46 results on '"Alford, Matthew H."'
Search Results
2. Near-slope turbulence in a Rockall canyon
- Author
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van Haren, Hans, Voet, Gunnar, Alford, Matthew H, Fernández-Castro, Bieito, Garabato, Alberto C Naveira, Wynne-Cattanach, Bethan L, Mercier, Herlé, and Messias, Marie-José
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Earth Sciences ,Oceanography ,Geochemistry ,Geology - Published
- 2024
3. Observations of diapycnal upwelling within a sloping submarine canyon
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Wynne-Cattanach, Bethan L., Couto, Nicole, Drake, Henri F., Ferrari, Raffaele, Le Boyer, Arnaud, Mercier, Herlé, Messias, Marie-José, Ruan, Xiaozhou, Spingys, Carl P., van Haren, Hans, Voet, Gunnar, Polzin, Kurt, Naveira Garabato, Alberto C., and Alford, Matthew H.
- Published
- 2024
- Full Text
- View/download PDF
4. Interacting internal waves explain global patterns of interior ocean mixing
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Dematteis, Giovanni, Boyer, Arnaud Le, Pollmann, Friederike, Polzin, Kurt L., Alford, Matthew H., Whalen, Caitlin B., and Lvov, Yuri V.
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Physics - Atmospheric and Oceanic Physics ,Nonlinear Sciences - Chaotic Dynamics ,Physics - Fluid Dynamics ,Physics - Geophysics - Abstract
Across the stable density stratification of the abyssal ocean, deep dense water is slowly propelled upward by sustained, though irregular, turbulent mixing. The resulting mean upwelling determines large-scale oceanic circulation properties like heat and carbon transport. In the ocean interior, this turbulent mixing is caused mainly by breaking internal waves: generated predominantly by winds and tides, these waves interact nonlinearly, transferring energy downscale, and finally become unstable, break and mix the water column. This paradigm, long parameterized heuristically, still lacks full theoretical explanation. Here, we close this gap using wave-wave interaction theory with input from both localized and global observations. We find near-ubiquitous agreement between first-principle predictions and observed mixing patterns in the global ocean interior. Our findings lay the foundations for a wave-driven mixing parameterization for ocean general circulation models that is entirely physics-based, which is key to reliably represent future climate states that could differ substantially from today's.
- Published
- 2023
5. Frequency dependence of near-surface oceanic kinetic energy from drifter observations and global high-resolution models
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Arbic, Brian K., Elipot, Shane, Brasch, Jonathan M., Menemenlis, Dimitris, Ponte, Aurelien L., Shriver, Jay F., Yu, Xiaolong, Zaron, Edward D., Alford, Matthew H., Buijsman, Maarten C., Abernathey, Ryan, Garcia, Daniel, Guan, Lingxiao, Martin, Paige E., and Nelson, Arin D.
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Physics - Atmospheric and Oceanic Physics ,Physics - Geophysics - Abstract
The geographical variability, frequency content, and vertical structure of near-surface oceanic kinetic energy (KE) are important for air-sea interaction, marine ecosystems, operational oceanography, pollutant tracking, and interpreting remotely sensed velocity measurements. Here, KE in high-resolution global simulations (HYbrid Coordinate Ocean Model; HYCOM, and Massachusetts Institute of Technology general circulation model; MITgcm), at the sea surface (0 m) and 15 m, are respectively compared with KE from undrogued and drogued surface drifters. Global maps and zonal averages are computed for low-frequency ($<$ 0.5 cpd), near-inertial, diurnal, and semi-diurnal bands. Both models exhibit low-frequency equatorial KE that is low relative to drifter values. HYCOM near-inertial KE is higher than in MITgcm, and closer to drifter values, probably due to more frequently updated atmospheric forcing. HYCOM semi-diurnal KE is lower than in MITgcm, and closer to drifter values, likely due to inclusion of a parameterized topographic internal wave drag. A concurrent tidal harmonic analysis in the diurnal band demonstrates that much of the diurnal flow is non-tidal. We compute a simple proxy of near-surface vertical structure, the ratio of 0 m KE to 0 m KE plus 15 m KE in model outputs, and undrogued KE to undrogued KE plus drogued KE in drifter observations. Over most latitudes and frequency bands, model ratios track the drifter ratios to within error bars. Values of this ratio demonstrate significant vertical structure in all frequency bands except the semidiurnal band. Latitudinal dependence in the ratio is greatest in diurnal and low-frequency bands., Comment: revised for AGU JGR: Oceans
- Published
- 2022
6. An in situ study of abyssal turbidity-current sediment plumes generated by a deep seabed polymetallic nodule mining preprototype collector vehicle
- Author
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Muñoz-Royo, Carlos, Ouillon, Raphael, El Mousadik, Souha, Alford, Matthew H, and Peacock, Thomas
- Abstract
An in situ study to investigate the dynamics of sediment plumes near the release from a deep seabed polymetallic nodule mining preprototype collector vehicle was conducted in the Clarion Clipperton Zone in the Pacific Ocean 4500-m deep. The experiments reveal that the excess density of the released sediment-laden water leads to a low-lying, laterally spreading turbidity current. At the time of measurement, 2 to 8% of the sediment mass were detected 2 m or higher above the seabed and were not observed to settle over several hours, with the remaining 92 to 98% below 2 m and some fraction of that locally deposited. Our results suggest that turbidity current dynamics sets the fraction of sediment remaining suspended and the scale of the subsequent ambient sediment plume. The implications of this process, which is characteristically overlooked in previous modeling efforts, are substantial for plume modeling that will lie at the heart of environmental impact statements for regulatory consideration.
