Analysis of the variation on underwater acoustic signal across ice layer in the Arctic

Information transmission between the sea water and the air was blocked by the sea ice in the Arctic.In order to obtain the effect of ice on underwater acoustic signal transmission across ice layer,an underwater acoustic signal detected experiment was carried by using a three-dimensional geophone in the Arctic Ocean centre area.The incident angle to the ice layer is small(<10°).A physical model of ice reflection and "free" Lamb modes were used to analyze the test data,the result are presented:(1) When 20 Hz~1 kHz acoustic signal was incident into the smooth ice layer from water,the reflectivity of some frequencies would be significantly reduced,93% of the value of dips in reflectivity map would be lower than-10 dB,and some would even be lower than-20 dB.(2) The acoustic wave corresponding to the dips of ice reflectivity can be received by the geophone above the ice layer,and shows stronger vibration velocity spectrum.It is consistent with the A2 and S2 Lamb mode waves generated simultaneously in the free ice model of the station in the frequency band.These results can provide a reference for the study of underwater acoustic signal pick-up and propagation.