ABSTRACT Scientists from University of South Florida rapidly responded to the Deepwater Horizon o... more ABSTRACT Scientists from University of South Florida rapidly responded to the Deepwater Horizon oil spill incident in the Gulf of Mexico (GOM). A trajectory forecast system using ocean circulation models and satellite imagery was implemented immediately upon spill onset. An ensemble of models was reinitialized daily with satellite imagery inferred oil locations, and virtual particles were then tracked using forecast currents. Subsurface trajectories were also forecast on the basis of continual release from the well site. Timely trajectory forecasts were used to plan scientific surveys and other spill response activities. In addition to the existing moored ADCP and shoreline-based HF radar arrays for ocean circulation monitoring on the West Florida Shelf (WFS), satellite-tracked drifters were deployed in both the GOM Loop Current and the shelf regions, and subsurface gliders and bottom-stationed ocean profilers were manipulated to observe the ocean circulation and to sample the ocean water properties on the WFS. The integrated ocean observing and modeling systems were demonstrated to be very useful in the rapid response.
A national glider network is essential to provide baseline ocean observations to connect the coas... more 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. Planning is underway for a workshop to produce a strategy for a glider network. A document from this workshop will be completed during 2012.
Harmful algal blooms of the dinoflagellate Karenia brevis require an upwelling circulation to man... more Harmful algal blooms of the dinoflagellate Karenia brevis require an upwelling circulation to manifest along the coastline of the West Florida Continental Shelf. Too much upwelling, however, can impede bloom formation by increasing inorganic nutrient levels to the point where faster growing phytoplankton such as diatoms may out-compete the slower growing K. brevis, as occurred in 1998 and 2010. Both 2012 and 2013 experienced persistent upwelling, but only 2012 exhibited a robust harmful algal bloom. Here we examine the subtle differences in the coastal ocean circulation between those two years that led to the disparate bloom evolutions.
Autonomous underwater gliders are becoming important assets of coastal ocean observing systems, b... more Autonomous underwater gliders are becoming important assets of coastal ocean observing systems, but the salinity data may have errors at the depths of thermocline if unpumped CTD sensors are used. Based on the CTD data collected by an autonomous underwater glider on the West Florida Shelf, we examine different salinity corrections, and find that the existing methods successfully adjust the thermal lag effects of a weak thermocline where temperature change is less than 0.7 °C in 3 m of the water column, but fail to calibrate the salinity spikes near a sharp thermocline where temperature change is ∼2 °C within 3 m of the water column. These salinity spikes can be effectively removed by applying a median filter in conjunction with the thermal lag correction methods. Thus, we propose an improved and practical approach of glider salinity error correction, which is especially useful for waters of strong stratification and sharp thermocline.
Autonomous platforms and vehicles are a growing component of the ocean research fleet, producing ... more Autonomous platforms and vehicles are a growing component of the ocean research fleet, producing data sets crucial to our understanding of oceanographic and fishery ecosystem processes. One emerging tool for making these measurements is underwater gliders that autonomously sample the water column for weeks to months at a time. Although originally designed to measure temperature and salinity, underwater gliders can now support a myriad of sensors. For the demonstration project described within, three complementary acoustic technologies were integrated into an underwater glider for mapping fish on the continental shelf: an acoustic telemetry receiver, a passive acoustic monitoring recorder, and a fisheries echosounder. The demonstration project was designed to evaluate the effectiveness of each sensing technology. Sixty-one fish were implanted with acoustic tags near the Gulfstream Natural Gas pipeline in the eastern Gulf of Mexico in advance of planned underwater glider missions. The glider was deployed four times over 12 months, with all three acoustic technologies to traverse the pipeline and surrounding habitat. Glider detections were compared to detections of fish at moored acoustic tag telemetry receivers and passive acoustic recorders co-located at the tagged fish locations. All three technologies identified fish along the targeted hard-bottom pipeline habitat, as well as previously uncharted areas of hard-bottom reef. The results of this study demonstrate the utility of gliders integrated with acoustic sensors as a potential tool to identify areas that merit deeper investigation to assess fish stocks.
