On December 3, 2024, Xingshang Qian, a PhD student at the School of Oceanography, Shanghai Jiao Tong University (SJTU-SOO), published a research article titled “Impact of Horizontal Resolution on Simulating Eddy-induced Meridional Heat Transport in the Southeast Indian Ocean” as the first author in Journal of Geophysical Research: Oceans. The paper was completed by Xingshang Qian (first author), Professor Lei Zhou from SJTU-SOO (corresponding author), and Associate Researcher Jianhuang Qin from the College of Oceanography, Hohai University.

Oceanic meridional heat transport is fundamental to establish the global heat balance, with the eddy-induced meridional heat transport (EMHT) contributing 20%–60% of the total oceanic meridional heat transport variance in different oceans. However, the EMHT in the Southeast Indian Ocean (SEIO) is commonly underestimated in widely-known models and reanalysis datasets (Figure 1). Therefore, 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 the D12 experiment showing EMHT values comparable to observations (Figure 1g). 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 (Figure 2).

According to turbulent diffusion theory, the magnitude of EMHT is directly correlated with eddy kinetic energy (EKE). EKE budget analysis suggests that the improvement in EKE is primarily attributed to the enhanced baroclinic instability, which is the dominant mechanism of mesoscale eddy formation. 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. Thus, this study provides a valuable insight into the enhancing horizontal resolution to improve the simulation of EMHT.

Figure 1. Temporally averaged surface eddy-induced meridional heat transport (EMHT) calculated using the (a) observations, (b) OFES, (c) SODA, (d) D12, (e) D08 and (f) D04 experiments, respectively. (g) Temporally and spatially averaged surface EMHT in the SEIO calculated using the observations and numerical models data.

Figure 7. Amplitude of cross-spectral power densities between  and  averaged in the SEIO, using data from (a) observations, (b) D12, (c) D08, and (d) D04 experiments, respectively. (e)–(h) are same as (a)–(d), but for absolute phase difference.

This work is supported by grants from the National Natural Science Foundation of China (42125601, 42106003), and the National Key Research and Development Program of China (2023YFF0805300).

Contribution: Research Group of Prof. Lei Zhou