| Autor: |
Craig L. McNeil, Eric A. D’Asaro, Mark A. Altabet, Roberta C. Hamme, Emilio Garcia-Robledo |
| Jazyk: |
angličtina |
| Rok vydání: |
2023 |
| Předmět: |
|
| Zdroj: |
Frontiers in Marine Science, Vol 10 (2023) |
| Druh dokumentu: |
article |
| ISSN: |
2296-7745 |
| DOI: |
10.3389/fmars.2023.1134851 |
| Popis: |
Oxygen Deficient Zones (ODZs) of the world’s oceans represent a relatively small fraction of the ocean by volume ( 300 dbar). We discriminate biologically produced N2 (ie., denitrification) from N2 in excess of saturation due to physical processes (e.g., mixing) using a new tracer – ‘preformed excess-N2’. We used inert dissolved argon (Ar) to help test the assumption that preformed excess-N2 is indeed conservative. We used the shipboard measurements to quantify preformed excess-N2 by cross-calibrating the gas tension method to the nutrient-deficit method. At 17 °N preformed excess-N2 decreased from approximately 28 to 12 µmol/kg over σ0 = 24–27 kg/m3 with a resulting precision of ±1 µmol N2/kg; at 12 °N values were similar except in the potential density range of 25.7< σ0< 26.3 where they were lower by 1 µmol N2/kg due likely to being composed of different source waters. We then applied these results to gas tension and O2 (< 3 µmol O2/kg) profiles measured by the nearby float to obtain the first autonomous biogenic N2 profile in the open ocean with an RMSE of ± 0.78 µM N2, or ± 19%. We also assessed the potential of the method to measure denitrification rates directly from the accumulation of biogenic N2 during the float drifts between profiling. The results suggest biogenic N2 rates of ±20 nM N2/day could be detected over >16 days (positive rates would indicate denitrification processes whereas negative rates would indicate predominantly dilution by mixing). These new observations demonstrate the potential of the gas tension method to determine biogenic N2 accurately and precisely in future studies of ODZs. |
| Databáze: |
Directory of Open Access Journals |
| Externí odkaz: |
|