This paper presents the first known research to examine sound production by fishes during harmful... more This paper presents the first known research to examine sound production by fishes during harmful algal blooms (HABs). Most fish sound production is species-specific and repetitive, enabling passive acoustic monitoring to identify the distribution and behavior of soniferous species. Autonomous gliders that collect passive acoustic data and environmental data concurrently can be used to establish the oceanographic conditions surrounding sound-producing organisms. Three passive acoustic glider missions were conducted off westcentral Florida in October 2011, and September and October 2012. The deployment period for two missions was dictated by the presence of red tide events with the glider path specifically set to encounter toxic Karenia brevis blooms (a.k.a red tides). Oceanographic conditions measured by the glider were significantly correlated to the variation in sounds from six known or suspected species of fish across the three missions with depth consistently being the most significant factor. At the time and space scales of this study, there was no detectable effect of red tide on sound production. Sounds were still recorded within red tide-affected waters from species with overlapping depth ranges. These results suggest that the fishes studied here did not alter their sound production nor migrate out of red tide-affected areas. Although these results are preliminary because of the limited measurements, the data and methods presented here provide a proof of principle and could serve as protocol for future studies on the effects of algal blooms on the behavior of soniferous fishes. To fully capture the effects of episodic events, we suggest that stationary or
The use of marine offshore benthic habitats by sea turtles is poorly characterized due to the dif... more The use of marine offshore benthic habitats by sea turtles is poorly characterized due to the difficulty of obtaining in situ data. Understanding benthic habitat use that is important to the species' reproduction, foraging, and migrations is critical for guiding management decisions. A towed camera-based assessment survey system (C-BASS) equipped with environmental sensors was used to characterize and assess benthic habitats on the West Florida Shelf (WFS) from 2014 to 2018. During these cruises, sea turtles were opportunistically observed during the surveys, and critical in situ data such as spatiotemporal information, species identification, habitat use, behavior, and environmental data were collected and evaluated. In total, 79 sea turtles were observed during 97 transects of approximately 2700 km of seafloor, which was recorded on 380 h of video. Several sea turtle species were spotted within the WFS, including loggerhead Caretta caretta, Kemp's ridley Lepidochelys kempii, and green turtles Chelonia mydas. These opportunistic sightings revealed an area of high use on the WFS, an anthropogenic structure known as the Gulfstream natural gas pipeline (GSPL). C-BASS survey results suggest that 2 sea turtle species (C. caretta and L. kempii) utilize this artificial structure primarily as a resting area. We emphasize the importance of combining habitat mapping techniques (towed underwater video and multibeam bathymetry/backscatter) with tracking technology to better understand the fine-scale habitat use of sea turtles.
Multi-sensor platforms like buoys and gliders produce one or more readings per sensor on varying,... more Multi-sensor platforms like buoys and gliders produce one or more readings per sensor on varying, discrete time frequencies. The resulting datasets are a matricies with rows containing readings from sensors that reported at a moment in time and NULL for missing readings from sensors that did not. Traditional Relational Database Management Systems (RDBMS) are already well suited for the dense matricies in which NULL values are infrequent. The efficiency of these systems deteriorates though as data becomes more sparse. The University of South Florida College of Marine Science Ocean Technology Group (COT) operates four gliders. Each glider produces dynamic, different sparse datasets. Other data management solutions exist, but they are based on a RDBMS. COT has been investigating an alternative without using and RDBMS. Glider Database Alternative with Mongo (GDAM) is a data management system for gliders built on the MongoDB NoSQL database engine. It is live in production at COT. GDAM is a collection of scripts which parse, process and store real-time glider datasets. Data is parsed as soon as it is transmitted via satellite to our shore-based servers. The system has been tested during two Slocum G1 glider deployments in September and October of 2012. Archival datasets dating back to March of 2009 have also been uploaded into this system. Records are indexed by time, GPS, and depth with the ability to add more indexes as necessary. The paper outlines dataset problems identified using data from COT glider operations in 2012. These problems inform a discussion of design decisions and possible options considering both RDBMS and NoSQL systems. The paper concludes by discussing the current implementation of GDAM.
