Surface drifters have been used for a long time to gather information about ocean motion. Since the drifters of the early days, a significant evolution has brought us to today's high accuracy GPS-positioned, multi-sensor, real-time tracked drifters.
The modern age of surface drifters began in the early 1980's with the development of the Davis drifter, designed to measure currents in the upper metre of the ocean. Robust enough to measure currents in the open sea and estuarine waters, the Davis drifter consisted of a 90 cm cylindrical hull, 10-15 cm in diameter, containing batteries and electronics. The drifter's floatation was ensured by four small floats connected to the end of the arms to which the underwater “sails” were attached.
The Coastal Ocean Dynamics Experiment (CODE) adopted the Davis drifter, and the Lagrangian Drifter Laboratory (LDL) at Scripps developed a buoy controller that enabled it to carry different sensor payloads. The CODE/Davis drifter’s design virtually eliminated the effect of direct wind forcing and substantially minimized Stokes drift. Although bulky and not easy to handle, it is, nevertheless, still under commercialization and widely used.
Different float designs were tested during the 1980’s to satisfy the requests of the World Ocean Circulation Experiment (WOCE). These resulted in the Surface Velocity Program (SVP) drifter configuration adopted by the NOAA's Global Drifter Program: a holey sock drogue centred at 15 m below the surface, suspended from a spherical float with nearly equatorial buoyancy. This arrangement practically eliminated Stokes drift and showed acceptably low downwind slip. If the drogue was lost, however, the slip increased more than one order of magnitude. Adopted by the Global Ocean Observing System (GOOS), LDL developed the lower-cost mini-SVP (35cm sphere) drifter to satisfy GOOS’s goal of covering the ocean surface with 1,250 measurement devices.
Based on the concept of the mini-SVP drifter, LDL has been supporting the production of several lines of surface drifters, including an undrogued one capable of delivering directional wave spectra and another provided with wind and wind atmospheric pressure sensors. LDL remains a world reference in surface drifters' production. Nevertheless, the mini-SVP drifters are neither cheap nor easy to store, transport and deploy. A simpler and cheaper drifter might help achieve GOOS' goal, thereby contributing to improve the knowledge of ocean dynamics and the quality of ocean and weather forecasts.
To our knowledge, the WAVY drifter is one of the very few drifters to have been designed specifically to carry out measurements in the nearshore and surf zones.
The MELOA team is currently deploying the WAVY drifters to validate and implement use cases! If you have a potential application for the WAVY Littoral that you would like to try out, please get in touch!