Observations and numerical simulations of large‐eddy circulation in the ocean surface mixed layer

Sundermeyer, Miles A.; Skyllingstad, Eric D.; Ledwell, James R.; Concannon, Brian; Terray, Eugene A.; Birch, Daniel A.; Pierce, Stephen D.; Cervantes, Brandy T. Kuebel

doi:10.1002/2014gl061637

Cited by 12 publications

(8 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…2) and particles aggregate into patches and streaks, though the streaks and patches are not as evident as in Langmuir turbulence. This is consistent with Sundermeyer et al (2014), which shows surface material is aligned in streaks without significant wave forcing.…”

Section: ) Phenomenologysupporting

confidence: 89%

Horizontal Dispersion of Buoyant Materials in the Ocean Surface Boundary Layer

Liang

Wan

Rose

et al. 2018

Journal of Physical Oceanography

View full text Add to dashboard Cite

The horizontal dispersion of materials with a constant rising speed under the exclusive influence of ocean surface boundary layer (OSBL) flows is investigated using both three-dimensional turbulence-resolving Lagrangian particle trajectories and the classical theory of dispersion in bounded shear currents generalized for buoyant materials. Dispersion in the OSBL is caused by the vertical shear of mean horizontal currents and by the turbulent velocity fluctuations. It reaches a diffusive regime when the equilibrium vertical material distribution is established. Diffusivity from the classical shear dispersion theory agrees reasonably well with that diagnosed using three-dimensional particle trajectories. For weakly buoyant materials that can be mixed into the boundary layer, shear dispersion dominates turbulent dispersion. For strongly buoyant materials that stay at the ocean surface, shear dispersion is negligible compared to turbulent dispersion. The effective horizontal diffusivity due to shear dispersion is controlled by multiple factors, including wind speed, wave conditions, vertical diffusivity, mixed layer depth, latitude, and buoyant rising speed. With all other meteorological and hydrographic conditions being equal, the effective horizontal diffusivity is larger in wind-driven Ekman flows than in wave-driven Ekman–Stokes flows for weakly buoyant materials and is smaller in Ekman flows than in Ekman–Stokes flows for strongly buoyant materials. The effective horizontal diffusivity is further reduced when enhanced mixing by breaking waves is included. Dispersion by OSBL flows is weaker than that by submesoscale currents at a scale larger than 100 m. The analytic framework will improve subgrid-scale modeling in realistic particle trajectory models using currents from operational ocean models.

show abstract

Section: ) Phenomenologysupporting

confidence: 89%

Horizontal Dispersion of Buoyant Materials in the Ocean Surface Boundary Layer

Liang

Wan

Rose

et al. 2018

Journal of Physical Oceanography

View full text Add to dashboard Cite

show abstract

“…In addition to the passive imagery capturing horizontal structure of the dye plume, active visible sensing can be useful for resolving the vertical structure of the plume [9]. This is accomplished by means of a Light Detection and Ranging (LIDAR) method, which directs a short laser beam pulse at the scene, and then splits the returned signal by time of arrival, which is then related to water depth.…”

Section: Visible Light Methodsmentioning

confidence: 99%

Airborne Remote Sensing of the Upper Ocean Turbulence during CASPER-East

et al. 2018

View full text Add to dashboard Cite

This study takes on the challenge of resolving upper ocean surface currents with a suite of airborne remote sensing methodologies, simultaneously imaging the ocean surface in visible, infrared, and microwave bands. A series of flights were conducted over an air-sea interaction supersite established 63 km offshore by a large multi-platform CASPER-East experiment. The supersite was equipped with a range of in situ instruments resolving air-sea interface and underwater properties, of which a bottom-mounted acoustic Doppler current profiler was used extensively in this paper for the purposes of airborne current retrieval validation and interpretation. A series of water-tracing dye releases took place in coordination with aircraft overpasses, enabling dye plume velocimetry over 100 m to 10 km spatial scales. Similar scales were resolved by a Multichannel Synthetic Aperture Radar, which resolved a swath of instantaneous surface velocities (wave and current) with 10 m resolution and 5 cm/s accuracy. Details of the skin temperature variability imprinted by the upper ocean turbulence were revealed in 1-14,000 m range of spatial scales by a mid-wave infrared camera. Combined, these methodologies provide a unique insight into the complex spatial structure of the upper ocean turbulence on a previously under-resolved range of spatial scales from meters to kilometers. However, much attention in this paper is dedicated to quantifying and understanding uncertainties and ambiguities associated with these remote sensing methodologies, especially regarding the smallest resolvable turbulent scales and reference depths of retrieved currents.Keywords: airborne remote sensing; ocean surface currents; upper ocean turbulence BackgroundCapabilities for spatial measurements of ocean surface turbulence are highly desirable for a wide variety of needs ranging from basic studies of upper ocean mixing processes to data assimilation into high-resolution coastal and ocean circulation models. On the global scale, presently available observations of the ocean currents are provided by satellite altimeters, which are limited to mesoscales and resolve only the geostrophic component of the surface current. Much anticipated launches of the

show abstract

“…Besides, D'Asaro et al (2014) show that Langmuir turbulence is not important everywhere in the ocean. Also, in a recent study of tracer injected in the OBL, lidar observations of banded structures were qualitatively reproduced using LES both with and without the Langmuir forcing (Sundermeyer et al, 2014). We also do not consider submesoscale fronts or mesoscale eddies in deeper layers in this study; again for reasons of simplicity.…”

Section: Introductionmentioning

confidence: 99%

Material transport in a convective surface mixed layer under weak wind forcing

et al. 2015

View full text Add to dashboard Cite

Flows in the upper ocean mixed layer are responsible for the transport and dispersion of biogeochemical tracers, phytoplankton and buoyant pollutants, such as hydrocarbons from an oil spill. Material dispersion in mixed layer flows subject to diurnal buoyancy forcing and weak winds (|u 10 | = 5 ms −1) are investigated using a non-hydrostatic model. Both purely buoyancy-forced and combined wind-and buoyancy-forced flows are sampled using passive tracers, as well as 2D and 3D particles to explore characteristics of horizontal and vertical dispersion. It is found that the surface tracer patterns are determined by the convergence zones created by convection cells within a time scale of just a few hours. For pure convection, the results displayed the classic signature of Rayleigh-Benard cells. When combined with a wind stress, the convective cells become anisotropic in that the along-wind length scale gets much larger than the crosswind scale. Horizontal relative dispersion computed by sampling the flow fields using both 2D and 3D passive particles is found to be consistent with the Richardson regime. Relative dispersion is an order of magnitude higher and 2D surface releases transition to Richardson regime faster in the wind-forced case. We also show that the buoyancy-forced case results in significantly lower amplitudes of scale-dependent horizontal relative diffusivity, k D (ℓ), than those reported by Okubo (1970), while the wind-and buoyancy-forced case shows a good agreement with Okubo's diffusivity amplitude, and the scaling is consistent with Richardson's 4/3rd law, k D ∼ ℓ 4/3. These modeling results provide a framework for measuring material dispersion by mixed layer flows in future observational programs.

show abstract

Observations and numerical simulations of large‐eddy circulation in the ocean surface mixed layer

Cited by 12 publications

References 25 publications

Horizontal Dispersion of Buoyant Materials in the Ocean Surface Boundary Layer

Horizontal Dispersion of Buoyant Materials in the Ocean Surface Boundary Layer

Airborne Remote Sensing of the Upper Ocean Turbulence during CASPER-East

Material transport in a convective surface mixed layer under weak wind forcing

Contact Info

Product

Resources

About