Underwater gliders have become a critical component of coastal observing systems for measuring wa... more Underwater gliders have become a critical component of coastal observing systems for measuring water column properties. They efficiently sample from the surface to the seafloor or their depth limit collecting essential density variables for weeks to months at a time, providing invaluable information to validate ocean circulation models. However, they can collect much more data, and how those data sets evolve into potential uses is not always fully appreciated. Obviously, if a truck can hold more gear without significantly hurting gas mileage, why not throw more in the back end? As such, over the past decade other sensing equipment has been incorporated into glider payloads such as fluorometers, dissolved oxygen sensors, ADCPs, nutrient sensors, and more. This has allowed expanded use of the same platform without sacrificing their primary design mission of CTD profiles. These additional sensors have enabled new research in fields such as hypoxia dead zones, red tide evolution, and water column heat content. The combination of the various sensors on the same platform will continue to enhance our understanding of the connections between processes that drive our coastal oceans. An additional research area with potential use for gliders is fisheries management. Fish stock assessment depend upon data sets from fishery dependent or independent surveys that are used to set harvest limits. In the eastern Gulf of Mexico, many economically important species are benthic and generally tied to preferred habitat types. State, federal, and academic groups are coordinating efforts to generate habitat-specific population estimates, the first step of which is creating habitat maps to guide visual or trap surveys for the fish. This is typically done by initially creating detailed bathymetric maps of regions and assessing the bottom types through video and other methods to characterize the seafloor structure, habitat and the distribution of biota. However, visually mapping the entire West Florida Shelf is not feasible. Autonomous systems like gliders should be employed as a first-level reconnaissance tool to opportunistically discover reef features or fish hotspots. For the past several years, we’ve attempted to assess fish populations, site fidelity, migration, and other relevant characteristics by integrating passive acoustic recorders, tag telemetry receivers, and fisheries echosounders to a glider tasked with repeated transects within a test region. Our test region has been a large, well-known artificial reef, the Gulfstream Natural Gas Pipeline, a largely linear feature between Tampa Bay and Mobile Bay. Our sampling has been seasonal and focused on the eastern portion of this feature between the 30 and 50m isobaths on the West Florida Shelf (WFS) with a total of five deployments of a single glider completed. Yet, while the linear reef is a wonderful target for the glider, gliders cannot easily traverse a straight line when coastal tidal currents are involved. So, in typical meandering fashion, the glider would spend a lot of time in the region of the pipeline, but not directly over the pipe. We accepted these data as opportunistic and another form of reconnaissance that can inform the design of follow-on surveys. During our efforts, we have used glider-collected acoustic data to identify several “hotspot” locations with high fish densities for which we do not yet have habitat maps nor measures of fish abundance. We subsequently mapped one of these regions with high resolution multibeam echosounder to create detailed bathymetric imagery of the seafloor. This has resulted in discovering previously unknown regions of habitat including seafloor ridges and demersal fish excavated zones known as “grouper holes”. This technological approach, if applied in an observing system capacity of sustained and continuous operations over a region like the West Florida Shelf, will augment existing efforts to identify and describe fish habitat and help provide data sets complimentary to fish stock assessment.
Underwater gliders have been widely used in oceanography for a range of applications. However, un... more Underwater gliders have been widely used in oceanography for a range of applications. However, unpredictable events like shark strikes or remora attachments can lead to abnormal glider behavior or even loss of the instrument. This paper employs an anomaly detection algorithm to assess operational conditions of underwater gliders in the real-world ocean environment. Prompt alerts are provided to glider pilots upon detecting any anomaly, so that they can take control of the glider to prevent further harm. The detection algorithm is applied to multiple datasets collected in real glider deployments led by the University of Georgia's Skidaway Institute of Oceanography (SkIO) and the University of South Florida (USF). In order to demonstrate the algorithm generality, the experimental evaluation is applied to four glider deployment datasets, each highlighting various anomalies happening in different scenes. Specifically, we utilize high resolution datasets only available post-recovery to perform detailed analysis of the anomaly and compare it with pilot logs. Additionally, we simulate the online detection based on the real-time subsets of data transmitted from the glider at the surfacing events. While the real-time data may not contain as much rich information as the post-recovery one, the online detection is of great importance as it allows glider pilots to monitor potential abnormal conditions in real time.
Underwater gliders are widely utilized for ocean sampling, surveillance, and other various oceani... more Underwater gliders are widely utilized for ocean sampling, surveillance, and other various oceanic applications. In the context of complex ocean environments, gliders may yield poor navigation performance due to strong ocean currents, thus requiring substantial human effort during the manual piloting process. To enhance navigation accuracy, we developed a real-time autonomous glider navigation software, named GENIoS Python, which generates waypoints based on flow predictions to assist human piloting. The software is designed to closely check glider status, provide customizable experiment settings, utilize lightweight computing resources, offer stably communicate with dockservers, robustly run for extended operation time, and quantitatively compare flow estimates, which add to its value as an autonomous tool for underwater glider navigation.
