Instrument: Tracer Injection Sled

The tracer injection sled is an integrated instrument package that is deployed from a vessel and lowered to the target potential density surface and then towed along that surface at 0.5 m/s while the tracer is injected. The sled is neutrally buoyant and is towed at the end of a 2-meter tether attached to the end of the CTD cable, which removes much of the ship motion. To follow lower frequency displacements of the target surface, the winch is controlled automatically with feedback from a SeaBird 911plus CTD system (Ledwell et al., 1998).The CTD has dual pumped C/T sensors mounted at the front of the sled to sample water not perturbed by the thermal wake of the sled. A WET Labs fluorometer is also present along with mounted injection orifices, pumps, batteries, fluid reservoirs, and control electronics for the injection.