Wave breaking turbulence at the offshore front of the Columbia River Plume

© The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geophysical Research Letters 41 (2014): 8987–8993, doi:10.1002/2014GL062274.Observations at the Columbia River plume show that wave breaking is an important source of turbulence at the offshore front, which may contribute to plume mixing. The lateral gradient of current associated with the plume front is sufficient to block (and break) shorter waves. The intense whitecapping that then occurs at the front is a significant source of turbulence, which diffuses downward from the surface according to a scaling determined by the wave height and the gradient of wave energy flux. This process is distinct from the shear-driven mixing that occurs at the interface of river water and ocean water. Observations with and without short waves are examined, especially in two cases in which the background conditions (i.e., tidal flows and river discharge) are otherwise identical.This work was supported by the Office of Naval Research, as part of the Data Assimilation and Remote Sensing for Littoral Applications (DARLA) project and in coordination with the Rivers and Inlets (RIVET) program

Wave-Breaking Turbulence in the Ocean Surface Layer

Observations of winds, waves, and turbulence at the ocean surface are compared with several analytic formulations and a numerical model for the input of turbulent kinetic energy by wave breaking and the subsequent dissipation. The observations are generally consistent with all of the formulations, although some differences are notable at winds greater than 15 m s⁻¹. The depth dependence of the turbulent dissipation rate beneath the waves is fit to a decay scale, which is sensitive to the choice of vertical reference frame. In the surface-following reference frame, the strongest turbulence is isolated within a shallow region of depths much less than one significant wave height. In a fixed reference frame, the strong turbulence penetrates to depths that are at least half of the significant wave height. This occurs because the turbulence of individual breakers persists longer than the dominant period of the waves and thus the strong surface turbulence is carried from crest to trough with the wave orbital motion.This is the publisher’s final pdf. The published article is copyrighted by the American Meteorological Society and can be found at: https://www.ametsoc.org/ams/index.cfm/publications/journals/journal-of-physical-oceanography/The SWIFT wave, wind, and turbulence data are available online (at www.apl.uw.edu/swift) by serial number. The waverider spectra are available as station 166 from the Coastal Data Information Program (CDIP) at the Scripps Institution of Oceanography or the National Data Buoy Center (NDBC) as station 46246.KEYWORDS: Wave breaking, Waves, oceanic, Atmosphere-ocean interaction, Turbulence, Wind waves, Circulation/ Dynamics, Atm/Ocean Structure/ Phenomena, Sea stat

Measurements of Enhanced Near-Surface Turbulence Under Windrows

Observations of waves, winds, turbulence, and the geometry and circulation of windrows were made in a shallow bay in the winter of 2018 outside of Rimouski, Québec. Water velocities measured from a forward-looking pulse-coherent ADCP mounted on a small zodiac show spanwise (cross-windrow) convergence, streamwise (downwind) velocity enhancement, and downwelling in the windrows, consistent with the view that windrows are the result of counter-rotating pairs of wind-aligned vortices. The spacing of windrows, measured with acoustic backscatter and with surface imagery, was measured to be approximately twice the water depth, which suggests an aspect ratio of 1. The magnitude and vertical distribution of turbulence measured from the ADCP are consistent with a previous scaling and observations of near-surface turbulence under breaking waves, with dissipation rates larger, and decaying faster vertically than what is expected from a shear-driven boundary layer. Measurements of dissipation rate are partitioned to within, and outside of the windrow convergence zones, and measurements inside the convergence zones are found to be nearly an order of magnitude larger than those outside with similar vertical structure. A ratio of time scales suggests that turbulence likely dissipates before it can be advected horizontally into convergences, but the advection of wave energy into convergences may elevate the surface flux of TKE and could explain the elevated turbulence in the windrows. These results add to a limited number of conflicting observations of turbulence variability due to windrows, which may modify gas flux, and heat and momentum transport in the surface boundary layer

Data to accompany “Direct observation of wave-coherent pressure work in the atmospheric boundary layer”