- Published
- 2022
7. Oceanic turbulence from a planktonic perspective
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Franks, Peter JS, Inman, Bryce G, MacKinnon, Jennifer A, Alford, Matthew H, and Waterhouse, Amy F
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Earth Sciences ,Environmental Sciences ,Biological Sciences ,Marine Biology & Hydrobiology - Abstract
The potential influences of turbulence on planktonic processes such as nutrient uptake, grazing, predation, infection, and mating have been explored in hundreds of laboratory and theoretical studies. However, the turbulence levels used may not represent those experienced by oceanic plankton, bringing into question their relevance for understanding planktonic dynamics in the ocean. Here, we take a data-centric approach to understand the turbulence climate experienced by plankton in the ocean, analyzing over one million turbulence measurements acquired in the open ocean. Median dissipation rates in the upper 100 m were < 10−8 W kg−1, with 99% of the observations < 10−6 W kg−1. Below mixed layers, the median dissipation rate was ~ 10−10 W kg−1, with 99% of the observations < 10−7 W kg−1. Even in strongly mixing layers the median dissipation rates rarely reached 10−5 W kg−1, decreasing by orders of magnitude over 10 m or less in depth. Furthermore, episodes of intense turbulence were transient, transitioning to background levels within 10 min or less. We define three turbulence conditions in the ocean: weak (< 10−8 W kg−1), moderate (10−8–10−6 W kg−1), and strong (> 10−6 W kg−1). Even the strongest of these is much weaker than those used in most laboratory experiments. The most frequent turbulence levels found in this study are weak enough for most plankton—including small protists—to outswim them, and to allow chemical plumes and trails to persist for tens of minutes. Our analyses underscore the primary importance of planktonic behavior in driving individual interactions.
- Published
- 2022
8. Breaking Internal Waves and Ocean Diapycnal Diffusivity in a High‐Resolution Regional Ocean Model: Evidence of a Wave‐Turbulence Cascade
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Momeni, Kayhan, primary, Ma, Yuchen, additional, Peltier, William R., additional, Menemenlis, Dimitris, additional, Thakur, Ritabrata, additional, Pan, Yulin, additional, Arbic, Brian K., additional, Skitka, Joseph, additional, and Alford, Matthew H., additional
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- 2024
- Full Text
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9. Observations and Numerical Simulations of the Onset and Growth of Langmuir Circulations
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Andriatis, Alexander, primary, Lenain, Luc, additional, Alford, Matthew H., additional, Winstead, Nathaniel, additional, and Geiman, Joseph, additional
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- 2024
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10. Internal wave breaking near the foot of a steep East-Pacific continental slope
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van Haren, Hans, Voet, Gunnar, Alford, Matthew H., and Torres, Daniel J.
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- 2022
- Full Text
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11. Near-slope turbulence in a Rockall canyon
- Author
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van Haren, Hans, primary, Voet, Gunnar, additional, Alford, Matthew H., additional, Fernández-Castro, Bieito, additional, Naveira Garabato, Alberto C., additional, Wynne-Cattanach, Bethan L., additional, Mercier, Herlé, additional, and Messias, Marie-José, additional
- Published
- 2024
- Full Text
- View/download PDF
12. An in situ study of abyssal turbidity-current sediment plumes generated by a deep seabed polymetallic nodule mining preprototype collector vehicle
- Author
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Muñoz-Royo, Carlos, Ouillon, Raphael, El Mousadik, Souha, Alford, Matthew H., Peacock, Thomas, Muñoz-Royo, Carlos, Ouillon, Raphael, El Mousadik, Souha, Alford, Matthew H., and Peacock, Thomas
- Abstract
An in situ study to investigate the dynamics of sediment plumes near the release from a deep seabed polymetallic nodule mining preprototype collector vehicle was conducted in the Clarion Clipperton Zone in the Pacific Ocean 4500-m deep. The experiments reveal that the excess density of the released sediment-laden water leads to a low-lying, laterally spreading turbidity current. At the time of measurement, 2 to 8% of the sediment mass were detected 2 m or higher above the seabed and were not observed to settle over several hours, with the remaining 92 to 98% below 2 m and some fraction of that locally deposited. Our results suggest that turbidity current dynamics sets the fraction of sediment remaining suspended and the scale of the subsequent ambient sediment plume. The implications of this process, which is characteristically overlooked in previous modeling efforts, are substantial for plume modeling that will lie at the heart of environmental impact statements for regulatory consideration.
- Published
- 2024
13. Advection–diffusion settling of deep-sea mining sediment plumes. Part 2. Collector plumes
- Author
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Ouillon, Raphael, Muñoz-Royo, Carlos, Alford, Matthew H., Peacock, Thomas, Ouillon, Raphael, Muñoz-Royo, Carlos, Alford, Matthew H., and Peacock, Thomas
- Abstract
We develop and investigate an advection–diffusion-settling model of deep-sea mining collector plumes, building on the analysis of midwater plumes in Part 1. In the case of collector plumes, deposition plays a predominant role in controlling the mass of sediment in suspension, and thus on setting the extent of the plume. We first discuss the competition between settling, which leads to deposition, and vertical turbulent diffusion, which stretches the plume vertically and reduces deposition. The time evolution of the concentration at the seabed is found to be a highly nonlinear function of time that depends non-trivially on the ratio of diffusion to settling time scales. This has direct implications for the three extent metrics considered, namely the instantaneous area of the seabed where a deposition rate threshold is exceeded, the furthest distance from the discharge where the plume exceeds a concentration threshold and the volume flux of fluid in the water column that ever exceeds a concentration threshold. Unlike the midwater plume, the particle velocity distribution of the sediment has the greatest influence on the extent metrics. The turbulence levels experienced by the plume also markedly affects its extent. Expected variability of turbulence and particle settling velocity yields orders of magnitude changes in the extent metrics.
