Nitrogen Isotope Evidence for Changing Arctic Ocean Ventilation Regimes During the Cenozoic
In this work, I report on the coupling of dinitrogen (N 2 ) fixation and denitrification in oxygen-deficient waters of the Arctic Ocean during the Paleogene. This coupling fertilized marine phytoplankton growth and favored organic carbon burial. Reduced vertical mixing due to salinity stratification...
| Published in: | Geophysical Research Letters |
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| Main Author: | |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Wiley
2022
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| Subjects: | |
| Online Access: | https://hdl.handle.net/10037/26926 https://doi.org/10.1029/2022GL099512 |
| Summary: | In this work, I report on the coupling of dinitrogen (N 2 ) fixation and denitrification in oxygen-deficient waters of the Arctic Ocean during the Paleogene. This coupling fertilized marine phytoplankton growth and favored organic carbon burial. Reduced vertical mixing due to salinity stratification in a tectonically closed oceanic basin created conditions favorable for N 2 -fixation by phytoplankton harboring diazotrophic bacterial symbionts. A positive shift of 5‰ in the δ 15 N record indicates a change in the main source of biologically available nitrogen due to rapidly changing nutrient availability. I interpret this shift as a switch to Atlantic-sourced nitrate as the main nitrogen source owing to the opening of the Arctic-Atlantic gateway to the northern North Atlantic. While the timing of the opening is still disputed among the available Arctic records, I use evidence from the northern North Atlantic to argue that the Arctic Ocean has been fully ventilated since the early Neogene. |
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