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  • 1
    Online Resource
    Online Resource
    Heat Transport through Diurnal Warm Layers
    American Meteorological Society ; 2020
    In:  Journal of Physical Oceanography Vol. 50, No. 10 ( 2020-10-01), p. 2885-2905
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 50, No. 10 ( 2020-10-01), p. 2885-2905
    Abstract: Penetration of solar radiation in the upper few meters of the ocean creates a near-surface, stratified diurnal warm layer. Wind stress accelerates a diurnal jet in this layer. Turbulence generated at the diurnal thermocline, where the shear of the diurnal jet is concentrated, redistributes heat downward via mixing. New measurements of temperature and turbulence from fast thermistors on a surface-following platform depict the details of this sequence in both time and depth. Temporally, the sequence at a fixed depth follows a counterclockwise path in log ϵ –log N parameter space. This path also captures the evolution of buoyancy Reynolds number (a proxy for the anisotropy of the turbulence) and Ozmidov scale (a proxy for the outer vertical length scale of turbulence in the absence of the free surface). Vertically, the solar heat flux always leads to heating of fluid parcels in the upper few meters, whereas the turbulent heat flux divergence changes sign across the depth of maximum vertical temperature gradient, cooling fluid parcels above and heating fluid parcels below. In general, our measurements of fluid parcel heating or cooling rates of order 0.1°C h −1 are consistent with our estimates of heat flux divergence. In weak winds ( 〈 2 m s −1 ), sea surface temperature (SST) is controlled by the depth-dependent absorption of solar radiation. In stronger winds, turbulent mixing controls SST.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-20-0079.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2020
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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  • 2
    Online Resource
    Online Resource
    Evolution of Turbulence in the Diurnal Warm Layer
    American Meteorological Society ; 2018
    In:  Journal of Physical Oceanography Vol. 48, No. 2 ( 2018-02), p. 383-396
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 48, No. 2 ( 2018-02), p. 383-396
    Abstract: The daily evolution of temperature, stratification, and turbulence in the diurnal warm layer is described from time series measurements at low to moderate winds and strong insolation in the equatorial Indian Ocean. At 2.0-m depth, turbulence dissipation rates ( ε ) decreased by two orders of magnitude over 1–2 h immediately after sunrise, initiated by stratification caused by penetrating solar radiation prior to the change in sign of net surface heat flux from cooling to warming. Decaying turbulence preceded a period of rapid growth, in which ε increased by two orders of magnitude over a few hours, and following which ε approached a daytime period of near-steady state. Decay and growth rates predicted by a simplified turbulence model are consistent with those observed. During the daytime period of near-steady state, asymmetric temperature ramps were associated with enhanced ε , supporting the interpretation that this period represents a balance between buoyancy and shear production associated with a shear-driven response to trapping of momentum within the diurnal warm layer.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-17-0170.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2018
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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  • 3
    Online Resource
    Online Resource
    Freshwater Lens Fronts Propagating as Buoyant Gravity Currents in the Equatorial Indian Ocean
    American Geophysical Union (AGU) ; 2021
    In:  Journal of Geophysical Research: Oceans Vol. 126, No. 8 ( 2021-08)
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 126, No. 8 ( 2021-08)
    Abstract: Thin, buoyant, near‐surface lenses of freshwater formed by local precipitation were observed in the central equatorial Indian Ocean 50% of observed lenses had sharp lateral interfaces and physical structure similar to gravity currents, including a bulbous leading edge Lens front propagation speeds derived from X‐band radar signatures were equal to their respective long interfacial wave speed
    Type of Medium: Online Resource
    ISSN: 2169-9275 , 2169-9291
    URL: Article
    DOI: 10.1029/2021JC017186
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2021
    detail.hit.zdb_id: 2016804-4
    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 3094219-6
    SSG: 16,13
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  • 4
    Online Resource
    Online Resource
    Deep Cycle Turbulence in Atlantic and Pacific Cold Tongues
    American Geophysical Union (AGU) ; 2022
    In:  Geophysical Research Letters Vol. 49, No. 8 ( 2022-04-28)
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 49, No. 8 ( 2022-04-28)
    Abstract: Massive turbulence data sets from multiyear time series at sites in Pacific and Atlantic cold tongues are compared Diurnal composites document similarities in variability and magnitudes of deep cycle turbulence in Atlantic and Pacific cold tongues A depth/amplitude scaling collapses turbulence dissipation measurements at three cold tongue sites to within a factor of 2
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2021GL097345
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2022
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 5
    Online Resource
    Online Resource
    Upper layer thermohaline structure of the Bay of Bengal during the 2013 northeast monsoon
    Elsevier BV ; 2020
