Development of a System for Long Term Underwater Sensing

University essay from KTH/Marina system

Author: Jari Krützfeldt; [2015]

Keywords: ;

Abstract:

The monitoring of the worlds oceans is a fundamental requirement to understand and predict the ongoing climate change. Scientists need reliable long-term data series from regions that are of great interest for understanding the climate change and its consequences. An important area is the West Antarctic Ice Shelf (WAIS), which is still a great uncertainty of future sea level rise predictions. The vulnerable polar regions are, however, seldom sampled, mainly because of their remoteness, the cost and the possibility to reach them.The KTH Center of Naval Architecture recently formed a cooperation with the Department of Earth Science (GVC) at the University of Gothenburg to develop a cost effective sens-ing system, designed to acquire long term temperature data in remote polar regions. The oceanographers at GVC are researching if the sea bottom temperature in shelf regions like the WAIS can be used as a proxy for the whole oceanic heat content. This research makes it possible to use sensing systems that are moored close to the sea-floor and measure ocean bottom temperature only.In this thesis a low-cost system for long term underwater sensing (LoTUS) is developed. The LoTUS bottom lander system consists of a positive buoyant pressure hull equipped with a very precise temperature sensor, an Iridium satellite link, GPS and a deep hibernation functional-ity. The bottom landers are deployed from a ship or a helicopter and sample data for up to 10 years in water depths up to 1000 meter. As soon as the intended operation time is reached, the LoTUS lander releases its anchor, surfaces and transmits its temperature data to the user ashore via satellite. Afterwards the bottom lander reconfigures to a GPS beacon mode, i.e. it drifts and regularly sends out its position to observe direction and velocity of surface currents. The LoTUS system was successfully tested in the Baltic Sea and in the Petermann 2015 Ex-pedition in northern Greenland. The bottom landers proved to be working under harsh polar conditions and can be used as a new and innovative low cost sensing system to acquire long term temperature data.

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