Variations in Denitrification and Ventilation Within the Arabian Sea Oxygen Minimum Zone During the Holocene
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- Pratima M. Kessarkar
- CSIR‐National Institute of Oceanography Dona Paula Goa India
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- S. W. A. Naqvi
- CSIR‐National Institute of Oceanography Dona Paula Goa India
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- M. Thamban
- National Centre for Antarctic and Ocean Research Vasco da Gama Goa India
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- Lina L. Fernandes
- CSIR‐National Institute of Oceanography Dona Paula Goa India
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- Christopher Siebert
- GEOMAR Helmholtz Centre for Ocean Research Kiel Kiel Germany
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- V. Purnachandra Rao
- CSIR‐National Institute of Oceanography Dona Paula Goa India
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- H. Kawahata
- Ocean Research Institute University of Tokyo Tokyo Japan
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- V. Ittekkot
- University of Bremen Bremen Germany
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- Martin Frank
- GEOMAR Helmholtz Centre for Ocean Research Kiel Kiel Germany
説明
<jats:title>Abstract</jats:title><jats:p>The continental slope of India is exposed to an intense perennial oxygen minimum zone (OMZ) supporting pelagic denitrification. Sediments that are presently in contact with the lower boundary of the denitrification zone indicate marked changes in the intermediate and bottom waters ventilation of OMZ during the past 9,500 years. The δ<jats:sup>15</jats:sup>N of sediment suggests that the OMZ waters were less ventilated during the early Holocene (between 9.5 and 8.5 ka BP) resulting in intensified denitrifying conditions with an average δ<jats:sup>15</jats:sup>N value of 7.8‰, while at the same time stable Mo isotope composition (average δ<jats:sup>98</jats:sup>Mo of −0.02‰) indicates that the bottom waters that were in contact with the sediments were better oxygenated. By the mid‐Holocene OMZ became more oxygenated suppressing denitrification (average δ<jats:sup>15</jats:sup>N of 6.2‰), while bottom waters gradually became less oxygenated (average δ<jats:sup>98</jats:sup>Mo of 1.7‰). The mid‐Holocene reduction in denitrification coincided with a global decrease in atmospheric N<jats:sub>2</jats:sub>O as inferred from ice core records, which is consistent with a decreased contribution from the Arabian Sea. Since ~5.5 ka BP OMZ waters have again been undergoing progressive deoxygenation accompanied by increasing denitrification.</jats:p>
収録刊行物
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- Geochemistry, Geophysics, Geosystems
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Geochemistry, Geophysics, Geosystems 19 (7), 2179-2193, 2018-07
American Geophysical Union (AGU)