Ocean Soundscapes in Antarctica's Amundsen Sea: Insights from Long-Term Hydroacoustic Monitoring

Deploying long-term, passive acoustic sensors in the polar ocean allows us to record a wide variety of sounds related to air-sea interactions, including icequakes from sea-ice, icebergs, and ice shelves, as well as vocalizations of marine mammals and ocean noise from human activities. The combination of these sounds in a specific location and time period is often referred to as the “soundscape,” and the characteristics of these sounds serve as a tool to monitor changes in the local ocean environment.

The Korea Polar Research Institute and NOAA/Pacific Marine Environmental Laboratory have jointly operated two Autonomous Underwater Hydrophones in Pine Island Bay and the Dotson Ice Shelf region in the Amundsen Sea during the periods of February 2020 to August 2022 and February 2022 to January 2024, respectively. The broadband cryogenic signals recorded at these sites exhibit correlations with local wind speeds and tidal forces. In the Pine Island Bay data, we detected signals from a large iceberg (B-49) that calved from the Pine Island Glacier ice shelf in February 2020, and noise levels steadily declined after 2020, coinciding with changes in sea ice concentration and the movement of icebergs and the ice shelf.

Seasonal variations in icequake activity were particularly prominent in the Dotson Ice Shelf region, with the highest noise levels occurring during the austral summer when nearby sea ice concentration approached zero. These signals were likely caused by iceberg movements in the nearby Bear Ridge region. Leopard seal vocalizations were successfully detected exclusively in the Dotson Ice Shelf region, whereas whale calls, commonly recorded in other Antarctic regions, were absent in both regions. Despite the logistical challenges and harsh environmental conditions associated with long-term hydroacoustic monitoring in polar regions, the data can help us understand environmental changes in the Southern Ocean and provide information about the status and trends of biodiversity.