Nearfield measurements of ice melting noise in the central Arctic Ocean in summer

Abstract

Sea ice melting is very common in Arctic summer, so it is important to study ice melting noise. This paper analyzes a 456 min time series of under-ice noise that was recorded at a depth of 29.9 m in the central Arctic Ocean when the area was approximately 89% ice cover, UTC time, on August 8th, 2017. When the air temperature was higher than the freezing point of the surface sea water, the under-ice noise levels increased. In particular, the noise levels at 80–240 Hz and 380–660 Hz had two broad peaks and increased by 5–15 dB, furthermore, there was a large number of transient signals in the noise data. When the air temperature decreased and was less than the freezing point of the surface sea water, the under-ice noise levels gradually decreased, the broad peaks of the under-ice noise levels gradually disappeared, and the transient signals also disappeared. At the above two frequency bands, the correlation coefficients between the air temperature and under-ice noise levels were generally above 0.5 and reached a maximum value of 0.81. These results suggest that the changes in the under-ice noise levels could be attributed to sea ice melting.