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  • 1
    Online Resource
    Online Resource
    An Estimate of Tidal Energy Lost to Turbulence at the Hawaiian Ridge
    American Meteorological Society ; 2006
    In:  Journal of Physical Oceanography Vol. 36, No. 6 ( 2006-06-01), p. 1148-1164
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 36, No. 6 ( 2006-06-01), p. 1148-1164
    Abstract: An integrated analysis of turbulence observations from four unique instrument platforms obtained over the Hawaiian Ridge leads to an assessment of the vertical, cross-ridge, and along-ridge structure of turbulence dissipation rate and diffusivity. The diffusivity near the seafloor was, on average, 15 times that in the midwater column. At 1000-m depth, the diffusivity atop the ridge was 30 times that 10 km off the ridge, decreasing to background oceanic values by 60 km. A weak (factor of 2) spring–neap variation in dissipation was observed. The observations also suggest a kinematic relationship between the energy in the semidiurnal internal tide (E) and the depth-integrated dissipation (D), such that D ∼ E1±0.5 at sites along the ridge. This kinematic relationship is supported by combining a simple knife-edge model to estimate internal tide generation, with wave–wave interaction time scales to estimate dissipation. The along-ridge kinematic relationship and the observed vertical and cross-ridge structures are used to extrapolate the relatively sparse observations along the length of the ridge, giving an estimate of 3 ± 1.5 GW of tidal energy lost to turbulence dissipation within 60 km of the ridge. This is roughly 15% of the energy estimated to be lost from the barotropic tide.
    Type of Medium: Online Resource
    ISSN: 1520-0485 , 0022-3670
    URL: Article
    DOI: 10.1175/JPO2885.1
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2006
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  • 2
    Online Resource
    Online Resource
    Saturation of the internal tide over the inner continental shelf. Part II: Parameterization
    American Meteorological Society ; 2021
    In:  Journal of Physical Oceanography ( 2021-06-02)
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, ( 2021-06-02)
    Abstract: Here, we develop a framework for understanding the observations presented in the accompanying paper (Part I) by Becherer et al. (2021). In this framework, the internal tide saturates as it shoals due to amplitude limitation with decreasing water depth ( H ). From this framework evolves estimates of averaged energetics of the internal tide; specifically, energy, 〈 APE 〉, energy flux, 〈 F E 〉, and energy flux divergence, ∂ x 〈 F E 〉. Since we observe that 〈 D 〉 ≈ ∂ x 〈 F E 〉, we also interpret our estimate of ∂ x 〈 F E 〉 as 〈 D 〉. These estimates represent a parameterization of the energy in the internal tide as it saturates over the inner continental shelf. The parameterization depends solely on depth-mean stratification and bathymetry. A summary result is that the cross-shelf depth dependencies of 〈 APE 〉, 〈 F E 〉 and ∂ x 〈 F E 〉 are analogous to those for shoaling surface gravity waves in the surf zone, suggesting that the inner shelf is the surf zone for the internal tide . A test of our simple parameterization against a range of data sets suggests that it is broadly applicable.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-21-0047.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2021
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  • 3
    Online Resource
    Online Resource
    Air–Sea Interactions from Westerly Wind Bursts During the November 2011 MJO in the Indian Ocean
    American Meteorological Society ; 2014
    In:  Bulletin of the American Meteorological Society Vol. 95, No. 8 ( 2014-08), p. 1185-1199
    Details
    In: Bulletin of the American Meteorological Society, American Meteorological Society, Vol. 95, No. 8 ( 2014-08), p. 1185-1199
    Type of Medium: Online Resource
    ISSN: 0003-0007 , 1520-0477
    URL: Article
    DOI: 10.1175/BAMS-D-12-00225.1
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2014
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  • 4
    Online Resource
    Online Resource
    A new method for estimating the turbulent heat flux at the bottom of the daily mixed layer
    American Geophysical Union (AGU) ; 1988
    In:  Journal of Geophysical Research: Oceans Vol. 93, No. C11 ( 1988-11-15), p. 14005-14012
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 93, No. C11 ( 1988-11-15), p. 14005-14012
    Abstract: A new method is presented for estimating the vertical turbulent heat flux at the bottom of the daily mixed layer from the temperature data in the mixed layer and net solar irradiance data at the sea surface. We assume that fluctuations in the divergence of advective heat flux have longer than daily time scales. The method is applied to data from the eastern tropical Pacific, where the daily cycle in the temperature field is confined to the upper 10–25 m. The night‐to‐day difference of the turbulent heat flux calculated from the data obtained during nine daily cycles in November 1984 agrees well on average with the same quantity estimated from microstructure observations. The night‐to‐day difference of the turbulent heat flux, estimated at several mooring stations near the equator (an average over 100 to 300 daily cycles), varies from 120 to 220 W/m 2 with larger values on the equator. Equatorial turbulence measurements show that the turbulent heat flux is much larger during nighttime than daytime. Therefore the present estimates give approximately the nighttime average, which is the major part of the turbulent heat flux. From the daytime heat budget we obtain divergence of the low‐frequency horizontal heat advection at 1°30′S, 140°W; it is governed by equatorial mesoscale fluctuations having a predominant period of 15–20 days.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/JC093iC11p14005
