Quantifying Deep Ocean Methane Along the Central Chilean Margin

Cold seeps are dynamic seafloor environments that provide conduits for methane (CH 4 ) to be transferred from marine sediments to the global ocean and, in shallow settings, the atmosphere. These seeps are ubiquitous along continental margins yet their spatial extent and impact on the marine carbon cycle are poorly constrained. During a research expedition to the underexplored Chilean Margin, we utilized an ROV‐mounted in situ CH 4 sensor and multibeam sonar to map seep fields. We confirmed seepage at depths between 100 and 2,750 m at El Quisco Seep Site, Concepción Methane Seep Area, and Mocha Island Seep Area. Combining ship‐based and ROV‐based acoustic gas flare detection with real‐time dissolved CH 4 measurements three different manifestations of CH 4 seepage were identified, which enabled estimations of both sediment‐seawater gaseous CH 4 flux (69.2 ± 11.2 t/yr) and near‐seafloor dissolved CH 4 storage (1.9 ± 1.3 t) along the central Chilean Margin.