David M Fratantoni | Woods Hole Oceanographic Institution (original) (raw)

Papers by David M Fratantoni

1] Acoustic float data collected near 800 m depth, are used to map zonal mean currents within the... more 1] Acoustic float data collected near 800 m depth, are used to map zonal mean currents within the Antarctic Intermediate Water (AAIW) tongue in the equatorial Atlantic. Alternating zonal jets of 2°latitudinal width are revealed between 6°S and 6°N. Displacements from profiling floats drifting near 1000 m depth, also reveal similar zonal jets at the base of the AAIW layer. The strongest jets (15 cm s À1 peak) are found at 4°S, 2°S, 0°, 2°N and 4°N. They are coherent longitudinally over order of 3000 km and, poleward of 1°S and 1°N, generally coherent vertically between 800 m and 1000 m. Large seasonal fluctuations exist at both levels: within 1°of equator, AAIW at 800 m flows westward (8 cm s À1 mean) in boreal summer and fall but eastward (3 cm s À1 mean) in winter, whereas the flow at 1000 m is eastward in late fall and winter. Citation: Ollitrault, M., M. Lankhorst,

0 0 1930 CLIVAR Mode Water Dynamics Experiment (CLIMODE) Fall 2005 R/V Oceanus

The public reporting burden for this collection of information is estimated to average 1 hour per... more The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-01881, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for falling to comply with a collection of information if it does not display a currently valid 0MB control number.

Our long-term goal is to develop a relocatable, sustainable, infrastructure-free ocean observing ... more Our long-term goal is to develop a relocatable, sustainable, infrastructure-free ocean observing system composed of low-cost, high-endurance vehicles with near-global range and a modular sensor payload. Particular emphasis is placed on the development of adaptive sampling strategies and the automated control of large glider fleets.

The Autonomous Ocean Sampling Networks (AOSN) program is an ambitious and ongoing ONR effort to c... more The Autonomous Ocean Sampling Networks (AOSN) program is an ambitious and ongoing ONR effort to combine new robotic vehicles and sampling methodologies with advanced ocean models to improve our ability to observe and predict the physical and biological state of the ocean. The AOSN-II field program was performed in Monterey Bay from mid-July to early September 2003. More than 20 autonomous underwater vehicles and a variety of in-situ and remote instrument systems were used to observe the evolution of wind-forced coastal upwelling processes and their biological consequences. The AOSN-II program received a great deal of national and international attention, and the accomplishments of the AOSN-II team continue to impact the development of regional observing strategies and systems including the NSF OOI. This award enabled broad dissemination of results from the AOSN-II field experiment via a special volume of Deep-Sea Research II.

Our long-term goal is to develop an efficient, sustainable, and relocatable observing system suit... more Our long-term goal is to develop an efficient, sustainable, and relocatable observing system suitable for a variety of exploratory, process-oriented oceanographic studies and naval applications. Our basic strategy is to combine technology development with significant field experiments which advance our understanding of the ocean environment.

The earth's largest ocean rings are spawned near 8°N in the western tropical Atlantic from th... more The earth's largest ocean rings are spawned near 8°N in the western tropical Atlantic from the equator-crossing North Brazil Current (NBC). NBC rings, which can exceed 450 km in diameter and 2000 m in vertical extent, translate northwestward parallel to the South American coastline until they collide with the Lesser Antilles in the southeastern Caribbean Sea. The rings entrain filaments of nutrient- and sediment-rich Amazon and Orinoco River discharge, impact the distribution of icthyoplankton, and pose a physical threat to expanding offshore oil and gas exploration. The six rings generated annually are also responsible for up to one-third of the equatorial-to-subtropical mass and heat transport associated with the Atlantic meridional overturning circulation, a fundamental component of the earth climate system. Recent RAFOS float and surface drifter trajectories illustrate the translation and structural evolution of several NBC rings and enable the determination of the downstrea...

