SailBuoy Ocean Currents: Low Cost Upper Layer Ocean Current Measurements in a Large Geographical Area.
Supervisor: Lars R. Hole (Norwegian Meteorol Inst)
The measurement of ocean currents is essential for offshore industries and the transportation sector, as well as for scientific research questions especially validation of ocean and atmospheric simulation models but also ecosystem models when considering questions such as larval dispersal. Traditional in-situ measurement techniques are time and resource consuming and therefore sparse. This work introduces an alternative to the existing methods for measuring ocean currents: The SailBuoy Ocean Currents is an unmanned surface vehicle that can navigate autonomously to predefined way-points. Its power is being supplied by integrated batteries and solar panels allowing for it to spend several months at sea. With the integrated 600 kHz Acoustic Doppler Current Profiler (ADCP) vertical current velocity profiles of the underlying water column can be measured. The here presented data, collected on two validation campaigns, indicate a satisfying correlation of the SailBuoy ADCP data with traditional techniques such as bottom mounted and moored current profilers and moored single-point current meters within the water column. Correlation was found to be highest in tidal signals, strong current and calm weather conditions, while low current speeds and varying high wave and wind conditions reduced the SailBuoy’s measurement capabilities. Not yet resolved is a systematic offset between the measurements obtained by the SB and the reference instruments of ± 0.03m/s. Possible reasons are discussed to be differences between instruments by different providers as well as changes in background noise levels due to environmental conditions. Under the prerequisite that this issue can be resolved, the findings show that the SailBuoyOcean Currents is a good lowcost alternative to traditional measurement techniques that can cover large geographical areas autonomously. It has proven to be an easy to handle tool for research campaigns in- and offshore.