Impact of Horizontal Resolution on Simulating Eddy-Induced Meridional Heat Transport in the Southeast Indian Ocean

The eddy-induced meridional heat transport (EMHT) in the Southeast Indian Ocean (SEIO) plays a crucial role in regional air-sea interactions and climate changes, but it is commonly underestimated in widely-known models and reanalysis data sets. This study uses three experiments of the Regional Ocean Modeling System (ROMS) with varying horizontal resolutions to assess their impact on simulating EMHT in the SEIO. The results show that increasing horizontal resolution enhances the simulated EMHT with a stronger seasonal cycle. The higher horizontal resolution experiments show improvements in the association and phase difference between high-frequency temperature and meridional velocity, both of which are the definition of EMHT. According to turbulent diffusion theory, the magnitude of EMHT is directly correlated with eddy kinetic energy (EKE). Both of them show similar vertical and temporal variations as well as spatial patterns. EKE budget analysis suggests that the improvement in EKE is primarily attributed to the enhanced baroclinic energy conversion, which indicates the EKE originated from eddy available potential energy. It is further found that the amplitude and number of mesoscale eddies are notably large in high-resolution experiments, thereby augmenting the EKE and EMHT. Additionally, the seasonal variation in EMHT in each model experiment is tied to the number of mesoscale eddies, rather than other characteristics of them. Thus, this study provides a valuable insight into the enhancing horizontal resolution to improve the simulation of EMHT.