Physical Oceanographic and Acoustic Observations of the Beaufort Sea and its Subsurface Duct Sensitivity to Deterministic Ocean Features
Bibliographic record
Abstract
The Arctic Ocean is rapidly transforming due to climate change, and this thesis analyzes two, year-long ocean-acoustic data sets to quantify variability in the thermohaline, current and ice structure and examine the implications for acoustic propagation in the Beaufort Sea. The two field efforts are the Canada Basin AcousticPropagation Experiment (CANAPE) and the Coordinated Arctic Acoustic Thermometry Experiment (CAATEX). These results are important since acoustics offers a unique tool for the Arctic under ice communication, navigation, and remote sensing.A key acoustic feature of the Beaufort Sea is the Beaufort duct created by the Pacific winter water (PWW), which is sandwiched between the shallow Pacific summer water (PSW) and the deeper Atlantic water (AW). This is important because this duct allows for long-range transmission without lossy interactions with sea ice or surface waves. In general, we find this duct can trap from 2-6 acoustic modes in the frequency range between several tens of Hz and several hundreds of Hz. Since fluctuations can alter the number of trapped modes and affect Transmission loss, we have analyzed variability due to spice, internal waves, eddies, and near-inertial waves, and we find spicy thermohaline structure is observed to be the most significant source of variability in the top 100 m, followed by eddies and internal waves.Acoustic interaction with the ice cover is another critical factor affecting arctic acoustics, so we have analyzed high-frequency acoustic scattering statistics from the CANAPE. Five important surface scattering epochs were identified over the seasonal cycle: open water, initial ice formation, ice solidification, ice thickening, and ice melting. The most significant changes in statistics are seen during the formation, solidification, and melting. The statistical features are comparable throughout the CANAPE region, implying similar ice properties.The stability of acoustic propagation in the Beaufort duct is another aspect of this thesis. We analyzed the oceanographic measurements from the CANAPE and CAATEX, and focused on the problem of mode coupling in the Beaufort duct,induced by deterministic ocean features such as eddies and intrusions. Here we find that deterministic variability in the PSW due to spice and stronger halocline eddies can result in enhanced coupling between acoustic modes in and out of the BD.\nHere we use the mode interaction parameter (MIP), which is a non-dimensional quantity, Γmn that quantifies the mode coupling strength between mode m (a duct mode) and all the other n modes. Strong/moderate-weak coupling is determined by MIP greater-than/less-than 1. The MIP is a function of acoustic frequency and horizontal structure, which we define as the typical half-width of Gaussian perturbation (Δ) in this thesis. Our result showed that for both large and small Δ, Γmn goes to zero, and maximal coupling occurs when Δ ranges between 1.5 and 2.2 km.
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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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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 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".