Seismic soundscape of the Arctic Ocean: seasonal effects of sea ice and swell on deep-sea ocean bottom seismometer records

SUMMARY The global oceans are a noisy environment with characteristic acoustic and seismic soundscapes. The enclosed, sea ice-covered Arctic Ocean constitutes a particular noise environment that is rapidly changing. Here, we present a first, comprehensive description of the seismic soundscape of the Arctic Ocean recorded by ocean bottom seismometers especially equipped for the operation in sea ice. They were deployed at 4 km water depth in the Laptev Sea near the sea ice edge in September 2018 and recovered one year later. Analysis of the spectral power between 20 s and 60 Hz demonstrates that ambient noise levels are generally very low compared to other ocean bottom seismic records. Distinct noise bands at high frequencies (>6 Hz) characterize the winter time and are likely caused by the deformation of sea ice emitting seismic signals recordable at the ocean bottom over tens of kilometers. Sea ice noise decays suddenly in May while sea ice concentration is still 100 per cent, but freezing stops and compressional stresses decrease. It only gradually develops in autumn as sea ice becomes thicker, brittle and internally stressed. Microseisms with frequencies of 0.2–2 Hz appear with open water on the Laptev Shelf. Swell events in autumn cause large microseisms and high-frequency noise although ice-noise is not yet present in this season. Ice concentration decreases following the swell events, showing the impact of swell on the sea ice. Ocean bottom seismic records thus represent a powerful tool to monitor the interplay between wave action in the emerging Arctic Ocean and the physical state of its sea ice cover.