Airborne measurements indicate large methane emissions from the Eastern Amazon Basin

Recent results from laboratory, field and remote sensing measurements suggest the presence of large methane emissions from the Amazon basin. In this talk, we will present regionally integrative, direct trace gas observations from two sites that confirm the presence of large fluxes of methane in eastern Amazonia. Air samples collected on aircraft near Santarem (2.9 deg. S, 55.0 deg W) and Manaus (2.6 deg S, 60.0 deg W) in eastern and central Amazonia show large enhancements of CH4 that are not seen at the NOAA/ESRL background sites in the tropical Atlantic Ocean. From the surface to about four km, enhancements averaging 34 ppb and up to 200 ppb occur throughout the year. Based on data from 2000 - 2007, we calculate emissions averaging 27 mg CH4/m2/day from upwind sources. This estimate is substantially larger than "bottom- up" source estimates for individual sources likely to be contributors. Our measurements represent a substantial gradient between South America and adjacent oceans and a tropical bulge in the global north-south methane gradient that are not captured by sampling sites in the marine boundary layer.