Monterey Accelerated Research System Research Articles

Development of a deep-sea in-situ anion analyzer for marine biogeochemical cycle observation

A novel deep-sea in-situ anion analyzer (DIAA) is proposed and developed for long-term and continuous observation of marine biogeochemistry and ecology. The DIAA is designed to analyze the concentrations of various anions in seawater, such as F−, Cl−, Br−, NO3−, SO42−, and PO43−, based on ion chromatography (IC) technology. The DIAA consists of a control circuit module, a conductivity signal acquisition module, and a flow analysis module. The control circuit module is installed in a sealed pressure-resistant vessel, while the conductivity signal acquisition module and the flow analysis module are housed in a sealed pressure-balanced vessel. The two vessels are capable of functioning at a water depth of up to 4000 m. A seawater in-situ dilution device is designed to solve the issue that the concentrations of Cl− and SO42− in seawater exceeds the IC detection limit. Moreover, an in-situ calibration device enables the DIAA to operate subsea for a long time without recovery. In addition, the DIAA can diagnose and isolate faults automatically. The operation status can be monitored remotely on the shore, and the scientific data can be acquired in real-time. During the sea trial, the DIAA was connected to Monterey Accelerated Research System (MARS) seafloor observatory at a water depth of approximately 900m and operated for six months successfully. The measurement accuracy and the long-term stability of the instrumentation have been verified.

Potential of K-means clustering for preliminary labeling of acoustic data samples

Labeling data for use in supervised learning algorithms can be a long and arduous process, especially for large datasets. This work explores if an unsupervised k-means clustering algorithm can act as a tool to efficiently obtain preliminary labels for large acoustic datasets. This approach is tested on vector sensor data from Monterey Accelerated Research System (MARS). To determine the optimal number of clusters in the k-means algorithm, the silhouette method is used. The clustering of different types of input data will be compared. Specifically, time average spectra from the pressure sensor, the acoustic particle velocity, and intensity will be considered. In addition, the results of clustering data from different times of day and months over a two-year period will be compared. Results of the clustering will be presented along with an assessment of the potential for using a k-means clustering as a preliminary labeling tool for large acoustic sets. [Undergraduate research funded by the College of Physical and Mathematical Sciences as Brigham Young University.]

A deep-sea in-situ chemical laboratory for cabled seafloor observatories

A deep-sea in-situ chemical laboratory (DICL) is proposed for new insight into ocean chemical evolution. The DICL integrates a deep-sea in-situ anion analyzer (DIAA) and several chemical sensors connected to cabled seafloor observatories via a science instrument interface module (SIIM). It can measure the concentrations of seawater anions (e.g., Fˉ, Clˉ, Brˉ, NO3ˉ, SO4 2ˉ, PO4 3ˉ), chlorophyll-a, dissolved oxygen, and methane, as well as pH value. The system operation status can be monitored remotely on the shore, and the science data can be acquired in real-time. After water pressure tests and shallow sea trials, the DICL was tested in the Monterey Accelerated Research System (MARS) deep-sea observatory and collected high-resolution time-series chemical parameters. The experimental results demonstrated that the DICL's mechatronics integration design is reasonable and feasible.

Model for underwater noise due to bubble clouds and comparison with observations from Monterey accelerated research system observatory

Empirical models for underwater noise spectrum from bubbles suggest a general increase by 5 dB for every doubling of wind speed. However, at wind speeds greater than 10 m/s and frequencies higher than 10 kHz, observations report a decrease in noise with increase in wind. This is due to the formation of bubble clouds, which radiate sound, but also attenuate the intensities because of the air contained within them. The bubble clouds occur in certain shapes called α, β, and γ plumes, which evolve during the various stages of wave-breaking. There are yet no quantitative underwater noise models that combine the nature of these clouds, with their acoustics. This paper builds the model in two steps. First, inputs such as wind speed and wave height are used to approximate the clouds as spheres, with respective number of bubbles of each radius and mean spacing between the clouds. Second, this approximate model is then used to predict the radiated sound. To test the model, predictions are setup for comparison with measured noise during high winds around Monterey, California. To input relevant environment parameters to the model, the work uses measurements of wind-velocities, and wave-heights, measured on-site. For acoustic recordings, the work uses hydrophone from the Monterey Accelerated Research System (MARS) cabled observatory.

