Ambient Stratification Research Articles

Mixing of a cylindrical gravity current in a stratified ambient

Simulation results from direct numerical simulations (DNSs) of cylindrical gravity currents propagating into a linearly stratified ambient with stratification strengths ranging from 0 to 0.8, at a moderate Reynolds number of Re=3450 are presented. The simulations are based on the incompressible Navier–Stokes equations, assuming small density differences such that the Boussinesq approximation is valid. The density of the ambient fluid increases linearly from the top (ρ0) to the bottom (ρb) of the domain. A comparative analysis is conducted between the stratified cases and the unstratified case to investigate the impact of ambient stratification strength on the mixing behaviour of cylindrical gravity currents. The energy conversion processes are analysed using the mechanical framework proposed by Winters et al. (1995). The energy budget is formulated by considering gravitational available potential energy, and the evolution of potential energy due to reversible stirring and irreversible diapycnal mixing in the system. The findings reveal a decrease in available potential energy and kinetic energy with increasing stratification strength, indicating lower energy exchange for gravity currents propagating in the stratified environment. Instantaneous and cumulative mixing efficiency calculations during the slumping phase indicate that Kelvin–Helmholtz billow play an important role in stirring the heavy fluid and causing irreversible mixing with the ambient fluid.

Impacts of Vertical Convective Mixing Schemes and Freshwater Forcing on the 2016–2017 Maud Rise Polynya Openings in a Regional Ocean Simulation

AbstractThe correct representation of the Maud Rise open‐ocean polynya in the Weddell Sea remains a challenge for ocean models. Here we reproduce the most recent polynya openings in 2016–2017 using a regional configuration, and assess their dependencies on vertical convective mixing schemes and freshwater forcing, both separately and in combination. We test three vertical convective mixing schemes: the enhanced vertical diffusion (EVD), the Eddy‐Diffusivity Mass‐Flux (EDMF) parameterization, and a modified version of EDMF accounting for thermobaric effects. Using simulations for the period 2007–2017, we find that the modified EDMF reproduces the observed climatological evolution of the mixed layer depth better than the original EDMF and the EVD, but a polynya fails to open due to excessive freshwater forcing. We thus use the modified EDMF to perform sensitivity experiments with reduced precipitation during 2012–2017. The imposed freshwater forcing strongly affects the number of years with polynyas. The simulation with the best representation of the 2016–2017 polynyas is analyzed to evaluate the triggering mechanisms. The 2016 polynya was induced by the action of thermobaric instabilities on a weak ambient stratification. This opening preconditioned the water column for 2017, which produced a stronger polynya. By examining the impacts of the different convective mixing schemes, we show that the modified EDMF generates more realistic patterns of deep convection. Our results highlight the importance of surface freshwater forcing and thermobaricity in governing deep convection around Maud Rise, and the need to represent thermobaric instabilities to realistically model Maud Rise polynyas.

Evidence of strong wave turbulence and of Bolgiano temperature spectra in katabatic winds on steep slopes

The katabatic winds on steep slopes investigated in the present study reveal a novel spectral behavior, observed in the outer part of the jet. At low wavenumbers, the one-dimensional (1D) velocity spectra show evidence of a kx−1 range for the three components of the velocity vector: Eu(kx),Ev(kx),Ew(kx)∝kx−1 [as well as for the 1D temperature spectrum Eθ(kx)∝kx−1]. This suggests the existence of strong wave turbulence. A necessary condition for strong wave turbulence to be manifest is that the flow direction wavenumber, kx, extends to much lower values than the slope normal one, kz. This is satisfied in the present field experiment where wave energy is injected at wavenumber kx=kN=(Na sin α)/uj¯, while kz∼1/Δz, with Na the ambient stratification, α the slope angle, uj¯ the maximum wind velocity, and Δz the shear layer thickness of the jet. In the inertial range, the velocity spectra exhibit a power law kx−5/3 over two decades, whereas the temperature-buoyancy spectra show evidence of a −7/5 slope in the buoyancy sub-range, followed by a −5/3 slope. The change in spectral slopes occurs at the Bolgiano scale LB that is close to the Dougherty–Ozmidov scale LOZ. The high Reynolds number based on the Taylor micro-scale, Reλ∼103, allows clear identification of the spectral laws.