Twenty-one RAFOS floats were tracked at depths of 200-1000 meters in and around several North Bra... more Twenty-one RAFOS floats were tracked at depths of 200-1000 meters in and around several North Brazil Current Rings between November 1998 and June 2000. This was part of an experiment to study the role of these current rings in transporting upper level South Atlantic water across the equatorial-tropical gyre boundary into the North Atlantic subtropical gyre. The float trajectories in combination with surface drifters and satellite imagery reveal the sometimes complex life histories of several rings and their fate as they collide with the Lesser Antilles

Marine Technology Society Journal, 2014

Persistently poor weather in the Arctic makes traditional marine mammal research from aircraft an... more Persistently poor weather in the Arctic makes traditional marine mammal research from aircraft and ships difficult, yet collecting information on marine mammal distribution and habitat utilization is vital for understanding the impact of climate change on Arctic ecosystems. Moreover, as industrial use of the Arctic increases with the expansion of the open-water summer season, there is an urgent need to monitor the effects of noise from oil and gas exploration and commercial shipping on marine mammals. During September 2013, we deployed a single Slocum glider equipped with a digital acoustic monitoring (DMON) instrument to record and process in situ low-frequency (<5 kHz) audio to characterize marine mammal occurrence and habitat as well as ambient noise in the Chukchi Sea off the northwest coast of Alaska, USA. The DMON was programmed with the low-frequency detection and classification system (LFDCS) to autonomously detect and classify sounds of a variety of Arctic and sub-Arctic marine mammal species. The DMON/LFDCS reported regularly in near real time via Iridium satellite detailed detection data, summary classification information, and spectra of background noise. The spatial distributions of bowhead whale, bearded seal, and walrus call rates were correlated with surface salinity measured by the glider. Bowhead whale and walrus call rates were strongly associated with a warm and salty water mass of Bering Sea origin. With a passive acoustic capability that allows both archival recording and near real-time reporting, we envision ocean gliders will become a standard tool for marine mammal and ocean noise research and monitoring in the Arctic.

Journal of Physical Oceanography, 2002

... SeaWiFS measures chlorophyll a and water leaving radiances at six wavelengths (Hooker et al. ... more ... SeaWiFS measures chlorophyll a and water leaving radiances at six wavelengths (Hooker et al. 1992; McClain et al. ... Further details regarding the SeaWiFS instrument, calibration methodologies, and data processing can be found in Hooker et al. (1992) and McClain et al. ...

