Measuring a Lagrangian drifter’s slip with an onboard ADCP

A perfect Lagrangian drifter should move with the same velocity as the water volume that it is following. Deviations from this ideal will result in a relative velocity between the drifter’s drogue and its surrounding water, commonly named “slip”. Estimating a drifter’s slip is difficult, especially for custom and heavily instrumented drifters. We propose to use a Self-Contained Acoustic Doppler Current Profiler (SCADCP) attached to the drifter to: • Measure the drifter’s slip directly at the drogue depth. • Obtain complementary data of current at other depths.