On the dynamics of gravity current motion in a stratified ambient

This study presents LES results of lock-release propagating gravity current (GC) at the base of a linearly stratified ambient. The focus of the study is to investigate the effect of ambient stratification on GC motion for both subcritical and supercritical regimes. The effects of Reynolds number and the ratio of the fluid depth in the lock to the total ambient fluid depth on GC front velocity are also examined. Also, the effect of stratification strength on mixing is evaluated. It is found that both subcritical and supercritical GCs have a constant-velocity phase. This phase terminates due to the current interaction with the internal waves (IWs) for the former, while for the latter, it is due to the decay of the head buoyancy. The duration of the constant-velocity phase increases with increasing stratification strength when the current is supercritical. For weak stratification the turbulence is considerable, while it is suppressed with stronger stratification. Mixing is more intense for supercritical GCs; however, mixing efficiency is much higher for subcritical GCs.

Stratification Breakdown in Antarctic Coastal Polynyas. Part I: Influence of Physical Factors on the Destratification Time Scale

Abstract This study examines the process of water-column stratification breakdown in Antarctic coastal polynyas adjacent to an ice shelf with a cavity underneath. This first part of a two-part sequence seeks to quantify the influence of offshore katabatic winds, alongshore winds, air temperature, and initial ambient stratification on the time scales of polynya destratification through combining process-oriented numerical simulations and analytical scaling. In particular, the often-neglected influence of wind-driven circulation on the lateral transport of the water formed at the polynya surface—which we call Polynya Source Water (PSW)—is systematically examined here. First, an ice shelf–sea ice–ocean coupled numerical model is adapted to simulate the process of PSW formation in polynyas of various configurations. The simulations highlight that (i) before reaching the bottom, majority of the PSW is actually carried away from the polynya by katabatic wind–induced offshore outflow, diminishing water-column mixing in the polynya and intrusion of the PSW into the neighboring ice shelf cavity, and (ii) alongshore coastal easterly winds, through inducing onshore Ekman transport, reduce offshore loss of the PSW and enhance polynya mixing and PSW intrusion into the cavity. Second, an analytical scaling of the destratification time scale is derived based on fundamental physical principles to quantitatively synthesize the influence of the physical factors, which is then verified by independent numerical sensitivity simulations. This work provides insights into the mechanisms that drive temporal and cross-polynya variations in stratification and PSW formation in Antarctic coastal polynyas, and establishes a framework for studying differences among the polynyas in the ocean.

Basal melt rates and ocean circulation under the Ryder Glacier ice tongue and their response to climate warming: a high-resolution modelling study

Abstract. The oceanic forcing of basal melt under floating ice shelves in Greenland and Antarctica is one of the major sources of uncertainty in climate ice sheet modelling. We use a high-resolution, nonhydrostatic configuration of the Massachusetts Institute of Technology general circulation model (MITgcm) to investigate basal melt rates and melt-driven circulation in the Sherard Osborn Fjord under the floating tongue of Ryder Glacier, northwestern Greenland. The control model configuration, based on the first-ever observational survey by Ryder 2019 Expedition, yielded melt rates consistent with independent satellite estimates. A protocol of model sensitivity experiments quantified the response to oceanic thermal forcing due to warming Atlantic Water and to the buoyancy input from the subglacial discharge of surface fresh water. We found that the average basal melt rates show a nonlinear response to oceanic forcing in the lower range of ocean temperatures, while the response becomes indistinguishable from linear for higher ocean temperatures, which unifies the results from previous modelling studies of other marine-terminating glaciers. The melt rate response to subglacial discharge is sublinear, consistent with other studies. The melt rates and circulation below the ice tongue exhibit a spatial pattern that is determined by the ambient density stratification.

Modeling of tsunami generated in stratified oceans by sub-aquatic volcanic eruptions

In this paper, we develop a model by introducing ambient stratification in the ocean to study the surface waves generated by sub-aquatic volcanic eruptions. The developed equations with the initial and boundary conditions were linearized. The linearized equations were solved using the joint Laplace and Hankel transform Green's function method. The solutions were computed, and the surface elevation was obtained for an instantaneous Duffy source function, revealing a beating phenomenon in the stratified ocean. A clear understanding of the sub-aquatic volcanic eruption and its effect on surface waves will help avoiding large-scale damage to communities and infrastructures in coastal areas.