Interpreting phase shifts of basin-scale arrivals observed in the North Pacific

The 75 Hz Kauai Beacon is well situated for observing the North Pacific Ocean acoustically. Somewhat conveniently, three ocean observing networks, with acoustic receivers located within the deep sound channel: two observatories 4 mm to the East (RCO: Regional Cabled Observatory and MARS: Monterey Accelerated Research System), and the International Monitoring Station at Wake Island 3.5mm to the West. During April–June of 2023, the Beacon transmitted a 37.5 Hz bandwidth m-sequence signal several times a day every 4 days. Upon processing, a persistent arrival structure is identified, which for which each arrival exhibits a unique, yet relatively steady phase over the course of a 20-min transmission. Leveraging acoustic propagation models to better understand the effect of the fluctuating ocean environment, we address the stability of the arrivals over the 20-min transmissions, from hour to hour, and over the course of the 3-month study. This includes examination of potential causes for the slow-phase shifts observed at all of the stations, and how it relates to Doppler. This talk concludes with a discussion on the future utility and research topics of interest, including long-range geo-positioning (underwater GPS), communications, thermometry, and tomography.

Basin scale propagation modeling of MLS signals from the Kauai Beacon source

Long distance underwater acoustic propagation is of interest for a variety of applications including underwater navigation, yet modeling such propagation is challenging due to the large degree of environmental uncertainty. In this presentation, the propagation of 75Hz center frequency maximum length sequence (MLS) signals emitted from a submerged source near Kauai and received at various sites throughout the Pacific Ocean Basin is modeled with the Bellhop ray tracing [1] and Monterey-Newport Parabolic Equation [2] models. Sites such as the Monterey Accelerated Research System (MARS) observatory and the Comprehensive Nuclear Test Ban Organization (CTBTO) hydroacoustic monitoring station near Wake Island are included in the discussion. The range-dependent environment is based on historical profiles from the World Ocean Atlas database and reanalysis data from the hybrid coordinate ocean model (HYCOM) [3]. Bathymetry profiles along the axis of propagation are interpolated from the General Bathymetric Chart of the Oceans (GEBCO) 2021 database [4]. Simulated broadband channel impulse responses transmission loss levels in the modeled environment are compared to selected receptions of the signal at the hydrophone sites. Additionally, fluctuations of the modeled transmission loss in the presence of an internal wave model [5] are discussed.

Basin-scale propagation modeling of MLS signals between Kauai and Monterey

Long distance underwater acoustic propagation is of interest for a variety of applications including underwater navigation, yet modeling such propagation is challenging due to the large degree of environmental uncertainty. In this presentation, the propagation of 75 Hz center frequency maximum length sequence (MLS) signals emitted from a submerged source near Kauai and received at the Monterey Accelerated Research System (MARS) observatory are modeled with the Bellhop ray tracing and the Monterey-Newport Parabolic Equation (MNPE) models. The range-dependent sound speed environment is based on historical profiles from the World Ocean Atlas database and reanalysis data from the hybrid coordinate ocean model (HYCOM). Bathymetry profiles along the axis of propagation are interpolated from the General Bathymetric Chart of the Oceans (GEBCO) 2021 database and the Naval Oceanographic Office Digital Bathymetric Data Base Variable Resolution (DBDB-V) data product. Simulated channel impulse responses are compared to observations for transmission loss and signal coherence.

Long time-series analysis from a directional acoustic sensor near Monterey Bay

A reduction in commercial shipping was reported during the first half of 2020 in response to the COVID-19 pandemic. The goal of this analysis is to determine if this impact on shipping resulted in a corresponding reduction in low-frequency ambient noise levels off the coast of Monterey Bay, California. Data presented here was collected on a Naval Postgraduate School directional acoustic sensor deployed on the Monterey Accelerated Research System’s cabled observatory, managed by the Monterey Bay Aquarium Research Institute. The directional acoustic sensor was developed by GeoSpectrum Technologies, Inc for integration onto the observatory system, and was initially installed in February, 2019. Since then, the data has been continuously streaming to a server at the Naval Postgraduate School for subsequent processing. In this work, long time-series analysis is performed to compare year-to-year statistics of month-long data sets through the end of January, 2021. Spectral probability densities are computed for each month over the 1/3 octave band for both amplitude and direction. Annual variations of the 50th percentile statistics are evaluated to determine if the shipping reduction due to COVID-19 is a distinguishable feature in the data.

