Charles Eriksen - US grants

This ongoing research program is organized into three distinct but related areas. The general aim of the first area is to elucidate and describe selective attentional mechanisms as they operate in visual information processing. Ongoing and proposed research is directed toward attention effects at early levels in stimulus processing, stimulus selection and the role of competing responses, sustained attention, and the spatial characteristics of the distribution of attentional resources in the visual field. Among the methodologies used, response competition paradigms, cost benefit analysis, and reaction time measures play a major role. A second area of research is to refine a new set of measures that analyze the microstructure of the responses that are used to signify choice in reaction time tasks. In recently completed pilot studies, these measures have shown high promise of reflecting differences in information processing that are not revealed in the usual latency measures. A third research direction uses a response competition paradigm to determine the extent and nature of the relationships and content that is retrieved upon semantic processing of a word.

Professor Eriksen's research laboratory is funded by NIMH grant MH 01206 and by a grant from the University of Illinois Research Board. The NIMH grant MH 01206 is currently in the twenty-sixth year of funding and as an indication of the quality and the importance of this research as evaluated by his peers, the last two renewals received priority ratings of 100 and 108 by the study section. Current experimentation in his laboratory is primarily oriented toward explicating the mechanisms involved in selective attention, to exploring further response competition effects, and to refining and extending his continuous flow model of visual information processing. During this past year two important papers have been completed that explain some of the major phenomena in same-difference judgments in terms of response competition effects. The response competition paradigm which was discovered and developed in his laboratory has been increasingly used by other investigators to attack a variety of cognitive problems, and the continuous flow model is increasingly cited as one of the leading theories of visual information processing.

This project has constructed three Profiling Current Meters and deployed them as part of the TROPIC HEAT moored Intensive Array (Dec 1984-July 1985). Data from these deployments is being analyzed to understand equatorial wave- mean flow interaction at low frequencies and the statistics of shear and stratification fluctuations in relation to mean Equatorial Undercurrent structure at high frequencies.

This project is a component of a coordinated study called the Tropical Instability Waves Experiment (TIWE). The P.I. will deploy an array of four current measurement moorings, centered at about 4 deg N, 140 deg W. These moorings will be instrumented with Profiling Current Meters (PCM), which cycle through a specified depth range, and are capable of measuring profiles of near-surface currents, as well as temperature and salinity, with a high degree of vertical and temporal resolution. In collaboration with other TIWE components, and existing NOAA current and temperature moorings, the P.I. will attempt to calculate balances of momentum flux, Reynolds heat flux convergence, energy production by barotropic instability, and background current upwelling. Information on background mean currents will also be analyzed in terms of annual variability.

This ongoing program of research on human visual information processing is currently concentrating on elucidating and describing visual selective attentional mechanisms. This empirical knowledge is a necessary first step in the development of a comprehensive model of attention. Specific issues addressed in the present proposal are: 1) the degree of processing of nonattended stimuli; 2) negative priming and the degree to which selection depends upon active suppression of irrelevant stimuli; 3) whether focal attention has a minimal channel size; 4) whether focal attention is best conceived as unitary and constant or as comprising different levels; and 5) the spread or distribution of attention in the visual field. Many of the methodologies employed in the research make use of procedures and paradigms that we have developed in our laboratory such as precueing, response competition and stimulus substitution. In certain multi-variate experiments electromyographic recordings and evoked brain potentials are used along with measures of response latency and accuracy. We will also employ measures based upon the microstructure of simple responses such as lever movements that the subjects use to signify their choices or decisions. Past work in our laboratory has shown the value of these micro responses in revealing processing differences that are not apparent when only RT or accuracy is looked at.

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Eriksen

This research project is conducted under the auspices of the National Oceanographic Partnership Program (NOPP). Partners include the Univ. of Maine, Univ. of Washington, several commercial instrument manufacturers, and two local government agencies. The project addresses an ocean sciences requirement for new ocean observational capabilities for continuous, high-resolution measure-ments of oceanic processes that include characterization of distributions, mechanisms, and rates of processes involving chemical and biological variables together with physical variables in the ocean. The overall objective is to add new capabilities to a small (1.8 m, 52 kg) autonomous underwater glider that moves horizontally and vertically using variable buoyancy control and wings. It can perform hundreds of cycles per launch from surface to 2,000 m or less, report data back (including GPS location) in real time upon each surfacing, and be reprogrammed from shore. New sensors will be developed and integrated into the system for dissolved oxygen and various inherent optical properties of seawater, all measured at the same time and space scales as physical properties. The project encompasses development of new sensors, miniaturization of several extant sensors and extensive field tests. The research team includes industrial partners, local governments working on practical societal/scientific issues; biological, physical and optical oceanographers; and an education effort from 8th grade through graduate school.

