Complex upper ocean sound-speed structure measured by gliders in the Canada Basin.

Area of Science:

• Oceanography
• Acoustics
• Arctic studies

Background:

• The Canada Basin's upper ocean is rapidly changing due to warmer Pacific water inflow and sea ice decline.
• These changes significantly impact sound propagation in the Arctic.
• Understanding upper ocean structure is crucial for acoustic applications.

Purpose of the Study:

• To investigate spatial sound-speed variability in the Canada Basin's upper ocean.
• To quantify the influence of internal waves, halocline eddies, and spice on sound-speed fluctuations.
• To contextualize findings within the Beaufort Gyre's structure.

Main Methods:

• Utilized Seagliders to collect high-resolution temperature, salinity, and pressure data.
• Analyzed data across fronts and eddies during summer 2016 and 2017.
• Integrated Seaglider data with measurements from a sub-surface mooring.

Main Results:

• Spice was the primary driver of sound-speed fluctuations in the upper 100m, with a maximum of 3 m/s rms at 23m.
• Internal waves and halocline eddies caused distinct sound-speed fluctuations at 25m (0.73 m/s rms), 60m (0.43 m/s rms), and 270m (0.2 m/s rms).
• Findings complement existing mooring data and extend observations into the mixed layer.

Conclusions:

• Oceanographic changes in the Canada Basin significantly affect sound-speed variability.
• Spice dominates upper ocean sound-speed fluctuations, while eddies and internal waves contribute at deeper levels.
• Accurate acoustic modeling requires incorporating these dynamic oceanographic features.