Persistent Sampling of Vertically Migrating Biological Layers by an Autonomous Underwater Vehicle Within the Beam of a Seabed-Mounted Echosounder

Many pelagic animals, such as krill, lanternfish, and cephalopods, migrate to deep water at dawn to avoid visual predators during daylight hours and move up toward the sea surface at dusk to search for food. This behavior is termed “diel vertical migration.” Migrating animals graze on phytoplankton or zooplankton and in turn serve as food for higher trophic levels, hence providing a key mechanism for carbon export via this migration. These animals are often observed as sound-scattering layers by echosounders, but the animals causing the acoustic scattering are difficult to identify using acoustics alone. In a spring 2019 experiment in Monterey Bay, we deployed autonomous underwater and surface vehicles over a seabed-mounted upward-looking echosounder to collect environmental DNA (eDNA) with the goal of identifying the vertically migrating animals. The echosounder was installed at 890-m depth on the Monterey Accelerated Research System (MARS) seabed cabled ocean observatory, providing real-time data of acoustic backscatter from the full water column. One long-range autonomous underwater vehicle (LRAUV) carrying a Third-Generation Environmental Sample Processor (3G-ESP) acquired water samples from a sequence of layers from near surface down to ~ 290 m as directed by the distribution of animals observed by the echosounder. During the sampling of each layer, the LRAUV ran on a tight circular yo-yo trajectory directly above the echosounder, remaining in its beam by acoustically tracking a station-keeping Wave Glider on the sea surface marking the echosounder's latitude and longitude. The persistent and simultaneous acoustic observation and eDNA acquisition enables identification of animals at precise locations to better understand their vertical migration behaviors. We present the methods and the system performance in the experiment.

Marine observations with optics

Seismology Placing sensors on the seafloor is difficult, but a sensor network has huge potential for observing processes occurring both below and above the seafloor. Lindsey et al. measured acoustic vibrations collected by attaching a laser to the Monterey Accelerated Research System's subsea optical fiber during a maintenance period (see the Perspective by Jousset). Acoustic waves were monitored by changes in laser light along the cable. The observations from just a few days allowed mapping of an unknown fault system and detection of several dynamic processes in the water column above. Science , this issue p. [1103][1]; see also p. [1076][2] [1]: /lookup/doi/10.1126/science.aay5881 [2]: /lookup/doi/10.1126/science.aaz7750

Illuminating seafloor faults and ocean dynamics with dark fiber distributed acoustic sensing.

Distributed fiber-optic sensing technology coupled to existing subsea cables (dark fiber) allows observation of ocean and solid earth phenomena. We used an optical fiber from the cable supporting the Monterey Accelerated Research System during a 4-day maintenance period with a distributed acoustic sensing (DAS) instrument operating onshore, creating a ~10,000-component, 20-kilometer-long seismic array. Recordings of a minor earthquake wavefield identified multiple submarine fault zones. Ambient noise was dominated by shoaling ocean surface waves but also contained observations of in situ secondary microseism generation, post-low-tide bores, storm-induced sediment transport, infragravity waves, and breaking internal waves. DAS amplitudes in the microseism band tracked sea-state dynamics during a storm cycle in the northern Pacific. These observations highlight this method's potential for marine geophysics.

Continuous monitoring and classification of odontocete echolocation clicks from an ocean observatory

Passive acoustic monitoring is a valuable technique for detecting the presence and inferring the activities of odontocetes, but is often limited by power and data-storage constraints of self-contained recorders. Since July 2015, a broadband (10 Hz–128 kHz) hydrophone has been recording continuously at the Monterey Accelerated Research System (MARS), a cabled observatory in Monterey Bay, California, USA. This acoustic record is notable for its combination of duration, bandwidth, and completeness. An automated detector identified more than 200 million unique clicks in this dataset, and extracted a variety of time-domain, spectral, and cepstral features from each click. Depending on the criteria used, clustering algorithms identified 4-8 click classes consistent with those of local odontocete species, including dolphins and beaked whales. Clicking rates were highly variable, with a median of 0.2 clicks minute-1 and a mean of 165 (± 130 standard error) clicks minute-1. Echolocation activity was 1-2 orders of magnitude higher at night than during daytime, and was seasonally higher in fall and winter. Prior work has shown that mesopelagic sound-scattering layers in Monterey Bay are densest at these times of year, suggesting higher availability of prey. Continuous passive monitoring has great potential to improve our understanding of these species’ foraging ecology, especially when integrated with environmental measurements and active acoustic measurements of their prey fields.Passive acoustic monitoring is a valuable technique for detecting the presence and inferring the activities of odontocetes, but is often limited by power and data-storage constraints of self-contained recorders. Since July 2015, a broadband (10 Hz–128 kHz) hydrophone has been recording continuously at the Monterey Accelerated Research System (MARS), a cabled observatory in Monterey Bay, California, USA. This acoustic record is notable for its combination of duration, bandwidth, and completeness. An automated detector identified more than 200 million unique clicks in this dataset, and extracted a variety of time-domain, spectral, and cepstral features from each click. Depending on the criteria used, clustering algorithms identified 4-8 click classes consistent with those of local odontocete species, including dolphins and beaked whales. Clicking rates were highly variable, with a median of 0.2 clicks minute-1 and a mean of 165 (± 130 standard error) clicks minute-1. Echolocation activity was 1-2 orders of ...