Maximum Penetration Height and Intrusion Speed of Weak Symmetric Plane Fountains in Linearly Stratified Fluids

The flow behavior of weak symmetric plane fountains in linearly stratified fluids is studied numerically with three-dimensional simulations over a range of the Froude (Fr), Reynolds (Re), and stratification numbers (s). The two main parameters describing the fountain characterization are the dimensionless maximum fountain penetration height (zm) and intrusion velocity (uint), which differ significantly at different flow development stages. It was found that the stratification stabilizes the symmetry of the weak fountains, which makes the fountain become asymmetric at a larger Fr value, and zm at the fully developed stage continues to increase as a result of the intrusion, which continually changes the ambient fluid stratification features, thus the buoyant force. The evolution of intrusion experiences three distinct stages. Both Fr and s have effects on zm and uint, with the effect of Fr usually larger than that of s. The overall impacts of Fr and s can be quantified in terms of Frasb, with a and b varying for different parameters. With numerical results, empirical correlations are produced in terms of Frasb for each relevant parameter, which generally predict the results very well.

Impact of nonuniform ambient stratification on thermal plume dynamics

Thermal plumes arising from localized buoyancy sources have been studied extensively, mostly focusing on entrainment and mixing in fully developed turbulence. Here, we focus on the primary instabilities of laminar plumes and their transitions as the strength of the buoyancy source is increased. Many prior studies in this transitional regime have reported a myriad of disparate spatiotemporal plume characteristics. We show that this wide variety is tied to various ways an axisymmetric system can undergo symmetry breaking, that the nature of the ambient stratification plays an important role in the symmetry breaking, and this determines the details of the plume spatiotemporal characteristics.

On the vortex shedding around a circular cylinder modulated by ambient density stratification

Alternating vortex shedding could be developed when the flow past a circular cylinder. Previous laboratory studies indicate that the vortex shedding frequency, which is expressed as dimensionless Strouhal number St, depends on the Reynolds number. Numerical simulations are used to analyze the flow characteristics around cylinder in recent years, however, they cannot reproduce laboratory measurements properly and the Strouhal numbers are overestimated. This discrepancy is attributed to the fault of numerical method and more advanced turbulence models are expected to improve the results. In this study it is postulated that the overestimated Strouhal number could be attributed to the ambient density stratification, which is neglected in previous numerical simulations. Numerical methods and laboratory measurements are used to confirm this assumption. The numerical results show that the Strouhal number decreases with increasing ambient density gradient for a wide range of Reynolds numbers. An electric thermometer with two sensors is used to measure the typical density gradients for various scenarios. The experimental measurements show that the strength of measured ambient density stratification is in the range anticipated from numerical simulation, which further confirms the influence of ambient density stratification on the vortex shedding frequency.

Wide-angle protostellar outflows driven by narrow jets in stratified cores

Most simulations of outflow feedback on star formation are based on the assumption that outflows are driven by a wide angle “X-wind,” rather than a narrow jet. However, the arguments initially raised against pure jet-driven flows were based on steady ejection in a uniform medium, a notion that is no longer supported based on recent observations. We aim to determine whether a pulsed narrow jet launched in a density-stratified, self-gravitating core could reproduce typical molecular outflow properties, without the help of a wide-angle wind component. We performed axisymmetric hydrodynamic simulations using the MPI-AMRVAC code with optically thin radiative cooling and grid refinement down to 5 au, on timescales up to 10 000 yr. Then we computed the predicted properties for the purposes of a comparison with observational data. First, the jet-driven shell expands much faster and wider through a core with steeply decreasing density than through an uniform core. Second, when blown into the same singular flattened core, a jet-driven shell shows a similar width as a wide-angle wind-driven shell in the first few hundred years, but a decelerating expansion on long timescales. The flow adopts a conical shape, with a sheared velocity field along the shell walls and a base opening angle reaching up toa≃ 90°. Third, at realistic ages of ~10 000 yr, a pulsed jet-driven shell shows fitting features along with a qualitative resemblance with recent observations of protostellar outflows with the Atacama Large Millimeter Array, such as HH46–47 and CARMA–7. In particular, similarities can be seen in the shell widths, opening angles, position-velocity diagrams, and mass-velocity distribution, with some showing a closer resemblance than in simulations based on a wide-angle “X-wind” model. Therefore, taking into account a realistic ambient density stratification in addition to millenia-long integration times is equally essential to reliably predict the properties of outflows driven by a pulsed jet and to confront them with the observations.

