Abstract
Over a 4-year period between 2015 and 2019, in-situ time series measurements of ocean ambient noise over the frequency range 100 Hz to 10 kHz, by an autonomous passive acoustic monitoring system have been made in the Kongsfjorden, Svalbard, Arctic. We characterize the noise due to sea ice melting during winter (December–January). This unique observation reveals loud noise signatures, of the order of 8 dB higher than the background noise, showing the signature of sea ice melting. Such observations are crucial for monitoring sea ice melting, especially during winter, to understand the recent warming of Arctic waters. The anomalous air temperature due to local atmospheric forcing and warming of ocean temperature in the fjord through ocean tunneling, individually or combinedly, is responsible for such sea ice melting. The cyclonic events in the Arctic are responsible for the anomalous atmospheric and ocean conditions, causing sea ice melting in winter.
Highlights
The audio files relating to sea ice melting show a loud and impulsive popping noise by breaking of tiny air bubbles entrapped in the ice (Supplementary Audio S1)
The sounds produced by the sea ice melting with spectral peak in the range of 1–3 kHz is similar to the sounds recorded in the summer glacierized fjord at Icy Bay, Alaska and laboratory experiments[31,32,33]
Our study shows that the maximum spectral content lies between 1 and 3 kHz, and the noise spectrum level extending to higher frequencies, are mainly due to the breaking of multiple air bubbles in varying sizes during the sea ice melting
Summary
In 2017–18, two cyclone events were observed on 20th December 2017 and 14th January 2018 (Fig. 2c), that stirred and advected the shelf warm seawater into the Kongsfjorden through surface turbulent process and resulted in sea ice melting. In 2018–19, a single low pressure of 980 hPa was observed on 12th January 2019 (Fig. 2d), and no sea ice melting sounds have been recorded in association with the extreme event.
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