THERE IS MUCH UNCERTAINTY WITH RESPECT TO HOW SHIFTS IN CLIMATE COULD RENDER TERRESTRIAL CARBON STOCKS VULNERABLE TO CONVERSION TO ATMOSPHERIC CO2 OR LEAD TO REDUCED CARBON UPTAKE BY THE OCEAN. BY LEVERAGING THE CLIMATE-CARBON FEEDBACKS EVIDENT IN INTERANNUAL VARIABILITY IN THE ATMOSPHERIC CO2 GROWTH RATE THIS PROJECT AIMS TO EXPLORE THE PROCESSES THAT REGULATE THE RESPONSE OF THE TERRESTRIAL BIOSPHERE TO CLIMATE VARIABILITY AND CHANGE. BECAUSE MUCH OF THIS VARIABILITY IS ASSOCIATED WITH LARGE-SCALE CLIMATE OSCILLATIONS IN OCEAN BASINS WE FOCUS ON RESOLVING THE GEOGRAPHIC AND MECHANISTIC ORIGIN TO VARIABILITY IN THE ATMOSPHERIC CO2 GROWTH RATE. THIS EFFORT REQUIRES AN INTERDISCIPLINARY APPROACH AND OUR TEAM WHICH ENCOMPASSES EXPERTISE IN ATMOSPHERIC OCEAN AND TERRESTRIAL PROCESSES AS WELL AS SATELLITE REMOTE SENSING WILL ADDRESS THE FOLLOWING SCIENCE QUESTIONS: Q1. WHAT ARE THE MECHANISMS BY WHICH CO-VARYING CLIMATE FACTORS AFFECT TERRESTRIAL CARBON FLUXES? WE WILL USE TWO NOVEL APPROACHES A MULTI-LAYER CANOPY MODEL AND A SOIL BIOGEOCHEMISTRY TEST BED TO UNDERSTAND HOW MODEL STRUCTURE INFLUENCES THE FEEDBACKS BETWEEN CARBON FLUXES AND INTERANNUAL CLIMATE VARIATIONS. WE HYPOTHESIZE THAT THESE FRAMEWORKS WILL EXHIBIT GREATER INTERANNUAL VARIABILITY THAN TRADITIONAL MODELING APPROACHES WHICH SIMPLIFY CANOPY STRUCTURE ABOVEGROUND AND MICROBIAL INTERACTIONS BELOWGROUND. WE EXPECT THAT RESULTS FROM THESE SIMULATIONS CAN BE EVALUATED AGAINST NASA SATELLITE OBSERVATIONS FROM MODIS OCO-2 AND SMAP TO ELUCIDATE HOW PARAMETERIZATIONS WITHIN THE COMMUNITY EARTH SYSTEM MODEL (CESM) CAN BE MODIFIED TO BEST REPRESENT INTERANNUAL VARIABILITY. Q2. ARE SIGNALS OF VARIABILITY IN OCEAN AND LAND CO2 FLUXES DETECTABLE OUTSIDE THEIR UNCERTAINTIES IN ATMOSPHERIC CO2? UNCERTAINTY IN THE FLUX FOOTPRINT OF ATMOSPHERIC CO2 OBSERVATIONS POTENTIALLY LIMITS THE ABILITY TO ATTRIBUTE CLIMATE-DRIVEN INTERANNUAL VARIATION IN OCEAN AND LAND CO2 FLUXES. WE WILL USE MODELED LAND FLUXES AND SEVERAL NEWLY AVAILABLE OCEAN FLUX DATA PRODUCTS TO ESTIMATE THE IMPRINTS OF OCEAN CLIMATE OSCILLATIONS ON THE OBSERVED ATMOSPHERIC CO2 VARIABILITY. WE HYPOTHESIZE THAT THIS RESEARCH WILL IDENTIFY KEY REGIONS WHERE ATMOSPHERIC CO2 CONTAINS UNIQUE FINGERPRINTS FROM EITHER LAND OR OCEAN CO2 AS WELL AS REGIONS WHERE INTERPRETATION OF INTERANNUAL VARIABILITY IN CO2 REQUIRES ADDITIONAL OBSERVATIONAL CONSTRAINTS. Q3. HOW DO LARGE-SCALE CLIMATE OSCILLATIONS INFLUENCE REGIONAL CLIMATE AND TERRESTRIAL CARBON FLUXES? COUPLED OCEAN-ATMOSPHERE CLIMATE OSCILLATIONS DRIVE CHANGES IN THE TERRESTRIAL CARBON SINK BUT WE STILL LACK MECHANISTIC UNDERSTANDING. USING A COMBINATION OF MODEL SIMULATIONS WE WILL INVESTIGATE NONLINEAR INTERACTIONS BETWEEN TEMPERATURE DROUGHT STRESS FIRE AND RADIATION VARIABILITY FACTORS THAT SHOW HIGH COVARIANCE WITH CLIMATE VARIATIONS. WE HYPOTHESIZE THAT INTERACTION EFFECTS HAVE A STRONG INFLUENCE ON INTERANNUAL CARBON VARIATIONS AND THAT ACCOUNTING FOR THESE INTERACTIONS WILL HELP RECONCILE APPARENT DISCREPANCIES BETWEEN TOPDOWN STUDIES THAT SUGGEST TEMPERATURE IS A STRONG REGULATOR OF TERRESTRIAL CARBON FLUX VARIABILITY AND BOTTOM-UP STUDIES THAT SUGGEST A PREDOMINANT ROLE FOR MOISTURE. REGIONAL AND TEMPORAL VARIATIONS IN THE ATMOSPHERIC CO2 GROWTH RATE SUCH AS THOSE MEASURED BY NASA'S OCO-2 SATELLITE PROVIDE AN IMPORTANT WINDOW INTO THE INTEGRATED EFFECTS OF CLIMATE VARIABILITY ON THE GLOBAL CARBON CYCLE. BY INTEGRATING OBSERVATIONS AND MODELING ACROSS THE EARTH SYSTEM THIS PROPOSAL AIMS TO ADVANCE OUR UNDERSTANDING OF HOW TO PROPERLY INTERPRET THESE OBSERVATIONS TO QUANTIFY CLIMATE-CARBON INTERACTIONS AT BOTH INTERANNUAL TIMESCALES AND TIMESCALES CRUCIAL FOR CLIMATE PREDICTION AND ADAPTATION. THE PROPOSED RESEARCH WILL HIGHLIGHT THE SCIENTIFIC VALUE OF NASA'S BROAD SUITE OF EARTH SYSTEM OBSERVATIONS AND BROADEN THE APPLICATION OF NASA DATA FOR PROGNOSTIC CARBON CYCLE MODELING.