On the observation of internal tides at the continental slope off the coast of Norway

• Main Author: Keunecke, Karl-Heinz
• Format: Article in Journal/Newspaper
• Language: English
• Published: Bornträger 1973
• Subjects: Norway; Norwegian Sea
• Online Access: https://oceanrep.geomar.de/id/eprint/56377/; https://oceanrep.geomar.de/id/eprint/56377/1/Keunecke_K_1973_A.pdf

At first a technique is presented to evaluate repeated hydrographic sections. In order to separate the periodic variations and the fluctuations which arise as a result of the horizontal motion of the profiling ship, the data at defined locations are averaged relative to time. The procedure of averaging can be applied successfully to sets of sections repeated at a constant rate under the assumption that the spatial field is approximately stationary during the time of observation and that the energy of the overlapping temporal processes is concentrated over a few spectral bands. In these cases, the mean spatial distribution can be expected as a result. The periodic part is extracted as the deviation of the actual sections from the averaged section. This procedure was applied to a set of observations made at 28 discrete stations along a triangular course at the continental shelf off the coast of Norway during the expedition "Norwegian Sea 1969". Temperature sections were repeated six times at an interval of 18 hours. The average section shows the expected downsloping of the isotherms perpendicular to the continental shelf corresponding to the Norwegian current. lt turns out that the fluctuations with respect to time during the period of observation are probably produced by semidiurnal internal tides. Wavelength and phase velocity are estimated to be A = 22 km and c = 0.5 ms-1 respectively. The waves progress towards the shelf at right angles. For depths of 250-500 m at the continental slope a considerable amplification of wave is noticed.