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Fluid mechanics lies at the heart of many of the physical processes associated with the nascent deep-sea mining industry. The evolution and fate of sediment plumes that would be produced by seabed mining activities, which are central to the assessment of the environmental impact, are entirely determined by transport processes. These processes, which include advection, turbulent mixing, buoyancy, differential particle settling, and flocculation, operate at a multitude of spatiotemporal scales. A combination of historical and recent efforts that combine theory, numerical modeling, laboratory experiments, and field trials has yielded significant progress, including assessing the role of environmental and operational parameters in setting the extent of sediment plumes, but more fundamental and applied fluid mechanics research is needed before models can accurately predict commercial-scale scenarios. Furthermore, fluid mechanics underpins the design and operation of proposed mining technologies, for which there are currently no established best practices. [ABSTRACT FROM AUTHOR]

The article highlights the dynamics of sediment plumes near the release from a deep seabed polymetallic nodule mining preprototype collector vehicle was conducted in the Clarion Clipperton Zone in the Pacific Ocean 4500-m deep. It also discusses that that turbidity current dynamics sets the fraction of sediment remaining suspended and the scale of the subsequent ambient sediment plume.

As the only deep hypersaline, halite‐precipitating lake on Earth today, the Dead Sea is the single modern analog for investigating the mechanisms by which large‐scale and thick salt deposits, known as "salt giants", have accreted in the geological record. We directly measure the hydroclimatic forcing and the physical limnologic processes leading to halite sedimentation, the vertical thermohaline structure, and salt fluxes in the Dead Sea. We demonstrate that changes in these forcing lead to strong seasonal and regional variations in the stratification stability ratio, triggering corresponding spatiotemporal variations in thermohaline staircase formation and diapycnal salt flux, and finally control the thickness of the halite layer deposited. The observed staircase formation is consistent with the mean‐field γ instability, causing layering in double‐diffusive convection. We show that double diffusion and thermohaline staircase formation drive the spatial variability of halite deposition in hypersaline water bodies, underlying and shaping "salt giants" basin architecture. Plain Language Summary: Kilometers‐thick halite sequences in the geological record represent some of the extreme environmental events during Earth's history. The present‐day Dead Sea serves as an analog for halite deposition and the unique limnology/oceanography of those past hypersaline environments. We observe differential downward salt flux in the lake and halite deposition at the deep lakefloor, corresponding to theoretical requirements of water column stability and the evolution of a step‐like thermohaline structure of the water column. These variations are spatiotemporally controlled by regional hydroclimatology, as the salt flux and halite deposition enhanced during the dry summer and farther from the freshwater inflows into the lake, along an increasing salinity gradient. Our findings explain thick halite accretion in global basin depocenters. Key Points: We resolve the mechanisms driving thick salt layers accretion in deep saline waterbodies by direct field measurements in the Dead SeaHydroclimatic variations impact stratification stability, thermohaline staircases, double diffusion salt fluxes, and halite depositionRegional and seasonal drying trends dictate stronger salt flux in the drier and deeper zones and explain the architecture of "salt giants" [ABSTRACT FROM AUTHOR]

We provide a new perspective on the transition of hyperpycnal flows into saline turbidity currents, which permits longer runout lengths than might be otherwise expected. This mechanism relies on the differential turbulent diffusion of salt and sediment, and in contrast to ambient saltwater entrainment it enables the salinification of the freshwater current without diluting the sediment concentration field by a corresponding amount. The freshness‐to‐sediment ratio is introduced in order to quantify the transition process. The results of high‐resolution simulations provide estimates for the transition distance of hyperpycnal model flows into saline turbidity currents. Plain Language Summary: In some near‐coastal areas of the world's oceans, sediment‐rich rivers trigger so‐called hyperpycnal currents, which are currents composed of river‐derived freshwater and sediment that propagate along the seafloor. In general, one may expect such currents to have a short runout length, since sediment deposition will reduce their density until they loft from the seafloor. There is evidence, however, that in some settings hyperpycnal currents can have much larger runout lengths than expected. Here we propose a novel perspective on such large runout lengths, by showing that differential diffusivities can enable the hyperpycnal flow to transition into a saline turbidity current. This mechanism relies on the fact that salt and sediment diffuse at different rates, so that the freshwater current can become salinified without diluting its sediment concentration field. Key Points: Differential diffusion provides a new perspective on the transition of hyperpycnal flows into saline turbidity currentsDifferential diffusion of salt and sediment can render the freshwater current salty, without strongly diluting the sedimentTransition distance estimates are provided for hyperpycnal model flows [ABSTRACT FROM AUTHOR]