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SUMMARY:Enhanced δ13C and δ18O differences between the South Atlantic an
 d South Pacific since the last glaciation gives us clues on how the ocean 
 exhaled: The deep gateway hypothesis'  - Elizabeth Sikes\, Rutgers Univers
 ity 
DTSTART:20180522T153000Z
DTEND:20180522T163000Z
UID:TALK106192@talks.cam.ac.uk
CONTACT:Andy Buckley
DESCRIPTION:Enhanced vertical gradients in benthic foraminiferal δ13C and
  δ18O in the Atlantic and Pacific during the last glaciation have reveale
 d that ocean overturning circulation was characterized by shoaling of Nort
 h Atlantic sourced interior waters\; nonetheless\, our understanding of th
 e specific mechanisms driving these glacial isotope patterns remains incom
 plete. Comparing high-resolution depth transects of benthic foraminiferal 
  δ13C and δ18O from the Southwest Pacific and the Southwest Atlantic\, e
 xamines the relative changes in northern and southern sourced deep waters 
 during the Last Glacial Maximum (LGM) and deglaciation. During the LGM\, o
 ur transects show that water mass properties and boundaries in the South A
 tlantic and Pacific were significantly different from one another below 25
 00 m. The compositional difference between the deep portions of the basins
  implies independent deep water sources during the glaciation. We attribut
 e these changes to a "deep gateway" effect whereby northern sourced waters
  shallower than the Drake Passage sill were unable to flow southward into 
 the Southern Ocean because a net meridional geostrophic transport cannot b
 e supported in the absence of a net east-west circumpolar pressure gradien
 t above the sill depth. We surmise that through the LGM and early deglacia
 tion\, shoaled northern sourced waters were unable to escape the Atlantic 
 and contribute to deep water formation in the Southern Ocean. 
LOCATION: Harker 1\, Department of Earth Sciences\, Downing Street
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