THIS PROJECT WILL APPLY AN INNOVATIVE SATELLITE DATA DRIVEN TERRESTRIAL CARBON FLUX (TCF) MODEL FRAMEWORK SUPPORTED BY DETAILED BIOPHYSICAL PROCESS MEASUREMENTS IN CONJUNCTION WITH ATMOSPHERIC INVERSE MODELING TO IMPROVE UNDERSTANDING OF CARBON (CO2 AND CH4) DYNAMICS AND THE ENVIRONMENTAL CONTROLS ON NORTHERN ECOSYSTEM CARBON BUDGETS. AT PRESENT IT REMAINS HIGHLY UNCERTAIN IF LENGTHENING GROWING SEASONS AND INCREASES IN VEGETATION PRODUCTIVITY WILL OFFSET HEIGHTENED PLANT AND SOIL RESPIRATION OCCURRING WITH HIGH LATITUDE WARMING. ALSO UNCERTAIN IS THE IMPACT OF AUTUMN AND WINTER CO2 RELEASE AND WETLAND CH4 EMISSIONS ON ANNUAL CARBON BUDGETS. THIS STUDY WILL EXPLORE AND QUANTIFY LINKAGES BETWEEN CHANGING TERRESTRIAL CARBON FLUXES LANDSCAPE THERMAL AND MOISTURE CONDITIONS AND DISTURBANCE EVENTS OVER ARCTIC-BOREAL ECOSYSTEMS IN ALASKA AND NORTHWEST CANADA. THIS WILL BE MADE POSSIBLE THROUGH A SUITE OF OBSERVATIONS FROM TOWER EDDY COVARIANCE SITES NEW MEASUREMENTS OF WINTER SOIL CO2 RESPIRATION ATMOSPHERIC CO2 AND CH4 MEASUREMENTS FROM THE NASA CARBON IN THE ARCTIC RESERVOIRS VULNERABILITY EXPERIMENT (CARVE) SATELLITE OPTICAL-INFRARED AND MICROWAVE REMOTE SENSING RETRIEVALS AND IMPROVED RESOLUTION REANALYSIS PRODUCTS. THE TCF MODEL WILL BE ENHANCED FOR NORTHERN TUNDRA AND BOREAL REGIONS TO IMPROVE ECOSYSTEM RESPIRATION RESPONSE UNDER AUTUMN AND WINTER COLD TEMPERATURE CONDITIONS. THE ALGORITHM IMPROVEMENTS WILL BE INFORMED USING A NEW NASA ARCTIC BOREAL VULNERABILITY EXPERIMENT (ABOVE) NETWORK OF WINTER SOIL CO2 FLUX OBSERVATIONS. THE UPDATED TCF MODEL WILL BE USED TO GENERATE A 16-YR (2003-2018) BASELINE RECORD OF DAILY VEGETATION GROSS PRIMARY PRODUCTIVITY (GPP) ECOSYSTEM RESPIRATION (RECO) NET ECOSYSTEM CO2 EXCHANGE (NEE) AND WETLAND CH4 EMISSIONS AT A 1-KM RESOLUTION. A SERIES OF ALTERNATIVE 500-M FLUX SIMULATIONS WILL ALSO BE PROVIDED USING 3-KM FIELDS FROM THE POLAR WEATHER RESEARCH AND FORECASTING (POLAR-WRF) MODEL AND IMPROVED RESOLUTION MICROWAVE SURFACE FREEZE/THAW SOIL MOISTURE AND INUNDATION RETRIEVALS. THE BOTTOM-UP 1-KM AND 500-M ECOSYSTEM CARBON FLUXES WILL BE USED AS PRIORS IN REGIONAL ATMOSPHERE MODEL INVERSIONS TO ASSESS TERRESTRIAL CARBON SOURCE AND SINK ACTIVITY ACROSS THE ABOVE DOMAIN. THIS WILL BE ACHIEVED USING THE WEATHER RESEARCH AND FORECASTING-STOCHASTIC TIME-INVERTED LAGRANGIAN TRANSPORT (WRF-STILT) AND GEOSTATISTICAL INVERSE MODELING (GIM) FRAMEWORK IN CONJUNCTION WITH CO2 AND CH4 CONCENTRATION MEASUREMENTS OBTAINED FROM CARVE FLIGHTS AND TALL TOWERS. THE STILT/GIM ANALYSES WILL BE USED AS PROGNOSTIC AND CORRECTIVE TOOLS TO EVALUATE THE ABILITY OF MODEL FLUX MAPS TO REPRESENT SPATIAL PATTERNS OBSERVED IN REGIONAL ATMOSPHERIC CONCENTRATIONS. PRODUCTS RESULTING FROM THIS STUDY WILL INCLUDE A 16-YEAR RECORD OF CARBON FLUXES AND BUDGETS FOR THE NASA ABOVE DOMAIN AT A 1-KM RESOLUTION AND ALTERNATIVE 500-M RECORDS FOR ALASKA OVER THE 2013-2015 POLAR-WRF OBSERVATION PERIOD. TREND MAPS AND ANALYSIS OF UNDERLYING ENVIRONMENTAL CONDITIONS DRIVING SHIFTS IN CARBON FLUX PATTERNS AND BUDGETS WILL ALSO BE PROVIDED FOR ALASKA AND THE ABOVE DOMAIN. RESULTING DATA WILL BE MADE AVAILABLE FROM THE WOODS HOLE RESEARCH CENTER AND ARCHIVED AT THE OAK RIDGE NATIONAL LAB (ORNL) DISTRIBUTED ACTIVE ARCHIVE CENTER IN ACCORDANCE WITH NASA GUIDELINES. THIS STUDY TARGETS THE CARBON CYCLE AND ECOSYSTEM FOCUS AREA IN THIS SOLICITATION BY IMPROVING UNDERSTANDING OF CARBON BUDGETS CARBON CYCLE PROCESSES AND ECOSYSTEM VULNERABILITY TO CHANGING WATER AND ENERGY CYCLES OCCURRING IN ARCTIC-BOREAL SYSTEMS. THIS STUDY WILL CONTRIBUTE TO MODEL BENCHMARKING ACTIVITIES THAT INFORM SCIENCE RESEARCH NEEDS FOR NASA INCLUDING THE ABOVE SOIL MOISTURE ACTIVE PASSIVE (SMAP) AND SURFACE WATER&OCEAN TOPOGRAPHY (SWOT) MISSIONS.