From Mixing to the Large Scale Circulation: How the Inverse Cascade Is Involved in the Formation of the Subsurface Currents in the Gulf of Guinea

Autor: Isabelle Dadou, Bernard Bourlès, Claire Ménesguen, Julien Jouanno, Yves Morel, Sophie Cravatte, Ryan M. Holmes, Fernand Assene, Micael Aguedjou, Audrey Delpech, Frédéric Marin, Ariane Koch-Larrouy, Gaël Alory, Alexis Chaigneau
Přispěvatelé: Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Université de Douala, Université d’Abomey-Calavi (UAC), Laboratoire d'Océanographie Physique et Spatiale (LOPS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), University of New South Wales [Sydney] (UNSW), Instrumentation, Moyens Analytiques, Observatoires en Géophysique et Océanographie (IMAGO) (IMAGO), Institut de Recherche pour le Développement (IRD [France-Ouest]), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université d’Abomey-Calavi = University of Abomey Calavi (UAC), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)
Jazyk: angličtina
Rok vydání: 2020
Předmět:
Pycnocline
010504 meteorology & atmospheric sciences
friction
Subsurface currents
Mesoscale meteorology
Zonal and meridional
lcsh:Thermodynamics
01 natural sciences
SEUC
Potential vorticity
lcsh:QC310.15-319
equatorial atlantic
mixing
14. Life underwater
friction 19
[SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography
lcsh:QC120-168.85
0105 earth and related environmental sciences
Fluid Flow and Transfer Processes
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]
Equatorial Atlantic
010505 oceanography
Advection
Mechanical Engineering
vortices
Geophysics
Condensed Matter Physics
Vortex
13. Climate action
Anticyclone
NEUC (North Equatorial Undercurrents)
SEUC (South Equatorial Undercurrents)
NEUC
lcsh:Descriptive and experimental mechanics
Geology
Zdroj: Fluids
Fluids, MDPI, 2020, 5 (3), pp.147. ⟨10.3390/fluids5030147⟩
Fluids (2311-5521) (MDPI AG), 2020-09, Vol. 5, N. 3, P. 147 (36p.)
Fluids, 2020, 5 (3), pp.147. ⟨10.3390/fluids5030147⟩
Volume 5
Issue 3
Fluids, Vol 5, Iss 147, p 147 (2020)
ISSN: 2311-5521
DOI: 10.3390/fluids5030147⟩
Popis: In this paper, we analyse the results from a numerical model at high resolution. We focus on the formation and maintenance of subsurface equatorial currents in the Gulf of Guinea and we base our analysis on the evolution of potential vorticity (PV). We highlight the link between submesoscale processes (involving mixing, friction and filamentation), mesoscale vortices and the mean currents in the area. In the simulation, eastward currents, the South and North Equatorial Undercurrents (SEUC and NEUC respectively) and the Guinea Undercurrent (GUC), are shown to be linked to the westward currents located equatorward. We show that east of 20°
W, both westward and eastward currents are associated with the spreading of PV tongues by mesoscale vortices. The Equatorial Undercurrent (EUC) brings salty waters into the Gulf of Guinea. Mixing diffuses the salty anomaly downward. Meridional advection, mixing and friction are involved in the formation of fluid parcels with PV anomalies in the lower part and below the pycnocline, north and south of the EUC, in the Gulf of Guinea. These parcels gradually merge and vertically align, forming nonlinear anticyclonic vortices that propagate westward, spreading and horizontally mixing their PV content by stirring filamentation and diffusion, up to 20°
W. When averaged over time, this creates regions of nearly homogeneous PV within zonal bands between 1.5°
and 5°
S or N. This mean PV field is associated with westward and eastward zonal jets flanking the EUC with the homogeneous PV tongues corresponding to the westward currents, and the strong PV gradient regions at their edges corresponding to the eastward currents. Mesoscale vortices strongly modulate the mean fields explaining the high spatial and temporal variability of the jets.
Databáze: OpenAIRE
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