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Frederick T. Mayer and Oliver B. Fringer

1. Introduction In the ocean, because lee waves occur on length scales smaller than the resolution of global circulation models (GCMs), the lee wave drag must be parameterized. Existing parameterizations are based on steady-state solutions for the flow above “linear-height” hills, wherein the height of the hill is much smaller than the wavelength of the wave ( Bell 1975b ; Gill 1982 ). Most common among the unresolved bathymetric features of the deep ocean are the abyssal hills which are

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Hui Wu

1. Introduction General circulation in the open ocean is constrained to the upper layer and thus hardly feels the abyssal topography, and the pressure anomaly away from the equator propagates westward due to Earth’s curvature, i.e., the planetary β effect. On reaching the shelf, the steep topography serves as a waveguide and deflects the oceanic information equatorward, i.e., the topographic Rossby wave, before it reaches the coastal region. In this case, the bathymetric slope, i.e., the

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Madeleine M. Hamann, Matthew H. Alford, Andrew J. Lucas, Amy F. Waterhouse, and Gunnar Voet

. Studies of internal wave reflection in canyons are limited, but studies of reflection from steep continental slopes show that incident mode-1 waves are accompanied by back reflection and scattering to modes 2 and higher. Globally, mode-1 internal tides encountering the continental slope transmit 20% of their energy onto the shelf, while 40% scatters to higher modes and 40% reflects back to the ocean interior ( Kelly et al. 2013 ). Locally, these percentages vary depending on stratification and the

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Shuwen Tan, Larry J. Pratt, Dongliang Yuan, Xiang Li, Zheng Wang, Yao Li, Corry Corvianawatie, Dewi Surinati, Asep S. Budiman, and Ahmad Bayhaqi

-to-supercritical transition of a hydraulic flow, which implies blockage of certain types of internal waves from propagating upstream. So far, a quantitative evaluation of the flow hydraulics, which is important for understanding the communication of the Indian Ocean with the Pacific Ocean through the Lifamatola Passage, has not been conducted. Fig . 2. Conservative Temperature (Θ) section along the thalweg of the Lifamatola Passage. Flow is to the right, and the locations of numbered CTD stations can be found in Fig. 1b

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Jody M. Klymak, Dhruv Balwada, Alberto Naveira Garabato, and Ryan Abernathey

1. Introduction Stratified flows passing over bathymetry experience drags that are often many orders of magnitude larger than that effected by skin friction alone, due to the creation of internal motions that either radiate away as internal waves ( Bell 1975 ) or are trapped as “nonpropagating” motions near the topography (e.g., Bacmeister and Pierrehumbert 1988 ). These motions are important to large-scale momentum, energy, and mixing in both the ocean and the atmosphere, yet often must be

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Magdalena Andres, Ruth C. Musgrave, Daniel L. Rudnick, Kristin L. Zeiden, Thomas Peacock, and Jae-Hun Park

1. Introduction Oceanic processes that have an expression in sea surface height (SSH) occur over a range of time scales. Since the early 1990s satellite altimetry has been used to examine SSH variability related to processes at intraseasonal periods such as mesoscale eddy motions ( Chelton et al. 2011 ) or baroclinic Rossby wave propagations ( Qiu and Chen 2005 ) and at longer periods, including studies of regional and global sea level rise ( Church and White 2011 ). Some higher

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YUE BAI, YAN WANG, and ANDREW L. STEWART

Abstract

Topographic form stress (TFS) plays a central role in constraining the transport of the Antarctic Circumpolar Current (ACC), and thus the rate of exchange between the major ocean basins. Topographic form stress generation in the ACC has been linked to the formation of standing Rossby waves, which occur because the current is retrograde (opposing the direction of Rossby wave propagation). However, it is unclear whether TFS similarly retards current systems that are prograde (in the direction of Rossby wave propagation), which cannot arrest Rossby waves. An isopycnal model is used to investigate the momentum balance of wind-driven prograde and retrograde flows in a zonal channel, with bathymetry consisting of either a single ridge or a continental shelf and slope with a meridional excursion. Consistent with previous studies, retrograde flows are almost entirely impeded by TFS, except in the limit of flat bathymetry, whereas prograde flows are typically impeded by a combination of TFS and bottom friction. A barotropic theory for standing waves shows that bottom friction serves to shift the phase of the standing wave’s pressure field from that of the bathymetry, which is necessary to produce TFS. The mechanism is the same in prograde and retrograde flows, but is most efficient when the mean flow arrests a Rossby wave with a wavelength comparable to that of the bathymetry. The asymmetry between prograde and retrograde momentum balances implies that prograde current systems may be more sensitive to changes in wind forcing, for example associated with climate shifts.

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Hemantha W. Wijesekera, Joel C. Wesson, David W. Wang, William J. Teague, and Z. R. Hallock

1. Introduction Flow interactions over space and time with abrupt topography, such as with small-scale islands and deep ocean ridges, can significantly impact regional to large-scale ocean circulation through intense turbulent mixing, formation of mesoscale wakes and eddy shedding behind islands, submesoscale upwelling and downwelling, and generation of lee internal waves ( Baines 1995 ). Along with ocean variability due to topographic features, islands and atolls also modify the atmospheric

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Kristin L. Zeiden, Jennifer A. MacKinnon, Matthew H. Alford, Daniel L. Rudnick, Gunnar Voet, and Hemantha Wijesekera

more to the irregularity in surface tidal KE. In another FLEAT study, Voet et al. (2020) observe the formation of lee waves from a combination of subinertial and tidal flows over the ridge north of Velasco. However, their observations suggest it is unlikely these waves contribute appreciably to upper-ocean velocity. In an earlier study of Palau, Wolanski et al. (2004) observed isotherm shoaling at tidal periods. These internal tides were synchronous the local spring–neap cycle, suggesting they

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Andrew L. Stewart, James C. McWilliams, and Aviv Solodoch

.1175/1520-0469(1986)043<3226:GSDAPV>2.0.CO;2 Rhines , P. B. , 1986 : Vorticity dynamics of the oceanic general circulation . Annu. Rev. Fluid Mech. , 18 , 433 – 497 , https://doi.org/10.1146/annurev.fl.18.010186.002245 . 10.1146/annurev.fl.18.010186.002245 Rhines , P. B. , and F. Bretherton , 1973 : Topographic Rossby waves in a rough-bottomed ocean . J. Fluid Mech. , 61 , 583 – 607 , https://doi.org/10.1017/S002211207300087X . 10.1017/S002211207300087X Salmon , R. , 1994 : Generalized two-layer models of

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