ICE SHEETS AND GLACIERS PLAY A CRUCIAL ROLE ON THE EARTH'S CLIMATE SYSTEM AFFECTING ATMOSPHERIC CIRCULATION FRESHWATER FLUXES AND CRUCIALLY SEA LEVEL CHANGE. THE SURFACE ENERGY AND MASS BALANCE IS A CRUCIAL MEDIATOR OF THESE EFFECTS AND IMPROVING THE REALISM OF THESE PROCESSES IN MODEL SIMULATIONS HAS IMPORTANT CONSEQUENCES FOR MODEL PROJECTIONS OF FUTURE CLIMATES. SPECIFICALLY CHANGES IN ALBEDO OVER TIME (SEASONALLY AND ON CLIMATE TIME SCALES) PLAY A KEY ROLE IN SURFACE MELT VARIABILITY. THE DEPOSITION OF ANTHROPOGENIC AND NATURAL AEROSOLS CAN ALSO DIRECTLY MODULATE THE SURFACE ALBEDO. FRESH SNOW ACCUMULATION INCREASES ALBEDO OVER PERMANENTLY ICE COVERED AREAS WHILE DURING SUMMER ALBEDO DECREASES AS A RESULT OF THE MELTING. IN THIS PROJECT WE PROPOSE TO INVESTIGATE THE RELATIONSHIPS BETWEEN ALBEDO AND SURFACE MASS BALANCE OVER THE GREENLAND AND ANTARCTIC ICE SHEETS AND OTHER GLACIATED AREAS OF THE GLOBE ON ATMOSPHERIC AND SURFACE MASS BALANCE. WE EXAMINE NATURAL SEASONAL VARIABILITY AND THE FORCED VARIABILITY OF FUTURE PROJECTIONS USING A NEW PHYSICALLY CONSISTENT METHOD FOR DETERMINING DYNAMIC ICE ALBEDO SCHEME IN THE NASA GISS-E2 GLOBAL CLIMATE MODEL. WE AIM AT ADDRESSING THE FOLLOWING SCIENCE QUESTIONS: WHAT IS THE RELATIONSHIP OF ALBEDO OVER THE ICE SHEETS TO ATMOSPHERIC FLUXES? HOW WELL CAN THE NASA GISS-E2 MODEL REPRODUCE EXTREME EVENTS SUCH AS THE HIGH EXTREME MELTING YEAR OF 2012 (WHEN MELTING EXTENDED UP TO 95 % OF THE ICE SHEET) AND THE LOW MELTING YEAR OF 1992 (DUE TO THE MOUNT PINATUBO ERUPTION)? WHAT IS THE IMPACT OF A DYNAMIC ALBEDO ON SURFACE MASS BALANCE AND THE ROLE OF NATURAL AND ANTHROPOGENIC AEROSOLS. UP TO RECENTLY THE BROADBAND ALBEDO FOR ICE SHEETS IN THE NASA GISS-E2 MODEL WAS STATIC AND SET TO THE OBSERVED MEAN VALUE OF 0.8 FOR ALL MONTHS AND REGIONS. THIS LIMITED THE QUALITY OF THE SIMULATION OF SURFACE MASS BALANCE QUANTITIES (SUCH AS RUNOFF MELTWATER PRODUCTION ETC.) AND OF ICE-ATMOSPHERE COUPLING. IN THIS PROJECT WE WILL MAKE USE OF A NEW ALBEDO SCHEME FOR THE NASA GISS-E2 MODEL THAT HAS BEEN DEVELOPED AND IS BEING REFINED AT NASA GISS. THIS WILL LEVERAGE CURRENT FUNDING OF POSTDOCTORAL RESEARCHER DR. ALEXANDER (NASA GISS) WHO IS EVALUATING A REGIONAL MODEL SIMULATION OF SNOW DENSITY'S MODULATION OF SURFACE ALBEDO DR. FISCHER WHO IS DEVELOPING METHODS OF COUPLING GISS-E2 AND ICE SHEET MODELS AND PI TEDESCO (LDEO COLUMBIA AND NASA GISS) WHO IS EXAMINING THE EFFECT OF LIGHT-ABSORBING IMPURITIES ON THE SNOW/ICE SURFACES AND THE EVOLUTION OF GRAIN SIZE ASSOCIATED WITH MELTING AND REFREEZING CYCLES. WE WILL ALSO USE AEROSOL DEPOSITION FROM THE MODEL TO INCLUDE THE CHANGING IMPACT OF LIGHT ABSORBING IMPURITIES IN THE NEW ALBEDO SCHEME AND THE ASSOCIATED IMPACT ON GRAIN SIZE EVOLUTION. WE WILL ALSO MAKE USE OF A SUB-GRID-SCALE SCHEME OF ELEVATION CLASSES THAT ALLOWS FOR HIGHER RESOLUTION SIMULATION OF ICE SHEET SURFACE PROCESSES ON ELEVATION CLASSES. WE WILL ASSESS THE ALBEDO SCHEME THROUGH THE COMPARISON WITH SATELLITE DATA (E.G. MODIS AVHRR) IN-SITU MEASUREMENTS RE-ANALYSIS PRODUCTS (E.G. MERRA-2) AND THE OUTPUTS OF A REGIONAL CLIMATE MODEL (E.G. MAR). MODEL SIMULATIONS WILL BE STUDIED IN COMPARISON WITH PRESENT-DAY REMOTE SENSING AND IN SITU OBSERVATIONS AND WITH THE ATMOSPHERIC OUTPUTS OF REGIONAL CLIMATE MODELS FORCED AT THE LATERAL BOUNDARIES WITH GISS-E2 OUTPUTS. WE WILL USE MODIS LAND SURFACE TEMPERATURE; MELT EXTENT AND DURATION FROM PASSIVE AND ACTIVE MICROWAVE DATA; CALIPSO AND CLOUDSAT DATA FOR CLOUD COVER VERTICAL PROFILE RADIATIVE FLUXES; CERES FOR RADIATIVE FLUXES; AIRS FOR TEMPERATURE AND WATER VAPOR PROFILES. OUR PROJECT ADDRESSES THE FOLLOWING RESEARCH THEMES 'COUPLING IN THE EARTH SYSTEM' 'EXTREMES IN EARTH SYSTEMS' AND 'CONSTITUENTS IN CLIMATE SYSTEM' AND THE FOLLOWING PROGRAMMATIC PRIORITIES: 'CHARACTERIZE AND/OR HELP REDUCE UNCERTAINTIES IN THE MODELS AND PRODUCTS' 'EXTEND THE RANGE OF MODEL OR PRODUCT VALIDITY BY USING NEW COMPONENTS'.