Analysis of future changes in surface ocean pH around the Korean Peninsula using CMIP6 model results

In this study, we examined future changes in surface ocean pH around the Korean Peninsula using results from five Earth system models participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6). Analysis of the present-day period (1995 ~ 2014) revealed small inter-model deviations, with pH trends closely matching those of observation-based reconstructions. Projections of future pH under different Shared Socioeconomic Pathway (SSP) scenarios indicated that higher greenhouse gas emissions lead to more significant pH reductions. In particular, under the SSP5-8.5 scenario, pH is projected to decrease by approximately 0.47 units by 2100 relative to the historical period. Furthermore, pH is expected to decline more rapidly in the late 21st century compared to the historical period, with ocean acidification progressing somewhat faster than the global average. In addition to this pH decline, the seasonal amplitude of pH is projected to decrease by around 43.8%, with lower values in winter and higher values in summer. We also explored future changes in the seasonality of factors influencing pH, such as sea surface temperature (SST), dissolved inorganic carbon (DIC), and total alkalinity (TA). While SST showed no significant changes, DIC exhibited a distinct seasonal amplitude increase of approximately 26.4% compared to the historical period, with increases in winter and decreases in summer. This change in DIC seasonality appears to be closely related to the reduced seasonal amplitude of pH.