Shallow water profiling platforms — SeaTramp and Octopus

Two profiling concepts will be presented and compared: The commercially available buoyancy engine profiling system SeaTramp from Ocean Origo AB, Sweden with focus on the latest achievements and data sets and a prototype underwater winch system of the University of Bremen. SeaTramp is an autonomous, multicycling, data collecting titanium platform designed for long term unattended marine monitoring and research. It profiles along a guiding wire using a closed oil pump buoyancy control system for propulsion and performs well also in stratified waters and when equipped with bulky, non stream-line payload. SeaTramp may be set to operate in “profiling mode” as well as “brake mode” where the platform stops and measures only at discrete depths selected by the operator. A data set from Gullmar fjord in Sweden, where SeaTramp is equipped with a NAS-2E nitrate analyser, SeaBird CTD, oxygen, chlorophyll, tilt, transmittance and PAR (light) sensors is presented as an example on how to achieve high resolution depth profiles with only one single set of user selectable sensors. Underwater winch systems may under certain conditions be advantageous to use. The prototype system Octopus of the University of Bremen is especially designed for small payloads and allows for real-time accessibility of moored sensors. Tests of the system have been conducted in the Gullmar fjord in Sweden which showed promising results. The aim of the presentation is to describe the state of the art of shallow water profiling systems and give clues to future developments and use under different deployment conditions particularly in the Baltic Sea.