Eastern Arctic ambient noise on a drifting vertical array

Abstract

Ambient noise in the eastern Arctic was studied from April to September 2013 using a 22 element vertical hydrophone array as it drifted from 89$^\circ$23'N, 64$^\circ$35'W to 83$^\circ$45'N, 4$^\circ$28'W. The hydrophones recorded for 108 min/day on six days/week with a sampling rate of 1953.125 Hz. After removal of data corrupted by non-acoustic transients, 19 days throughout the transit period were analyzed. Noise contributors identified include broadband and tonal ice noises, bowhead whale calling, seismic airgun surveys, and earthquake $T$ phases. The bowhead whale or whales detected are believed to belong to the endangered Spitsbergen population and were recorded when the array was as far north as 86$^\circ$24'N. Median power spectral estimates and empirical probability density functions (PDFs) along the array transit show a change in the ambient noise levels corresponding to seismic survey airgun occurrence and received level at low frequencies and transient ice ice noises at high frequencies. Median power for the same periods across the array show that this change is consistent in depth. The median ambient noise for May 2013 was among the lowest of the sparse reported observations in the eastern Arctic but comparable to the more numerous observations of western Arctic noise levels.