Recent Advances in High-Resolution Current Profile Estimation from Autonomous Underwater Gliders

Sarah Webster1, Aleksandr Aravkin2, Jacob Stevens-Haas2, Jonathan D Jonker3, Lora Van Uffelen4, Richard A Krishfield5, Matthew A. Dzieciuch6 and Peter F. Worcester7, (1)Applied Physics Laboratory, Univ of Washington, Seattle, WA, United States, (2)University of Washington, Department of Applied Mathematics, Seattle, WA, United States, (3)University of Washington, Department of Mathematics, Seattle, WA, United States, (4)University of Rhode Island, Ocean Engineering, Narragansett, RI, United States, (5)Woods Hole Oceanographic Institution, Woods Hole, MA, United States, (6)University of California San Diego, Scripps Institution of Oceanography, La Jolla, CA, United States, (7)Univ of California San Diego, La Jolla, CA, United States
Horizontal through-the-water (TTW) progress of autonomous underwater gliders is 20-30 cm/s, which is comparable to the speed of the stronger ocean currents. Underwater localization of gliders in the presence of unknown advection therefore presents a considerable challenge. Using high frequency glider-mounted acoustic Doppler current profiler (ADCP), we are able to collect short, overlapping, glider-relative shear profiles. We will describe our recent advances in using these Doppler measurements to create a smoothed current profile estimate, while deconvolving the current profile from the glider’s true velocity over ground. The result is a complete current profile along the glider’s trajectory, as well as over-the-ground (OTG) glider velocities that can be used for more accurate subsea positioning. We will show results from the Canada Basin Acoustic Glider Experiment (CABAGE), in which two Seagliders equipped with 1 MHz ADCPs were deployed in the Canada Basin as part of a large scale acoustic tomography experiment in the summer of 2017. During this experiment the gliders recorded short overlapping shear profiles every 15 seconds with a 1MHz upward-looking ADCP, as well as transmission from the 250 Hz acoustic tomography sources. The ADCP observations, the glider’s through the water velocity estimates, and GPS fixes provide the inputs to the deconvolution. In addition, we will include subsea range measurements, derived from the acoustic tomography transmissions, to the deconvolution, and compare both results to ground truth data from the top 40 meters of the water column, collected from upward-facing 600 kHz ADCPs on the array moorings.