This paper utilizes an anomaly detection algorithm to check if underwater gliders are operating n... more This paper utilizes an anomaly detection algorithm to check if underwater gliders are operating normally in the unknown ocean environment. Glider pilots can be warned of the detected glider anomaly in real time, thus taking over the glider appropriately and avoiding further damage to the glider. The adopted algorithm is validated by two valuable sets of data in real glider deployments, the University of South Florida (USF) glider Stella and the Skidaway Institute of Oceanography (SkIO) glider Angus.
The long term goal is development and utilization of a bottom stationed autonomous ocean profiler... more The long term goal is development and utilization of a bottom stationed autonomous ocean profiler. The system is capable of bi-directional satellite communcation via the ORBCOMM system, is user programmable and can store and/or transmit aquired data in near real-time. Deployment of large numbers of BSOP systems, each equipped with a highly capable sensor suite, can be used to synoptically observe marine environments with very low initial capital investment and even lower operations costs.
A GPS-buoy system has been built and is currently undergoing test to measure precise 3D sea floor... more A GPS-buoy system has been built and is currently undergoing test to measure precise 3D sea floor motion in the shallow (less than 200 m) continental shelf environment. Offshore deformation is undersampled in most subduction zones. In Cascadia, the shallow shelf environment constitutes roughly 20%-25% of the offshore area between the coastline and the trench. In the system being tested, the GPS receiver at the top of the buoy is connected to the sea floor through a rigid structure supported by a float. A similar design has been used by INGV (Italy) to measure vertical deformation on the sea floor near the Campi Flegrei caldera. Synthetic analysis shows that by adding a 3-axis digital compass to measure heading and tilt, along with kinematic GPS measurements, position of the anchor can be recovered to an accuracy of several centimeters or better, depending on water depth and GPS baseline length. Synthetic resolution tests show that our ability to detect shallow slow slip events on subduction plate boundaries can be greatly improved by adding offshore GPS-buoy sites
ABSTRACT Scientists from University of South Florida rapidly responded to the Deepwater Horizon o... more ABSTRACT Scientists from University of South Florida rapidly responded to the Deepwater Horizon oil spill incident in the Gulf of Mexico (GOM). A trajectory forecast system using ocean circulation models and satellite imagery was implemented immediately upon spill onset. An ensemble of models was reinitialized daily with satellite imagery inferred oil locations, and virtual particles were then tracked using forecast currents. Subsurface trajectories were also forecast on the basis of continual release from the well site. Timely trajectory forecasts were used to plan scientific surveys and other spill response activities. In addition to the existing moored ADCP and shoreline-based HF radar arrays for ocean circulation monitoring on the West Florida Shelf (WFS), satellite-tracked drifters were deployed in both the GOM Loop Current and the shelf regions, and subsurface gliders and bottom-stationed ocean profilers were manipulated to observe the ocean circulation and to sample the ocean water properties on the WFS. The integrated ocean observing and modeling systems were demonstrated to be very useful in the rapid response.
A national glider network is essential to provide baseline ocean observations to connect the coas... more 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. Planning is underway for a workshop to produce a strategy for a glider network. A document from this workshop will be completed during 2012.
Harmful algal blooms of the dinoflagellate Karenia brevis require an upwelling circulation to man... more Harmful algal blooms of the dinoflagellate Karenia brevis require an upwelling circulation to manifest along the coastline of the West Florida Continental Shelf. Too much upwelling, however, can impede bloom formation by increasing inorganic nutrient levels to the point where faster growing phytoplankton such as diatoms may out-compete the slower growing K. brevis, as occurred in 1998 and 2010. Both 2012 and 2013 experienced persistent upwelling, but only 2012 exhibited a robust harmful algal bloom. Here we examine the subtle differences in the coastal ocean circulation between those two years that led to the disparate bloom evolutions.
