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A national glider network for sustained observation of the coastal ocean
Abstract
A national glider network is essential to provide baseline ocean observations to connect the coastal and global ocean, and to address such issues as natural climate variability, ecosystem health, and water quality. The development of gliders is briefly reviewed. Requirements for a national network are presented, and the capabilities of gliders are shown to be suited for the task. The needs of a data management system tuned to gliders are outlined. A workshop to outline a strategy towards creating this network was held in August 2012, with a planning document to follow.
... Since the last decade, Autonomous Underwater Vehicles (AUVs) have becoming popularly used for oceanographic research, e.g., monitoring coastal water [1], observing ocean processes [2], tracking marine mammals [3], and sampling under-ice environment [4]. In data analysis, measurements collected by AUVs must be registered to geo-referenced locations using the position information of the vehicles. ...
... The field work was supported by Marine Institute, Memorial University of Newfoundland. 1 bdeyoung@mun.ca an AUV is usually programmed to surface occasionally for GPS fixes. ...
... Since the last decade, Autonomous Underwater Vehicles (AUVs) have becoming popularly used for oceanographic research, e.g., monitoring coastal water [1], observing ocean processes [2], tracking marine mammals [3], and sampling under-ice environment [4]. In data analysis, measurements collected by AUVs must be registered to geo-referenced locations using the position information of the vehicles. ...
... The field work was supported by Marine Institute, Memorial University of Newfoundland. 1 bdeyoung@mun.ca an AUV is usually programmed to surface occasionally for GPS fixes. ...
An adaptive sensing method is presented to control the pinging interval of a downward-looking sonar on an Autonomous Underwater Vehicle. The goal is to conserve energy via adjusting the pinging rate automatically without reducing the localization accuracy when using terrain-aided navigation (TAN). In this paper, the TAN is implemented using a particle filter and a bias velocity estimator developed based on a Kalman filter. The adaptation on the sonar pinging interval is determined based on the depth variation of local seafloor topography which is quantified using a modified Teager Kaiser energy operator. As a result, more measurements are collected on high relief regions, and less measurements are obtained on relatively flat and smooth regions. We evaluated the adaptive sensing method in a simulated environment and applied it to a field data set. The results show that the adaptive sensing method produces an improved navigational accuracy compared to the missions with fixed sonar pinging rates. In the offline field missions, the energy consumed by the altimeter is reduced to about 30% in the adaptive sensing missions compared to continuously sensing missions where the altimeter is pinging consistently without switching off.
... One possibility is the usage of AUVs called gliders [3,4]. These gliders have a low cruising speed (0.2 to 0.4 m s-1) for long operational periods up to 30 days with low energy consumption achieved by the passive drive concept. ...
The sustained and cost-effective monitoring of the water quality within European coastal areas is of growing importance in view of the upcoming European marine and maritime directives, i.e. the increased industrial use of the marine environment. Such monitoring needs mechanisms/systems to detect the water quality in a large sea area at different depths in real time. This paper presents a system for the automated detection and analysis of water quality parameters using an autonomous underwater vehicle. The analysis of discharge of nitrate into Norwegian fjords near aqua farms is one of the main application fields of this AUV system. As carrier platform the AUV "CWolf" from the Fraunhofer IOSB-AST will be used, which is perfectly suited through its modular payload concept. The mission Task and the integration of the payload unit which includes the sensor module, the scientific and measurement computer in the AUV carrier platform will be described. Few practice oriented information about the software and interface concept, the function of the several software modules and the test platform with the several test levels to test every module will be discussed.
... Due to high efficiency and low cost, UGs or other different type gliders formation researches have attracted more attention, and have been widely used in marine observation [4], search and rescue and other fields [5]. UGs are significant components of ocean observation network applications [6] and integrated ocean observing systems [7]. And collaboration of UGs has great application prospects in large-scale ocean surveys [8]. ...
