Underwater gliders for ocean research
TL;DR: Underwater gliders are autonomous vehicles that profile vertically by buoyancy control and move horizontally on wings as mentioned in this paper, and are among the best approaches to achieving subsurface spatial resolution necessary for ocean research.
Abstract: Underwater gliders are autonomous vehicles that profile vertically by buoyancy control and move horizontally on wings. Gliders are reviewed, from their conception by Stommel as an extension of autonomous profiling floats, through their development in 3 models, and including their first deployments singly and in numbers. This paper discusses the basics of glider function as implemented by University of Washington, Seaglider, Scripps Institution of Oceanography, and Webb Research in Slocum. Preliminary results are presented from a recent demonstration project that used a network of gliders off Monterey. A wide range of sensors has already been deployed on gliders, with many under development, and a wider range of future possibilities. Glider networks appear to be among the best approaches to achieving subsurface spatial resolution necessary for ocean research.
Citations
More filters
05 Mar 2007
TL;DR: This paper addresses the design of mobile sensor networks for optimal data collection by using a performance metric, used to derive optimal paths for the network of mobile sensors, to define the optimal data set.
Abstract: This paper addresses the design of mobile sensor networks for optimal data collection. The development is strongly motivated by the application to adaptive ocean sampling for an autonomous ocean observing and prediction system. A performance metric, used to derive optimal paths for the network of mobile sensors, defines the optimal data set as one which minimizes error in a model estimate of the sampled field. Feedback control laws are presented that stably coordinate sensors on structured tracks that have been optimized over a minimal set of parameters. Optimal, closed-loop solutions are computed in a number of low-dimensional cases to illustrate the methodology. Robustness of the performance to the influence of a steady flow field on relatively slow-moving mobile sensors is also explored
920 citations
Cites methods from "Underwater gliders for ocean resear..."
...The data used correspond to the Spray gliders [ 22], [28] and the Slocum gliders [ 13], [28] that patrolled the bay during the summer of 2003 (as plotted in Figures 2 and 3)....
[...]
...A highlight was the simultaneous deployment of more than a dozen, sensor-equipped, autonomous underwater gliders [28], including five Spray gliders operated by Russ Davis of Scripps Institution of Oceanography and up to ten Slocum gliders operated by David Fratantoni of Woods Hole Oceanographic Institution (Figure 1)....
[...]
TL;DR: In this paper, the authors describe a methodology for cooperative control of multiple AUVs based on virtual bodies and artificial potentials (VBAP) which allows for adaptable formation control and can be used for missions such as gradient climbing and feature tracking.
Abstract: Operations with multiple autonomous underwater vehicles (AUVs) have a variety of underwater applications. For example, a coordinated group of vehicles with environmental sensors can perform adaptive ocean sampling at the appropriate spatial and temporal scales. We describe a methodology for cooperative control of multiple vehicles based on virtual bodies and artificial potentials (VBAP). This methodology allows for adaptable formation control and can be used for missions such as gradient climbing and feature tracking in an uncertain environment. We discuss our implementation on a fleet of autonomous underwater gliders and present results from sea trials in Monterey Bay in August, 2003. These at-sea demonstrations were performed as part of the Autonomous Ocean Sampling Network (AOSN) II project
518 citations
TL;DR: The signal processing techniques needed to produce calibrated measurements of terrestrial and aquatic acoustic habitats are reviewed and a supplemental tutorial and template computer codes in matlab and r are included, which give detailed guidance on how to production calibrated spectrograms and statistical analyses of sound levels.
