Research

Exploration

IMT lab researchers uncover phenomena relating to the sea. Below displays research topics, innovative technologies, and related scientific publications.

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Air-Sea Gas Transfer

air sea gas transfer

A diverse range of studies are conducted to observe and understand the effects of waves and wave breaking on air-sea exchanges.

The Acoustal and Physical Characterization of Bubble Plumes >

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Bioluminescent Dinoflagellates

bioluminescent dinoflaggellates

The IMT Laboratory has developed a novel means of measuring fluid shear stress using the cell flashing behavior of bioluminescent dinoflagellates.

Bioluminescent Dinoflagellates >

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Near Shore Dynamics

near shore dynamics

Research in near shore dynamics with its focus on small scale interfacial processes is viewed as a major strength of the IMT Lab as it provides a unique opportunity to gain insight into a variety of large scale weather and climate dynamics.

Near Shore Biological Coupling >

Underwater Ambient Communication >

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Polar Science

Barne Glaciers

IMT Lab researchers study the dynamic and complex nature of climate-driven ice-water interactions such as glacial calving events and energy transport from the atmosphere to the seafloor with colleagues at Scripps Institution of Oceanography and the University of Otago, New Zealand.

Underwater Acoustic Signatures of Glacier Calving >

News Mentions

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Seafloor

THOR technology

Explorations are made in new domain-optimized high-performance computation methods for automatic image classification and search to enable seafloor population surveys at landscape scales.

THOR >

APEX Array

The development by the IMT Laboratory of an Advanced Plume Sensor System (APEX) provides principal observations of plume structure necessary for scattering and noise models.

The Advanced Plume Sensor System (APEX) is a multi-sensor package designed to probe the structure of the dense bubble plumes beneath ocean whitecaps on several simultaneous spatial scales and provide information about bubble plume scale and roughness, the bubble size distribution and turbulence within the plume.

Plumes are created by breaking waves beneath whitecaps and, amongst other things, generate ambient noise, scatter sound at the ocean surface and enhance air-sea gas exchange. The study of bubble plumes is important for predicting oceanic noise, modeling underwater communications and sonar performance, and understanding global climate change.

Instrumentation

The Advanced Plume Sensor System is a multi-sensor package designed to probe the structure of the dense bubble plumes beneath ocean whitecaps on several simultaneous spatial scales. The instrument package includes:

  • an optical bubble counter
  • a vertical array of 4-ring conductivity sensors
  • a conductivity/temperature sensor
  • a vertical array of four 3-axis acoustic Doppler velocity meters
  • an acoustic system for measuring plume scattering cross-section
  • laser-based bubble scattering system

These sensors simultaneously measure the bubble size distribution and void fraction of air within whitecap plumes, the size of the plumes and scaling of plume size with sea state, the acoustical roughness scales of the plume boundaries and the noise radiated during plume formation.

Design

APEX consists of the instrumentation package described above mounted onto two surface-following frames. The principal frame supports Doppler sonars and ring conductivity sensors co-located on a vertical array to simultaneously measure the void fraction of air and water turbulence during a breaking wave event. The laser-based imaging system and optical bubble counter are positioned adjacent to the vertical array to measure bubble size distributions and the bubble plume boundary at a fixed depth. The principal frame also supports PC104-based data acquisition computers to power and control the measurement instrumentation. All instrument computers are connected to a network, which is cabled to control station through a single umbical. All systems can be remotely integorrated and controlled from the control station. A secondary frame, remote from but cabled to the primary frame, supports the acosutical scattering cross-section measurements.

APEX is designed to be deployed in 15-35 knot winds using the R/P Flip in deep water or on a horizontal mooring in shallow water. The instrument package is mounted on a surface-following frame that keeps the sensors within the top 40 cm of the upper-ocean boundary layer, which is the active region of wave breaking and air entrainment. Each instrument is controlled with a PC104 computer mounted on the sensor frame, allowing real-time data acquisition and control via a copper or wireless network connection.

