Full latitudinal marine atmospheric measurements of iodine monoxide

14 pags., 7 figs., 4 tabs.Iodine compounds destroy ozone (O3) in the global troposphere and form new aerosols, thereby affecting the global radiative balance. However, few reports have described the latitudinal distribution of atmospheric iodine compounds. This work reports iodine monoxide (IO) measurements taken over unprecedented sampling areas from the Arctic to the Southern Hemisphere and spanning sea surface temperatures (SSTs) of approximately 0 to 31.5°C. The highest IO concentrations were observed over the Western Pacific warm pool (WPWP), where O3 minima were also measured. There, a negative correlation was found between O3 and IO mixing ratios at extremely low O3 concentrations. This correlation is not explained readily by the O3-dependent oceanic fluxes of photolabile inorganic iodine compounds, which is the dominant source in recent global-scale chemistry transport models representing iodine chemistry. Actually, the correlation rather implies that O3-independent pathways can be similarly important in the WPWP. The O3-independent fluxes result in a 15% greater O3 loss than that estimated for O3-dependent processes alone. The daily O3 loss rate related to iodine over the WPWP is as high as approximately 2ppbv (parts per billion by volume) despite low O3 concentrations of approximately 10ppbv, with the loss being up to 100% greater than that without iodine. This finding suggests that warming SST driven by climate change might affect the marine atmospheric chemical balance through iodine-ozone chemistry. Copyright:This study was supported by the KAKENHI (grant nos. 16KK0017 and 21H04933), and by the ArCS (Arctic Challenge for Sustainability; grant no. JPMXD1300000000) of the Ministry of Education, Culture, Sports, Science, and Technology of Japan. This study has also received funding from the European Research Council Executive Agency under the European Union’s Horizon 2020 Research and Innovation programme (grant no. ERC2016-COG 726349; CLIMAHAL). This study was also supported, in part, by funding from Fukuoka University (grant no. 197103).Peer reviewe