The specific goals of this project are:
- to extend development of an autonomous, underwater glider to be capable of measuring biological, optical, physical and chemical variables on the same time and space sales, in real time, and in diverse environments;
- to develop small, light-weight, low-power sensors for measuring dissolved oxygen, inherent optical properties (IOPs) of seawater, chlorophyll a fluorescence (the primary surrogate for phytoplankton biomass), and other fluorescing compounds;
- to verify with ground-truth measurements the high quality data collected by the glider;
- to demonstrate the glider's capabilities for real-time, data-adaptive sampling;
- to enhance understanding of the dynamics of key physical and biological parameters in Puget Sound that are essential to assessing human impacts on water quality;
- to demonstrate the glider's ability to significantly improve validation of satellite ocean color data by sampling at the appropriate scales; and
- to engage undergraduates and graduate students in engineering tests and research applications.

The newly developed optical sensors for IOPs and chlorophyll a fluorescence would be easily adaptable to other platforms, and hence be easily and rapidly available to the general oceanographic community. Also, the glider will be able to operate in areas beyond Puget Sound including both coastal and open-ocean environments.

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This project is aimed at demonstrating the effectiveness of gliders to observe boundary currents and describe an annual cycle of eastern boundary current evolution at the terminus of the West Wind Drift. Seagliders are small, reusable autonomous vehicles designed to glide from the ocean surface to as deep as 200 m and back while collecting profiles of physical, chemical and bio-optical properties. Two Seagliders will be deployed in successive missions up to 7.5 months long off the Washington coast to resolve the seasonal cycle of the California/Alaska Current system. All the data, about a thousand profiles of temperature and salinity will be transmitted in near-real time so that the progress of the gliders and current oceanic conditions can be monitored. Oxygen and bio-optical sensors will also be on the gliders. The work proposed is intended as a step forward toward learning to observe boundary currents over long time periods.

The focus of this five-year program is to assess the seasonal and interannual physical and biological variability of the Alaska Coastal Current (ACC). Specifically the PIs will investigate the seasonal and interannual variability in ACC freshwater content and transport, the ACC's role in governing spring-time mixed layer evolution over the shelf, processes controlling temporal and spatial variability in the spring bloom, and processes that may produce onshore nutrient flux. These processes are inherently three-dimensional and exhibit a wide range of temporal scales. To address these sampling requirements, this program will exploit the capabilities of a new, autonomous, telemetering vehicle (Seaglider) to make continuous, high-resolution sections of the ACC. Seaglider measures temperature, conductivity, pressure, chlorophyll fluorescence, dissolved oxygen and volume scattering function, profiles from the surface to within 10 m, of the bottom and provides 2 km horizontal resolution. The vehicle will operate year-round, repeating a sampling pattern designed to provide five sections across the ACC every twenty days. The sampling strategy was designed to augment existing GLOBEC Long Term Observation Program components. The temporal and spatial resolution provided by Seaglider surveys will resolve processes such as springtime restratification and phytoplankton blooms, while the multi-year extent of these observations will explore the system's response to long timescale perturbations in forcing.

ABSTRACT

OCE-0223372

Experimental evaluations of the organic carbon export from the euphotic zone of the ocean are essential for verifying and calibrating estimates of the ocean's biological pump by both satellite color and Global Circulation Models. Studies of upper ocean oxygen mass balance have shown that carbon export from the euphotic zone can be accurately estimated by determining net annual biological oxygen production at locations where there are time-series measurements. Growing awareness of the present importance of nitrogen fixation in the subtropical North Atlantic and Pacific Oceans has lead to the suggestion that ocean productivity, and perhaps the organic carbon export, in these areas is limited by the wind blown flux of iron to the surface waters. One could evaluate the importance of this process in the subtropical ocean without the expense of an iron fertilization experiment by determining the net biological oxygen production in locations that receive very different atmospheric loading of iron. The ideal locations to contrast in this regard are the North and South Pacific Ocean; however, it has not been possible to carry out a time-series study south of the equator in the Pacific because it is too remote. The advent of glider technology and the evolution of our ability to quantify air-water gas exchange in the subtropical oceans make it now possible to study the oxygen mass balance by remotely measuring the T, S, and O2 concentrations in the upper ocean. In this study, investigators at the University of Washington will develop this new technology to determine the net biological oxygen production in the North and South Pacific. The subtropical oceans are ideal for introducing a glider study of upper ocean heat, fresh water and oxygen budgets because the relatively steady and slow surface currents.

Specifically, the goals of this research are to demonstrate the utility of gliders to determine accurate and precise T, S and O2 concentrations in the open ocean from which budgets can be calculated and to contrast the net biological oxygen production in the North and South Pacific subtropical gyres. The research team will carry out glider surveys of the upper ocean at the Hawaii Ocean time series (HOT). The team will calibrate instruments on the glider against monthly measurements by the time-series scientists so that it will be possible to verify accuracies and make adjustments to improve results.

