A simple advection-diffusion-settling model for estimating deep-sea mining sediment plume transport

Large regions of the deep ocean are covered in potato-sized nodules rich in metals and minerals that are commonly mined on land for the production of batteries. An emerging deep-sea mining industry proposes to use large vehicles to collect nodules from the seabed. During nodule mining, a collector vehicle will pick up sediment as it drives along the seabed. Most of this unwanted sediment is expected to be discharged at the rear of the vehicle, close to the seabed, resulting in a so-called seabed plume. The remaining sediment is lifted up with the nodules to a surface operation vessel, where it is separated from the nodules and returned back to the ocean, either in the midwater column or near the seabed. The seabed and discharge sediment plumes lie at the core of the indirect impact of deep-sea mining on the ocean environment, yet their evolution remains a topic of speculations and misconceptions. Here, we employ established principles of fluid dynamics, namely advection, diffusion and settling, to derive simple predictions of the evolution of both seabed and discharge plumes over their entire lifespan.