Physical Oceanographic and Acoustic Observations of the Beaufort Sea and its Subsurface Duct Sensitivity to Deterministic Ocean Features
Notice bibliographique
Résumé
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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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».