In this paper, through the application research of underwater gliders, it is found that ocean currents are the major influencing factor in the practical application of gliders. The objective of this study is to solve the path planning of glider formation in time-varying ocean currents. Using the existing glider model, energy consumption model and time-varying ocean current model are established based on the existing data, and a model close to the practical application of glider formation is established as well. The existing RRT algorithms are improved to be OCi-RRT (Ocean current improved RRT) algorithms based on environmental ocean currents. the algorithms are used to solve the path planning problems encountered in the practical application of gliders. Through simulations that are close to the restrictions of reality and the ideal communication state, it indicates that the improved RRT algorithms are suitable for path planning of glider formation in real ocean current environments. Then, a large number of simulation experiments are conducted, the results show that OCi-RRT* can reduce the number of cycles and path length by up to 14%, and the unit energy utilization can increase by up to 25% comparing with the RRT algorithm.
... Three winter (November/December) and two spring (April/May) glider missions were carried out across the SAP between 2015 and 2017, roughly from Bari to Dubrovnik (Figure 1 and Table 1). Teledyne Slocum gliders 2 were used, sampling temperature and salinity down to 1,000 m, using a Sea-Bird pumped payload CTD (GPCTD) with accuracies of ± 0.002 • C and ± 0.002, respectively (Stommel, 1989;Merckelbach et al., 2008;Rudnick et al., 2012). The sensors were calibrated prior to each deployment. ...
The paper aims to describe the preconditioning and observations of exceptionally high salinity values that were observed in summer and autumn of 2017 in the Adriatic. The observations encompassed CTD measurements carried out along the well-surveyed climatological transect in the Middle Adriatic (the Palagruža Sill, 1961–2020), Argo profiling floats and several glider missions, accompanied with satellite altimetry and operational ocean numerical model (Mediterranean Forecasting System) products. Typically, subsurface salinity maximum, with values lower than 39.0, is observed in the Southern Adriatic (usually between 200 and 400 m), related to ingressions of saltier and warmer waters originating in the eastern Mediterranean (Levantine Intermediate Water—LIW). However, seasonally strong inflow of warm and high salinity waters (S > 38.8) has been observed much closer to the surface since spring 2015. The main LIW core deepened at the same time (to 400–700 m). Such double-maxima vertical pattern was eventually disturbed by winter convection at the beginning of 2017, increasing salinities throughout the water column. A new episode of very strong inflow of high salinity waters from the Northern Ionian was observed in late winter and spring of 2017, this time restricted almost to the surface. As most of 2017 was characterized by extremely dry conditions, low riverine inputs and warmer than usual summer over the Adriatic and Northern Ionian, salinity values above the sharp and shallow (15–40 m) thermocline significantly increased. The maximum recorded salinity was 39.26, as measured by the Argo float in the Southern Adriatic. Surface salinity maximum events, but with much lower intensity, have been documented in the past. Both past events and the 2017 event were characterized by (i) concurrence with overall high salinity conditions and cyclonic or transitional phase of the Adriatic-Ionian Bimodal Oscillating System, (ii) very low river discharges preconditioning the events for a year or more, (iii) higher-than-average heat fluxes during most of the summer and early autumn periods, forming a stable warm layer above the thermocline, and (iv) higher-than-average E-P (evaporation minus precipitation) acting on this warm surface layer. Importantly, the 2017 event was also preceded by strong near-surface inflow of very saline waters from the Northern Ionian in early 2017.
... 149 and a Kongsberg Seaglider (https://www.kongsberg.com). Both models can dive down to 1000 150 m and are equipped with a Sea-Bird pumped payload CTD (GPCTD) with accuracies of 151 ±0.002°C, ±0.0003, and ±0.1% of full-scale range for temperature, salinity, and pressure, 152 respectively (Merckelbach et al., 2008;Rudnick et al., 2012;Stommel, 2013). The sensors were 153 calibrated prior to each deployment. ...