Dynamics of a buoyant gravity current propagating in a linearly stratified medium

In this study, we investigate partial- and full-depth buoyant gravity currents propagating along the top surface in a linearly stratified medium. Two- and three-dimensional numerical simulations are performed to study the effect of stratification and initial current depth, on the front speed, internal wave field, and turbulence characteristics. The stratification is varied through a non-dimensional parameter R=ρ0−ρCρb−ρ0, ranging between 0.04 and 85, where ρC is the constant bulk density of the current fluid and ρ0,ρb represent the densities of the ambient fluid at the top and bottom surfaces, respectively. For large values of R (ρ0−ρC≫ρb−ρ0), we observe that the resulting Froude number (Fr=UNH) is greater than 1/π, and the flow is characterized as supercritical, where the front speed exceeds the long wave speed. In the supercritical regime, Kelvin–Helmholtz billows are prominently seen along with an internal solitary wave, which propagates with the density front. As the R value decreases, the relative strength of the ambient stratification increases when compared to the horizontal density difference at the top surface, leading to a subcritical flow regime where the front speed is smaller when compared to the long-wave speed. The Kelvin–Helmholtz billows and the solitary wave gradually disappear, and vertically propagating high-mode internal waves are prominently seen for R< 1. Quantification of the Froude number for various values of R and h/H shows that it follows a power law, Fr∝(h/H×R)1/2, with the proportionality constant 0.72. This scaling works well for all the partial-depth cases considered in this study, i.e., h/H= 1/8, 1/6, 1/4, and 1/3, while a slight deviation is observed for the full-depth gravity currents that correspond to h/H= 1.

Wind Effects on Near‐ and Midfield Mixing in Tidally Pulsed River Plumes

AbstractRiver plumes transport and mix land‐based tracers into the ocean. In tidally pulsed river plumes, wind effects have long been considered negligible in modulating interfacial mixing in the energetic nearfield region. This research tests the influence of variable, realistic winds on mixing in the interior plume. A numerical model of the Merrimack River plume‐shelf system is utilized, with an application of the salinity variance approach employed to identify spatial and temporal variation in advection, straining, and dissipation (mixing) of vertical salinity variance (stratification). Results indicate that moderate wind stresses (∼0.5 Pa) with a northward component countering the downcoast rotation of the plume are most effective at decreasing stratification in the domain relative to other wind conditions. Northward winds advect plume and ambient shelf stratification offshore, allowing shelf water salinity to increase in the nearshore, which strengthens the density gradient at the plume base. Straining in the plume increases with winds enhancing offshore‐directed surface velocities, leading to increased shear at the plume base. Increased straining and larger density gradients at the plume base enhance variance dissipation in the near‐ and midfield plume, and dissipation remains enhanced if the shelf is clear of residual stratification. The smaller spatial and temporal scales of the Merrimack plume allow the mechanisms to occur at tidal time scales in direct response to instantaneous winds. This is the first study to show tidal time scale wind‐induced straining and advection as controlling factors on near‐ and midfield mixing rates in river plumes under realistic winds.

Mean flow structure of katabatic winds and turbulent mixing properties

The recent field measurements of katabatic winds on steep alpine slopes provide a unique database for theoretical analysis of the mean flow development and the determination of mixing properties. The theory is based on the depth-integrated momentum and heat equations, and demonstrates an increase in mean velocity $U$ with downstream distance $x$ according to $x^{n}$ ( $n\leq 1/2$ ). An equation for the mean wind velocity is established, expressing its dependency on the buoyancy flux, related to the heat flux to the ground, entrainment and bottom friction. No ambient stratification, and ambient wind and constant ground surface temperature, lead to $U{\sim} x^{1/2}$ , while constant heat flux to the ground leads to $U{\sim} x^{1/3}$ and requires that the reduced gravity decreases as $x^{-1/3}$ . Stable ambient stratification $N$ causes, in addition to small-amplitude mean flow oscillations, a decrease in reduced gravity with $x$ , in which case the assumption of constant surface heat flux along $x$ is only an approximation. The turbulent fluxes are a function of gradient Richardson number $Ri$ with the ratio of turbulent diffusivity to viscosity $K_h/K_m$ changing from nearly $1.4$ to approximately $0.5$ at $Ri\approx 0.5$ . A new mixing efficiency is introduced that includes turbulence kinetic energy production or consumption by along-slope turbulent buoyancy flux. It increases with $Ri$ up to $0.25$ at $Ri\approx 0.5$ and then remains nearly constant. The measurements allowed us to determine the bottom drag coefficients and interfacial entrainment, with the ground surface heat flux being determined from the mean buoyancy flux.

