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| Klymak, Jody M.; Shearman, R. Kipp; Gula, Jonathan; Lee, Craig M.; D'Asaro, Eric A.; Thomas, Leif N.; Harcourt, Ramsey R.; Shcherbina, Andrey Y.; Sundermeyer, Miles A.; Molemaker, Jeroen; Mcwilliams, James C.. |
| The Gulf Stream is a major conduit of warm surface water from the tropics to the subpolar North Atlantic. Here we observe and simulate a submesoscale (<20km) mechanism by which the Gulf Stream exchanges water with subpolar water to the north. Along isopycnals, the front has a sharp compensated temperature-salinity contrast, with distinct mixed water between the two water masses 2 and 4km wide. This mixed water does not increase downstream despite substantial energy available for mixing. A series of streamers detrain this water at the crest of meanders. Subpolar water replaces the mixed water and resharpens the front. The water mass exchange accounts for a northward flux of salt of 0.5-2.5 psum(2)s(-1), (large-scale diffusivity O (100m(2)s(-1))). This is... |
| Tipo: Text |
Palavras-chave: Ocean mixing; Gulf Stream; Submesoscale mixing; Eddies. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00600/71201/69570.pdf |
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| Wenegrat, Jacob O.; Thomas, Leif N.; Gula, Jonathan; Mcwilliams, James C.. |
| Non-conservative processes change the potential vorticity (PV) of the upper ocean, and later, through the subduction of surface waters into the interior, affect the general ocean circulation. Here we focus on how boundary layer turbulence, in the presence of submesoscale horizontal buoyancy gradients, generates a source of potential vorticity at the ocean surface through a balance known as the Turbulent ThermalWind. This source of PV injection at the submesoscale can be of similar magnitude to PV fluxes from the wind and surface buoyancy fluxes, and hence can lead to a net injection of PV onto outcropped isopycnals even during periods of surface buoyancy loss. The significance of these dynamics is illustrated using a high-resolution realistic model of the... |
| Tipo: Text |
Palavras-chave: Ageostrophic circulations; Atmosphere-ocean interaction; Fronts; Ocean dynamics; Potential vorticity; Boundary layer. |
| Ano: 2018 |
URL: http://archimer.ifremer.fr/doc/00452/56347/57937.pdf |
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| Thomas, Leif N.; Shakespeare, Callum J.. |
| A simple analytical model is used to elucidate a potential mechanism for steady-state mode water formation at a thermohaline front that involves frontogenesis, submesoscale lateral mixing, and cabbeling. This mechanism is motivated in part by recent observations of an extremely sharp, density-compensated front at the North Wall of the Gulf Stream. Here, the intergyre, along-isopycnal, salinity-temperature difference is compressed into a span of a few kilometers, making the flow susceptible to cabbeling. The sharpness of the front is caused by frontogenetic strain, which is presumably balanced by submesoscale lateral mixing processes. The balance is studied with the simple model, and a scaling is derived for the amount of water mass transformation resulting... |
| Tipo: Text |
Palavras-chave: Circulation/ Dynamics; Frontogenesis/frontolysis; Fronts; Ocean dynamics; Atm/Ocean Structure/ Phenomena; Water masses. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00351/46243/46107.pdf |
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| Joyce, Terrence M.; Toole, John M.; Klein, Patrice; Thomas, Leif N.. |
| Layering of ocean velocity fine structure has been coherently observed across the entire extent of a Gulf Stream warm-core ring using a shipboard acoustic Doppler current profiler system in September 2009 and independently sampled as the ring transited a moored array. Lines of constant velocity phase generally followed isopycnals as they deepened within the ring center. We also observed a clear separation of the vertical structure of the flows associated with the ring (of order 0.5m/s) with the shorter (200m) and less energetic (similar to 0.2m/s) flows of the velocity fine structure, which was further observed to rotate clockwise with increasing depth, consistent with downward propagating near-inertial waves (NIWs). Observations are consistent with a... |
| Tipo: Text |
Palavras-chave: Near-inertial waves; Warm-core ring; Velocity fine structure. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00148/25929/23966.pdf |
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