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Intellectual Merits:
This project will continue to observe and understand the physics and biology of the highly productive northeast Pacific boundary current region over the continental slope off Washington and Oregon - the Cascadia slope - with an autonomous, sustained presence. For over a year, Seagliders, long-range autonomous underwater vehicles, have been deployed to survey the temperature, salinity, dissolved, oxygen, chlorophyll fluorescence, and optical backscatter structure of the slope off. Washington. Seagliders have collected data on sections from the continental shelf edge offshore 220 km at fortnightly intervals, reporting back data after each dive, on deployments typically lasting 4-5 months. The objective of the observations has been to detect seasonal and inter-annual variability in this part of the California Current system by collecting highly spatially and temporally resolved observations. Using Seagliders makes possible extended high resolution observations that would otherwise be prohibitively expensive if carried out by ships. This three-year project will: 1) analyze more than 16 months of Seaglider observations already collected, 2) continue the Seaglider observational program to over the continental shelf, and 3) analyze the newly collected data to describe the seasonal and interannual structure of the northern California Current system. Extension in time over the existing Seaglider repeat transects is necessary to confidently describe seasonal and interannual variability in the Cascadia slope region and to resolve and understand the (primarily advective) processes that are responsible for this variability. The data in hand offer tantalizing hints at the low frequency variability, but the 1.5 year record along two cross-slope sections is too limited to support quantitative understanding.

Broader Impacts:
The results from this project will improve physical and biological understanding of climate change. By autonomously measuring important oceanographic parameters over a sustained period of time, it will be possible to establish an unprecedented climate record in an economically important area. By expanding the spatial coverage of the autonomous transects, we will be able to resolve and understand the contribution of advection. The results of this project will benefit resource planners by helping to understand the coastal zone ecosystem and influences of large scale ocean circulation on coastal and estuarine conditions in the Pacific Northwest. We will continue our outreach activities with presentations to local schools, open houses, public talks, and contacts with print and electronic media on local, national and international levels.

The scientific goal of the project is to document and understand the seasonal and interannual variability of both Atlantic inflow to and deep overflow from the Nordic Seas over the Iceland-Scotland Ridge, a region where meridional overturning circulation deep branches are formed and important shallow branches concentrate. Currently, the most reliable estimates of exchange across the Iceland-Scotland Ridge are based on currents and hydrography sampled with different spatial and temporal resolution, with different techniques, and with debatable values for reference temperature and salinity. The detailed spatial structure and seasonal and interannual variability of circulation in this region has yet to be resolved. In the context of global climate change, decline of the meridional overturning circulation is widely predicted. Climate models are very sensitive to these transports and resolution of them is crucial to understanding ocean climate variability, past, present and future. New observations (primarily physical) will be used to infer entrainment sites and to quantify transports by water mass type for use in improving climate models, whose predictions under global warming are sensitive to the physics of the high-latitude ocean. The intense biological productivity of the region, which depends on these circulations and water masses, will also be profiled optically. Long-range autonomous underwater vehicles (Seagliders) will be used to collect full-depth hydrography and estimate absolute geostrophic velocity sections simultaneously of both shallow northward inflow and dense southward overflow across the Iceland-Faroe Ridge and the Faroe-Shetland Channel. This domain is thought to account for about 90% of the Atlantic transport poleward and about half of the deep water transport equatorward (the remaining portion passes through the Denmark Strait). Seagliders will collect high-resolution sections of temperature, salinity, dissolved oxygen, fluorescence and optical backscatter as well as depth-averaged horizontal velocity. The sections will resolve seasonal variations and begin to detect prominent interannual variations. One Seaglider will traverse the Faroe-Shetland Channel weekly while a pair of Seagliders will survey the southwestern flank of the Iceland-Faroe Ridge, repeating a ~1000 km track monthly. The vehicles will be deployed in 4-month missions continuously for 3 years, using vessels in the Faroe Islands for launch and recovery. The plan is to collect about 30,000 full-depth (500-1000m) profiles with 3-6 km horizontal resolution across nearly 60,000 km of track during the three year project, all delivered in near real-time via satellite. Real-time command of the Seagliders will allow mapping of finescale water masses and frontal features. The observations will be carried out in conjunction with mooring/ship observations of on-going projects, and with Norwegian, Icelandic and Faroese collaborating scientists The study is a contribution to the U.S. CLIVAR (CLImate VARiability and predictability) program..

