A Spar Buoy for High-Frequency Wave Measurements and Detection of Wave Breaking in the Open Ocean

Waves and wave breaking play a significant role in the air-sea exchanges of momentum, sea spray aerosols and trace gases such as CO2 but few direct measurements of wave breaking have been obtained in the open ocean (far from the coast). This paper describes the development and initial deployments on two research cruises of an autonomous spar buoy that was designed to obtain such open ocean measurements. The buoy was equipped with: capacitance wave wires and accelerometers to measure surface elevation and wave breaking; downward looking still and video digital cameras to obtain images of the sea surface; sub-surface acoustic and optical sensors to detect bubble clouds from breaking waves. The buoy was free drifting and was designed to collect data autonomously for days at a time before being recovered. Therefore, on the two cruises during which the buoy was deployed, this allowed a variety of sea states to be sampled in mean wind speeds which ranged from 5 to 18 m/s.