The 2024 deployment

In 2024, funded by the US National Academies of Science, Engineering, and Medicine Gulf Research Programme and led by a team of scientists from the University of Rhode Island, five Sonardyne Origin 65 units were deployed alongside the original Sonardyne CPIES in the Gulf of Mexico (depth range of 1,800 – 3,200 m) for an initial 18-month measurement campaign.

Both the Origin 65s and CPIES have integrated acoustic modems enabling high-speed (up to 9,000 bps) acoustic telemetry to support wireless retrieval of data by an uncrewed surface vessel (USV) in addition to remote control of the instruments.

Despite similar telemetry capability, the volume of data generated by Origin 65 compared to CPIES is much greater, and therefore limited acoustic bandwidth presents a challenge when looking to transfer this substantial data via acoustic telemetry.

This is where Origin 65’s Edge onboard data processing capability comes into play to condense the bulky raw data into small packets of actionable information, easily exportable via the acoustic modem.

The five Origin 65 units were deployed with an Edge application (app) installed to perform combined onboard processing of the ADCP and PIES data. More specifically, the Edge app implemented a custom algorithm that produced an hourly compact (24 bytes) binary output containing a timestamp, the mean current speed and bearing in six depth-bins above the bottom, plus the mean of the PIES results.

The beauty of the onboard data processing was apparent during planned USV visits, where it took less than 20 minutes to acoustically harvest more than two months’ worth of data

An assessment was conducted whereby the integrated acoustic release on one of the Origin 65 instruments was triggered after 66 days of deployment to allow recovery (Figure 1) of the device and complete data download for a thorough evaluation. This instrument was located in a water depth of 2,142 m.

Figure 1: Retrieval of the Origin 65 aboard the R/V Pelican.

Pies

The PIES portion of the Origin 65 performed consistently (Figure 2). Periods of increased scatter in the sound speed measurements are observable, but these are a result of higher ambient noise levels (pretrigger RMS), which correspond to higher sea states (local wave activity is a dominant source of acoustic noise given that in higher sea states the surface return from the PIES chirp is more spread out).

Figure 2: PIES sound speed and ambient noise (pretrigger RMS) measurements for the  deployment. The bottom plot compares ambient noise (pretrigger RMS) to the level of local wave activity using wind speed (as recorded by station Green Canyon 338, 124 km to the WNW of the deployment site) as a proxy for sea state.

ADCP

Velocity data demonstrates expected current behaviour (Figure 3), with velocities much larger in the Eastward and Northward directions than in the upward direction. The lack of significant apparent velocity in the vertical direction indicates that there is no systematic bias in the beam-frame Doppler velocities.

In addition, the observed velocity signals (large blue and red patches) vary on timescales between days and weeks, which is expected.

Of particular interest, it can be seen around 6th June, the prevailing current changed from South-Easterly to North-Westerly over the course of around two days.

This corresponded with a sudden increase in scatter density, thought to be an indication that the seabed was disturbed by the changing current.

Figure 3: Components of the Earth-frame velocities for the 66-day deployment (60-ping ensembles).

Low scatterer concentration in the deep waters (>2000 m) of the Gulf of Mexico reduced the effective profiling range of the Origin 65 from its achieved maximum range of > 800 m. However, with a sufficiently long averaging period it can been seen that the current velocity signal is present for the entire 800 m range of the Origin 65 (Figure 4).

Figure 4: Comparison of 24-hour averages of Eastward current velocity for different altitude bins. Performing increased averaging shows that a consistent current velocity signal is exhibited across the 800 m range of Origin 65.

“Our collaboration with the University of Rhode Island has been instrumental in augmenting our PIES technology in the form of Origin 65, a combined ADCP and PIES, for oceanographic study of geostrophic currents fields like that found in the Gulf of Mexico. We’re delighted to see Origin 65 being applied in this vital study, and by extension, to be able to support research efforts to improve and extend forecasting of the LCS and LCE behaviour with the accuracy desired. We look forward to continuing our relationship with the University of Rhode Island, and to seeing further successful USV data harvests from the Origin 65 units over their deployment period in the Gulf of Mexico.”

Michelle Barnett, Business Development Manager – Ocean Science, Sonardyne

What’s more, evidence of diel plankton migration is apparent with the repeated appearance and disappearance of a scattering layer between 500 m and 800 m height above the bottom. This pattern has a period of roughly 24 hours with the scattering layer clearly visible in daylight hours, as is consistent with the cycle of diel vertical migration observed ubiquitously in aquatic systems throughout the world.

This is nicely demonstrated in cross-correlation data, where values increased to around 80% on a daily cycle in response to the plankton migration (Figure 5). This cross-correlation data helps to indicate the effective maximum range of the system of around 800 m.

Figure 5: An excerpt (4 – 7th June) of unaveraged cross-correlation data for each of the four beams of the Origin 65 demonstrating a clearly observable diel vertical migration pattern. The lower plot represents the local time, with the colour being a function of the local solar altitude.

“This suite of instrumentation and platforms will help refine predictive tools for future applications in the Gulf. Looking ahead, the combination of Sonardyne Origin 65 current profilers and adaptive data-harvesting technology opens the door for long-term deployments in deep water – anywhere in the world. This is very exciting: we could access remote and critically important regions supporting sustained observations and advancing science.”

Professor Kathleen (Kathy) Donohue, Professor of Oceanography, University of Rhode Island

What’s next?

Two successful data harvests by a SeaTrac SP-48 USV equipped with a Sonardyne HPT 7000 L transceiver head have already been conducted. A third data harvest is scheduled for the end of July and the instruments will be recovered in September 2025. Keep an eye on our website and social media for further information about this and the data captured.

If you have an operational challenge for Origin 65, or any other Sonardyne product, please contact us.