Oseanografiske variasjoner i testområde for KNM Fridtjof Nansens akseptansetester, mars 2007

The Norwegian Defense is procuring five new frigates with an advanced sonar system. The frigates are equipped with a hull mounted sonar and a towed array. In connection with the procurement a Sea Acceptance Test 2 (SAT2) will take place. The test area is located in the North Sea west of Bergen, and is chosen because of the topography in that area. During SAT2 it is important to know the different environmental parameters, such as sound speed. The sound speed should vary as little as possible in time and space when the tests are in progress. Therefore it is necessary to measure the sound speed in the test area previous to and during SAT2. A survey was carried out in the test area outside Bergen 2-4 March 2007. SAT2 was going to take place the following days, but the tests where postponed. The aim of the survey was to map the oceanography in the area and based on that information give advice were the tests should take place and what kind oceanographic variations could be expected. We observed that the oceanographic variations are considerable and it changes relatively rapidly, and it could be a challenge to locate stable oceanographic areas. The measuring methods made us cover a large area in a relatively short time period, but at the same time keep a high data resolution. We also had a quick look on how such variations affect the transmission of sound by using Lybin.