We are carrying out measurements of atmospheric composition over the Arctic Ocean on R/V Mirai, aiming to clarify the dynamics and influence of atmospheric gases and aerosols related to the Arctic climate change.
Particularly, our major focus is on black carbon (BC) particles, contributing to global warming by absorbing solar radiation. Other species such as carbon monoxide (CO) and ozone (O3), are also simultaneously measured. It is pointed out that BC not only heats the atmosphere but also deposits on snow and sea ice to increase light absorption and promote their melting. In the Arctic, however, there were few data over the ocean. Therefore, we have acquired data from summer to autumn for four years from 2014 to 2017, during the Arctic research cruises on R/V Mirai. As a result, we found that the atmospheric concentration of BC over the ocean were considerably lower than the values reported on land. From the current MR18-05C cruise, we are expecting new observation results in a different season, namely, in autumn to winter.
For continuous observations of atmospheric composition on the vessel, instruments are installed in a top-floor room to which air is drawn from the outside. Also, air samplers are installed on the compass deck to collect aerosol particles directly onto filters. The air samplers are only run in the case of headwind, in order to avoid the influence of exhaust from the rear side of the ship. Chemical composition of the particles will be analyzed in detail after the cruise; from their variations, origins and transport processes of BC will be elucidated. Filter sampling schedule is planned with reference to the “chemical weather forecast” of BC and CO, which are derived from atmospheric chemical transport model simulations and are sent from land every day as support information.
Fumikazu Taketani and Chunmao Zhu(JAMSTEC)