Evaluating the environmental impact of deep-sea mining in the Clarion-Clipperton Zone

Details

Supervisors

Hanert, Emmanuel ; Scherpereel, Colin

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en sciences et technologies de l'environnement, à finalité spécialisée

Abstract

enGrowing global demand for critical minerals to support the low-carbon transition has sparked increasing interest in deep-sea mining, particularly in the eastern Pacific Clarion-Clipperton Zone, despite the uncertainties surrounding its environmental consequences. In these regions, the extraction of polymetallic nodules (PMN) from depths around 4,000 meters poses multiple environmental threats, including increased underwater noise and artificial lighting, destruction of benthic habitats, and the generation of metal-rich sediment plumes that can spread over large distances, increasing turbidity and smothering seafloor organisms. There is currently limited understanding of how sediment plumes disperse and how extraction activities could be adopted to minimize their impact. Here we used the 3D baroclinic version of the multiscale ocean model SLIM coupled with a Lagrangian sediment transport model to simulate the dispersal of sediment plumes generated by PMN mining. Our results show that fine particles (< 28 μm) are primarily responsible for the extent of the impacted area, which is almost 80 times larger than the mined area. Unlike coarser sediments, fine particles can travel more than 100 km by remaining suspended for hundreds of hours, emphasizing the need to prioritize these sediment classes in efforts to mitigate environmental impacts. Our results also reveal that both impact assessment and the effectiveness of mitigation strategies are highly sensitive to the thresholds used to define unacceptable harm, highlighting the need for further research on benthic ecosystems. This work provides a foundation for developing mitigation strategies based on deep-sea ocean circulation forecasts. Coupled with real-time measurements, such models could enhance the accuracy of sediment plume predictions. In the context of commercialscale polymetallic nodule extraction, regulatory bodies like the International Seabed Authority could mandate their use to minimize environmental harm while ensuring responsible resource extraction.