Ambient noise field and propagation in an Arctic fjord Kongsfjorden, Svalbard

Ambient noise field and propagation in a glacierized Arctic fjord, Kongsfjorden is investigated using time series measurements of noise and Conductivity Temperature Depth (CTD) measurements between July 2015-April 2016. The hydrophone recorded noise for 10 months, with a duty cycle of 1 min every 3 h, covering summer, fall, winter and spring season. Noise field is seen to be variable with highest levels recorded during summer-fall (112 dB at 0.125 kHz) after which there is a decrease in maximum recorded noise levels. The spectral distribution of noise deviates from the theoretical Gaussian assumption, at varying degrees over the frequency band (0.125-4 kHz). Low frequency band is dominated by marine traffic during summer and fall, and ice wave interactions during winter and spring months. Propagation studies reveal variable nature in propagation with different scenarios observed between seasons. During the summer, refracted paths are observed and a weak channel is formed around the sound channel axis (∼100 m), and a well defined surface duct is revealed during the fall (depth of ∼60 m), characterized by a lower half channel bounded by the sea surface and the sonic layer depth. Surface duct propagation is common in winter with an upward profile and weakens with the onset of spring, as a consequence of the hydrology at the region. The studies will be useful in the context of climate change owing to the critical location of Kongsfjorden which is more prone to experience ongoing warming.