The Value of Learning New Approaches
By Caroline Cusack, Marine Institute | December 20, 2024
Contributions by Anthony English
On scientific cruises, such as the EuroGO-SHIP 2024 Ocean Climate Cruise, ship-based hydrographic scientists work in concert with the ship’s technicians to ensure the instruments meet the mission’s objectives, adjusting deployment strategies as needed. Troubleshooting and repairing equipment to minimise downtime during the expedition is an important step in the process and onboard training is essential and an invaluable way to improve skills. The role that technicians play in the development of innovation and the adoption of best practices should not be overlooked. Working with different scientific teams and ship crews affords them the opportunity to pick up and refine new techniques and pass them on. Anthony English is a ship’s technician for P&O Maritime Services, who are tendered by the Irish Marine Institute to run the two Irish Research Vessels (RVs): RV Celtic Explorer and RV Tom Crean. As a marine technician, he has a diverse range of responsibilities and performs tasks to ensure the smooth operation of scientific sensors at sea. He is responsible for the ship’s scientific equipment such as the CTD rosette system, and specialised scientific equipment brought onboard the vessel (e.g. lowered Acoustic Doppler Current Profiler – LADCP).
To demonstrate the importance of international collaboration and the willingness to adapt in advancing ship based hydrographic measurement, Anthony recounts his first experience receiving onboard training during a 2017 Transatlantic GO-SHIP survey.
“During this survey, I worked closely with a colleague, Marshall Swartz, from the Physical Oceanography group in Woods Hole Oceanographic Institution who has over 20 years of experience. Working with Marshall helped me gain valuable insights into maintaining the CTD and LADCP (this was our first time using the LADCP).
CTD oceanographic cable termination with Anthony and Marshall
mending the CTD winch wire.
Real-time CTD data as viewed in the dry laboratory on a PC (green = relative fluorescence, yellow = dissolved oxygen, red = temperature and blue = salinity).
The CTD is often operated at depths of thousands of meters, where the pressure is immense. One of the most vulnerable points in their deployment is the electrical termination, where two wires must be joined and made waterproof. If water penetrates the termination, it disrupts the electrical supply to the CTD, causing power irregularities and introducing data noise, such as spikes in the readings. This not only compromises the quality of the data collected but can also render entire datasets unusable. The termination method traditionally carried out on the Irish research vessels included sealing with resin to encapsulate the wires and cable armour. This can, however, fail under high pressure leading to water ingress especially when the CTD was deployed at great depths, leading to time-consuming rework and risk of data loss. Lost data is especially detrimental during expensive, time-sensitive research cruises, where continuous datasets are critical for scientific studies. With the high costs of mobilising research vessels and the narrow windows for data collection, ensuring robust and reliable terminations is important.
The new method we learned from our Woods Hole colleagues excludes the cable armour from the resin. This technique has significantly reduced termination failures on vessels like the RV Tom Crean and Celtic Explorer. The improved reliability saves time, enhances data quality, and ensures more consistent operations. It also underscores the value of learning from diverse perspectives to tackle persistent technical challenges. Embracing innovation improves efficiency, minimises risks, and supports the success of vital oceanographic mission”.
Anthony English
Collaborations through International GO-SHIP and EuroGO-SHIP have helped technicians and scientists make other improvements during hydrographic cruises. For example, the Marine Institute has replaced internal rubber tubing on Niskin bottles on the CTD rosette system with external springs on the Niskin bottles. This iteration reduces the risk of sample contamination by eliminating direct contact with the water sample inside the bottle. External springs are also more resistant to degradation from exposure to sunlight, temperature changes, and chemical reactions, ensuring more reliable and consistent performance over time.
CTD system bottle trigger mechanism with Antony and Marshall checking to make sure the mechanism is clean and ready for use.
CTD oceanographic cable termination: Final stages of mending the CTD winch wire.