As described in the methods section of “Direct Observation of Wave-coherent Pressure Work in the Atmospheric Boundary Layer”: Measurements were made from an open-lattice steel tower deployed in roughly 13 m water depth in Buzzards Bay, MA. Buzzards Bay is a 48 km by 12 km basin open on the SW side to Rhode Island Sound. The average depth is 11 m, with a tide range of 1 to 1.5 m, depending on the neap/spring cycles. Winds in Buzzards Bay are frequently aligned on the long-axis (from the NE or SW), and are commonly strong, particularly in the fall and winter. The tower was deployed near the center of the bay at 41.577638 N, 70.745555 W for a spring deployment lasting from April 12, 2022 to June 13th, 2022. Atmospheric measurements included three primary instrument booms that housed paired sonic anemometers (RM Young 81000RE) and high-resolution pressure sensors (Paros Scientific). The pressure sensor intakes were terminated with static pressure heads, which reduce the dynamic pressure contribution to the measured (static) pressure. The tower booms were aligned at 280 degrees such that the NE and SW winds would be unobstructed by the tower's main body. A fourth sonic anemometer (Gill R3) was extended above the tower such that it was open to all wind directions and clear of wake by the tower structure. A single point lidar (Riegl LD90-3i) was mounted to the highest boom, such that the lidar measured the water surface elevation underneath the anemometer and pressure sensors to within a few centimeters horizontally. All instruments were time synchronized with a custom "miniNode" flux logger, that aggregated the data streams from each instrument. Additional atmospheric and wave measurements on the tower included short-wave and long-wave radiometers (Kipp & Zonen), two RH/T sensors (Vaisala), and a standard lower-resolution barometer (Setra).National Science Foundation, Division of Ocean Sciences (OCE) Award 202302

Observations of turbulence and the geometry and circulation of windrows in a small bay in the St. Lawrence Estuary

Measurements of ocean turbulence, waves, and the geometry and circulation of windrows were made over 5 days in early March in a small bay in the St. Lawrence Estuary. Measurements were made from a small zodiac and from a SWIFT drifter. Two acoustic doppler velocity profilers (ADCPs) were used from the zodiac to measure water velocity and turbulent kinetic energy (TKE) dissipation rates near the surface. The acoustic backscatter from the ADCPs was used in conjunction with a GPS to map the location and spacing of wind aligned rows of bubbles. The SWIFT drifter provided measurements of waves, wind stress, and secondary measurements of TKE dissipation rates. Imagery of the surface was taken with a GoPro camera mounted on the zodiac, and with a DJI MavicPro quadcopter.Funding was provided by the Woods Hole Oceanographic Institute’s Postdoctoral Scholar Program and by the Interdisciplinary Award. This work was also partially supported by the Centre National d’Études Spatiales (CNES) project WAVE-ICE (PS), and the project WAVESCALE under the “Laboratoire d’Excellence” LabexMER (ANR-10-LABX-19) co-funded by a grant from the French government under the program “Investissements d’Avenir” (PS). The BicWin experiment during which this study occurred is funded by the MEOPAR Network of Centers of Excellence (DD) and is a contribution to the research program of Québec-Océan

Parsing the kinetic energy budget of the ocean surface mixed layer

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Zippel, S. F., Farrar, J. T., Zappa, C. J., & Plueddemann, A. J. Parsing the kinetic energy budget of the ocean surface mixed layer. Geophysical Research Letters, 49(2), (2022): 2021GL095920, https://doi.org/10.1029/2021GL095920.The total rate of work done on the ocean by the wind is of considerable interest for understanding global energy balances, as the energy from the wind drives ocean currents, grows surface waves, and forces vertical mixing. A large but unknown fraction of this atmospheric energy is dissipated by turbulence in the upper ocean. The focus of this work is twofold. First, we describe a framework for evaluating the vertically integrated turbulent kinetic energy (TKE) equation using measurable quantities from a surface mooring, showing the connection to the atmospheric, mean oceanic, and wave energy. Second, we use this framework to evaluate turbulent energetics in the mixed layer using 10 months of mooring data. This evaluation is made possible by recent advances in estimating TKE dissipation rates from long-enduring moorings. We find that surface fluxes are balanced by TKE dissipation rates in the mixed layer to within a factor of two.This work was funded by NSF Award No. 2023 020, and by NASA as part of the Salinity Processes in the Upper Ocean Regional Study (SPURS), supporting field work for SPURS-1 (NASA Grant No. NNX11AE84G), and for analysis (NASA Grant No. 80NSSC18K1494), and as part of SASSIE (NASA Grant No. 80NSSC21K0832). This work was also funded by NSF through Grant Award Nos. 1756 839, 2049546, and by ONR through Grant N000141712880 (MISO-BoB)