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Reduced oxygenation at intermediate depths of the southwest Pacific during the last glacial maximum

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Durand Axel, Chase Zanna, Noble Taryn L., Bostock Helen, Jaccard Samuel L., Townsend Ashley T., Bindoff Nathaniel L., Neil Helen, Jacobsen Geraldine,
Project SeaO2 - Past changes in Southern Ocean overturning circulation - implications for the partitioning of carbon and oxygen between the ocean and the atmosphere
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Original article (peer-reviewed)

Journal Earth and Planetary Science Letters
Volume (Issue) 491
Page(s) 48 - 57
Title of proceedings Earth and Planetary Science Letters
DOI 10.1016/j.epsl.2018.03.036

Abstract

To investigate changes in oxygenation at intermediate depths in the southwest Pacific between the Last Glacial Maximum (LGM) and the Holocene, redox sensitive elements uranium and rhenium were measured in 12 sediment cores located on the Campbell and Challenger plateaux offshore from New Zealand. The core sites are currently bathed by Subantarctic Mode Water (SAMW), Antarctic Intermediate Water (AAIW) and Upper Circumpolar Deep Water (UCDW). The sedimentary distributions of authigenic uranium and rhenium reveal reduced oxygen content at intermediate depths (800–1500 m) during the LGM compared to the Holocene. In contrast, data from deeper waters (≥1500 m) indicate higher oxygen content during the LGM compared to the Holocene. These data, together with variations in benthic foraminiferal δ13C, are consistent with a shallower AAIW–UCDW boundary over the Campbell Plateau during the LGM. Whilst AAIW continued to bathe the intermediate depths (≤1500 m) of the Challenger Plateau during the LGM, the data suggest that the AAIW at these core sites contained less oxygen compared to the Holocene. These results are at odds with the general notion that AAIW was better oxygenated and expanded deeper during the LGM due to stronger westerlies and colder temperatures. These findings may be explained by an important change in AAIW formation and circulation.
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