Abstract: Summary 1. Many organisms depend on sound for communication, predator/prey detection and navigation. The acoustic environment can therefore play an important role in ecosystem dynamics and evolution. A growing number of studies are documenting acoustic habitats and their influences on animal development, behaviour, physiology and spatial ecology, which has led to increasing demand for passive acoustic monitoring (PAM) expertise in the life sciences. However, as yet, there has been no synthesis of data processing methods for acoustic habitat monitoring, which presents an unnecessary obstacle to would-be PAM analysts. 2. Here, we review the signal processing techniques needed to produce calibrated measurements of terrestrial and aquatic acoustic habitats. We include a supplemental tutorial and template computer codes in MATLAB and R, which give detailed guidance on how to produce calibrated spectrograms and statistical analyses of sound levels. Key metrics and terminology for the characterisation of biotic, abiotic and anthropogenic sound are covered, and their application to relevant monitoring scenarios is illustrated through example data sets. To inform study design and hardware selection, we also include an up-to-date overview of terrestrial and aquatic PAM instruments. 3. Monitoring of acoustic habitats at large spatiotemporal scales is becoming possible through recent advances in PAM technology. This will enhance our understanding of the role of sound in the spatial ecology of acoustically sensitive species and inform spatial planning to mitigate the rising influence of anthropogenic noise in these ecosystems. As we demonstrate in this work, progress in these areas will depend upon the application of consistent and appropriate PAM methodologies.
329 citations
University of St. Thomas (Minnesota)1, Atlantic Oceanographic and Meteorological Laboratory2, University of Tasmania3, CSIRO Marine and Atmospheric Research4, Cooperative Research Centre5, Silver Spring Networks6, Commonwealth Scientific and Industrial Research Organisation7, Georgia Institute of Technology8, National Center for Atmospheric Research9, University of California, San Diego10, Met Office11, University of Hamburg12, Pacific Marine Environmental Laboratory13, Tohoku University14, Joint Institute for Marine and Atmospheric Research15, Woods Hole Oceanographic Institution16, University of Illinois at Chicago17, University of California, Davis18, University of Buenos Aires19, ENEA20, IFREMER21, California Institute of Technology22, University of California, Irvine23
TL;DR: The evolution of ocean temperature measurement systems is presented with a focus on the development and accuracy of two critical devices in use today (expendable bathythermographs and conductivity-temperature-depth instruments used on Argo floats).
Abstract: The evolution of ocean temperature measurement systems is presented with a focus on the development and accuracy of two critical devices in use today (expendable bathythermographs and conductivity-temperature-depth instruments used on Argo floats). A detailed discussion of the accuracy of these devices and a projection of the future of ocean temperature measurements are provided. The accuracy of ocean temperature measurements is discussed in detail in the context of ocean heat content, Earth's energy imbalance, and thermosteric sea level rise. Up-to-date estimates are provided for these three important quantities. The total energy imbalance at the top of atmosphere is best assessed by taking an inventory of changes in energy storage. The main storage is in the ocean, the latest values of which are presented. Furthermore, despite differences in measurement methods and analysis techniques, multiple studies show that there has been a multidecadal increase in the heat content of both the upper and deep ocean regions, which reflects the impact of anthropogenic warming. With respect to sea level rise, mutually reinforcing information from tide gauges and radar altimetry shows that presently, sea level is rising at approximately 3 mm yr-1 with contributions from both thermal expansion and mass accumulation from ice melt. The latest data for thermal expansion sea level rise are included here and analyzed. Key Points Oceanographic techniques and analysis have improved over many decadesThese improvements allow more accurate Earth-energy balance estimatesUnderstanding of ocean heat content and sea-level rise has also increased ©2013. American Geophysical Union. All Rights Reserved.
315 citations
TL;DR: The field results for the heterogeneous fleet of autonomous underwater gliders that collected data continuously throughout the month-long ASAP field experiment demonstrate an innovative tool for ocean sampling and provide a proof of concept for an important field robotics endeavor that integrates coordinated motion control with adaptive sampling.
Abstract: A full-scale adaptive ocean sampling network was deployed throughout the month-long 2006 Adaptive Sam- pling and Prediction (ASAP) field experiment in Monterey Bay, California. One of the central goals of the field experiment was to test and demonstrate newly developed techniques for coordinated motion control of au- tonomous vehicles carrying environmental sensors to efficiently sample the ocean. We describe the field results for the heterogeneous fleet of autonomous underwater gliders that collected data continuously throughout the month-long experiment. Six of these gliders were coordinated autonomously for 24 days straight using feed- back laws that scale with the number of vehicles. These feedback laws were systematically computed using recently developed methodology to produce desired collective motion patterns, tuned to the spatial and tem- poral scales in the sampled fields for the purpose of reducing statistical uncertainty in field estimates. The implementation was designed to allow for adaptation of coordinated sampling patterns using human-in-the- loop decision making, guided by optimization and prediction tools. The results demonstrate an innovative tool for ocean sampling and provide a proof of concept for an important field robotics endeavor that integrates coordinated motion control with adaptive sampling. C
308 citations
Cites background from "Underwater gliders for ocean resear..."