Mean and Turbulent Characteristics of a Bottom Mixing‐Layer Forced by a Strong Surface Tide and Large Amplitude Internal Waves

AbstractWe present 15 days of both mean and turbulent field observations bottom mixing‐layer at a gently sloping 250 m deep continental shelf site, energized by tides and nonlinear internal waves (NLIWs). The tidal frequency forcing was due to the combined effects of the barotropic tide and a mode‐1 internal tide (IT), while the NLIWs were predominantly mode‐1 waves of depression. The bottom mixing‐layer thickness varied at both semidiurnal and sub‐tidal ∼O(10)d frequencies, with an average thickness of around 10 m. Compression and expansion of the mixing‐layer by both the IT and NLIWs affected the mean velocity profiles in the mixing‐layer, while the phasing between the barotropic and baroclinic flows led to an asymmetry in mean velocity profiles between periods of rising and falling isotherms. With the exception of periods of flow reversal, the turbulent kinetic energy balance and turbulent stress observations were consistent with the existence of an inertial‐sublayer with thickness of approximately 10%–15% of the mixing‐layer thickness ( ∼1 m), even beneath NLIWs. In the outer portion of the mixing‐layer—that is, above the inertial‐sublayer—NLIWs modulated the local turbulence spectra. We discuss the observations in the context of a predictive model for mixing‐layer thickness. The analysis suggests that the high‐frequency variability in mixing‐layer thickness was dominated by internal wave pumping, though strength of the ambient stratification and the frequency of the forcing were important controls on the time‐averaged (sub‐tidal) variation.

The rotation of a sedimenting spheroidal particle in a linearly stratified fluid

We derive analytically the angular velocity of a spheroid, of an arbitrary aspect ratio$\kappa$, sedimenting in a linearly stratified fluid. The analysis demarcates regions in parameter space corresponding to broadside-on and edgewise settling in the limit$Re, Ri_v \ll 1$, where$Re = \rho _0UL/\mu$and$Ri_v =\gamma L^3\,g/\mu U$, the Reynolds and viscous Richardson numbers, respectively, are dimensionless measures of the importance of inertial and buoyancy forces relative to viscous ones. Here,$L$is the spheroid semi-major axis,$U$an appropriate settling velocity scale,$\mu$the fluid viscosity and$\gamma \ (>0)$the (constant) density gradient characterizing the stably stratified ambient, with the fluid density$\rho_0$taken to be a constant within the Boussinesq framework. A reciprocal theorem formulation identifies three contributions to the angular velocity: (1) an$O(Re)$inertial contribution that already exists in a homogeneous ambient, and orients the spheroid broadside-on; (2) an$O(Ri_v)$hydrostatic contribution due to the ambient stratification that also orients the spheroid broadside-on; and (3) a hydrodynamic contribution arising from the perturbation of the ambient stratification whose nature depends on$Pe$;$Pe = UL/D$being the Péclet number with$D$the diffusivity of the stratifying agent. For$Pe \ll 1$, this contribution is$O(Ri_v)$and orients prolate spheroids edgewise for all$\kappa \ (>1)$. For oblate spheroids, it changes sign across a critical aspect ratio$\kappa _c \approx 0.41$, orienting oblate spheroids with$\kappa _c < \kappa < 1$edgewise and those with$\kappa < \kappa _c$broadside-on. For$Pe \ll 1$, the hydrodynamic component is always smaller in magnitude than the hydrostatic one, so a sedimenting spheroid in this limit always orients broadside-on. For$Pe \gg 1$, the hydrodynamic contribution is dominant, being$O(Ri_v^{{2}/{3}}$) in the Stokes stratification regime characterized by$Re \ll Ri_v^{{1}/{3}}$, and orients the spheroid edgewise regardless of$\kappa$. Consideration of the inertial and large-$Pe$stratification-induced angular velocities leads to two critical curves which separate the broadside-on and edgewise settling regimes in the$Ri_v/Re^{{3}/{2}}$–$\kappa$plane, with the region between the curves corresponding to stable intermediate equilibrium orientations. The predictions for large$Pe$are broadly consistent with observations.