Journal of Geophysical Research, 2001

A new compilation of Lagrangian velocity observations describes the state of the North Atlantic s... more A new compilation of Lagrangian velocity observations describes the state of the North Atlantic surface circulation during the 1990s. Gridded fields of velocity and eddy kinetic energy (EKE) are constructed from trajectories of more than 1500 15-m drogued satellite-tracked surface drifters in service between January 1990 and December 1999. This time period overlaps a coordinated field study of circulation and variability in the North Atlantic completed between 1996-2000 as part of the World Ocean Circulation Experiment. We describe the construction of a self-consistent drifter climatology, present decadal-mean quasi-Eulerian velocity and EKE fields computed on a 1 ø grid, and compare these results with contemporary satellite measurements. Detailed discussion of the inferred surface circulation is focused on three regions: (1) The Gulf Stream and North Atlantic Current, (2) the Labrador Sea and subpolar gyre, and (3) the Caribbean Sea. The swiftest drifter motions were found in the equatorial region and along the tropical, subtropical, and subpolar western boundaries. The maximum instantaneous speed determined from a single (quality-controlled and filtered) drifter observation was 273 cm s -• in the Gulf Stream southeast of Cape Cod. The highest EKE value in the North Atlantic (2790 cm 2 s -2) was found in the Gulf Stream just downstream of the New England Seamounts. Over most of the Atlantic basin, drifter-derived EKE values were found to be O(100 cm 2 s -2) higher than corresponding values derived from satellite altimetry. In the Labrador Sea a region of sharply elevated EKE appears to be geographically related to the localized ejection of drifters (and by extension, mass and kinetic energy) from the energetic West Greenland Current between 60 ø and 62øN. When compared to drifter measurements made in the late 1970s our results suggest (but do not statistically confirm) an enhancement and slight northward shift of the zonal Gulf Stream extension. Such a shift is consistent in sign with expectations based on observed interdecadal variations in wind stress and subtropical gyre potential energy associated with the North Atlantic Oscillation. 1. Introduction Over the last 75 years, numerous investigators have attempted to describe and quantify the low-frequency circulation of the North Atlantic using an expanding collection of hydrographic profiles and direct velocity measurements. Notable among these efforts are the pioneering field studies of Iseh'n [1936] who elucidated the large-scale structure of the subtropical gyre and the Gulf Stream, and the syntheses of I4/orthington [1976] who quantified transports and tracer relationships throughout the North Atlantic. Recent synthesis efforts [e.g., Schmitz and Richardson, 1991: Schmitz and McCartney, 1993; Schmitz, 1995] have incorporated direct measurements of ocean velocities in an effort to refine estimates of the three-dimensional ocean circulation and illuminate transport pathways between the North Atlantic, its marginal seas. and the neighboring South Atlantic. Within the last 20 years, satellite-tracked Lagrangian drifters have emerged as an efficient means to explore upperocean circulation patterns independent of subsurface hydrographic measurements and the requisite (and sometimes difficult) choice of a geostrophic reference level. The number of drifter observations in the North Atlantic has increased sufficiently to enable a relatively high-resolution depiction of the basin-scale circulation and its variability. Of equal importance, the standardization of drifter design and drogue geometry [e.g., Sybrandy and Nillet, 1991: Nillet et al., 1995] has allowed the meaningful compilation of drifter trajectories measured at substantially different times enabling improved statistical confidence in the resulting circulation schemes.

Hydrobiologia, 2000

Seasonal and daily patterns of zooplankton populations are often predictable in natural lakes. Di... more Seasonal and daily patterns of zooplankton populations are often predictable in natural lakes. Distinct zonation and geomorphic differences in reservoirs, however, make ecological extrapolations from lakes to reservoirs uncertain. We describe the spatial and temporal distribution of zooplankton, algae, and water clarity across reservoir zones and along a depth gradient in Glen Elder Reservoir, Kansas. Daphnia species were most abundant in the lacustrine zone, with D. pulicaria numerically dominant in early spring and D. mendotae dominant later in 1999 and 2000. Rotifers (Keratella quadrata, Asplanchna spp.) were dominant in the riverine zone in 1999, 2000, and 2001. Algal biomass was not significantly different between zones through most of the sampling periods, except late April in 1999 and mid-April in 2000. Chlorophyll a exceeded 81 lg l )1 in the lacustrine zone in mid-to late-April in 1999 and 2000, and exceeded 90 lg l )1 in the riverine zone in mid-April. Water clarity was significantly lower in the riverine zone in 1999 and 2000.

The public reporting burden for this collection of information is estimated to average 1 hour per... more The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-01881, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information it it does not display a currently valid OMB control number.

Deep Sea Research Part II: Topical Studies in Oceanography, 2009

Prediction is very difficult, especially about the future.'' Origin disputed but often attributed... more Prediction is very difficult, especially about the future.'' Origin disputed but often attributed to physicist Niels Bohr.

An underwater glider is a buoyancy-propelled, fixedwing vehicle with attitude controlled complete... more An underwater glider is a buoyancy-propelled, fixedwing vehicle with attitude controlled completely, or in part, by means of internal mass redistribution. We have developed a physics-based nonlinear model of the dynamics of an underwater glider and adapted it to model the SLOCUM glider's geometry, rudder, ballast pump and internal movable mass. In this paper we identify the model parameters to match the steady glides in new flight test data from the SLOCUM glider. In the process we also estimate the buoyancy trim offset of the glider used in the flight tests.

