Quantifying Pacific Ocean nitrous oxide cycling using intramolecular isotope measurements and modeling
Abstract/Contents
- Abstract
- Nitrous oxide is one of the lesser-known greenhouse gases, yet its potential to warm the environment, on a per-molecule basis, is immense. Marine nitrous oxide production is concentrated in and around oxygen deficient zones, whose steep redox gradients allow for overlapping microbial processes that produce nitrous oxide. But the rates of these processes, and their relative importance in contributing to hotspots of nitrous oxide production, remain uncertain. This dissertation uses the intramolecular nitrogen isotopes (or isotopomers) of nitrous oxide to quantify its production in and around the eastern tropical North Pacific oxygen deficient zone. In Chapter 1, I find that high, near surface accumulations of nitrous oxide in this region are produced mainly by denitrification, with a smaller contribution from nitrification. In some core anoxic depths of the oxygen deficient zone, nitrous oxide cycling is not in steady state, while elsewhere, the isotopic content of nitrous oxide can be explained by denitrification with a positive site preference. In Chapter 2, I present a software package for isotopomer data processing and discuss the performance of this software. Ammonia-oxidizing archaea can produce nitrous oxide via a hybrid mechanism, so-called because it combines nitrogen derived from ammonium and nitrite to form nitrous oxide. In Chapter 3, I show that hybrid nitrous oxide production is inhibited by oxygen and reaches high yields at oxic-anoxic interfaces where ammonia oxidation is active. Integrating the information learned from these biogeochemical measurements, Chapter 4 presents a 1D advection-diffusion-reaction model constrained with nitrous oxide isotopomers to quantify nitrous oxide cycling in the eastern tropical North Pacific and test the sensitivity of that cycling to ocean deoxygenation and changes in organic matter export. Together, the results described in this dissertation show that nitrous oxide cycling in this region is a dynamic system that depends on low oxygen conditions and an organic matter source, conditions subject to change with ocean warming, deoxygenation, and increasing atmospheric N deposition. The constraints and parameters identified in this dissertation should provide a starting point for better implementations of nitrous oxide cycling in global biogeochemical models, making it possible to predict feedbacks between marine nitrous oxide cycling and climate change.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2023; ©2023 |
| Publication date | 2023; 2023 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Kelly, Colette LaMonica |
|---|---|
| Degree supervisor | Casciotti, Karen Lynn, 1974- |
| Thesis advisor | Casciotti, Karen Lynn, 1974- |
| Thesis advisor | Arrigo, Kevin R |
| Thesis advisor | Dekas, Anne |
| Thesis advisor | Francis, Christopher |
| Degree committee member | Arrigo, Kevin R |
| Degree committee member | Dekas, Anne |
| Degree committee member | Francis, Christopher |
| Associated with | Stanford Doerr School of Sustainability |
| Associated with | Stanford University, Department of Earth System Science |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Colette LaMonica Kelly. |
|---|---|
| Note | Submitted to the Department of Earth System Science. |
| Thesis | Thesis Ph.D. Stanford University 2023. |
| Location | https://purl.stanford.edu/yq704bd0082 |
Access conditions
- Copyright
- © 2023 by Colette LaMonica Kelly
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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