Knorr 200‐6 will conduct a survey along the trackline shown below using SeaBeam to map seafloor topography, CTD casts to capture water samples, and the High Resolution Profiler (HRP) to measure water column properties and velocity at very small vertical scales. HRP is an untethered instrument that descends to the seafloor, drops its weights at a preprogrammed height above the bottom and ascends buoyantly to the surface. Recovery involves maneuvering the ship alongside the instrument in order to hook a line onto it, and then using a specially designed winch and lifting rig system to hoist the package back onto deck at the stern. A system of tracks is used to move the package from the stern to a protected area near the aft hangar. A typical dive takes about the same time as a shipboard CTD cast. We will conduct CTD casts simultaneously with HRP operations, but not on every HRP dive. The plan is for ~125 HRP dives and 60 CTD casts. We will also deploy 10 profiling floats along the ship's track. At 6 sites, intensive multi‐beam and HRP surveys will be carried out over a time period of ~2.5 days each. The specific goals are to be able to determine: 1) where and how much turbulent mixing occurs in the study region in relation to varying bathymetric characteristics, 2) the sources of energy driving that mixing, 3) how the dense waters navigate past a topographic ridge at 20°N, and 4) to acquire a detailed bathymetric survey and water samples along the moored array deployed last September.
The High Resolution Profiler (HRP) is a robust data acquisition system for studying mixing in the deep ocean to measure water column properties and velocity at very small vertical scales. The vehicle uses ballast weights to descend, which are jettisoned when one of the dive termination criteria is met, then excess buoyancy in the body allows rapid ascent to the surface where it is recovered. The sensor systems selected are highly accurate, and sample at precisely timed intervals. Each fulfills a task of describing a scale of ocean temperature, conductivity or velocity. Instrument configuration is flexible and extensible, so when newer and better sensors become available, they may be employed on the profiler. All the data is logged to memory during the dive and downloaded to a shipboard computer after recovery.