MBARI Vertical Profiler

Abstract

The Monterey Bay Aquarium Research Institute (MBARI) is a non-profit privately funded research institute devoted to the development of technology that supports ocean sciences. The MBARI Vertical Profiler (MVP) is an attempt to combine the high-resolution data of a profiler with the long-term capability of a mooring. Typical mooring instrumentation is usually located at discrete depths and subject to fouling. This can generate time-series data sets that are incomplete due to a limited number of sensors or erroneous data from fouled sensors. The number of sensors on a mooring can be increased but this increases the cost and the risk of a mooring failure. Shipboard "over-the-side" profilers (e.g. CTD), are capable of collecting a complete profile of high resolution data but the cost of staying on station for time-series measurements is prohibitive. The MVP system uses a variable buoyancy mechanism to transect the mooring line at designated time intervals. The MVP can also be parked at a depth below the euphotic zone between profiles and reduce the amount of fouling to the sensors. During 1999 and 2000, the prototype MVP was designed, manufactured, and tested at MBARI. The test configuration included the cage and flotation cones. This assembly was tested in seawater and observed to reach 90% of its expected terminal velocity. The initial sea trial testing provided critical data for the development and design of the Buoyancy Engine. The Buoyancy Engine propels the profiler through the water column by extending or retracting a piston. This piston movement changes the volume of the package and therefore the buoyancy of the profiler. The prototype was also designed for diver installation and recovery from a mooring. The MVP prototype was first tested from a ship in a series of over-the-side tests where it performed successfully to its designed depth (200 m). Next, it was deployed on a test mooring (60 m depth) for a period of 2 weeks. During these initial tests, a self-contained profiling CTD along with a miniature fluorometer were used for evaluation of the profiler performance.