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Mesoscale warm‐core rings, known as Loop Current rings (LCRs) reshape the Gulf of Mexico water masses by redistributing large amounts of heat and salt laterally. LCRs also transform water masses via diapycnal mixing, but the mechanisms by which this occurs are poorly measured. Here, we present glider‐MicroPod turbulence observations that reveal enhanced mixing below the mixed layer, along the eddy edges, driving the LCR's heat, salt, and oxygen exchanges. Interleavings of adjacent water masses may be interpreted mainly as a manifestation of submesoscale processes through stirring of the spice gradients, which facilitates double‐diffusive mixing that transforms Subtropical Underwater into Gulf Common Water. Our findings highlight the need for ocean models to parameterize double‐diffusive mixing processes directly resulting from submesoscale tracer stirring, which may be important at basin scale in the presence of LCRs in the Gulf of Mexico. Plain Language Summary In the Gulf of Mexico (GoM), anticyclonic eddies, known as Loop Current rings (LCRs) carrying warm and salty water shape the basin's water mass properties, which in turn, affects the regional climate and marine life. The water mass properties are altered by turbulent mixing. However, the mechanisms leading to the mixing of GoM waters are still under debate due to a lack of observations. Here, we use an autonomous underwater vehicle (glider) equipped with a turbulence sensor to assess the nature of LCR mixing and its impact on water properties. The breaking of internal waves in the ocean is often thought to be responsible for turbulent mixing in the ocean interior. However, our findings demonstrate that a process called double‐diffusive convection is responsible, where turbulence is forced by differences between the temperature and salinity of adjacent water parcels. We found that double‐diffusive convection was the main driver in mixing heat, salt, and oxygen along the eddy edges, producing Gulf Common Water. These findings highlight the need to include double diffusive processes in ocean models for more accurate simulations. Key Points Direct observations of turbulence reveal the distribution of mixing across a Gulf of Mexico Loop Current Ring Subtropical Underwater is transformed into Gulf Common Water through double‐diffusive convection on the edges of the eddy

In this paper, we investigate the BKM type blowup criterion applied to 3D double-diffusive magneto convection systems. Specifically, we demonstrate that a unique local strong solution does not experience blow-up at time T, given that ). To prove this, we employ the logarithmic Sobolev inequality in the Besov spaces with negative indices and a well-known commutator estimate established by Kato and Ponce. This result is the further improvement and extension of the previous works by O (2021) and Wu (2023).

Parameterizations of small‐scale mixing are important in modeling the behavior of the World Ocean. These microstructure mixing processes do not exist in isolation, however, and larger‐scale processes can affect their fluxes, which is an important consideration for general circulation models. We have developed a new pseudo‐spectral hydrodynamic model, the “Rocking Ocean Modeling Environment,” which is able to simulate the effects of some large‐scale processes, such as shear and internal waves. The code induces a time‐dependent shear forcing across a small domain that can accurately resolve the micro‐scale. This configuration presents a challenge for modeling via Fourier‐based algorithms because the typical evolution of such a flow is incompatible with the periodic boundary conditions at the vertical extremities of the computational domain. This complication is addressed by reformulating the governing equations in a new, temporally varying “tilting” coordinate system associated with the background flow as has been done in the past in the field of homogenous turbulence. The code is applied to one such process which is known to show substantial differences in turbulent environments: salt fingers. We simulate salt fingers in the presence of constant and oscillating shear in order to quantify the mixing of heat and salt by these systems under the impacts of large‐scale internal waves. Generally, it is shown that the application of shear can reduce fluxes by a factor of 2 or 3 for typical amplitudes of near‐inertial waves and that the impact of shear decreases as the frequency of the applied shear increases. Plain Language Summary This work presents a new fluid model designed to investigate how waves and turbulence in the ocean on large (>10 m) scales can affect mixing that occurs on small (∼1 cm) scales. The code is shown to perform well for a variety of tests and one particular application of this code is demonstrated. This application is a process known as salt fingering, and we show how this process can be affected by currents and waves in the ocean. Salt fingers occur in regions where warm and salty water exists above cooler and fresher water. This can happen in a large fraction of the ocean when the amount of evaporation exceeds the amount of precipitation and typically exists at a layer of the ocean where the temperature changes quickly with depth, known as the thermocline. These salt fingers can transport heat and salt vertically in the ocean. However, salt fingers are relatively small (a few centimeters in width) and can be easily disrupted by fluid motion, such as currents and waves. We show through a series of computational experiments involving steady and oscillating motions that the transport of heat and salt by these salt fingers can be easily halved. Key Points We have developed a pseudo‐spectral code for investigating incompressible flows in the presence of shear The code uses a dynamic grid that follows the background flow and remaps to minimize grid deformation The code predicts a reduction in salt fingering fluxes by at least a factor of two by shear

The nonlinear stability of stationary and oscillatory double-diffusive convection in an Oldroyd-B fluid layer is investigated using a perturbation method. The cubic Landau equations are derived and based on which the stability of stationary and oscillatory bifurcating solutions in the neighborhood of their critical values is discussed. The boundary between stationary and oscillatory convection demarcated by identifying a codimension-two points in the viscoelastic parameters plane. The bifurcating solution is found to be subcritical depending on the choices of physical parameters. Heat and mass transport are estimated in terms of Nusselt numbers. The effect of Prandtl number is observed only in the case of oscillatory motions and increase in its value is to decrease the heat and mass transfer. Besides, increasing relaxation and retardation parameters is to decrease and increase the amount of heat and mass transfer, respectively in the stationary case, while these parameters found to exhibit an opposing kind of behavior in the case of oscillatory motions.