Between 2013 and 2016 a drastic change in the vertical salinity structure in the South Adriatic Pit was recorded by Argo floats and ocean gliders. The analysis revealed that high salinity waters characterised 2013 at the surface and intermediate layers, creating the conditions for dense water formation. The year 2014 was instead marked by less saline water, dominant in the first 100 m, that spread in the entire Pit. Heat gain, negative E-P anomalies and abundant river runoff, during that period, maintained this saline stratification for more than a year. This water mass contributed to the dilution of the underlying layer, during the convection event of 2015. The spring transition period, later in 2015, as defined by new saline water placed over the winter formatted water mass and the unperturbed part of the existent salinity profile, in the deeper layers, resulted in a particular vertical structure, characterised by a double salinity maximum. High salinity waters continued to be present at the surface and intermediate layers until the end of 2016, when the strong convection led to a deep mixing, eliminating that structure. The analysis of the available datasets in the South Adriatic Pit, since 1984, linked the presence of these high salinity waters, with the cyclonic phase of the North Ionian Gyre, additionally revealing, also, years of a decreasing trend, during the anticyclonic mode of the Gyre.
... Measurements of the annual production of oxygen Bushinsky and Emerson, 2015] or depletion of nitrate [Plant et al., 2016] using sensors mounted on profiling floats can provide direct estimates of ANCP after the Redfield ratio is used to convert the measured quantity to carbon uptake. While these sensors can be deployed on a variety of other platforms, such as moorings [Shadwick et al., 2015] or gliders [Nicholson et al., 2008], the high operational costs of these platforms [Rudnick et al., 2012] generally preclude large arrays from being deployed [Rudnick, 2016]. The Argo program has demonstrated that very large arrays of profiling floats can be operated at the global scale. ...
Annual nitrate cycles have been measured throughout the pelagic waters of the Southern Ocean, including regions with seasonal ice cover and southern hemisphere subtropical zones. Vertically resolved nitrate measurements were made using in situ ultraviolet spectrophotometer (ISUS) and submersible ultraviolet nitrate analyzer (SUNA) optical nitrate sensors deployed on profiling floats. Thirty-one floats returned 40 complete annual cycles. The mean nitrate profile from the month with the highest winter nitrate minus the mean profile from the month with the lowest nitrate yields the annual nitrate drawdown. This quantity was integrated to 200 m depth and converted to carbon using the Redfield ratio to estimate annual net community production (ANCP) throughout the Southern Ocean south of 30°S. A well-defined, zonal mean distribution is found with highest values (3–4 mol C m⁻² yr⁻¹) from 40 to 50°S. Lowest values are found in the subtropics and in the seasonal ice zone. The area weighted mean was 2.9 mol C m⁻² yr⁻¹ for all regions south of 40°S. Cumulative ANCP south of 50°S is 1.3 Pg C yr⁻¹. This represents about 13% of global ANCP in about 14% of the global ocean area.
... Any difference between the GPS fix and the final dead reckoning position is due to water currents while the gliders are moving underwater. This allows estimations of depth-averaged currents during glider missions (Stommel, 1989;Merchelbach et al., 2008;Rudnick et al., 2012). ...
In the northeastern Adriatic Sea, southwest of the Istrian Peninsula, a persistent thermohaline front is formed, called here the Istrian Front (IF). A Slocum glider was operated across the IF near the entrance to the Kvarner Bay between 24 and 27 February 2015. Three Acoustic Doppler Current Profilers (ADCPs) were also deployed at the entrance of the Kvarner Bay during the same period. The glider crossed twice the IF, which was characterized by a fast reaction to the local wind condition, detecting strong salinity, temperature and density gradients. During the first crossing a strong northeasterly Bora wind was blowing. This resulted in a very sharp and strong thermohaline front, extended vertically in the entire water column. Across the front the SST changed 1.2 °C within a distance of 2.4 km. On the contrary, during the second crossing, about 2 days later, under weaker wind conditions, the IF appeared to be much smoother, inclined and wider and the SST changed 1.2 °C within a distance of 8 km. A strong density gradient was also reported, coincident with the thermohaline IF. From previous observations, mainly experiments in 2003, the IF was known only as a thermohaline front compensated in density. In winter 2015, the density front was strong and well defined, demonstrating a density difference, across it, of about 0.36 kg/m3. The ADCP measurements and the numerical model simulations demonstrated a circulation of cold waters exiting from the Kvarner Bay in the southern part of the entrance, while this outflow was previously reported to taking place in the northern part.
