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| Siegelman, Lia; Klein, Patrice; Thompson, Andrew F.; Torres, Hector S.; Menemenlis, Dimitris. |
| Recent studies demonstrate that energetic sub-mesoscale fronts (10–50 km width) extend in the ocean interior, driving large vertical velocities and associated fluxes. However, diagnosing the dynamics of these deep-reaching fronts from in situ observations remains challenging because of the lack of information on the 3-D structure of the horizontal velocity. Here, a realistic numerical simulation in the Antarctic Circumpolar Current (ACC) is used to study the dynamics of submesocale fronts in relation to velocity gradients, responsible for the formation of these fronts. Results highlight that the stirring properties of the flow at depth, which are related to the velocity gradients, can be inferred from finite-size Lyapunov exponent (FSLE) at the surface.... |
| Tipo: Text |
Palavras-chave: Altimetry; Finite-size Lyapunov exponent; Ocean dynamics; Sub-mesoscale. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00645/75666/76532.pdf |
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| Siegelman, Lia; Roquet, Fabien; Mensah, Vigan; Riviere, Pascal; Pauthenet, Etienne; Picard, Baptiste; Guinet, Christophe. |
| Most available CTD Satellite Relay Data Logger (CTD-SRDL) profiles are heavily compressed before satellite transmission. High-resolution profiles recorded at the sampling frequency of 0.5 Hz are, however, available upon physical retrieval of the logger. Between 2014 and 2018, several loggers deployed on elephant seals in the Southern Ocean have been set in continuous recording mode, capturing both the ascent and descent for over 60 profiles per day during several months, opening new horizons for the physical oceanography community. Taking advantage of a new dataset made of seven such loggers, a postprocessing procedure is proposed and validated to improve the quality of all CTD-SRDL data: that is, both high-resolution profiles and compressed low-resolution... |
| Tipo: Text |
Palavras-chave: Algorithms; Data processing; In situ oceanic observations. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00494/60567/64043.pdf |
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| Siegelman, Lia; Klein, Patrice; Rivière, Pascal; Thompson, Andrew F.; Torres, Hector S.; Flexas, Mar; Menemenlis, Dimitris. |
| The ocean is the largest solar energy collector on Earth. The amount of heat it can store is modulated by its complex circulation, which spans a broad range of spatial scales, from metres to thousands of kilometres. In the classical paradigm, fine oceanic scales, less than 20 km in size, are thought to drive a significant downward heat transport from the surface to the ocean interior, which increases oceanic heat uptake. Here we use a combination of satellite and in situ observations in the Antarctic Circumpolar Current to diagnose oceanic vertical heat transport. The results explicitly demonstrate how deep-reaching submesoscale fronts, with a size smaller than 20 km, are generated by mesoscale eddies of size 50–300 km. In contrast to the classical... |
| Tipo: Text |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00594/70562/71323.pdf |
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| Su, Zhan; Torres, Hector; Klein, Patrice; Thompson, Andrew F; Siegelman, Lia; Wang, Jinbo; Menemenlis, Dimitris; Hill, Christopher. |
| he rate of ocean heat uptake depends on the mechanisms that transport heat between the surface and the ocean interior. A recent study found that the vertical heat transport driven by motions with scales smaller than 50 km (submesoscales) and frequencies smaller than one day‐1 is upward. This transport competes with the other major components of the global heat transport, namely the downward heat transport explained by the large‐scale wind‐driven vertical circulation and vertical diffusion at small scales, and the upward heat transport associated with mesoscale eddies (50‐300 km size). The contribution from motions with small spatial scales (< 50 km) and frequencies larger than one day‐1, including internal gravity waves, has never been explicitly... |
| Tipo: Text |
Palavras-chave: Ocean heat transport<; /AUTHOR_KEYWORD>; High frequency<; /AUTHOR_KEYWORD>; Ocean front<; /AUTHOR_KEYWORD>; Eddies<; /AUTHOR_KEYWORD>; Eddy transport<; /AUTHOR_KEYWORD>. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00643/75508/76354.pdf |
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| Klein, Patrice; Lapeyre, Guillaume; Siegelman, Lia; Qiu, Bo; Fu, Lee‐lueng; Torres, Hector; Su, Zhan; Menemenlis, Dimitris; Le Gentil, Sylvie. |
| Satellite observations of the last two decades have led to a major breakthrough emphasizing the existence of a strongly energetic mesoscale turbulent eddy field in all the oceans. This ocean mesoscale turbulence (OMT) is characterized by cyclonic and anticyclonic eddies (with a 100‐‐300 km size and depth scales of ~500‐‐1000 m) that capture approximatively 80% of the total kinetic energy and is now known to significantly impact the large‐scale ocean circulation, the ocean's carbon storage, the air‐sea interactions and therefore the Earth climate as a whole. However, OMT revealed by satellite observations has properties that differ from those related to classical geostrophic turbulence theories. In the last decade, a large number of theoretical and... |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00488/59951/63202.pdf |
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| Rivière, Pascal; Jaud, Thomas; Siegelman, Lia; Klein, Patrice; Cotté, Cedric; Le Sommer, Julien; Dencausse, Guillaume; Guinet, Christophe. |
| Sub‐mesoscale fronts—with scales from 1 to 50 km are ubiquitous in satellite images of the world oceans. They are known to generate strong vertical velocities with significant impacts on biogeochemical fluxes and pelagic ecosystems. Here, we use a unique data set, combining high‐resolution behavioral and physical measurements, to determine the effects of sub‐mesoscale structures on the foraging behavior of 12 instrumented female southern elephant seals. These marine mammals make long voyages (several months over more than 2000 km), diving and feeding continuously in the Antarctic Circumpolar Current. Our results show that elephant seals change their foraging behavior when crossing sub‐mesoscale fronts: They forage more and at shallower depths inside... |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00584/69636/67497.pdf |
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| Siegelman, Lia; O’toole, Malcolm; Flexas, Mar; Rivière, Pascal; Klein, Patrice. |
| The area west of the Kerguelen Islands (20–70°E/45–60°S) is characterized by a weak mesoscale activity except for a standing meander region of the Antarctic Circumpolar Current (ACC) localized between 20 and 40°E. A unique bio-physical dataset at high-resolution collected by a southern elephant seal (Mirounga leonina) reveals a conspicuous increase in foraging activity at the standing meander site up to 5 times larger than during the rest of her three-month trip west of the Kerguelen Islands. Here, we propose a physical explanation for such high biological activity based on the study of small-scale fronts with scales of 5 to 20 km, also called submesoscales. The standing meander is associated with intensified frontal dynamics at submesoscale, not observed... |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00489/60038/63305.pdf |
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