Intellectual Merit. The most basic dynamic balances of the global overturning circulation of the oceans are under debate. Global change may alter the overturning circulation and with it, global climate and ecosystems. High resolution climate observations with radically new platforms, sustained in time, can guide the numerical climate models which are increasingly relied upon in matters of policy and planning

Broader Impacts. Beyond physical science, this work relates to ecosystems in one of the most biologically productive sites on Earth, and a region of strong uptake of carbon from the atmosphere. The work will provide bio-optical profiles and sections at high resolution in regions of unusually high biological productivity. The interdependence of fisheries and physical oceanography in this region is extremely strong, as primary productivity is associated with buoyant, low-salinity layers which trap phytoplankton. The research contributes to our undergraduate teaching in environmental studies, in which the methods and results of science are put before young students who are the beneficiaries and custodians of the environment.

The annual CO2 flux into the ocean north of 14 degN in the Pacific is about equal to the annual flux to the atmosphere from the Equatorial Pacific (14 degN to 14 degS). The strongest region of CO2 uptake in the north Pacific is at the subtropical subarctic front. Although thermodynamic processes primarily control the air-sea CO2 flux in the subtropics, biological and physical mechanisms are much more important at the front and in the subarctic Pacific. Based on current understanding, it is uncertain whether alterations to these physical and biological processes in response to climate change could transform the north Pacific into a stronger source or even into a sink for anthropogenic CO2.

In this research, PIs from the University of Washington and Oregon State University, in close collaboration with scientists from NOAA's Pacific Marine Ecosystems Laboratory, will conduct field studies combined with satellite observations and a modeling investigation to identify the mechanisms controlling the air-sea CO2 flux at the subtropical subarctic front and in the eastern basin of the subarctic Pacific. The field studies comprise three separate components: (1) measurement of pCO2 and oxygen isotope tracers of biological productivity (delta17O, O2/Ar) using a Volunteer Observation Ship (VOS) that crosses the Pacific every other month; (2) determination of carbon fluxes and depth distributions not possible from a VOS using a research cruise between Hawaii and Seattle, and (3) in situ, continuous measurement of T, S, O2, chlorophyll, pCO2 and pH on a surface mooring in the eastern subarctic Pacific at Ocean Station P while simultaneously measuring the four dimensional distribution of T, S, and O2 using a Seaglider survey of the area. These autonomous measurements are focused on identifying the role of intermittency in the biological pump. The field observations will be placed in context by a study of satellite products that identify the role of intermittent forcing (e.g. sea-surface height, atmospheric dust levels) and subsequent productivity events (e.g. ocean color, coccolithophorid blooms). A circulation model of the north Pacific that includes modules for the biological ecosystem and the carbonate chemistry will be combined with the field and satellite data to help distinguish the importance of physical and biological processes in controlling the pCO2 of surface waters at the frontal region.

The most obvious broader impact is the participation of 10 - 15 undergraduate and graduate students on a research expedition between Hawaii and Seattle as part of a course for students of Oceanography at the University of Washington. This research will also support two and one half graduate students who will use the data derived here to complete their Ph.D. research. A greater understanding of carbon cycling in this critically important regime will provide societal benefits.

This project is funded as an EArly-concept Grant For Exploratory Research (EAGER).

The Rapid Climate Change-Meridional Overturning Circulation and Heat Flux Array (RAPID-MOCHA) began monitoring meridional mass transports in the North Atlantic Ocean along a transatlantic section from North America to Africa in 2004. It estimates the climatically critical meridional overturning circulation (MOC) by differencing dynamic height profiles gathered from small clusters of moorings on either side of the Atlantic basin, measuring boundary current flows with current meters, measuring transport in the Florida Strait electrically, and using satellite winds to estimate Ekman transport. While bottom pressure gauges are used to estimate time-varying barotropic contributions, RAPID-MOCHA relies on an assumed spatially uniform temporally constant barotropic flow to estimate mean transport.

The first scientific use of the newly developed full-ocean-depth (surface to 6 km) autonomous underwater glider, Deepglider will complement the RAPID-MOCHA array. Deepgliders will be used to estimate absolute transports independently of RAPID-MOCHA by collecting repeat hydrographic sections of the extended western boundary region off Abaco, Bahamas. A pair of vehicles will repeatedly transit across 100 and 500 km wide overlapping sections between end members of the RAPID-MOCHA dynamic height moorings. These sections will be repeated about weekly and monthly, respectively, by Deepgliders, providing substantial spatial resolution compared to that provided by the moorings, although at considerably coarser temporal resolution. Each Deepglider is expected to last well over 1 year, possibly up to about 18 months. Integrated geostrophic shear inferred from horizontal density gradients resolved in the sections will be referenced to depth-averaged current inferred from each glider dive cycle. The difference between dead-reckoned glider displacement through the water and GPS displacement over the ground is used to estimate depth-averaged current. The Deepglider estimates will include the likely possibility of horizontally varying time-mean barotropic contributions to transport. The independent Deepglider estimates of transports will be compared to those from the RAPIDMOCHA array.

