Overview

At a glance

Unlocking the Gulf Loop Current

The Gulf of Mexico is home to one of the world’s most energetic oceanographic phenomena – the Gulf of Mexico Loop Current. Reaching intensities of between 2 – 4 knots and measurable down to 1,000 m, the Loop Current System (LCS) also regularly sheds Loop Current Eddies (LCE).

The challenge

LCEs are highly energetic anticyclonic (clockwise) rotating rings of warm water, roughly 300 km across and 500 – 1,000 m deep, with current speeds of up to 4 knots. These break away from the extended Loop Current about every 8-9 months and slowly drift west-southwestward towards Texas or Mexico at about 3-5 km per day.

When an LCE forms at the height of hurricane season, it has the potential to fuel rapid intensification of hurricanes. This is what happened in 2005, just before Hurricane Katrina passed over and “bombed” into a Category 5 hurricane.

Warm circulating eddies can break off the LCS into the western, northern and central Gulf. These eddies are so highly energetic that they regularly disrupt oil and gas operations. But, they’re also critical to the Gulf of Mexico’s oceanographic system, including its nutrient and food cycles and, most importantly, hurricane intensity.

Despite 50 years of effort by the scientific community to understand the processes underlying the LCS, its behaviour remains unpredictable. To some extent, this is because of interactions with the deep eddies, which have been difficult to track from measurements near the sea surface. For this reason, a multi-year scientific study has been launched, led by the University of Rhode Island(URI). It includes a major deployment of Sonardyne’s Pressure Inverted Echo Sounders(PIES).

The solution

Following a recommendation by the US National Academies of Sciences, Engineering, and Medicine a long-term, US$ multi-million research program to plug the gaps in understanding and predicting the LCS is now underway.

The initial two-year project comprises an array of 15 URI CPIES, five Sonardyne CPIES and five Bureau of Ocean Management PIES. These are in an array, spaced 60 km apart, at depths down to 3,500 m in the area of the extended LCS. Initially deployed in June 2018, for a nominal two-year study, the units are fitted with batteries that can keep them powered for up to 36 months. This will allow for data gathering continuity in the event of a subsequent expansion of the program.

A core element of this scientific study is the array of seabed-mounted sensors, including Sonardyne’s PIES. PIES were originally developed for the marine seismic industry to measure average sound velocity in the water column. They do this by transmitting a wideband acoustic pulse from their position on the seabed. This pulse is reflected off the sea surface and returns to the seabed where it is detected by the PIES.

Oceanographers, however, use PIES differently. Their goal is to derive important physical data, including the strength and direction of currents. This is based on the principle that there’s a strong correlation between two-way travel time (usually known as tau) and vertical profiles of temperature, salinity and density. As a consequence, where this profile has been derived from historical data, an empirical relationship can be derived, which enables the density profile to be inferred from tau.

At a basic level, a laterally separated pair of PIES will, therefore, provide a vertical profile of velocity, and by deploying an array of PIES, local horizontal velocity and density fields can be mapped over the period of deployment.

URI has pioneered and refined the use of PIES for this purpose. While URI has a long history of developing its own PIES instruments, it decided to use Sonardyne’s PIES, as well as its own. This was primarily because a comparison study off the coast of Oregon* indicated that the Sonardyne PIES could generate similar accuracy data efficiently, potentially enabling longer deployments – and because of their telemetry capability.

Sonardyne’s integrated high-speed (up to 9,000 bps) acoustic telemetry capability also enables remote reconfiguration of the instruments and wireless retrieval of data to surface vessels, without interrupting the bottom pressure record.

These capabilities are based on Sonardyne’s extensive expertise in underwater acoustics, signal processing, hardware design and custom engineering, which URI recognises, have the potential to reinforce future PIES development.

Sonardyne’s expertise was central to reconfiguring a standard PIES as a CPIES (Current PIES) which was needed for this project to allow for near-seabed current data to be harvested alongside the PIES pressure and tau measurements. It also delivers important data on deep eddy currents above the seabed/water interface.

