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Eric Kunze

Senior Principal Oceanographer

Affiliate Professor, Oceanography

Email

kunze@apl.washington.edu

Phone

206-221-2616

Biosketch

Eric Kunze's research focuses on smallscale (1 cm – 100 km) ocean physics that contributes to mixing and stirring with the ultimate goal of parameterizing the influence of subgridscale processes on larger-scale ocean phenomena that can be modeled with global climate models. He both collects data at sea and analyzes it in the context of the underlying dynamics. Interests include interactions of internal gravity waves with background flows and topography, quantifying internal wave energy budgets, shear instability production of turbulent mixing, and the salt-fingering form of double diffusion. He has also explored whether swimming marine organisms can contribute significant mixing to the world ocean. [They can't.] Eric Kunze was a WHOI Geophysical Fluid Dynamics Fellow during 1983 under the supervision of Francis Bretherton and a WHOI postdoctoral fellow during 1985–86 in collaboration with Ray Schmitt, Sandy Williams and Mel Briscoe. He was awarded AGU's Father James B. Macelwane Medal for Young Investigators in 1992. During 2004–2011, he was a Canada Research Chair in Physical Oceanography. He is presently a principal oceanographer at the Applied Physics Lab, Univ. of Washington, an affiliate in the School of Oceanography, an editor for the Journal of Physical Oceanography and a Pacific Science Center Science Communication Fellow. He maintains discographies for the 20th century American composer Alan Hovhaness and the 19th century French composer Charles Valentin Alkan.

Department Affiliation

Ocean Physics

Education

B.Sc. Physics/Mathematics, University of British Columbia, 1979

M.S. Physical Oceanography, University of Washington, 1982

Ph.D. Physical Oceanography, University of Washington, 1985

Publications

2000-present and while at APL-UW

Global patterns of diapycnal mixing from measurements of the turbulent dissipation rate

Waterhouse, A.F., et al., including M.H. Alford, E. Kunze, T.B. Sanford, and C.M. Lee, "Global patterns of diapycnal mixing from measurements of the turbulent dissipation rate," J. Phys. Oceanogr., 44, 1854-1872, doi:10.1175/JPO-D-13-0104.1, 2014.

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1 Jul 2014

The authors present inferences of diapycnal diffusivity from a compilation of over 5200 microstructure profiles. As microstructure observations are sparse, these are supplemented with indirect measurements of mixing obtained from (i) Thorpe-scale overturns from moored profilers, a finescale parameterization applied to (ii) shipboard observations of upper-ocean shear, (iii) strain as measured by profiling floats, and (iv) shear and strain from full-depth lowered acoustic Doppler current profilers (LADCP) and CTD profiles. Vertical profiles of the turbulent dissipation rate are bottom enhanced over rough topography and abrupt, isolated ridges. The geography of depth-integrated dissipation rate shows spatial variability related to internal wave generation, suggesting one direct energy pathway to turbulence. The global-averaged diapycnal diffusivity below 1000-m depth is O(10-4) m2 s-1 and above 1000-m depth is O(10-5) m2 s-1. The compiled microstructure observations sample a wide range of internal wave power inputs and topographic roughness, providing a dataset with which to estimate a representative global-averaged dissipation rate and diffusivity. However, there is strong regional variability in the ratio between local internal wave generation and local dissipation. In some regions, the depth-integrated dissipation rate is comparable to the estimated power input into the local internal wave field. In a few cases, more internal wave power is dissipated than locally generated, suggesting remote internal wave sources. However, at most locations the total power lost through turbulent dissipation is less than the input into the local internal wave field. This suggests dissipation elsewhere, such as continental margins.

Second-order seasonal variability in diel vertical migration timing of euphausiids in a coastal inlet

Sato, M., J.F. Dower, E. Kunze, and R. Dewey, "Second-order seasonal variability in diel vertical migration timing of euphausiids in a coastal inlet," Mar. Ecol. Prog. Ser., 480, 39-56, doi:10.3354/meps10215, 2013.