- Published
- 2024
14. Advection-diffusion-settling of deep-sea mining sediment plumes. Part 1: Midwater plumes
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Ouillon, Raphael, Muñoz-Royo, Carlos, Alford, Matthew H., Peacock, Thomas, Ouillon, Raphael, Muñoz-Royo, Carlos, Alford, Matthew H., and Peacock, Thomas
- Abstract
The evolution of midwater sediment plumes associated with deep-sea mining activities is investigated in the passive-transport phase using a simplified advection–diffusion-settling model. Key metrics that characterize the extent of plumes are defined based on a concentration threshold. Namely, we consider the volume flux of fluid that ever exceeds a concentration threshold, the furthest distance from and maximum depth below the intrusion where the plume exceeds the threshold, and the instantaneous volume of fluid in excess of the threshold. Formulas are derived for the metrics that provide insight into the parameters that most strongly affect the extent of the plume. The model is applied to a reference deep-sea mining scenario around which key parameters are varied. The results provide some sense of scale for deep-sea mining midwater plumes, but more significantly demonstrate the importance of the parameters that influence the evolution of midwater plumes. The model shows that the discharge mass flow rate and the concentration threshold play an equal and opposite role on setting the extent of the plume. Ambient ocean turbulence and the settling velocity distribution of particles play a lesser yet significant role on setting the extent, and can influence different metrics in opposing ways.
- Published
- 2024
15. Surface and Sub‐Surface Kinetic Energy Wavenumber‐Frequency Spectra in Global Ocean Models and Observations.
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Ansong, Joseph K., Arbic, Brian K., Nelson, Arin D., Alford, Matthew H., Kunze, Eric, Menemenlis, Dimitris, Savage, Anna C., Shriver, Jay F., Wallcraft, Alan J., and Buijsman, Maarten C.
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KINETIC energy ,OCEAN surface topography ,INTERNAL waves ,GRAVITY waves ,GENERAL circulation model ,OCEANOGRAPHY - Abstract
This paper examines spectra of horizontal kinetic energy (HKE) in the surface and sub‐surface ocean, with an emphasis on internal gravity wave (IGW) motions, in global high‐resolution ocean simulations. Horizontal wavenumber‐frequency spectra of surface HKE are computed over seven oceanic regions from two global simulations of the HYbrid Coordinate Ocean Model (HYCOM) and three global simulations of the Massachusetts Institute of Technology general circulation model (MITgcm). In regions with high IGW activity, high surface HKE variance in the horizontal wavenumber‐frequency spectra is aligned along IGW linear dispersion curves. For both HYCOM and MITgcm, and in almost all regions, finer horizontal resolution yields more energetic supertidal IGW continuum spectra. The ratio of high‐horizontal‐wavenumber variance in semi‐diurnal and supertidal motions relative to lower‐frequency motions, a quantity of great interest for swath altimetry, depends on the model employed and the horizontal resolution within the model, implying that quantitative predictions of the partition between low‐ and high‐frequency motions taken from particular simulations should be treated with care. The frequency‐vertical wavenumber spectra, frequency spectra, and vertical wavenumber spectra from the models are compared to spectra computed from McLane profilers at nine locations. In general, MITgcm spectra match the McLane profiler spectra more closely at high frequencies (|ω| > 4.5 cpd). In both models, vertical wavenumber spectra roll off more steeply than observations at high vertical wavenumbers (m > 10−2 cpm). The vertical wavenumber spectra in such models is an important target for improvement, due to turbulence production and dissipation that takes place at high vertical wavenumbers. Plain Language Summary: Recently, a small but growing number of global ocean models have begun to employ simultaneous tidal and atmospheric forcing. At the same time, increasing supercomputer power has allowed for simulations of oceanic motions with increasing accuracy, increasing feature (spatial) resolution, and more frequent time slices. Global ocean models with fine grid spacing, and simultaneous tidal and atmospheric forcing, host a vigorous spectrum of high‐frequency waves that control mixing over most of the ocean water column, and are important for many operational oceanography challenges. As an example of the latter, high‐resolution global internal wave models have been used to study the relative partition of high‐frequency versus low‐frequency motions at the small horizontal scales that will be measured by the new Surface Water Ocean Topography mission. The partition described above depends on the model employed and the grid spacing employed within that model, meaning that conclusions about the partition are dependent on the model used to estimate it. Comparisons between the models and vertically profiling instruments indicate that resolving fine scale motions in the vertical direction, where ocean mixing takes place, is not yet handled well by the models. Modeling of fine‐vertical scale motions is therefore an important future research direction. Key Points: Vertical wavenumber spectra of internal gravity wave kinetic energy in two high‐resolution global models are compared to observed spectraModels under‐estimate motions at high vertical wavenumbers (small vertical scales), flagging this as a target for model improvementThe ratio of high‐ versus low‐frequency surface kinetic energy at small horizontal scales is dependent on the model and grid spacings employed [ABSTRACT FROM AUTHOR]
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- 2024
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16. Turbulent diapycnal fluxes as a pilot Essential Ocean Variable.
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Le Boyer, Arnaud, Couto, Nicole, Alford, Matthew H., Drake, Henri F., Bluteau, Cynthia E., Hughes, Kenneth G., Naveira Garabato, Alberto C., Moulin, Aurélie J., Peacock, Thomas, Fine, Elizabeth C., Mashayek, Ali, Cimoli, Laura, Meredith, Michael P., Melet, Angelique, Fer, Ilker, Dengler, Marcus, and Stevens, Craig L.
