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    Annual Reversal of the Equatorial Intermediate Current in the Pacific: Observations and Model Diagnostics

    Source: Journal of Physical Oceanography:;2009:;Volume( 040 ):;issue: 005::page 915
    Author:
    Marin, Frédéric
    ,
    Kestenare, Elodie
    ,
    Delcroix, Thierry
    ,
    Durand, Fabien
    ,
    Cravatte, Sophie
    ,
    Eldin, Gérard
    ,
    Bourdallé-Badie, Romain
    DOI: 10.1175/2009JPO4318.1
    Publisher: American Meteorological Society
    Abstract: A large reversal of zonal transport below the thermocline was observed over a period of 6 months in the western Pacific Ocean between 2°S and the equator [from 26.2 Sv (1 Sv ≡ 106 m3 s?1) eastward in October 1999 to 28.6 Sv westward in April 2000]. To document this reversal and assess its origin, an unprecedented collection of ADCP observations of zonal currents (2004?06), together with a realistic OGCM simulation of the tropical Pacific, was analyzed. The results of this study indicate that this reversal is the signature of intense annual variability in the subsurface zonal circulation at the equator, at the level of the Equatorial Intermediate Current (EIC) and the Lower Equatorial Intermediate Current (L-EIC). In this study, the EIC and the L-EIC are both shown to reverse seasonally to eastward currents in boreal spring (and winter for the L-EIC) over a large depth range extending from 300 m to at least 1200 m. The peak-to-peak amplitude of the annual cycle of subthermocline zonal currents at 165°E in the model is ?30 cm s?1 at the depth of the EIC, and ?20 cm s?1 at the depth of the L-EIC, corresponding to a mass transport change as large as ?100 Sv for the annual cycle of near-equatorial zonal transport integrated between 2°S and 2°N and between 410- and 1340-m depths. Zonal circulations on both sides of the equator (roughly within 2° and 5.5° in latitude) partially compensate for the large transport variability. The main characteristics of the annual variability of middepth modeled currents and subsurface temperature (e.g., zonal and vertical phase velocities, meridional structure) are consistent, in the OGCM simulation, with the presence, beneath the thermocline, of a vertically propagating equatorial Rossby wave forced by the westward-propagating component of the annual equatorial zonal wind stress. Interannual modulation of the annual variability in subthermocline equatorial transport is discussed.
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      Annual Reversal of the Equatorial Intermediate Current in the Pacific: Observations and Model Diagnostics

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    contributor authorMarin, Frédéric
    contributor authorKestenare, Elodie
    contributor authorDelcroix, Thierry
    contributor authorDurand, Fabien
    contributor authorCravatte, Sophie
    contributor authorEldin, Gérard
    contributor authorBourdallé-Badie, Romain
    date accessioned2017-06-09T16:31:03Z
    date available2017-06-09T16:31:03Z
    date copyright2010/05/01
    date issued2009
    identifier issn0022-3670
    identifier otherams-69258.pdf
    identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4210907
    description abstractA large reversal of zonal transport below the thermocline was observed over a period of 6 months in the western Pacific Ocean between 2°S and the equator [from 26.2 Sv (1 Sv ≡ 106 m3 s?1) eastward in October 1999 to 28.6 Sv westward in April 2000]. To document this reversal and assess its origin, an unprecedented collection of ADCP observations of zonal currents (2004?06), together with a realistic OGCM simulation of the tropical Pacific, was analyzed. The results of this study indicate that this reversal is the signature of intense annual variability in the subsurface zonal circulation at the equator, at the level of the Equatorial Intermediate Current (EIC) and the Lower Equatorial Intermediate Current (L-EIC). In this study, the EIC and the L-EIC are both shown to reverse seasonally to eastward currents in boreal spring (and winter for the L-EIC) over a large depth range extending from 300 m to at least 1200 m. The peak-to-peak amplitude of the annual cycle of subthermocline zonal currents at 165°E in the model is ?30 cm s?1 at the depth of the EIC, and ?20 cm s?1 at the depth of the L-EIC, corresponding to a mass transport change as large as ?100 Sv for the annual cycle of near-equatorial zonal transport integrated between 2°S and 2°N and between 410- and 1340-m depths. Zonal circulations on both sides of the equator (roughly within 2° and 5.5° in latitude) partially compensate for the large transport variability. The main characteristics of the annual variability of middepth modeled currents and subsurface temperature (e.g., zonal and vertical phase velocities, meridional structure) are consistent, in the OGCM simulation, with the presence, beneath the thermocline, of a vertically propagating equatorial Rossby wave forced by the westward-propagating component of the annual equatorial zonal wind stress. Interannual modulation of the annual variability in subthermocline equatorial transport is discussed.
    publisherAmerican Meteorological Society
    titleAnnual Reversal of the Equatorial Intermediate Current in the Pacific: Observations and Model Diagnostics
    typeJournal Paper
    journal volume40
    journal issue5
    journal titleJournal of Physical Oceanography
    identifier doi10.1175/2009JPO4318.1
    journal fristpage915
    journal lastpage933
    treeJournal of Physical Oceanography:;2009:;Volume( 040 ):;issue: 005
    contenttypeFulltext
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    DSpace software copyright © 2002-2015  DuraSpace
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