Observation

Wave-induced bubble plumes are important in the following areas of acoustics:

  • generation of ambient noise
  • high frequency scattering at the ocean surface
  • acoustic communications through the littoral zone
  • air-sea mixing

Despite the central role in these areas, little is known about the physical properties of dense bubble plumes in the first few seconds following wave breaking. The advanced plume sensor system is designed to provide information of the measurement of plume scale, roughness and bubble sizes.

APEX provides principal observations of bubble plume structure necessary for high frequency scattering and noise models during high wind conditions (>20 knots). The overall objective is to generate physics-based models of plume generation and internal structure, and relate these to their observed acoustical properties.

In addition to providing valuable information about open-ocean induced bubble plumes, APEX can be deployed in the surf zone to characterize the acoustical cross-sections of surf-induced bubble plumes.

Tech Application

APEX has been deployed on numerous experiments. APEX was deployed in the winter of 2002 at the Martha’s Vineyard Coastal Observatory (MVCO) during the SPACE02 experiment funded by the ONR Ocean Acoustics Program and hosted by Dr. James Preisig at Woods Hole Oceanographic Institution. Collaborators included Dr. David Farmer at the Graduate School of Oceanography, University of Rhode Island and Dr. Svein Vagle from the Institute of Ocean Sciences, British Colombia.

Link to Research

BOA Array

A novel combination of technologies assembled by the IMT lab has produced an instrument system (BOA) that can be deployed easily, surveyed accurately and built inexpensively for use in marine and terrestrial environments. The design of the BOA digital electronics allow sensor nodes to include different types of transducers and allows up to 150 nodes to be encapsulated onto a single array cable allowing hundreds of sensor measurements to be collected synchronously at rapid intervals.

Successful deployments of BOA have generated considerable interest in the marine science community, not only to adopt the present temperature/pressure technology, but to use the BOA technology with different environmental sensors. The BOA I system has been used for a study of the physical hydrography affecting Floridian coral reefs on a 10 second temporal scale over 3 months and a spatial scale from 2 m to 100’s of meters. The BOA II system has been used to study the shoaling surface gravity field in the surf zone adjacent to the SIO pier

Of particular interest is the potential to use different transducers with the time-division multiplexed BOA design. In this manner, a BOA array with hundreds of nodes could be produced that include , temperature, oxygen, irradiance, conductivity, and transmissivity sensors at each node at a fraction of the expense of hundreds of commercially available instruments.

Bubblecam

bubble cam technology

Obtaining bubble measurements inside breaking wave plumes is difficult because of strong sound and light attenuation. By designing an instrument that maintains a clear optical path between the imaging optics and the volume of bubbles under study captures bubble imagery that provides information on bubble size spectra and spatial distribution. The BubbleCam operates by producing a high intensity sheet of light (3.5 mm by 37 mm high) a few millimeters in front of the optical face plate. Bubbles in this region are brightly illuminated and captured on high-speed video tape. Computer analysis of the resulting images generates estimates of the bubble size frequency distribution over time. The Bubblecam imaging instrument has been deployed in the surf zone and open ocean to generate images of bubbles formed beneath the crests of breaking ocean waves.

Scientists at the IMT Laboratory have developed a high-speed optical imaging system coined the “BubbleCam” to quantify bubble distributions which occur within the turbulent air-water mixture within a breaking wave crest.

Measurements of the formation of bubbles at the air-sea interface provide important information on:

  • global climate change
  • ocean and atmospheric processes
  • air-sea gas transfer
  • heat and moisture exchange
  • aerosol production
  • production of underwater noise

THOR

A new seafloor acoustic and optical imaging system (THOR) is deployed by the Scripps Institution of Oceanography for field operations world-wide. THOR is capable of collecting high-resolution broadband and multi-spectral fluorescent images, acoustic signals, and water column metrics (temperature for salinity) for shallow water marine environments over large spatial scales. Funded by the Seaver Institute, THOR is based on successful prototypes by the PIs (tested on the species-diverse and complex terrain of a coral reef) and designed to generate large volumes of high-detail seafloor data requiring automated classification of organisms and terrain features.

