[M-ZZ42] Process, Environment, and Exploration of Marine Manganese Deposits

[MZZ42-02] Preliminary simulation of sediment plume dispersion and deposition in seamount

*Naoki Saito^1,2, Shinichiro Yano², Masayuki Nagao¹, Atsushi Suzuki¹, Hiroko Kamoshida³ (1.National Institute of Advanced Industrial Science and Technology, 2.Kyushu University, 3.Japan Organization for Metals and Energy Security)

Keywords:deep-sea mining, cobalt-rich crust, environmental impact assessment, tidal current, internal tide, numerical simulation

In recent years, mining of cobalt-rich crusts, a potential mineral resource, has been planned in seamounts. Mining can disturb seafloor sediments and generate large amounts of suspended particles, or sediment plumes, which can affect the ecosystem. However, the effects of complex currents around seamounts on plume dispersion and deposition have rarely been investigated. In this study, hydrodynamic modeling and plume dispersion and deposition simulations were conducted for Scripps Guyot, a flat-topped seamount located in the Northwest Pacific Ocean. Plume properties and mining operations were set based on measured data from a small-scale excavation test conducted on the seamount in 2020 (Saito et al. 2023 Front. Mar. Sci.; Washburn et al. 2023 Curr. Biol.). Hydrodynamic modeling showed that the tidal currents at the summit of seamount were up to about 8 times stronger than in the open ocean. The strength of the tidal currents depended on their location on the summit, and the distance of plume deposition varied up to 6.5 times with the strength of the tidal currents. The results of this study suggest that characterization of tidal currents can be important for assessing and predicting the environmental impacts of mining on seamounts.