Spatial distribution of CO2, CH4, and N2O in the Pacific sector of the Southern Ocean and the Amundsen Sea

Continuous increase of CO2, CH4, and N2O in the atmosphere is the dominant driving force to change in the global climate. The ocean plays a wide range of role in the budget of these gases in the atmosphere: as a sink for CO2 and a source for CH4 and N2O. High latitude of the Southern Ocean is particularly important as the change in the cryosphere can impact the ecological and physical settings that govern the content and flux of dissolved gases in seawater. We have visited the Pacific sector of the Southern Ocean and the Amundsen Sea during the austral summer between 2009 and 2012 to investigate the impact of the change in the cryospheric environments. In the open ocean, CO2 in the seawater was mostly undersaturated while N2O and CH4 were supersaturated with respect to that in the marine boundary layer. These typical features were not observed in the sea-ice region; CO2 in the seawater was supersaturated in 2011, but not in 2012, and CH4 in the seawater was undersaturated while dissolved N2O was supersaturated for both years. In the polynya of the Amundsen Sea, CO2 and CH4 were depleted in the seawater while dissolved N2O was supersaturated with respect to that in the atmosphere. Based on these 3-year observations during austral summer season, high latitude of the southern ocean contributes as a sink for atmospheric CO2 whilst as a source for N2O. In the case of CH4, its emission to the atmosphere is weak in the open ocean, while the sea-ice region and the polynya act as a sink.