Zonal current structure of the Indian Ocean in CMIP6 models

The Indian Ocean circulation system significantly affects local and global climate, with zonal currents as one of the most critical components. Zonal currents bridge the water mass and energy pathways between the eastern and western Indian Oceans. Nevertheless, their representation in the latest generation of coupled climate models has not been thoroughly evaluated. In this study, we examined the representation of the mean structure of the Indian Ocean zonal currents in 29 models from the Coupled Model Intercomparison Project Phase 6 (CMIP6). We confirmed that the CMIP6 ensemble represents the Indian Ocean zonal current structure but with a shallower Equatorial Undercurrent (EUC) core and an overestimated South Equatorial Current (SEC). Further, we investigated the physical properties in the Indian Ocean to understand simulated biases and inter-model spread in CMIP6 models, and found that the simulated biases of zonal currents are accompanied by hydrography and wind forcing simulation biases. This study compares the performance of CMIP6 models for simulating the Indian Ocean zonal currents and provides a reference for further studies on the Indian Ocean circulation system using coupled climate models.