Spectrograms of acoustic power spectral at the Bransfield Strait (A) and Scotia Sea (B).

<p>Spectrograms are calculated from 2 second FFT windows with each vertical time slice representing the cumulative energy over a 1 day interval. Near-constant, broad-band, short-duration impulsive signals are likely sounds from wind-driven waves and ice breakup. Clustered energy in the 15–25 and 89 Hz bands are fin whale calls. Blue whale calls are the steady tone at 27 Hz. The several examples of fundamental and overtone energy <10 Hz in both spectra are interpreted to be from a combination of sources, including broadband energy created by sea-state (storms, waves, and wind), iceberg grounding tremor, and tonal “strumming” of mooring line caused by fast moving ocean currents. White areas represent times with no data.