Effects of Variations in Boundary Current Strength on the Export Pathways of Convected Water Masses in the Labrador Sea
Bibliographic record
Abstract
The production of water masses formed by convection in the Labrador Sea (i.e. Labrador Sea Water, LSW) and its variability contributes to the variability of the Atlantic Meridional Overturning Circulation (AMOC). Several studies put the role of the Labrador Sea under renewed debate, and suggest a rather complex interplay between the production of the LSW, the boundary current and the eddy field. To this end, an increased effort is put in understanding the variability of the LSW, its export routes and associated export timescales. In this study, the effects of variations in boundary current strength on the export pathways of convected water masses are investigated. The same idealized eddy-resolving numerical model is used as Georgiou et al. (2019) which has proven to be capable of capturing the key dynamics of the Labrador Sea, like the annual cycle of convection, the process and timescales of restratification, and properties of the mesoscale eddy field. Model simulations are set-up with different scenarios of the density structure of the boundary current at inflow location (i.e. southern tip of Greenland). The variations result in respectively a 5% strengthening and 5% weakening of the boundary current, which corresponds to interannual variability of observed surface velocities. The model output demonstrates that boundary current variations start a chain of reactions, significantly changing the dynamics of the Labrador Sea. This has implications for deep convection processes in the interior of the basin and thus the export product. With a passive tracer analysis it is shown that convected water masses formed in the convection area are laterally steered along isopycnals by an eddy-induced shear flow from the interior towards the boundary current at the West-Greenland coast in deeper layers. A strengthening (weakening) of the boundary current yields a lighter (denser) water mass to be exported at shallower (deeper) layers out of the interior. The most intense entrainment into the boundary current occurs where both the density and depth of the convected water masses match the local water mass properties of the boundary current, and where eddies detach from the boundary current. The associated export timescales can be linked to the location where eddies detach, and to the strength of the eddy-induced shear flow. This study further highlights the implications for linking variability in the LSW production and export to AMOC variability as the total export of convected waters in the Labrador Sea is a mixture of multiyear convected waters. Based on density alone, measurements of water masses at the exit do not directly reveal the past-year dynamical state of the Labrador Sea. This emphasizes that a proper representation of mesoscale eddies in models is necessary for representing the export timescales and water mass properties of the LSW, and their response to changing forcing.
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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 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 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".