Our primary long-term objective is to better understand the physical and biological mechanisms of... more Our primary long-term objective is to better understand the physical and biological mechanisms of formation and maintenance of thin layers of zooplankton. Because zooplankton can be strong sound scatterers, acoustic instruments are effective at detecting and describing zooplankton thin layers. Using a combination of instruments (acoustics, image-forming optics, ADCP's, CTD's, and bio-optical sensors) and sampling platforms (a fleet of gliders and a profiling package), we plan to determine the temporal and spatial scales of acoustic backscatter from zooplankton aggregations, the taxonomic and size composition of the zooplankton in such layers, and the associations of zooplankton thin layers with physical parameters. To do this, it is imperative that we understand the factors influencing the frequency dependent backscatter from the organisms. In particular, the orientations of the plankton relative to the acoustic source can have significant effects on the resultant backscatter. Hence, a

The Autonomous Ocean Sampling Network-II (AOSN-II) and Adaptive Sampling And Prediction (ASAP) pr... more The Autonomous Ocean Sampling Network-II (AOSN-II) and Adaptive Sampling And Prediction (ASAP) projects aim to develop a sustainable, portable, adaptive ocean observing and prediction system for use in coastal environments. These projects employ, among other observation platforms, autonomous underwater vehicles that carry sensors to measure physical and biological signals in the ocean. The measurements from all sensing platforms are assimilated in real-time into advanced ocean models. The objective is to coordinate the mobile assets in order to collect data of highest possible utility. Critical to this effort are reliable, efficient and adaptive control strategies to enable the mobile sensor platforms to collect data autonomously. In this paper, we summarize feedback control strategies that enable us to gather useful information over a wide spectrum of spatial and temporal scales. First, we design formation control strategies useful for sampling small spatial scale processes (less than 5 km). In this framework, the feedback control laws maintain a desired formation of vehicles and allow the group to locate interesting features in the ocean. Some of these control strategies were implemented on a group of underwater gliders in Monterey Bay in August 2003, as part of the AOSN-II project. Second, we direct mobile sensor networks to provide synoptic coverage to investigate larger scales (5−100 km). Coordinated vehicle trajectories are designed according to the spatial and temporal variability in the field in order to keep sensor measurements appropriately distributed in space and time.

1] Acoustic float data collected near 800 m depth, are used to map zonal mean currents within the... more 1] Acoustic float data collected near 800 m depth, are used to map zonal mean currents within the Antarctic Intermediate Water (AAIW) tongue in the equatorial Atlantic. Alternating zonal jets of 2°latitudinal width are revealed between 6°S and 6°N. Displacements from profiling floats drifting near 1000 m depth, also reveal similar zonal jets at the base of the AAIW layer. The strongest jets (15 cm s À1 peak) are found at 4°S, 2°S, 0°, 2°N and 4°N. They are coherent longitudinally over order of 3000 km and, poleward of 1°S and 1°N, generally coherent vertically between 800 m and 1000 m. Large seasonal fluctuations exist at both levels: within 1°of equator, AAIW at 800 m flows westward (8 cm s À1 mean) in boreal summer and fall but eastward (3 cm s À1 mean) in winter, whereas the flow at 1000 m is eastward in late fall and winter. Citation: Ollitrault, M., M. Lankhorst,

0 0 1930 CLIVAR Mode Water Dynamics Experiment (CLIMODE) Fall 2005 R/V Oceanus

The public reporting burden for this collection of information is estimated to average 1 hour per... more The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-01881, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for falling to comply with a collection of information if it does not display a currently valid 0MB control number.

Our long-term goal is to develop a relocatable, sustainable, infrastructure-free ocean observing ... more Our long-term goal is to develop a relocatable, sustainable, infrastructure-free ocean observing system composed of low-cost, high-endurance vehicles with near-global range and a modular sensor payload. Particular emphasis is placed on the development of adaptive sampling strategies and the automated control of large glider fleets.

