Long-term variations in ocean acidification indices in the Northwest Pacific from 1993 to 2018

• Published in: Climatic Change
• Main Authors: Ishizu, Miho, Miyazawa, Yasumasa, Guo, Xinyu
• Other Authors: Sasakawa Peace Foundation, Japan Agency for Marine-Earth Science and Technology
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Science and Business Media LLC 2021
• Subjects: Atmospheric Science; Global and Planetary Change; Pacific; Ocean acidification; Subarctic
• Online Access: http://dx.doi.org/10.1007/s10584-021-03239-1; https://link.springer.com/content/pdf/10.1007/s10584-021-03239-1.pdf; https://link.springer.com/article/10.1007/s10584-021-03239-1/fulltext.html

Abstract Long-term variations in ocean acidification indices in the Northwest Pacific were examined using observational data and a biogeochemical model with an operational ocean model product for the period 1993–2018. The model and observational data for the surface ocean (< 100-m depth) exhibit consistent patterns of ocean acidification in the subtropical and Kuroshio Extension regions and relative alkalinization (i.e., reduced acidification) in the subarctic region of the Northwest Pacific. Below 100-m depth, acidification dominated in the subtropical regions and alkalinization in the subarctic regions. We attribute the excess acidification in the subtropical and Kuroshio regions to the vertical mixing of dissolved inorganic carbon (DIC) exceeding the DIC release by air–sea exchange. These regional differences in acidification and alkalinization are attributed to spatially variable biological processes in the upper ocean and horizontal and vertical physical redistribution of DIC. Our model and observational results have implications for the spatial extent and pattern of ocean acidification, along with the strength of the ocean carbon sink, which are key aspects of global climate change.