Lateral stirring is a basic oceanographic phenomenon affecting the distribution of physical, chemical, and biological fields. Eddy stirring at scales on the order of 100 km (the mesoscale) is fairly well understood and explicitly represented in modern eddy-resolving numerical models of global ocean circulation. The same cannot be said for smaller-scale stirring processes. Here, the authors describe a major oceanographic field experiment aimed at observing and understanding the processes responsible for stirring at scales of 0.1–10 km. Stirring processes of varying intensity were studied in the Sargasso Sea eddy field approximately 250 km southeast of Cape Hatteras. Lateral variability of water-mass properties, the distribution of microscale turbulence, and the evolution of several patches of inert dye were studied with an array of shipboard, autonomous, and airborne instruments. Observations were made at two sites, characterized by weak and moderate background mesoscale straining, to contrast diff...

/pdf/the-latmix-summer-campaign-submesoscale-stirring-in-the-5cs1qch6wi.pdf

The latmix summer campaign: Submesoscale stirring in the upper ocean

........................................................................................... 86 KOKKUVÕTE ....................................................................................... 88 APPENDIX A ......................................................................................... 91 APPENDIX B ....................................................................................... 101 APPENDIX C ....................................................................................... 109 APPENDIX D ....................................................................................... 123 APPENDIX E ....................................................................................... 131 APPENDIX F ....................................................................................... 145 APPENDIX G ....................................................................................... 153 APPENDIX H ....................................................................................... 175 CURRICULUM VITAE ..................................................................... 183 ELULOOKIRJELDUS ....................................................................... 184

Flow-Sensitive Robotic Fish: From Concept to Experiments. Voolutundlik robotkala: ideest katsetusteni

Observations of hypoxia, dissolved oxygen (DO) concentrations < 1.4 ml L−1, off the central Oregon coast vary in duration and spatial extent throughout each upwelling season. Underwater glider measurements along the Newport hydrographic line (NH-Line) reveal cross-shelf DO gradients at a horizontal resolution nearly 30 times greater than previous ship-based station sampling. Two prevalent hypoxic locations are identified along the NH-Line, as is a midshelf region with less severe hypoxia north of Stonewall Bank. Intraseasonal cross-shelf variability is investigated with 10 sequential glider lines and a midshelf mooring time series during the 2011 upwelling season. The cross-sectional area of hypoxia observed in the glider lines ranges from 0 to 1.41 km2. The vertical extent of hypoxia in the water column agrees well with the bottom mixed layer height. Midshelf mooring water velocities show that cross-shelf advection cannot account for the increase in outer-shelf hypoxia observed in the glider sequ...

Intraseasonal Cross-Shelf Variability of Hypoxia along the Newport, Oregon, Hydrographic Line

Underwater autonomous gliders (UAG) such as Slocum electric gliders provide an effective platform and tool for marine and coastal scientists to conduct prolonged missions over weeks or months. However, localization of these gliders underneath ocean surface is challenging due to the lack of inexpensive, effective underwater positioning sensors. In this paper, we present a dynamic model-based localization scheme to improve the positioning estimation of UAG. The new localization approach is built on an experimentally validated dynamic model and fused with onboard depth and yaw angle sensor measurements. We compare and validate the proposed scheme with dead reckoning and the ground truth.

Dynamic model-aided localization of underwater autonomous gliders

This work indicates two novel ocean current observation methods that based on a glider type mobile platform. Glider with current meters are ideal current observation solutions for marine scientists since they have merits of large dynamic area and low power consumption, but their measurement accuracy is insufficient now. The proposed 1st solution, single point current meter compensated inversion method (SPCMCIM), is a revolution of the conventional inverse method by solving the acoustic Doppler to current profiler (AD2CP) induced turbulence problem. It’s a cooperated AD2CP and single point current meter (SPCM) algorithm that compensates the contaminated first AD2CP layer data. The physical position of the SPCM is also optimized according to a finite element analysis (FEA) study to minimize the interference generated by the SPCM. The 2nd method is solving the area restriction problems that AD2CP can just apply to non-pure water environment namely single point and inertial measurement inversion method (SPIMIM). It utilizes the SPCM as the only current observation source and takes advantages of physical properties of ocean currents. The currents are constitute of stable layers and each of them has a stable velocity, so the glider’s velocity variation can be obtained by reading the SPCM. The velocity variation in the transition process between layers can be acquired by the low cost inertial sensors. Finally, these theoretical studies were verified in an onsite sea trial. The SPCM and AD2CP was mounted to an underwater glider to measure the currents and a ship equipped AD2CP was used to provide the arbitrary data. Both of the proposed method can effectively measure the current velocity and induced significant enhancement than the classical inversion method. In particular, the first method conducted improvement of 70% accuracy by average. The 2nd one also shows an obvious improvement and has the advantage to deploy to high purity water area like deep lakes or north pole.

Novel Underwater Glider-Based Absolute Oceanic Current Observation Solutions

ADCP sensors have recently been incorporated into AUV Gliders offering the potential for increased physical and biological oceanographic observations. These vehicles can collect high-density measurements for weeks at a time at a small cost compared to vessel-reliant operations. Glider-based ADCPs can provide absolute water velocity profiles based on the “shear method” developed from LADCP research and offer the ability to perform oceanographic research where stationary platform and vessel-based ADCP observations are unavailable or not suitable. The ability to obtain accurate velocity profiles from gliders will further enable high resolution and cost-effective oceanographic observations. Shear is calculated from water track velocities measurements for every ensemble and averaged within depth intervals to create one shear profile for each glider dive. The vertically averaged shear profile is integrated to establish a velocity profile relative to the bottom of the glider dive. As shear is independent of platform motion, integrated relative velocities will not contain glider motion bias. Absolute velocities are computed by referencing dive-averaged velocity measurements, based on the glider drift. Bottom track velocities, where available, they be referenced to water track measurements and provide absolute velocities. Bottom referenced velocities provide a verification for dive-averaged velocities and are valuable for removing diverging velocity offsets. Effective data processing methods, data filtering, accurate heading information, and instrument settings for high-quality data collection are the tools for obtaining absolute water velocity profiles from gliders. The Oregon State University Glider Research Group is refining these methods by comparing results against concurrent velocity measurements from adjacent ADCP platforms. The findings described in this document result from experiments performed in 2011 by OSU off the Oregon Shelf and during the Office of Naval Research sponsored Lateral Mixing Project in the Sargasso Sea.

Obtaining absolute water velocity profiles from glider-mounted Acoustic Doppler Current Profilers

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Obtaining absolute water velocity profiles from glider-mounted Acoustic Doppler Current Profilers