K-ACE2: Model Overview and Evaluation of Pre-industrial Climate

Abstract The KMA Advanced Community Earth System Model version 2 (K-ACE2) is introduced and evaluated as a fully coupled Earth system model for climate simulations. K-ACE2 integrates atmospheric, oceanic, sea-ice, land, and biogeochemical processes, and its fundamental characteristics are assessed using a pre-industrial control (piControl) simulation following the CMIP6 protocol. The piControl simulation exhibits stable conditions, with a near-zero net top-of-atmosphere radiative imbalance (approximately 0.01 W m⁻²) and negligible long-term trends in key variables such as surface air temperature, sea surface temperature, and sea ice extent. These results indicate a quasi-equilibrium state. The simulated mean climate state falls within the range of the CMIP6 multi-model ensemble and reproduces the large-scale patterns of surface temperature, precipitation, and air-sea CO 2 flux. Internal variability, including the El Niño–Southern Oscillation (ENSO) and the Atlantic Meridional Overturning Circulation (AMOC), is also represented with characteristics comparable to CMIP6 models. Overall, K-ACE2 demonstrates stable and physically consistent behavior within the spread of CMIP6 models and provides information for future CMIP-related simulations and model evaluations.