Autonomous underwater gliders are becoming important assets of coastal ocean observing systems, b... more Autonomous underwater gliders are becoming important assets of coastal ocean observing systems, but the salinity data may have errors at the depths of thermocline if unpumped CTD sensors are used. Based on the CTD data collected by an autonomous underwater glider on the West Florida Shelf, we examine different salinity corrections, and find that the existing methods successfully adjust the thermal lag effects of a weak thermocline where temperature change is less than 0.7 °C in 3 m of the water column, but fail to calibrate the salinity spikes near a sharp thermocline where temperature change is ∼2 °C within 3 m of the water column. These salinity spikes can be effectively removed by applying a median filter in conjunction with the thermal lag correction methods. Thus, we propose an improved and practical approach of glider salinity error correction, which is especially useful for waters of strong stratification and sharp thermocline.
Autonomous platforms and vehicles are a growing component of the ocean research fleet, producing ... more Autonomous platforms and vehicles are a growing component of the ocean research fleet, producing data sets crucial to our understanding of oceanographic and fishery ecosystem processes. One emerging tool for making these measurements is underwater gliders that autonomously sample the water column for weeks to months at a time. Although originally designed to measure temperature and salinity, underwater gliders can now support a myriad of sensors. For the demonstration project described within, three complementary acoustic technologies were integrated into an underwater glider for mapping fish on the continental shelf: an acoustic telemetry receiver, a passive acoustic monitoring recorder, and a fisheries echosounder. The demonstration project was designed to evaluate the effectiveness of each sensing technology. Sixty-one fish were implanted with acoustic tags near the Gulfstream Natural Gas pipeline in the eastern Gulf of Mexico in advance of planned underwater glider missions. The glider was deployed four times over 12 months, with all three acoustic technologies to traverse the pipeline and surrounding habitat. Glider detections were compared to detections of fish at moored acoustic tag telemetry receivers and passive acoustic recorders co-located at the tagged fish locations. All three technologies identified fish along the targeted hard-bottom pipeline habitat, as well as previously uncharted areas of hard-bottom reef. The results of this study demonstrate the utility of gliders integrated with acoustic sensors as a potential tool to identify areas that merit deeper investigation to assess fish stocks.
This paper presents the first known research to examine sound production by fishes during harmful... more This paper presents the first known research to examine sound production by fishes during harmful algal blooms (HABs). Most fish sound production is species-specific and repetitive, enabling passive acoustic monitoring to identify the distribution and behavior of soniferous species. Autonomous gliders that collect passive acoustic data and environmental data concurrently can be used to establish the oceanographic conditions surrounding sound-producing organisms. Three passive acoustic glider missions were conducted off westcentral Florida in October 2011, and September and October 2012. The deployment period for two missions was dictated by the presence of red tide events with the glider path specifically set to encounter toxic Karenia brevis blooms (a.k.a red tides). Oceanographic conditions measured by the glider were significantly correlated to the variation in sounds from six known or suspected species of fish across the three missions with depth consistently being the most significant factor. At the time and space scales of this study, there was no detectable effect of red tide on sound production. Sounds were still recorded within red tide-affected waters from species with overlapping depth ranges. These results suggest that the fishes studied here did not alter their sound production nor migrate out of red tide-affected areas. Although these results are preliminary because of the limited measurements, the data and methods presented here provide a proof of principle and could serve as protocol for future studies on the effects of algal blooms on the behavior of soniferous fishes. To fully capture the effects of episodic events, we suggest that stationary or
The use of marine offshore benthic habitats by sea turtles is poorly characterized due to the dif... more The use of marine offshore benthic habitats by sea turtles is poorly characterized due to the difficulty of obtaining in situ data. Understanding benthic habitat use that is important to the species' reproduction, foraging, and migrations is critical for guiding management decisions. A towed camera-based assessment survey system (C-BASS) equipped with environmental sensors was used to characterize and assess benthic habitats on the West Florida Shelf (WFS) from 2014 to 2018. During these cruises, sea turtles were opportunistically observed during the surveys, and critical in situ data such as spatiotemporal information, species identification, habitat use, behavior, and environmental data were collected and evaluated. In total, 79 sea turtles were observed during 97 transects of approximately 2700 km of seafloor, which was recorded on 380 h of video. Several sea turtle species were spotted within the WFS, including loggerhead Caretta caretta, Kemp's ridley Lepidochelys kempii, and green turtles Chelonia mydas. These opportunistic sightings revealed an area of high use on the WFS, an anthropogenic structure known as the Gulfstream natural gas pipeline (GSPL). C-BASS survey results suggest that 2 sea turtle species (C. caretta and L. kempii) utilize this artificial structure primarily as a resting area. We emphasize the importance of combining habitat mapping techniques (towed underwater video and multibeam bathymetry/backscatter) with tracking technology to better understand the fine-scale habitat use of sea turtles.