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EDDY flux ,GLOBAL Ocean Observing System ,OCEAN ,FOREIGN exchange rates ,KINETIC energy - Abstract
We contend that ocean turbulent fluxes should be included in the list of Essential Ocean Variables (EOVs) created by the Global Ocean Observing System. This list aims to identify variables that are essential to observe to inform policy and maintain a healthy and resilient ocean. Diapycnal turbulent fluxes quantify the rates of exchange of tracers (such as temperature, salinity, density or nutrients, all of which are already EOVs) across a density layer. Measuring them is necessary to close the tracer concentration budgets of these quantities. Measuring turbulent fluxes of buoyancy (Jb), heat (Jq), salinity (JS) or any other tracer requires either synchronous microscale (a few centimeters) measurements of both the vector velocity and the scalar (e.g., temperature) to produce time series of the highly correlated perturbations of the two variables, or microscale measurements of turbulent dissipation rates of kinetic energy (e) and of thermal/salinity/tracer variance (c), from which fluxes can be derived. Unlike isopycnal turbulent fluxes, which are dominated by the mesoscale (tens of kilometers), microscale diapycnal fluxes cannot be derived as the product of existing EOVs, but rather require observations at the appropriate scales. The instrumentation, standardization of measurement practices, and data coordination of turbulence observations have advanced greatly in the past decade and are becoming increasingly robust. With more routine measurements, we can begin to unravel the relationships between physical mixing processes and ecosystem health. In addition to laying out the scientific relevance of the turbulent diapycnal fluxes, this review also compiles the current developments steering the community toward such routine measurements, strengthening the case for registering the turbulent diapycnal fluxes as an pilot Essential Ocean Variable. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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17. Turbulent diapycnal fluxes as a pilot Essential Ocean Variable
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Le Boyer, Arnaud, primary, Couto, Nicole, additional, Alford, Matthew H., additional, Drake, Henri F., additional, Bluteau, Cynthia E., additional, Hughes, Kenneth G., additional, Naveira Garabato, Alberto C., additional, Moulin, Aurélie J., additional, Peacock, Thomas, additional, Fine, Elizabeth C., additional, Mashayek, Ali, additional, Cimoli, Laura, additional, Meredith, Michael P., additional, Melet, Angelique, additional, Fer, Ilker, additional, Dengler, Marcus, additional, and Stevens, Craig L., additional
- Published
- 2023
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18. A warm jet in a cold ocean
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MacKinnon, Jennifer A., Simmons, Harper L., Hargrove, John, Thomson, Jim, Peacock, Thomas, Alford, Matthew H., Barton, Benjamin I., Boury, Samuel, Brenner, Samuel D., Couto, Nicole, Danielson, Seth L., Fine, Elizabeth C., Graber, Hans C., Guthrie, John, Hopkins, Joanne E., Jayne, Steven R., Jeon, Chanhyung, Klenz, Thilo, Lee, Craig M., Lenn, Yueng-Djern, Lucas, Andrew J., Lund, Björn, Mahaffey, Claire, Norman, Louisa, Rainville, Luc, Smith, Madison M., Thomas, Leif N., Torres-Valdés, Sinhué, and Wood, Kevin R.
- Published
- 2021
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19. Extent of impact of deep-sea nodule mining midwater plumes is influenced by sediment loading, turbulence and thresholds
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Muñoz-Royo, Carlos, Peacock, Thomas, Alford, Matthew H., Smith, Jerome A., Le Boyer, Arnaud, Kulkarni, Chinmay S., Lermusiaux, Pierre F. J., Haley, Jr., Patrick J., Mirabito, Chris, Wang, Dayang, Adams, E. Eric, Ouillon, Raphael, Breugem, Alexander, Decrop, Boudewijn, Lanckriet, Thijs, Supekar, Rohit B., Rzeznik, Andrew J., Gartman, Amy, and Ju, Se-Jong
- Published
- 2021
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20. Observations of Tidally Driven Turbulence over Steep, Small-Scale Topography Embedded in the Tasman Slope.
- Author
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Marques, Olavo B., Alford, Matthew H., Pinkel, Robert, MacKinnon, Jennifer A., Voet, Gunnar, Klymak, Jody M., and Nash, Jonathan D.
- Subjects
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INTERNAL waves , *TURBULENCE , *MERIDIONAL overturning circulation , *TURBULENT mixing , *MOUNTAIN wave , *CONTINENTAL slopes - Abstract
Enhanced diapycnal mixing induced by the near-bottom breaking of internal waves is an essential component of the lower meridional overturning circulation. Despite its crucial role in the ocean circulation, tidally driven internal wave breaking is challenging to observe due to its inherently short spatial and temporal scales. We present detailed moored and shipboard observations that resolve the spatiotemporal variability of the tidal response over a small-scale bump embedded in the continental slope of Tasmania. Cross-shore tidal currents drive a nonlinear trapped response over the steep bottom around the bump. The observations are roughly consistent with two-dimensional high-mode tidal lee-wave theory. However, the alongshore tidal velocities are large, suggesting that the alongshore bathymetric variability modulates the tidal response driven by the cross-shore tidal flow. The semidiurnal tide and energy dissipation rate are correlated at subtidal time scales, but with complex temporal variability. Energy dissipation from a simple scattering model shows that the elevated near-bottom turbulence can be sustained by the impinging mode-1 internal tide, where the dissipation over the bump is O(1%) of the incident depth-integrated energy flux. Despite this small fraction, tidal dissipation is enhanced over the bump due to steep topography at a horizontal scale of O(1) km and may locally drive significant diapycnal mixing. Significance Statement: Near-bottom turbulent mixing is a key element of the global abyssal circulation. We present observations of the spatiotemporal variability of tidally driven turbulent processes over a small-scale topographic bump off Tasmania. The semidiurnal tide generates large-amplitude transient lee waves and hydraulic jumps that are unstable and dissipate the tidal energy. These processes are consistent with the scattering of the incident low-mode internal tide on the continental slope of Tasmania. Despite elevated turbulence over the bump, near-bottom energy dissipation is small relative to the incident wave energy flux. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
21. Observations of tidally driven turbulence over steep, small-scale topography embedded in the Tasman slope
- Author
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Marques, Olavo B., primary, Alford, Matthew H., additional, Pinkel, Robert, additional, MacKinnon, Jennifer A., additional, Voet, Gunnar, additional, Klymak, Jody M., additional, and Nash, Jonathan D., additional
- Published
- 2023
- Full Text
- View/download PDF
22. Numerical simulations of internal tide dynamics in a steep submarine canyon
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Masunaga, Eiji, primary, Alford, Matthew H., additional, Lucas, Andrew J., additional, and Rodriguez-Marin Freudmann, Andrea, additional
- Published
- 2023
- Full Text
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23. Observations and simulations of caustic formation due to oceanographic fine structure
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DeFilippis, Jacob P., primary, Cornuelle, Bruce D., additional, Lucas, Andrew J., additional, Hodgkiss, William S., additional, Lenain, Luc, additional, Kuperman, W. A., additional, and Alford, Matthew H., additional
