Is the ocean really getting louder?

Abstract

In 1975 Donald Ross indicated a long term trend of low frequency anthropogenic noise increase of 0.55dB/year between 1958 and 1975. This trend in ocean ambient noise levels due to expansion in global shipping has yielded an increase in the ambient noise floor of the ocean that is anywhere from 6dB to 12dB higher than what it was in 1958 (depending on location). What became known as the “Ross Prediction” did not incorporate other anthropogenic sources of noise such as navigation and communication signals, noise from offshore fossil fuel exploration and extraction, and the noises from other marine industrial enterprises. There is a concern that the increase in ambient noise is masking biologically significant sounds, although the evidence for this is still scarce and somewhat speculative. Meanwhile perhaps 90 percent of the biomass of complex vertebrates has been removed from the ocean since 1850 due to industrialized whaling and fishing operations. This paper examines whether the ocean ambient noise floor may have been significantly higher in 1800 than in the 1958 baseline year of the “Ross Prediction,” and speculates that ambient noise levels may be less of a biological aggravator than the particular characteristics of a noise source.