Methane plume in Atlantic Ocean in 2014, sonar image. Split-beam (EK60) sonar image of bubbles (green) in the water column at a seep site overlooking Baltimore Canyon near the US Atlantic coast. Although the bubbles appear to nearly reach the sea surface, the methane contained in the bubbles would have dissolved and been replaced by other gases by the time the bubbles had risen the several hundred metres. Since 2012, images such as these have led to the discovery of hundreds of methane seeps in an area previously thought to be devoid of such leakage. When methane reaches the atmosphere, it contributes to global warming.