As part of the EuroGO-SHIP project, GEOMAR (Helmholtz Center for Ocean Research Kiel) is currently working with the Marine Institute to set up an LADCP system on the Irish RV Celtic Explorer. In 2024, we purchased the ADCP units and throughout 2025 we will work with GEOMAR to apply their innovative approach of powering the LADCPs through the CTD winch cable rather than external batteries. This new setup will use the electrical power and communication capabilities of the armoured CTD winch cable to directly power the LADCP instruments and facilitate download of data after each CTD rosette cast. This in turn eliminates reliance on heavy external batteries to streamline operations and reduces the risk of battery-related issues during long or deep casts. This method also simplifies deployment and recovery, as it avoids handling additional components like battery packs. This approach reflects advancements in LADCP operational efficiency, aligning with ongoing efforts to optimise deep-ocean instrumentation setups.
The experience of exchanging ideas and learning from diverse perspectives in the oceanographic communities such as GO-SHIP and EuroGO-SHIP have transformed the way data is collected at sea. Adopting innovative solutions not only helps to resolve persistent technical challenges, but also ensures that our research objectives to collect high-quality and uninterrupted datasets are achieved.
By rethinking established methods and embracing new techniques, oceanographers can address critical equipment challenges, reduce operational risks, make observation missions more efficient, and enhance scientific outcomes.
About the author
Name: Caroline Cusack
Work Package: WP 2, 3, 4, 5
Organisation: Marine Institute, Ireland
Name: Anthony English
Ship Instrument Technician
P&O Maritime Service
What is a CTD rosette system?
CTD: The CTD is an essential tool for oceanographers, used to measure the conductivity (measures electrical conductivity to estimate salinity), temperature, and depth in the water that the sensor is measuring from (water depth and pressure), often combined with additional sensors to capture oxygen levels, fluorescence, turbidity, photosynthetically active radiation (PAR) and pH.
CTD rosette showing the white painted steel circular frame, the grey Niskin cylindrical bottles, the yellow and blue LADCPs and associated orange battery pack. The CTD sensors are just visible behind the LADCP sensor.
Rosette frame: A stainless steel (or titanium) cylindrical frame designed to protect sensitive instruments during deployment and recovery. The CTD sensors and cylindrical water sampling bottles are mounted around this metal frame.
Water sampling bottles: Water bottles (e.g. Niskin) are used to collect water samples at different water depths. The bottles are equipped with caps at both ends that are closed electronically via the CTD system bottle trigger mechanism at selected depths in the water column allowing the capture of discrete depth water samples for chemical and biological analysis.
Winch and conducting cable: The winch system deploys and retrieves the CTD rosette with a conductive cable that allows data transmission in real time from the CTD sensors to the shipboard deck unit and computer.
What is an LADCP?
A lowered Acoustic Doppler Current Profiler (LADCP) is a device used to measure the speed and direction of water currents at different depths in the ocean. It operates by emitting short bursts of sound waves at a specific frequency, which bounce off particles suspended in the water, and the Doppler shift in the frequency of the returning sound waves is used to calculate the velocity of the water and the travel time is used to calculate the depth of the reflected signal. The LADCP is mounted on the CTD rosette and lowered from the sea surface to ~10 m off the seabed collecting high-resolution water current data during the water column profile. LADCPs are used to study ocean circulation, mixing, and transport processes, supporting environmental monitoring and climate change research activities.
Yellow and blue coloured downward facing LADCP and associated orange pressure cased battery. To the right are the CTD sensors and just visible above are the opened grey Niskin bottles.
The LADCP is mounted on a CTD rosette system to measure water column velocity profiles during deployments. The setup typically includes one or two LADCP units, with a downward-facing profiler mounted at the bottom of the rosette frame and sometimes an upward-facing profiler added to improve coverage and data resolution. External battery packs, typically housed in pressure-resistant casings, are securely mounted to the frame to power the LADCP during operation. These batteries are positioned to minimise interference with the water flow and the CTD sensors, ensuring accurate velocity measurements while maintaining the rosette’s balance and functionality.
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