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Acoustic remote sensing of Arctic Sea Ice from long term soundscape measurements. (Monitoring de la glace de mer en Arctique à partir des mesures à long terme du paysage acoustique sous marin)

The Arctic sea ice melting, in the global warming context, has become a major scientific topic during the last 30 years. The Arctic Ocean plays a fundamental role in the global climate balance and requires a particular attention. The Arctic Regions are then monitored by satellite observations and in-situ measurements. The climatic impact of the total melting of the Arctic sea ice is not yet understood and researches are still needed for long term monitoring of Arctic Ocean, particularly the dynamics of the ice cover and its consequences on the ecosystems. The loss of Arctic sea ice will gradually accompanied by the installation of seasonal or perennial industrial activities. As consequences, it will result a modification in the underwater soundscapes in these regions devoid of anthropogenic sound sources. The present study, focused on the Canadian Arctic and subarctic seas natural soundscapes, falls within this context through two research axes. The first part of the present study concerns the direct consequences of the melting of sea ice on Polar Regions soundscapes. We then examined the background noise, its seasonal variations and its environmental drivers. A dedicated algorithm to estimate this ocean noise component has been developed for this purpose, in order to constitute time series from long term acoustic measurements. Through statistical analysis, we determined that the environmental variables responsible for generating the background noise depends upon the state of the ocean surface and that during the winter period, the background noise is controlled by the same environmental variables driving the large-scale Arctic Ocean circulation. The second part of our work is to evaluate the potential of passive acoustics as a complementary means of monitoring the spatial and temporal dynamics of Arctic sea ice. To do this, we identified acoustic events related to the physical phenomena under the ice cover to improve our understanding of their generating mechanisms. We were able to bind various acoustic transients to some deformation processes of the moving ice cover.