... Submarine (buoyancy-driven) gliders are a type of Autonomous Underwater Vehicle (AUV) that oscillates through the water column and can remain unattended at sea for several weeks to months (Rudnick and Crowley et al., 2012). Gliders carrying appropriate sensors can simultaneously monitor a range of physical and biological parameters, and regular surface communications with satellite allow their movement to be controlled and data to be uploaded in near real-time. ...
Tidal mixing fronts establish during the summer months over shelf-seas, and separate tidally-mixed from stratified water masses. They play an important part in shelf-sea bio-physical processes, including volume transport and facilitation of primary productivity. Frontal hydrodynamics provide the physical necessities for prey aggregations to develop, holding the potential for biodiversity hotspots. However, there is limited knowledge on long-term variability of tidal mixing fronts and its effect on associated ecosystems, due to a lack of adequate datasets. Such information would greatly benefit spatial conservation efforts and improve our understanding of ecosystem dynamics on the continental shelf.
Satellite-derived frontal maps and extensive biological datasets (from 1990-2010) are employed here to investigate spatio-temporal variability of tidal mixing fronts and their significance for shelf-sea biology from zooplankton tomegavertebrates in the Celtic Sea. In addition, this study assesses the suitability and limitations of satellite-derived frontal metrics for quantitative analyses and employs innovative technology (submarine gliders) to fill data gaps in species-environment interactions.
This research provides guidance on the use of frontal metrics in quantitative analysis, such as the need to account for data variability over the years and the careful consideration of the employed frontal metric. This thesis furthermore, represents the first description of long-term temporal variability of tidal mixing fronts on the European shelf and highlights a potential sensitivity to climate change due to positive correlations with rising temperatures. Consequences could include extension of the frontal season and intensification of the frontal density gradient with knock-on effects on associated biota.
The density gradient of tidal mixing fronts was shown to act as a direct distribution boundary for plankton between different shelf-sea domains. Climate-change-driven shifts in the seasonality of these fronts may have a direct impact on dispersal of passive floating organisms, habitat connectivity and adult populations of species with planktonic larvae, including commercially important fish and the benthos. Apart from a barrier function, fronts were also found to be important foraging areas for specialist megavertebrates, which were strongly associated with persistent frontal areas, whereas generalist feeders were not. Tidal mixing fronts represent suitable conservation areas for sensitive species in shelf-seas. The underlying mechanisms leading to bio-aggregations at these sites require more research. High-resolution data, simultaneously collected across multiple trophic levels can be obtained by autonomous robotic fleets in the near future.
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... On the other hand, maybe the lure of gliders is that they are coming of age during a time of increased budget scrutiny for ocean science, given their apparent economy relative to ships. Whatever the causes of this enthusiasm, gliders have been touted for their potential in ocean observation systems for over a decade ( Send et al. 2010; Testor et al. 2010; Rudnick et al. 2012 Rudnick et al. , 2014). A fair assessment is that none of these attempts at establishing a sustained national or international glider observational program have been successful. ...
... Through the miniaturization of such a measurement system and its combination with the flexibility of an Autonomous Underwater Vehicle (AUV), the base for an automatic and closely meshed monitoring of inshore waters, fjords and inland waters will be created. One possibility is the usage of AUVs called gliders [3,4]. These gliders have a low cruising speed (0.2-0.4 m s À1 ) for long operational periods up to 30 days with low energy consumption achieved by the passive drive concept. ...
Recently, underwater vehicles have become low cost, reliable and affordable platforms for performing various underwater tasks. While many aquaculture systems are closed with no harmful output, open net cage fish farms and land-based fish farms can discharge significant amounts of wastewater containing nutrients, chemicals, and pharmaceuticals that impact on the surrounding environment. Although aquaculture development has often occurred outside a regulatory framework, government oversight is increasingly common at both the seafood quality control level, and at baseline initiatives addressing the basic problem of pollution generated by culture operations, e.g. the European marine and maritime directives. This requires regular, sustainable and cost-effective monitoring of the water quality. Such monitoring needs devices to detect the water quality in a large sea area at different depths in real time. This paper presents a concept for a guidance system for a carrier (an autonomous underwater vehicle) of such devices for the automated detection and analysis of water quality parameters.