In addition, Deepgliders temporarily will be used in 'virtual mooring' mode to check the adequacy of the moorings in measuring dynamic height. Together, the complement of repeat section and moored time series will be used to assess errors and improve estimates of meridional transports in the extended western boundary region.

Intellectual Merit: The intellectual merit of this work lies in its connections to basic issues of global climate dynamics. The variability of the MOC is not well observed, let alone understood. The same can be said for the deep flow. Comparison of techniques by which the MOC is monitored is essential to establish their credibility and effectiveness. Deepglider repeat hydrography will provide independent measures of climatically critical ocean circulation transports, the western boundary contributions to MOC. Resolution of the temporal/spatial structure of western boundary currents is prerequisite to understanding how this portion of the climate system operates.

Broader Impact: This project will serve as a demonstration of efficacy and economy of full-depth gliders in monitoring ocean circulation not only along the RAPID-MOCHA line, but also along other transects. It will pioneer the use of autonomous gliders to monitor not only the upper ocean, but its deep regions as well. Currently Argo floats monitor the upper ocean globally, but the deep ocean is severely under-observed for climate change, a situation Deepgliders could alter. By making deep ocean access affordable, the Deepglider technology opens the possibility that the complete extent of global ocean climate change may be observed.

The northern Atlantic Ocean, near the seafloor ridge between Greenland and Scotland, is a particularly active part of the global climate system. This project will analyze observations from a recently completed 3-year program of Seaglider deployments in this sub-polar region. It is the first time that robotic gliders have been used to observe the dense overflow waters of the global meridional overturning circulation, and with them the warm northward flowing branch of the AMOC (Atlantic Meridional Overturning Circulation). 17,800 profiles of hydrography, dissolved oxygen, bio-optical variables and depth-averaged velocity were retrieved in 23 successful deployments during this NSF-sponsored work from November 2006 to November 2009.

The primary foci of the proposed work are (i) an analysis of the water masses involved in the deep branch of the AMOC, the polar front and warm branch of the AMOC at this site, (ii), a study of mixing, dense-water transformation, and internal waves inferred from glider profiles of vertical velocity, optical backscatter, temperature and salinity at 1m vertical resolution, and (iii) an analysis of horizontal velocity using glider depth-averaged velocity, geostrophic shear and satellite altimetry, emphasizing dense overflow plume structure, polar front structure, and vertical structure of the strong eddy field.

This new observational dataset will be combined with historical hydrographic sections, gridded climatology and with models of the Atlantic circulation. The statistical strength of the new data lies in the multiple occupations of the southern slopes of the Iceland Faroe Ridge over 3 years. Top-to-bottom profiles of horizontal velocity normal to the sections are recovered from the hydrography and glider-measured depth-averaged horizontal velocity. The new measurements of fine-scale vertical velocity by the gliders are particularly exciting. "Hot-spots" of turbulent mixing are visible throughout the water column, but particularly intense in the dense overflow water plume near the exit of the Faroe Bank Channel. Complementary observations from moorings and lowered turbulence probes have been made by Norwegian colleagues. Fine structure of temperature and salinity and optical backscatter observed at the 1m scale will be related to the vertical-velocity mixing signature. In parallel laboratory experiments have been investigating mixing induced by flow over seafloor topography. Together, these observations will provide a significant coverage of eddies, water masses, circulation and mixing in an important sector of the global climate system.

Intellectual Merit: Human-induced global climate change is accelerating, and yet the natural variability of climate is strong and difficult to predict. Multi-decadal variability of the AMOC is being advanced as a contributor to the rapid late 20th Century global warming, which is largely thought to be driven by greenhouse gases. While climate models are centerpieces of the global warming/climate change debate, it is widely acknowledged that these models (and indeed higher resolution ocean circulation models) are deficient in representing dynamics in these key high-latitude regions. It is necessary to make direct observations of mixing, sinking, water-mass transformation, topographic control and boundary layers. These need to be targeted, and dense in space and time, which is the virtue of gliders. The motivations for this work go back through many years of research with theoretical dynamics of the ocean, which guide the analysis of observations.

Broader Impacts: The investigators on this project interact with students through detailed research with graduate students to undergraduate teaching about the global environment. A key argument made to undergraduate students is that scientific technology has reached the point where it can contribute more effectively in assessing environmental problems. This project will foster on-going collaborations with oceanographers in Norway and the Faroe Islands interested in climate issues affecting sustainability of fisheries, dislocation of ecosystems and the precarious nature of human communities at the rim of the Arctic. Seagliders can be applied widely to address such issues as biological productivity and ecosystem change. The links between countries at the rim of the Arctic are strengthened by growing collaborations in climate- and environmental sciences.