The reconfiguration involved connecting an Aanderaa Doppler current sensor to the PIES, which then served as a battery pack and data logger for the current sensor, deployed 50 m above the PIES on a float. Combining the deep current observations with the deep pressure observations enable data from the array to be referred to a common reference surface.

The results

An interim data retrieval campaign, using acoustic telemetry, was successfully completed in September. While the principal purpose of this was to recover an initial three-month-long data set, one notable feature found in the data was echoes, thought to be from fish, shrimp or squid.

This has been seen in other studies carried out by URI. We believe it is related to the transport of nutrients by deep currents crossing from the deeper to shallower thermocline side around the periphery of the Loop Current or a passing LCE.

The present array will inform planning for a longer-term, 10-year campaign. This could see a substantially expanded array of PIES deployed into Cuban, as well as Mexican and US waters. The aim of this larger array would be to provide near real-time data as input for LCS forecasting models.

Loop Current and LCE forecasts have the potential to benefit a wide range of users, from oil and gas operations and hurricane forecasters to fishing and tourism. Furthermore, improving ocean modelling in the Gulf of Mexico has the potential to provide a standard for improving prediction efforts in other ocean basins also.

What's possible

You need transponders to be tough, reliable and easy to work with. RT 6-3000 meets these requirements.

Part of our range of acoustic releases, RT 6-3000 combines our extensive mechanical design track record and many years of subsea mooring experience with the flexibility of our 6G platform. The result is an enhanced battery life and, perhaps most significantly, compatibility with our Ranger 2 USBL family.

Deploy. Track. Locate. Recover.

With RT 6-3000, you can use your Ranger 2 USBL to deploy, track, locate and command the instrument – removing the need for a separate topside unit.

If you don’t have access to a Ranger 2 USBL, our rugged and lightweight Deck Topside with an over-the-side dunker is all you need to configure and command your RT 6-3000s.

RT 6-3000s are used to anchor oceanographic moorings to the seabed. However, their compact size and compatibility with Ranger 2 makes them ideal for incorporation into instrument frames or lowered platforms to enable deployment of sub-system packages. Depth rated to 3,000 m, the maximum slant range for operation is dependent on the noise environment and topside used, but ranges to 4,500 m are achievable.

A battery disconnect fob is located on the transducer and uses an internal magnetic switch to electronically disconnect the battery when not in use. This means you don’t have to open the unit to manually disconnect the battery, saving time and reducing the risk of incorrect re-assembly.

Standard features include a Working Load Limit (WLL) of 1,275 kg (at 4:1) and the same trusted spring-assisted release mechanism used on thousands of Sonardyne transponders globally for many years. RT 6-3000 is compatible with our standard tandem and high-load release frames for scenarios requiring a higher WLL.

Speak to us about your requirements as custom frames are also an option.

Entry level – next level

What's possible

The RT 6-1000 is the versatile acoustic release transponder for your subsea operations. It can be commanded from multiple sources, including the Deck Topside, an Android app, or any Ranger 2 USBL system. This flexibility allows you to easily deploy, track, locate and retrieve your seabed equipment and ocean sensors.

One of the key advantages of the RT 6-1000 is its depth rating of 1,000 metres and weight load limit of 150 kg. This depth and payload capacity make it an ideal choice for scientists, surveyors, and military personnel who require a reliable and enduring solution for their underwater applications.

The RT 6-1000 is compatible with Sonardyne’s Ranger 2 USBL tracking systems, which are widely used on survey vessels around the world. This integration allows for seamless deployment, tracking, and retrieval of your equipment. No access to Ranger 2? No problem, the RT 6-1000’s NFC capability enables setup and control via its Android app or a dedicated Deck Topside unit.

