Tomography buoys successfully recovered after one year in the Fram Strait
The DAMOCLES acoustic tomography moorings were successfully recovered on August 5. The objective of this first acoustic tomography experiment in the Fram Strait is to develop new ocean observing systems for the Arctic Ocean.
THE TEAM: Johan Wåhlin, Emmanuel Skarsoulis, Peter Worcester, Svein Arild Haugen, Halvor Hobæk, Hanne Sagen and the crew members of RV Håkon Mosby.
Acoustic tomography data are used to estimate the mean temperature and current fields in the deep ocean.
The data are used in combination with high resolution ice-ocean models to estimate the properties and transport of water masses in the Fram Strait. Thus, the tomography system is an important contribution to the AOOS system (Arctic Ocean Observing System) that DAMOCLES aims to develop.
The Fram Strait experiment also includes data from CTD sections (Conductivity, Temperature, Depth), Seagliders and moored profilers.
Data from this first experiment will be analysed in the coming months and the first results are expected before the end of 2009.
About the tomography technology
The tomography system measures the travel time of sound signals in different depths of the water column. Because sound travels faster in warm water than in cold water, the scientists are able to calculate the water temperature from travel time data. Also currents can be calculated when sound signals are sent in opposite directions.
The instrumentation consists of a sound source (an underwater loud speaker) and a number of receivers. The source and receivers are mounted on vertical strings anchored to the sea bed. In DAMOCLES the tomography system is deployed at about 1,500 meter depth in the deep part of the Fram Strait.
The acoustic sources and receivers will also be used for transmission of long-range acoustic navigation signals and commands in order to operate Seagliders and AUVs (Autonomous Underwater Vehicles) in ice-covered areas.
The acoustic system is designed to have negligible impact on marine mammals and other life in the ocean.
