Quantifying the contribution of human activities to marine heatwaves around the Korean Peninsula using the WRF-ROMS regional coupled model

Marine heatwaves (MHWs), prolonged periods of abnormally high ocean temperature, have more than doubled globally since the 1980s, with their frequency and intensity projected to increase further due to global warming, according to the Special Report on Ocean and Cryosphere in a Change Climate (SROCC). In particular, the Korean Peninsula has experienced noticeably more frequent and intense MHWs in recent years amidst ongoing climate change. To improve our understanding of these changes, this study quantitatively investigates the impact of human activities on the MHWs around the Korean Peninsula using Weather Research and Forecasting (WRF) and Regional Ocean Modeling System (ROMS) regional coupled models. To achieve this, we conduct control (CTL) and pseudo-NAT (NAT) experiments. The CTL experiment uses reanalysis data as the initial and boundary conditions of WRF and ROMS models. In contrast, the NAT experiment uses reanalysis data with anthropogenic influences removed. Anthropogenic influences are estimated as the difference between the Coupled Model Intercomparison Project Phase 6 (CMIP6) hist-nat simulation with natural forcing only and historical simulation with both natural and anthropogenic forcing over 1985–2014. Although the WRF and ROMS models tend to underestimate sea surface temperatures, they reasonably capture their spatial patterns, with higher temperatures in the order of Jeju Island, the South Sea, the West Sea, and the East Sea. Our findings reveal that anthropogenic forcing raised SSTs by approximately 0.3 to 0.6°C in the major waters of Korea. As a result, the frequency, intensity, duration, and spatial extent of MHWs have significantly increased in the major waters of Korea. These results highlight the critical role of human activities in driving recent changes in MHW characteristics around the Korean Peninsula and underscore the importance of mitigating anthropogenic climate change impacts.