- Published
- 2023
- Full Text
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24. Energy and Momentum of a Density-Driven Overflow in the Samoan Passage
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Voet, Gunnar, primary, Alford, Matthew H., additional, Cusack, Jesse M., additional, Pratt, Larry J., additional, Girton, James B., additional, Carter, Glenn S., additional, Klymak, Jody M., additional, Tan, Shuwen, additional, and Thurnherr, Andreas M., additional
- Published
- 2023
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25. A Vorticity‐Divergence View of Internal Wave Generation by a Fast‐Moving Tropical Cyclone: Insights From Super Typhoon Mangkhut
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Brizuela, Noel G., primary, Johnston, T. M. Shaun, additional, Alford, Matthew H., additional, Asselin, Olivier, additional, Rudnick, Daniel L., additional, Moum, James N., additional, Thompson, Elizabeth J., additional, Wang, Shuguang, additional, and Lee, Chia‐Ying, additional
- Published
- 2023
- Full Text
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26. Significance of Diapycnal Mixing Within the Atlantic Meridional Overturning Circulation
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Cimoli, Laura, primary, Mashayek, Ali, additional, Johnson, Helen L., additional, Marshall, David P., additional, Naveira Garabato, Alberto C., additional, Whalen, Caitlin B., additional, Vic, Clément, additional, de Lavergne, Casimir, additional, Alford, Matthew H., additional, MacKinnon, Jennifer A., additional, and Talley, Lynne D., additional
- Published
- 2023
- Full Text
- View/download PDF
27. Tidally Forced Turbulent Dissipation on a Three-Dimensional Fan in Luzon Strait
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Alford, Matthew H., primary, Nash, Jonathan D., additional, and Buijsman, Maarten, additional
- Published
- 2023
- Full Text
- View/download PDF
28. Near‐Surface Oceanic Kinetic Energy Distributions From Drifter Observations and Numerical Models
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Arbic, Brian K., primary, Elipot, Shane, additional, Brasch, Jonathan M., additional, Menemenlis, Dimitris, additional, Ponte, Aurélien L., additional, Shriver, Jay F., additional, Yu, Xiaolong, additional, Zaron, Edward D., additional, Alford, Matthew H., additional, Buijsman, Maarten C., additional, Abernathey, Ryan, additional, Garcia, Daniel, additional, Guan, Lingxiao, additional, Martin, Paige E., additional, and Nelson, Arin D., additional
- Published
- 2022
- Full Text
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29. Significance of diapycnal mixing within the Atlantic Meridional Overturning Circulation
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Cimoli, Laura, primary, Mashayek, Ali, additional, Johnson, Helen Louise, additional, Marshall, David P, additional, Naveira Garabato, Alberto C., additional, Whalen, Caitlin, additional, Vic, Clement, additional, de Lavergne, Casimir, additional, Alford, Matthew H, additional, MacKinnon, Jennifer A, additional, and Talley, Lynne D., additional
- Published
- 2022
- Full Text
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30. Impact of Vertical Mixing Parameterizations on Internal Gravity Wave Spectra in Regional Ocean Models
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Thakur, Ritabrata, primary, Arbic, Brian K., additional, Menemenlis, Dimitris, additional, Momeni, Kayhan, additional, Pan, Yulin, additional, Peltier, W. R., additional, Skitka, Joseph, additional, Alford, Matthew H., additional, and Ma, Yuchen, additional
- Published
- 2022
- Full Text
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31. Global Observations of Rotary-With-Depth Shear Spectra
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Waterhouse, Amy F., primary, Hennon, Tyler, additional, Kunze, Eric, additional, MacKinnon, Jennifer A., additional, Alford, Matthew H., additional, Pinkel, Robert, additional, Simmons, Harper, additional, Whalen, Caitlin B., additional, Fine, Elizabeth C., additional, Klymak, Jody, additional, and Hummon, Julia M., additional
- Published
- 2022
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32. Measurements of Turbulence Generated by Wake Eddies Near a Steep Headland
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Wynne‐Cattanach, Bethan L., primary, Alford, Matthew H., additional, MacKinnon, Jennifer A., additional, and Voet, Gunnar, additional
- Published
- 2022
- Full Text
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33. Prolonged thermocline warming by near-inertial internal waves in the wakes of tropical cyclones.
- Author
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Gutiérrez Brizuela, Noel, Alford, Matthew H., Shang-Ping Xie, Sprintall, Janet, Voet, Gunnar, Warner, Sally J., Hughes, Kenneth, and Moum, James N.
- Subjects
- *
INTERNAL waves , *TROPICAL cyclones , *OCEANIC mixing , *WATER masses , *EDDY flux , *PERMEATION tubes - Abstract
Turbulence-enhanced mixing of upper ocean heat allows interaction between the tropical atmosphere and cold water masses that impact climate at higher latitudes thereby regulating air-sea coupling and poleward heat transport. Tropical cyclones (TCs) can drastically enhance upper ocean mixing and generate powerful near-inertial internal waves (NIWs) that propagate down into the deep ocean. Globally, downward mixing of heat during TC passage causes warming in the seasonal thermocline and pumps 0.15 to 0.6 PW of heat into the unventilated ocean. The final distribution of excess heat contributed by TCs is needed to understand subsequent consequences for climate; however, it is not well constrained by current observations. Notably, whether or not excess heat supplied by TCs penetrates deep enough to be kept in the ocean beyond the winter season is a matter of debate. Here, we show that NIWs generated by TCs drive thermocline mixing weeks after TC passage and thus greatly deepen the extent of downward heat transfer induced by TCs. Microstructure measurements of the turbulent diffusivity (κ) and turbulent heat flux (Jq) in the Western Pacific before and after the passage of three TCs indicate that mean thermocline values of κ and Jq increased by factors of 2 to 7 and 2 to 4 (95% confidence level), respectively, after TC passage. Excess mixing is shown to be associated with the vertical shear of NIWs, demonstrating that studies of TC-climate interactions ought to represent NIWs and their mixing to accurately capture TC effects on background ocean stratification and climate. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
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34. A vorticity-divergence view of internal wave generation by tropical cyclones: insights from Super Typhoon Mangkhut
- Author
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Brizuela, Noel G., primary, Johnston, T. M. Shaun, additional, Alford, Matthew H, additional, Asselin, Olivier, additional, Rudnick, Daniel L., additional, Moum, Jim, additional, Thompson, Elizabeth J, additional, Wang, Shuguang, additional, and Lee, Chia-Ying, additional
- Published
- 2022
- Full Text
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35. Hydraulic control of flow in a multi-passage system connecting two basins
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Tan, Shuwen, Pratt, Lawrence J., Voet, Gunnar, Cusack, Jesse M., Helfrich, Karl R., Alford, Matthew H., Girton, James B., Carter, Glenn S., Tan, Shuwen, Pratt, Lawrence J., Voet, Gunnar, Cusack, Jesse M., Helfrich, Karl R., Alford, Matthew H., Girton, James B., and Carter, Glenn S.
