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Surf's up! Wave glider trials in the North Sea

05 February 2013

Scientists at Cefas are trialling a clever device that looks like a surf board but packs a wide range of sophisticated instruments to record a variety of marine conditions.

The autonomous wave glider, hired from US firm Liquid Robotics, was deployed off Lowestoft on 30 January. This marks the first time such a device has been tested in the southern North Sea, where tides and currents are strong and shipping is busy.

Wave glider (copyright Liquid Robotics)The 2m-long wave glider is self-propelled by wave action and has the capacity to travel thousands of miles. It is steered remotely from the operations base and has a built-in automatic identification system, which means that it can send alerts with advice to actively avoid shipping.

The suite of systems onboard the device is powered by batteries recharged by solar panels.

Alongside the standard fitments - of weather station, wave height and temperature sensors - the Cefas scientists have added instruments to measure oxygen concentration and saturation, turbidity (water cloudiness), the chlorophyll fluorescence of phytoplankton and salinity. These observations are being recorded by a specially integrated Cefas data logger and data are transmitted to shore via satellite telecommunications in near "real-time".

During the Cefas trial, which runs to March, the glider will transit north to Cefas' own Dowsing SmartBuoy site, about 25 miles off the Norfolk and Lincolnshire coasts. There it will make a comparison of the sensors on the wave glider with those on the SmartBuoy. After a few days of monitoring activity, the glider will set off for another SmartBuoy site further south at West Gabbard, 30 miles from the Suffolk and Essex coasts. It will then repeat the same monitoring pattern as at the Dowsing site.

The wave glider travels at around 1.5 knots and will need to cope with strong tides so the 120-mile journey between the two SmartBuoy sites may take several days. Once its work at the West Gabbard site is completed, it will turn north and transit back to Lowestoft for recovery (see map).

Wave glider map of North Sea trial

Wave glider's North Sea route: green line indicates initial transit to first, northern SmartBuoy site; the stars mark SmartBuoy locations; black line shows the trial route

Jo Foden, Cefas' Project Manager for these trials, said: "At present our observations at sea are made from a variety of platforms: moored instruments such as the SmartBuoys, plus our research vessel, FerryBox systems on ferries and other ships, satellite, etc. Despite this range, there are still some important gaps in data and our knowledge.

"The instruments mounted on the wave glider will enable us to plug some of those gaps. For instance, they should supply greater spatial coverage between platforms and more accurately determine the spatial representation of our SmartBuoys' data. We also anticipate that the instruments onboard will provide some valuable new information: for example, the chlorophyll fluorescence data can help to verify satellite observations, and other data will help to calibrate and validate our marine models. So, the wave glider is a flexible platform and new sensors can be added.

"Another big advantage of the wave glider," Jo continued, "is the ease of launching and recovery from a small vessel. This will mean that some costs are reduced and it provides flexibility: we can deploy it at short notice or change its track to make observations of unexpected and interesting phenomena at sea."

If the Cefas trial is successful there will be long-term benefits in using wave gliders. Not only will there be validation of a range of environmental characteristics, but there opens up the possibility of more collaborative work with neighbouring European states. Shared marine boundaries with neighbouring states have been areas of contention in the past, so a glider could be programmed to sample transboundary waters across the North Sea for bilateral research studies. This could save money and provide improved scientific understanding of the marine environment.

Fact file

  • The OSPAR Strategy[1] and the EU's Marine Strategy Framework Directive (MSFD)[2] are the key drivers of the UK's monitoring and assessment commitments. These policies require multiple environmental characteristics to be measured in near- and off-shore waters.
  • Nutrient, chlorophyll and phytoplankton data are vital for calculating the MSFD's indicators of Good Environmental Status, and to establish the thresholds for the assessment of eutrophication - where too much nutrient enrichment caused by human activity can lead to undesirable disturbance to ecosystem health and water quality.
  • Some of the UK's marine areas are not well covered in annual vessel surveys. For instance, while there is a SmartBuoy in the Celtic Sea, research vessel time is still required to service it and this is not sufficiently frequent to prevent data being lost due to bio-fouling on the instruments. The data transmitted back from a wave glider could be automatically checked for signs of bio-fouling and then re-called or instructed to "hold station" for cleaning if a research vessel was nearby.
  • At present there is a paucity of acoustic data routinely collected at sea. Such data are needed for MSFD assessments of underwater noise. SmartBuoys are noisy because of their moorings, and seabed units are vulnerable to trawling or interference. Wave gliders, originally designed for cetacean (e.g. dolphins) monitoring, are inherently quiet. Cefas has plans to mount acoustic instruments onboard the wave glider in future.

[1] Strategy of the OSPAR Commission for the Protection of the Marine Environment of the North-East Atlantic 2010-2020, OSPAR Agreement 2010-03
[2] Directive 2008/56/EC

Wave glider image © Liquid Robotics

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Last Modified: 27 April 2014