Detection of marine methane emissions with AVIRIS band ratios

The relative source contributions of methane (CH4) have high uncertainty, creating a need for local‐scale characterization in concert with global satellite measurements. However, efforts towards methane plume imaging have yet to provide convincing results for concentrated sources. Although atmospheric CH4 mapping did not motivate the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) design, recent studies suggest its potential for studying concentrated CH4 sources such as the Coal Oil Point (COP) seep field (∼0.015 Tg CH4 yr−1) offshore Santa Barbara, California. In this study, we developed a band ratio approach on high glint COP AVIRIS data and demonstrate the first successful local‐scale remote sensing mapping of natural atmospheric CH4 plumes. Plume origins closely matched surface and sonar‐derived seepage distributions, with plume characteristics consistent with wind advection. Imaging spectrometer data may also be useful for high spatial‐resolution characterization of concentrated, globally‐significant CH4 emissions from offshore platforms and cattle feedlots. Key Points Development of AVIRIS band ratio technique for methane anomaly identification Detection of atmospheric methane plumes from marine hydrocarbon seepage Comparison with sonar and flux data, potential to apply to other CH4 sources