Deploy. Track. Locate. Recover

At a glance

• The reliable choice to deploy, leave and recover seafloor equipment and sensors
• 1,000 metre depth rating; twice that of similar low-cost acoustic release transponders
• Tested, loaded, commanded and released using Deck Topside
• Also works with any Ranger 2 USBL to track it and activate it
• >13-month battery life means less time servicing it and more time using it
• 150 kg Working Load Limit to support your sensors and instruments
• Optional rope canister for heavy lifting

The RT 6-1000 offers impressive endurance, with a battery life of up to 13 months, making it well-suited for long-term deployments and year-long surveys. Its screw-off release mechanism ensures reliable recovery of the transponder and your equipment.

An optional rope canister attachment allows you to quickly and easily raise items left on the seabed, such as tools, cables and salvage. The canister deploys a high-strength rope as the transponder ascends, providing a convenient means of retrieval.

Unlocking subsea secrets with PIES

Imagine the possibilities

Boost your operations: Make informed decisions with a deeper understanding of ocean currents and seismic activity.

Save time and money: Deploy PIES for up to five years, reduce personnel costs and environmental impact through unmanned data retrieval.

Uncover hidden insights: Combine PIES data with other geophysical measurements for a comprehensive view of the ocean floor.

How PIES works for you

PIES is designed to seamlessly integrate into your system:

• Easy to use: Simple setup and configuration, with flexible ping rates to match your needs.
• Reliable data: Consistent, accurate measurements for months or even years.
• Versatile retrieval: Access data when you want it, remotely, mid-operation, via unmanned vehicles or by traditional end of mission retrieval methods.
• Comprehensive insights: Developed for marine seismic and ocean science applications.

Why invest in PIES

• Suitable for environmental surveys / ocean currents monitoring / site survey and characterisation
• Harvest data using ROV, AUV, USV or surface vessel
• Integrated acoustic release for easy recovery
• Depth ratings to 6,000 m
• Choice of form factor to suit your operations

Overview

Acoustic release transponders are a vital piece of ocean equipment – relied upon by energy, defence and science users to moor valuable equipment strings for years at a time, and when commanded to do so, reliably return equipment and logged data to the surface.

Transponders need to be tough, reliable and easy to work with. RT 6-6000 meets these requirements.

Part of our new range of acoustic releases, RT 6-6000 combines the extensive mechanical design track record of our renowned ORTs and DORTs with the flexibility of our 6G platform, resulting in enhanced battery life and perhaps most significantly, compatibility with our Ranger 2 USBL family

With RT 6-6000, you can use your vessel’s Ranger 2 USBL to deploy, track, locate and command the instrument – removing the need for a separate topside unit. If you don’t have access to a Ranger 2 USBL, our rugged and lightweight Deck Topside with an over-the-side dunker is all you need to both configure and command RT 6-6000s.

At a glance

• Tested, loaded, deployed and released using Deck Topside
• Also works with Sonardyne Ranger 2 USBL to deploy, track and command in very deep water
• Highly reliable release mechanism design and thousands are in service globally
• Working Load Limit 1,275 kg (4:1)
• Depth rated to 6,000 m
• External battery disconnect to maximise battery life with no need to open unit
• Compact and rugged design

RT 6-6000s are most commonly used to anchor oceanographic moorings to the seabed. However, their compact size and compatibility with Ranger 2 makes them ideal for incorporation into instrument frames or lowered platforms to enable deployment of sub-system packages.

Standard features include a Working Load Limit of 1,275 kg (at 4:1) and a spring-assisted release mechanism. RT 6-6000 is compatible with our standard tandem and high-load release frames for scenarios requiring a higher WLL. Speak to us about your requirements as custom frames are also an option.

A battery disconnect fob is located on the transducer and uses an internal magnetic switch to electronically disconnect the battery when not in use. This means you do not have to open the unit to manually disconnect the battery, saving time and reducing the risk of incorrect re-assembly.

RT 6-6000s use the same trusted spring-assisted release mechanism that has been in service for many years and used on thousands of Sonardyne transponders globally.