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22 Apr 2013

Variability in the diel vertical migration timing of euphausiids in Saanich Inlet, British Columbia, Canada, is quantified using 2 yr of echosounder data from a cabled observatory. The continuous and high-resolution nature of the observations allows examination of second-order seasonal variability in migration timing relative to civil twilight times. Early dusk ascent and late dawn descent occur during spring–fall, while late dusk ascent and early dawn descent occur during winter. Ascent timing appears to be regulated by (1) light availability at the daytime depth of the euphausiids, which is modulated by phytoplankton bloom shadowing, and (2) euphausiid size-dependent visual predation risk. Because (1) does not apply at dawn, descent timing appears to be regulated by (2). During the pre-spawning period, higher energy demand for reproduction may cause earlier dusk ascent and later dawn descent to maximize energy gain, even with larger body size. Instead of the traditional view of diel vertical migration timing, correlated solely with civil twilight, our data suggest that euphausiids also adapt their migration timing to accommodate changes in environmental cues as well as their growth.

Can barotropic tide–eddy interactions excite internal waves?

Lelong, M.-P., and E. Kunze, "Can barotropic tide–eddy interactions excite internal waves?" J. Fluid Mech., 721, 1-27, doi:10.1017/jfm.2013.1, 2013.

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1 Apr 2013

The interaction of barotropic tidal currents and baroclinic geostrophic eddies is considered theoretically and numerically to determine whether energy can be transferred to an internal wave field by this process. The eddy field evolves independently of the tide, suggesting that it acts catalytically in facilitating energy transfer from the barotropic tide to the internal wave field, without exchanging energy with the other flow components. The interaction is identically zero and no waves are generated when the barotropic tidal current is horizontally uniform. Optimal internal wave generation occurs when the scales of tide and eddy fields satisfy resonant conditions. The most efficient generation is found if the tidal current horizontal scale is comparable to that of the eddies, with a weak maximum when the scales differ by a factor of two. Thus, this process is not an effective mechanism for internal wave excitation in the deep ocean, where tidal current scales are much larger than those of eddies, but it may provide an additional source of internal waves in coastal areas where horizontal modulation of the tide by topography can be significant.

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Internal bores and breaking internal tides on the Oregon continental slope

Martini, K.I., M.H. Alford, E. Kunze, S.M. Kelly, and J.D. Nash, "Internal bores and breaking internal tides on the Oregon continental slope," J. Phys. Oceanogr., 43, 120-139, doi:10.1175/JPO-D-12-030.1, 2013.

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1 Jan 2013

We present observations of breaking internal tides on the Oregon continental slope during a 40-day deployment of 5 moorings along 43° 12' N. Remotely-generated internal tides shoal onto the slope, steepen, break and form turbulent bores that propagate upslope independently of the internal tide. A high-resolution snapshot of a single bore is captured from LADCP/CTD profiles in a 25-hour time-series at 1200 m. The bore is cold, salty, over 100-m tall and has a turbulent head where instantaneous dissipation rates are enhanced and sediment is resuspended. At the two deepest slope moorings (1452 and 1780-m), similar bore-like phenomena are observed in near-bottom high-resolution temperature time series. Mean dissipation rates and diapycnal diffusivities increase by a factor of 2 when bores are present and observed internal tides are energetic enough to drive these enhanced dissipation rates. Globally, we estimate an average of 1.3 kW m-1 of internal tide energy flux is directed onto continental slopes. On the Oregon slope, internal tide fluxes are smaller suggesting it is a relatively weak internal tide sink. Mixing associated with the breaking of internal tides are therefore likely to be larger on other continental slopes.

The effect of vertical and horizontal dilution on fertilized patch experiments

Ianson, D., C. Volker, K.L. Denman, E. Kunze, and N. Steiner, "The effect of vertical and horizontal dilution on fertilized patch experiments," Global Biogeochem. Cycles, 26, doi:10.1029/2010GB004008, 2012.

