Observations and modeling of the tidal bottom boundary layer on the southern flank of Georges Bank
Bibliographic record
Abstract
We examine the vertical structure of the tidally driven bottom boundary layer during nearly homogeneous ( N 2 < 10 −5 s −2 ) and strongly stratified ( N 2 ∼ 10 −4 s −2 ) conditions in a shallow coastal region dominated by semidiurnal tides. From moored array and shipboard measurements taken at a 76‐m‐deep study site on the southern flank of Georges Bank, we infer tidal velocity profiles, bottom stress estimates, Richardson numbers, and turbulent dissipation rates. On the basis of our measurements, we discuss changes in tidal boundary‐layer dynamics in the presence of weak and strong stratification. We compare observations to results from two different one‐dimensional numerical circulation models: a two‐layer eddy viscosity model with linear eddy viscosity distribution in the lower layer and constant eddy viscosity in the upper layer (2LK), and a continuously varying eddy viscosity model (both in time and in the vertical) with Mellor‐Yamada level 2.5 closure (MY2.5). Both models compare favorably with observations during nearly homogeneous conditions, but show disagreement with data when the water column is strongly stratified. In the case of 2LK, the model overestimates the bottom stress and does not reproduce the observed velocity maximum at mid‐depth. This behavior is clearly related to the absence of buoyancy effects in the simplistic turbulence closure scheme. The advanced MY2.5 scheme, on the other hand, reproduces the observed velocity distribution and bottom stress well. However, the model also predicts an abrupt adjustment from the turbulent bottom boundary layer to a nearly nonturbulent region above which is not supported by our Richardson number estimates and observed turbulent dissipation rates. Potential reasons explaining the discrepancies between observations and MY2.5 include high‐frequency internal‐wave mixing and underestimation of the critical Richardson number used by the model to describe the transition from active to decaying turbulence.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".