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1988
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    SSG: 16,13
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  • 5
    Online Resource
    Online Resource
    Turbulence Asymmetries in Bottom Boundary Layer Velocity Pulses Associated with Onshore-Propagating Nonlinear Internal Waves
    American Meteorological Society ; 2020
    In:  Journal of Physical Oceanography Vol. 50, No. 8 ( 2020-08-01), p. 2373-2391
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 50, No. 8 ( 2020-08-01), p. 2373-2391
    Abstract: The inner shelf is a region inshore of that part of the shelf that roughly obeys Ekman dynamics and offshore of the surf zone. Importantly, this is where surface and bottom boundary layers are in close proximity, overlap, and interact. The internal tide carries a substantial amount of energy into the inner shelf region were it eventually dissipates and contributes to mixing. A part of this energy transformation is due to a complex interaction with the bottom, where distinctions between nonlinear internal waves of depression and elevation are blurred, indeed, where polarity reversals of incoming waves take place. From an intensive set of measurements over the inner shelf off central California, we identify salient differences between onshore pulses from waves with properties of elevation waves and offshore pulses from shallowing depression waves. While the velocity structures and amplitudes of on/offshore pulses 1 m above the seafloor are not detectably different, onshore pulses are both more energetically turbulent and carry more sediments than offshore pulses. Their turbulence is also oppositely skewed: onshore pulses slightly to the leading edges, offshore pulses to the trailing edges of the pulses. We consider in turn three independent mechanisms that may contribute to the observed asymmetry: propagation in adverse pressure gradients and the resultant inflection point instability, residence time of a fluid parcel in the pulse, and turbulence suppression by stratification. The first mechanism may largely explain higher turbulence in the trailing edge of offshore pulses. The extended residence time may be responsible for the high and more uniform turbulence distribution across onshore compared to offshore pulses. Stratification does not play a leading role in turbulence modification inside of the pulses 1 m above the bed.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-19-0178.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2020
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  • 6
    Online Resource
    Online Resource
    Saturation of the internal tide over the inner continental shelf. Part I: Observations
    American Meteorological Society ; 2021
    In:  Journal of Physical Oceanography ( 2021-05-14)
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, ( 2021-05-14)
    Abstract: Broadly-distributed measurements of velocity, density and turbulence spanning the inner shelf off central California indicate that (i) the average shoreward-directed internal tide energy flux (〈 F E 〉) decreases to near 0 at the 25 m isobath; (ii) the vertically-integrated turbulence dissipation rate (〈 D 〉) is approximately equal to the flux divergence of internal tide energy ( ∂ x 〈 F E 〉); (iii) the ratio of turbulence energy dissipation in the interior relative to the bottom boundary layer (BBL) decreases toward shallow waters; (iv) going inshore, 〈 F E 〉 becomes decorrelated with the incoming internal wave energy flux; and (v) 〈 F E 〉 becomes increasingly correlated with stratification toward shallower water.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-20-0264.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2021
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    detail.hit.zdb_id: 184162-2
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  • 7
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    Online Resource
    The Inner-Shelf Dynamics Experiment
    American Meteorological Society ; 2021
    In:  Bulletin of the American Meteorological Society Vol. 102, No. 5 ( 2021-05), p. E1033-E1063
    Details
    In: Bulletin of the American Meteorological Society, American Meteorological Society, Vol. 102, No. 5 ( 2021-05), p. E1033-E1063
    Abstract: The inner shelf, the transition zone between the surfzone and the midshelf, is a dynamically complex region with the evolution of circulation and stratification driven by multiple physical processes. Cross-shelf exchange through the inner shelf has important implications for coastal water quality, ecological connectivity, and lateral movement of sediment and heat. The Inner-Shelf Dynamics Experiment (ISDE) was an intensive, coordinated, multi-institution field experiment from September–October 2017, conducted from the midshelf, through the inner shelf, and into the surfzone near Point Sal, California. Satellite, airborne, shore- and ship-based remote sensing, in-water moorings and ship-based sampling, and numerical ocean circulation models forced by winds, waves, and tides were used to investigate the dynamics governing the circulation and transport in the inner shelf and the role of coastline variability on regional circulation dynamics. Here, the following physical processes are highlighted: internal wave dynamics from the midshelf to the inner shelf; flow separation and eddy shedding off Point Sal; offshore ejection of surfzone waters from rip currents; and wind-driven subtidal circulation dynamics. The extensive dataset from ISDE allows for unprecedented investigations into the role of physical processes in creating spatial heterogeneity, and nonlinear interactions between various inner-shelf physical processes. Overall, the highly spatially and temporally resolved oceanographic measurements and numerical simulations of ISDE provide a central framework for studies exploring this complex and fascinating region of the ocean.
