Measurements of methane concentrations and isotopic ratios from the atmosphere via equipment aboard supply aircrafts operating between Christchurch, New Zealand and McMurdo Sound

The atmospheric trace gas, methane (CH4), affects the radiative heat balance of the earth. Measurements of the carbon and hydrogen isotopes in atmospheric methane are used to relate this climatically important greenhouse gas to its sources. An important part of this work is to determine the variation with height and latitude in the very clean air south of New Zealand to determine the transport of methane from the northern hemisphere. Large whole air samples (1000-1400 litres) were collected from a compressor system aboard the supply aircrafts operating between Christchurch and McMurdo (Hercules – C130, Starlifter – C141 and the Globemaster - C17). Samples were analysed for methane concentrations and the isotopic ratios of 14C and 13C. The use of different aircrafts offers the ability to measure the vertical distribution of methane and the isotopic ratios within the troposphere and stratosphere along a latitudinal transect.