Detection and classification of whales calls using band-limited energy detection and transfer learning

The Monterey Bay Aquarium Research Institute has been recording since July 2015 almost continuously at the Monterey Accelerated Research System (MARS) cabled observatory in Monterey Bay, California, USA. This long-term recording contains thousands of whale calls to help further our understanding of interannual, seasonal, and diel patterns. Here we report on our highly accurate detection and classification method developed to classify blue whale A, B, and D calls and Fin whale 20 Hz pulses. The foundation of the method is a computationally efficient and tuned decimation filter to convert the broadband hydrophone 128 kHz signal to 2 kHz which preserves the low-frequency signal and avoids any high-frequency aliasing. Detection is done using a band-limited-energy-detection filter to find potential calls in the decimated data. Spectrograms are then generated for potential calls and enhanced with local image normalization followed by smoothing by convolving in either time or frequency. Classification is done using the Google Inception v3 model with a transfer learning method. Overall, false positive rates are very low despite variability in whale call shape and background noise.

Independent Benthic Microbial Fuel Cells Powering Sensors and Acoustic Communications with the MARS Underwater Observatory

AbstractMost oceanographic instruments on the seafloor have no connections with the surface and therefore have to run on batteries and store data until recovery. To demonstrate a developing technology, sensors and acoustic modems were powered with energy harvested from the seafloor, and data were relayed acoustically in near–real time to the Monterey Accelerated Research System (MARS) observatory in Monterey Bay, California, and to surface research vessels. MARS is a cabled observatory in deep water (~890 m) at the edge of Monterey Canyon. An acoustic modem was attached to the MARS node and configured to send out commands to, and relay data received from, remote modems. Two benthic microbial fuel cells (BMFCs) positioned approximately 0.5 km away from MARS supplied power to the remote modems and sensors. At their peak performance, these BMFCs produced continuous power densities of ~35 mW m−2 (footprint area). The modems utilized in this study contained an integrated power management platform (PMP) designed to manage and store the electrical energy generated by each BMFC and to record BMFC performance parameters and sensor data on an hourly basis. Temperature and either oxygen or conductivity sensors were chosen because of their common use and environmental relevance. Acoustically transmitted data records show that the BMFCs renewed energy stores and that the oceanographic sensors measured dissolved oxygen, temperature, and conductivity reliably throughout the operational life of each BMFC system (~6 months). These systems remained in place for more than 12 months.

Design, construction, and operation of an actively controlled deep-sea CO2 enrichment experiment using a cabled observatory system

We describe the design, testing, and performance of an actively controlled deep-sea Free Ocean CO2 Enrichment (dp-FOCE) system for the execution of seafloor experiments relating to the impacts of ocean acidification on natural ecosystems. We used the 880m deep MARS (Monterey Accelerated Research System) cable site offshore Monterey Bay, California for this work, but the Free Ocean CO2 Enrichment (FOCE) system concept is designed to be scalable and can be modified to be used in a wide variety of ocean depths and locations. The main frame is based on a flume design with active thruster control of flow and a central experimental chamber. The unit was allowed to free fall to the seafloor and connected to the cable node by remotely operated vehicle (ROV) manipulation. For operation at depth we designed a liquid CO2 containment reservoir which provided the CO2 enriched working fluid as ambient seawater was drawn through the reservoir beneath the more buoyant liquid CO2. Our design allowed for the significant lag time associated with the hydration of the dissolved CO2 molecule, resulting in an e-folding time, τ, of 97s between fluid injection and pH sensing at the mean local T=4.31±0.14°C and pHT of 7.625±0.011. The system maintained a pH offset of ~0.4 pH units compared to the surrounding ocean for a period of ~1 month. The unit allows for the emplacement of deep-sea animals for testing. We describe the components and software used for system operation and show examples of each. The demonstrated ability for active control of experimental systems opens new possibilities for deep-sea biogeochemical perturbation experiments of several kinds and our developments in open source control systems software and hardware described here are applicable to this end.

