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Your search keyword '"Alford, Matthew H."' showing total 179 results
Start Over Author "Alford, Matthew H." Publisher american meteorological society
179 results on '"Alford, Matthew H."'

3. Observations of Tidally Driven Turbulence over Steep, Small-Scale Topography Embedded in the Tasman Slope.

Author

Marques, Olavo B., Alford, Matthew H., Pinkel, Robert, MacKinnon, Jennifer A., Voet, Gunnar, Klymak, Jody M., and Nash, Jonathan D.

Subjects
*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
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6. CLIMATE PROCESS TEAM ON INTERNAL WAVE-DRIVEN OCEAN MIXING: The study summarizes recent advances in our understanding of internal wave-driven turbulent mixing in the ocean interior and introduces new parameterizations for global climate ocean models and their climate impacts

Author

MacKinnon, Jennifer A., Zhao, Zhongxiang, Whalen, Caitlin B., Waterhouse, Amy F., Trossman, David S., Sun, Oliver M., Laurent, Louis C. St., Simmons, Harper L., Polzin, Kurt, Pinkel, Robert, Pickering, Andrew, Norton, Nancy J., Nash, Jonathan D., Musgrave, Ruth, Merchant, Lynne M., Melet, Angelique V., Mater, Benjamin, Legg, Sonya, Large, William G., Kunze, Eric, Klymak, Jody M., Jochum, Markus, Jayne, Steven R., Hallberg, Robert W., Griffies, Stephen M., Diggs, Steve, Danabasoglu, Gokhan, Chassignet, Eric P., Buijsman, Maarten C., Bryan, Frank O., Briegleb, Bruce P., Barna, Andrew, Arbic, Brian K., Ansong, Joseph K., and Alford, Matthew H.

Subjects
Weather forecasting -- Methods, Ocean circulation -- Observations, Business, Earth sciences
Abstract

Diapycnal mixing plays a primary role in the thermodynamic balance of the ocean and, consequently, in oceanic heat and carbon uptake and storage. Though observed mixing rates are on average [...]

Published
2017
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8. Global Observations of Rotary-With-Depth Shear Spectra

Author

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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21. Persistent Turbulence in the Samoan Passage

Author

Cusack, Jesse M., primary, Voet, Gunnar, additional, Alford, Matthew H., additional, Girton, James B., additional, Carter, Glenn S., additional, Pratt, Larry J., additional, Pearson-Potts, Kelly A., additional, and Tan, Shuwen, additional

Published
2019
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34. Satellite Investigation of the M2 Internal Tide in the Tasman Sea.

Author

Zhao, Zhongxiang, Alford, Matthew H., Simmons, Harper L., Brazhnikov, Dmitry, and Pinkel, Rob

Subjects
*ALTIMETRY, *STRATIGRAPHIC geology, *WATER currents, *MESOSCALE eddies, *FLUX (Energy), *THEORY of wave motion
Abstract

The M2 internal tide in the Tasman Sea is investigated using sea surface height measurements made by multiple altimeter missions from 1992 to 2012. Internal tidal waves are extracted by two-dimensional plane wave fits in 180 km by 180 km windows. The results show that the Macquarie Ridge radiates three internal tidal beams into the Tasman Sea. The northern and southern beams propagate respectively into the East Australian Current and the Antarctic Circumpolar Current and become undetectable to satellite altimetry. The central beam propagates across the Tasman Sea, impinges on the Tasmanian continental slope, and partially reflects. The observed propagation speeds agree well with theoretical values determined from climatological ocean stratification. Both the northern and central beams refract about 15° toward the equator because of the beta effect. Following a concave submarine ridge in the source region, the central beam first converges around 45.5°S, 155.5°E and then diverges beyond the focal region. The satellite results reveal two reflected internal tidal beams off the Tasmanian slope, consistent with previous numerical simulations and glider measurements. The total energy flux from the Macquarie Ridge into the Tasman Sea is about 2.2 GW, of which about half is contributed by the central beam. The central beam loses little energy in its first 1000-km propagation, for which the likely reasons include flat bottom topography and weak mesoscale eddies. [ABSTRACT FROM AUTHOR]

Published
2018
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37. Global Patterns of Diapycnal Mixing from Measurements of the Turbulent Dissipation Rate

Author

Waterhouse, Amy F., primary, MacKinnon, Jennifer A., primary, Nash, Jonathan D., primary, Alford, Matthew H., primary, Kunze, Eric, primary, Simmons, Harper L., primary, Polzin, Kurt L., primary, St. Laurent, Louis C., primary, Sun, Oliver M., primary, Pinkel, Robert, primary, Talley, Lynne D., primary, Whalen, Caitlin B., primary, Huussen, Tycho N., primary, Carter, Glenn S., primary, Fer, Ilker, primary, Waterman, Stephanie, primary, Naveira Garabato, Alberto C., primary, Sanford, Thomas B., primary, and Lee, Craig M., primary

Published
2014
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40. The Impact of Oceanic Near-Inertial Waves on Climate

Author

Jochum, Markus, primary, Briegleb, Bruce P., additional, Danabasoglu, Gokhan, additional, Large, William G., additional, Norton, Nancy J., additional, Jayne, Steven R., additional, Alford, Matthew H., additional, and Bryan, Frank O., additional

Published
2013
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42. Global Observations of Open-Ocean Mode-1 M2 Internal Tides.

Author

Zhao, Zhongxiang, Alford, Matthew H., Girton, James B., Rainville, Luc, and Simmons, Harper L.

Subjects
*TIDES, *OCEAN circulation, *INTERNAL waves, *SEAMOUNTS, *FLUX flow
Abstract

A global map of open-ocean mode-1 M2 internal tides is constructed using sea surface height (SSH) measurements from multiple satellite altimeters during 1992-2012, representing a 20-yr coherent internal tide field. A two-dimensional plane wave fit method is employed to 1) suppress mesoscale contamination by extracting internal tides with both spatial and temporal coherence and 2) separately resolve multiple internal tidal waves. Global maps of amplitude, phase, energy, and flux of mode-1 M2 internal tides are presented. The M2 internal tides are mainly generated over topographic features, including continental slopes, midocean ridges, and seamounts. Internal tidal beams of 100-300 km width are observed to propagate hundreds to thousands of kilometers. Multiwave interference of some degree is widespread because of the M2 internal tide's numerous generation sites and long-range propagation. The M2 internal tide propagates across the critical latitudes for parametric subharmonic instability (28.8°S/N) with little energy loss, consistent with the 2006 Internal Waves across the Pacific (IWAP) field measurements. In the eastern Pacific Ocean, the M2 internal tide loses significant energy in propagating across the equator; in contrast, little energy loss is observed in the equatorial zones of the Atlantic, Indian, and western Pacific Oceans. Global integration of the satellite observations yields a total energy of 36 PJ (1 PJ = 1015 J) for all the coherent mode-1 M2 internal tides. Finally, satellite observed M2 internal tides compare favorably with field mooring measurements and a global eddy-resolving numerical model. [ABSTRACT FROM AUTHOR]

Published
2016
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47. Energy Flux and Dissipation in Luzon Strait: Two Tales of Two Ridges

Author

Alford, Matthew H., primary, MacKinnon, Jennifer A., primary, Nash, Jonathan D., primary, Simmons, Harper, primary, Pickering, Andy, primary, Klymak, Jody M., primary, Pinkel, Robert, primary, Sun, Oliver, primary, Rainville, Luc, primary, Musgrave, Ruth, primary, Beitzel, Tamara, primary, Fu, Ke-Hsien, primary, and Lu, Chung-Wei, primary

Published
2011
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