Multi-sensor platforms like buoys and gliders produce one or more readings per sensor on varying,... more Multi-sensor platforms like buoys and gliders produce one or more readings per sensor on varying, discrete time frequencies. The resulting datasets are a matricies with rows containing readings from sensors that reported at a moment in time and NULL for missing readings from sensors that did not. Traditional Relational Database Management Systems (RDBMS) are already well suited for the dense matricies in which NULL values are infrequent. The efficiency of these systems deteriorates though as data becomes more sparse. The University of South Florida College of Marine Science Ocean Technology Group (COT) operates four gliders. Each glider produces dynamic, different sparse datasets. Other data management solutions exist, but they are based on a RDBMS. COT has been investigating an alternative without using and RDBMS. Glider Database Alternative with Mongo (GDAM) is a data management system for gliders built on the MongoDB NoSQL database engine. It is live in production at COT. GDAM is a collection of scripts which parse, process and store real-time glider datasets. Data is parsed as soon as it is transmitted via satellite to our shore-based servers. The system has been tested during two Slocum G1 glider deployments in September and October of 2012. Archival datasets dating back to March of 2009 have also been uploaded into this system. Records are indexed by time, GPS, and depth with the ability to add more indexes as necessary. The paper outlines dataset problems identified using data from COT glider operations in 2012. These problems inform a discussion of design decisions and possible options considering both RDBMS and NoSQL systems. The paper concludes by discussing the current implementation of GDAM.
Underwater gliders have become a critical component of coastal observing systems for measuring wa... more Underwater gliders have become a critical component of coastal observing systems for measuring water column properties. They efficiently sample from the surface to the seafloor or their depth limit collecting essential density variables for weeks to months at a time, providing invaluable information to validate ocean circulation models. However, they can collect much more data, and how those data sets evolve into potential uses is not always fully appreciated. Obviously, if a truck can hold more gear without significantly hurting gas mileage, why not throw more in the back end? As such, over the past decade other sensing equipment has been incorporated into glider payloads such as fluorometers, dissolved oxygen sensors, ADCPs, nutrient sensors, and more. This has allowed expanded use of the same platform without sacrificing their primary design mission of CTD profiles. These additional sensors have enabled new research in fields such as hypoxia dead zones, red tide evolution, and water column heat content. The combination of the various sensors on the same platform will continue to enhance our understanding of the connections between processes that drive our coastal oceans. An additional research area with potential use for gliders is fisheries management. Fish stock assessment depend upon data sets from fishery dependent or independent surveys that are used to set harvest limits. In the eastern Gulf of Mexico, many economically important species are benthic and generally tied to preferred habitat types. State, federal, and academic groups are coordinating efforts to generate habitat-specific population estimates, the first step of which is creating habitat maps to guide visual or trap surveys for the fish. This is typically done by initially creating detailed bathymetric maps of regions and assessing the bottom types through video and other methods to characterize the seafloor structure, habitat and the distribution of biota. However, visually mapping the entire West Florida Shelf is not feasible. Autonomous systems like gliders should be employed as a first-level reconnaissance tool to opportunistically discover reef features or fish hotspots. For the past several years, we’ve attempted to assess fish populations, site fidelity, migration, and other relevant characteristics by integrating passive acoustic recorders, tag telemetry receivers, and fisheries echosounders to a glider tasked with repeated transects within a test region. Our test region has been a large, well-known artificial reef, the Gulfstream Natural Gas Pipeline, a largely linear feature between Tampa Bay and Mobile Bay. Our sampling has been seasonal and focused on the eastern portion of this feature between the 30 and 50m isobaths on the West Florida Shelf (WFS) with a total of five deployments of a single glider completed. Yet, while the linear reef is a wonderful target for the glider, gliders cannot easily traverse a straight line when coastal tidal currents are involved. So, in typical meandering fashion, the glider would spend a lot of time in the region of the pipeline, but not directly over the pipe. We accepted these data as opportunistic and another form of reconnaissance that can inform the design of follow-on surveys. During our efforts, we have used glider-collected acoustic data to identify several “hotspot” locations with high fish densities for which we do not yet have habitat maps nor measures of fish abundance. We subsequently mapped one of these regions with high resolution multibeam echosounder to create detailed bathymetric imagery of the seafloor. This has resulted in discovering previously unknown regions of habitat including seafloor ridges and demersal fish excavated zones known as “grouper holes”. This technological approach, if applied in an observing system capacity of sustained and continuous operations over a region like the West Florida Shelf, will augment existing efforts to identify and describe fish habitat and help provide data sets complimentary to fish stock assessment.