Link to Research

2015

Underwater acoustic signatures of glacier calving

Glowacki, O, Deane GB, Moskalik M, Blondel P, Tegowski J, Blaszczyk M.  2015.  Underwater acoustic signatures of glacier calving. Geophysical Research Letters. :2014GL062859.

Date Published: Feb 2015

Abstract: Climate-driven ice-water interactions in the contact zone between marine-terminating glaciers and the ocean surface show a dynamic and complex nature. Tidewater glaciers lose volume through the poorly understood process of calving. A detailed description of the mechanisms controlling the course of calving is essential for the reliable estimation and prediction of mass loss from glaciers. Here we present the potential of hydroacoustic methods to investigate different modes of ice detachments. High-frequency underwater ambient noise recordings are combined with synchronized, high-resolution, time-lapse photography of the Hans Glacier cliff in Hornsund Fjord, Spitsbergen, to identify three types of calving events: typical subaerial, sliding subaerial, and submarine. A quantitative analysis of the data reveals a robust correlation between ice impact energy and acoustic emission at frequencies below 200 Hz for subaerial calving. We suggest that relatively inexpensive acoustic methods can be successfully used to provide quantitative descriptions of the various calving types.

2004

Bioluminescence imaging of wave-induced turbulence

Stokes, MD, Deane GB, Latz MI, Rohr J.  2004.  Bioluminescence imaging of wave-induced turbulence. Journal of Geophysical Research-Oceans. 109

Date Published: Jan 2004

Abstract: The ability to measure turbulent processes on small spatial and temporal scales is a long standing problem in physical oceanography. Here we explore a novel means of measuring fluid shear stress using the cell flashing behavior of bioluminescent dinoflagellates. To illustrate this technique, we present estimates of the heterogeneous, time-varying shear stress inside a breaking wave crest. These results have implications for a better understanding of upper ocean wave physics, air-sea gas transfer, and the biology of planktonic near-surface organisms as well as providing a new quantitative fluid visualization tool.

2002

A robust single-cable sensor array for oceanographic use

Deane, GB, Stokes MD.  2002.  A robust single-cable sensor array for oceanographic use. IEEE Journal of Oceanic Engineering. 27:760-767.

Date Published: July 2002

Abstract: Simple, inexpensive and easy to deploy, pressure and temperature arrays have been constructed and tested in the near shore. A method has been devised whereby low data-rate sensors can be powered and send data over a two-conductor cable using time division multiplexing. Using this technology it is possible to rapidly deploy large numbers of sensors in environments that are impractical to instrument with individually cabled or autonomous sensors. Pressure and temperature data collected using two arrays in the surf zone are shown to illustrate the practicality of the deployment method and feasibility of the technology.

Scale dependence of bubble creation mechanisms in breaking waves

Deane, GB, Stokes MD.  2002.  Scale dependence of bubble creation mechanisms in breaking waves. Nature. 418:839-844.

Date Published: Aug 2002

Abstract: Breaking ocean waves entrain air bubbles that enhance air-sea gas flux, produce aerosols, generate ambient noise and scavenge biological surfactants. The size distribution of the entrained bubbles is the most important factor in controlling these processes, but little is known about bubble properties and formation mechanisms inside whitecaps. We have measured bubble size distributions inside breaking waves in the laboratory and in the open ocean, and provide a quantitative description of bubble formation mechanisms in the laboratory. We find two distinct mechanisms controlling the size distribution, depending on bubble size. For bubbles larger than about 1 mm, turbulent fragmentation determines bubble size distribution, resulting in a bubble density proportional to the bubble radius to the power of -10/3. Smaller bubbles are created by jet and drop impact on the wave face, with a -3/2 power-law scaling. The length scale separating these processes is the scale where turbulent fragmentation ceases, also known as the Hinze scale. Our results will have important implications for the study of air-sea gas transfer.

