Physical Oceanography (PO)

Permanent URI for this collection

https://hdl.handle.net/1912/7

Department members investigate the dynamics and thermodynamics of ocean circulation. They work globally from the Arctic to the Antarctic and from the Strait of Gibraltar to the Philippine shelf on the full range of oceanic processes, from mixing on centimeter scales to heat balance on the global scale.

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Browsing Physical Oceanography (PO) by Author "Alford, Matthew H."
  • Article
    Energy and momentum of a density-driven overflow in the Samoan Passage
    (American Meteorological Society, 2023-06-01) Voet, Gunnar ; Alford, Matthew H. ; Cusack, Jesse M. ; Pratt, Larry J. ; Girton, James B. ; Carter, Glenn S. ; Klymak, Jody M. ; Tan, Shuwen ; Thurnherr, Andreas M.
    Abstract The energy and momentum balance of an abyssal overflow across a major sill in the Samoan Passage is estimated from two highly resolved towed sections, set 16 months apart, and results from a two-dimensional numerical simulation. Driven by the density anomaly across the sill, the flow is relatively steady. The system gains energy from divergence of horizontal pressure work and flux of available potential energy . Approximately half of these gains are transferred into kinetic energy while the other half is lost to turbulent dissipation, bottom drag, and divergence in vertical pressure work. Small-scale internal waves emanating downstream of the sill within the overflow layer radiate upward but dissipate most of their energy within the dense overflow layer and at its upper interface. The strongly sheared and highly stratified upper interface acts as a critical layer inhibiting any appreciable upward radiation of energy via topographically generated lee waves. Form drag of , estimated from the pressure drop across the sill, is consistent with energy lost to dissipation and internal wave fluxes. The topographic drag removes momentum from the mean flow, slowing it down and feeding a countercurrent aloft. The processes discussed in this study combine to convert about one-third of the energy released from the cross-sill density difference into turbulent mixing within the overflow and at its upper interface. The observed and modeled vertical momentum flux divergence sustains gradients in shear and stratification, thereby maintaining an efficient route for abyssal water mass transformation downstream of this Samoan Passage sill.
  • Article
    Observations of double diffusive staircase edges in the Arctic Ocean
    (American Geophysical Union, 2022-10-12) Boury, Samuel ; Supekar, Rohit ; Fine, Elizabeth C. ; Musgrave, Ruth C. ; Mickett, John B. ; Voet, Gunnar ; Odier, Philippe ; Peacock, Thomas ; MacKinnon, Jennifer A. ; Alford, Matthew H.
    Recent observational studies have provided detailed descriptions of double‐diffusive staircases in the Beaufort Sea, characterized by well‐mixed intrusions between high‐gradient interfaces. These structures result from double‐diffusive convection, occurring when cooler fresh water lies atop the warmer saltier Atlantic water layer. In the present study, we investigate the spatial structure of such layers, by analyzing combined high resolution data from a subsurface mooring, a ship‐towed profiling conductivity‐temperature‐depth/ADCP package, and a free‐falling microstructure profiler. At large scale, the modular microstructure profiler data suggest a horizontal “ragged edge” of the layered water masses near the basin boundary. At smaller scales, the mooring data indicate that, in the 300–400 m depth interval, regions of layers abruptly appear. This laterally sharp (of the order of 100 m) interface is advected southwards, as shown by the shallow water integrated mapping system survey conducted nearby. Neither disruption nor formation of layers is directly observed in our data, and we thus interpret our observations as the stable and possibly recent abutment of a layered and an unlayered water masses, now globally advected southwards by a large scale flow.