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| Qiu, Bo; Chen, Shuiming; Klein, Patrice; Sasaki, Hideharu; Sasai, Yoshikazu. |
| Located at the center of the western North Pacific Subtropical Gyre, the Subtropical Countercurrent (STCC) is not only abundant in mesoscale eddies, but also exhibits prominent submesoscale eddy features. Output from a 1/30 degrees high-resolution OGCM simulation and a gridded satellite altimetry product are analyzed to contrast the seasonal STCC variability in the mesoscale versus submesoscale ranges. Resolving the eddy scales of >150 km, the altimetry product reveals that the STCC eddy kinetic energy and rms vorticity have a seasonal maximum in May and April, respectively, a weak positive vorticity skewness without seasonal dependence, and an inverse (forward) kinetic energy cascade for wavelengths larger (shorter) than 250 km. In contrast, the... |
| Tipo: Text |
Palavras-chave: Circulation/ Dynamics; Eddies; Instability; Mesoscale processes; Observational techniques and algorithms; Altimetry; Models and modeling; Ocean models; Variability; Seasonal variability. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00245/35588/34142.pdf |
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| Klein, Patrice; Hua, Bach-lien; Le Gentil, Sylvie; Fruman, Mark; Menesguen, Claire; Sasaki, Hideharu. |
| The big challenge of the next decade for the oceanic sciences is to adopt a multi-scale approach because of the strong nonlinearity of the oceanic fluid. This can be undertaken only through numerical simulations with ultra-high resolution. Within this context, the purpose of our project is to fully explore two energetic dynamical oceanic regimes that have a major impact on the general oceanic circulation: the mesoscale eddy regime at mid-latitudes and the equatorial regime. Results will help for the configuration of realistic numerical simulations to be performed in 2007-2008 by the OFES group on the Earth Simulator and also should benefit to future climate models. These studies make use of the Primitive Equations model ROMS (Regional Ocean Modelling... |
| Tipo: Text |
Palavras-chave: Mesoscale oceanic eddies; Equatorial dynamics. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/00067/17784/15307.pdf |
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| Sasaki, Hideharu; Klein, Patrice; Sasai, Yoshikazu; Qiu, Bo. |
| The kinetic energy (KE) seasonality has been revealed by satellite altimeters in many oceanic regions. Question about the mechanisms that trigger this seasonality is still challenging. We address this question through the comparison of two numerical simulations. The first one, with a 1/10° horizontal grid spacing, 54 vertical levels, represents dynamics of physical scales larger than 50 km. The second one, with a 1/30° grid spacing, 100 vertical levels, takes into account the dynamics of physical scales down to 16 km. Comparison clearly emphasizes in the whole North Pacific Ocean, not only a significant KE increase by a factor up to three, but also the emergence of seasonal variability when the scale range 16–50 km (called submesoscales in this study) is... |
| Tipo: Text |
Palavras-chave: Submesoscale turbulence; Scale interactions; Mixed-layer instability; High-resolution simulations; North Pacific. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00392/50347/51110.pdf |
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| Qiu, Bo; Chen, Shuiming; Klein, Patrice; Ubelmann, Clement; Fu, Lee-lueng; Sasaki, Hideharu. |
| Utilizing the framework of effective surface quasi-geostrophic (eSQG) theory, we explored the potential of reconstructing the 3D upper ocean circulation structures, including the balanced vertical velocity (w) field, from high-resolution sea surface height (SSH) data of the planned SWOT satellite mission. Specifically, we utilized the 1/30°, submesoscale-resolving, OFES model output and subjected it through the SWOT simulator that generates the along-swath SSH data with expected measurement errors. Focusing on the Kuroshio Extension region in the North Pacific where regional Rossby numbers range from 0.22 to 0.32, we found that the eSQG dynamics constitutes an effective framework for reconstructing the 3D upper ocean circulation field. Using the modeled... |
| Tipo: Text |
Palavras-chave: Variability; Models and modeling; General circulation models; Vertical motion; Circulation/ Dynamics; Quasigeostrophic models; Mesoscale processes; Observational techniques and algorithms; Oceanic variability; Altimetry. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00309/42032/41331.pdf |
