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| Kolodziejczyk, Nicolas; Reverdin, Gilles; Lazar, Alban. |
| The Argo dataset is used to study the winter upper-ocean conditions in the northeastern subtropical (NEA) Atlantic during 2006-12. During late winter 2010, the mixed layer depth is abnormally shallow and a negative anomaly of density-compensated salinity, the so-called spiciness, is generated in the permanent pycnocline. This is primarily explained by unusual weak air-sea buoyancy flux during the late winter 2010, in contrast with the five other studied winters. Particularly deep mixed layers and strong spiciness anomalies are observed during late winter 2012. The 2010 winter conditions appear to be related to historically low North Atlantic Oscillation (NAO) and high tropical North Atlantic index (TNA). Interannual variability of the eastern subtropical... |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00624/73566/73010.pdf |
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| Kolodziejczyk, Nicolas; Reverdin, Gilles; Gaillard, Fabienne; Lazar, Alban. |
| Low-frequency variability of spiciness is observed in the Subtropical South Atlantic over the period 2002–2013 with the Argo gridded product In Situ Analysis System. Within the pycnocline, spiciness anomalies propagate at a mean speed of 0.04 ± 0.02 m s−1, the same speed as the gyre mean circulation, from the Agulhas Retroflection region off South Africa (~35°S–20°E) toward the South American coast (~18°S–35°W). After 2010, propagation is still found, but stationary local spiciness generation is also found over the Subtropical South Atlantic. This spiciness increase is associated with high values of vertical Turner angle below the mixed layer base during late winter. This suggests spice injection resulting from penetrative convective mixing due to air-sea... |
| Tipo: Text |
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| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00212/32310/30756.pdf |
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| Stammer, Detlef; Bracco, Annalisa; Achutarao, Krishna; Beal, Lisa; Bindoff, Nathaniel L.; Braconnot, Pascale; Cai, Wenju; Chen, Dake; Collins, Matthew; Danabasoglu, Gokhan; Dewitte, Boris; Farneti, Riccardo; Fox-kemper, Baylor; Fyfe, John; Griffies, Stephen M.; Jayne, Steven R.; Lazar, Alban; Lengaigne, Matthieu; Lin, Xiaopei; Marsland, Simon; Minobe, Shoshiro; Monteiro, Pedro M. S.; Robinson, Walter; Roxy, Mathew Koll; Rykaczewski, Ryan R.; Speich, Sabrina; Smith, Inga J.; Solomon, Amy; Storto, Andrea; Takahashi, Ken; Toniazzo, Thomas; Vialard, Jerome. |
| Natural variability and change of the Earth's climate have significant global societal impacts. With its large heat and carbon capacity and relatively slow dynamics, the ocean plays an integral role in climate, and provides an important source of predictability at seasonal and longer timescales. In addition, the ocean provides the slowly evolving lower boundary to the atmosphere, driving, and modifying atmospheric weather. Understanding and monitoring ocean climate variability and change, to constrain and initialize models as well as identify model biases for improved climate hindcasting and prediction, requires a scale-sensitive, and long-term observing system. A climate observing system has requirements that significantly differ from, and sometimes are... |
| Tipo: Text |
Palavras-chave: Ocean observing system; Ocean climate; Earth observations; In situ measurements; Satellite observations; Ocean modeling; Climate information. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00675/78724/80996.pdf |
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| Capet, Xavier; Estrade, Philippe; Machu, Eric; Ndoye, Siny; Grelet, Jacques; Lazar, Alban; Marie, Louis; Dausse, Denis; Brehmer, Patrice. |
| Upwelling off southern Senegal and Gambia takes place over a wide shelf with a large area where depths are shallower than 20 m. This results in typical upwelling patterns that are distinct (e.g., more persistent in time and aligned alongshore) from those of other better known systems, including Oregon and Peru where inner shelves are comparatively narrow. Synoptic to superinertial variability of this upwelling center is captured through a 4-week intensive field campaign, representing the most comprehensive measurements of this region to date. The influence of mesoscale activity extends across the shelf break and far over the shelf where it impacts the midshelf upwelling (e.g., strength of the upwelling front and circulation), possibly in concert with wind... |
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| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00374/48541/48842.pdf |
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| Camara, I.; Kolodziejczyk, Nicolas; Mignot, Juliette; Lazar, Alban; Gaye, Amadou T.. |
| The physical processes controlling the mixed layer salinity (MLS) seasonal budget in the tropical Atlantic Ocean are investigated using a regional configuration of an ocean general circulation model. The analysis reveals that the MLS cycle is generally weak in comparison of individual physical processes entering in the budget because of strong compensation. In evaporative regions, around the surface salinity maxima, the ocean acts to freshen the mixed layer against the action of evaporation. Poleward of the southern SSS maxima, the freshening is ensured by geostrophic advection, the vertical salinity diffusion and, during winter, a dominant contribution of the convective entrainment. On the equatorward flanks of the SSS maxima, Ekman transport mainly... |
| Tipo: Text |
Palavras-chave: Salinity; Seasonal variation; Tropical Atlantic; Vertical mixing. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00624/73563/73200.pdf |
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| Kolodziejczyk, Nicolas; Testor, Pierre; Lazar, Alban; Echevin, Vincent; Krahmann, Gerd; Chaigneau, Alexis; Gourcuff, Claire; Wade, Malick; Faye, Saliou; Estrade, Philippe; Capet, Xavier; Mortier, Laurent; Brehmer, Patrice; Schuette, Florian; Karstensen, Johannes. |
| Glider measurements acquired along 4 transects between Cap‐Vert Peninsula and the Cape Verde archipelago in the eastern tropical North Atlantic during March‐April 2014 were used to investigate fine‐scale stirring in an anticyclonic eddy. The anticyclone was formed near 12°N off the continental shelf and propagated north‐west towards the Cape Verde islands. At depth, between 100‐400 m, the isolated anticyclone core contained relatively oxygenated, low salinity South Atlantic Central Water, while the surrounding water masses were saltier and poorly oxygenated. The dynamical and thermohaline subsurface environment favored the generation of fine‐scale horizontal and vertical temperature and salinity structures in and around the core of the anticyclone. These... |
| Tipo: Text |
Palavras-chave: Submesoscale; Stirring; Tropical Atlantic; Meoscale eddy; Glider measurements; OMZ. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00450/56162/57708.pdf |
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| Camara, Ibrahima; Mignot, Juliette; Kolodziejczyk, Nicolas; Losada, Teresa; Lazar, Alban. |
| This study investigates the physical processes controlling the mixed layer buoyancy using a regional configuration of an ocean general circulation model. Processes are quantified by using a linearized equation of state, a mixed-layer heat, and a salt budget. Model results correctly reproduce the observed seasonal near-surface density tendencies. The results indicate that the heat flux is located poleward of 10° of latitude, which is at least three times greater than the freshwater flux that mainly controls mixed layer buoyancy. During boreal spring-summer of each hemisphere, the freshwater flux partly compensates the heat flux in terms of buoyancy loss while, during the fall-winter, they act together. Under the seasonal march of the Inter-tropical... |
| Tipo: Text |
Palavras-chave: Physical processes; Salt and heat budget; Density; Compensation. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00634/74636/74530.pdf |
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