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11 Jul 2012

A great deal of attention, both negative and positive, has been directed at the potential of large-scale iron fertilization schemes to sequester carbon by inducing phytoplankton blooms that would, in theory, result in significant export of organic carbon to the deep ocean in high nitrogen - low chlorophyll regions. A suite of iron manipulation or "patch" experiments has been performed over length-scales of 10s of km. Here, we use a physical-ecological-chemical model, with prognostic nitrogen, silica and iron dynamics, to study one of the most successful of these experiments, the Subarctic Ecosystem Response to Iron Enrichment Study (SERIES), focusing on the vertical export of organic material, which is difficult to observe in the field. The implications of large-scale fertilization, i.e. increasing patch size, are investigated. Our results agree with the general conclusions obtained from the field experiments. Only a modest export of organic carbon occurs (less than 25% of carbon uptake by phytoplankton) at the base of the mixed layer. Furthermore, we show that lateral and vertical supply of silicic acid is necessary to fuel a sustained phytoplankton bloom. Increasing patch size results in less lateral nutrient supply relative to patch area and so a decrease, not only in total production (per unit area), but in the contribution by large phytoplankton due to silica limitation. Most importantly, the export of organic carbon (per unit area) decreases substantially, by nearly an order of magnitude, as scales of 1000 km are approached.

The cascade of tidal energy from low to high modes on a continental slope

Kelly, S.M., J.D. Nash, K.I. Martini, M.H. Alford, and E. Kunze, "The cascade of tidal energy from low to high modes on a continental slope," J. Phys. Oceanogr., 42, 1217-1232, doi:10.1175/JPO-D-11-0231.1, 2012.

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1 Jul 2012

The linear transfer of tidal energy from large to small scales is quantified for small tidal excursion over a near-critical continental slope. A theoretical framework for low-wavenumber energy transfer is derived from "flat bottom" vertical modes and evaluated with observations from the Oregon continental slope. To better understand the observations, local tidal dynamics are modeled with a superposition of two idealized numerical simulations, one forced by local surface-tide velocities and the other by an obliquely incident internal tide generated at the Mendocino Escarpment 315 km southwest of the study site. The simulations reproduce many aspects of the observed internal tide and verify the modal-energy balances. Observed transfer of tidal energy into high-mode internal tides is quantitatively consistent with observed turbulent kinetic energy (TKE) dissipation. Locally generated and incident simulated internal tides are superposed with varying phase shifts to mimic the effects of the temporally varying mesoscale. Altering the phase of the incident internal tide alters (i) internal-tide energy flux, (ii) internal-tide generation, and (iii) energy conversion to high modes, suggesting that tidally driven TKE dissipation may vary between 0 and 500 watts per meter of coastline on 3–5-day time scales. Comparison of observed in situ internal-tide generation and satellite-derived estimates of surface-tide energy loss is inconclusive.

Turbulent mixing and exchange with interior waters on sloping boundaries

Kunze, E., C. MacKay, E.E. McPhee-Shaw, K. Morrice, J.B. GIrton, and S.R. Terker, "Turbulent mixing and exchange with interior waters on sloping boundaries," J. Phys. Oceanogr., 42, 910-927, doi:10.1175/JPO-D-11-075.1, 2012.

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1 Jun 2012

Microstructure measurements along the axes of Monterey and Soquel Submarine Canyons reveal 200%u2013300-m-thick well-stratified turbulent near-bottom layers with average turbulent kinetic energy dissipation rates 4 x 10-8 W kg-1 and eddy diffusivities 16 x 10-4 m2 s-1 (assuming mixing efficiency γ = 0.2) to at least thalweg depths of 1200 m. Turbulent dissipation rates are an order of magnitude lower in overlying waters, whereas buoyancy frequencies are only 25% higher. Well-mixed bottom boundary layer thicknesses hN are an order of magnitude thinner than the stratified turbulent layer. Because well-stratified turbulent layers are commonly observed above slopes, arguments that mixing efficiency should be reduced on sloping boundaries do not hold in cases of energetic internal-wave generation or interaction with topography. An advective–diffusive balance is used to infer velocities and transports, predicting horizontal upslope flows of 10–50 m day-1. Extrapolating this estimate globally suggests that canyon turbulence may contribute 2–3 times as much diapycnal transport to the World Ocean as interior mixing. The upcanyon turbulence-driven transports are not uniform, and the resulting upslope convergences will drive exchange between the turbulent layer and more quiescent interior. Predicted density surfaces of detrainment and entrainment are consistent with observed isopycnals of intermediate nepheloid and clear layers. These data demonstrate that turbulent mixing dynamics on sloping topography are fundamentally 2D or 3D in the ocean, so they cannot be accurately described by 1D models.

