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Creators/Authors contains: "Thomson, Jim"

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  1. Wind, wave, and acoustic observations are used to test a scaling for ambient sound levels in the ocean that is based on wind speed and the degree of surface wave development (at a given wind speed). The focus of this study is acoustic frequencies in the range 1-20 kHz, for which sound is generated by the bubbles injected during surface wave breaking. Traditionally, ambient sound spectra in this frequency range are scaled by wind speed alone. In this study, we investigate a secondary dependence on surface wave development. For any given wind-speed, ambient sound levels are separated into conditions in which waves are 1) actively developing or 2) fully developed. Wave development is quantified using the non-dimensional wave height, a metric commonly used to analyze fetch or duration limitations in wave growth. This simple metric is applicable in both coastal and open ocean environments. Use of the wave development metric to scale sound spectra is first motivated with observations from a brief case study near the island of Jan Mayen (Norwegian Sea), then robustly tested with long time-series observations of winds and waves at Ocean Station Papa (North Pacific Ocean). When waves are actively developing, ambient sound levels are elevated 2-3 dB across the 1-20 kHz frequency range. This result is discussed in the context of sound generation during wave breaking and sound attenuation by persistent bubble layers. 
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  2. Seafloor moorings measuring pressure and temperature were deployed from April to September 2023 at three sites near the route of the fiber optic telecommunications cable that extends offshore of Oliktok Point, Alaska. The raw data data (1 Hertz (Hz) sampling) are processed for hourly estimates of the ocean surface wave conditions, along with average seawater temperature and average depth. The sites were ice-covered from April to July, then mostly open water in August and September. The data were collected to calibrate proxy wave measurements using Distributed Acoustic Sensing (DAS) from the telecommunications cable. 
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  3. Abstract In the past decade, two large marine heatwaves (MHWs) formed in the northeast Pacific near Ocean Station Papa (OSP), one of the oldest oceanic time series stations. Physical, biogeochemical, and biological parameters observed at OSP from 2013 to 2020 are used to assess ocean response and potential impacts on marine life from the 2019 northeast Pacific MHW. The 2019 MHW reached peak surface and subsurface temperature anomalies in the summertime and had both coastal, impacting fisheries, and offshore consequences that could potentially affect multiple trophic levels in the Gulf of Alaska. In the Gulf of Alaska, the 2019 MHW was preceded by calm and stratified upper ocean conditions, which preconditioned the enhanced surface warming in late spring and early summer. The MHW coincided with lower dissolved inorganic carbon and higher pH of surface waters relative to the 2013–2020 period. A spike in the summertime chlorophyll followed by a decrease in surface macronutrients suggests increased productivity in the well‐lit stratified upper ocean during summer 2019. More blue whale calls were recorded at OSP in 2019 compared to the prior year. This study shows how the utility of long‐term, continuous oceanographic data sets and analysis with an interdisciplinary lens is necessary to understand the potential impact of MHWs on marine ecosystems. 
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  4. Existing codes spanning 2009-2012 for working with Surface Wave Instrument Floats with Tracking (SWIFT) data. Codes for both telemetry and post-processed data. Buoy versions v3, v3, and microSWIFTs supported. 
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  5. This dataset contains processed ocean surface gravity wave parameters derived from interrogation of a seafloor fiber with distributed acoustic sensing (DAS). These measurements were taken on a fiber within a cable owned by Quintillion extending off the coast near Oliktok Point, Alaska in November 2021 and August 2022. Processing includes calculation of frequency-dependent, channel-specific correction factors using collocated wave buoy (SWIFT) observations, which is then multiplied by the PSD of raw strain-rate. A depth-attenuation correction is then also applied. Dataset includes the raw strain-rate spectra and the derived wave spectra, as well as bulk wave parameters including significant wave height (Hs), peak wave period (Tp), and energy-weighted wave period (Te). 
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  6. This dataset includes vessel-based water-column profile and seabed data collected around Blossom Shoals, a shoal complex offshore of Icy Cape in northwestern Alaska (in the Chukchi Sea). Data were collected from the Research Vessel (R/V) Sikuliaq (offshore) and a companion workboat (inshore). Water-column profile data include salinity, temperature, depth, and turbidity data collected using a RBR Maestro CTD/Tu (conductivity, temperature, depth, turbidity) sensor package. Profile data also include median diameters and volumetric concentrations of suspended particles, where were collected using a Sequoia LISST200X (laser in situ scattering transmissometer). Seabed grab samples were collected from the Sikuliaq using a shipek grab sampler and from the workboat using a hand-operated mini van veen grab sampler. Samplers were bagged and returned chilled to the lab for particle-size analyses in an Escitec Bettersizer S3Plus laser diffraction sensor. Sediments were not treated for organics due to generally low organic contents. Samples contained primarily sand except for a few isolated locations where mud was found. Data were collected in November 2019 during the fall freezeup season when pancake ice were beginning to form. Data were also collected in late September and early October 2020 during a mooring recovery cruise. Single-beam bathymetry data (which were only collected in 2020) were gathered using a commercial fish finder mounted on the workboat and connected to a data logger. 
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  7. This dataset contains processed ocean surface gravity wave parameters derived from interrogation of a seafloor fiber with distributed acoustic sensing (DAS). These measurements were taken on a fiber within a cable owned by Quintillion extending off the coast near Oliktok Point, Alaska in November 2021 and August 2022. Processing includes calculation of frequency-dependent, channel-specific correction factors using collocated wave buoy (SWIFT) observations, which is then multiplied by the PSD of raw strain-rate. A depth-attenuation correction is then also applied. Dataset includes the raw strain-rate spectra and the derived wave spectra, as well as bulk wave parameters including significant wave height (Hs), peak wave period (Tp), and energy-weighted wave period (Te). 
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