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Research Topics

.

Air-Sea Gas Transfer

air sea gas transfer

A diverse range of studies are conducted to observe and understand the effects of waves and wave breaking on air-sea exchanges.

The Acoustal and Physical Characterization of Bubble Plumes >

.

Bioluminescent Dinoflagellates

bioluminescent dinoflaggellates

The IMT Laboratory has developed a novel means of measuring fluid shear stress using the cell flashing behavior of bioluminescent dinoflagellates.

Bioluminescent Dinoflagellates >

.

Near Shore Dynamics

near shore dynamics

Research in near shore dynamics with its focus on small scale interfacial processes is viewed as a major strength of the IMT Lab as it provides a unique opportunity to gain insight into a variety of large scale weather and climate dynamics.

Near Shore Biological Coupling >

Underwater Ambient Communication >

.

Polar Science

Barne Glaciers

IMT Lab researchers study the dynamic and complex nature of climate-driven ice-water interactions such as glacial calving events and energy transport from the atmosphere to the seafloor with colleagues at Scripps Institution of Oceanography and the University of Otago, New Zealand.

Underwater Acoustic Signatures of Glacier Calving >

News Mentions

.

Seafloor

THOR technology

Explorations are made in new domain-optimized high-performance computation methods for automatic image classification and search to enable seafloor population surveys at landscape scales.

THOR >

.

Technology

APEX Array

The development by the IMT Laboratory of an Advanced Plume Sensor System (APEX) provides principal observations of plume structure necessary for scattering and noise models.

The Advanced Plume Sensor System (APEX) is a multi-sensor package designed to probe the structure of the dense bubble plumes beneath ocean whitecaps on several simultaneous spatial scales and provide information about bubble plume scale and roughness, the bubble size distribution and turbulence within the plume.

Plumes are created by breaking waves beneath whitecaps and, amongst other things, generate ambient noise, scatter sound at the ocean surface and enhance air-sea gas exchange. The study of bubble plumes is important for predicting oceanic noise, modeling underwater communications and sonar performance, and understanding global climate change.

Instrumentation

The Advanced Plume Sensor System is a multi-sensor package designed to probe the structure of the dense bubble plumes beneath ocean whitecaps on several simultaneous spatial scales. The instrument package includes:

  • an optical bubble counter
  • a vertical array of 4-ring conductivity sensors
  • a conductivity/temperature sensor
  • a vertical array of four 3-axis acoustic Doppler velocity meters
  • an acoustic system for measuring plume scattering cross-section
  • laser-based bubble scattering system

These sensors simultaneously measure the bubble size distribution and void fraction of air within whitecap plumes, the size of the plumes and scaling of plume size with sea state, the acoustical roughness scales of the plume boundaries and the noise radiated during plume formation.

Design

APEX consists of the instrumentation package described above mounted onto two surface-following frames. The principal frame supports Doppler sonars and ring conductivity sensors co-located on a vertical array to simultaneously measure the void fraction of air and water turbulence during a breaking wave event. The laser-based imaging system and optical bubble counter are positioned adjacent to the vertical array to measure bubble size distributions and the bubble plume boundary at a fixed depth. The principal frame also supports PC104-based data acquisition computers to power and control the measurement instrumentation. All instrument computers are connected to a network, which is cabled to control station through a single umbical. All systems can be remotely integorrated and controlled from the control station. A secondary frame, remote from but cabled to the primary frame, supports the acosutical scattering cross-section measurements.

APEX is designed to be deployed in 15-35 knot winds using the R/P Flip in deep water or on a horizontal mooring in shallow water. The instrument package is mounted on a surface-following frame that keeps the sensors within the top 40 cm of the upper-ocean boundary layer, which is the active region of wave breaking and air entrainment. Each instrument is controlled with a PC104 computer mounted on the sensor frame, allowing real-time data acquisition and control via a copper or wireless network connection.