- Abstract
© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Tan, S., Pratt, L. J., Voet, G., Cusack, J. M., Helfrich, K. R., Alford, M. H., Girton, J. B., & Carter, G. S. Hydraulic control of flow in a multi-passage system connecting two basins. Journal of Fluid Mechanics, 940, (2022): A8, https://doi.org/10.1017/jfm.2022.212., When a fluid stream in a conduit splits in order to pass around an obstruction, it is possible that one branch will be critically controlled while the other remains not so. This is apparently the situation in Pacific Ocean abyssal circulation, where most of the northward flow of Antarctic bottom water passes through the Samoan Passage, where it is hydraulically controlled, while the remainder is diverted around the Manihiki Plateau and is not controlled. These observations raise a number of questions concerning the dynamics necessary to support such a regime in the steady state, the nature of upstream influence and the usefulness of rotating hydraulic theory to predict the partitioning of volume transport between the two paths, which assumes the controlled branch is inviscid. Through the use of a theory for constant potential vorticity flow and accompanying numerical model, we show that a steady-state regime similar to what is observed is dynamically possible provided that sufficient bottom friction is present in the uncontrolled branch. In this case, the upstream influence that typically exists for rotating channel flow is transformed into influence into how the flow is partitioned. As a result, the partitioning of volume flux can still be reasonably well predicted with an inviscid theory that exploits the lack of upstream influence., This work was supported by the National Science Foundation under grants OCE-1029268, OCE-1029483, OCE-1657264, OCE-1657795, OCE-1657870 and OCE-1658027.
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- 2022
36. Near‐Surface Oceanic Kinetic Energy Distributions From Drifter Observations and Numerical Models
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Arbic, Brian K., Elipot, Shane, Brasch, Jonathan M., Menemenlis, Dimitris, Ponte, Aurelien, Shriver, Jay F., Yu, Xiaolong, Zaron, Edward D., Alford, Matthew H., Buijsman, Maarten C., Abernathey, Ryan, Garcia, Daniel, Guan, Lingxiao, Martin, Paige E., Nelson, Arin D., Arbic, Brian K., Elipot, Shane, Brasch, Jonathan M., Menemenlis, Dimitris, Ponte, Aurelien, Shriver, Jay F., Yu, Xiaolong, Zaron, Edward D., Alford, Matthew H., Buijsman, Maarten C., Abernathey, Ryan, Garcia, Daniel, Guan, Lingxiao, Martin, Paige E., and Nelson, Arin D.
- Abstract
The geographical variability, frequency content, and vertical structure of near-surface oceanic kinetic energy (KE) are important for air-sea interaction, marine ecosystems, operational oceanography, pollutant tracking, and interpreting remotely sensed velocity measurements. Here, KE in high-resolution global simulations (HYbrid Coordinate Ocean Model; HYCOM, and Massachusetts Institute of Technology general circulation model; MITgcm), at the sea surface (0 m) and at 15 m, are compared with KE from undrogued and drogued surface drifters, respectively. Global maps and zonal averages are computed for low-frequency (<0.5 cpd), near-inertial, diurnal, and semidiurnal bands. Both models exhibit low-frequency equatorial KE that is low relative to drifter values. HYCOM near-inertial KE is higher than in MITgcm, and closer to drifter values, probably due to more frequently updated atmospheric forcing. HYCOM semidiurnal KE is lower than in MITgcm, and closer to drifter values, likely due to inclusion of a parameterized topographic internal wave drag. A concurrent tidal harmonic analysis in the diurnal band demonstrates that much of the diurnal flow is nontidal. We compute simple proxies of near-surface vertical structure—the ratio 0 m KE/(0 m KE + 15 m KE) in model outputs, and the ratio undrogued KE/(undrogued KE + drogued KE) in drifter observations. Over most latitudes and frequency bands, model ratios track the drifter ratios to within error bars. Values of this ratio demonstrate significant vertical structure in all frequency bands except the semidiurnal band. Latitudinal dependence in the ratio is greatest in diurnal and low-frequency bands. Key Points We examine frequency content of ocean kinetic energy (KE) at the sea surface (0 m) and 15 m depth with global drifter data and two models Near-surface near-inertial and tidal KE in numerical models are sensitive to atmospheric forcing frequency and damping The ratio 0 m KE/(0 m KE + 15 m KE) in models lies within error b
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- 2022
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37. A warm jet in a cold ocean
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MacKinnon, Jennifer A, Simmons, Harper L, Hargrove, John, Thomson, Jim, Peacock, Thomas, Alford, Matthew H, Barton, Benjamin I, Boury, Samuel, Brenner, Samuel D, Couto, Nicole, Danielson, Seth L, Fine, Elizabeth C, Graber, Hans C, Guthrie, John, Hopkins, Joanne E, Jayne, Steven R, Jeon, Chanhyung, Klenz, Thilo, Lee, Craig M, Lenn, Yueng-Djern, Lucas, Andrew J, Lund, Björn, Mahaffey, Claire, Norman, Louisa, Rainville, Luc, Smith, Madison M, Thomas, Leif N, Torres-Valdés, Sinhué, Wood, Kevin R, MacKinnon, Jennifer A, Simmons, Harper L, Hargrove, John, Thomson, Jim, Peacock, Thomas, Alford, Matthew H, Barton, Benjamin I, Boury, Samuel, Brenner, Samuel D, Couto, Nicole, Danielson, Seth L, Fine, Elizabeth C, Graber, Hans C, Guthrie, John, Hopkins, Joanne E, Jayne, Steven R, Jeon, Chanhyung, Klenz, Thilo, Lee, Craig M, Lenn, Yueng-Djern, Lucas, Andrew J, Lund, Björn, Mahaffey, Claire, Norman, Louisa, Rainville, Luc, Smith, Madison M, Thomas, Leif N, Torres-Valdés, Sinhué, and Wood, Kevin R