Underwater gliders have been widely used in oceanography for a range of applications. However, un... more Underwater gliders have been widely used in oceanography for a range of applications. However, unpredictable events like shark strikes or remora attachments can lead to abnormal glider behavior or even loss of the instrument. This paper employs an anomaly detection algorithm to assess operational conditions of underwater gliders in the real-world ocean environment. Prompt alerts are provided to glider pilots upon detecting any anomaly, so that they can take control of the glider to prevent further harm. The detection algorithm is applied to multiple datasets collected in real glider deployments led by the University of Georgia's Skidaway Institute of Oceanography (SkIO) and the University of South Florida (USF). In order to demonstrate the algorithm generality, the experimental evaluation is applied to four glider deployment datasets, each highlighting various anomalies happening in different scenes. Specifically, we utilize high resolution datasets only available post-recovery to perform detailed analysis of the anomaly and compare it with pilot logs. Additionally, we simulate the online detection based on the real-time subsets of data transmitted from the glider at the surfacing events. While the real-time data may not contain as much rich information as the post-recovery one, the online detection is of great importance as it allows glider pilots to monitor potential abnormal conditions in real time.
Underwater gliders are widely utilized for ocean sampling, surveillance, and other various oceani... more Underwater gliders are widely utilized for ocean sampling, surveillance, and other various oceanic applications. In the context of complex ocean environments, gliders may yield poor navigation performance due to strong ocean currents, thus requiring substantial human effort during the manual piloting process. To enhance navigation accuracy, we developed a real-time autonomous glider navigation software, named GENIoS Python, which generates waypoints based on flow predictions to assist human piloting. The software is designed to closely check glider status, provide customizable experiment settings, utilize lightweight computing resources, offer stably communicate with dockservers, robustly run for extended operation time, and quantitatively compare flow estimates, which add to its value as an autonomous tool for underwater glider navigation.
This paper utilizes an anomaly detection algorithm to check if underwater gliders are operating n... more This paper utilizes an anomaly detection algorithm to check if underwater gliders are operating normally in the unknown ocean environment. Glider pilots can be warned of the detected glider anomaly in real time, thus taking over the glider appropriately and avoiding further damage to the glider. The adopted algorithm is validated by two valuable sets of data in real glider deployments, the University of South Florida (USF) glider Stella and the Skidaway Institute of Oceanography (SkIO) glider Angus.
The long term goal is development and utilization of a bottom stationed autonomous ocean profiler... more The long term goal is development and utilization of a bottom stationed autonomous ocean profiler. The system is capable of bi-directional satellite communcation via the ORBCOMM system, is user programmable and can store and/or transmit aquired data in near real-time. Deployment of large numbers of BSOP systems, each equipped with a highly capable sensor suite, can be used to synoptically observe marine environments with very low initial capital investment and even lower operations costs.
A GPS-buoy system has been built and is currently undergoing test to measure precise 3D sea floor... more A GPS-buoy system has been built and is currently undergoing test to measure precise 3D sea floor motion in the shallow (less than 200 m) continental shelf environment. Offshore deformation is undersampled in most subduction zones. In Cascadia, the shallow shelf environment constitutes roughly 20%-25% of the offshore area between the coastline and the trench. In the system being tested, the GPS receiver at the top of the buoy is connected to the sea floor through a rigid structure supported by a float. A similar design has been used by INGV (Italy) to measure vertical deformation on the sea floor near the Campi Flegrei caldera. Synthetic analysis shows that by adding a 3-axis digital compass to measure heading and tilt, along with kinematic GPS measurements, position of the anchor can be recovered to an accuracy of several centimeters or better, depending on water depth and GPS baseline length. Synthetic resolution tests show that our ability to detect shallow slow slip events on subduction plate boundaries can be greatly improved by adding offshore GPS-buoy sites
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Papers by Chad Lembke