Observation

Wave-induced bubble plumes are important in the following areas of acoustics:

  • generation of ambient noise
  • high frequency scattering at the ocean surface
  • acoustic communications through the littoral zone
  • air-sea mixing

Despite the central role in these areas, little is known about the physical properties of dense bubble plumes in the first few seconds following wave breaking. The advanced plume sensor system is designed to provide information of the measurement of plume scale, roughness and bubble sizes.

APEX provides principal observations of bubble plume structure necessary for high frequency scattering and noise models during high wind conditions (>20 knots). The overall objective is to generate physics-based models of plume generation and internal structure, and relate these to their observed acoustical properties.

In addition to providing valuable information about open-ocean induced bubble plumes, APEX can be deployed in the surf zone to characterize the acoustical cross-sections of surf-induced bubble plumes.

Tech Application

APEX has been deployed on numerous experiments. APEX was deployed in the winter of 2002 at the Martha’s Vineyard Coastal Observatory (MVCO) during the SPACE02 experiment funded by the ONR Ocean Acoustics Program and hosted by Dr. James Preisig at Woods Hole Oceanographic Institution. Collaborators included Dr. David Farmer at the Graduate School of Oceanography, University of Rhode Island and Dr. Svein Vagle from the Institute of Ocean Sciences, British Colombia.

Link to Research

BOA Array

A novel combination of technologies assembled by the IMT lab has produced an instrument system (BOA) that can be deployed easily, surveyed accurately and built inexpensively for use in marine and terrestrial environments. The design of the BOA digital electronics allow sensor nodes to include different types of transducers and allows up to 150 nodes to be encapsulated onto a single array cable allowing hundreds of sensor measurements to be collected synchronously at rapid intervals.

Successful deployments of BOA have generated considerable interest in the marine science community, not only to adopt the present temperature/pressure technology, but to use the BOA technology with different environmental sensors. The BOA I system has been used for a study of the physical hydrography affecting Floridian coral reefs on a 10 second temporal scale over 3 months and a spatial scale from 2 m to 100’s of meters. The BOA II system has been used to study the shoaling surface gravity field in the surf zone adjacent to the SIO pier

Of particular interest is the potential to use different transducers with the time-division multiplexed BOA design. In this manner, a BOA array with hundreds of nodes could be produced that include , temperature, oxygen, irradiance, conductivity, and transmissivity sensors at each node at a fraction of the expense of hundreds of commercially available instruments.

Bubblecam

bubble cam technology

Obtaining bubble measurements inside breaking wave plumes is difficult because of strong sound and light attenuation. By designing an instrument that maintains a clear optical path between the imaging optics and the volume of bubbles under study captures bubble imagery that provides information on bubble size spectra and spatial distribution. The BubbleCam operates by producing a high intensity sheet of light (3.5 mm by 37 mm high) a few millimeters in front of the optical face plate. Bubbles in this region are brightly illuminated and captured on high-speed video tape. Computer analysis of the resulting images generates estimates of the bubble size frequency distribution over time. The Bubblecam imaging instrument has been deployed in the surf zone and open ocean to generate images of bubbles formed beneath the crests of breaking ocean waves.

Scientists at the IMT Laboratory have developed a high-speed optical imaging system coined the “BubbleCam” to quantify bubble distributions which occur within the turbulent air-water mixture within a breaking wave crest.

Measurements of the formation of bubbles at the air-sea interface provide important information on:

  • global climate change
  • ocean and atmospheric processes
  • air-sea gas transfer
  • heat and moisture exchange
  • aerosol production
  • production of underwater noise

THOR

A new seafloor acoustic and optical imaging system (THOR) is deployed by the Scripps Institution of Oceanography for field operations world-wide. THOR is capable of collecting high-resolution broadband and multi-spectral fluorescent images, acoustic signals, and water column metrics (temperature for salinity) for shallow water marine environments over large spatial scales. Funded by the Seaver Institute, THOR is based on successful prototypes by the PIs (tested on the species-diverse and complex terrain of a coral reef) and designed to generate large volumes of high-detail seafloor data requiring automated classification of organisms and terrain features.

