DURIP A Mini Trimming System and SOLO-II floats to observe three-dimensional trajectories
Abstract
Vigorous three-dimensional circulations exist in the submesoscale regime with especially strong vertical velocities. The submesoscale is defined by a Rossby number of order one, which is typically found at horizontal length scales <10 km. To quantify the three-dimensional trajectories in subsurface, submesoscale circulations we will deploy an acoustically-tracked, isopycnal-following array (IFA) of gliders and floats with other investigators in the RIOT DRI. We anticipate an array of a few kilometers in extent, which drifts for about a week, but emphasize that how the IFA disperses is actually a research question.Observing these three-dimensional trajectories depends on solving two technical problems: (a) designing a neutrally buoyant platform that can follow a parcel of seawater and (b) acoustic tracking of the IFA in the horizontal. To obtain neutral buoyancy, we will add a mini trimming system (MTS) to buoyancy-driven profilers, which permits fine control of volume via a single stroke pump. The MTS will have a total displacement of about 100 mL. We will make this solution available to other RIOT projects. To obtain horizontal localization, acoustic options are available: (i) simple long baseline transponders/interrogators to obtain slant ranges and (ii) the WHOI MicroModem which adds two-way communications for issuing commands and transferring data. Vertical location is easily determined with pressure.This DURIP project supports (a) the design and fabrication of 10 MTS and (b) the fabrication of 5 SOLO-II profiling floats equipped with acoustic communications. The additional MTS are for 5 existing Spray 2 underwater gliders.Since all assets are equipped with the same acoustic tracking hardware and MTS, their roles are interchangeable. Some assets will profile, while other assets form the IFA. The profiling assetsobtain accurate positions at surface intervals, which are used to reference the relative positions from acoustic tracking. Depending on the acoustic range and location of the IFA, the number of profiling assets can be adjusted to either join the IFA or obtain sections to characterize the environment at scales larger than the IFA.This autonomous fleet may be deployed anywhere during the RIOT DRI. We prefer targeting strong submesoscale features that are predictable and locked to topography, such as island wake eddies. Thisnew technology will be used first in the Channel Islands in the Southern California Bight, where wake eddies with Rossby numbers ~ 1 and scales < 10 km are known. The easy logistics and proximity to our labs allow RIOT the best chance to deal with inevitable problems that arise with the new technology of the IFA. There is the opportunity to study both cyclonic and anticyclonic wakes in close proximity. This first study will be funded under the RIOT DRI.Our technical achievement will be an adaptable, autonomous fleet of floats and gliders for direct measurement of three-dimensional submesocale trajectories. The scientific outcome is an unprecedented resolution of subsurface, submesocale trajectories.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 13, 2025
- Source ID
- N000142512136
Entities
People
- T.m. Shaun Johnston
Organizations
- Office of Naval Research
- United States Navy
- University of California, San Diego