Gebbie, Geoffrey AHuybers, Peter2009-11-052006Gebbie, Geoffrey A., and Peter J. Huybers. 2006. Meridional circulation during the Last Glacial Maximum explored through a combination of South Atlantic δ18O observations and a geostrophic inverse model. Geochemistry Geophysics Geosystems 7(11): 1-15.1525-2027http://nrs.harvard.edu/urn-3:HUL.InstRepos:3382983The vertical profile of meridional transport in the South Atlantic is examined by combining paleoceanographic observations with a geostrophic circulation model using an inverse method. δ 18Ocalcite 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 δ 18Ocalcite 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 δ 18Ocalcite 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 δ 18Owater 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 δ 18Ocalcite observations. δ 18Ocalcite 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 δ 18Ocalcite and density.en-USinverse modelingLast Glacial Maximummeridional ocean circulationgeostrophyJournal Article2009-11-0510.1029/2006GC001383