... Through the miniaturization of such a 57 measurement system and its combination with the flexibility of an Autonomous Underwater Vehicle (AUV), 58 the base for an automatic and closely meshed monitoring of inshore waters, fjords and inland waters will be 59 created. One possibility is the usage of AUVs called gliders [3, 4]. These gliders have a low cruising speed 60 (0.2 to 0.4 ms -1 ) for long operational periods up to 30 days with low energy consumption achieved by the 61 passive drive concept. ...
Recently, underwater vehicles have become low cost, reliable and affordable platforms for performing various underwater tasks. While many aquaculture systems are closed with no harmful output, open net cage fish farms and land-based fish farms can discharge significant amounts of wastewater containing nutrients, chemicals, and pharmaceuticals that impact on the surrounding environment. Although aquaculture development has often occurred outside a regulatory framework, government oversight is increasingly common at both the seafood quality control level, and at baseline initiatives addressing the basic problem of pollution generated by culture operations, e. g. the European marine and maritime directives. This requires regular, sustainable and cost-effective monitoring of the water quality. Such monitoring needs devices to detect the water quality in a large sea area at different depths in real time. This paper presents a concept for a guidance system for a carrier (an autonomous underwater vehicle) of such devices for the automated detection and analysis of water quality parameters.
... Submarine (buoyancy-driven) gliders are a type of Autonomous Underwater Vehicle (AUV) that oscillates through the water column and can remain unattended at sea for several weeks to months (Rudnick and Crowley et al., 2012). Gliders carrying appropriate sensors can simultaneously monitor a range of physical and biological parameters, and regular surface communications with satellite allow their movement to be controlled and data to be uploaded in near real-time. ...
A combination of scientific, economic, technological and policy drivers is behind a recent upsurge in the use of marine autonomous systems (and accompanying miniaturized sensors) for environmental mapping and monitoring. Increased spatial–temporal resolution and coverage of data, at reduced cost, is particularly vital for effective spatial management of highly dynamic and heterogeneous shelf environments. This proof-of-concept study involves integration of a novel combination of sensors onto buoyancy-driven submarine gliders, in order to assess their suitability for ecosystem monitoring in shelf waters at a variety of trophic levels. Two shallow-water Slocum gliders were equipped with CTD and fluorometer to measure physical properties and chlorophyll, respectively. One glider was also equipped with a single-frequency echosounder to collect information on zooplankton and fish distribution. The other glider carried a Passive Acoustic Monitoring system to detect and record cetacean vocalizations, and a passive sampler to detect chemical contaminants in the water column. The two gliders were deployed together off southwest UK in autumn 2013, and targeted a known tidal-mixing front west of the Isles of Scilly. The gliders’ mission took about 40 days, with each glider travelling distances of >1000 km and undertaking >2500 dives to depths of up to 100 m. Controlling glider flight and alignment of the two glider trajectories proved to be particularly challenging due to strong tidal flows. However, the gliders continued to collect data in poor weather when an accompanying research vessel was unable to operate. In addition, all glider sensors generated useful data, with particularly interesting initial results relating to subsurface chlorophyll maxima and numerous fish/cetacean detections within the water column. The broader implications of this study for marine ecosystem monitoring with submarine gliders are discussed.
... One possibility is the usage of AUVs called gliders [3,4]. These gliders have a low cruising speed (0.2 to 0.4 m s-1) for long operational periods up to 30 days with low energy consumption achieved by the passive drive concept. ...
