Statistical characteristics of under-ice noise on the Arctic Chukchi Plateau.

In the context of global warming leading to rapidly changing Arctic sea ice and the environment, it is necessary to understand the statistical characteristics of noise under existing Arctic ocean environmental conditions. The data recorded from August 1, 2018 to November 2, 2019, on the Arctic Chukchi Plateau, have been studied to analyze the relationship between the ice transient events and the non-Gaussian statistics of under-ice noise. The ice-generated transient noise largely contributes to the under-ice noise environment, and the total under-ice noise exhibits non-Gaussian statistics due to the occurrence of these ice transients. The number of ice transients has a strong negative correlation with the characteristic index α, meaning that the higher the occurrence of transient events, the stronger the non-Gaussian statistics of under-ice noise. Stronger non-Gaussian noise with full ice coverage is observed compared to partial ice coverage. The under-ice noise in 0.5-1 kHz exhibits the strongest non-Gaussian statistics, followed by 1-4 kHz, while it is weakest in 20-500 Hz. The statistics of ice transients and under-ice noise have been provided in this paper, which can be used in sonar detection algorithms and have important significance for the performance prediction and optimization of sonar processors.

Ocean ambient noise on the Chukchi Plateau and its environmental correlates.

Conducting research on ocean ambient noise under different sea ice conditions is highly important for the comprehension of the rapidly changing Arctic. We present the first results of ambient noise and its relationship to environmental forcing during the open-water, ice transition and ice-covered periods on the Chukchi Plateau. The ambient noise level (ANL) in the 20 Hz to 2 kHz band is higher, intermediate and lower during the open-water, ice transition and ice-covered periods, respectively. During the ice-covered period, the ambient noise is dominated by the ice-generated noise due to sea ice activities and shows a negative correlation with temperature. Therefore, when the temperature decreases, the sea ice is prone to shrinking and cracking, thus increasing the sea ice activities and resulting in increased ice-generated noise; when the temperature rises and is relatively high in May and June, the ANL is lowest for the sea ice inhibition to wind waves and decreased sea ice activities induced by temperature rise. Sea ice is the most predominant environmental factor affecting Arctic ocean ambient noise, and the ANL can potentially increase due to a reduction in Arctic sea ice and increase in human activities caused by global climate change.