The Autonomous Ocean Sampling Networks (AOSN) program is an ambitious and ongoing ONR effort to c... more The Autonomous Ocean Sampling Networks (AOSN) program is an ambitious and ongoing ONR effort to combine new robotic vehicles and sampling methodologies with advanced ocean models to improve our ability to observe and predict the physical and biological state of the ocean. The AOSN-II field program was performed in Monterey Bay from mid-July to early September 2003. More than 20 autonomous underwater vehicles and a variety of in-situ and remote instrument systems were used to observe the evolution of wind-forced coastal upwelling processes and their biological consequences. The AOSN-II program received a great deal of national and international attention, and the accomplishments of the AOSN-II team continue to impact the development of regional observing strategies and systems including the NSF OOI. This award enabled broad dissemination of results from the AOSN-II field experiment via a special volume of Deep-Sea Research II.

Our long-term goal is to develop an efficient, sustainable, and relocatable observing system suit... more Our long-term goal is to develop an efficient, sustainable, and relocatable observing system suitable for a variety of exploratory, process-oriented oceanographic studies and naval applications. Our basic strategy is to combine technology development with significant field experiments which advance our understanding of the ocean environment.

The earth's largest ocean rings are spawned near 8°N in the western tropical Atlantic from th... more The earth's largest ocean rings are spawned near 8°N in the western tropical Atlantic from the equator-crossing North Brazil Current (NBC). NBC rings, which can exceed 450 km in diameter and 2000 m in vertical extent, translate northwestward parallel to the South American coastline until they collide with the Lesser Antilles in the southeastern Caribbean Sea. The rings entrain filaments of nutrient- and sediment-rich Amazon and Orinoco River discharge, impact the distribution of icthyoplankton, and pose a physical threat to expanding offshore oil and gas exploration. The six rings generated annually are also responsible for up to one-third of the equatorial-to-subtropical mass and heat transport associated with the Atlantic meridional overturning circulation, a fundamental component of the earth climate system. Recent RAFOS float and surface drifter trajectories illustrate the translation and structural evolution of several NBC rings and enable the determination of the downstrea...

Twenty-one RAFOS floats were tracked at depths of 200-1000 meters in and around several North Bra... more Twenty-one RAFOS floats were tracked at depths of 200-1000 meters in and around several North Brazil Current Rings between November 1998 and June 2000. This was part of an experiment to study the role of these current rings in transporting upper level South Atlantic water across the equatorial-tropical gyre boundary into the North Atlantic subtropical gyre. The float trajectories in combination with surface drifters and satellite imagery reveal the sometimes complex life histories of several rings and their fate as they collide with the Lesser Antilles

Marine Technology Society Journal, 2014

Persistently poor weather in the Arctic makes traditional marine mammal research from aircraft an... more Persistently poor weather in the Arctic makes traditional marine mammal research from aircraft and ships difficult, yet collecting information on marine mammal distribution and habitat utilization is vital for understanding the impact of climate change on Arctic ecosystems. Moreover, as industrial use of the Arctic increases with the expansion of the open-water summer season, there is an urgent need to monitor the effects of noise from oil and gas exploration and commercial shipping on marine mammals. During September 2013, we deployed a single Slocum glider equipped with a digital acoustic monitoring (DMON) instrument to record and process in situ low-frequency (<5 kHz) audio to characterize marine mammal occurrence and habitat as well as ambient noise in the Chukchi Sea off the northwest coast of Alaska, USA. The DMON was programmed with the low-frequency detection and classification system (LFDCS) to autonomously detect and classify sounds of a variety of Arctic and sub-Arctic marine mammal species. The DMON/LFDCS reported regularly in near real time via Iridium satellite detailed detection data, summary classification information, and spectra of background noise. The spatial distributions of bowhead whale, bearded seal, and walrus call rates were correlated with surface salinity measured by the glider. Bowhead whale and walrus call rates were strongly associated with a warm and salty water mass of Bering Sea origin. With a passive acoustic capability that allows both archival recording and near real-time reporting, we envision ocean gliders will become a standard tool for marine mammal and ocean noise research and monitoring in the Arctic.