The sustained and cost-effective monitoring of the water quality within European coastal areas is of growing importance in view of the upcoming European marine and maritime directives, i.e. the increased industrial use of the marine environment. Such monitoring needs mechanisms/systems to detect the water quality in a large sea area at different depths in real time. This paper presents a system for the automated detection and analysis of water quality parameters using an autonomous underwater vehicle. The analysis of discharge of nitrate into Norwegian fjords near aqua farms is one of the main application fields of this AUV system. As carrier platform the AUV “CWolf” from the Fraunhofer IOSB-AST will be used, which is perfectly suited through its modular payload concept. The mission task and the integration of the payload unit which includes the sensor module, the scientific and measurement computer in the AUV carrier platform will be described. Few practice oriented information about the software and interface concept, the function of the several software modules and the test platform with the several test levels to test every module will be discussed.
Basic monitoring of the marine environment is crucial for the early warning and assessment of marine hydrometeorological conditions, climate change, and ecosystem disasters. In recent years, many marine environmental monitoring platforms have been established, such as offshore platforms, ships, or sensors placed on specially designed buoys or submerged marine structures. These platforms typically use a variety of sensors to provide high-quality observations, while they are limited by low spatial resolution and high cost during data acquisition. Satellite remote sensing allows monitoring over a larger ocean area; however, it is susceptible to cloud contamination and atmospheric effects that subject the results to large uncertainties. Unmanned vehicles have become more widely used as platforms in marine science and ocean engineering in recent years due to their ease of deployment, mobility, and the low cost involved in data acquisition. Researchers can acquire data according to their schedules and convenience, offering significant improvements over those obtained by traditional platforms. This study presents the state-of-the-art research on available unmanned vehicle observation platforms, including unmanned aerial vehicles (UAVs), underwater gliders (UGs), unmanned surface vehicles (USVs), and unmanned ships (USs), for marine environmental monitoring, and compares them with satellite remote sensing. The recent applications in marine environments have focused on marine biochemical and ecosystem features, marine physical features, marine pollution, and marine aerosols monitoring, and their integration with other products are also analysed. Additionally, the prospects of future ocean observation systems combining unmanned vehicle platforms (UVPs), global and regional autonomous platform networks, and remote sensing data are discussed.
Over the next decade there will be an increase in the development and use of unmanned maritime technologies by the Navy, NOAA, and other commercial and educational entities. There is a need for a cost effective training, test, and evaluation (TT&E) area that can support the demonstration and evaluation of these emerging unmanned maritime systems. The University of Southern Mississippi (USM) has developed the environmental and oceanographic measurement tools, modeling framework, data processing, and visualization products required for the testing and performance evaluation of these maritime systems. Since the performance of these systems and their advanced technologies are coupled to changing ocean and atmospheric environments, their capabilities must be demonstrated, tested, and evaluated in an area with a broad range of oceanographic, acoustic propagation, and environmental variabilities. Mississippi's coastal waters provide these wide range of oceanographic variabilities that are not collectively available in other test areas. Data analysis, modeling, acoustic channel propagation characteristics, and visualization products have been developed to support TT&E activities for both private and academic research partners. Both underwater and atmospheric sensor systems provide data on the controlling environmental processes and their variabilities in the 4-D Ocean Cube test area. Nowcasts and forecasts using high-resolution Navy and NOAA operational models have been integrated into visualization and interactive tools to describe the 4-D Ocean Cube's operational environment.
Executive Summary
There is a critical need to link the terrestrial and ocean systems over time and space scales to address episodic (days) and climatic (years) scale problems facing the scientific and management communities. One element of a strategy to address this need is a sustained sampling protocol that includes the three dimensional ocean from the coasts to the deep ocean. This protocol must include adaptive sampling capabilities to sample episodic events as well as routine and sustained sampling of transects in order to monitor long term changes in the subsurface ocean. These sampling capabilities along the coastal regions of the United States and the Great Lakes would provide critical information to address numerous critical drivers spanning ecosystem and water quality forecasting, hurricane prediction, response to extreme events and man-made disasters, address climate change, and a number of other applications discussed in this report. These drivers identified in numerous national and international reports (JSOST 2007, NOP IP 2013) as well as at a community meeting of glider operators (see Appendix D) comprise the motivation of this report.
