LOADING AND UNLOADING AT THE EARTH'S SURFACE IS AN IMPORTANT PROCESS THAT CAUSES DEFORMATION IN THE MANTLE AND CRUST AND TO THE EARTH'S SURFACE AS WELL. BECAUSE THE DEFORMATION IS SENSITIVE TO MANTLE AND LITHOSPHERIC RHEOLOGY OR VISCOSITY THE LOADING PROCESSES HAVE BEEN STUDIED EXTENSIVELY TO LEARN ABOUT THE VISCOSITY THAT IS IMPORTANT FOR DYNAMIC PROCESSES IN THE MANTLE INCLUDING MANTLE CONVECTION [E.G. WATTS 2001J. ONE OF THE BEST-KNOWN SUCH EXAMPLES IS GLACIATION AND DE-GLACIATION FOR THE LAST 100 000 YEARS AND THIS PROCESS HAS CAUSED SIGNIFICANT SURFACE DEFORMATION AND CHANGES IN SEA-LEVEL GRAVITY AND OTHER GEOPHYSICAL OBSERVABLES. STUDIES OF THIS LOADING PROCESS (I.E. GLACIAL ISOSTATIC ADJUSTMENT OR GIA) HAVE PLACED CONSTRAINTS ON THE VISCOSITY OF THE MANTLE AND GLACIATION/ DE-GLACIATION HISTORY AND PROVIDED EXPLANATIONS TO THE GIA OBSERVATIONS [PELTIER ET AL. 2015; SIMONS AND HAGER 1997; MITROVICA AND FORTE 2004J. THE MAIN OBJECTIVES OF THIS PROJECT ARE: 1) TO UNDERSTAND THE EFFECTS OF REALISTIC TEMPERATURE- AND STRESS-DEPENDENT (I.E. 3-D) MANTLE VISCOSITY ON THE GIA PROCESS 2) TO CONSTRUCT REFERENCE GIA MODELS WITH 3-D MANTLE VISCOSITY BY FITTING GEOLOGICAL AND GEODETIC OBSERVATIONS 3) TO UNDERSTAND THE POSSIBLE DYNAMIC INTERACTION BETWEEN SURFACE LOADING PROCESS AND MANTLE PROCESS INCLUDING DISSIPATIVE HEATING. THESE OBJECTIVES ARE CLOSELY RELATED TO THE SOLICITATION OF THIS EARTH SURFACE AND INTERIOR PROGRAM AND NASA GENERAL SCIENCE GOAL. FIVE TASKS ARE PROPOSED TO ACCOMPLISH OUR OBJECTIVES VIA REALISTIC AND SOPHISTICATED ANALYTICAL AND LARGE-SCALE NUMERICAL MODELING. TO EXPLORE THE EFFECTS OF 3-D MANTLE VISCOSITY ON THE GIA PROCESS USING NEW SEISMIC MODELS IN A DEPTH- AND TEMPERATURE-DEPENDENT MANTLE VISCOSITY MODEL AND PARTICULARLY TO TEST THE 1-D AVERAGE VISCOSITY MODEL HYPOTHESIS AND TO EXAMINE THE CHARACTERISTIC 3-D EFFECTS AT FAR-FIELD SITES (E.G. BARBADOS CARIBBEAN) AND IN ANTARCTICA. TO FORMULATE GIA MODELS WITH STRESS-DEPENDENT MANTLE VISCOSITY INCLUDING BOTH ICE-LOAD-INDUCED STRESS AND MANTLE BACKGROUND STRESS DUE TO MANTLE CONVECTION AND TO TEST THE HYPOTHESIS THAT BOTH ICE-LOAD-INDUCED STRESS AND MANTLE BACKGROUND STRESS SIGNIFICANTLY AFFECT THE GIA PROCESS DUE TO STRESS-DEPENDENT VISCOSITY. TO FORMULATE NEW STANDARD GIA MODELS WITH 3-D VISCOSITY STRUCTURE THAT EXPLAIN GIA RELATED OBSERVATIONS AND HELP INTERPRET NON- GIA RELATED GRAVITY CHANGE IN THE GRACE DATA. TO DEVELOP GENERAL UNDERSTANDING ON THE RELATIONSHIP BETWEEN SURFACE LOADING AND INTERNAL DEFORMATION AND DISSIPATIVE ENERGY IN THE MANTLE AND TO ASSESS POSSIBLE DYNAMIC FEEDBACK BETWEEN THE LOADING PROCESS AND MANTLE PROCESS. TO RE-PROGRAM PARALLEL COMPUTING ROUTINES FOR VISCOELASTIC LOADING CODE CITCOMSVE FOR MASSIVELY PARALLEL COMPUTING AND TO MAKE THE CODE PUBLICALLY AVAILABLE TO SCIENCE COMMUNITY.