Journal of Physical Oceanography, 2002

... SeaWiFS measures chlorophyll a and water leaving radiances at six wavelengths (Hooker et al. ... more ... SeaWiFS measures chlorophyll a and water leaving radiances at six wavelengths (Hooker et al. 1992; McClain et al. ... Further details regarding the SeaWiFS instrument, calibration methodologies, and data processing can be found in Hooker et al. (1992) and McClain et al. ...

Journal of Geophysical Research, 2001

A new compilation of Lagrangian velocity observations describes the state of the North Atlantic s... more A new compilation of Lagrangian velocity observations describes the state of the North Atlantic surface circulation during the 1990s. Gridded fields of velocity and eddy kinetic energy (EKE) are constructed from trajectories of more than 1500 15-m drogued satellite-tracked surface drifters in service between January 1990 and December 1999. This time period overlaps a coordinated field study of circulation and variability in the North Atlantic completed between 1996-2000 as part of the World Ocean Circulation Experiment. We describe the construction of a self-consistent drifter climatology, present decadal-mean quasi-Eulerian velocity and EKE fields computed on a 1 ø grid, and compare these results with contemporary satellite measurements. Detailed discussion of the inferred surface circulation is focused on three regions: (1) The Gulf Stream and North Atlantic Current, (2) the Labrador Sea and subpolar gyre, and (3) the Caribbean Sea. The swiftest drifter motions were found in the equatorial region and along the tropical, subtropical, and subpolar western boundaries. The maximum instantaneous speed determined from a single (quality-controlled and filtered) drifter observation was 273 cm s -• in the Gulf Stream southeast of Cape Cod. The highest EKE value in the North Atlantic (2790 cm 2 s -2) was found in the Gulf Stream just downstream of the New England Seamounts. Over most of the Atlantic basin, drifter-derived EKE values were found to be O(100 cm 2 s -2) higher than corresponding values derived from satellite altimetry. In the Labrador Sea a region of sharply elevated EKE appears to be geographically related to the localized ejection of drifters (and by extension, mass and kinetic energy) from the energetic West Greenland Current between 60 ø and 62øN. When compared to drifter measurements made in the late 1970s our results suggest (but do not statistically confirm) an enhancement and slight northward shift of the zonal Gulf Stream extension. Such a shift is consistent in sign with expectations based on observed interdecadal variations in wind stress and subtropical gyre potential energy associated with the North Atlantic Oscillation. 1. Introduction Over the last 75 years, numerous investigators have attempted to describe and quantify the low-frequency circulation of the North Atlantic using an expanding collection of hydrographic profiles and direct velocity measurements. Notable among these efforts are the pioneering field studies of Iseh'n [1936] who elucidated the large-scale structure of the subtropical gyre and the Gulf Stream, and the syntheses of I4/orthington [1976] who quantified transports and tracer relationships throughout the North Atlantic. Recent synthesis efforts [e.g., Schmitz and Richardson, 1991: Schmitz and McCartney, 1993; Schmitz, 1995] have incorporated direct measurements of ocean velocities in an effort to refine estimates of the three-dimensional ocean circulation and illuminate transport pathways between the North Atlantic, its marginal seas. and the neighboring South Atlantic. Within the last 20 years, satellite-tracked Lagrangian drifters have emerged as an efficient means to explore upperocean circulation patterns independent of subsurface hydrographic measurements and the requisite (and sometimes difficult) choice of a geostrophic reference level. The number of drifter observations in the North Atlantic has increased sufficiently to enable a relatively high-resolution depiction of the basin-scale circulation and its variability. Of equal importance, the standardization of drifter design and drogue geometry [e.g., Sybrandy and Nillet, 1991: Nillet et al., 1995] has allowed the meaningful compilation of drifter trajectories measured at substantially different times enabling improved statistical confidence in the resulting circulation schemes.