This white paper is focused on using the underwater glider as part of a larger comprehensive three dimensional ocean, coastal and Great Lakes observing system. This paper outlines the structure to develop an initial network that includes maintaining existing glider lines, acquiring additional glider lines to fill high priority identified gaps, and improving data management, product development, and data/product delivery. We recognize that there are other autonomous surface and underwater vehicles and we expect they will complement glider capabilities, but this paper focuses on underwater gliders because of the level of maturity of the technology and the community of operators. Tagging of marine animals and fish are also emerging as another capability, and an animal telemetry strategy is also being developed. Both of these efforts are being overseen by the Interagency Ocean Observing Committee (IOOC) and the U.S. Integrated Ocean Observing System (IOOS®) Program Office within NOAA to ensure consistency.
The efforts of the Office of Naval Research, University of Washington, Scripps Institute of Oceanography, Rutgers University and Teledyne Web Research are acknowledged for their early work in gliders that laid the foundation for the United States to be talking about having a network. Today, funding for civilian gliders is provided by National Science Foundation, National Aeronautics and Space Administration, National Oceanic and Atmospheric Administration (NOAA), Environmental Protection Agency, and the U.S. IOOS Program Office. A majority of the gliders are operated by IOOS Regional Associations (RAs) and academic institutions. The High Frequency Radar network evolved similarly and provides an example of the benefits in operational efficiency and in information delivery that were achieved when the network became centrally coordinated as part of IOOS. This paper reflects similar concepts.
In writing this plan a number of questions were raised that merit further discussion. This plan identifies the need for a national steering team to continue the discussion. The questions focus on two main issues (1) should the plan only focus on long endurance lines as opposed to campaigns that support event driven issues and (2) the exact locations of the glider lines. In the end we wrote the plan outlining both long endurance lines as well as the campaigns for event driven issues because the of the versatility of the glider as a platform. But in doing this we are i
not suggesting that gliders can or should be used in every circumstance. Further, the identification of the glider lines are a suggested lay out based on efforts that have already been funded and will be refined in the future.
Over the past 6 years, regional glider operators have completed 33,400 glider days, funded by several federal, state, and local agencies private foundations, and industry. The resulting infrastructure provides a solid framework for a nationwide, operational, glider network; however, many of these assets were obtained via grants and contracts that do not provide ongoing funding for sustained operations and maintenance or data management. With the goal of better modeling and understanding of the dynamic properties of the subsurface Great Lakes and coastal ocean, here defined as the U.S. Exclusive Economic Zone (within 200 nautical miles of shore), this plan describes a way to maximize the benefit of existing investments by providing a mechanism for sustained operation and delivery of these subsurface profile data in a consistent manner to users around the country. The plan also identifies highest priority data gaps that must be filled to achieve a national subsurface sustained monitoring capability that can characterize the coastal waters so that information can meet many of the needs of diverse stakeholders in each region.
The Glider Network is designed to function as a distributed system, with some centralized data management functions that apply consistent data standards and best practices to achieve integration, among various glider observing assets. As the lead federal agency for U.S. IOOS, NOAA will lead the overall plan and coordinate requirements and efforts to ensure consistency between national and regional needs and to align with the national Data Management and Communication objectives.
The plan outlines how IOOS will coordinate data from local and regional efforts across the glider community to deliver a collaborative approach for the design, implementation, and management of the Glider Network, including staffing and training requirements, cost, hardware and server requirements, as well as data management principles. The U.S. IOOS Program Office will collaborate with other NOAA programs, the Inter-agency Subcommittee on Unmanned Systems and the IOOC to identify specific product requirements.
The cost estimate to implement this plan, including operations and maintenance (O&M), acquisition and deployment of new gliders to fill priority data gaps, and acquisition of additional replacement gliders to minimize down time is provided. The capital costs are estimated at 12M, however some of the costs are already covered by existing programs. The operational costs should not exceed $6-8M per year.
The Glider Network requires active participation at the federal and regional levels, with distributed expertise in the regions to operate and maintain the gliders. Data management and operational data delivery would be the responsibility of IOOS with support from the RAs. Technical workshops and a proposed Glider Network Steering Group and Data Team will continue to refine the network and data management requirements over time working with IOOS to ensure the guidelines included in this plan are updated accordingly. Additionally the development of a national glider community will be linked to evolving educational programs focused on developing the glider workforce of the future.