Secondary Intrusion Formation of Multiphase Plumes

This work presents a new laboratory study for understanding secondary intrusions in multiphase plumes in quiescent, stratified environments. The study is driven by field observations of secondary intrusions during the Deepwater Horizon (DWH) oil spill. The smaller trap heights observed at DWH for secondary versus primary intrusions could have resulted, in part, from decreasing plume buoyancy (due to gas dissolution) and increasing ambient stratification with elevation above the source. We seek additional mechanisms responsible for the observed smaller secondary trap heights through controlled laboratory experiments where buoyancy and ambient stratification are nominally constant throughout. A novel approach is adopted in the experiments to increase the visibility of secondary intrusions, which are traditionally difficult to visualize, thus investigate. The study reveals that a wider plume source width can also cause the secondary intrusions to trap earlier, providing another plausible explanation for the shallower secondary intrusions observed in the field data.

Dynamics of Eddies Generated by Sea Ice Leads

AbstractInteraction between the atmosphere and ocean in sea ice–covered regions is largely concentrated in leads, which are long, narrow openings between sea ice floes. Refreezing and brine rejection in these leads inject salt that plays a key role in maintaining the polar halocline. The injected salt forms dense plumes that subsequently become baroclinically unstable, producing submesoscale eddies that facilitate horizontal spreading of the salt anomalies. However, it remains unclear which properties of the stratification and leads most strongly influence the vertical and horizontal spreading of lead-input salt anomalies. In this study, the spread of lead-injected buoyancy anomalies by mixed layer and eddy processes are investigated using a suite of idealized numerical simulations. The simulations are complemented by dynamical theories that predict the plume convection depth, horizontal eddy transfer coefficient, and eddy kinetic energy as functions of the ambient stratification and lead properties. It is shown that vertical penetration of buoyancy anomalies is accurately predicted by a mixed layer temperature and salinity budget until the onset of baroclinic instability (~3 days). Subsequently, these buoyancy anomalies are spread horizontally by eddies. The horizontal eddy diffusivity is accurately predicted by a mixing-length scaling, with a velocity scale set by the potential energy released by the sinking salt plume and a length scale set by the deformation radius of the ambient stratification. These findings indicate that the intermittent opening of leads can efficiently populate the polar halocline with submesoscale coherent vortices with diameters of ~10 km, and they provide a step toward parameterizing their effect on the horizontal redistribution of salinity anomalies.

Influence of thermal stratification on vertical natural convection—Experimental investigations on the example of thermal energy storage systems

Stratified thermal energy storages (TESs) are a promising solution for the large-scale energy storage problem of surplus renewable energy. Recent studies have shown parasitic convection occurring in near-wall regions inside such storage tanks, decreasing the working fluid's thermal stratification and reducing their exergy efficiency. This paper presents an experimental investigation of vertical convective flows in thermally stratified environments to complement the theoretical studies in this field. Specifically, we consider natural convection within a stratified laminar flow driven not by active heating but by the temperature gradient along a vertical wall, as is the case in real TES systems. The insights gained into the fundamental physical mechanisms of stratified vertical convection can promote efficiency improvements in TES systems. Therefore, we combine multiple particle image velocimetry and temperature measurements at different heights and thus obtain high-resolution vector fields of the entire wall jet flow and vertical temperature profiles for a TES model experiment. We appropriately modify scaling arguments found in the literature to develop a theory specifically suited to the experimental setup. The experimental data agree well with the modified theory. The results show two laminar counter-directed jets next to the vertical sidewall. In regions with high temperature gradients, the wall jets slow down, and flow reversals occur next to them. Moreover, the wall jets are asymmetric due to temperature-dependent fluid properties in conjunction with the ambient fluid stratification. In the stratification's upper, hot part, the wall jet is thinner and faster than the bottom jet in the cold region.

Effect of crossflow on trapping depths of particle plumes: laboratory experiments and application to the PLUMEX field experiment

The fate and transport of sediment plumes in the ocean, such as those resulting from the disposal of deep-sea mining residuals, are affected by ambient crossflow. We present laboratory measurements of the depth at which a particle plume is trapped by ambient stratification for various crossflow and particle settling velocities. Results suggest that the trap depth declines exponentially with crossflow velocity but is relatively insensitive to settling velocity in the range studied. An empirical correlation based on the laboratory data is validated by a larger scale field experiment involving simulated disposal of deep-sea mining wastes.