...…the ASAP experiment the covariance of fluctuations C(R, t, R′, t ′) is assumed to be σ0e − (R,R′)/σ−|t−t ′|/τ , where σ0 = 1, σ = 22 km is the spatial decorrelation length, and τ = 2.2 days the temporal decorrelation length, all based on estimates from previous glider data (Rudnick et al., 2004)....
[...]
...2 days the temporal decorrelation length, all based on estimates from previous glider data (Rudnick et al., 2004)....
[...]
References
More filters
TL;DR: SLOCUM as discussed by the authors is a small gliding AUV of 40 000-km operational range which harvests its propulsive energy from the heat flow between the vehicle engine and the thermal gradient of the temperate and tropical ocean.
Abstract: SLOCUM is a small gliding AUV of 40 000-km operational range which harvests its propulsive energy from the heat flow between the vehicle engine and the thermal gradient of the temperate and tropical ocean. The design of both the glider and the thermal engine are discussed including the design genesis and approach, field trial results, concept strength, and limitations and potential use.
746 citations
TL;DR: In this paper, a small (50-kg, 2-m long) underwater vehicle with operating speeds of 20-30 cm/s and ranges up to 6000 km has been developed and field tested.
Abstract: A small (50-kg, 2-m long) underwater vehicle with operating speeds of 20-30 cm/s and ranges up to 6000 km has been developed and field tested. The vehicle is essentially an autonomous profiling float that uses a buoyancy engine to cycle vertically and wings to glide horizontally while moving up and down. Operational control and data relay is provided by GPS navigation and two-way communication through ORBCOMM low-Earth-orbit satellites. Missions are envisioned with profile measurements repeated at a station or spaced along a transect. The initial instrument complement of temperature, conductivity, and pressure sensors was used to observe internal waves and tides in the Monterey underwater canyon.
720 citations
467 citations
01 Jul 2002
TL;DR: In this article, an in situ ultraviolet spectrophotometer (ISUS) that can operate while submerged to depths of at least 2000m is reported. But, the detection limit is nearly random and significant reductions in detection limit are possible by averaging multiple observations, and the precision, accuracy and stability of the chemical concentrations derived with the ISUS are sufficient for many biogeochemical studies.
Abstract: The design for an in situ ultraviolet spectrophotometer (ISUS) that can operate while submerged to depths of at least 2000 m is reported. We show that the ISUS can be used to make high resolution (∼1/s and 0.5 cm) and long-term (>3 months) measurements of the concentration of nitrate, bisulfide and bromide in seawater using the distinctive, ultraviolet absorption spectra of these chemical species. The precision, accuracy and stability of the chemical concentrations derived with the ISUS are sufficient for many biogeochemical studies. One standard deviation of the nitrate concentration in seawater is ∼0.5 μM and the limit of detection (3 SD) for one observation would be ∼1.5 μM. However, the noise is nearly random and significant reductions in the detection limit are possible by averaging multiple observations. The 95% confidence interval for a 30 s scan is 0.2 μM. Low temperatures appear to produce a bias (∼10% at 400 m depth in the ocean) in the nitrate concentration and in the salinity estimated from the bromide concentration. If an independent estimate of salinity is available, then the bias in nitrate can be eliminated by correcting nitrate concentrations by the same amount that the optical estimate of salinity is in error. The instrument has been deployed on a mooring in the equatorial Pacific for a 6-month period with no apparent degradation in performance during the first 3 months. Measurements of UV spectra at a height of 1 cm over the bottom in a cold seep at 960 m depth demonstrate the capability to detect bisulfide ion within the benthic boundary layer.
304 citations