- Abstract
Unprecedented quantities of heat are entering the Pacific sector of the Arctic Ocean through Bering Strait, particularly during summer months. Though some heat is lost to the atmosphere during autumn cooling, a significant fraction of the incoming warm, salty water subducts (dives beneath) below a cooler fresher layer of near-surface water, subsequently extending hundreds of kilometers into the Beaufort Gyre. Upward turbulent mixing of these sub-surface pockets of heat is likely accelerating sea ice melt in the region. This Pacific-origin water brings both heat and unique biogeochemical properties, contributing to a changing Arctic ecosystem. However, our ability to understand or forecast the role of this incoming water mass has been hampered by lack of understanding of the physical processes controlling subduction and evolution of this this warm water. Crucially, the processes seen here occur at small horizontal scales not resolved by regional forecast models or climate simulations; new parameterizations must be developed that accurately represent the physics. Here we present novel high resolution observations showing the detailed process of subduction and initial evolution of warm Pacific-origin water in the southern Beaufort Gyre.
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- 2022
38. Extent of impact of deep-sea nodule mining midwater plumes is influenced by sediment loading, turbulence and thresholds
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Muñoz-Royo, Carlos, Peacock, Thomas, Alford, Matthew H, Smith, Jerome A, Le Boyer, Arnaud, Kulkarni, Chinmay S, Lermusiaux, Pierre FJ, Haley, Patrick J, Mirabito, Chris, Wang, Dayang, Adams, E Eric, Ouillon, Raphael, Breugem, Alexander, Decrop, Boudewijn, Lanckriet, Thijs, Supekar, Rohit B, Rzeznik, Andrew J, Gartman, Amy, Ju, Se-Jong, Muñoz-Royo, Carlos, Peacock, Thomas, Alford, Matthew H, Smith, Jerome A, Le Boyer, Arnaud, Kulkarni, Chinmay S, Lermusiaux, Pierre FJ, Haley, Patrick J, Mirabito, Chris, Wang, Dayang, Adams, E Eric, Ouillon, Raphael, Breugem, Alexander, Decrop, Boudewijn, Lanckriet, Thijs, Supekar, Rohit B, Rzeznik, Andrew J, Gartman, Amy, and Ju, Se-Jong
- Abstract
Deep-sea polymetallic nodule mining research activity has substantially increased in recent years, but the expected level of environmental impact is still being established. One environmental concern is the discharge of a sediment plume into the midwater column. We performed a dedicated field study using sediment from the Clarion Clipperton Fracture Zone. The plume was monitored and tracked using both established and novel instrumentation, including acoustic and turbulence measurements. Our field studies reveal that modeling can reliably predict the properties of a midwater plume in the vicinity of the discharge and that sediment aggregation effects are not significant. The plume model is used to drive a numerical simulation of a commercial-scale operation in the Clarion Clipperton Fracture Zone. Key takeaways are that the scale of impact of the plume is notably influenced by the values of environmentally acceptable threshold levels, the quantity of discharged sediment, and the turbulent diffusivity in the Clarion Clipperton Fracture Zone.
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- 2022
39. Extent of impact of deep-sea nodule mining midwater plumes is influenced by sediment loading, turbulence and thresholds
- Author
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Massachusetts Institute of Technology. Department of Mechanical Engineering, Massachusetts Institute of Technology. Department of Civil and Environmental Engineering, Muñoz-Royo, Carlos, Peacock, Thomas, Alford, Matthew H., Smith, Jerome A., Le Boyer, Arnaud, Kulkarni, Chinmay S., Lermusiaux, Pierre F. J., Haley, Patrick J., Mirabito, Chris, Wang, Dayang, Adams, E. Eric, Ouillon, Raphael, Breugem, Alexander, Decrop, Boudewijn, Lanckriet, Thijs, Supekar, Rohit B., Rzeznik, Andrew J., Gartman, Amy, Ju, Se-Jong, Massachusetts Institute of Technology. Department of Mechanical Engineering, Massachusetts Institute of Technology. Department of Civil and Environmental Engineering, Muñoz-Royo, Carlos, Peacock, Thomas, Alford, Matthew H., Smith, Jerome A., Le Boyer, Arnaud, Kulkarni, Chinmay S., Lermusiaux, Pierre F. J., Haley, Patrick J., Mirabito, Chris, Wang, Dayang, Adams, E. Eric, Ouillon, Raphael, Breugem, Alexander, Decrop, Boudewijn, Lanckriet, Thijs, Supekar, Rohit B., Rzeznik, Andrew J., Gartman, Amy, and Ju, Se-Jong
- Abstract
Deep-sea polymetallic nodule mining research activity has substantially increased in recent years, but the expected level of environmental impact is still being established. One environmental concern is the discharge of a sediment plume into the midwater column. We performed a dedicated field study using sediment from the Clarion Clipperton Fracture Zone. The plume was monitored and tracked using both established and novel instrumentation, including acoustic and turbulence measurements. Our field studies reveal that modeling can reliably predict the properties of a midwater plume in the vicinity of the discharge and that sediment aggregation effects are not significant. The plume model is used to drive a numerical simulation of a commercial-scale operation in the Clarion Clipperton Fracture Zone. Key takeaways are that the scale of impact of the plume is notably influenced by the values of environmentally acceptable threshold levels, the quantity of discharged sediment, and the turbulent diffusivity in the Clarion Clipperton Fracture Zone.