Hydrobiologia, 2000

Seasonal and daily patterns of zooplankton populations are often predictable in natural lakes. Di... more Seasonal and daily patterns of zooplankton populations are often predictable in natural lakes. Distinct zonation and geomorphic differences in reservoirs, however, make ecological extrapolations from lakes to reservoirs uncertain. We describe the spatial and temporal distribution of zooplankton, algae, and water clarity across reservoir zones and along a depth gradient in Glen Elder Reservoir, Kansas. Daphnia species were most abundant in the lacustrine zone, with D. pulicaria numerically dominant in early spring and D. mendotae dominant later in 1999 and 2000. Rotifers (Keratella quadrata, Asplanchna spp.) were dominant in the riverine zone in 1999, 2000, and 2001. Algal biomass was not significantly different between zones through most of the sampling periods, except late April in 1999 and mid-April in 2000. Chlorophyll a exceeded 81 lg l )1 in the lacustrine zone in mid-to late-April in 1999 and 2000, and exceeded 90 lg l )1 in the riverine zone in mid-April. Water clarity was significantly lower in the riverine zone in 1999 and 2000.

The public reporting burden for this collection of information is estimated to average 1 hour per... more The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-01881, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information it it does not display a currently valid OMB control number.

Deep Sea Research Part II: Topical Studies in Oceanography, 2009

Prediction is very difficult, especially about the future.'' Origin disputed but often attributed... more Prediction is very difficult, especially about the future.'' Origin disputed but often attributed to physicist Niels Bohr.

An underwater glider is a buoyancy-propelled, fixedwing vehicle with attitude controlled complete... more An underwater glider is a buoyancy-propelled, fixedwing vehicle with attitude controlled completely, or in part, by means of internal mass redistribution. We have developed a physics-based nonlinear model of the dynamics of an underwater glider and adapted it to model the SLOCUM glider's geometry, rudder, ballast pump and internal movable mass. In this paper we identify the model parameters to match the steady glides in new flight test data from the SLOCUM glider. In the process we also estimate the buoyancy trim offset of the glider used in the flight tests.

Our primary long-term objective is to better understand the physical and biological mechanisms of... more Our primary long-term objective is to better understand the physical and biological mechanisms of formation and maintenance of thin layers of zooplankton. Because zooplankton can be strong sound scatterers, acoustic instruments are effective at detecting and describing zooplankton thin layers. Using a combination of instruments (acoustics, image-forming optics, ADCP's, CTD's, and bio-optical sensors) and sampling platforms (a fleet of gliders and a profiling package), we plan to determine the temporal and spatial scales of acoustic backscatter from zooplankton aggregations, the taxonomic and size composition of the zooplankton in such layers, and the associations of zooplankton thin layers with physical parameters. To do this, it is imperative that we understand the factors influencing the frequency dependent backscatter from the organisms. In particular, the orientations of the plankton relative to the acoustic source can have significant effects on the resultant backscatter. Hence, a

The Autonomous Ocean Sampling Network-II (AOSN-II) and Adaptive Sampling And Prediction (ASAP) pr... more The Autonomous Ocean Sampling Network-II (AOSN-II) and Adaptive Sampling And Prediction (ASAP) projects aim to develop a sustainable, portable, adaptive ocean observing and prediction system for use in coastal environments. These projects employ, among other observation platforms, autonomous underwater vehicles that carry sensors to measure physical and biological signals in the ocean. The measurements from all sensing platforms are assimilated in real-time into advanced ocean models. The objective is to coordinate the mobile assets in order to collect data of highest possible utility. Critical to this effort are reliable, efficient and adaptive control strategies to enable the mobile sensor platforms to collect data autonomously. In this paper, we summarize feedback control strategies that enable us to gather useful information over a wide spectrum of spatial and temporal scales. First, we design formation control strategies useful for sampling small spatial scale processes (less than 5 km). In this framework, the feedback control laws maintain a desired formation of vehicles and allow the group to locate interesting features in the ocean. Some of these control strategies were implemented on a group of underwater gliders in Monterey Bay in August 2003, as part of the AOSN-II project. Second, we direct mobile sensor networks to provide synoptic coverage to investigate larger scales (5−100 km). Coordinated vehicle trajectories are designed according to the spatial and temporal variability in the field in order to keep sensor measurements appropriately distributed in space and time.