In this research article, we investigated the weakly non-linear effect of gravity modulation for the temperature dependent viscous fluid in a horizontal porous layer in the presence of internal heat source. We use power series expansion in terms of the amplitude of gravity modulation, which is considered to be small for double-diffusive convection in porous media. We graphically show the effect of internal heat source, solute Rayleigh number, Lewis number, Vadász number, thermo-rheological parameter, the amplitude of gravity modulation, the frequency of modulation on the heat and mass transfer using Ginzburg-Landau equation. The effect of gravity modulation is found significant and is more effective for the low values of frequency of modulation.

Double diffusive convection (DDC) flows are widely seen in many industrial processes where the thermo-solutal buoyancy forces generates vorticity and initiates convective heat and mass transfer. In this paper numerical computations are conducted on this behaviour inside cavities of different aspect ratio at nominal Rayleigh number using a finite element based code. Velocity –vorticity form of Navier-Stokes equations are solved along with energy and solutal concentration conservation equations simultaneously using Galerkin’s weighted residual method. Bottom wall is assumed hot and salted while top wall is maintained as sink, both side walls of the cavity are assumed to be adiabatic to heat and mass flow. Generally cavities with the present boundary conditions exhibit weak vorticity and convection characteristic especially at low Rayleigh number. In this numerical work an attempt is made to explore the role of variation in relative strength of thermal and solutal buoyancy forces on flow characteristics and mode of heat and mass transfer in such conditions. Simulation results have been reported for different buoyancy ratios in the range -2≤N≤2 , Rayleigh number varying from 1.0e5 to 1.0e3, for cavities of aspect ratios, 0.5(shallow), 1 (square) and 2 (deep). Flow contours are well validated with the results in the literature. The fluid rotation patterns are captured and reported under different operating conditions chosen, the vorticity generation is observed relatively low for deep cavity when compared to other two. Investigations revealed that fluid convection gets greatly hampered when operated in negative buoyancy ratio regime and require relatively higher Rayleigh number to change the mode of heat transfer from diffusion to convection.

The presence of salt in seawater strongly affects the melt rate and the shape evolution of ice, both of utmost relevance in ice–ocean interactions and thus for the climate. To get a better quantitative understanding of the physical mechanics at play in ice melting in salty water, we numerically investigate the lateral melting of an ice block in stably stratified saline water. The developing ice shape from our numerical results shows good agreement with the experiments and theory from Huppert & Turner (J. Fluid Mech., vol. 100, 1980, pp. 367–384). Furthermore, we find that the melt rate of ice depends non-monotonically on the mean ambient salinity: it first decreases for increasing salt concentration until a local minimum is attained, and then increases again. This non-monotonic behaviour of the ice melt rate is due to the competition among salinity-driven buoyancy, temperature-driven buoyancy and salinity-induced stratification. We develop a theoretical model based on the force balance which gives a prediction of the salt concentration for which the melt rate is minimal, and is consistent with our data. Our findings give insight into the interplay between phase transitions and double-diffusive convective flows.

In this paper, we have investigated theoretically the effect of Soret parameter on the onset of double diffusive rotating anisotropic convection in a horizontal sparsely packed porous layer using linear stability theory which is based on the usual normal mode technique. The Brinkman model that includes the Coriolis term is employed for the momentum equation. The effect of anisotropy parameters, Soret parameter, solute Rayleigh number, Taylor number, Lewis number, Darcy and Darcy Prandtl number on stationary and oscillatory convection is shown graphically.

TheAntarctic Ice Sheet loses about half its mass through ocean-driven melting of its fringing ice shelves. However, the ocean processes governing ice shelf melting are not well understood, contributing to uncertainty in projections of Antarctica’s contribution to global sea level. We use high-resolution large-eddy simulation to examine ocean-driven melt, in a geophysical-scale model of the turbulent ice shelf–ocean boundary layer, focusing on the ocean conditions observed beneath the Ross Ice Shelf. We quantify the role of double-diffusive convection in determining ice shelf melt rates and oceanic mixed layer properties in relatively warm and low-velocity cavity environments. We demonstrate that double-diffusive convection is the first-order process controlling the melt rate and mixed layer evolution at these flow conditions, even more important than vertical shear due to a mean flow, and is responsible for the step-like temperature and salinity structure, or thermohaline staircase, observed beneath the ice. A robust feature of the multiday simulations is a growing saline diffusive sublayer that drives a time-dependent melt rate. This melt rate is lower than current ice–ocean parameterizations, which consider only shear-controlled turbulent melting, would predict. Our main finding is that double-diffusive convection is an important process beneath ice shelves, yet is currently neglected in ocean–climate models.

In this paper, we have investigated the onset of double diffusive convection (DDC) in a couple stress fluid saturated rotating anisotropic porous layer in the presence of Soret and Dufour effects using linear stability analyses which is based on the usual normal mode technique. The onset criteria for both stationary and oscillatory modes obtained analytically. The effects of the Taylor number, mechanical anisotropy parameter, Darcy Prandtl number, solute Rayleigh number, normalized porosity parameter, Soret and Dufour parameters on the stationary and oscillatory convections shown graphically. The effects of couple stresses are quite significant for large values of the non-dimensional parameter and delay the onset of convection. Taylor number has stabilizing effect on double diffusive convection, Dufour number has stabilizing effect in stationary mode while destabilizing in oscillatory mode. The negative Soret parameter stabilizes the system and positive Soret parameter destabilizes the system in the stationary convection, while in the oscillatory convection the negative Soret coefficient destabilize the system and positive Soret coefficient stabilizes the system.