECT DIRECTLY ALIGNS WITH MANY OF THE GOALS OF NASA S EARTH SCIENCE DIVISION AND CRYOSPHERIC SCIENCE PROGRAM BY DEVELOPING A BETTER UNDERSTANDING OF AIS MASS BALANCE, ICE-OCEAN-ATMOSPHERE INTERACTIONS, AND FACILITATING MORE INFORMED PROJECTIONS OF FUTURE AIS CHANGE.