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    Meridional circulation during the Last Glacial Maximum explored through a combination of South Atlantic δ18O observations and a geostrophic inverse model

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    2006GC001383.pdf (525.1Kb)
    Date
    2006-11-15
    Author
    Gebbie, Geoffrey A.  Concept link
    Huybers, Peter  Concept link
    Metadata
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    Citable URI
    https://hdl.handle.net/1912/1373
    As published
    https://doi.org/10.1029/2006GC001383
    DOI
    10.1029/2006GC001383
    Keyword
     Inverse modeling; Last Glacial Maximum; Meridional ocean circulation; Geostrophy 
    Abstract
    The vertical profile of meridional transport in the South Atlantic is examined by combining paleoceanographic observations with a geostrophic circulation model using an inverse method. δ18Ocalcite observations along the margins of the South Atlantic show that upper-ocean cross-basin differences were weaker during the Last Glacial Maximum (LGM) than the Holocene. The δ18Ocalcite observations can be explained by a shift of water-mass properties without any change in the overturning circulation. Alternatively, they may indicate a reduced LGM cross-basin density difference and, via the thermal wind relation, a reduced vertical shear. Model inversions of δ18Ocalcite are found to require meridional transports different from the modern only after three assumptions are made: temperature and salinity distributions are spatially smooth, the relationship between salinity and δ18Owater is linear and spatially invariant, and LGM temperatures are known to within 1°C along the margins. The last assumption is necessary because an independent constraint on temperature or salinity is required to determine density from δ18Ocalcite observations. δ18Ocalcite observations are clearly useful, but before any firm constraints can be placed on LGM meridional transport, it appears necessary to better determine the relationship between δ18Ocalcite and density.
    Description
    Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 7 (2006): Q11N07, doi:10.1029/2006GC001383.
    Collections
    • Geology and Geophysics (G&G)
    Suggested Citation
    Geochemistry Geophysics Geosystems 7 (2006): Q11N07
     

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