Methane in air above water surface

Description

Mixing ratio of methane in the air above the water surface measured along a ship’s route in September 2005. The dotted line shows the Latitude-specific monthly average of 1.85 parts per million by volume established for the Barrow, Alaska, USA, monitoring station at 71° 19’ N, 156° 35’ W this is the normal level of methane in the atmosphere at this latitude.