CLOSING THE METHANE BUDGET FOR THE US CORN BELT AND UPPER MIDWEST

WE PROPOSE A RESEARCH PROGRAM TO ADVANCE SCIENTIFIC UNDERSTANDING AND PREDICTABILITY OF METHANE EMISSIONS FROM THE US CORN BELT AND UPPER MIDWEST. THIS REGION IS CRITICAL TO THE METHANE BUDGET AS ONE OF THE MOST INTENSIVELY MANAGED LANDSCAPES IN THE WORLD AND A GLOBAL HOTSPOT FOR CROP AND ANIMAL AGRICULTURE. IT ALSO INCLUDES SOME OF THE MOST WETLAND-RICH AREAS IN THE COTERMINOUS US ALONG WITH MAJOR URBAN AND ANTHROPOGENIC EMISSIONS. SEVERAL FUNDAMENTAL ISSUES PREVENT ACCURATE QUANTIFICATION OF METHANE SOURCES FROM THIS REGION AND COMPROMISE PROJECTIONS OF HOW THOSE SOURCES MAY CHANGE. - WETLANDS ARE THE LARGEST SOURCE OF METHANE GLOBALLY BUT CURRENT GLOBAL MODELS LACK A REALISTIC PROCESS-BASED TREATMENT OF THESE EMISSIONS AND FAIL TO CAPTURE THEIR SPATIAL EXTENT. - RIVERS AND STREAMS HAVE DEMONSTRATED ELEVATED METHANE EMISSIONS IN AGRICULTURAL REGIONS BUT THIS PROCESS HAS NOT BEEN QUANTIFIED OR INTEGRATED INTO BOTTOM-UP INVENTORIES. - BOTTOM-UP INVENTORIES OF ANIMAL METHANE FLUXES ARE UNCERTAIN DUE TO SPARSE MEASUREMENTS AND LACK OF INFORMATION ON THE MAGNITUDE AND VARIABILITY OF DIFFERENT SOURCES (ENTERIC FERMENTATION IN DAIRY AND BEEF CATTLE GRAZING VS. NON-GRAZING SOLID VS. LIQUID MANURE STORAGE ETC.). - HETEROGENEITY IN THE ABOVE SOURCES POSES A SCALING CHALLENGE. THE RELATIVE IMPORTANCE OF WETLANDS AGRICULTURE AND OTHER ANTHROPOGENIC SOURCES TO THE OVERALL METHANE BUDGET IS THUS POORLY KNOWN POSING A BARRIER TO ANY MITIGATION PLANNING. THIS INTERDISCIPLINARY PROJECT WILL ADVANCE THE RESOLUTION OF THE ABOVE ISSUES. WE WILL COMBINE IN-SITU AND REMOTE SENSING AGRICULTURAL SCIENCE HYDROLOGY AND MICROMETEOROLOGY WITH FORWARD AND INVERSE MODELING IN A MULTI-SCALE APPROACH TO ADDRESS THE FOLLOWING QUESTIONS: A) WHAT IS THE NET METHANE FLUX IN THE US CORN BELT AND UPPER MIDWEST? HOW DOES IT VARY SEASONALLY? B) WHAT ARE THE MAGNITUDES SEASONALITIES AND PROCESS CONTROLS ON METHANE FLUXES FROM WETLANDS RIVERS AND STREAMS? C) HOW MUCH METHANE IS EMITTED FROM ENTERIC FERMENTATION (BARN AND GRAZING CONDITIONS) MANURE MANAGEMENT SYSTEMS AND OTHER KEY COMPONENTS OF ANIMAL AGRICULTURE? D) WHAT IS THE CONTRIBUTION OF OTHER ANTHROPOGENIC SOURCES TO THE REGIONAL METHANE BUDGET? SPECIFIC TASKS TO BE UNDERTAKEN INCLUDE THE FOLLOWING: 1) ANALYSIS OF OUR ONGOING LONG-TERM WETLAND METHANE FLUX MEASUREMENTS ASSOCIATED ECOLOGICAL DATA AND NEW RIVER- AND STREAM-BASED OBSERVATIONS TO QUANTIFY THE UNDERLYING HYDROLOGIC AND ENVIRONMENTAL FACTORS THAT DRIVE SEASONAL EMISSIONS. 2) NEW AGRICULTURAL MEASUREMENTS TO CONSTRAIN THE METHANE SOURCE FROM REPRESENTATIVE FACILITY TYPES FOR DAIRY AND BEEF CATTLE FARMS. 3) AIRBORNE MEASUREMENTS TO CHARACTERIZE THE REGIONAL METHANE DISTRIBUTION AND MAJOR SOURCES INCLUDING WETLANDS AGRICULTURE AND OTHER ANTHROPOGENIC SOURCES. 4) COUPLING OF SATELLITE REMOTE SENSING WITH ONGOING TALL TOWER MEASUREMENTS AND AIRBORNE DATA FROM TASK 3 IN A MULTI-PRONGED INVERSION FRAMEWORK TO INTEGRATE AND OPTIMIZE THE BOTTOM-UP METHANE SOURCE ESTIMATES DERIVED ABOVE. CONSTRAINTS FROM THIS WORK WILL ADVANCE KNOWLEDGE OF METHANE EMISSIONS FROM THIS UNDERSTUDIED REGION THAT IS CRUCIAL TO THE OVERALL US METHANE BUDGET. IT WILL ALSO INFORM OUR MECHANISTIC UNDERSTANDING OF THE METHANE SOURCE TYPES THAT ARE MOST IMPORTANT IN A GLOBAL CONTEXT. THE PROPOSED RESEARCH DIRECTLY ADDRESSES CENTRAL GOALS FOR THIS NASA SOLICITATION INCLUDING IMPROVED UNDERSTANDING OF THE PROCESSES SOURCE TYPES AND FLUXES RESPONSIBLE FOR NATURAL AND ANTHROPOGENIC METHANE EMISSIONS AND EMISSION TRENDS INTEGRATION OF TOP-DOWN AND BOTTOM-UP APPROACHES TO OBTAIN A BETTER UNDERSTANDING OF THE PROCESSES CONTROLLING METHANE SOURCES AND ANALYTICAL APPROACHES FOR SEPARATING THE CONTRIBUTIONS AND POSSIBLE INTERACTIONS OF MANAGED VERSUS UNMANAGED ECOSYSTEMS TO OVERALL METHANE EMISSIONS. AS PRIORITIZED IN THE RFA THE WORK MAKES SIGNIFICANT USE OF SPACE-BASED DATA ALONG WITH OTHER NASA-PRODUCED DATASETS.