Fluid mixing by swimming organisms in the low-Reynolds-number limit

Kunze, E., "Fluid mixing by swimming organisms in the low-Reynolds-number limit," J. Mar. Res., 69, 591-601, doi:10.1357/002224011799849435, 2011.

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1 Jul 2011

Recent publications in the fluid physics literature have suggested that low-Reynolds-number swimming organisms might contribute significantly to ocean mixing. These papers have focussed on the mass transport due to fluid capture and disturbance by settling or swimming particles based on classical fluid mechanics flows but have neglected the role of molecular property diffusion. Scale-analysis of the property conservation equation finds that, while properties with low molecular diffusivities can have enhanced mixing for typical volume fractions in aggregations of migrating zooplankton, this mixing is still well below that due to internal-wave breaking so unlikely to be important in the ocean.

Observations of internal tides on the Oregon continental slope.

Martini, K.I., M.H. Alford, and E. Kunze, "Observations of internal tides on the Oregon continental slope." J. Phys. Oceanogr., 41, 1772-1794, doi: 10.1175/2011JPO4581.1, 2011.

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1 Jun 2011

A complex superposition of locally forced and shoaling remotely generated semidiurnal internal tides occurs on the Oregon continental slope. Presented here are observations from a zonal line of five profiling moorings deployed across the continental slope from 500 to 3000 m, a 24-h expendable current profiler (XCP) survey, and five 15-48-h lowered ADCP (LADCP)/CTD stations. The 40-day moored deployment spans three spring and two neap tides, during which the proportions of the locally and remotely forced internal tides vary. Baroclinic signals are strong throughout spring and neap tides, with 4-5-day-long bursts of strong cross-slope baroclinic semidiurnal velocity and vertical displacement . Energy fluxes exhibit complex spatial and temporal patterns throughout both tidal periods. During spring tides, local barotropic forcing is strongest and energy flux over the slope is predominantly offshore (westward). During neap tides, shoaling remotely generated internal tides dominate and energy flux is predominantly onshore (eastward). Shoaling internal tides do not exhibit a strong spring-neap cycle and are also observed during the first spring tide, indicating that they originate from multiple sources. The bulk of the remotely generated internal tide is hypothesized to be generated from south of the array (e.g., Mendocino Escarpment), because energy fluxes at the deep mooring 100 km offshore are always directed northward. However, fluxes on the slope suggest that the northbound internal tide is turned onshore, most likely by reflection from large-scale bathymetry. This is verified with a simple three-dimensional model of mode-1 internal tides propagating obliquely onto a near-critical slope, whose output conforms fairly well to observations, in spite of its simplicity.

Turbulence in a sheared, salt-fingering-favorable environment: Anistropy and effective diffusivities

Kimura, S., W. Smyth, and E. Kunze, "Turbulence in a sheared, salt-fingering-favorable environment: Anistropy and effective diffusivities," J. Phys. Oeanogr., 41, 1144-1159, doi: 10.1175/2011JPO4543.1, 2011.

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1 Jun 2011

Direct numerical simulations (DNS) of a shear layer with salt-fingering-favorable stratification have been performed for different Richardson numbers Ri and density ratios R_rho. In the absence of shear (Ri = infinity), the primary instability is square planform salt fingering, alternating cells of rising and sinking fluid. In the presence of shear, salt fingering takes the form of salt sheets, planar regions of rising and sinking fluid, aligned parallel to the sheared flow. After the onset of secondary instability, the flow becomes turbulent. The continued influence of the primary instability distorts the late-stage structure and hence biases isotropic estimates of the turbulent kinetic energy dissipation rate. In contrast, thermal and saline gradients evolve to become more isotropic than velocity gradients at their dissipation scales. Thus, the standard observational methodology of estimating the turbulent kinetic energy dissipation rate from vertical profiles of microscale gradients and assuming isotropy can underestimate its true value by a factor of 2-3, whereas estimates of thermal and saline dissipation rates using this approach are relatively accurate. Likewise, estimates of Gamma from vertical profiles overestimate the true Gamma by roughly a factor of 2. Salt sheets are ineffective at transporting momentum. Thermal and saline effective diffusivities decrease with decreasing Ri, despite the added energy source provided by background shear. After the transition to turbulence, the thermal to saline flux ratio and the effective Schmidt number remain close to the values predicted by linear theory.

