The Back Story
More than half of the world’s population lives in coastal areas and needs to address coastal flooding. There is also a requirement to monitor inshore waters affected by agricultural runoff and industrial pollution.
As a result, there is interest in understanding the origins of underwater “internal waves”, which impact the mixing, exchange, and flushing of coastal waters. In 2015, Canadian researchers were studying the origin of internal waves in Saguenay Fjord in Quebec, Canada.
Operating in a small research boat, the Canadian team used a V-Wing 850 towed underwater depressor with a Teledyne Sentinel V Acoustic Doppler Current Profiler (ADCP) to measure currents to 50-meter depth.
- A towed underwater depressor with an ADCP offers an affordable, efficient solution for survey work
- A towed body can carry an ADCP and other sensors
- Dual ADCPs oriented to look up and down enhance the flexibility of the towed method
- Towing an ADCP avoids interfering bubble layers found below larger vessels
After crossing the boundary between two water masses, the team recorded the generation of large 10-meter high, underwater waves. The Canadian team’s field observations showed the generation of large amplitude internal solitary waves. This work represents a rare case where internal wave generation is clearly observed at sea.
The researchers found the cause for the large waves to be an intrusive horizontal plume whose currents disturbed density layers. Although such plumes are known in coastal seas, their role in generating large underwater waves was not previously recorded. An improved understanding of ocean wave development can help to support the safety of coastal populations across the globe.