The California Current System (CCS) is expected to experience the
ecological impacts of ocean acidification (OA) earlier than most other
ocean regions because coastal upwelling brings old, CO2-rich
water relatively close to the surface ocean. Historical inorganic carbon
measurements are scarce, so the progression of OA in the CCS is unknown.
We used a multiple linear regression approach to generate empirical
models using oxygen (O2), temperature (T), salinity (S), and
sigma theta (σθ) as proxy variables to
reconstruct pH, carbonate saturation states, carbonate ion concentration
([CO32-]), dissolved inorganic carbon (DIC)
concentration, and total alkalinity (TA) in the southern CCS. The
calibration data included high-quality measurements of carbon, oxygen,
and other hydrographic variables, collected during a cruise from British
Columbia to Baja California in May-June 2007. All resulting empirical
relationships were robust, withr2values >0.92 and low root
mean square errors. Estimated and measured carbon chemistry matched very
well for independent data sets from the CalCOFI and IMECOCAL programs.
Reconstructed CCS pH and saturation states for 2005-2011 reveal a
pronounced seasonal cycle and inter-annual variability in the upper
water column. Deeper in the water column, conditions are stable
throughout the annual cycle, with perennially low pH and saturation
states. Over sub-decadal time scales, these empirical models provide a
valuable tool for reconstructing carbonate chemistry related to ocean
acidification where direct observations are limited. However,
progressive increases in anthropogenic CO2 content of
southern CCS water masses must be carefully addressed to apply the
models over longer time scales.
Underwater gliders are autonomous vehicles that profile vertically by controlling buoyancy and move horizontally on wings. Gliders are reviewed, from their conception by Henry Stommel as an extension of autonomous profiling floats, through their development in three models, and including their first deployments singly and in numbers. The basics of glider function are discussed as implemented by University of Washington in Seaglider, Scripps Institution of Oceanography in Spray, and Webb Research in Slocum. Gliders sample in the archetypical modes of sections and of "virtual moorings." 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 current development, and an even wider range of future possibilities. Glider networks appear to be one of the best approaches to achieving subsurface spatial resolution necessary for ocean research.
The autonomous profiling float has been a revolutionary development in oceanography, enabling global broad-scale ocean observations of temperature, salinity, velocity, and additional variables. The Argo float array applies this new technology to provide unprecedented measurements of the global upper ocean in near real time, with no period of exclusive use. It builds on its predecessors, the upper ocean thermal networks of the 1970s to 1990s—extending the spatial domain and depth range, improving the accuracy, and adding salinity and velocity. Precision satellite measurements of sea surface height, as made by the Jason-1 altimeter, combine with Argo data in a dynamically complementary description of sea level variability and its subsurface causes. The broad-scale Argo float array is a central element in the international infrastructure for ocean research. A comprehensive ocean observing system can be constructed from floats, together with satellite measurements, improved measurements of air-sea fluxes, moored time-series in the tropics and other special locations, shipboard hydrography, and high resolution measurements in fronts, eddies and boundary currents from autonomous gliders. One of the primary objectives of the observing system is to close the oceanic budgets of momentum, heat, and freshwater on seasonal and longer time-scales in order to understand the role of the ocean in the climate system.
Seagliders are small, reusable autonomous underwater vehicles
designed to glide from the ocean surface to a programmed depth and back
while measuring temperature, salinity, depth-averaged current, and other
quantities along a sawtooth trajectory through the water. Their low
hydrodynamic drag and wide pitch control range allow glide slopes in the
range 0.2 to 3. They are designed for missions in a range of several
thousand kilometers and durations of many months. Seagliders are
commanded remotely and report their measurements in near real time via
wireless telemetry. The development and operation of Seagliders and the
results of field trials in Puget Sound are reported
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
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
Fluxes in the California Current System, " in ALPS: Autonomous and Lagrangian Platforms and Sensors
- C Eriksen
ALPS: Autonomous and Lagrangian Platforms and Sensors
- D L Rudnick
- M J Perry