    In:  Deep Sea Research Part II: Topical Studies in Oceanography Vol. 172 ( 2020-02), p. 104630-
    Details
    In: Deep Sea Research Part II: Topical Studies in Oceanography, Elsevier BV, Vol. 172 ( 2020-02), p. 104630-
    Type of Medium: Online Resource
    ISSN: 0967-0645
    URL: Article
    DOI: 10.1016/j.dsr2.2019.07.018
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2020
    detail.hit.zdb_id: 1141627-0
    detail.hit.zdb_id: 1500312-7
    SSG: 14
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  • 6
    Online Resource
    Online Resource
    Evolution of the Velocity Structure in the Diurnal Warm Layer
    American Meteorological Society ; 2020
    In:  Journal of Physical Oceanography Vol. 50, No. 3 ( 2020-03), p. 615-631
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 50, No. 3 ( 2020-03), p. 615-631
    Abstract: The daily formation of near-surface ocean stratification caused by penetrating solar radiation modifies heat fluxes through the air–sea interface, turbulence dissipation in the mixed layer, and the vertical profile of lateral transport. The transport is altered because momentum from wind is trapped in a thin near-surface layer, the diurnal warm layer. We investigate the dynamics of this layer, with particular attention to the vertical shear of horizontal velocity. We first develop a quantitative link between the near-surface shear components that relates the crosswind component to the inertial turning of the along-wind component. Three days of high-resolution velocity observations confirm this relation. Clear colocation of shear and stratification with Richardson numbers near 0.25 indicate marginal instability. Idealized numerical modeling is then invoked to extrapolate below the observed wind speeds. This modeling, together with a simple energetic scaling analysis, provides a rule of thumb that the diurnal shear evolves differently above and below a 2 m s −1 wind speed, with limited sensitivity of this threshold to latitude and mean net surface heat flux. Only above this wind speed is the energy input sufficient to overcome the stabilizing buoyancy flux and thereby induce marginal instability. The differing shear regimes explain differences in the timing and magnitude of diurnal sea surface temperature anomalies.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-19-0207.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2020
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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  • 7
    Online Resource
    Online Resource
    Seasonality and Buoyancy Suppression of Turbulence in the Bay of Bengal
    American Geophysical Union (AGU) ; 2019
    In:  Geophysical Research Letters Vol. 46, No. 8 ( 2019-04-28), p. 4346-4355
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 46, No. 8 ( 2019-04-28), p. 4346-4355
    Abstract: Upper‐ocean turbulence in the Bay of Bengal is quantified using yearlong moored data Turbulence above 25 m was directly related to wind forcing throughout most of the year After SW monsoon surface low‐salinity water suppressed turbulence below 25 m for 3–5 months
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2018GL081577
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2019
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 8
    Online Resource
    Online Resource
    Flippin’ χSOLO, an Upper-Ocean Autonomous Turbulence-Profiling Float
    American Meteorological Society ; 2023
    In:  Journal of Atmospheric and Oceanic Technology Vol. 40, No. 5 ( 2023-05), p. 629-644
    Details
    In: Journal of Atmospheric and Oceanic Technology, American Meteorological Society, Vol. 40, No. 5 ( 2023-05), p. 629-644
    Abstract: A new autonomous turbulence profiling float has been designed, built, and tested in field trials off Oregon. Flippin’ χ SOLO (F χ S) employs a SOLO-II buoyancy engine that not only changes but also shifts ballast to move the center of mass to positions on either side of the center of buoyancy, thus causing F χ S to flip . F χ S is outfitted with a full suite of turbulence sensors—two shear probes, two fast thermistors, and pitot tube, as well as a pressure sensor and three-axis linear accelerometers. F χ S descends and ascends with turbulence sensors leading, thereby permitting measurement through the sea surface. The turbulence sensors are housed antipodal from communication antennas so as to eliminate flow disturbance. By flipping at the sea surface, antennas are exposed for communications. The mission of F χ S is to provide intensive profiling measurements of the upper ocean from 240 m and through the sea surface, particularly during periods of extreme surface forcing. While surfaced, accelerometers provide estimates of wave height spectra and significant wave height. From 3.5 day field trials, here we evaluate (i) the statistics from two F χ S units and our established shipboard profiler, Chameleon, and (ii) F χ S-based wave statistics by comparison to a nearby NOAA wave buoy. Significance Statement The oceanographic fleet of Argo autonomous profilers yields important data that define the state of the ocean’s interior. Continued deployments over time define the evolution of the ocean’s interior. A significant next step will be to include turbulence measurements on these profilers, leading to estimates of thermodynamic mixing rates that predict future states of the ocean’s interior. An autonomous turbulence profiler that employs the buoyancy engine, mission logic, and remote communication of one particular Argo float is described herein. The Flippin’ χ SOLO is an upper-ocean profiler tasked with rapid and continuous profiling of the upper ocean during weather conditions that preclude shipboard profiling and that includes the upper 10 m that is missed by shipboard turbulence profilers.
