Journal
PALEOCEANOGRAPHY
Volume 32, Issue 10, Pages 1000-1017Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1002/2017PA003118
Keywords
oxygen isotopes; carbon isotopes; Southern Ocean; glacial ocean circulation; intermediate water
Funding
- PAGES
- NSF [OCE-0823487, 0823549-03, OCE-1003500]
- Hanse-Wissenschaftskolleg
- NOAA Climate and Global Change Program
- PAGES
- NSF [OCE-0823487, 0823549-03, OCE-1003500]
- Hanse-Wissenschaftskolleg
- NOAA Climate and Global Change Program
- Directorate For Geosciences [0823549] Funding Source: National Science Foundation
- Directorate For Geosciences
- Division Of Earth Sciences [1440015] Funding Source: National Science Foundation
- Division Of Ocean Sciences [0823549] Funding Source: National Science Foundation
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Enhanced vertical gradients in benthic foraminiferal C-13 and O-18 in the Atlantic and Pacific during the last glaciation have revealed that ocean overturning circulation was characterized by shoaling of North Atlantic sourced interior waters; nonetheless, our understanding of the specific mechanisms driving these glacial isotope patterns remains incomplete. Here we compare high-resolution depth transects of Cibicidoides spp. C-13 and O-18 from the Southwest Pacific and the Southwest Atlantic to examine relative changes in northern and southern sourced deep waters during the Last Glacial Maximum (LGM) and deglaciation. During the LGM, our transects show that water mass properties and boundaries in the South Atlantic and Pacific were different from one another. The Atlantic between similar to 1.0 and 2.5km was more than 1 enriched in C-13 relative to the Pacific and remained more enriched through the deglaciation. During the LGM, Atlantic O-18 was similar to 0.5 more enriched than the Pacific, particularly below 2.5km. This compositional difference between the deep portions of the basins implies independent deep water sources during the glaciation. We attribute 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 be supported in the absence of a net east-west circumpolar pressure gradient above the sill depth. We surmise that through the LGM and early deglaciation, shoaled northern sourced waters were unable to escape the Atlantic and contribute to deep water formation in the Southern Ocean.
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