This project is a contribution to the US AMOC (Atlantic Meridional Overturning Circulation) project of the CLIVAR (CLImate VARiability and predictability) program.

Intellectual Merit: One of the largest outstanding and ongoing research problems in the physical and biogeochemical oceanographic community concerns the fate of organic carbon generated from primary production in the surface ocean. Though carbon export exerts a profound control on CO2 concentrations in the world?s atmosphere, in-situ measurements of production rates are not fully reconciled with those inferred from the global annual average, and the spectrum of variability of carbon export in a variety of oceanic environments has yet to be fully determined. A popular method for evaluating ocean metabolism is the formulation of an oxygen mass balance, in which an oxygen budget is constructed in the mixed layer or euphotic zone, the effects of physical processes are removed, and the residual oxygen production is stoichiometrically related to the export of carbon to depth. While ship-based oxygen mass balance studies are hindered largely by expense and the availability of resources, recent efforts using remote measurement of oxygen from moored sensors display considerable potential for cost-effective and geographically widespread diagnostics of the biological pump. These techniques have been expanded to mobile autonomous platforms such as profiling Argo floats and ocean gliders, which offer an enhanced, highly-resolved vertical and horizontal picture of major physical processes controlling primary production.

Continuing the evolution of studies of net biological oxygen production from autonomous platforms, the project will apply a comprehensive physical and oxygen mass balance assessment to a remote-sensing time series of unprecedented duration and resolution: the University of Washington Seaglider Ocean Station P time series in the southern Gulf of Alaska. Three separate Seaglider deployments orbited the well-instrumented National Oceanic and Atmospheric administration Pacific Marine Environmental Laboratory (NOAA/PMEL) Station P mooring from June 2008 to January 2010, collecting detailed vertical and horizontal profiles of basic physical properties, bio-optical variables, and dissolved oxygen. During extended portions of this time, the Station P mooring observed atmospheric variables and corresponding physical parameters within the near surface ocean; taken together these datasets represent a powerful tool for adding to the established picture of physical variability and net oxygen production in the central subarctic Pacific Ocean. In the course of our proposed analysis, we hope to: 1) better constrain horizontal advection, vertical advection, and diapycnal mixing processes, as they apply to the budget of an active tracer; 2) obtain a robust estimate of net oxygen production in the mixed layer during the course of the time series; 3) evaluate respiration (oxygen consumption) below the mixed layer and above the permanent halocline; and 4) estimate the dependence with depth of respiration below the pycnocline.

Broader Impacts: This project will expand the knowledge base of the physical dynamics controlling the biological pump in the Gulf of Alaska as well as add to the length of the time series which has been analyzed in a carbon export context. A better understanding of advection in the surface layer would allow comparison to previous residual estimates of this term and its relative importance at each phase of the seasonal cycle. Exploring the dependence in time and depth of diapycnal diffusivity would improve and clarify our knowledge of its role in vertical transport of oxygen at Station P. Additionally, analysis of a combined moored and autonomous vehicle time series should provide a foundation of techniques to be used in similar future deployments in difficult-to-observe regions of the world ocean.

This project will carry out further development and testing to bring the advanced prototype for a full ocean depth capable glider to the stage that it can be used for scientific investigation. Deepgliders are designed to dive to as deep as 6 km and return to the sea surface about 250 times in a single mission lasting as long as 18 months and traveling as far as 10,000 km through the ocean. They sample temperature, salinity, and dissolved oxygen along sawtooth paths through the ocean and communicate them to shore via satellite telemetry. Two-way communication allows commands to be transmitted so that autonomous behavior can be controlled remotely from a pilot anywhere with an internet connection. The projected operational cost of each slanting full depth profile is ~$120, almost two orders of magnitude less than what a deep ocean hydrographic cast costs (although deep casts generally measure many more variables). Deepgliders offer sampling persistence and frequency that is unmatched by ships. Their mobility and remote control enables spatial description of the ocean's internal structure that would require an underwater forest of moored sensors to match. Their economy can be exploited to observe the deep ocean far more intensively and extensively than is possible with conventional methods so as to answer fundamental questions about ocean circulation, the role of the ocean in climate, boundary current systems, and omnipresent mesoscale eddies.

Three Deepgliders capable of diving to 6 km depth have been constructed to date, two of which have been lost in a total of 5 trial deployments in the tropical Atlantic in the past year. One was adrift at the sea surface with communication difficulties when lost in a mission that had sampled only the upper ocean, while effects of high pressure may not be ruled out in the other loss. Deepglider has reached 5920 m depth, executed a 275 km section to 5250 m depth, used energy at a rate that implies 18 month missions are feasible, and measured temperature and salinity with resolution and stability comparable to what is attained with CTD casts.