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- 2022
40. A warm jet in a cold ocean
- Author
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MacKinnon, Jennifer A., Simmons, Harper L., Hargrove, John, Thomson, Jim, Peacock, Thomas, Alford, Matthew H., Barton, Benjamin I., Boury, Samuel, Brenner, Samuel D., Couto, Nicole, Danielson, Seth L., Fine, Elizabeth C., Graber, Hans C., Guthrie, John, Hopkins, Joanne E., Jayne, Steven R., Jeon, Chanhyung, Klenz, Thilo, Lee, Craig M., Lenn, Yueng-Djern, Lucas, Andrew J., Lund, Björn, Mahaffey, Claire, Norman, Louisa, Rainville, Luc, Smith, Madison M., Thomas, Leif N., Torres-Valdés, Sinhué, Wood, Kevin R., MacKinnon, Jennifer A., Simmons, Harper L., Hargrove, John, Thomson, Jim, Peacock, Thomas, Alford, Matthew H., Barton, Benjamin I., Boury, Samuel, Brenner, Samuel D., Couto, Nicole, Danielson, Seth L., Fine, Elizabeth C., Graber, Hans C., Guthrie, John, Hopkins, Joanne E., Jayne, Steven R., Jeon, Chanhyung, Klenz, Thilo, Lee, Craig M., Lenn, Yueng-Djern, Lucas, Andrew J., Lund, Björn, Mahaffey, Claire, Norman, Louisa, Rainville, Luc, Smith, Madison M., Thomas, Leif N., Torres-Valdés, Sinhué, and Wood, Kevin R.
- Abstract
Unprecedented quantities of heat are entering the Pacific sector of the Arctic Ocean through Bering Strait, particularly during summer months. Though some heat is lost to the atmosphere during autumn cooling, a significant fraction of the incoming warm, salty water subducts (dives beneath) below a cooler fresher layer of near-surface water, subsequently extending hundreds of kilometers into the Beaufort Gyre. Upward turbulent mixing of these sub-surface pockets of heat is likely accelerating sea ice melt in the region. This Pacific-origin water brings both heat and unique biogeochemical properties, contributing to a changing Arctic ecosystem. However, our ability to understand or forecast the role of this incoming water mass has been hampered by lack of understanding of the physical processes controlling subduction and evolution of this this warm water. Crucially, the processes seen here occur at small horizontal scales not resolved by regional forecast models or climate simulations; new parameterizations must be developed that accurately represent the physics. Here we present novel high resolution observations showing the detailed process of subduction and initial evolution of warm Pacific-origin water in the southern Beaufort Gyre.
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- 2022
41. Double Diffusion, Shear Instabilities, and Heat Impacts of a Pacific Summer Water Intrusion in the Beaufort Sea
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Fine, Elizabeth C., primary, MacKinnon, Jennifer A., additional, Alford, Matthew H., additional, Middleton, Leo, additional, Taylor, John, additional, Mickett, John B., additional, Cole, Sylvia T., additional, Couto, Nicole, additional, Boyer, Arnaud Le, additional, and Peacock, Thomas, additional
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- 2022
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- View/download PDF
42. Advection–diffusion settling of deep-sea mining sediment plumes. Part 2. Collector plumes
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Ouillon, Raphael, primary, Muñoz-Royo, Carlos, additional, Alford, Matthew H., additional, and Peacock, Thomas, additional
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- 2022
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- View/download PDF
43. Advection-diffusion-settling of deep-sea mining sediment plumes. Part 1: Midwater plumes
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Ouillon, Raphael, primary, Muñoz-Royo, Carlos, additional, Alford, Matthew H., additional, and Peacock, Thomas, additional
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- 2022
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- View/download PDF
44. Oceanic turbulence from a planktonic perspective
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Franks, Peter J. S., primary, Inman, Bryce G., additional, MacKinnon, Jennifer A., additional, Alford, Matthew H., additional, and Waterhouse, Amy F., additional
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- 2021
- Full Text
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45. Data‐Driven Identification of Turbulent Oceanic Mixing From Observational Microstructure Data
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Couchman, Miles M. P., primary, Wynne‐Cattanach, Bethan, additional, Alford, Matthew H., additional, Caulfield, Colm‐cille P., additional, Kerswell, Rich R., additional, MacKinnon, Jennifer A., additional, and Voet, Gunnar, additional
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- 2021
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46. Interacting internal waves explain global patterns of interior ocean mixing.
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Dematteis G, Le Boyer A, Pollmann F, Polzin KL, Alford MH, Whalen CB, and Lvov YV
- Abstract
Across the stable density stratification of the abyssal ocean, deep dense water is slowly propelled upward by sustained, though irregular, turbulent mixing. The resulting mean upwelling determines large-scale oceanic circulation properties like heat and carbon transport. In the ocean interior, this turbulent mixing is caused mainly by breaking internal waves: generated predominantly by winds and tides, these waves interact nonlinearly, transferring energy downscale, and finally become unstable, break and mix the water column. This paradigm, long parameterized heuristically, still lacks full theoretical explanation. Here, we close this gap using wave-wave interaction theory with input from both localized and global observations. We find near-ubiquitous agreement between first-principle predictions and observed mixing patterns in the global ocean interior. Our findings lay the foundations for a wave-driven mixing parameterization for ocean general circulation models that is entirely physics-based, which is key to reliably represent future climate states that could differ substantially from today's., (© 2024. The Author(s).)
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- 2024
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