    Type of Medium: Online Resource
    ISSN: 0739-0572 , 1520-0426
    URL: Article
    DOI: 10.1175/JTECH-D-22-0067.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2023
    detail.hit.zdb_id: 2021720-1
    detail.hit.zdb_id: 48441-6
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  • 9
    Online Resource
    Online Resource
    The Unpredictable Nature of Internal Tides on Continental Shelves
    American Meteorological Society ; 2012
    In:  Journal of Physical Oceanography Vol. 42, No. 11 ( 2012-11-01), p. 1981-2000
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 42, No. 11 ( 2012-11-01), p. 1981-2000
    Abstract: Packets of nonlinear internal waves (NLIWs) in a small area of the Mid-Atlantic Bight were 10 times more energetic during a local neap tide than during the preceding spring tide. This counterintuitive result cannot be explained if the waves are generated near the shelf break by the local barotropic tide since changes in shelfbreak stratification explain only a small fraction of the variability in barotropic to baroclinic conversion. Instead, this study suggests that the occurrence of strong NLIWs was caused by the shoaling of distantly generated internal tides with amplitudes that are uncorrelated with the local spring-neap cycle. An extensive set of moored observations show that NLIWs are correlated with the internal tide but uncorrelated with barotropic tide. Using harmonic analysis of a 40-day record, this study associates steady-phase motions at the shelf break with waves generated by the local barotropic tide and variable-phase motions with the shoaling of distantly generated internal tides. The dual sources of internal tide energy (local or remote) mean that shelf internal tides and NLIWs will be predictable with a local model only if the locally generated internal tides are significantly stronger than shoaling internal tides. Since the depth-integrated internal tide energy in the open ocean can greatly exceed that on the shelf, it is likely that shoaling internal tides control the energetics on shelves that are directly exposed to the open ocean.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-12-028.1
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2012
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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  • 10
    Online Resource
    Online Resource
    Stratified shear instabilities in diurnal warm layers
    American Meteorological Society ; 2021
    In:  Journal of Physical Oceanography ( 2021-05-25)
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, ( 2021-05-25)
    Abstract: In low winds (≲2 m s −1 ), diurnal warm layers form but shear in the near-surface jet is too weak to generate shear instability and mixing. In high winds (≳8ms −1 ), surface heat is rapidly mixed downward and diurnal warm layers do not form. Under moderate winds of 3–5 m s −1 , the jet persists for several hours in a state that is susceptible to shear instability. We observe low Richardson numbers of Ri ≈ 0.1 in the top 2 m between 10:00 and 16:00 local time (from 4 h after sunrise to 2 h before sunset). Despite Ri being well below the Ri = 1/4 threshold, instabilities do not grow quickly, nor do they overturn. The stabilizing influence of the sea surface limits growth, a result demonstrated by both linear stability analysis and two-dimensional simulations initialized from observed profiles. In some cases, growth rates are sufficiently small (≪1 h −1 ) that mixing is not expected even though Ri 〈 1/4. This changes around 16:00–17:00. Thereafter, convective cooling causes the region of unstable flow to move downward, away from the surface. This allows shear instabilities to grow an order of magnitude faster and mix effectively. We corroborate the overall observed diurnal cycle of instability with a freely evolving, two-dimensional simulation that is initialized from rest before sunrise.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-20-0300.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2021
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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