Internal tide reflection and turbulent mixing on the continental slope

Nash, J.D., E. Kunze, J.M. Toole, and R.W. Schmitt, "Internal tide reflection and turbulent mixing on the continental slope," J. Phys. Oceanogr., 34, 1117-1134, doi: 10.1175/1520-0485(2004)034, 2004.

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1 May 2004

Observations of turbulence, internal waves, and subinertial flow were made over a steep, corrugated continental slope off Virginia during May–June 1998. At semidiurnal frequencies, a convergence of low-mode, onshore energy flux is approximately balanced by a divergence of high-wavenumber offshore energy flux. This conversion occurs in a region where the continental slope is nearly critical with respect to the semidiurnal tide. It is suggested that elevated near-bottom mixing observed offshore of the supercritical continental slope arises from the reflection of a remotely generated, low-mode, M2 internal tide. Based on the observed turbulent kinetic energy dissipation rate, the high-wavenumber internal tide decays on time scales O(1 day). No evidence for internal lee wave generation by flow over the slope's corrugations or internal tide generation at the shelf break was found at this site.

Boundary layer intrusions from a sloping bottom: A mechanism for generating intermediate nepheloid layers

McPhee-Shaw, E.E., and E. Kunze, "Boundary layer intrusions from a sloping bottom: A mechanism for generating intermediate nepheloid layers," J. Geophys. Res., 107, 10.1029/2001JC000801, 2002.

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12 Jun 2002

Laboratory experiments were used to investigate the growth of intrusions due to internal-wave reflection from a sloping boundary. When normalized by the incident energy density flux, the average intrusion spreading velocity was found to be a linear function of the frequency ratio ω/ωc, where ω is the frequency of the incident wave and ωc is the critical frequency, at which the wave characteristic has the same angle as the bottom slope. Evenly spaced layers, indicating thin perturbations in the background density gradient, developed within the mixing region and spread into the tank interior. The vertical spacing of these layers also bore a linear relationship to ω/ωc. A linear model of internal-wave reflection suggests that these layers may be related to an isopycnal displacement, or overturn, scale. Intrusion growth occurred at a range around the critical frequency and was strongest at slightly supercritical conditions. A balance relating the spreading rate of intrusions to the divergence of energy density flux across the boundary layer is derived. Fitting the laboratory results to this theoretical prediction suggested a weak net buoyancy flux. This balance might be of use in predicting spreading rates of intermediate nepheloid layers generated by internal-wave mixing at oceanic margins.

Internal wave interactions with equatorial deep jets. Part II: Acceleration of the jets

Muench, J.E. and E. Kunze, "Internal wave interactions with equatorial deep jets. Part II: Acceleration of the jets," J. Phys. Oceanogr., 30, 2099-2110, 2000.

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1 Aug 2000

What drives the equatorial deep jets is a puzzle because of their isolation from surface forcing by the intervening main pycnocline and the Equatorial Undercurrent, and from lateral boundaries by distances of tens of thousands of kilometers. It would take decades for energy to propagate to the jets' midbasin location from boundary sources. Their persistence points to some mechanism maintaining them in situ. The authors hypothesize that the ambient internal wave field deposits momentum fluxes at critical layers within the deep jets and, using calculated momentum- and energy-flux divergences as forcing, estimate acceleration of the mean zonal flow in the deep jets. Internal wave momentum-flux divergences are more than sufficient to sustain the jets, acting to sharpen the shear between the jets on timescales of months to years. Predicted energy-flux divergences produce turbulent dissipation rates compatible with those observed.

Internal wave interactions with equatorial deep jets. Part I: Momentum-flux divergences

Muench, J.E., and E. Kunze, "Internal wave interactions with equatorial deep jets. Part I: Momentum-flux divergences," J. Phys. Oceanogr., 29, 1453-1467, 2000.

1 Jul 1999

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