Oxygen uptake and vertical transport during deep convection events in the Labrador Sea and its interannual variability
Bibliographic record
Abstract
Dissolved oxygen (DO) is essential for marine life and biogeochemical cycling.\nTo a first order approximation, DO is determined by the competition between ocean ventilation and biological productivity. \nApproximately 21% of the atmospheric gases is oxygen, and the waters at the ocean surface are enriched in oxygen. \nVentilation occurs through a suite of physical processes that brings the DO-rich surface waters into the interior ocean. \nThis dissertation combines two works that closely examine the ventilation of oxygen in the region of deep water formation, and explore the relationship between air-sea oxygen flux and surface forcing aiming at deepening our understanding of the processes that regulate he DO inventory. \nThrough these analyses we develop a framework to understand the oxygen to ocean heat content (O2-OHC) ratio in the ocean interior. \nBoth works focus on the Labrador Sea and include a theoretical development and its validation using a suite of numerical sensitivity experiments. \n\nThe first work leads to two main conclusions.\n1) Both the duration and the intensity of the winter-time cooling are important to the total O2 uptake for a convective event. \nStronger cooling leads to deeper convection and brings oxygen into deeper depths. \nLonger duration of the cooling period increases the total amount of oxygen uptake over the convective season. \n2) The bubble-mediated influx of oxygen can increase oxygen uptake, but part of the contribution is compensated by the weakening the diffusive influx because the air-sea disequilibrium of oxygen is shifted towards supersaturation. \nThe degree of compensation between the diffusive and bubble-mediated gas exchange depends on the relative strength of oceanic vertical mixing and the gas transfer velocity. \nStrong convective mixing reduces the degree of compensation so that the two components of gas exchange together drive exceptionally strong oceanic oxygen uptake. \nA numerical model with idealized domain and non-hydrostatic dynamics is used to test the hypotheses in this work. \n\nThe second work explores what controls the O2-OHC ratio during deep convection. \nModels of different complexities ranging from 1-D convective adjustment model to a regional ocean circulation model that includes a complex biogeochemical module are used.\nThe bubble injection increases the oxygen flux and the magnitude of the O2-OHC ratio under intense convective events. \nLonger cooling duration leads to a larger magnitude of the O2-OHC ratio. \nThe pre-conditioning of the vertical gradients in oxygen and temperature are important for the O2-OHC ratio under different climate scenarios. \n\nWith these two works, we highlight a few key mechanisms that are important to regulate the DO inventory in the ocean interior, but further efforts are needed to understand the global DO variability and to constrain the deoxygenation potential under a warming climate.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".