Vertical directionality and spatial coherence of the sound field in glacial bays in Hornsund Fjord.

Abstract

Arctic glacial bays are among the loudest natural environments in the ocean, owing to heavy submarine melting, calving, freshwater discharge, and ice-wave interactions. Understanding the coherence and vertical directionality of the ambient sound there can provide insights about the mechanisms behind the ice loss in these regions. It can also provide key information for operating technologies such as sonar, communication, and navigation systems. To study the unexplored sound coherence and vertical directionality in glacial bays, a vertical hydrophone array was deployed, and acoustic measurements were made at four glacier termini in Hornsund Fjord, Spitsbergen, in June and July 2019. The measurements show that the sound generated by melting glacier ice is more dominant in the upper portion of the water column near the glacier terminus. The melt water from the submarine melting and the freshwater discharge from the glacier create a glacially modified water duct near the sea surface. This disrupts the inter-sensor vertical coherence in the channel. However, some coherence across the duct is preserved for sound arising from spatially localized events at low frequencies. Overall, the observations in this study can help improve the understanding of the submarine melting phenomenon in glacial bays.