Inter-annual Variability of Ocean Surface Carbonate System Parameters and Their Trends in the Pacific Ocean Since 2001

Shin-ichiro Nakaoka1, Yukihiro Nojiri2, Sayaka Yasunaka3, Tsuneo Ono4, Shintaro Takao1 and Maciej Telszewski5, (1)National Institute for Environmental Studies, Tsukuba, Japan, (2)Hirosaki University, Hirosaki, Japan, (3)Japan Agency for Marine-earth Science and Technology, Yokosuka, Japan, (4)Japan Fisheries Research and Education Agency, Yokohama, Japan, (5)Institute of Oceanology Polish Academy of Sciences, Sopot, Poland
This study produced monthly maps of the ocean surface carbonate system parameters such as dissolved inorganic carbon, pH based on the estimated distributions of the pCO2 and the total alkalinity (TA) in the Pacific Ocean after 2001. The pCO2 values were estimated using a self-organizing map neural network technique to explain the non-linear relationships between observed pCO2 data and four oceanic bio-geophysical parameters: sea surface temperature (SST), sea surface salinity (SSS), mixed layer depth (MLD), chlorophyll-a (CHL) concentration and the location. The observed pCO2 data was obtained from the international pCO2 database of the Surface Ocean CO2 Atlas version 5. The SST, SSS, MLD datasets were obtained from the Grid Point Value of the Monthly Objective Analysis using the Argo data and the satellite CHL dataset were from MODIS-Aqua and SeaWiFS Level 3 standard products. To detect the vulnerable areas for the ecosystem due to the ocean acidification in this work, we then evaluate the distributions of other carbonate system parameters during the period based on the TA estimate with the estimated pCO2 distribution using CO2SYS and show their inter-annual variability and trends.