The purpose of this project is to improve the reliability of Deepglider so that it can achieve design mission endurance and range goals, evaluate the stability and accuracy of its measurements, and develop it into a credible tool for oceanographic research. Several new Deepgliders are to be constructed and used in an extensive program of both laboratory and field tests. Results from a staggered sequence of tests on the currently available Deepglider and the first of the new units will be used to modify the design of the subsequent units. Laboratory tests will include intensive pressure cycle tests of hull integrity and buoyancy engine performance. Field tests will take place at a deep ocean time series site for logistic convenience and the availability of regular high quality shipboard and moored measurements for comparison, most likely the Hawaii Ocean Time-series Study (HOTS) site or the Bermuda Atlantic Time-series Study (BATS) site.

Intellectual Merit: This project will bring to readiness a technique that will extend autonomous underwater glider depth range to the water column entirety in nearly the entire ice-free open deep ocean, endurance to more than one year, and horizontal range to 10,000 km. These improvements by factors of 2-6 over present technology are projected to accompany reductions in glider usage cost and only a modest (~25%) increase in glider fabrication cost.

Broader Impact: The transition of Deepglider from advanced prototype to reliable oceanographic tool will enable extensive, relatively frequent sampling of the deep ocean?s temperature, salinity, oxygen, and current structure. Affordable means to sample the water column will advance knowledge of ocean circulation and the ocean?s role in climate. The technology will invite the development and addition of other sensors to Deepglider as a versatile platform for ocean observation. It will also lead to commercialization and widespread use of such vehicles.

This is a project to study the decay of a subthermocline eddy as it travels from near its generation site in the California Undercurrent (CU) over the continental slope into offshore waters. The CU, a prominent element of the California Current System (CCS), transports relatively warm, saline, anoxic Pacific Equatorial Water north along the North American west coast. Temperature and salinity generally decrease both poleward and offshore, while dissolved oxygen increases, as the CU spins off long lived eddies transporting its water properties away from the CCS into the eastern Pacific. These eddies, nicknamed cuddies for their origin, have been tracked by solitary floats for many months and surveyed hydrographically on occasion, but their structural evolution as they decay has yet to be observed. They take the form of submesoscale coherent vorticies and are largely invisible to remote sensing techniques due both to their small size and subsurface intensification. The extent to which cuddies contribute to broad scale property gradients in the CCS and beyond is tied to the evolution of their radial-vertical structure.

This study will use a pair of extended-range Seagliders to frequently survey a cuddy over many months as it travels. A cuddy will be identified and located for study by an ongoing Seaglider repeat transect, separately supported by NOAA and maintained by University of Washington colleagues. With improvements to performance efficiency, Seagliders are projected to be capable of operating as long as a year while transmitting slanting profiles of upper-ocean structure ashore in near real time. Simultaneous transects at 4-6 km resolution along nearly perpendicular paths repeated every week or less over the course of ten months appear feasible, with an additional two months of mission time devoted to reaching from and returning to the coastal region for launch and recovery. The sequence of approximately 50 three-dimensional surveys of a cuddy will be used to observe its decay rate, associated frequency and intensity of fine scale stratification features, and changes in vertical-radial structure.

The observed structural evolution of a subsurface eddy will be used to infer the exchange rates of physical, chemical, and biological properties with the surrounding waters. While cuddies are widely suspected to be important agents of property exchange in the CCS, the observations proposed will be the first to describe a cuddy in four dimensions over an appreciable portion of its lifetime.

This study will contribute to understanding of eddy transport in general and the role of submesoscale coherent vorticies in particular in transmitting eastern boundary region properties to the ocean interior. Implications of eddy transport are important not only to physical distributions in the ocean, but to chemical and biological ones as well. The project will train a graduate student to be expert in an emerging observational technique as well as in the role of eddies in ocean circulation.

The Atlantic Meridional Overturning Circulation (AMOC) is a principal element of the global climate system. At 26.5 degrees North latitude, the AMOC is responsible for carrying about sixty percent of the net poleward heat flux carried by the oceans and about thirty percent of the total heat flux carried by the atmosphere and ocean together, integrated zonally around the globe. Through sea surface temperature modulation, the AMOC is linked to climate signals on interannual to multi-decadal time scales that can have extensive societal impact. Climate models predict substantial weakening of the AMOC over the next century, a change with potentially wide ramifications. For the past decade, U.S. and U.K. scientists have maintained a transatlantic heavily instrumented moored array to observe fluctuations in the AMOC and its heat flux. Variability on time scales longer than ten days is dominated by geostrophic current fluctuations inferred from transatlantic dynamic height differences and boundary current fluctuations. While effective, the moored array is costly to maintain. This project is an attempt to assess the effectiveness of very long-range full ocean depth underwater gliders in measuring aspects of the AMOC side-by-side the moored array. These autonomous vehicles, named Deepgliders, collect sea-surface to sea-floor profiles of temperature, salinity, and dissolved oxygen along slanting trajectories through the ocean in near-real time. They also return estimates of the full-depth average current. Successful application of Deepgliders to the 26.5 degrees North latitude line will motivate applying the technique to other transects of interest (such as in the North Atlantic subpolar gyre and the South Atlantic subtropical gyre), to address the challenges of repeat hydrography globally, and reduce the overall cost of such programs in order that such ocean climate projects can be afforded as a whole by funding agencies. These together will lead to deeper understanding of earth?s climate.

