THIS PROPOSAL ADDRESSES ABOVE PHASE 2 RESEARCH TO DEVELOP DATA PRODUCTS TO IMPROVE UNDERSTANDING OF ECOSYSTEM DYNAMICS USING REMOTE SENSING DATA COLLECTED DURING THE 2017 AIRBORNE CAMPAIGN. WE WILL QUANTIFY PERMAFROST ACTIVE LAYER PATTERNS SEASONAL VARIATIONS AND RECENT TRENDS ACROSS ALASKA AND NORTHWEST CANADA. WE WILL ALSO CLARIFY IMPACTS FROM RECENT CLIMATE CHANGE AND DISTURBANCE ON ACTIVE LAYER CHANGES. WE WILL ACCOMPLISH THESE OBJECTIVES USING AN ITERATIVE SPATIALLY NESTED ANALYSIS AND DATA-DRIVEN MODELING FRAMEWORK INTEGRATING FIELD MEASUREMENTS LOCAL (50M) SCALE ACTIVE LAYER RETRIEVALS FROM AIRBORNE RADAR AND LANDSCAPE (1KM) SCALE ASSESSMENTS DERIVED FROM THE RECENT SATELLITE RECORD (2000-PRESENT). ..WE WILL DEVELOP NEW REMOTE SENSING ALGORITHMS AND RETRIEVALS OF PERMAFROST ACTIVE LAYER CONDITIONS USING FOUNDATIONAL UAVSAR AND AIRMOSS LOW FREQUENCY (L+P-BAND) AIRBORNE RADAR BACKSCATTER DATA FROM THE ABOVE. RADAR ALGORITHMS WILL BE RUN ITERATIVELY WITH THE SOIL PROCESS MODEL TO HARMONIZE AND OPTIMIZE KEY PHYSICAL PARAMETERS COMMON TO BOTH APPROACHES. THE COUPLED RADAR AND SOIL MODEL FRAMEWORK WILL HELP RESOLVE THE UNDERDETERMINED NATURE OF THE RADAR INVERSIONS WHILE ENHANCING REGIONAL ACCURACY AND CONSISTENCY. RADAR AND SOIL MODEL OUTPUTS WILL BE ANALYZED WITH FIELD MEASUREMENTS AND OTHER GEOSPATIAL DATA TO CLARIFY HOW VARIATIONS IN CLIMATE SOIL VEGETATION AND TOPOGRAPHY ARE INTERACTIVE IN CONTROLLING ACTIVE LAYER TRENDS. THE NESTED MODEL AND DATA ANALYSIS FRAMEWORK WILL DEFINE SCALING FUNCTIONS LINKING LOCAL SCALE INFORMATION DERIVED FROM THE DETAILED FIELD STUDIES AND AIRBORNE CAMPAIGNS WITH COARSER LANDSCAPE ASSESSMENTS DERIVED FROM A GLOBAL SATELLITE-DRIVEN SOIL PROCESS MODEL. RESULTING GEOSPATIAL OUTPUTS WILL INCLUDE ACTIVE LAYER SOIL MOISTURE AND FREEZE-THAW PROFILES WHICH ARE DRIVING FACTORS AFFECTING>30% OF GLOBAL SOIL ORGANIC CARBON VULNERABLE TO DECOMPOSITION AND RELEASE FROM PERMAFROST SOILS UNDER GLOBAL WARMING. ..THE SOIL PROCESS MODEL INFORMED BY THE LOCAL SCALE AIRBORNE ANALYSIS WILL BE USED FOR EXTRAPOLATING ACTIVE LAYER CONDITIONS BEYOND THE LIMITED AIRBORNE ACQUISITIONS TO THE ENTIRE ABOVE DOMAIN. THE MODEL RESULTS WILL INCLUDE A CONTINUOUS (8-DAY TO ANNUAL) GEOSPATIAL RECORD OF NEAR SURFACE PERMAFROST EXTENT (PE) AND ACTIVE LAYER THAW DEPTH DYNAMICS SPANNING THE LONG-TERM SATELLITE RECORD (2000- PRESENT). PRIMARY MODEL DRIVERS WILL BE OBTAINED FROM GLOBAL SATELLITE OPTICAL-IR AND MICROWAVE SENSOR RECORDS REPRESENTING KEY ENVIRONMENTAL FACTORS INFLUENCING ACTIVE LAYER TRENDS. THESE ACTIVITIES WILL CLARIFY REGIONAL PATTERNS RECENT CHANGES AND UNDERLYING DRIVERS AFFECTING PE STABILITY AND ACTIVE LAYER DEVELOPMENT ACROSS THE DOMAIN. ..THIS PROJECT ADDRESSES THE NASA ABOVE TIER-2 SCIENCE QUESTION: "WHAT PROCESSES ARE CONTROLLING CHANGES IN PERMAFROST DISTRIBUTION AND PROPERTIES AND WHAT ARE THE IMPACTS OF THESE CHANGES?" PROJECT OUTCOMES WILL INCLUDE NEXT GENERATION REMOTE SENSING ALGORITHMS AND DEMONSTRATED TECHNICAL READINESS FOR PERMAFROST ACTIVE LAYER MONITORING FROM LOW FREQUENCY (L- P-BAND) RADARS. THIS STUDY WILL ALSO PROVIDE NEW CAPABILITIES FOR SATELLITE BASED MONITORING OF ACTIVE LAYER CHANGES ACROSS THE PAN-ARCTIC WHILE IMPROVING UNDERSTANDING OF CLIMATE AND DISTURBANCE RELATED IMPACTS ON NORTHERN PERMAFROST LANDSCAPES AND WATER-CARBON CYCLE CONNECTIONS. .