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| Klein, Patrice; Hua, Bach-lien; Le Gentil, Sylvie; Sasaki, Hideharu. |
| The big challenge of the next decade for the oceanic sciences is to adopt a multi-scale approach because of the strong nonlinearity of the oceanic fluid. This can be undertaken only through numerical simulations with ultra-high resolution. Within this context, the purpose of our projects is to fully explore two energetic dynamical oceanic regimes that have a major impact on the general oceanic circulation: the mesoscale eddy regime at mid-latitudes and the equatorial regime. Expected results will help for the configuration of realistic numerical simulations to be performed in 2006 by the OFES group on the Earth Simulator and they should benefit to future climate models. These studies make use of the Primitive Equations model ROMS (Regional Ocean Modelling... |
| Tipo: Text |
Palavras-chave: Mesoscale oceanic eddies; Equatorial dynamics. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/00067/17783/15306.pdf |
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| Sasaki, Hideharu; Qiu, Bo; Klein, Patrice; Sasai, Yoshikazu; Nonaka, Masami. |
| The outputs from a submesoscale permitting hindcast simulation from 1990 to 2016 are used to investigate the interannual to decadal variations of submesoscale motions. The region we focus on is the subtropical Northwestern Pacific including the subtropical countercurrent. The submesoscale kinetic energy (KE) is characterized by strong interannual and decadal variability, displaying larger magnitudes in 1996, 2003, and 2015, and smaller magnitudes in 1999, 2009, 2010, and 2016. These variations are partially explained by those of the available potential energy (APE) release at submesoscale driven by mixed layer instability in winter. Indeed, this APE release depends on the mixed layer depth and horizontal buoyancy gradient, both of them modulated with the... |
| Tipo: Text |
Palavras-chave: Submesoscale motion; Interannual to decadal variations; Mixed layer instability; North Pacific Subtropical Countercurrent. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00641/75287/75641.pdf |
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| Klein, Patrice; Hua, Bach-lien; Le Gentil, Sylvie; Sasaki, Hideharu. |
| The purpose of this project is to study the dynamics of the upper oceanic layers (the first 1000m below the surface) and principally to get new insights on the effectiveness of the oceanic vertical pump at a basin scale through numerical experiments using ultra-high resolution. If the magnitude of this vertical pump when using such a resolution is much larger than anticipated, then the expected results should have an important impact on basin-scale SST and circulation through the vertical fluxes of heat and potential vorticity. Indeed preliminary studies already indicate the significant contribution of this eddy vertical pump to the modification of the surface layers heat content ([1], [2]). Thus the expected new results should be of importance for climate... |
| Tipo: Text |
Palavras-chave: Mesoscale oceanic eddies; Submesoscale dynamics; Vertical pump. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/00067/17782/15304.pdf |
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| Sasaki, Hideharu; Klein, Patrice; Qiu, Bo; Sasai, Yoshikazu. |
| Ocean eddies (with a size of 100-300 km), ubiquitous in satellite observations, are known to represent about 80% of the total ocean kinetic energy. Recent studies have pointed out the unexpected role of smaller oceanic structures (with 1-50 km scales) in generating and sustaining these eddies. The interpretation proposed so far invokes the internal instability resulting from the large-scale interaction between upper and interior oceanic layers. Here we show, using a new high-resolution simulation of the realistic North Pacific Ocean, that ocean eddies are instead sustained by a different process that involves small-scale mixed-layer instabilities set up by large-scale atmospheric forcing in winter. This leads to a seasonal evolution of the eddy kinetic... |
| Tipo: Text |
Palavras-chave: Earth sciences; Oceanography. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00250/36098/34642.pdf |
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