The overall goal of the project is to learn how to assist the sustainable continuation of AMOC monitoring through coming decades. Learning to measure the AMOC using Deepgliders will help sustain operation of the current array at 26.5 degrees North for the many decades required to resolve interannual and multi-decadal variability. Only by operating for several decades will the signals associated with natural climate variability and anthropogenic climate change be evident and potentially distinguishable. A Deepglider is designed to make about 250 dives to as deep as 6000 m in missions lasting as long as 18 months while traveling as much as 10,000 km through the ocean on a single set of lithium batteries. It samples temperature, salinity, and dissolved oxygen along saw tooth paths through the ocean and communicates them to shore each time it reaches the sea surface via satellite telemetry. Two-way communication allows commands to be transmitted to Deepgliders so that its autonomous behavior can be controlled remotely from a pilot anywhere with an internet connection. As a pilot experiment, four one-year Deepglider missions are planned over a 2-year period overlapping moored deployments. Two of these will concentrate on maintaining position close to a RAPID-MOCHA mooring just offshore Abaco, Bahamas to resolve the principal variability in dynamic height for use in estimating the interior ocean contribution to AMOC variability. Two more will repeat a short section intended to capture temporal and spatial variations in Antilles and Deep Western Boundary Current flow. Deepglider and moored measurements will be compared to assess relative efficacy.

Appreciation that the ocean is full of eddies on a vast array of scales began with the discovery of what are commonly referred to as mesoscale eddies: those with horizontal scales of order tens to about 100 km. These eddies are geostrophic (a state where the pressure gradient force from density gradients is in balance with the Coriolis effect from the rotation of the earth) in contrast to meteorological eddies like tornadoes which are significantly ageostrophic. Because they are the most energetic features of oceanic motion, understanding how these geostrophic eddies work is key to understanding and predicting circulation, the distribution of properties, and biomass in the ocean. Testing theories of geostrophic turbulence will stimulate new work to better understand oceanic states in the past and to predict their future. Laws for the dependence of energy wavenumber spectra implied by geostrophic turbulence were proposed on theoretical grounds half a century ago. These distinguished between an inverse cascade transferring energy to larger scale and a forward cascade transferring enstrophy (the energy of rotating motions) to shorter scale. While the existence of an enstrophy cascade has been identified in spectra of trophospheric wind observations, evidence supporting such a cascade in the ocean is scant and contradictory. Recent observations of the depth structure of current and vertical displacement at the Bermuda Atlantic Time Series (BATS) site seem to confirm the scaling predictions for both the inverse energy and forward enstrophy cascade portions of the wavenumber spectrum. These preliminary observations will be extended and generalized by sampling four new sites with distinct eddy energy and latitude regimes. This project will train a graduate student in the use of the new glider technology and join the cadre of young scientists being trained to use autonomous platforms for oceanographic research.

The initial observations at the Bermuda Atlantic Time Series (BATS) site show potential energy exceeds kinetic energy by more than an order of magnitude in the steeper portion of the spectra, implying vortex stretching dominates relative vorticity in potential vorticity fluctuations in the enstrophy cascade. Temporal variations on scales of several weeks suggest that the transition wavenumber between the two slope dependences varies as the inverse cube root of vertical wavenumber which nearly preserves enstrophy regardless of eddy energy. The goal of this project is to test if: 1) energy and enstrophy transfer portions of the wavenumber spectrum of geostrophic turbulence are a general feature of ocean eddies; 2) potential energy consistently exceeds kinetic energy in the oceanic enstrophy cascade wavenumber range; and 3) enstrophy for geostrophic eddies is self-limited to modest Rossby number. To accomplish these goals, Deepglider repeat survey missions in distinctly different eddy energy and latitude regimes in both the highly energetic Northwest Atlantic and the eddy desert of the Gulf of Alaska in the Northeast Pacific will be conducted. Missions will rely on chartered small boats or, in one case, on ancillary use of a large vessel. The approach at each site is to survey from surface to bottom a roughly 100 km by 100 km region of ocean along a common track every three weeks or so for a year. By comparing estimates from BATS and four new sites, at least a preliminary climatology of the geostrophic eddy inverse energy and forward enstrophy cascades will be created. These calculations will provide rich targets for new theories and numerical models of the ocean.