IUTAM Summer School on Gravity Currents in the Environment

Gravity currents are a ubiquitous phenomenon in nature and technology. They constitute primarily horizontal flows that are driven by hydrostatic pressure gradients due to variations in temperature, chemical composition, or the presence of suspended particles. They are among the main drivers of heat and mass redistribution on the planet, via density-driven flows in the ocean and atmosphere, and are responsible for a range of natural and man-made hazards, such as snow avalanches, landslides, volcanic eruptions of various kinds, but also positively buoyant flows such as plumes and smoke from fires within buildings. Turbidity currents represent an important class of particle-driven gravity currents, as they represent a key mechanism for transporting sediment into deeper water. Their interaction with the seafloor via erosion and deposition is responsible for the formation of large-scale features such as submarine canyons, and their deposits form the largest sediment bodies on Earth. From an engineering point of view, submarine gravity currents pose a significant hazard to infrastructure such as oil pipelines and telecommunication cables.

That gravity currents can form under such a wide variety of conditions renders them a particularly fascinating research topic. They can be associated with opposite ends of the Reynolds number spectrum (magma flows versus atmospheric currents), so that they are governed by different balances between inertial, viscous, and gravitational forces. They can be nonconservative in that their excess density varies with time (for example, eroding or depositing turbidity currents), they can be Boussinesq or non-Boussinesq in nature (seabreezes versus powder snow avalanches), they can give rise to non-Newtonian dynamics (debris flows), and they can be linked to chemical reactions or to the preferential exclusion of salt during the formation of ice. Gravity currents can exist in ambient environments that exhibit velocity shear, such as in thunderstorm outflows, their dynamics can be affected by complex topography, and they can interact with a background density stratification, thereby triggering the formation of internal gravity waves, or vice versa where sediment resuspension due to breaking internal waves may conversely generate gravity currents.

The proposed course will introduce the fundamental physical principles governing the dynamics of gravity and turbidity currents, along with a broad variety of examples in nature. We will highlight several conceptual models of high Reynolds number gravity currents, and introduce depth-resolving modeling approaches based on the full Navier-Stokes equations.

The course will include a one-day field excursion to examine deposits of ancient submarine gravity flows that occurred 55 million years ago and are now preserved as sedimentary rocks. These include the deposits of turbidity currents and submarine landslides.

The course is intended primarily for graduate students, postdocs, and early career researchers, as well as for senior scientists from engineering and geosciences.