Design and Application of a Junction Box for Cabled Ocean Observatories

AbstractCabled ocean observatories enabling large amounts of power and two-way communication bandwidth for underwater experiments are a future approach for studying the oceans. On April 21, 2011, at Monterey Bay, California, USA, a network node composed of a junction box (JBox) and three scientific instruments was deployed at the Monterey Accelerated Research System (MARS) site for a 6-month uninterrupted sea trial. The JBox is a facility that can provide multiple wet-mateable connections for various instruments. Each connection can draw 500 W of power and has 10/100 Mbit/s network communication. The current study presents the design and construction of the JBox with focus on the following aspects: a power distribution system with high reliability; a flexible springloaded mechanical structure for heat dissipation; communication that incorporates various data protocols; and self-protection against faults like over-current, short fault, ground fault, and flooding. The deployment and operation of the JBox is described. The sea trial results show that the technologies and methods applied on the JBox and the deploying approach are applicable and worthy of consideration for long-term cabled ocean observatories.

Development of an In Situ pH Calibrator in Deep Sea Environments

The pH Calibrator is an instrument for in situ calibration and measurement of chemical species (pH) in aqueous fluids at elevated pressure. The calibration device consists of two interactive systems: a data-logging sensor system and an automated fluid de- livery system. The solid-state pH sensor array is sealed in a flow cell to decrease measurement response time. The automated fluid de- livery system consists of a pump and process control valves, which intermittently deliver seawater samples for measurement. Following measurement cycles, the pH buffer solutions are drawn into the sensor cell to perform two-point calibration. Here, we describe the initial steps in its conversion from a battery-powered instrument for short-term application into a unit that can be used to take full advantage of cabled-powered observatories that will soon be coming online at a number of locations in marine environments. Accordingly, we made use of the continuous power supply and TCP/IP network capability intrinsic to the Monterey Accelerated Research System (MARS)-cabled ocean observatory, Monterey Bay, CA, to reconfigure the unit in anticipation of future seafloor deployments. The flow through system has been further optimized to reduce dead volume effects in the calibration process, while the mechanical system can now better tolerate increases in fluid discharge pressure and flow rate for long-term operations. Furthermore, the sensor head is now equipped with a novel valve to enhance operations in hydrothermal diffuse flow environments. To gain full access to the MARS-cabled observatory, the dc-dc power converter module and Ethernet to serial module are integrated to the electronics. The pH Calibrator has passed the wet node simulator tests in a seawater tank at the Monterey Bay Aquarium Research Institute, moving the project closer to fulfilling long-term objectives for marine studies.

Test China Node on Monterey Accelerated Research System (MARS)

Test China Node on Monterey Accelerated Research System (MARS)

Interfacing a scientific echosounder with a cabled ocean observatory.

To demonstrate the utility of adding active acoustics to ocean observatories, an upward‐looking, 38 kHz Simrad EK‐60 echosounder package was connected to the Monterey Accelerated Research System (MARS) Observatory. The Deepwater Echo Integrating Marine Observatory System (DEIMOS) integrated the echosounder with commercial electrical and communications hardware in a glass pressure sphere, all mounted in an ROV‐deployable frame. A cabled connection to the MARS node provided instrument power and real‐time TCP/IP network communications to surface control and display systems. DEIMOS sampled the entire water column (875 m) at 0.2 Hz from February 27, 2009 to August 18, 2010. The instrument collected 50 Mbytes of raw data every 3 h resulting in a total of 167 Gbytes of raw data. Metrics developed to quantify distributions and abundances of pelagic organisms show temporal variability over seasons, diel cycles, and minute‐to‐minute predator‐prey interactions. We will present design goals, deployment challenges, an...

Deep‐sea observatory

The first deep‐sea ocean observatory offshore of the continental United States has begun operating in the waters off central California. The remotely operated Monterey Accelerated Research System (MARS) will allow scientists to monitor the deep sea continuously. Among the first devices to be hooked up to the observatory are instruments to monitor earthquakes, videotape deep‐sea animals, and study the effects of acidification on seafloor animals. “Some day we may look back at the first packets of data streaming in from the MARS observatory as the equivalent of those first words spoken by Alexander Graham Bell: ‘Watson, come here, I need you!’,” commented Marcia McNutt, president and CEO of the Monterey Bay Aquarium Research Institute, which coordinated construction of the observatory. For more information, see http://www.mbari.org/news/news_releases/2008/mars‐live/mars‐live.html.