    Type of Medium: Online Resource
    ISSN: 0003-0007 , 1520-0477
    URL: Article
    DOI: 10.1175/BAMS-D-19-0281.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2021
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    detail.hit.zdb_id: 419957-1
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  • 8
    Online Resource
    Online Resource
    Observations of Shoaling Nonlinear Internal Bores across the Central California Inner Shelf
    American Meteorological Society ; 2020
    In:  Journal of Physical Oceanography Vol. 50, No. 1 ( 2020-01), p. 111-132
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 50, No. 1 ( 2020-01), p. 111-132
    Abstract: We present observations of shoaling nonlinear internal bores off the coast of central California. The dataset includes 15 moorings deployed during September–October 2017 and cross-shore shipboard surveys. We describe the cross-shore structure and evolution of large-amplitude internal bores as they transit from 9 km (100-m depth) to 1 km offshore (10 m). We observe that two bores arrive each semidiurnal period, both propagating from the southwest; of the total, 72% are tracked to the 10-m isobath. The bore speeds are subtidally modulated, but there is additional bore-to-bore speed variability that is unexplained by the upstream stratification. We quantify temporal and cross-shore variability of the waveguide (the background conditions through which bores propagate) by calculating the linear longwave nonrotating phase speed c o and using the nonlinearity coefficient of the Korteweg–de Vries equation α as a metric for stratification. Bore fronts are generally steeper when α is positive and are more rarefied when α is negative, and we observe the bore’s leading edge to rarefy from a steep front when α is positive offshore and negative inshore. High-frequency α fluctuations, such as those nearshore driven by wind relaxations, contribute to bore-to-bore variability of the cross-shore evolution during similar subtidal waveguide conditions. We compare observed bore speeds with c o and the rotating group velocities c g , concluding that observed speeds are always faster than c g and are slower than c o at depths greater than 32 m and faster than c o at depths of less than 32 m. The bores maintain a steady speed while transiting into shallower water, contrary to linear estimates that predict bores to slow.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-19-0125.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2020
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    detail.hit.zdb_id: 184162-2
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  • 9
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    Online Resource
    Damping of Inertial Motions through the Radiation of Near-Inertial Waves in a Dipole Vortex in the Iceland Basin
    American Meteorological Society ; 2023
    In:  Journal of Physical Oceanography Vol. 53, No. 8 ( 2023-08), p. 1821-1833
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 53, No. 8 ( 2023-08), p. 1821-1833
    Abstract: Along with boundary layer turbulence, downward radiation of near-inertial waves (NIWs) damps inertial oscillations (IOs) in the surface ocean; however, the latter can also energize abyssal mixing. Here we present observations made from a dipole vortex in the Iceland Basin where, after the period of direct wind forcing, IOs lost over half their kinetic energy (KE) in two inertial periods to radiation of NIWs with minimal turbulent dissipation of KE. The dipole’s vorticity gradient led to a rapid reduction in the NIW’s lateral wavelength via ζ refraction that was accompanied by isopycnal undulations below the surface mixed layer. Pressure anomalies associated with the undulations were correlated with the NIW’s velocity yielding an energy flux of 310 mW m −2 pointed antiparallel to the vorticity gradient and a downward flux of 1 mW m −2 capable of driving the observed drop in KE. The minimal role of turbulence in the energetics after the IOs had been generated by the winds was confirmed using a large-eddy simulation driven by the observed winds. Significance Statement We report direct observational estimates of the vector wave energy flux of a near-inertial wave. The energy flux points from high to low vorticity in the horizontal, consistent with the theory of ζ refraction. The downward energy flux dominates the observed damping of inertial motions over turbulent dissipation and mixing.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-22-0202.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2023
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  • 10
    Online Resource
    Online Resource
    Monitoring geostrophic currents at the equator
    Elsevier BV ; 1987
    In:  Deep Sea Research Part A. Oceanographic Research Papers Vol. 34, No. 7 ( 1987-7), p. 1149-1161
    Details
    In: Deep Sea Research Part A. Oceanographic Research Papers, Elsevier BV, Vol. 34, No. 7 ( 1987-7), p. 1149-1161
    Type of Medium: Online Resource
    ISSN: 0198-0149
    URL: Article
    DOI: 10.1016/0198-0149(87)90069-0
    Language: English
    Publisher: Elsevier BV
    Publication Date: 1987
    detail.hit.zdb_id: 2280519-9
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