The onset of the COVID-19 pandemic in early 2020 brought an unexpected "anthropause". Border closures, travel restrictions, and economic slowdown meant a hiatus in commercial shipping, offshore energy exploration, and ocean tourism. It provided a rare research opportunity to investigate the time-series relationship between anthropogenic activities and ambient noise levels in oceans using Python and open data.
The ocean soundscape is noisy, merging geophony (natural noises of the earth), biophony (sounds of marine life), and anthrophony (sounds of human activities). Steep rise in trade, globalization, and opening up of new year-round shipping routes in the Arctic because of thinning of ice due to climate change means anthrophony is rising. Low-frequency sound from maritime shipping is a major source of ambient underwater noise in global oceans and a threat to marine life. To test the assumption that COVID-19 restrictions would have decreased underwater ambient noise levels in lower frequency bands (1 kHz) in early 2020, hydrophone data were collected from 8 sites in the Atlantic, Arctic, Pacific, the Mediterranean, and the North Sea. The classification of primary ambient noise sources in oceans was done using the Wenz curves. Power spectral densities were calculated before and after the lockdown, and ambient noise levels were compared at one-third octave bands centered around 63 Hz, 125 Hz, and 1 kHz. Noise contribution from ocean winds was eliminated by limiting the comparison to days with the same levels on the Beaufort scale – so that the resulting differences were likely due to the variability in the anthropogenic noise. The results have been presented as an interactive web app: www.MonitorMyOcean.com to enable policymakers to evaluate if their "Quieter Ocean" policies are working.
Speakers: Artash Nath