Link to Research

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Publications

2015

Underwater acoustic signatures of glacier calving

Glowacki, O, Deane GB, Moskalik M, Blondel P, Tegowski J, Blaszczyk M.  2015.  Underwater acoustic signatures of glacier calving. Geophysical Research Letters. :2014GL062859.

Date Published: Feb 2015

Abstract: Climate-driven ice-water interactions in the contact zone between marine-terminating glaciers and the ocean surface show a dynamic and complex nature. Tidewater glaciers lose volume through the poorly understood process of calving. A detailed description of the mechanisms controlling the course of calving is essential for the reliable estimation and prediction of mass loss from glaciers. Here we present the potential of hydroacoustic methods to investigate different modes of ice detachments. High-frequency underwater ambient noise recordings are combined with synchronized, high-resolution, time-lapse photography of the Hans Glacier cliff in Hornsund Fjord, Spitsbergen, to identify three types of calving events: typical subaerial, sliding subaerial, and submarine. A quantitative analysis of the data reveals a robust correlation between ice impact energy and acoustic emission at frequencies below 200 Hz for subaerial calving. We suggest that relatively inexpensive acoustic methods can be successfully used to provide quantitative descriptions of the various calving types.

2004

Bioluminescence imaging of wave-induced turbulence

Stokes, MD, Deane GB, Latz MI, Rohr J.  2004.  Bioluminescence imaging of wave-induced turbulence. Journal of Geophysical Research-Oceans. 109

Date Published: Jan 2004

Abstract: The ability to measure turbulent processes on small spatial and temporal scales is a long standing problem in physical oceanography. Here we explore a novel means of measuring fluid shear stress using the cell flashing behavior of bioluminescent dinoflagellates. To illustrate this technique, we present estimates of the heterogeneous, time-varying shear stress inside a breaking wave crest. These results have implications for a better understanding of upper ocean wave physics, air-sea gas transfer, and the biology of planktonic near-surface organisms as well as providing a new quantitative fluid visualization tool.

2002

A robust single-cable sensor array for oceanographic use

Deane, GB, Stokes MD.  2002.  A robust single-cable sensor array for oceanographic use. IEEE Journal of Oceanic Engineering. 27:760-767.

Date Published: July 2002

Abstract: Simple, inexpensive and easy to deploy, pressure and temperature arrays have been constructed and tested in the near shore. A method has been devised whereby low data-rate sensors can be powered and send data over a two-conductor cable using time division multiplexing. Using this technology it is possible to rapidly deploy large numbers of sensors in environments that are impractical to instrument with individually cabled or autonomous sensors. Pressure and temperature data collected using two arrays in the surf zone are shown to illustrate the practicality of the deployment method and feasibility of the technology.

Scale dependence of bubble creation mechanisms in breaking waves

Deane, GB, Stokes MD.  2002.  Scale dependence of bubble creation mechanisms in breaking waves. Nature. 418:839-844.

Date Published: Aug 2002

Abstract: Breaking ocean waves entrain air bubbles that enhance air-sea gas flux, produce aerosols, generate ambient noise and scavenge biological surfactants. The size distribution of the entrained bubbles is the most important factor in controlling these processes, but little is known about bubble properties and formation mechanisms inside whitecaps. We have measured bubble size distributions inside breaking waves in the laboratory and in the open ocean, and provide a quantitative description of bubble formation mechanisms in the laboratory. We find two distinct mechanisms controlling the size distribution, depending on bubble size. For bubbles larger than about 1 mm, turbulent fragmentation determines bubble size distribution, resulting in a bubble density proportional to the bubble radius to the power of -10/3. Smaller bubbles are created by jet and drop impact on the wave face, with a -3/2 power-law scaling. The length scale separating these processes is the scale where turbulent fragmentation ceases, also known as the Hinze scale. Our results will have important implications for the study of air-sea gas transfer.