Source: Journal of Geophysical Research: Oceans
Both winds and tides inject energy into the ocean. Much of that energy is then transported up to thousands of miles by internal waves: large-scale underwater waves that can travel between ocean basins. Quantifying the amount of energy transported by internal waves and assessing their dynamics are difficult given their location and scale. Still, the question is important because internal wave dynamics interact with the global climate and underwater ecosystems by influencing currents, ocean mixing, and more.
Li et al. used the LLC4320 configuration of the MIT General Circulation Model to better understand meridional internal wave fluxes into and through the Southern Ocean. They broke internal wave energy into tidal, wind, and general background motion bands and assessed fluxes at latitudes from 35°S to 65°S. The modeling allowed the authors to estimate how much internal wave energy, measured in gigawatts, is brought into and exported from the Southern Ocean and to assess the effects of various bathymetric and hydrographic features on internal wave fluxes.
The net internal wave flux is poleward, the authors report, reaching approximately 15 gigawatts at 35°S and 55°S and 7 gigawatts at 45°S. The majority—more than 80%—of the internal wave flux is powered by the tides. In contrast, wind-driven waves carry just 1%–3% as much energy but move in the opposite direction—equatorward—partially offsetting the net poleward flux. The rest is accounted for by various background motions, including higher tidal harmonics, lee waves, and nonlinear interactions. Tidal motion drops precipitously at 65°S, accounting for less than half the total flux there.
Digging deeper into their data, the authors assessed the contributions of various high-energy locations throughout the Southern Ocean, including the Drake Passage and the Macquarie Ridge, which are associated with poleward and equatorward fluxes, respectively. Further, they found that energy from tidal forces is net exported from the Southern Ocean between 45°S and 55°S but is net imported in the 35°S–45°S and 55°S–56°S latitudinal bands.
This paper, the first to quantify the structure of the internal wave energy flux in the Southern Ocean, could become a reference for future observational studies. Even so, the authors point to several model shortcomings that could be addressed in future work. The model simulation length was too short to capture seasonal to interannual variability in internal wave fluxes, they say, and they were unable to distinguish between wave modes or pick out wave interference. Future improvements could include a modal decomposition and the use of wave-fitting techniques to help address these issues. (Journal of Geophysical Research: Oceans, https://doi.org/10.1029/2025JC023348, 2026)
—Nathaniel Scharping (@nathanielscharp), Science Writer
