We present results from an experiment designed to better understand the mechanism by which ocean currents and winds control flotsam drift. The experiment consisted of deploying in the Florida Current and subsequent satellite tracking of specially designed drifting buoys of various sizes, buoyancies, and shapes. We explain the differences in the trajectories described by the special drifters as a result of their inertia, primarily buoyancy, which constrains the ability of the drifters to adapt their velocities to instantaneous changes in the ocean current and wind that define the carrying flow field. Our explanation of the observed behavior follows from the application of a recently proposed Maxey–Riley theory for the motion of finite-sized particles floating on the ocean surface. The nature of the carrying flow and the domain of validity of the theory are clarified, and a closure proposal is made to fully determine its parameters in terms of the carrying fluid system properties and inertial particle characteristics.
On the sphere, with local coordinates x1 = (λ − λ0) · a⊙ cos ϑ0 and x2 = (ϑ − ϑ0)·a⊙, where a⊙ is the planet’s mean radius and λ (respectively, ϑ) is longitude (respectively, latitude), the Maxey–Riley set takes the form (5) with f = 2Ω sin ϑ + τ⊙1, where Ω is the planet’s rotation rate and , , where γ⊙ ≔ sec ϑ⊙ cos ϑ and . In turn, the reduced Maxey–Riley set takes the form (12) with , with γ⊙, f, and ω as above.